Refractive outcomes in anterior chamber intraocular lenses

Abstract

To the Editor,The 2008 United Kingdom Royal College of Oph-thalmologists’ (RCOphth) Cataract Surgery Guide-lines included, for the first time, a biometricbenchmark of achieving a final spherical equivalent(SE) within ±1 dioptre (D) of the target in 85 % ofcases [1]. This was based on a prospective analysis of4,806 eyes with in-the-bag lens implantation, with83.4 and 53.6 % within ±1 and ±0.5 D of predictedSE, respectively [2].We retrospectively applied this benchmark to anauditofrefractiveoutcomesforanteriorchamberlenses(ACIOL). Data were available in 52 eyes implantedwith 122UV lenses (Bausch & Lomb Inc., New York,NY,USA),a polymethylmethacrylate open-loop angle-supported design available in two lengths: 12.5 mm(S122UV) and 13.75 mm (L122UV). The manufac-turer’s A-constant of 115.8 was used in all cases.Subjective refractions were performed in 41 (79 %) of52 eyes, with the remainder by auto-refraction. Finalrefraction following suture removal revealed 71.2 %within ±1Dand40.4%within±0.5 D of target SE.Mean difference between target and achieved SE was0.37 D (range -1.77 to 2.54, SD 0.89); no differenceswere observed between refraction methods (p = 0.31,t test) or the two lens lengths (p = 0.44, t test), norwhether the lens was implanted as a primary orsecondary procedure (p = 0.41, t test). Weak correla-tion between increasing anterior chamber depth andgreater hypermetropic error was demonstrated (Pear-son’s correlation, r = 0.23). Raw data were submittedto the Users Group for Laser Interference Biometry(ULIB) website, providing an optimized A-constant of115.1 for use with the SRK/T formula (http://www.augenklinik.uni-wuerzburg.de/ulib/c1.htm).Comparative published outcomes predominantlyinvolve extracapsular extractions, although none pro-vide SE outcomes in the same RCOphth format:98 % ± 3D[3], 86 % ± 2D[4] and mean SE -0.73[5]. The largest series of 83 ACIOLs between 1991and 2005 (method of surgery not stated), reported amean refractive outcome of -0.8 D ± 1.67 [6].While RCOphth guidelines are not explicitly lim-ited to in-the-bag implantation, with the routine use ofoptical biometry, modern lens calculation formulaeand A-constant optimization there is no reason whyrefractive benchmarks should not be applied toanterior chamber implantation. While the inherentlimitations of this small retrospective audit areacknowledged, our data suggest that refractive out-comes with ACIOLs can be judged by the samebiometric standards.