Abstract Purpose: To evaluate the photoreceptor integrity in diabetic patients with macular edema using spectral domain optical coherence tomography (SD-OCT) Methods: We compared macular thickness in diabetic patients with and without macular edema to determine the role of damage to the external limiting membrane (ELM) or photoreceptors. Diabetic patients were selected from the screening study of > 2000 minority patients seen at Eastmont Wellness Center, Oakland, CA. Patients underwent photoscreening with a Canon Cr-DGi nonmydriatic camera (Tokyo, Japan) and an iVue OCT (Optovue Inc, Fremont, CA). Retinal scans of 70 diabetic patients, age range 33-68 yr., were selected so that A) 50% of patients had clinical significant macular edema (CSME), as diagnosed by the presence of hard exudates within 1 disc diameter from the fovea in the color photos, B) the full range of central macular thicknesses in our population was included. And C) patients with CSME were the same age as those not diagnosed with CSME. We graded the retinal scans according to the external limiting membrane (ELM) integrity; 6 patients had damaged ELM and the remaining 64 had intact ELM. Similarly, we graded the retinal scans according to the photoreceptor integrity; 14 patients had damaged photoreceptors and the remaining 56 had intact photoreceptors Results: Average retinal thickness was 254 µm (±57.4) and 356 µm (±95.9) in patients with intact and damaged ELM, respectively; and was 240 µm (±30.0), and 363 µm (±90.0) in patients with intact and damaged photoreceptors, respectively. Retinal thickness means were significantly greater for patients with damaged compared with intact ELM ( P=0.031). Similarly, Retinal thickness means in patients with damaged photoreceptors were significantly greater compared to patients with intact photoreceptors ( P = 0.0001). We also observed that all 6 patients who have damaged ELM were diagnosed with CSME, but were not significantly older than the diabetic patients not diagnosed with CSME ( P = 0.393) Conclusions: ELM and photoreceptor layer damage are found more often when retinal thickness exceeds 355 µm. It is not known if this outer retinal damage is the result of the edema or whether there is more edema because the outer retinal blood brain barrier is failing