Microperimetry provides sensitive measure of macular function in sickle cell patients

This study's authors correlated macular structural changes by spectral-domain optical coherence tomography (SD-OCT) with functional changes by scanning laser ophthalmoscope (SLO) microperimetry testing in patients with sickle cell hemoglobinopathies. The results, reported in the October issue of the American Journal of Ophthalmology, indicate that sickle cell patients with macular thinning had significantly decreased retinal sensitivities on SLO microperimetry compared with sickle cell patients with normal macular thickness and with similar-aged controls. SD-OCT and SLO appear to be useful modalities in sickle cell patients for assessing retinal pathology not detected by clinical examination.

Using SD-OCT and SLO microperimetry, the authors prospectively examined 19 patients (37 eyes) with electrophoretic confirmation of sickle cell hemoglobinopathies and 34 similar-aged control subjects (34 eyes). Based on SD-OCT findings, the sickle cell cohort was subdivided into those with focal macular thinning and those without.

Mean age and mean logMAR BCVA were similar between the sickle cell groups with and without focal macular thinning. However, the group with thinning had significantly thinner retinas in the parafoveal superior (P = .019), parafoveal temporal (P < 0.004), parafoveal inferior (P = 0.003), perifoveal superior (P < 0.04), perifoveal temporal (P = 0.0005) and perifoveal inferior (P = 0.045) subfields compared with the group without thinning. The overall mean microperimetry retinal sensitivities of the focal macular thinning group were significantly less than those of the other group (14.2 dB vs. 16.5 dB, P = 0.00005). However, there was no statistical difference between the group without focal macular thinning and controls (16.5 dB vs. 16.7 dB, P = 0.63).

The authors say that thinning is most notable in the temporal subfields among the group with focal macular thinning likely because macular ischemia tends to occur in watershed areas along the temporal horizontal raphe, thus sparing the fovea and central visual acuity. Therefore, they conclude that microperimetry testing may be a more sensitive tool to detect macular ischemia than visual acuity testing alone and that longitudinal follow-up with microperimetry testing could be useful for monitoring the natural history of any progressive loss of macular function in patients with sickle cell hemoglobinopathies.

They say that SD-OCT may be a more sensitive test than microperimetry to detect subclinical macular ischemic thinning, which may prompt a more thorough examination of the peripheral retina to look for evidence of peripheral ischemia and more advanced stages of sickle retinopathy. They conclude that macular SD-OCT scans and/or microperimetry may be of use in the future as an additional clinical test to help hematologists choose appropriate systemic therapy for sickle cell patients.