Measured and predicted anterior chamber depth for transscleral suture-fixated posterior chamber intraocular lenses

Variables in intraocular lens (IOL) power calculations include axial length, average dioptric power of the cornea, and an assumed pseudophakic anterior chamber depth (ACD). In the case of transscleral suture-fixated posterior chamber (PC) IOLs, ACD depends on the placement of the suture and thus might be expected to vary more than it does in eyes with capsular-fixated IOLs. To assess the degree of this variation, we determined the postoperative pseudophakic ACD using A-scan ultrasonography in 15 patients with transscleral suture-fixated PC-IOLs. The mean pseudophakic ACD (posterior corneal vertex to anterior pseudophakos) was 3.47 +/- 0.69 mm. The mean absolute discrepancies in ACD between these measured values and those predicted by the original Binkhorst and the most recent Holladay formulas were 0.579 +/- 0.513 mm and 0.639 +/- 0.519 mm, respectively. In 11 of 15 eyes, the measured ACD was within 1 mm of that predicted by either the Binkhorst or Holladay formula, suggesting that either will provide reasonable estimates of ACD for IOL power calculations for suture-fixated PC-IOLs.