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| LIMBAL PALISADES OF VOGT*
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|
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| BY Morton F. Goldberg, MD, AND
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|
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| (BY INVITATION) Anthony ]. Bron, BSC
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|
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| INTRODUCTION
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|
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| THE PALISADES OF VOGT WERE CLINICALLY DESCRIBED IN 1914 BY STREIFF WHO
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| called them “radial stripes”; in 1917 by Koeppe who called them “radial
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| pseudocysts”; and in 1934 by Graves who called them “trabeculae.”1 At
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| one time they were thought to have a glandular function but this notion was
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| clearly dispelled by Aurell and Kornerup in 1949.2 Because the name
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| applied in 1921 by Vogt has persisted, we will maintain his terminology. 13*‘
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|
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| The palisades of Vogt are a series of radially oriented fibrovascular ridges
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| that are concentrated along the upper and lower corneoscleral limbus.
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| There, they aggregate into distinct crescentic zones. They lie just peripheral to the terminal capillary loops of the limbus and just central to
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| Schlemm’s canal. Between the connective tissue palisades are intervening
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| radial zones of thickened conjunctival epithelium, the so-called interpalisades or epithelial rete ridges. '
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|
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| The palisade and interpalisade regions thus contain specialized blood
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| vessels and may also serve as repositories of epithelial cells. They may have
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| clinical importance in replacing defective corneal epithelium (as for example in normal aging, recurrent corneal erosion, chemical burns, melting
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| diseases, and delayed graft epithelialization).5'6 The morphology of the
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| palisades and interpalisades may also explain the characteristic pattern of
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| pigment slide and of cornea verticillata, as seen in Fabry’s disease and in
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| drug-induced degeneration of the corneal epithelium (eg, chloroquine,
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| amiodarone, and others).7
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|
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| *From the N ufiield Laboratory of Ophthalmology, University of Oxford, England, and from
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| the University of Illinois Eye and Ear Infirmary, Chicago, Ill. Supported in part by a Macy
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| Foundation Faculty Scholar Award (Dr Goldberg), by core grant EY1792 from the National
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|
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| Eye Institute, Bethesda, Maryland, and by an unrestricted research grant from Research to
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| Prevent Blindness, Inc, New York, NY.
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|
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| Tn. AM. OPHTH. Soc. vol. LXXX, 1982
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| 156 Goldberg
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|
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| Because little is known of the morphology of this region and because
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| angiographic studies have not previously been undertaken we present the
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| results of our biomicroscopic and angiographic investigations in both
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| normal and abnormal human limbuses.
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|
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| SUBJECTS AND METHODS
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|
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| Over 40 normal adults and several additional patients with infectious
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| conjunctivitis were examined biomicroscopically. Macrophotographs were
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| obtained in 30 normal subjects (X 10 magnification on film) using the
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| Brown macrocamera and the Nikon specular camera with Ektachrome 200
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| film. Linear measurements of the palisades and interpalisades were obtained by superimposing an enlarged photographic negative of a stage
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| micrometer onto photographic prints of the palisade region that were
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| enlarged identically. The micrometer (obtained from Graticules, Ltd,
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| Tonbridge, Kent) was graduated in 0.01 mm steps.
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|
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| p F luorescein angiography was performed with the Zeiss photo slit-lamp
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| and the Zeiss 75 SL at X 16 magnification. Subjects were injected antecubitally with 5 mL of 20% sodium fluorescein, and a flash frequency at
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| 0.5- to 1.0-second intervals and maximum power were employed.
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|
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| For histologic study, the eye of an 84-year-old white woman was obtained at autopsy. The limbal tissues were fixed in formalin and stained
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| routinely with hematoxylin and eosin. Photographs were taken with a Zeiss
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| photomicroscope.
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|
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| RESULTS
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|
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| CLINICAL MORPHOLOGY
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|
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| Precise focusing of the slit-lamp (Fig IA and B) and high magnification (Fig
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| 1C) are necessary if the palisades are to be observed. They are found just
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| peripheral to the terminal capillary loops of the limbus (Fig 2). The
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| appearance of the palisade zone varies considerably from one individual to
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| the next. For example it is altered by the presence of melanin (Fig 3A and
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| B). In moderately or darkly pigmented individuals the palisades are easily
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| seen in diffuse illumination, because they are outlined by the melanincontaining epithelial cells of the interpalisades (epithelial rete ridges).
