HYPERMETROPIA (HYPEROPIA)

A i.e. Hypermetropia of 2 D

 Axial hypermetropia:

•  1-mm shortening of the anteroposterior diameter of the eye results in 3 dioptres of hypermetropia.

Curvature hypermetropia:

• 1-mm increase in radius of curvature results in 6 dioptres of hypermetropia.

Ans. 6 dioptres

Curvature hypermetropia is that condition in which curvature of the cornea, lens or both is increased (flatter) than the normal, resulting in change in refractive power of the eye. About 1 mm increase in radius of curvature results in 6 D of hypermetropia

Ans. Hypermetropia

Ans. C i.e. Hypermetropia

Ans. D: Anterior dislocation of the lens

Factors responsible for hypermetropia:

• Short axial length of the eyeball
• Curvature hypermetropia commonly occurs as a factor in astigmatism (corneal plana)
• Index hypermetropia accounts for the hypermetropia of old age due to increased refractive index of the cortex of the lens relative to the nucleus so that overall refractive power of the lens decreases.

It may be associated with diabetes, tumors, microphthalmia (a growth dysfunction during fetus development) and fovea hypoplasia, a condition that affects the blood vessels in the retina.

While these conditions may result in hypermetropia, one of the most commonly cited causes of farsightedness is considered to be aging.

Ans. is. d., 6D hypermetropia

• Change in axial length can cause refractive error.
• It is the commonest form of ametropia (both myopia and hypermetropia).
• In hypermetropia, there is an axial shortening of eyeball.
• So, image is formed behind the retina.
• In myopia, there is an axial lengthening of eyeball.
• So, image is formed in front of the retina.
• 1 mm change in axial length leads to ametropia of 3D.
• For example 1 mm shortening in axial length causes hypermetropia of 3D.