Abstract
Purpose :
To measure contrast sensitivity of diabetic patients using illiterate CamBlobs2 charts as a self-administered test, and to relate this to the different levels of diabetic retinopathy (DR).
Methods :
DR of 105 eyes in 56 diabetic patients attending a diabetic eye clinic was graded using retinal photography (dilated pupils) with the ETDRS grading, and confirmed with fluorescein angiography, indirect ophthalmoscopy and OCT measurements as necessary. Patients had minimal lenticular changes and no other ocular disease. The different levels of retinopathy grades were: Grade 0 (none), Grade 1 (mild NPDR, Non Proliferative DR), Grade 2 (moderate NPDR), Grade 3 (severe NPDR/PDR, also graded as sight-threatening retinopathy STR). Contrast sensitivity was measured using hand-held CamBlobs2 charts. These are printed paper charts with 25 rows of round grey spots, each 9mm in diameter, whose log Weber contrast (logC), with respect to the white background, reduces by 0.05 on successive rows ranging from -0.80 at the top to -2.05 at the bottom. On each row of the chart there are 4 randomly spaced spots (all with the same contrast) whose location the subject marks with a pen. The subject's contrast sensitivity is recorded as -logC of the spots on the uppermost row on which the location of no more than two spots has been correctly marked.
Results :
Each increase in the level of severity of retinopathy was associated with a significant reduction in visual function as determined by LogMAR acuity or by CamBlobs2 contrast sensitivity. Receiver Operating Characteristic (ROC) curves were constructed. The area under the ROC curve for differentiating STR from earlier stages of retinopathy based on the contrast sensitivity data was 0.76±0.05, indicating moderately good sensitivity and specificity. Contrast sensitivity measured with CamBlobs2 for eyes with STR was 0.30±0.05 log units (p<0.001) less than for diabetic eyes with no retinopathy.
Conclusions :
This pilot study shows that contrast sensitivity of patients with DR can be satisfactorily measured with a self-administered test using inexpensive printed paper charts. The reduction in contrast sensitivity associated with the progression of DR from none to STR is sufficiently large that it should be possible to identify it by periodically monitoring a patient's contrast sensitivity using CamBlobs2 charts.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.