Clinical comparison of the SITE IRAS hand-held interferometer and Haag-Streit Lotmar visometer

Clinician versus potential acuity test predictions of visual outcome after cataract surgery

BACKGROUND

The aim of this study was to compare the ability of potential vision tests and clinical judgement to predict postoperative visual acuity after uneventful cataract surgery.

METHODS

Sixty-two subjects (median, 74.5 years) were included in the study. Preoperative measurements included a clinical judgement prediction (based on case history and ocular examination alone), 2 super-illuminated pinhole techniques (distance and near), Potential Acuity Meter and interferometer. Postoperative visual acuity was used as the outcome measure to evaluate the accuracy of the preoperative predictions.

RESULTS

Subjects were categorized as follows: (a) moderate cataract (N = 25); (b) moderate cataract and comorbidity (N = 18), and (c) advanced cataract (N = 19). Preoperative predictions within 2 lines of the postoperative visual acuity were as follows (a, b, and c respectively): clinical judgement (92%, 72%, 58%), super-illuminated pinhole distance (96%, 100%, 21%), super-illuminated pinhole near (92%, 78%, 26%), Potential Acuity Meter (72%, 67%, 21%), and interferometer (56%, 61%, 37%).

CONCLUSIONS

Based on the preoperative predictions above, none of the potential vision tests was useful compared with the clinical judgement in the advanced cataract group. The super-illuminated pinhole (distance) provided additional information beyond clinical judgement in the moderate cataract subgroup. The Potential Acuity Meter and interferometer were inaccurate even in the presence of moderate cataract, and this and other recent findings suggest they should no longer be considered adequate for potential vision assessment.

Capabilities of potential vision test measurements

PURPOSE

To determine the usefulness of a battery of potential vision tests (PVTs) including potential acuity meter (PAM), laser interferometer (LI), critical flicker/fusion frequency (CFF), superilluminated pinhole at distance (SPH(d)) and near (SPH(n)), and optimal reading speed (ORS) by their independence of the effects of cataracts and sensitivity to macular disease (MD).

SETTING

Department of Optometry, University of Bradford, Bradford and Leeds General Infirmary, Leeds, United Kingdom.

METHODS

Potential vision test measurements were determined in 76 patients with age-related cataract and no other eye disease, 52 patients with MD and clear ocular media, and 28 patients with normal, healthy eyes.

RESULTS

Potential vision tests were independent of the degrading effects of cataract up to a visual acuity (VA) level of 20/200 or worse (CFF), 20/125 (ORS and SPH), and 20/40 (PAM and LI). A high degree of association was found between PVT scores and distance VA in the MD group for SPH(d) (r2 = 0.93), SPH(n) (r2 = 0.89), and PAM (r2 = 0.71). A moderate correlation was found for LI (r2 = 0.55), CFF (r2 = 0.50), and ORS (r2 = 0.45).

CONCLUSIONS

Potential acuity meter and LI showed very limited independence to moderate/dense cataracts and inaccurate predictions in patients with MD. Superilluminated pinhole was relatively unaffected by moderate/dense cataract and yet provided accurate predictions in the presence of MD and clear ocular media. Critical flicker/fusion frequency showed the greatest ability to bypass cataracts, although its ability to predict VA in patients with early MD was limited. The ORS was relatively unaffected by moderate/dense cataract, but its poor ability to predict VA in MD may limit its clinical suitability as a PVT.

Accuracy of IRAS GT interferometer and potential acuity meter prediction of visual acuity after phacoemulsification: prospective comparative study

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.