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cornea

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  cornea The cornea is the clear, transparent, dome-shaped front surface of the eye. It covers the iris, pupil, and anterior chamber, and it is the main refractive surface of the eye. Key Features of the Cornea Transparency → allows light to enter the eye. Shape → convex, more curved than the sclera. Thickness → Central cornea: ~0.5 mm Peripheral cornea: ~1 mm Diameter → ~11–12 mm (horizontal), ~10–11 mm (vertical). Refractive Power → ~43 diopters (≈ 2/3 of the total eye’s focusing power). Avascular → no blood vessels; nourished by tears, aqueous humor, and limbal vessels. Nerve Supply → trigeminal nerve (ophthalmic division); very sensitive to touch and pain. 🔹 Layers of the Cornea (outside → inside, 5 layers) Epithelium – stratified squamous; regenerates quickly. Corneal Epithelium It is the outer protective layer of the cornea. Makes up about 10% of corneal thickness (~50 µm). Type: Non-keratinized stratified squamous e...
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sclera

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sclera  The sclera is the white, opaque outer coat of the eyeball – often called the "white of the eye." It is strong and protective, giving the eye its shape. 🔹 Key Features of the Sclera Location : Forms the posterior 5/6 of the eyeball’s outer coat , continuous in front with the cornea and behind with the dura mater of the optic nerve . Structure : Dense connective tissue (mainly collagen & elastic fibers). Avascular (no blood vessels), which makes it appear white. Covered by episclera (outer connective tissue layer) and conjunctiva . Thickness : Thickest near the posterior pole (~1 mm). Thinnest just behind the rectus muscle insertions (~0.3 mm). Openings : Anterior scleral foramina → for cornea. Posterior scleral foramina → for optic nerve fibers. Numerous small channels for nerves & blood vessels. 🔹 Functions Maintains the shape of the eyeball. Provides attachment for extraocular muscles. Protects the delicate...
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BINOCULAR VISION

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  BINOCULAR VISION BINOCULAR VISION AND SPACE PERCEPTION Slide 1 Location: Position of an object in physical (objective) space Localization: Position of the object in visual (subjective) space Retinal elements/points/ Areas: The retinocerebral apparatus engaged in elaborating a sensation in response to the excitation of a unit area of the retinal surface Slide 2 Relative subjective visual direction  ( BINOCULAR VISION ) Each retinal element localizes the stimulus as a visual percept in a specific visual direction relative to the  visual direction  of the fovea Slide 3-5 Retinomotor values It is the degree of movement of the eye to get fixation at the fovea Slide 6-7 Common relative subjective visual direction All object points that simultaneously stimulate the two fovea appear in one and the same subjective visual direction i.e not in the direction of the principal line of direction of either eye but in a direction coinciding with the medial plane of the head Slide 8...
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Embryology of the Eye 🧬👁️

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  Embryology of the Eye 🧬👁️ The eye develops from three embryonic sources : Neuroectoderm of forebrain (diencephalon) → retina, optic nerve, ciliary body epithelium, iris epithelium. Surface ectoderm → lens, corneal epithelium, conjunctival epithelium, lacrimal gland. Mesoderm & Neural crest cells → sclera, corneal stroma & endothelium, choroid, iris stroma, extraocular muscles, parts of orbit. Developmental stages: Optic vesicle (outpouching of forebrain neuroectoderm). Invagination → optic cup (double-walled). Outer layer → Retinal pigment epithelium (RPE). Inner layer → Neural retina. Lens vesicle develops from surface ectoderm (induced by optic vesicle). Mesenchyme around optic cup → choroid, sclera, cornea (stroma & endothelium). Choroidal fissure closes → optic nerve forms. Eyelids & lacrimal apparatus develop from surface ectoderm. ⚠️ Clinical relevance: Failure of choroidal fissure closure → coloboma . Abn...
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