Refractive Errors, Colour Vision Issues and Visual Defects

Question 1

Types of refractive error

Management

Answer 1

Emmetropia - normal vision

Myopia (short sighted) - light focuses on area infront of retina

• elongation of eyeball often happens during childhood as skull grows
• concave lens needed

Hyperopia (long sighted)
-convex lens needed

Question 2

Colour blindness

-pathogenesis, some types and epidemiology

Answer 2

R and G pigments on X chromosome

Men more likely to lack pigment

Anomalous trichromat - 1 pigment is altered
Dichromats - lack either R or G
Monochromats - lack 2 pigments
Achromatopsia - no cones

Question 3

Describe the visual defect if you have damage at the level of the

• left retina,
• left optic nerve
• midline optic chiasm
• left lateral optic chiasm
• left optic tract
• left Meyer’s loop
• left Baum’s loop
• left striate cortex

Answer 3

Left retina => scotoma (loss of vision in part of your visual field)
Left optic nerve => blind in L eye
Midline optic chiasm => bitemporal hemianopia
Left lateral optic chiasm => left nasal hemianopia
Left optic tract => right homonymous hemianopia
Left Meyer’s loop => right superior quadrantopia
Left striate cortex => right homonymous hemianopia with macular sparing