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| Vessels in these palisades may be obscured by dispersed pigmentation. In
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| lightly pigmented whites the palisades may be difiicult to see in diffuse
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| illumination, but can be observed rather well by scleral scatter. In some
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| individuals the palisades are not visualized well at all. In many instances,
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| Palisades of Vogt 157
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| 158 Goldberg
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|
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| FIGURE 2
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| Palisades of Vogt are located just peripheral to terminal capillary loops (arrows) of limbus.
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|
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| especially in lightly pigmented individuals, the characteristic blunt-tipped
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| vascular loops in the fibrovascular palisades mark their location (Fig 1A).
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| These vessels are more prominent when the eye is inflamed (Fig 4).
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|
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| The palisades are most numerous and obvious along the superior and
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| inferior limbal regions, and least prevalent in the horizontal meridians.
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| They may be few in number or may exceed
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|
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| The configuration of the palisade zone is highly variable, and no limbal
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| region is identical to any other, even in the same patient. The palisades
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| appear to be more discrete in younger individuals and to be more prominent and regular along the lower limbus than at the upper limbus (Fig 5A
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| and B). The overall configuration in one eye tends to resemble that in the
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| other eye, but the symmetry is never exact.
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|
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|
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|
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| FIGURE 1
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| Precise focusing at high magnification is necessary if palisades of Vogt are to be observed. A:
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| Each palisade (arrows) contains a radially oriented vascular complex; cf, Fig 1B. Open arrow
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| indicates marker vessel for orientation and comparison with Fig 1B. The angiogram is shown
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| in Fig 7. 8; Same area as Fig 1A, but focused slightly more superficially. The palisades
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| cannot be seen. Open arrow indicates marker vessel for orientation and comparison with Fig
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| 1A. C: Limbal area at low magnification only faintly shows palisade zone as series of short,
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| radially oriented and parallel stripes (arrow).
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| Palisades of Vogt 159
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|
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| 9
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|
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| FIGURE 3
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| The palisades of Vogt are more easily discerned when moderately dense limbal melanosis is
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| present. A: East Indian limbus; palisades outlined by melanin-containing cells ofinterpalisade
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| zones are easily seen in diffuse illumination. B: European limbus; palisades are seen well only
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| in scleral scatter.
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|
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| FIGURE 4
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| Vessels (arrows) of the palisades are dilated and more visible when the conjunctiva is
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| inflamed, as in case of adenoviral conjunctivitis.
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| 160 Goldberg
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|
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| FIGURE 5
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| Palisades are more prominent and regular along lower limbus than at upper limbus. A:
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| Composite photograph of lower limbus of eye whose upper limbus is shown in Fig 5B. B:
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| Composite photograph of upper limbus of eye whose lower limbus is shown in Fig 5A.
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|
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| In non- or lightly pigmented eyes, the palisades appear white and
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| translucent. Their edges are highlighted, possibly due to the contrast
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| imparted by adjacent ridges of epithelial cells in the interpalisades. Thus
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| each palisade may appear double—contoured. In more heavily pigmented
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| eyes the palisades are easily identified because of rows of brown pigment,
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| presumably due to adjacent epithelial cells containing melanin that are
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| seen end on.
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|
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| The shape of individual palisades is also extremely varied. The commonest configuration is a long, narrow rectangle, but tiny circles or ovals
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| may also be seen. The latter shapes are probably identical to the "basal
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| crypts” of Graves,8 and often contain a central red dot, presumably a
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| Palisades of Vogt 161
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|
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|
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|
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| FIGURE 6
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| The shape of individual palisades varies considerably. A: Typical narrow rectangles are seen at
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| right, and more unusual dot and oval shapes are seen at left. B: Palisades shaped like H’s, V's,
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| K’s, or Y's may be seen, along with complex trabecular configurations.
