Quantitative assessment of macular thickness in normal subjects and patients with diabetic retinopathy by scanning retinal thickness analyser

Aims-To evaluate the scanning retinal thickness analyser (RTA), a novel non invasive imaging instrument, in diagnosing and quantitatively characterisin g diabetic macular oedema, and to investigate the relation between central macula thickness measured by RTA and other clinical examinations. Methods-Central macular thickness was measured using the RTA in 40 normal s ubjects and 60 patients with diabetic retinopathy. The reproducibility of t he retinal thickness measurements was evaluated by calculating the mean of the inter- and intrasession variations. Central. macular thickness was corr elated with the results of visual acuity measurements, biomicroscopy, and f luorescein angiography. Results-Intra- and intersession reproducibility of the RTA in normal subjec ts was plus or minus 5.2% (16 mu m) and plus or minus 6.1% (19 mu m), respe ctively. The mean central macular thickness was 182 (SD 16) mu m in normal subjects, 283 (116) pm in diabetic eyes without clinically significant macu lar oedema (CSMO), and 564 (168) mu m in diabetic eyes with CSMO. Central m acular thickness was significantly greater (p<0.001) in eyes with diabetic retinopathy than in normal subjects, even when macular thickening did not m eet the standard for CSMO (p=0.019) measured by biomicroscopy. Although gre ater fluorescein leakage at the macula results in greater central macular t hickness, only eyes with diffuse leakage had statistically significant macu lar thickening compared with normal subjects (p=0.022). Central macular thi ckness measured with the RTA was significantly correlated with the logarith mic converted visual acuity (r(2)=0.76) in diabetic eyes. Conclusion-Scanning RTA, which has good reproducibility, might be useful to quantitatively detect and monitor macular thickening in diabetic retinopat hy. Central macular thickness was highly correlated with logarithmic conver ted visual acuity in diabetic macular oedema.