Eye and Vision Revision Sheet

1. 📌 Essentials

• The eye is a sensory organ responsible for image formation, contrast, luminosity, and color perception.
• Located in the anterior and posterior segments of the eyeball.
• Main structures: cornea, aqueous humor, pupil, lens (cristallin), vitreous body, retina, fovea.
• Light passes through cornea → pupil → lens vitreous humor → retina.
• Visual pigments: cones (color) and rods (luminosity/contrast).
• Max light sensitivity at 550 nm (green light).
• Pupil diameter from 2-8 mm depending on illumination.
• Emmetropic eye: far point at infinity, near point ~25 cm.
• Common defects: myopia, hypermetropia, astigmatism, presbyopia.
• Corrective lenses: diverging (myopia), converging (hypermetropia), toric (astigmatism), progressive (presbyopia).

2. 🧩 Key Structures & Components

• Cornea — primary refractive surface, contributes ~70% of focusing power.
• Aqueous humor — transparent fluid, maintains intraocular pressure.
• Pupil — adjustable aperture controlling light entry.
• Cristallin (lens) — fine-tunes focus; flexible for accommodation.
• Vitreous body — gel-like substance maintaining eye shape.
• Retina — light-sensitive layer; contains photoreceptors.
• Fovea — central retina region with high cone density for sharp vision.
• Optic nerve — transmits visual signals to the brain.
• Visual pigments — opsins in cones (color) and rods (luminosity).

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