Fluctuations of Anterior Chamber Depth and Astigmatism in Pseudophakic Eyes

To explore the significance of changes in anterior chamber depth (ΔACD) and astigmatism between 4 and 8 weeks following uneventful phacoemulsification.

Anterior chamber depth (ACD, mm), autorefractometry and subjective refraction were monitored in pseudophakic eyes implanted with non-toric IOLs (group 1, SA60AT, n=36; group 2, SN60WF, n=34; group 3, ICBOO, n=16) and phakic control group (n=30, group 4a, for ACD and autorefractometry) over four weeks. Changes in subjective refractions were compared with repeatability in normal phakic eyes (n=30, group 4b).

Reporting key results (p<0.01), mean (±sd 95% CI) ΔACD values (ACD at start minus ACD at four weeks) were +0.02 (±0.37, -0.16 to 0.08), +0.22 (±0.51,0.05 to 0.39), -0.33 (±0.51, -0.58 to -0.08), -0.02 (±0.07, -0.04 to 0.01) in groups 1-4a respectively. Differences were significant (1-way ANOVA, F=7.02). Pooling data from the pseudophakic eyes (n=86) induced astigmatism (IA) by autorefractometry was significantly greater in comparison with group 4a [-0.78D (±0.67, -0.92 to -0.64) and -0.19D (±0.16, -0.25 to - 0.13)]. IA power correlated with the initial power of refractive astigmatism at 4 weeks (A), [IA = 0.36A-0.30 (r²=0.207) and IA = 0.39A-0.29 (r²=0.232) by autorefractometry and subjective refraction, respectively]. In groups 1-3, vector analysis revealed i) the change in refraction in over 55% of eyes was beyond the 95% confidence interval limits observed in groups 4a and 4b, ii) some significant associations between changes in vectors describing astigmatism with ΔACD and IOL labelled power.

Changes in ACD and refraction still occur four weeks after unremarkable phacoemulsification and the inter-relationship depends on IOL design/type. Other factors, such as tilt or dislocation of the IOL along the X-Y axes parallel to Listing's plane, accompanying changes in ACD are expected to affect the postop astigmatism.