Expected value of foveal thickness in macular edema in Mexican patients with diabetes.

Background: The tomographic cut-off point to detect macular edema uses an international reference of retinal thickness, which is greater than that in our population. We undertook this study to identify the expected value of central subfield mean thickness (CSMT) in Mexican patients with diabetes with clinically significant macular edema (CSME) and the proportion in which using only the tomographic cut-off point for clinical macular edema (>300 μm) could overlook the diagnosis.

Methods: We carried out an observational, analytical, crosssectional and prospective study. Eyes of diabetic patients with CSME (January 2006-June 2007) with a fluorescein angiography and optical coherence tomography were included. The sample was divided according to angiographic type: monofocal (group 1), multifocal (group 2), or diffuse (group 3). The mean of CSMT of each group was weighed by the proportion represented by each group to calculate the all-type expected value. The proportion of eyes with CSMT = 300 μm was identified.

Results: Ninety-three eyes were included. Mean age was 60.9 years; there were 57 females (61.3%). Forty-one eyes were assigned to group 1 (44.1%, CSMT 210.63 μm), 31 to group 2 (33.3%, CSMT 279.65 μm), and 21 to group 3 (22.6%, CSMT 327.14 μm). The expected value of CSMT was 259.9 μm, 37.75% over the normal reference in the study population and 23% over the American reference. CSMT was <300 μm in 79.6% of the eyes (95% CI 71.4-87.8).

Conclusions: The expected value of CSMT in Mexican patients with diabetes with CSME was within the range internationally regarded as subclinical. Using local references of CSMT is recommended to avoid overlooking the diagnosis of CSME and overestimating its treatment effect.