|A personal message from Dr Mark Hill (May 2020)
| I have decided to take early retirement in September 2020. During the many years online I have received wonderful feedback from many readers, researchers and students interested in human embryology. I especially thank my research collaborators and contributors to the site. The good news is Embryology will remain online and I will continue my association with UNSW Australia. I look forward to updating and including the many exciting new discoveries in Embryology!
These notes introduce the development of the eye: induction and regional specification of the eye structures, maturation and formation of retina and optic tectum neuronal connections.
The adult eye has contributions from several different embryonic layers eventually forming neuronal, supportive connective tissue, optical structures, and muscular tissues.
There are additional pages shown in the vision links, covering specific topics of vision development.
Some Recent Findings
Adult Human Retina histology
- The relationship between eye movement and vision develops before birth  "While the visuomotor system is known to develop rapidly after birth, studies have observed spontaneous activity in vertebrates in visually excitable cortical areas already before extrinsic stimuli are present. Resting state networks and fetal eye movements were observed independently in utero, but no functional brain activity coupled with visual stimuli could be detected using fetal fMRI. This study closes this gap and links in utero eye movement with corresponding functional networks. BOLD resting-state fMRI data were acquired from seven singleton fetuses between gestational weeks 30-36 with normal brain development. During the scan time, fetal eye movements were detected and tracked in the functional MRI data. We show that already in utero spontaneous fetal eye movements are linked to simultaneous networks in visual- and frontal cerebral areas. In our small but in terms of gestational age homogenous sample, evidence across the population suggests that the preparation of the human visuomotor system links visual and motor areas already prior to birth."
- Activation of c-Jun N-Terminal Kinase (JNK) during Mitosis in Retinal Progenitor Cells "Most studies of c-Jun N-terminal Kinase (JNK) activation in retinal tissue were done in the context of neurodegeneration. In this study, we investigated the behavior of JNK during mitosis of progenitor cells in the retina of newborn rats. ... The data show, for the first time, that JNK is activated in mitotic progenitor cells of developing retinal tissue, suggesting a new role of JNK in the control of progenitor cell proliferation in the retina."
- Rearrangement of retinogeniculate projection patterns after eye-specific segregation in mice "When monocular enucleation was performed after eye-specific segregation, rearrangement of retinogeniculate axons in the dorsal lateral geniculate nucleus (dLGN) was observed within 5 days. ...We also examined the critical period for this rearrangement and found that the rearrangement became almost absent by the beginning of the critical period for ocular dominance plasticity in the primary visual cortex."
- The long noncoding RNA RNCR2 directs mouse retinal cell specification"We find that the RNCR2 is selectively expressed in a subset of both mitotic progenitors and postmitotic retinal precursor cells. ShRNA-mediated knockdown of RNCR2 results in an increase of both amacrine cells and Müller glia, indicating a role for this lncRNA in regulating retinal cell fate specification."
|More recent papers
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Search term: Vision Development
<pubmed limit=5>Vision Development</pubmed>
Search term: Vision Embryology
<pubmed limit=5>Vision Embryology</pubmed>
- Weeks 3 - 4 Eye Fields-Optic Vesicle
- Weeks 5 - 6 Optic Cup, Lens Vesicle, Choroid Fissure, Hyaloid Artery
- Weeks 7 - 8 Cornea, Anterior Chamber, Pupillary Membrane, Lens, Retina
- Weeks 9 - 15 Iris, Ciliary Body
- Weeks 8 - 10 Eyelids
Carnegie Stages - Eye
|The following data is from a study of human embryonic carnegie stages and other sources.
- Stage 10 - optic primordia appear.
- Stage 11 - right and left optic primordia meet at the optic chiasma forming a U-shaped rim.
- Stage 12 - optic neural crest reaches its maximum extent and the optic vesicle becomes covered by a complete sheath,
- Week 4 - Stage 13 - By the end of the fourth week the optic vesicle lies close to the surface ectoderm. Optic evagination differentiation allows identification of optic part of retina, future pigmented layer of retina, and optic stalk. The surface ectoderm overlying the optic vesicle, in response to this contact, has thickened to form the lense placode.
- Week 5 - Stage 14 - (about 32 days) the lens placode is indented by the lens pit, cup-shaped and still communicates with the surface by a narrowing pore.
- Week 5 - Stage 15 - (about 33 days) the lens pit is closed. The lens vesicle and optic cup lie close to the surface ectoderm and appear to press against the surface.
- Week 6 - Stage 16 - (37 days) Growth of the lens body results in a D-shaped lens cavity. Perilental blood vessels (tunica vasculosa lentis) are visible. Prior to the development of the eyelids, one small sulcus or groove forms above the eye (eyelid groove) and another below it.
- Week 6 to 7 - Stages 17 - 19 - Retinal pigment is visible and the retinal fissure is largely closed. Eyelids grooves deepen, eyelid folds develop, first below, and then above, the eye.
- Week 7 - Stages 18 - Mesenchyme invades the region between the lens epithelium and the surface ectoderm.