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|
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| palisadal vessel seen end on. The long, narrow, rectangular palisades often
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| interconnect, forming Y-, H-, X-, or K-shaped patterns (Figs 5, 6). Sometimes, more extensive connections give a trabecular appearance.
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|
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| Measurements of the length and width of the palisades and interpalisades from 12 normal subjects are shown in the Table, and indicate that
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| the fibrovascular bundles are narrower than the epithelial rete ridges. The
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| average length of the palisades in our subjects was 0.36 mm : 0.09 SD
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| (range: 0.25 to 0.59 mm), and their average width was 0.04 mm : 0.007 SD
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| (range: 0.03 to 0.05 mm). The variation of these dimensions is indicated by
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| the coeflicients of variation, which were 26.7% for length and 18.5% for
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| width. The corresponding measurement for the width of the epithelial
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| interpalisades was as follows: average width, 0.07 mm : 0.02 SD (range:
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| 0.05 to 0.10 mm). The coefficient of variation was 22.7%. The length of the
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| interpalisades could not be determined because of the lack of discrete
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| margins.
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|
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|
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|
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| TABLE: PALISADE MEASUREMENTS (n = 12 NORMAL SUBJECTS)
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|
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| LENGTH WIDTH INTERPALISADAL WIDTH
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|
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| Mean 0.036-mm 0.04 mm 0.07 mm
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| Range 0.25-0.59 mm 0.03-0.05 mm 0.05-0.10 mm
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| SD 0.09 mm 0.007 mm 0.02 mm
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| Coeflicient of
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|
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| variation 26. 7% 18. 5% 22. 7%
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| cf, Duke-Elder &
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|
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| Wybar26 — — 1.5-2.0 mm
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|
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| Vogta 0.07-0.9 mm 0.03-0.05 mm 0.1-0.15 mm
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|
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| Cravess 0. 5-1.25 mm — —-—
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| 162 Goldberg
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|
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| AN GIOGRAPHIC FINDINGS
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|
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| The small size, rapid filling, and complexity of the limbal vasculature make
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| angiographic interpretation somewhat difficult. The palisadal vessels,
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| however, because of their parallel, radial orientation can be distinguished,
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| and the extent of their ability to contain fluorescein intraluminally can be
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| characterized. The palisadal vessels are but one microvascular subsystem
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| derived from the anterior ciliary arteries.
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|
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| As described in detail by Bron and Easty,9 the sequence of How in the
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| external portion of the globe’s anterior segment is as follows: (1) The
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| anterior ciliary arteries fill first, and give rise to episcleral branches
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| directed anteriorly toward the limbus. (2) Three distinct vascular subsystems then fill, as follows, and ultimately drain into the episcleral venous
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| plexus: .
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|
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| a. The recurrent conjunctival arteries, supplying the paralimbal con
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| junctiva for a distance of about 3 to 6 mm from the limbus;
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|
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| b. the marginal arcades (terminal capillary loops) of the cornea (the most
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|
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| centrally located vessels); and
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|
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| c. the palisadal vessels.
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|
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| The palisadal vessels fill extremely quickly, and, with the techniques
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| employed, the arterial and venous components of the hairpin vascular loop
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| occupying the palisade cannot be distinguished. The functional competence of their endothelial linings appears more developed than that of
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| other episcleral and conjunctival vessels, in that leakage of fluorescein
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| occurs later than it does in these other vessels and apparently to a lesser
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| extent (Fig 7A and B). The onset and amount of leakage roughly parallel the
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| courselof events in the marginal arcades (Fig 7).
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|
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| As leakage from the normal palisadal vessels proceeds, the palisades
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| gradually become hyperfluorescent, and the vessels themselves eventually
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| stand out in negative relief (Figs 8, 9). The late hyperfluorescence outlines
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| the full extent of the palisadal fibrovascular tissues and allows them to be
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| Visualized more clearly. The interpalisades also become more visible
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| because they are relatively hypofluorescent at this stage. The lack of
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| hyperfluorescence that characterizes the interpalisades is probably due to
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| their remoteness from leaking vessels and the lesser amount of fibrovascular connective tissue in the substantia propria underlying the epithelial
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| rete ridges. The rete ridges themselves may have inter- or intracellular
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| barriers to diffusion of fluorescein.
