[Use of retinal photography in the diagnosis of diabetic macular edema]

OBJECTIVE

To determine the validity of retinal photography in the diagnosis of diabetic macular edema. Determine the number and size of the photographs for its correct diagnosis.

METHODS

Cross-sectional observational study consisting of 420 eyes of patients with diabetic retinopathy, using a combination of retinography (simple, stereoscopic, red-free light), after expansion, to determine its validity in the diagnosis of diabetic macular edema. Sensitivity, specificity, positive and negative predictive values and the correlation with the gold standard test (optical coherence tomography) were calculated. The retinographs were evaluated by three experts and their results analyzed by the statistical program SPSS 15.0 Windows.

RESULTS

Sensitivities were below 80% in simple photographs and above 80% in the stereoscopic retinography, whereas those associated with red-free filters, reaching the 30° green stereoscopic photography, showed a sensitivity of 94.3%. The specificity was 95% in color and red-free stereoscopic retinography of 45° and 30°. The positive predictive value was greater than 95% and the negative value greater than 90% with a coefficient of agreement of 80%, and a degree of consistency with the benchmark of over 80%.

CONCLUSIONS

The results of the stereoscopic retinographs are sufficient to enable them to be used in screening for diabetic macular edema. The use of a green filter and its combination with visual acuity improves results in the diagnosis of this disease.

Retinal thickness in diabetic retinopathy: comparison of optical coherence tomography, the retinal thickness analyzer, and fundus photography

BACKGROUND

Optical coherence tomography (OCT) and the retinal thickness analyzer (RTA) have proved their ability to measure retinal thickness in healthy subjects and diabetics reliably. In the present study, both techniques were compared for the same study population of diabetic patients, and the findings were related to macular edema shown by stereo fundus photography (SFP).

METHODS

Maculas of 124 eyes from 69 patients with diabetes mellitus were examined with OCT and the RTA. Measurements of retinal thickness were compared with signs of macular edema shown by SFP. For each eye, nine different sectors were analyzed (a foveal sector, four parafoveal sectors, and four extrafoveal sectors). Thirteen eyes with a normal macula served as controls. Sensitivity and specificity of detecting clinically significant macular edema (CSME) were calculated.

RESULTS

Of 111 eyes, 64 showed signs of CSME by SFP. Mean retinal thickness +/- SD of the foveal sector was 249 +/- 104 microm by RTA and 295 +/- 124 microm by OCT measurements. There was a moderate overall correlation between OCT and the RTA (r = 0.66). The correlation was best in the foveal sector (r = 0.82). Overall correlation with SFP was better for OCT (r = 0.77) than for the RTA (r = 0.62). Sensitivity of detecting CSME was consistently higher with OCT, while the RTA showed higher specificity.

CONCLUSION

Both measuring techniques yielded similar results when examining eyes of patients with diabetes, although absolute values differed. OCT seems to be more suitable in the clinical screening for macular edema due to its high sensitivity (>90%) with appropriate analysis parameters. The RTA is more prone to erroneous or missing thickness readings particularly under difficult measuring conditions.

Diabetic macular edema: an OCT-based classification

PURPOSE

More than ten years after ETDRS, Optical Coherence Tomography (OCT) greatly enhanced our ability to detect macular thickening and has brought new insights on the morphology of edema and on the presence of vitreal traction. In this study we propose a new classification of macular edema based on OCT findings to better catalogue and follow this complex clinical entity.

METHODS

Since January 2000 we analysed with OCT 2 (Zeiss Inc.) more than one thousand and two hundred eyes with DME.

RESULTS

The classification takes into account five parameters: retinal thickness, diffusion, volume, morphology and presence of vitreous traction. Standard figures and numerical values for every parameter are given.

CONCLUSION

Although ETDRS guidelines for laser treatment of DME still remain the only proven therapy for this condition, many other strategies are now on trial, and the vast majority of authors use OCT as the best indicator of therapeutic benefit. The amount of information given by OCT demonstrates that macular edema is a complex clinical entity with various morphology and gravity, and disclaimed the limitations of a simple "clinical" definition. As in many other examples such as macular holes and choroidal neovascularization, a uniform and precise definition of macular edema would increase the possibility to compare and judge the result of different therapeutic strategies. Aim of this classification is to implement the ETDRS clinical definition of DME with the precise and useful data given by OCT to better diagnose, catalogue and follow macular edema.