- Week 7 to 8 - Stages 19 - 22 - the eyelid folds develop into the eyelids and cover more of the eye as the palpebral fissure takes shape. Stage 19 the upper and the lower eyelids meet at the outer canthus (palpebral commissure, corner of the eye where the upper and lower eyelids meet).
- Week 8 - Stage 20 - The lens cavity is lost and a lens suture begins to form. The inner canthus (palpebral commissure, corner of the eye where the upper and lower eyelids meet) is established.
- Week 8 - Stage 23 - The retina comprises the pigmented layer, external limiting membrane, proliferative zone, external neuroblastic layer, transient fiber layer, internal neuroblastic layer, nerve fiber layer, and internal limiting membrane. Eyelids closure is complete (Note - shown as still open in the Kyoto embryo).
|Embryo Virtual Slides|
The lens or crystalline lens or aquula (Latin, aquula = a little stream) has a key role in focussing light (with the cornea) upon the neural retina. The lens embryonic origin is from surface ectoderm of the sensory placodes that form in the head region (More? Week 4 - Placodes). The lens focusses by refracting light as it passes through the biconvex lens, which can be altered in shape (accommodation) by surrounding ciliary muscles. These ciliary muscles are activated (contracted) by parasympathetic innervation from the ciliary ganglion itself innervated by the oculomotor nerve (Cranial Nerve III) (More? Cranial Nerves).
surface ectoderm -> lens placode -> lens pit -> lens vesicle -> lens fibres -> lens capsule and embryonic/fetal nucleus.
- Links: Vision - Lens Development
Stage 22 Eye
The images below link to virtual slides of the human developing eye at Carnegie stage 22. Click on the image to open or select specific regions from the regions of interest links.
Links: Embryo Virtual Slides
This neuroscience term describes how the developing retina is precisely "mapped" onto the visual cortex through a series of signaling and activity dependent mechanisms. This follows from Hubel and Wiesel (1981 Nobel Prize in Physiology or Medicine) key discoveries (1959-70) of how in development system matching occurs in the visual system. The topographic map establishes an ordered neuronal connection between sensory structures and the central nervous system.
The retinotectal map (eye to brain) of birds (lower vertebrates):
- temporal (posterior) retina is connected to the rostral (anterior) part of the contralateral optic tectum
- nasal (anterior) retina to the caudal (posterior) tectum
- ventral retina to the dorsal (medial) tectum
- dorsal ventral (lateral) tectum
Retinal waves a form of coordinated spontaneous activity that occurs in the developing retina. These waves of electrical activity (action potentials) are thought to have a role in establishing the initial retinotopic map by correlating/coordinating the activity of neighbouring retinal ganglion cells.
EphA/ephrin-A molecular signaling also thought to have a role in establishing the initial retinotopic map.
Mouse eye neural crest
Mouse eye TGF-beta model
- Links: Image - Mouse eye neural crest | Image - Mouse eye TGF-beta model | Vision Development | Neural Crest Development | Head Development
Schematic showing the stages of Schlemm's canal development in the postnatal mouse by the novel process of canalogenesis.
(Cartoons have been drawn for clarity and are not intended to suggest that most early sprouts arise from the LVP.)
Extraocular muscles are required to move the eye within the orbit. Their embryonic origin requires an interaction between the cranial mesoderm and the migrating neural crest cells.
The following is from a recent paper comparing human to zebrafish muscle development.
|About the Muscles
- Five of the six muscles (inferior rectus, superior rectus, lateral rectus, medial rectus, and superior oblique) originate at a common tendinous ring of fibrous tissue (the Annulus of Zinn).
- The Annulus of Zinn surrounds the optic nerve, ophthalmic artery, and ophthalmic vein at their entrance through the apex of the orbit.
- The sixth muscle (inferior oblique) has a separate origin point on the orbital side of the bony maxilla at the anterior inferomedial strut.
- IR - inferior rectus
- SR - superior rectus
- LR - lateral rectus
- MR - medial rectus
- SO - superior oblique
- IO - inferior oblique
- Links: Extraocular Muscles
Human stage 22 developing iris region
Human stage 22 developing iris region
Human stage 22 overview of optic nerve
Human stage 22 overview of eye
Human stage 22 lens and hyaloid vessels
Human stage 22 optic nerve (stalk)
Mouse adult optic nerve axons
Fig. 456. Location of optic areas before the closure of the neural groove.
Fig. 457. Location of areas shown in Fig. 456 after the formation of the neural canal.
Fig. 458. Location of the optic area after the beginning of the formation of the optic cup and optic stalk. Fig. 459. Dorsal view of head of chick of 58 hours' incubation.
Fig. 460. Section through head of chick of two days' incubation.
Fig. 461. Section through head of chick of three days' incubation.
Fig. 462. Later stage in development of optic cup and lens than is shown in Fig. 461.
Fig. 463. Developing lens and optic cup.
Fig. 464. Model showing lens and formation of optic cup.
Fig. 465. Stages in the development of the lens in the rabbit embryo.
Fig. 466. Section through optic cup and lens invagination of chick of fifty-four hours' incubation.
Fig. 467. Section through eye of human embryo of 13-14 weeks.
