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Jamie Leong, Ronald Silverman, Stanley Chang, Quan Hoang; Assessing IOLMaster Measurement of Eye Axial Length in Pathologic Myopia Patients with Staphyloma. Invest. Ophthalmol. Vis. Sci. 2013;54(15):5858.
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Pathologic myopia, or extreme near-sightedness, is a leading cause of blindness worldwide. In these eyes, there is axial lengthening and eye wall thinning, allowing for focal outpouchings (staphyloma). Accurate axial length measurement is critical in gauging myopic progression. Depending on the local shape or slope at the staphylomatous area being examined, there may be unreliable measurements due to aberrant reflections of light waves. The present work compares IOLMaster-measured axial lengths and manually-measured axial lengths on B-scan ultrasonography.
A prospective study was performed on 5 pathologic myopia patients clinically diagnosed with staphyloma. 5 eyes underwent measurement with both IOLMaster and B-scan ultrasonography (Quantel CineScan, 10 MHz) oriented in the anterior-posterior direction. Axial length measurement with IOLMaster was compared to that found on manual measurement by a single investigator (JL), on static frames selected from video B-scan ultrasonography captured by an experienced ultrasonographer (RS).
Among pathologic myopia patients with staphyloma, paired t-test analysis shows no significant difference in axial lengths measured by IOLMaster and those manually measured on B-scan ultrasonography. Axial lengths measured by the IOLMaster were greater by an average of +0.64 mm (range -0.87 to +2.58, n = 5). Although this was not statistically significant (2-tailed paired t-test, p = 0.40), the range from -0.87 to +2.58 mm is equivalent to -2.61 diopters to +7.74 diopters (a 10.35 diopter range).
Assessment of axial length in staphylomatous eyes may be challenging, potentially influenced by staphyloma location and local slope. Initial studies suggest that axial length measured by IOLMaster is comparable to that found by manual measurement on 2-D B-scan ultrasonography, but given the wide variation, the use of both methods together is likely to provide the most accurate results in staphylomatous eyes.
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