Chronology of Eye Development PDF

Chronology of Eye Development Maria Traka, PhD  Development of the eye (sulcus) Day 22 Neuroectoderm retina, iris, optic nerve Ectoderm (surface) lens Mesoderm vascular and fibrous coat of the eye /prosencephalon...

Chronology of Eye Development Maria Traka, PhD  Development of the eye (sulcus) Day 22 Neuroectoderm retina, iris, optic nerve Ectoderm (surface) lens Mesoderm vascular and fibrous coat of the eye /prosencephalon Week 5  Week 7 The invagination of the optic vesicle is more extensive inferiorly and a cleft called the choroid fissure (or optic fissure) is formed The mouth of the optic cup forms a round opening that will be the future pupil  1. Retina: Pigmented epithelium (outer layer)/ Photoreceptive retina (posterior 4/5 of the eye). Optic cup 2. Ciliary body partially derived from epithelial layer of the optic cup and partially from adjacent mesenchyme. 3. Iris posteriorly covered by epithelial layer of optic cup (give rise to sphincter pupillae and dilator pupillae) and anteriorly derived from mesenchyme.  optic nerve and the obliteration on the anterior portion of the hyaloid Optic stalk vessels become a remnant (hyaloid canal of the vitreous body). Optic nerve myelination is complete by 10 weeks postnatally Optic stalk is surrounded by meninges of the brain. Dura matter is continuous with the sclera. Mesenchyme adjacent to optic cup forms the sclera Mesenchyme anterior to the lens vacuolizes and the space becomes the anterior chamber of the eye Mesenchyme is split by the chamber in an inner layer (iridopupillary membrane) and outer layer (cornea) The iridopupillary membrane obliterates and opens communication between anterior and posterior chamber of the eye The eyelids open around week 26 Congenital defects: Coloboma iris: choroid fissure fails to close and a cleft persists. Potentially effecting iris, but also ciliary body, retina, optic nerve REMNANTS OF IRIDOPUPILLARY MEMBRANE IRIS PUPILLARY APERTURE Congenital cataract: the lens becomes opaque during intrauterine life. It is mostly due to gene mutations Bell and Oluonye,et al., 2020 Therapeutic Advances in Rare Disease  Histology of the eye 1 Transparent Cornea (1) Densely innervated avascular lens Posterior 5/6 of the eye Sclera (1) Rich in collagen and elastic fibers Avascular Lens Progressively less elastic Opacity = cataract choroid Uvea (2) iris ciliary body (suspensory ligaments & ciliary muscle for lens 1 2 3 accommodation) Retina (3) (outgrowth of the diencephalon)  Iris affects brightness & quality of light entering eye Pupillary sphincter  constriction of pupil (miosis) pupil Pupillary dilator  dilation of pupil (mydriasis) Modulated by ANS Corneoscleral junction cornea Anterior Anterior chamber Compartment iris filled with watery Posterior chamber aqueous humor lens Posterior compartment filled with gelatinous vitreous humor Histology of the eye 1 Transparent Cornea (1) Densely innervated avascular lens Posterior 5/6 of the eye Sclera (1) Rich in collagen and elastic fibers Avascular Progressively less Lens elastic Opacity = cataract choroid iris Uvea (2) ciliary body suspensory ligaments 1 2 3 Retina (3) (outgrowth of the diencephalon)  Outer facing the choroid layer Seven Retinal cell types Different layers inner layer facing vitreous humor 14  Photoreceptors: rods & cones 125 million/retina Rods 20:1 cone Both contain light-absorbing photopigments Rods contribute to night vision (scotopic) Cones work during daytime (photopic) 3 types of cone pigments (RBG colors) 15  CONVERGENCE 10-100 rods to 1 bipolar 1 cone to 1 bipolar = more acuity Rods: high convergence Cones: low convergence More visual acuity  Optic disc or papilla (blind spot) Fovea centralis (sharpest vision and acute color discrimination) Macula lutea (area of central vision)  The retina is regionally specialized No photoreceptors in blind spot  rods/cones in periphery Fovea is rich in cones Fovea specializes in high light vision, periphery in lowlight vision 19 As the optic nerve exits the eye globe it is invested by all three meningeal layers. Increased cranial pressure causes CSF to compress ophthalmic vessels. Bulge of fluid at the optic disc (papilledema) Questions: [email protected]