Abstract
Purpose: :
To assess the light-backscatter of intraretinal layers in normal and diabetic eyes with no or minimal diabetic retinopathy using Optical Coherence Tomography (OCT)
Methods: :
Standard macular mapping by Stratus OCT were performed in 74 healthy eyes (34±16 years) and 26 eyes with diabetes mellitus (DM) with no or minimal diabetic retinopathy (19 eyes no DR [DM; 32±9 years] and 7 eyes with minimal DR [MDR; 63±18]) on biomicroscopy. Automatic layer segmentation was performed using a custom-built algorithm. Mean values of thickness and relative light-backscatter of the RNFL, GCL+IPL, INL, OPL, ONL, IS/OS and RPE in healthy normal, DM and MDR eyes were compared using ANOVA followed by Newman-Keuls post hoc analysis. A p value of <0.05 was considered statistically significant.
Results: :
Relative light-backscatter was significantly less in DM eyes than in normal (p<0.05 for all the layers except ISOS). However, thickness of the RNFL, ONL and ISOS was not significantly less in DM than in controls. Relative light-backscatter was significantly less in MDR eyes than in normal for only the RNFL, ISOS and RPE (p<0.05). Nevertheless, thickness of the GCL+IPL, OPL and ONL was significantly less in MDR than in healthy eyes. Relative light-backscatter and thickness in the GCL+IPL, INL, OPL and ONL was significantly more in MDR than in DM eyes (p<0.05). No significant differences in light-backscattering between DM and MDR eyes were obtained for ISOS and RPE. There was no difference in RNFL relative light-backscatter and thickness between DM and MDR eyes (45±8 % vs. 45±6%, p=0.96; and 41±3µm vs. 42±4µm, p=0.38; respectively). On the contrary, RNFL’s light-backscatter was significantly less in eyes with DM and MDR than in normal eyes. Moreover, GCL+IPL’s thickness in MDR eyes showed a tendency towards thinning as compared with normal and DM eyes. Conversely, ONL and OPL’s thickness showed an increasing trend in the MDR group.
Conclusions: :
Our results suggest that the GCL+IPL complex is more susceptible to initial damage than RNFL when comparing MDR with DM eyes. This may reflect neurodegenerative changes in the diabetic retina. The trend observed for the GCL+IPL’s thickness and its relative light-backscattering in MDR eyes might be associated with pathological metabolic changes in the retina. Light-backscattering along with thickness information of the various cellular layers of the retina may provide useful information about the pathological changes in retinal morphology.
Keywords: image processing • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • diabetic retinopathy