Abstract
Purpose: :
To evaluate the correlation between integrity of the photoreceptor inner/outer segment (IS/OS) layer on edema involving the 1000 µm of the central macular area and its relationship with best corrected visual acuity (BCVA) in eyes with macular edema in diabetes type2.
Methods: :
Forty-six eyes of 32 patients with DME involving the 1000 µm central macular area were included in this retrospective study. All subjects underwent spectral domain-optical coherence tomography (HD-OCT CirrusTM) and BCVA was measured using ETDRS charts. The photoreceptor IS/OS layer was evaluated, on horizontal and vertical scans, for 500µm in either direction of the fovea. This was manually graded from 0 to 4: grade 0 meaning intact IS/OS layer, grade 1 focal disruption of the IS/OS junction of ≤250µm, grade 2 one disruption between 250µm to 500µm, grade 3 one disruption between 500µm to 750µm, grade 4 one disruption ≥750µm. Logistic regression analysis was used to estimate the relative contribution of the value and type of edema, grade of IS/OS disruption to BCVA.
Results: :
Of the 46 eyes with DME, 18 had a score of BCVA of 75 or more letters and a mean retinal thickness (RT) of 351µm whereas the other 28 eyes had a BCVA less than 75 letters and a mean RT of 448µm. Some degree of disruption of the photoreceptor IS/OS layer was detected in 93% of the 46 cases. In the sub group with good VA 12 eyes (70%) were classified as grade 1, 3 eyes (18%) as grade 2, 1 eye (6%) as grade 3 and 1 eye (6%) as grade 4. In the sub-group with worse VA no cases were classified as grade 1 and 2, 7 eyes (25%) were classified in grade 3, and 21 eyes (75%) as grade 4. The sub-group with worse VA (<75 letters) showed clearly more extensive disruption of the photoreceptor IS/OS layer presenting only grade 3 and 4 - disruption of more than half of the central 1000µm. In contrast, the group with better VA (≥75 letters) showed much less disruption of the photoreceptor IS/OS layer being predominantly of grade 1 and 2 involving less than half of the central 1000µm with the exception of only two cases. Extensive disruption of the photoreceptor IS/OS layer appears to be a good indicator of poor visual acuity among patients with DME (r2= 0,852, p<0,001).
Conclusions: :
Extensive disruption of the photoreceptor IS/OS layer in the central macular area (1000µm) shows statistically significant associating with poor visual acuity among patients with DME. The evaluation of IS/OS layer integrity on OCT is a relevant parameter and should be considered when comparing treatment outcomes.
Keywords: diabetic retinopathy • photoreceptors • visual acuity