Change in effective power of posterior chamber lenses placed with the plano surface anterior.

Posterior chamber lenses were inserted with the plano surface anterior because of theoretical optical improvements in spherical and chromatic aberration, less induced magnification, and a reported decrease in late opacification of the posterior capsule. A decrease in effective lens power occurred, with a shift in observed refraction of approximately + 1.50 diopters (D) from that calculated. This finding is explained by the location of the principal planes of a plano-convex lens. Orienting the plano surface anteriorly causes an observed increase in required anterior chamber depth (ACD) calculation that averages 1.1 mm. Required ACD using the Binkhorst formula was 5.1 mm; the Sanders-Retzlaff-Kraff (SRK) A constant required was 118.7. The need for secondary capsulotomy has been only 5.8% with an average follow-up of 19 months and a range of 12-27 months.