Iris Morphology in Diabetic Eye Disease: Optical Coherence Tomography Study
Purpose
To explain the poor pupillary dilation and floppy iris observed during cataract surgery in patients with diabetes and to study changes in iris morphology which occur in patients with diabetic ocular disease in comparison to non-diabetic patients.
Methods
A retrospective chart review was undertaken to identify patients with diabetic eye disease as well as non-diabetic controls who had previously undergone Anterior Segment Optical Coherence Tomography (AS-OCT). Patients were separated into two groups based upon the presence or absence of diabetic eye disease. The previously acquired AS-OCT images were reanalyzed by measuring iris thickness in the dilator muscle region (DMR) and sphincter muscle region (SMR). Pupillary diameter (PD) was measured for quality control. DMR/SMR ratios were calculated. Mean iris thickness in each region, mean DMR/SMR ratio, and mean PD were then compared between the two groups.
Results
The Diabetic group (n=10 eyes) exhibited significant iris thickening in the SMR as compared to the Control group (n=9 eyes); 429±82µm versus 354±52µm (p=0.0032). The DMR was additionally significantly thickened in the Diabetic group compared to the Control group; 386±88µm versus 332.59±58µm (p=0.044). The DMR/SMR ratio was preserved between the Diabetic and Control groups; 0.92±0.22 versus 0.94±0.12 (p=0.74). PD did not differ significantly between the Diabetic and Control groups; 3325±1429µm versus 3299±482µm (p=0.96).
Conclusion
Patients with diabetic eye disease exhibit iris thickening compared to non-diabetics, in both the SMR and DMR. This might result from iris ischemia associated with diabetic eye disease and represents morphologic evidence of the pathologic process underlying impaired pupillary dilation and floppy iris during cataract surgery in diabetic patients.