Abstract
Purpose:
To compare retinal nerve fiber layer thickness (RNFLT) measurement by Stratus and Cirrus OCTs and to evaluate the agreement between the two instruments in retrobulbar optic neuritis (RON), non arteritic anterior ischemic optic neuropathy (NAION) and normals.
Methods:
Eighty-nine eyes with RON, ninety-two with NAION (both in the chronic phase, six to twelve months after diagnosis of acute disease), and one hundred fifty-five normal eyes were studied. Average RNFLT was measured by Stratus and Cirrus OCTs. Comparisons among groups were performed by ANOVA test. The agreement between the two instruments was assessed using intraclass correlation coefficient (ICC) with 95% confidence interval (CI), and Bland-Altman analysis. Statistical significance was set at p ≤0.5.
Results:
Average RNFLT was lower in NAION eyes than in RON and normal ones using both OCTs (60.0 ±1.2, 69.9 ±1.2 and 97.4 ±0.9 µ, p<0.001 by Cirrus; 49.7 ±1.5, 65.9 ±1.9 and 99.2 ±1.3 µ, p<0.001 by Stratus). RNFLT values were higher with Cirrus than with Stratus in NAION (+10.30 μ, CI 7.82 - 12.79 μ) and RON (+4.01 μ, CI 1.32 - 6.70 μ) eyes, and slightly lower in normal ones (-1.75 μ, CI -3.51 - 0.01 μ). A stronger agreement between the two instruments was found in normal and RON eyes than in NAION ones (ICC 0.682, CI 0.566-0.771; 0.635, CI 0.467-0.758; 0.321, CI 0.132-0.472, respectively).
Conclusions:
Both Stratus and Cirrus OCTs can identify RNFLT reduction in eyes with RON and NAION in the chronic phase. Absolute RFNLT values differ between the two instruments, hence they have not to be considered interchangeable.<br />