12 - Opth - Refractive Error - Hypermetropia, Astigmatism, Presbyopia

Question 1

What is hypermetropia

Answer 1

long sightedness

Question 2

what happens in hypermetropia + why

Answer 2

light focused behind retina due to

• refractive power too weak (<60) - cornea/lens too flat)
• axial hypermetropia (eye too short <22.22m)

Question 3

possible cause + associated ocular conditions - hypermetropia

Answer 3

usually genetic component

• Acute angle closure glaucoma
• squint
• amblyopia

Question 4

What may compensate hypermetropia - what can this lead to

Answer 4

partial compensation with accommodation - tiredness of gaze, headaches and convergent squint in children

Question 5

how to correct hypermetropia

Answer 5

corrected by convergent (convex) lens (+ve prescription)

Question 6

Astigmatism - cause + effect

Answer 6

by cornea or lens lacking regular curvature in all directions - light rays lack a single point of focus

Question 7

How to correct Astigmatism

Answer 7

with cylindrical lens - along with correcting main refractive error

Question 8

Presbyopia - when? what happens? reduces what?

Answer 8

in old age - starts at 40y and ends by 60y

- progressive sclerosis of lens - reduces accommodative ability

Question 9

define presbyopia

Answer 9

age related impaired accommodation and near vision

Question 10

how to correct presbyopia

Answer 10

correct with convex lens (+ve prescription)