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A.E. Knellinger, T.F. Mauger, A.M. Mahmoud, J.R. Lewis; The Effect of Using Soft Contact Lenses to Measure the Axial Length of the Healthy Human Eye Using the IOLMaster . Invest. Ophthalmol. Vis. Sci. 2005;46(13):817.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To evaluate the reproducibility of the IOLMaster axial length measurement in the presence of a soft contact lens in healthy human eyes and accuracy using optical coherence tomography. Methods: Each axial length was measured 10 times using the IOLMaster (Zeiss) in 20 eyes of 20 normal subjects (10 female; mean age 27.25 ± 4.92 years; average mean spherical equivalent –2.83 D, range –0.13 D to –6.63 D; 7 non–contact lens wearers) in the absence of and presence of a SofLens 38 (Bausch & Lomb, CL1) contact lens or Acuvue2 (Johnson & Johnson, CL2) contact lens, each with a base curve = 8.7mm, diameter = 14mm, and power = –0.50 D. Optical coherence tomography (OCT–1, Zeiss) A–scans were taken before each IOLMaster series to measure directly the change in central corneal thickness including the contact lens and pre–lens tearfilm. Statistical analysis was performed using SAS. Reproducibility was evaluated by analysis of the standard deviations. Results: The mean standard deviation (or variability) of the IOLMaster axial length measurements was 20±7 µm without a contact lens, 24±10 µm with CL1, and 23±8 µm with CL2. Addition of either lens did not significantly affect (p=.17) the repeatability of these axial length measurements using the IOLMaster. The mean difference in the axial length relative to the no–lens condition was 59±10 µm and 134±13 µm for CL1 and CL2, respectively. OCT measured a mean central corneal thickness change of 61.0±5.65 µm for CL1 and 136.1±3.0 µm for CL2 (including pre–lens tearfilm) from 3 scans across a central 1–mm region. Conclusions: A technique to measure axial length using a soft contact lens and the IOLMaster has been compared in normal healthy subjects using two different lenses. The technique provided repeatable measurements using either contact lens. The change in axial length added by CL1 and CL2 was accurately detected by the IOLMaster as compared to OCT measurements of each contact lens and pre–lens tearfilm thickness.
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