A study of the central and peripheral refractive power of the cornea with orthokeratology treatment

The central and peripheral refracting power of the cornea after orthokeratology treatment was studied by a cross-sectional method. Three Asian subject groups were recruited. Group 1 consisted of 31 normal non-contact lens wearers, group 2 consisted of 14 subjects who wore orthoK contact lenses for 10-20 months, and group 3 consisted of 14 subjects who wore orthoK contact lenses for more than 20 months. Our results showed that the corneal refracting power (central 3.3 mm) in both of the groups with orthoK contact lens treatment did not differ significantly from the average cornea. The group that wore orthoK lenses for more than 20 months had a flatter temporal peripheral cornea than did the normal group at approximately 2.95 mm from the corneal apex. Because the temporal cornea is steeper than the nasal cornea in normal eyes, a relatively flatter temporal cornea in the orthoK group produces a more symmetrical peripheral cornea.