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|
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| In eyes characterized by anterior segment inflammation, particularly
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| infectious conjunctivitis such as that caused by adenoviruses, the amount of
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| fluorescein leakage and hyperfluorescence are much greater (Fig 8). All the
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| paralimbal vessels dilate, and the palisadal vessels are more easily seen.
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| Palisades of Vogt 163
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|
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| FIGURE 7
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| Angiogram of lower limbal region shown in Fig 1A. A: Vessels of palisades (triple white
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| arrows) fill extremely quickly, at about same time as terminal capillary loops (single white
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| arrow). Both sets of vessels leak fluorescein slightly, and to lesser extent than bulbar vessels
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| of conjunctiva (open black arrows). B: Later venous stage of angiogram seen in Fig 7A. Very
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| little additional leakage is seen from vessels of palisades and from terminal capillary loops of
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| the marginal arcades, whereas bulbar conjunctiva is intensely hyperfluorescent due to
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| extreme leakage.
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| 164 Goldberg
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|
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| FIGURE 8
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| Angiogram of normal limbus. A: Early arterial phase. Vessels of palisades (triple arrows) have
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| not yet become perfused. Open white arrow indicates same vessel in all phases of angiogram.
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| B: A few seconds later, vessels of palisades contain fluorescein (triple arrows), but there is
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| almost no leakage. Other bulbar vessels of conjunctiva have begun to leak (double arrows). C:
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| Early venous phase shows mild leakage from vessels of palisades (triple arrows). D: Late
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| venous phase shows little increase in leakage from vessels of palisades (triple arrows),
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| although leakage from larger vessels of conjunctiva has increased markedly.
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|
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| Furthermore, the palisadal tissue appears to enlarge, possibly because of
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| inflammatory edema and cellular infiltration, and the palisades become
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| wider than the interpalisades contrary to their normal proportions.
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|
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| HISTOLOGIC FINDINGS
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|
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| Routine histology of the human limbus confirms the presence of fibrovas—
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| cular palisades interdigitating with epithelial rete ridges (Fig 10). The
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| palisades contain nerves, arteries, veins, and lymphatics. They are considerably narrower than the adjacent epithelial ridges when uninflamed.
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| The epithelium of the ridge-shaped interpalisade ranges from about 10 to
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| 15 cells in thickness or more, whereas that overlying the palisade may be
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| only 2 to 3 cells thick or slightly more. In comparison, the corneal
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| epithelium is about 5 cells in thickness.
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| Palisades of Vogt 165
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|
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| FIGURE 9
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| Angiogram of limbus from patient with adenoviral conjunctivitis. A: Mid-venous phase. Note
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| hyperfluorescence of palisades (arrows) and negative image of their vessels. B: Late venous
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| phase. Palisades (arrows) are enlarged when inflamed, and amount of fluorescein leakage is
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| increased.
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| 166 Goldberg
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|
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| _ FIGURE 10
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| Histologic appearance of palisades of Vogt. The palisade is narrower than the interpalisade,
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| and contains blood vessels (arrows) (hematoxylin and eosin). A: Limbus of 84-year-old
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| woman. B: Another limbal area from same subject.
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|
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| DISCUSSION
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|
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| The palisade zone is clearly a specialized anatomic area, with differentiated
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| ridges of thickened epithelium (the interpalisades) and a distinctive blood
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| supply. The functions of these two components of the palisade zone, in
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|
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| » both normal and abnormal states, can only be surmised at the present time. T‘
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|
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| The palisadal vessels may serve to supply the metabolic needs of the large
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| number of epithelial cells comprising the interpalisades, or may have some
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| other fiinction. The interpalisades may represent a repository of replicating
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| epithelial cells that slide inferiorly from the upper limbus and superiorly
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| from the lower limbus where they exist in abundance. If so, they could
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| normally serve to replace aging and dying cells in the central cornea and
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| could be called upon to replace corneal epithelial cells that are destroyed
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| by trauma or by other disease processes. A lack of a normal number of
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| limbal epithelial cells or improper replication or migration might well be
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| responsible for delayed epithelialization of the cornea in a wide variety of
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| disease states; eg, alkali burns, etc. The radial distribution of the palisades
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| and interpalisades along the superior and inferior limbus may also explain
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| the characteristic verticillate pattern of the corneal epithelium in such
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| disorders as F abry’s disease and drug-induced degeneration.7 In these
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| circumstances one may theorize that the radial epithelial ridges at the
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| limbus send columns of cells onto the surface of the cornea, causing their
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| typical curvilinear distribution.
