Question

Describe the function of two non-neural optical structures of the visual system. Also, describe resulting visual impairments if each of these structures is damaged.

Answer 1

Answer :

visual system is part of central nervous system , which give organism ability to process visual details as sight.

This system consist of eyes, optic nerve , optic chiasma, optic tract, lateral geniculate nucleus, optic radiation, visual cortex and visual association cortex.

Light travels from atmosphere to inside of eyes through cornea, anterior chamber, pupil, lens, posterior chamber, retina, optic nerve.

No-neuronal optical structures of visual systems include cornea, anterior chamber, pupil, lens, posterior chamber.

Cornea acts as eyes outer most lens. It controlls and focuses the entry of light into the eyes.

It contributes 65 to 75 % of the eyes total focussing power.

It is a transparent part of eye, covers the pupil, iris and anterior chamber. Cornea helps to refract light.

cornea consists of non keratinized squamous epithelium. normal corneal thickness is 510 to 520 micrones.

normal functioning of cornea is important for normal visual system

so many diseases afffects cornea and these afffects vision.

examples - CORNEAL OPACITY - here cornea became scared, it occur in vit A deficiency , side effects of drugs like amiodarone.... it will prevents lights to enter inside eyes .

ASTIGMATISM - this is another common reason affecting vision. here the cornea have irregular curve , which affects the refractory power of cornea and causes blurry , distortrd vision

KERATITIS

-FUCHS  ENDOTHELIAL DYSTROPHY

another important non neuronal structure in visual system is lens . it is transparent , biconvex

this also helps to refract light to be focused on retina.

by changing the shape of lens with the helps of accessory muscles , it can focus on objects at various distance. this adjustment is known as accommodation.

refractory power of lens in its natural enviornment is 18 diopter.

anterior surfuce of lens is less curved than posterior. adult lens has 10 mm diameter and 4 mm axial length.

lens lack blood vessels , nerves . lens capsule is mainly made up of type 4 collagen tissues.

lens epithelium is simple cuboidal epithelium, regulate homeostasis of lens.

various diseases affects lens functions

example

CATARACTS - these are opacity of lens . usually develop as a aging process , but also occurs congrenitaly . nuclear sclerosis is type of age related catract. diabetes, trauma , medications , uvlight exposure iare another risk factor for catracts.

surical removal of diseased lens and replaced with artificial lens is treatment ootion.

PRESBYOPIA- this also age related problem . here accomodation is affected, so that eye cannot focus nearby objects.

APHAKIA - it is the condition of absence of lens. occur either congenitaly , traumaticaly , surgicaly