Assessment of multifocal contact lens over-refraction using an infrared, open-field autorefractor: A preliminary study.

PURPOSE: To evaluate the usefulness of an infrared open-field autorefractor as a predictor of the refractive error when fitting multifocal contact lenses (MCL). METHODS: Objective and subjective measurements of the non-cycloplegic distance refractive error were compared in patients wearing MCL. We used the Grand Seiko WAM-5500 autorefractor for the objective measurements. Three commercially available MCL were tested. Twenty-one eyes of sixteen healthy adults were included in the study. Over-refraction was evaluated in terms of spherical equivalent (SE) and astigmatic vectors (J0 and J45). The mean difference±SD of each parameter was calculated. The Kolmogorov-Smirnov test was used to verify the normal distribution. Pearson's correlation, Bland and Altman plot and paired sample t test were used to compare the results obtained with both methods. RESULTS: The mean difference between objective and subjective results of the SE over-refraction was 0.13±0.42D; for astigmatic vectors J0 and J45 were 0.03±0.32D and -0.00±0.17D, respectively. The Kolmogorov-Smirnov test showed a normal distribution for all parameters. The highest Pearson's correlation coefficients were obtained for the SE with values of 0.98 without MCL and 0.97 with MCL. The lowest were obtained for J45 with values of 0.65 without MCL and 0.75 with MCL. Significant correlations were obtained for each parameter. The paired sample t test failed to show significant differences in analyzed parameters except for J0 without MCL. CONCLUSIONS: The Grand Seiko WAM-5500 can be used as a screening method of over-refraction in the clinical fitting of MCL.

Optical quality and intraocular scattering in a healthy young population.

BACKGROUND: We objectively assessed the optical quality and intraocular scattering by means of parameters provided by a clinical double-pass system in healthy young subjects and thereby we obtained new reference data for clinical diagnosis. We calculated normal values of neural contrast sensitivity function (nCSF) from the measured modulation transfer function (MTF) and the contrast sensitivity function (CSF). METHODS: Eligible subjects were healthy adults aged from 18 to 30 years with a logMAR visual acuity (VA) of 0.0 or better and normal values of CSF. Optical quality measurements for a 4.0 mm pupil were performed using the Optical Quality Analysis System (OQAS) based on the double-pass technique. The following parameters were analysed: the modulation transfer function cutoff frequency (MTF(cutoff)), the Strehl(2D) ratio, the OQAS values (OV) at 100, 20 and nine per cent contrasts and the objective scatter index (OSI). RESULTS: A total of 178 volunteers responded to the call, of whom 181 eyes were finally part of the study taking into account the criteria for inclusion. The values for the optical quality parameters were: 44.54 ± 7.14 cpd (MTF(cutoff)), 0.27 ± 0.06 (Strehl(2D) ratio), 1.48 ± 0.24 (OV(100%)), 1.58 ± 0.32 (OV(20%)), 1.64 ± 0.39 (OV(9%)), and 0.38 ± 0.19 (OSI). The nCSF calculated was 1.76 ± 0.21 (3 cpd), 2.13 ± 0.23 (6 cpd), 2.01 ± 0.28 (12 cpd) and 1.86 ± 0.33 (18 cpd). CONCLUSION: The normal values provided can be a useful tool for discriminating healthy eyes from early abnormal ones in which the optical quality or sensory function is impaired.