Abstract
Purpose: :
The ability to test vision under different contrast and luminance conditions that simulate normal life activities has traditionally been difficult in clinical practice requiring the use of different testing charts, illumination techniques and other factors. The purpose of our study is to evaluate the use of a computerized test of visual acuity, the Vimetrics Central Vision Analyzer (CVA), to quantify mesopic and glare conditions in normal eyes and eyes with macular disease.
Methods: :
A consecutive series of 250 normal and diseased eyes were studied. All patients had been consented for IRB approved, non-invasive vision testing, underwent standardized ETDRS testing and full ophthalmic examinations. Patients with retinal disease also had clinically indicated fluorescein angiography and SD OCT scanning to define macular disease. CVA testing was performed for each eye twice to determine reproducibility on the same day. This is a computerized test using a vision testing algorithm under standardized illumination with a calibrated monitor. The patient uses a joystick to self administer the test. Landoldt C targets are used at various degrees of contrast as well as under computer generated glare conditions. Diagnosis was determined by a clinician independent of knowledge of the vision testing. Patients were tested on the CVA instrument at 100%, 64% and 43% contrast as well as under two glare conditions G2= 10% contrast with 80% off axis (vertical) source of light and G3= 8% contrast and 15 degree off axis (retro-illumination) conditions.
Results: :
Reproducibility of the device was high. In diseased eyes with Epiretinal membrane, Dry AMD and Wet AMD the concordance correlation (CCC) was between 0.82 and 0.90. This was modestly higher than in normal acuity eyes. These CCC were all significant ( p between 0.03 and 0.001). Plots of ETDRS equivalent log MAR acuities under all five contrast conditions showed a decline in visual acuity as contrast lowered and then further under additional glare / photo-stress conditions. The slope of the curve (worsening acuity with decreased contrast and additional photostress) was higher in eyes with macular disease than in control non diseased eyes by 50%.
Conclusions: :
Vimetrics Central Vision Analyzer objectively measures mesopic and photopic acuities with high reproducibility. Such testing offers insight into the correlation between macular structure and function. Further improvements in testing algorithms are under way.
Keywords: retina • visual acuity • age-related macular degeneration