Accuracy of IRAS GT interferometer and potential acuity meter prediction of visual acuity after phacoemulsification

Prospective comparative study

Abstract

Purpose: 

To assess and compare the accuracy of 2 methods of predicting visual acuity after phacoemulsification.

Setting: 

Department of Ophthalmology, Montpellier, France.

Methods: 

This prospective study evaluated 47 eyes of 47 patients having uneventful phacoemulsification over a 1-month period. All the patients had mild to moderate cataract. Visual acuity recovery was predicted using the white-light IRAS GT® interferometer on the 3- and 8-degree wide test area and the Guyton-Minkowski potential acuity meter (PAM). Best corrected visual acuity was evaluated 1 day before and 1 month after surgery.

Results: 

Both the interferometer and PAM underestimated the retinal visual capacity. Three-degree white-light interferometry gave significantly better mean predicted results than 8-degree interferometry and the PAM. There was no statistically significant disparity between predicted and postoperative results with 3-degree interferometry (1.04 ± 0.57 logMAR; −0.09 ± 0.27 decimal) (P = .0647) and a statistically significant disparity with 8-degree interferometry (0.89 ± 0.59 logMAR; −0.13 ± 0.27 decimal) and the PAM (0.66 ± 0.62 logMAR; −0.22 ± 0.24 decimal) (P = .0001). The predicted values were widely dispersed; the correlation indices were 0.38 with the PAM (P = .091), 0.39 with 3-degree interferometry (P = .001), and 0.49 with 8-degree interferometry (P = .0005).

Conclusions: 

Three-degree white-light interferometry gave more accurate results than 8-degree interferometry and the PAM. The wide dispersion of results and unsatisfactory correlation indices show the tests are poor predictors of individual acuity. They should be used semiquantitatively and the results interpreted in relation to the clinical data. Qualitative methods may be useful in confirming or refuting visual recovery capacity ascertained by quantitative systems.