Light distortion and spherical aberration for the accommodating and nonaccommodating eye.

To evaluate how different amounts of induced spherical aberration (SA) affect the light distortion (LD) phenomena, tests were performed using an experimental device to measure the distortion (haloes, glare, and so on) of a point source. To simulate the effect of SA, eight different phase plates between +0.300 and −0.300 µm of SA for a 5-mm aperture were used in a random and double-masked experimental design. Measurements were performed at a distance of 2 m in a darkened room in 10 eyes of five subjects with a mean age of 26.4±6.1 years and a mean refractive error of −0.50±0.70 D. Data were obtained with natural pupil and after pupil dilatation. The measurements with this experimental system showed a significant increase in all distortion parameters with cycloplegia for the phase plates with the higher positive SA (+0.300 and +0.150 µm). The disturbance index increased from 14.86±6.12% to 57.98±36.20% (p<0.05) with the +0.300 µm plate. The same effect was observed through at a much lower rate when the eye could accommodate. Plates inducing negative SA did not change the LD compared to the control condition without induction of SA or even decreased the effect of distortion. Pupillary dilation and cyclopegia led to a significant increase in the size of the LD when increasing values of SA were induced. Accommodation and pupillary constriction are capable of compensating the degradation of the optical quality induced.

Validation of a method to measure light distortion surrounding a source of glare.

Our objective was to validate a new device dedicated to measure the light disturbances surrounding bright sources of light under different sources of potential variability. Twenty subjects were involved in the study. Light distortion was measured using an experimental prototype (light distortion analyzer, CEORLab, University of Minho, Portugal) comprising twenty-four LED arrays panel at 2 m. Sources of variability included: intrasession and intersession repeated measures, pupil size (3 versus 6 mm), defocus (+0.50 ) correction for the working distance, angular resolution (15 deg versus 30 deg), temporal stimuli presentation, and pupil size. Size, shape, location, and irregularity parameters have been obtained. At a low speed of presentation of the stimuli, changes in angular resolution did not have an effect on the results of the parameters measured. Results did not change with pupil size. Intensity of the central glare source significantly influenced the outcomes. Examination time was reduced by 30% when a 30 deg angular resolution was explored instead of 15 deg. Measurements were fast and repeatable under the same experimental conditions. Size and shape parameters showed the highest consistency, whereas location and irregularity parameters showed lower consistency. The system was sensitive to changes in the intensity of the central glare source but not to pupil changes in this sample of healthy subjects

Performance of three multipurpose disinfecting solutions with a silicone hydrogel contact lens.

PURPOSE: To evaluate the clinical performance of a silicone hydrogel (Si-Hy) soft contact lens (CL) in combination with three different multipurpose disinfecting solutions (MPDSs). METHODS: This was a prospective, randomized, single-masked, crossover, and comparative study in which 31 habitual soft CL wearers were randomly assigned to one of the three MPDSs (Synergi, COMPLETE RevitaLens, and OPTI-FREE PureMoist) for 1 month with a 1-week wash-out period between each exposure. All subjects were successfully refitted with a Si-Hy CL (Biofinity). Subjects were then scheduled for follow-up visits after 1 month of lens wear, being evaluated at 2 and 8 hours after lens insertion. Visual Analogue Scales (VAS) were used to gauge comfort rating. RESULTS: The tarsal conjunctiva showed a significantly different degree of lid redness between the MPDSs at the 2-hour visit (P < 0.05, Kruskal-Wallis test), being lower for COMPLETE RevitaLens compared to the other two MPDSs (Mann-Whitney U test). Furthermore, a significantly different degree of lid roughness at the 8-hour visit was seen (P < 0.05, Kruskal-Wallis test), being higher for Synergi (Mann-Whitney U test). The subjective comfort was similar with the three MPDSs. CONCLUSION: Tarsal conjunctival response should be also considered in the context of the clinical performance of MPDs at the ocular surface.