What are the classifications of hyperopia?

Hyperopia can be divided into three types: axial hyperopia, curvature hyperopia, and refractive index hyperopia.

1. Axial Hyperopia: A short ocular axis is referred to as axial hyperopia. The change in the ocular axis of the human eye is generally not significant, usually not exceeding 2mm, which corresponds to a 6 diopter (D) change, with each 1mm representing a 3D change. Occasionally, there is high hyperopia, reaching 24D under pathological conditions, such as congenital microphthalmos or orbital tumors, orbital inflammatory masses, and retinal detachment, which can shorten the anteroposterior axis of the eye.

2. Curvature Hyperopia: A smaller surface curvature of the refractive media is referred to as curvature hyperopia. Changes in curvature can occur in the cornea and lens, particularly in the cornea. An increase in the corneal radius of curvature by 1mm results in 6D of hyperopia. In this type of curvature hyperopia, there is almost always astigmatism because the cornea rarely remains spherical. Common causes include congenital flat cornea and corneal diseases or injuries.

3. Refractive Index Hyperopia: A weakened refractive effect of the lens is referred to as refractive index hyperopia. This change is observed in physiological changes in the elderly and pathological changes caused by diabetes treatment. Posterior dislocation of the lens and lens deficiency can also lead to hyperopia.