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Ocular anatomy
Neuro-Ophthalmology
Key Points
- •The globe has 3 coats: fibrous (cornea + sclera), vascular (iris + ciliary body + choroid), and neural (retina) - AP length ~24 mm, volume ~6.5 mL, total refractive power ~+60 D (cornea +43 D, lens +15–20 D)
- •The retina has 10 layers (ILM to RPE): inner retina (layers 1–6) supplied by CRA; outer retina (layers 7–10) supplied by choroid - dual supply explains cherry-red spot in CRAO and photoreceptor viability in inner retinal ischaemia
- •The orbit is formed by 7 bones; medial wall (lamina papyracea) is thinnest; the annulus of Zinn gives origin to all EOMs except the inferior oblique (from orbital floor); Spiral of Tillaux: MR 5.5, IR 6.5, LR 6.9, SR 7.7 mm from limbus
- •Anterior ciliary arteries (7 total: 2 from each rectus except 1 from LR) + long posterior ciliary arteries form the major arterial circle of the iris - detaching >2 recti risks anterior segment ischaemia
- •The fovea contains only photoreceptors and outer retinal layers (no inner retina, no retinal vessels) - explains the foveal avascular zone, the cherry-red spot in CRAO, and why foveal vision depends entirely on choroidal circulation
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12 more sections are included with the Clinical plan.
- Definition
- Epidemiology
- Aetiology and causes
- Pathogenesis
- Classification
- Clinical features