Measurement of Axial Length by Applanation Ultrasound Relative to Optical Biometry in Normal Eye


ABSTRACT:BACKGROUND:The precision of axial length measurement has great impact on successful cataract surgery and refractive outcome besides its diagnostic role of many ophthalmic conditions. There are various methods for axial length measurement which differ in their operating principle and technology beside the difference in their advantage and limitation.AIM OF STUDY: To compare the axial length measurement performed with optical biometry IOLMaster 500(Carl-Zeiss Meditec,Jena, Germany) with those obtained by applanation ultrasound (A-Scan biometer AL-100) in three groups. METHODS: 207 eyes of 104 candidates with age range (20-40 year) were included. These candidates divided into three groups according to axial length; group 1 (22 - 24 mm), group 2 (24.1 – 26 mm) and group 3 (26.1 – 28 mm). Axial length was measured in three groups, firstly by optical biometry then by applanation ultrasound by the same examiner. RESULTS: The axial length measured by IOLMaster was longer than by applanation ultrasound in all groups. The mean differences were (0.15mm, 0.15mm and 0.2 mm) in three groups respectively, which were statistically significant p-value < 0.05. Bland-Altman plots shows there is good agreement between measurements of two devices for all groups.CONCLUSION: The results show optical biometry provided longer axial length than applanation ultrasound with hypermetropic shift (0.35D-0.5D) by applanation ultrasound in normal eye.