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|
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| Whatever their function, the anatomy of the palisades and interpalisades
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| is remarkably similar to the dermatoglyphic (“skin carving”) configuration
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| of the cutaneous epithelium on the plantar and volar surfaces of the hands
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| Palisades of Vogt 167
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|
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| and feet. Here, as in the limbus, parallel rows of epithelial rete ridges
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| interdigitate with cords of fibrovascular connective tissue. In analogy with
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| the skin, the characteristic limbal anatomy can be called “conjunctivoglyphics” (“conjunctival carvings”) or “limboglyphics." There are several
| |
| additional points of similarity. The glyphics are not present on all skin
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| surfaces, nor are they found throughout the conjunctiva. Holocrine glands
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| or cells (sebaceous in the skin; goblet cells in the conjunctiva) are missing
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| from both of these specialized structures. The ridge patterns are unique to
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| each individual in the skin (eg, fingerprints) and also appear unique in the
| |
| conjunctiva. One difference between the dermatoglyphics and conjunctivoglyphics is the presence of eccrine (sweat) gland openings on the epithelial rete ridges in the former, and their absence in the latter.
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|
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| In the skin there are characteristic changes in the ridge patterns in
| |
| different diseases (eg, trisomies, chromosomal deletions, ectodermal dysplasia, congenital rubella,‘ nail-patella syndromem); some minor differences between males and females; and some racial differences in the types
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| of individual ridge patterns. “'16 Whether or not the study of conjunctivaglyphics proves to be as clinically or genetically as rewarding as that of
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| dermatoglyphics remains to be seen. In any event it would be desirable to
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| study the palisades and interpalisades to determine the following: if there
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| are age, race, sex, or twin differences; if there are associations with
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| chromosomal diseases; and if there are characteristic changes with such
| |
| acquired diseases as recurrent corneal erosions, delayed graft epithelialization, chemical burns, melting diseases of the limbus, and various limbal
| |
| operations including fomix- and limbal-based flaps of the conjunctiva.
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|
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| It is of interest that a large number of previous angiographic
| |
| studies1’9’17"°‘4 have failed to visualize or describe the vasculature of the
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| palisades of Vogt. Good clinical descriptions and diagrams may be found in
| |
| the work by Vogt, himself,3 by Craves,8 by Hogan et al,‘°‘5 and by DukeElder and Wybar.26 The fact that fluorescein leakage from the palisadal
| |
| vessels occurs relatively late in the angiographic sequence and is relatively
| |
| mild suggests that some intercellular junctional complexes in the endothelium may be functionally competent and/or that there are few, if any,
| |
| endothelial fenestrations. In an electron microscopic study of conjunctival
| |
| vessels Hogan was able to demonstrate some zonulae occludentes, only a
| |
| few cytoplasmic fenestrations, good basement membrane formation, and a
| |
| few pericytes. 25 In any event, the angiographic appearance of the palisadal
| |
| vessels suggests that this distinctive microvasculature has functional properties different from those of the more peripheral bulbar conjunctiva.
