Screening for sight-threatening diabetic retinopathy: comparison of fundus photography with automated color contrast threshold test

Abstract 

Purpose

To compare tritan contrast threshold (TCT) with fundus photography in screening for sight-threatening diabetic retinopathy (STDR), before significant visual loss.

Design

Prospective, comparative study.

Methods

A total of 510 consenting diabetic patients attending a hospital-based photographic screening clinic were recruited over a 2-year period. Exclusion criteria included visual acuity of worse than 6/9, previous photocoagulation, and a history of previous eye disease known to affect color vision. The automated TCT test was performed using a computerized cathode ray tube-based technique. Retinal photography was performed using a Polaroid mydriatic fundus camera with a 45 degrees field. Grading of diabetic retinopathy was carried out by an ophthalmologist using slit-lamp biomicroscopy and a 78-diopters lens. Assessments of sensitivity, specificity, and predictive values for both fundus photography and the TCT test were made.

Results

Both the fundus photography and TCT test correlated significantly with the presence of STDR (P < .0001, χ² test). The TCT test yielded a sensitivity of 94% (95% confidence interval [CI], 73%– 100%) and a specificity of 95% (95% CI, 92%– 96%) for detection of STDR compared with a sensitivity of 88% (95% CI, 66%–97%) and a specificity of 95% (95% CI, 93%–97%) with fundus photography. Combined modality improved overall screening performance.

Conclusion

The TCT assessment is an effective and clinically viable technique, in comparison with fundus photography, to screen for STDR among a diabetic population. Additionally, our results also showed that combining the TCT test with fundus photography greatly increases the performance of screening for STDR.