Abstract
Purpose :
It is well known that the development of glaucoma is accompanied by some loss of contrast sensitivity (CS) but it is not clear how practicable or useful a measurement of CS is in identifying different stages of glaucoma progression. We have examined whether simple disposable printed (CamBlobs) charts, that could be used with illiterate patients, can provide quick and reliable CS measurements in patients with glaucoma.
Methods :
CS of 21 patients (40 eyes) with diagnosed glaucoma was measured and compared with 27 age-matched controls using paper CamBlobs charts (Robson JG, et al. IOVS 2016; 57:ARVO Abstract 6105), On each row of the A4-sized charts (210 x 297mm) there are four grey spots, 9mm in diameter, randomly located at different positions along the row. The contrast of all spots in each row is the same and 0.05 log units (0.5 dB) lower than that of the spots in the row above it. The Weber contrast of the spots varies from 14% (at the top of the charts) to less than 1% (at the bottom). Subjects view the charts at reading distance and demonstrate that they have seen the spots by correctly marking them with a cross. The contrast of the faintest spots whose position can be accurately identified is a measure of a subject's contrast sensitivity. Patients were categorized based on their MD (24-2).. Eyes with any other pathology were excluded. Lens changes were allowed only if they were < NS2, P1, C2 (LOCS II). CS was also measured using a standard Pelli-Robson (P-R) chart.
Results :
CS of glaucoma patients was significantly lower (p<10-8) than that of control subjects. CS loss increased with the severity of the condition, as shown by both CamBlobs and P-R charts. The correlation between MD24-2 and logCS measured with CamBlobs was significant (r = 0.61) and similar to that found in previous studies; it was considerably larger than the correlation with distance logMAR (r = 0.29). The data were used to construct ROC curves. The area under the ROC curve for distinguishing all glaucomatous eyes from normals was 0.88, while the area under the curve for distinguishing mild glaucomatous eyes (MD > -6dB) was 0.80.
Conclusions :
CS can be measured easily and quickly in patients with glaucoma using the CamBlobs charts and could be useful in detecting the disease and assessing its progression. The use of CamBlobs charts is especially appropriate with patients who are illiterate or when home monitoring is required.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.