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Editors Selection IGR 7-3
Visual function
Comment by Balwantray Chauhan on:
11680 Effect of cataract surgery with intraocular lens implant on frequency doubling perimetry, Arvind H; George R; Baskaran M et al., Current Eye Research, 2005; 30: 123-128
The effects of cataract are important in the evaluation of the visual field. This issue is perhaps more critical in the evaluation of glaucomatous visual fields as segregating defects due to glaucoma from those due to cataract is not always easy. Ideally, perimetric tests used for screening for glaucomatous visual field defects should be minimally influenced by the effects of cataract. Frequency doubling technology (FDT) perimetry is a test commonly used for glaucoma screening. The screening mode of the FDT requires approximately a minute, while the threshold test requires five to six minutes. The new generation of FDT (Matrix perimetry) requires approximately the same time. Arvind et al. (124) studied the change in visual field appearance in 54 healthy subjects before and after cataract surgery with both the screening and threshold versions of FDT. The screening test resulted in a significant increase in visual field sensitivity using three different semi-quantitative grading schemes. The threshold test resulted in a change in mean deviation from -5.23 dB to -2.94 dB, however the pattern standard deviation changed very little (from 5.15 dB to 5.21 dB). While the improvement in mean deviation was statistically significant, it was surprising to find a post-surgical value that is substantially worse than that published for a normal population. The authors were careful to grade the cataracts using the Lens Opacities Classification System II (LOCS II); however, it is a pity that they did not perform a sub-analysis to show whether nuclear cataract or sub-capsular cataract had a more profound effect on the visual field. Also omitted was the relationship between change in visual acuity and change in the FDT measured visual field. The authors contend that because cataract did not affect the PSD, this index should have a reduced impact on the evaluation of glaucomatous visual fields. Further studies from this group and others on the effect of cataract on FDT fields in patients with coexisting glaucoma are now warranted.
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