Purpose: We investigated the extent of corneal displacement and factors associated with the measurement of IOP during the early and late phases of noncontact tonometry.
Methods: One eye in each of 61 healthy volunteers was studied. In each case, the cornea was photographed in profile using a high-speed camera during noncontact tonometry. The extent of displacement at the corneal center, and at the midperipheral corneal areas at 13.2 and 30.0 ms after the application of an air puff was recorded. For each measurement point, multiple regression analyses were performed against age, sex, axial length, corneal curvature, IOP, and central corneal thickness (CCT) to determine the independent predictors of corneal displacement. Multiple comparison tests were used to determine whether the displacement differences were associated with age or sex.
Results: Our results showed that the factors most associated with corneal displacement were the IOP (P < 0.001) and CCT (P = 0.02) at the corneal center at 13.2 ms, the CCT (P = 0.041) at the corneal midperiphery at 13.2 ms, age (P < 0.01) at the corneal center at 30.0 ms, and age (P = 0.04) and IOP (P = 0.04) at the corneal midperiphery at 30.0 ms. Young females had the smallest amounts of corneal displacement at all measurement points, and elderly females had largest amounts of displacement at the late phase of tonometry.
Conclusions: The amount of corneal displacement is affected by an individual's IOP, age, and CCT. Our findings indicated that the corneas of females may be more susceptible to aging than those of males.