Comparative study to evaluate retinal changes using spectral-domain optical coherence tomography in diabetics without diabetic retinopathy

PURPOSE: To elucidate changes in the neuro-sensory retina at the macula, using spectral-domain optical coherence tomography (SD-OCT) in type 2 diabetics without clinical signs of diabetic retinopathy, and compare with healthy subjects. METHODS: This was a cross-sectional observational study, conducted at a tertiary eye institute from November 2018 to March 2020. Type 2 diabetics visiting the outpatient department with normal fundus (without any clinical signs of diabetic retinopathy) were taken as Group 1, and healthy subjects as Group 2. Both underwent recording of visual acuity, intraocular pressure (non-contact tonometry), slit-lamp anterior segment examination, fundus examination using an indirect ophthalmoscope, and macular SD-OCT. SPSS (Statistical Package for Social Sciences) version 20 [IBM SPSS statistics (IBM corp. Armonk, NY, USA released 2011)] was used to perform the statistical analysis of the data entered in the excel sheet. RESULTS: Our study included 440 eyes of 220 subjects, divided equally into two groups. The mean age of patients with diabetes was 58.09 ± 9.42 years, and of controls 57.25 ± 8.91 years. The mean BCVA in group 1 and group 2 was 0.36 ± 0.37 and 0.21 ± 0.24 logMAR, respectively. SD-OCT showed thinning in all areas in group 1 compared to group 2, but statistically significant thinning was seen only in the central subfield (P = 0.0001), temporal parafoveal (P = 0.0001), temporal perifoveal (P = 0.0005), and nasal perifoveal areas (P = 0.023) in group 1. There was a significant inter-eye difference noted between the right and left eyes in nasal and inferior parafovea only in group 1 (P = 0.03). No significant difference was noted between males and females. CONCLUSION: There was significant macular thinning in diabetics compared with controls, which denotes the occurrence of neuronal damage in these eyes before clinical evidence of diabetic retinopathy.