Fig. 468. Development of the retinal cells.
Fig. 469. Vertical section through retina of a four months' human embryo.
Fig. 470. Vertical section through retina of a five and one-half months' human embryo.
Fig. 1. Section through head of pig, 2 mm long.
Fig. 2. Section through head of chick, 2 mm long.
Fig. 3. Section through head of Foetal Pig, 2 mm long.
Fig. 4. Section through head of Foetal Pig, 3 mm long.
Fig. 5. Section through head of Foetal Pig, 3 mm long.
Fig. 6. Section through head of Foetal Pig, 4 mm long.
Fig. 7. Section through head of Foetal Pig, 7 mm long.
Fig. 8. Section through head of pig, 8 mm long.
Fig. 9. Section through head of pig, 9 mm long.
Fig. 11. colobomba of the fundus in the adult and means a lack of development.
The International Journal of Developmental Biology Vol. 48 Nos. 8/9 (2004) Eye Development
Bookshelf vision development
Search Pubmed: vision development | eye development | eye embryology | retina embryology | lens embryology
Search Entrez: vision development | eye development | eye embryology | retina embryology | lens embryology
- annular tendon - (common tendinous ring, annulus of Zinn) fibrous tissue surrounding the optic nerve forming the origin for five of the six extra ocular muscles.
- AXIN2 - a scaffold protein that is an antagonist and universal target of the Wnt/β-catenin pathway required for visual development. OMIM - AXIN2
- canthus - (palpebral commissure) the corner of the eye where the upper and lower eyelids meet.
- Cloquet's canal - historic term for the hyaloid canal. Named after Jules G. Cloquet (1790-1883) a French anatomist.
- cranial nerve 2 - (CN II, optic nerve) the cranial nerve consisting of retinal ganglion cell axons and glia forming the connection with the brain (pathway: retina, optic disc, optic chiasma, optic tract, lateral geniculate nucleus, pretectal nuclei, and superior colliculus).
- extraocular muscles - six muscles that control movement of the eye (superior, Inferior, lateral and medial rectus; superior and inferior oblique).
- fovea - (fovea centralis; Latin, fovea = pit) retina region located in the center of the macula, required for sharp central vision.
- ganglion cell layer - (retinal ganglion layer) the layer of the retina where retinal ganglion cell bodies lie.
- hyaloid canal - a developmental feature in the embryo contains the hyaloid artery that supplies blood to the developing lens.
- macula - (Latin, macula = spot; lutea = yellow) region near the center of the retina containing two or more layers of ganglion cells.
- meibomian glands - eyelid gland that secrete meibum, generates the lipid layer of the tear film that prevents excessive evaporation of tear fluid.
- nasolacrimal groove - (lacrimal groove) an embryonic surface feature between the maxillary and the lateral nasal process that will later fuse to form the lacrimal duct running between the eye and the nasal inferior meatus.
- optic chiasm (optic chiasma) CN II region where some of the axons (partial) cross to the opposite side.
- optic cup - the in-folded extension of the optic stalk from the diencephalon that forms the retina.
- optic disc - (optic nerve head) region on the retina where the retinal ganglion cells exit to form CN II.
- optic placode - (lens placode) surface ectoderm that folds inward to form the developing lens.
- retina - The stratified sensory structure of the eye, formed from the neural ectoderm that extends from the forebrain (diencephalon) to form initially the folded optic cup. Vertebrates have ten identifiable layers formed from nerve fibers, neurons, membranes, photoreceptors and pigmented cells. Light must pass through nearly all these layers to the photoreceptors. (1. Inner limiting membrane - Müller cell footplates; 2. Nerve fiber layer; 3. Ganglion cell layer - layer of retinal ganglion cells their axons form the nerve fiber layer and eventually the optic nerve; 4. Inner plexiform layer - another layer of neuronal processes; 5. Inner nuclear layer; 6. Outer plexiform layer; 7. Outer nuclear layer; 8. External limiting membrane - layer separating inner segment portions of photoreceptors from their cell nuclei; 9. Photoreceptor layer - rods and cones that convert light into signals; 10. Retinal pigment epithelium).
- retinal pigment epithelium - (RPE, pigmented layer) An epethial pigmented cell layer lying outside the sensory retina, formed from the outer layer of the folded optic cup. The RPE is firmly attached to the underlying choroid and overlying retinal visual cells, for which it has a nutritional role.
- retinal waves - A form of coordinated spontaneous activity that occurs in the developing retina. These waves of electrical activity (action potentials) along with EphA/ephrin-A signaling are thought to have a role in establishing the initial retinotopic map by correlating/coordinating the activity of neighbouring retinal ganglion cells.
- Stilling's canal - historic term for the hyaloid canal. Named after Benedict Stilling (1810-1879) a German anatomist.
- YAP - (Yes-Associated Protein) transcriptional regulator required for retinal progenitor cell cycle progression and RPE cell fate acquisition. PMID 27616714 OMIM - YAP1
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Cite this page: Hill, M.A. (2020, August 12) Embryology Sensory - Vision Development. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Sensory_-_Vision_Development
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