Avaliação da função visual de sensibilidade ao contraste: estudo comparativo entre um novo teste e um teste padrão

Abstract

Introduction: Contrast sensitivity is one of the most important visual functions and reflects functional vision, which is related to the ability to perform everyday tasks. Its assessment can help detecting and following numerous eye diseases, as well as indicating and evaluating the outcome of various ophthalmic treatments.

Purpose: To evaluate visual contrast sensitivity of a normal population and patients with keratoconus or post refractive surgery by a novel contrast sensitivity chart, the first printed grating contrast sensitivity test for near, in comparison with a standard contrast sensitivity test, Optec 6500®.

Methods: Two hundred eyes with normal contrast sensitivity (group 1) and 113 eyes previously submitted to refractive surgery or with incipient keratoconus (group 2) were evaluated. All patients underwent both tests, with the same examiner, on the same day ("test") and two weeks later ("retest"). The agreement between the new test and the standard test, the agreement between "test" and "retest" of both tests and the acuity measurements of both tests were measured (p <0.05).

Results: In the standard test, 27.0% of group 1 patients were classified below the normality curve in the spatial frequency of 1.5 cpd ("floor effect"). As the normality curve of the standard test did not apply to group 1, a new curve was defined for this population based on 5th and 95th percentiles. A learning effect was observed between "test" and "retest" in both tests. Considering the agreement between "test" and "retest" of both tests, there was a good agreement only in the spatial frequency of 6.0 cpd of the standard test (K = 0.66). Evaluating the agreement between the new test and the standard test, there was a good agreement only in spatial frequency of 12.0 cpd (K = 0.64) when both groups were considered together.

Conclusions: There was a moderate agreement between the new test and the standard contrast sensitivity test. Both tests showed low test-retest reproducibility. A learning effect was observed between "test" and "retest" with both tests. The contrast sensitivity curve obtained with the standard test appears to differ in distinct populations. The new test proved useful for assessing contrast sensitivity visual function but still needs to be improved.