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Jonathan Tang, Jane Y Pan, Stanley Chang, Quan V Hoang; Comparison of Ocular Axial Length Measurements with MRI and Partial Coherence Interferometry in Highly Myopic Patients with Posterior Staphyloma. Invest. Ophthalmol. Vis. Sci. 2014;55(13):5939.
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© ARVO (1962-2015); The Authors (2016-present)
Accurate axial length measurement is critical in gauging myopic progression. Partial coherence interferometry used in machines such as the Zeiss IOLMaster is the most commonly used method in clinical ophthalmology for measuring axial length. Due to irregularities of slope and shape in the posterior wall of staphylomatous eyes, aberrant reflections are possible and can result in inaccurate measurements. This present work compares IOLMaster-measured axial lengths and manually measured axial lengths on 3-D MRI volume renderings in highly myopic patients with staphyloma.
A prospective study was performed on 32 eyes of 16 patients with high myopia clinically diagnosed with staphyloma. All eyes underwent measurement with both IOLMaster and 3-D MRI scan (Phillips, 3.0T, fat-suppressed T2-weighted cube, a modified 3-D fast-spin echo sequence). Volume renderings of the eyes were generated from high-resolution 3-D data and properly oriented so the eye could be rotated around its visual axis. MRI axial length (from the posterior cornea to the vitreo-retinal interface) was manually measured from 4 different views (each 90 degrees apart) and averaged. Axial length measurement with IOLMaster was compared to that found with the 3-D MRI rendering of the eye.
Eyes examined ranged in axial length from 27.40 to 39.32 mm on IOLMaster and from 26.48 to 39.32 mm on MRI. The axial length measured by IOLMaster was longer than that measured by MRI in 30 out of 32 eyes. On average, the axial length measured by IOLMaster was 0.46 +/- 0.33 mm (mean +/- standard deviation) longer than that measured by MRI (range -0.34 to 1.16 mm). This difference was not significant at conventional levels (p = 0.55, two-tailed t-test).
The longer axial length measured by IOLMaster may be partially explained by a contribution from retinal thickness. 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 3-D MRI.
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