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| 168 Goldberg
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|
| |
| SUMMARY
| |
|
| |
| The palisades of Vogt are distinctive normal features of the human corneoscleral limbus. Our clinical studies indicate that they are more discrete
| |
| in younger and in more heavily pigmented individuals, and that they
| |
| appear more regular and prominent at the lower limbus than at the upper
| |
| limbus. They are seen only infrequently in the horizontal meridian. There
| |
| is some symmetry (though it is not exact) from one eye to the other in the
| |
| same person. The anatomy of the palisades appears to be unique for a given
| |
| individual. In this respect, as well as in their microscopic anatomy, the
| |
| palisades of Vogt appear comparable to fingerprints, and the term “conj unctivoglyphics” (“conjunctival carvings”) or “limboglyphics” is suggested
| |
| in analogy with “dermatoglyphics.”
| |
|
| |
| The palisades of Vogt have a distinct vasculature with narrow, barely
| |
| visible, arterial and venous components of radially oriented hairpin loops.
| |
| Angiography reveals that these vessels leak fluorescein relatively late and
| |
| only to a moderate extent. They respond to inflammation by dilatation and
| |
| gross breakdown of their physiologic barrier properties.
| |
|
| |
| The functions of the palisades of Vogt are not known with certainty, but
| |
| their interpalisadal epithelial rete ridges may serve as a repository for
| |
| corneal epithelial cells. They may thus be important in both aging and
| |
| diseases of the cornea.
| |
|
| |
| REFERENCES
| |
|
| |
| 1. Bron A], Goldberg MF: Clinical features of the human limbus, in Trevor-Roper P (ed):
| |
| The Cornea in Health and Disease: Proceedings of the Vlth Congress of the European
| |
| Society of Ophthalmology. London, Academic Press Inc, 1981.
| |
|
| |
| 2. Aurell G, Komerup T: On glandular structures at the comeo-scleral junction in man and
| |
|
| |
| swine: The so-called “Manz glands.” Acta Ophthalmol 27:19, 1949.
| |
|
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| Vogt A: Atlas of the Slitlamp-Microscopy of the Living Eye. Berlin, Springer, 1921.
| |
|
| |
| Dobree JH: Superficial perilimbal vessels in the normal and congested eye. Br ]
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|
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| Ophthalmol 34:720, 1950.
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|
| |
| 5. Maumenee AE: Repair in the cornea, in Montagna W, Billingham RE (eds): Advances in
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| Biology of Skin. New York, Macmillan Co, 1964, vol 5.
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|
| |
| 6. von Heydenreich A: Die Zellmigration im Bereich der Hornhaut. Ber Dtsch Ophthalmol
| |
| Ces 62:287, 1959.
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|
| |
| 7. Bron A]: Vortex patterns of the corneal epithelium. Trans Ophthalmol Soc UK 93:455,
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|
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| 1973.
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|
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| Graves B: Certain clinical features of the normal limbus. Br] Ophthalmol 18:305, 1934.
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|
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| Bron A], Easty DL: F luorescein angiography of the globe and anterior segment. Trans
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|
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| Ophthalmol Soc UK 90:339, 1970.
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|
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| 10. Verbov ]: Clinical significance and genetics of epidermal ridges: A review of der
| |
| matoglyphics. ] Invest Dermatol 54:26l, 1970.
| |
| 11. Miller JR: Dermatoglyphics. ] Invest Dermatol 60:435, 1973.
| |
|
| |
| 12. Holt SB: The significance of dermatoglyphics in medicine: A short survey and summary.
| |
| Clin Pediatr 12:47l, 1973. '
| |
|
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| 99°
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|
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| 599°
| |
| Palisades of Vogt 169
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|
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| 13. Preus M, Fraser F C: Dermatoglyphics and syndromes. Am] Dis Child 124:933, 1972.
| |
|
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| 14. Cherrill FR: The Finger Print System at Scotland Yard. London, Her Majesty's Stationery Oflice, 1954.
| |
|
| |
| 15. Schaumann B, Alter M: Dermatoglyphics in Medical Disorders. New York, SpringerVerlag, 1976. ’
| |
|
| |
| 16. Holt SB: The Genetics of Dermal Ridges. Springfield, Ill, Charles C Thomas, 1968.
| |
|
| |
| I7. Easty DL, Bron A]: F luorescein angiography of the anterior segment: Its value in corneal
| |
| disease. Br J Ophthalmol 55:671, 1971.
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|
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| 18. Mitsui Y, Matsubara M, Kanagawa M: Fluorescence irido-corneal photography. Br I
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| Ophthalmol 53:505, 1969.
