Methods: Thirty-seven patients with HLA-B27-positive AAU and 32 patients with HLA-B27-negative AAU were analyzed. Clinical characteristics, HLAB27 typing and retinal nerve fiber layer thickness measurements were recorded. All data were compared with 35 age and sex matched healthy subjects. ROC analysis was used to determine the RNFL threshold in patients with HLA B27 positive AAU.

Results: There was no signifi cant difference between the HLA-B27 (-) group and the control group in terms of RNFL thickness in the temporal, temporal inferior and nasal inferior quadrants. (P = 0.293, p = 0.064, p = 0.033, respectively) In all other quadrants, RNFL thickness of the HLA-B27 (+) and HLA-B27 (-) groups was thicker than the control group. RNFL thicknesses in temporal superior, nasal superior and nasal inferior quadrants were signifi cantly thicker in the HLA-B27 (+) group compared to the HLA-B27 (-) group. (P = 0.008, p = 0.012, p = 0.016, respectively) According to ROC analysis, RNFL thresholds were 139 µm, 111.50 µm and 110.50 µm in temporal superior, nasal superior and nasal inferior quadrants, respectively. A signifi cant and positive correlation was found between RNFL and anterior chamber cell counts in all quadrant AAU patients.

Conclusion: RNFL thickness increases more in HLA-B27 positive patients than in negative patients. RNFL thickness above the threshold values determined by ROC analysis may indicate HLA-B27 positivity. Keywords : HLA-B27 positivity, Acute anterior uveitis, Retinal nerve fiber layer thickness, ROC analysis, Idiopathic uveitis