Fundus autofluorescence characteristics in patients with diabetic macular edema

Abstract

Background Diabetic macular edema (DME) is one of the major causes of visual impairment in patients with diabetes mellitus. DME shows a variety of clinical characteristics with unpredictable results to treatment. The purpose of this study was to investigate the characteristics of fundus autofluorescence (FAF) in DME, which is a rapid, noninvasive technique for fundus diseases. Methods A total of 18 patients (30 eyes) with clinically significant macular edema (CSME) were enrolled. FAF imaging was performed with a confocal scanning laser ophthalmoscope. Other ophthalmic examinations included best corrected visual acuity (BCVA), MP-1 microperimetry, and spectral-domain optical coherence tomography (SD-OCT). Main outcome measurements included BCVA, macular sensitivity (MS), central retinal thickness (CRT), central retinal volume (CRV), the integrity of the inner segment-outer segment junction (IS/OS), and the integrity of the external limiting membrane (ELM). Results Among the 30 eyes, four eyes (13.3%) had normal foveal FAF and 26 eyes (86.7%) had abnormal FAF. Abnormal FAF was mainly divided into three types: cystoid increased FAF (iFAF) 16 eyes (53.3%), spot iFAF six eyes (20%), irregular decreased FAF (dFAF) four eyes (13.3%). According to the FAF morphology, patients were categorized into four groups: normal, cystoid iFAF, spot iFAF, and irregular dFAF. There was a significant difference in BCVA (P <0.001) and MS (P <0.05) among the four groups. The visual function of patients with spot iFAF and irregular dFAF was relatively poor. However, there was no difference in CRT (P=0.186) and CRV (P=0.191) among the four groups. In the normal FAF group, the photoreceptor layers were mostly intact. Regarding the cystoid iFAF group, the photoreceptor layers were relatively intact, while in the other two groups, IS/OS and ELM were disrupted in most patients. No one had intact IS/OS or ELM layer. Conclusions FAF might reflect the damage of the retina and had a relationship with visual function as well as photoreceptor integrity, which gives new insight into the evaluation of DME. Dynamic FAF monitoring helps to better evaluate the disease progression of DME as well as visual function.