We read the article by Hoang and associates with great interest. This is the first study using a segmental analysis of the macula to demonstrate thinning by spectral-domain optical coherence tomography (OCT) in asymptomatic female sickle patients. The authors conclude that this patient population has significant central macular thinning and splaying, when compared to healthy, matched control subjects. They suggest that since foveal thinning may be indicative of more global retinal ischemia, the presence of thinning may be a useful screening modality for patients to determine the need for a more thorough examination.
However, we have concerns about the methodology and conclusions of the study. In the table underscoring the demographics of their sickle cell retinopathy group, we see that not only do they include different stages of retinopathy, but they even include 6 eyes of 4 patients with no retinopathy. Theoretically, the inclusion of patients with no retinopathy to stage 4 retinopathy is a confounding factor that introduced a level of variability to the study. A better analysis might have examined 3 groups: an age-, gender-, and race- matched control group; a sickle cell group without retinopathy; and a sickle cell group with retinopathy.
Furthermore, they report a mean central total macular thickness (CMT) of 228 ± 3 μm in the control group and 220 ± 3 μm in the study group. In the normative database, the mean central macular thickness or central point thickness on Spectralis OCT has been reported as 227.3 ± 23.2 μm in the general population. Both the control and study group results fall within 1 standard error measurement of the normative data, indicating that the statistically significant difference may not be clinically important. We also wonder whether the authors examined central subfield in their patients, which may be a more clinically useful measurement.