Abstract
Abstract: :
Purpose: To determine the inter-occasion repeatability and the comparability of measurements of axial length using the Zeiss Humphrey IOL Master and standard ultrasound under two different mydriatic/cycloplegic conditions. Methods: We measured axial length and anterior chamber depth (ACD) on 14 young adult subjects (average age SD = 23.8 1.5 years, refractive error range -3.96 D to +7.31 D) using the Zeiss Humphrey IOL Master and a standard ultrasound biometer (Humphrey model 820). Five readings were taken and averaged using both instruments 30 minutes following instillation of two drops of phenylephrine 2.5% (PE) on two occasions separated by at least one week. Measures were also made 30 minutes following instillation of cyclopentolate 1% (CYCLO) on one of these occasions chosen at random. Results: The IOL Master and ultrasonography gave comparable results for axial length under both mydriatic/cycloplegic conditions (CYCLO: 23.92 1.07 mm for IOL Master, 23.87 1.05 mm for ultrasound; P=0.21; PE: 23.93 1.06 mm for IOL Master, 23.90 1.04 mm for ultrasound; P=0.45). The very small difference in axial length as a function of drug type was statistically significant for the IOL Master (0.015 mm, P=0.018) but not for ultrasonography (0.036 mm, P=0.49). ACD was shallower with ultrasonography than with IOL Master by 0.11 0.12 mm (P=0.0038), presumably because of ultrasound probe compression of the cornea. Inter-occasion repeatability of axial length was substantially better for the IOL Master than for ultrasonography (95% limits of agreement: 0.052 mm for IOL Master; 0.43 mm for ultrasonography). Conclusion: The IOL Master provides non-contact measures of axial length that are comparable to those from ultrasonography whether PE or CYCLO is used, and that have superior repeatability.
Keywords: 356 clinical (human) or epidemiologic studies: systems/equipment/techniques • 500 optical properties • 430 imaging/image analysis: clinical