Corneal topography for intraocular lens power calculations.

BACKGROUND: In patients undergoing cataract extraction with PC IOL insertion, pre-op and post-op corneal power measurement is necessary to calculate induced astigmatism. In cases with irregular corneal astigmatism, measurements with traditional keratometry is inaccurate. We report the use of video keratography in three cases that required keratometry readings in order to calculate IOL power. These cases were characterized by irregular or incomplete keratometer mires, so quantitative descriptors derived from computer-assisted corneal topography (TMS-1) were used instead.

CONCLUSION: The standard keratometer is useless in cases in which the mires appear irregular or incomplete. In such cases, computer-assisted corneal topography can be used successfully. Recently, a new corneal topography index has been developed, the average corneal power, which is a measure of the average corneal power within the entrance pupil. We are currently evaluating the use of average corneal power to assist in the calculation of IOL powers.