Abstract
Purpose: :
To evaluate the relationship between optic disc ovality and retinal nerve fiber layer (RNFL) thickness measurement using Cirrus OCT. To investigate the influence of disc ovality on glaucoma diagnosis.
Methods: :
A prospective analysis was performed on 588 patients (290 controls and 298 glaucomatous). Optic disc ovality was determined using the ratio of minimum to maximum disc diameter (disc ovality ratio, DOR). Associations between RNFL measurements in controls and DOR were evaluated by linear regression analysis. To evaluate the effect of the DOR on the diagnosis accuracy of Cirrus OCT, the total sample was divided into percentils (DOR ≤ 0.85; 0.85-0.90; 0.91-0.94; ≥0.95). Areas under the receiver operating characteristic curves (AUCs) were calculated for each group (G). T-Student independent data analysis was used to compare the DOR between eyes with incorrect diagnosis (false positive, and false negative) and correct diagnosis (true positive, and true negative).
Results: :
For the average RNFL, inferior and superior quadrants, significant negative correlations were found between RNFL thickness and the DOR (rs= -0.12, p=0.03; rs= -0.18, p=0.008; rs= -0.18, p=0.005, respectively). No significant association was found between the DOR and the nasal and temporal quadrant measurements. The AUCs for RNFL thickness were similar between groups for the average measurement (G 1= 0.82; G 2= 0.77; G 3= 0.81; G 4= 0.85) and for the inferior (G 1= 0.85; G 2= 0.77; G 3= 0.85; G 4= 0.85) and superior (G 1= 0.82; G 2= 0.75; G 3= 0.80; G 4= 0.80) quadrants. For the nasal quadrant, significant differences were found between groups (G 1= 0.58; G 2= 0.68; G 3= 0.69; G 4= 0.69) and eyes with correct diagnosis (true positives) showed higher DOR compared with eyes with incorrect diagnosis (false positives) (p=0.003).
Conclusions: :
Although measuring the thickness of the RNFL is influenced by the DOR, the ability of Cirrus OCT to diagnose glaucoma is not affected by optic disc ovality when the average, superior or inferior quadrants are evaluated.
Keywords: optic disc • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)