Biometry of 7,500 Cataractous Eyes

Abstract

This biometric analysis of 7,500 eyes of cataract patients gave a mean axial length of 23.65 mm, a mean average keratometric value of 43.81 diopters, a mean preoperative anterior chamber depth of 3.24 mm, and a mean central endothelial cell count of 2,470 cells/mm2. There is a statistically significant but clinically insignificant 0.16-diopter flattening of the cornea after cataract surgery without an intraocular lens, but none with an intraocular lens. Pseudophakic eyes do not show a clinically significant increase in corneal flattening over aphakic eyes. Anterior chamber depth increases from 3.24 mm to 3.32 mm (±0.08) in pseudophakic eyes and to 3.67 mm (±0.43) in aphakic eyes. Astigmatism averaged 1.0 diopter in phakic eyes preoperatively, showing a mean increase of only 0.5 diopter in aphakic eyes and 0.65 diopter in pseudophakic eyes. One third of the eyes in this series had axial myopia while slightly less than half had axial hyperopia; the remaining 20% were in the emmetropic range. Preoperative anterior chamber depths were lowest in eyes with short axial lengths and increased with axial length. However, deep (6 mm) and shallow (2 mm) anterior chamber depths were encountered in all three groups. Shorter eyes had steeper corneas than emmetropic eyes by less than 1.0 diopter while myopic eyes had weaker corneas than emmetropic eyes by about 0.5 diopter. Astigmatism was essentially the same in all three groups (1.0 diopter) except that emmetropic eyes showed a small (0.08 diopter) but statistically significant decrease in cylinder from the other groups, as well as a smaller range (6.3 vs. 9.5 diopters). There is a very small but extremely significant increase in endothelial cell count from hyperopic to myopic eyes. There is little correlation between fellow eyes for axial length, average keratometric value, or anterior chamber depth, indicating the need for bilateral examination in calculating intraocular lens power. All other possible correlations of these data were not statistically significant. This biometric analysis of 7,500 eyes of cataract patients gave a mean axial length of 23.65 mm, a mean average keratometric value of 43.81 diopters, a mean preoperative anterior chamber depth of 3.24 mm, and a mean central endothelial cell count of 2,470 cells/mm2. There is a statistically significant but clinically insignificant 0.16-diopter flattening of the cornea after cataract surgery without an intraocular lens, but none with an intraocular lens. Pseudophakic eyes do not show a clinically significant increase in corneal flattening over aphakic eyes. Anterior chamber depth increases from 3.24 mm to 3.32 mm (±0.08) in pseudophakic eyes and to 3.67 mm (±0.43) in aphakic eyes. Astigmatism averaged 1.0 diopter in phakic eyes preoperatively, showing a mean increase of only 0.5 diopter in aphakic eyes and 0.65 diopter in pseudophakic eyes. One third of the eyes in this series had axial myopia while slightly less than half had axial hyperopia; the remaining 20% were in the emmetropic range. Preoperative anterior chamber depths were lowest in eyes with short axial lengths and increased with axial length. However, deep (6 mm) and shallow (2 mm) anterior chamber depths were encountered in all three groups. Shorter eyes had steeper corneas than emmetropic eyes by less than 1.0 diopter while myopic eyes had weaker corneas than emmetropic eyes by about 0.5 diopter. Astigmatism was essentially the same in all three groups (1.0 diopter) except that emmetropic eyes showed a small (0.08 diopter) but statistically significant decrease in cylinder from the other groups, as well as a smaller range (6.3 vs. 9.5 diopters). There is a very small but extremely significant increase in endothelial cell count from hyperopic to myopic eyes. There is little correlation between fellow eyes for axial length, average keratometric value, or anterior chamber depth, indicating the need for bilateral examination in calculating intraocular lens power. All other possible correlations of these data were not statistically significant.