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|
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| 19. Fetkenhour CL, Choromokos E: Anterior segment fluorescein angiography with a retinal
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| fundus camera. Arch Ophthalmol 962711, 1978.
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|
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| 20. Bruun-Jensen J: F luorescein angiography of the anterior segment. Am ] Ophthalmol
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| 67:842, 1969.
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|
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| 21. Amalric P, Rebi E: New indications of fluorescein angiography of the anterior segment of
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| the eye: IV. Several examples of scleral and corneal pathology. Ann Ocul (Paris) 204:73l,
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| I971.
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|
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| 22. Marsh R], Ford SM: Blood flow in the anterior segment of the eye. Trans Ophthalmol Soc
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|
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| UK 1002388, 1980.
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|
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| Talusan ED, Schwartz B: Fluorescein angiography: Demonstration of flow pattern of
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|
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| anterior ciliary arteries. Arch Ophthalmol 99:1074, 1981.
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|
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| M inatoya H, Acacio I, Goldberg MF : F luorescein angiography of the bulbar conjunctiva
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|
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| in sickle cell disease. Ann Ophthalmol 5:980, 1973.
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| Hogan M], Alvarado ]A, Weddell IE: Histology of the Human Eye: An Atlas and
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| Textbook. Philadelphia, WB Saunders, 1971.
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|
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| 26. Duke-Elder S, Wybar KC: The Anatomy of the Visual System: System of Ophthalmology.
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|
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| London, Henry Kimpton, 1961, vol 2.
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|
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| 3°»
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| 3-’
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| $3
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| DISCUSSION
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|
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| DR VVILLIAM H SPENCER. The authors have carefully studied the biomicroscopic
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| appearance, vascular dynamics and anatomic substrate of the specialized epithelial
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| and subepithelial fibrovascular structures located at the limbus known as the
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| “palisades of Vogt. " The authors note considerable variation in pattern, distribution
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| and number of ridge-like palisades from one person to another and suggest that,
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| like fingerprints, the limbal palisades are distinctive for a given individual. The
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| authors speculate about the function of the epithelial and vascular components
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| noting that the thick layer of inter-palisadal epithelial cells may serve as a depot of
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| cells ready to migrate onto the cornea to replace diseased or destroyed corneal
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| epithelial cells, and they suggest that the vessels serve to nourish these cells.
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|
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| In histologic sections of normal skin the border between the dermis and epidermis is irregular due to the presence of dermal papillae that extend upward into
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| the epidermis. The ridges of epidermis separating the papillae are known as rete
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| ridges. This pattern is relatively inconspicuous wherever the skin is loosely
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| adherent to underlying tissues, but is quite prominent at sites of firm subepithelial
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| adhesions. In the hand the skin of the dorsum is quite “loose” and has relatively few
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| rete ridges, but the firmly attached palmar surface of the skin contains many ridges.
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| Similarly the thin skin of the eyelid surface containing epithelium of uniform
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| 170 Goldberg
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|
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| thickness is readily “ballooned up" by a subepithelial injection of fluid until the lid
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| margin is reached where firm rete ridges and dermal papillae inhibit further fluid
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| dissection. These anatomic specializations are also found in mucous membrane,
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| especially at zones of transition and attachment. Doctors Goldberg and Bron have
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| called our attention to the anchoring sites of the conjunctiva at the limbus.
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| Corresponding attachments are found where the conjunctiva adheres to the tarsus
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| and to the lid margin at the mucocutaneous junction. In the tarsus the spread of
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| vascular and perivascular inflammation is to a degree limited by these structures
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| causing characteristic papillae to form, some with a “paving block" configuration.
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| The spread of inflammatory transudate from the vessels of the limbal palisades may
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| also be in part limited by the inter-palisadal attachments. Perhaps this accounts for
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| the papillary configuration of the circumscribed elevations occasionally seen at the
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| limbus in individuals with vernal kerato-conjunctivitis. i ‘
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|
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| The authors have provided us with interesting data pertaining to the fluorescein
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| leakage pattern from normal palisadal vessels. It is to be hoped that they will
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| continue this investigation since so little is known about the responses of these
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| vessels to a variety of stimuli and the role that they play in such diverse conditions as
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| peripheral corneal immune reactions and the development of a pannus.
