Comparison of Partial Interferometry and Ultrasound A-scan for Axial Length Measurement in Retinal Vein Occlusions

ABSTRACT

PURPOSE: To evaluate the significance of axial length, which is a known risk factor of retinal vein occlusion, we measured the axial lengthby using contact A-scan sonography and partial interferometry and compared the two values. METHODS: This study included 19 patients complaining of visual symptoms and who were diagnosed with unilateral retinal vein occlusion (RVO) with macular edema (ME). Affected eyes were classified as the study group, and healthy fellow eyes were classified as the control group. We measured the central macular thickness (CMT) and axial length (AL) of the affected and fellow eyes and compared them. CMT was measured by optical coherence tomography (Stratus OCT, Carl Zeiss, Jena, Germany), and AL was measured by interferometry (IOL Master®, Carl Zeiss, Jena, Germany). RESULTS: In RVO patients, CMT was significantly different between affected eyes (485.7 ± 111.3 µm) and fellow eyes (197.8 ± 29.7 µm; p < 0.001). Axial length measured by A-scan sonography was 23.06 ± 0.86 mm in the affected eyes and 23.28 ± 0.93 mm in the healthy eyes, which was statistically different (p < 0.001). However, using partial interferometry, the AL was 23.35 ± 0.87 mm in the affected eyes and 23.38 ± 0.95 mm in the healthy eyes. No significant difference was found. CONCLUSIONS: We confirmed that short AL, which was once thought to be a risk factor of RVO, results from the properties of the instruments used for measurement. Moreover, we verified that partial interferometry is more accurate for measurement of AL than A-scan sonography when retinal vein occlusion is associated with ME.