ANATOMY AND PHYSIOLOGY THE EYE ANATOMY AND PHYSIOLOGY

MAJOR PARTS OF THE EYE The OUTSIDE EYELID EYELASHES CONJUNCTIVA IRIS CORNEA SCLERA EYE MUSCLES The INSIDE AQUEOUS HUMOUR LENS (PUPIL) CHOROID RETINA – RODS / CONES VITREOUS HUMOUR FOVEA OPTIC NERVE

MUSCLES OF THE EYE

The Lens Elastic, circular, biconvex, transparent Held in place by suspensory ligaments It is enclosed in transparent capsule Unique ability – vary its refractive power, by changing its thickness Ciliary muscle contracts, moves forward, making lens thicker as it releases tension.

HOW THE EYE SEES

Liquid light Vitreous humour – Posterior segment Aqueous humour – is in the anterior and posterior chambers – in the Anterior Segment Divided by Iris Secreted by Ciliary glands - continous Passes in front of lens Return via Canal of Schlemm IO pressure -10-20mmHg Vitreous humour – Posterior segment 99%water, rest salts and mucoprotien Maintains pressure to support retina Maintains shape of eye Constant through life

The Retina Innermost layer Made of various light sensitive layers Rods (contrast or night vision) – Rhodopsin (needs Vit A) Cones (colour vision) Fovea – centre – only cones Optic nerve – convergence of all the nerve fibres

LACHRYMAL GLANDS AND DUCTS

FOODS THAT HELP Carrots and other orange foods- beta carotene, vit A Leafy greens - lutein and zeaxanthin—antioxidants that, studies show, lower the risk of developing macular degeneration and cataracts. Eggs – zinc and antioxidants Berries and citrus fruit – vitamin C Almonds- Vitamin E Fatty Fish - Tuna, salmon, mackerel, anchovies and trout are rich in DHA, a fatty acid found in your retina—low levels of which have been linked to dry eye syndrome

DISORDERS OF THE EYE TRAUMA – blunt, scratch, pierce VASCULAR – ischemia & haemorrhage INFLAMMATORY – conjunctivitis, scleritis, iritis, keratitis CATARACT & GLAUCOMA

SYSTEMIC DISORDERS DIABETES HYPERTENSION THYROID DISORDERS