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18 Cards in this Set
- Front
- Back
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What layers are there in the tear film? And what are they produced by? |
- Mucoid layer, produced by goblet cells in conjunctival epithelium - Aqueous layer, produced by lacrimal glands - Lipid layer, produced by meibomian glands of the eyelid margins |
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What muscle closes the eyelid and what is its nerve supply? |
Orbicularis oculi, CNVII |
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What muscle opens the eyelid and what is its nerve supply? |
Levator palpebrae, CNIII |
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What anatomical factors contribute to corneal transparency? |
- Absence of keratinisation of epithelium - Tight packing of epithelial cells - Mucous layer (smooth surface) - Regular arrangement of corneal lamellae - Absence of blood vessels |
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What physiological factor contributes to corneal transparency? |
Dehydration of the cornea through Na+/HCO3- pump in corneal endothelium |
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Where is aqueous humour produced? |
Ciliary processes in posterior chamber |
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How does aqueous humour drain? |
Enters anterior chamber, circulates, drains through the trabecular meshwork into the canal of Schlemm, aqueous veins and conjunctival episceral veins |
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What % of the lens is water and what % is protein? |
65% water, 35% protein |
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What happens when the ciliary mm contracts? |
Zonular fibres relax, lens becomes more globular, refractive power increased |
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What is the function of cones? |
Acute vision and colour vision |
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What is the function of rods? |
Vision in poor light and wide field of vision |
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An afferent pupillary defect implies a problem in which nerve? |
Optic nerve |
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An efferent pupillary defect implies a problem in which nerve? |
Occulomotor nerve |
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If anisocoria is worse in bright light, the fault lies with which mechanism? |
Constrictor mechanism e.g. III nerve palsy |
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If anisocoria is worse in dim light, the fault lies with which mechanism? |
Dilator mechanism e.g. Horner's syndrome |
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What is the refractive power of the cornea and the lens? |
Cornea= 40D Lens= 20D |
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In axial myopia, the eye is too long/short. Light is focused in front of/behind the retina and is corrected with divergent/convergent lenses? |
Long, in front of, divergent |
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In axial hypermetropia, the eye is too long/short. Light is focused in front of/behind the retina and is corrected with divergent/convergent lenses? |
Short, behind, convergent |