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|
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| One of the most intriguing aspects of this study is the suggestion that the thick
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| layer of inter-palisadal epithelial cells can serve as a repository for cells that can
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| migrate onto the cornea to replace diseased or destroyed corneal epithelial cells.
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| Normally the epithelial cells of the cornea are, in part, replaced by cells from the
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| basal layer where cell division takes place. Undoubtedly central migration of
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| peripheral cells also occurs. As evidence of this phenomenon the authors draw our
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| attention to the characteristic vertically oriented curvilinear pattern of corneal
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| epithelial opacification that occurs in F abry’s disease and after utilization of drugs
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| such as Amiodarone or chloroquine. Additional evidence is seen in another
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| condition occurring primarily in blacks, known as striate melanokeratosis where
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| limbal pigment bearing cells migrate toward the center of the cornea after chronic
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| inflammation or injury. I would like to ask if the authors have observed the pattern
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| of opacification in Fabry's disease to begin at the superior and inferior limbus and to
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| advance centrally. These photographs from the collection of Doctor Richard Abbott
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| at the Pacific Medical Center in San Francisco show the characteristic pattern of
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| corneal epithelial opacification in Fabry’s disease and after use of Amiodarone. The
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| participation by peripheral cells in the process is diflicult to determine. I would
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| assume that the cells most likely to become affected would be those that are most
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| active metabolically, and would expect the opacity to arise centrally as well as
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| peripherally. Perhaps an animal model using a radiomarker, such as tritiumlabeled thymidine, could be used to study the participation of the inter-palisadal
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| epithelial cells in these conditions, and in the normal turnover of corneal epithelial
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| cells.
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|
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| I very much appreciate the opportunity to discuss this fine contribution to the
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| literature and wish to thank the authors for sending me their manuscript well in
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| advance of the meeting.
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| Palisades of Vogt . 171
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|
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| DR GEORGE SPAETH. One observation on gonioscopy is that the posterior trabecular
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| meshwork is almost always less pigmented in the 3:00 and 9:00 o'clock positions
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| than elsewhere. I have never been able to understand this. I wonder if Doctor
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| Goldberg believes that there is less flow of aqueous out of these particular areas,
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| which may explain this peculiar distribution of pigmentation or rather lack of
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| pigmentation in these areas.
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|
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| DR MORTON GOLDBERG. Thank you. With respect to Doctor Spaeth’s query, I have no
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| explanation of that observation. We do not think that it would be directly attributable to the palisades. With respect to Doctor Spencer’s comments, I think
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| they were extremely valuable. The labelling studies would, in a proper subhuman
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| primate, probably answer the question as to the migration of pericorneal cells onto
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| the center of the cornea. There is no doubt, from a variety of animal as well as
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| human studies, that surface corneal epithelial cells come not only from the basal
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| layer of the corneal epithelium but also from the pericomeal limbus. The pericomeal limbal cells have a higher mitotic rate than those in the center of the cornea.
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| One might theorize, therefore, that the more rapidly reproducing cells might
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| migrate into zones where the reproduction rate is slower. That would explain the
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| appearance we see in the otherwise dissimilar whirlpool or vortex patterned
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| dystrophies of the corneal epithelium. This group of diseases is extremely heterogeneous from the etiologic point of view. There are, for example, inherited
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| storage diseases, such as Fabry's disease, in which macrolipid marks the presence
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| of the apparently migrating corneal epithelial cells. One sees the same biomicroscopic appearance in toxic keratopathies, such as those caused by chloroquine
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| and Amiodarone. One sees the same thing as a normal manifestation of epithelial
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| slide in heavy pigmented individuals (striate melanokeratosis). It would seem that
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| the common denominator of these quite dissimilar diseases would involve the
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| pattern of cell migration, because these conditions have virtually nothing else in
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| common. However, the proof is in the pudding, and we have not performed the
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| experiments suggested by Doctor Spencer. I would agree that further work is
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| indicated, and I hope that many of the members would proceed with it.
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