1 - Opth - Introduction and Anatomy - Outer Layer Flashcards
Eye can be divided clinically into …
anterior portion - ant to and including lens
posterior portion - post to lens
Sclera - what? blood supply? corneal junction? What is the Lamina Cribrosa?
bundles of interlaced collagen fibres
relatively avascular
continuous with cornea at LIMBUS
LC - hole in sclera that optic nerve passes through
Cornea - purpose? describe surface? how many layers?
refraction - 75% refractive power
smooth regular surface
5 distinct layers
Name the 5 layers of Cornea from external to internal - give salient features
1 epithelium 2 bowmans membrane 3 stroma - 90% of thickness 4 descemet's membrane 5 endothelium - single layer of flat cells - removes water from the stroma
Name the 3 layers of the tear film + where they are + function
oily layer - superficial - maintain tear film, prevent evaporation
aqueous layer - electrolytes, proteins, lysozymes, IG, glucose, dissolved O2
mucoid layer - deep - helps wetting properties of tears
Lacrimal Apparatus - where is main lacrimal gland + what is it supplied by
supratemporal part of orbit
supply - parasympth fibres from greater petrosal nerve of facial nerve
Lacrimal apparatus - drainage route?
sup+inf puncta+canaliculi>lacrimal sac>nasolacrimal duct>inferior meatus
Where are the anterior and posterior chambers? what are they filled with? function of this?
ant - directly post to cornea and anterior to iris
post - between lens and iris, triangular shape
aqueous humor - provides nutrients to avascular cornea and lens + maintains ocular pressure
Aqueous humor - composition? route?
similar to tissue fluid (but less glucose and low protein)
- secreted into post chamber byciliary body > into ant chamber through pupil > drains into canal Schlemm via trabecular meshwork
Lens - refractive power? thickness? blood supply? make up?
25% of refractive power
5mm thick - increases with age
supply - avascular - supplied by aqueous
2/3 water, 1/3 protein
