ABSTRACT
PURPOSE: The efficacy of overnight wear of four types of reverse-geometry lenses was compared. The length of time needed to achieve correction and any adverse events that occurred during the course of the study were recorded. METHODS: In this prospective, randomized study, 60 subjects (18 to 35 years old) with refractive error between -1.00 to -4.00 D (cyl = -1.50) wore reverse-geometry lenses overnight only. All subjects were assigned a Rinehart Reeves lens in one eye, and subsets of 20 subjects were randomly assigned a Mountford BE, DreimLens, or Contex D Series 4 lens for the contralateral eye. Visits included baseline, dispensing, 1 day, 1 week, and 1 month. Biomicroscopy, unaided visual acuity, subjective refraction, best-corrected visual acuity at high and low contrast and high and low illumination, corneal topography, and subjective rating data were collected. RESULTS: Forty-six subjects completed the study. At 1 month, there were no significant differences between lens types in their effect on unaided visual acuity, subjective sphere, subjective cylinder, best-corrected visual acuity at high and low contrast at high illumination and low contrast at low illumination, apical corneal radius, corneal eccentricity, and subjective ratings. Between 1 week and 1 month, there was a significant improvement in subjective ratings of quality of day and night vision (p < 0.05) but no significant change in the objective measures. No significant ocular adverse events were observed during the trial. CONCLUSIONS: The lens types tested were all similarly effective in the reduction of myopic refractive error. Subjective ratings continued to improve after objective measures stabilized at 1 week. Overnight lens wear proceeded for 1 month without significant adverse reactions.
Subject(s)
Contact Lenses, Extended-Wear , Myopia/therapy , Prosthesis Design , Adult , Corneal Topography , Female , Humans , Male , Prospective Studies , Prosthesis Fitting , Treatment Outcome , Visual Acuity/physiologyABSTRACT
PURPOSE: Twelve volunteers participated in a study designed to measure the overnight corneal edema response with a variety of hydrogel contact lenses. During the study four subjects (5 eyes) experienced a contact lens related acute red eye (CLARE) reaction, which manifested as severe ocular pain, photophobia, corneal infiltration, and conjunctival hyperemia. An additional five subjects (7 eyes) developed corneal infiltrates only. Twelve eyes (of 9 subjects) showed no response. METHODS AND RESULTS: Upon microbiological examination of the contact lenses and storage solutions, gram-negative bacteria were isolated in large amounts. The bacteria were identified as Serratia marcescens, Pseudomonas putida, and Pseudomonas aeruginosa. Significantly greater numbers of bacteria were isolated from contact lenses of subjects who experienced CLARE than from the other subjects (P = 0.005) and from the contact lenses of subjects who experienced an adverse reaction (CLARE or infiltrates) than from the other subjects (P < 0.001). The contaminating bacteria are thought to have been introduced to the lens storage vials as a result of lens handling and subsequent failure to disinfect lenses. CONCLUSIONS: This study draws attention to the possible contribution of contaminated lenses and storage cases in contact lens related acute inflammation and specifically implicates gram-negative bacteria, in particular Pseudomonas spp. and Serratia spp., in the inducement of acute inflammatory reactions such as CLARE.
Subject(s)
Contact Lenses/adverse effects , Endophthalmitis/microbiology , Gram-Negative Bacterial Infections , Acute Disease , Adolescent , Adult , Corneal Edema/etiology , Equipment Contamination , Female , Gram-Negative Bacterial Infections/complications , Humans , MaleABSTRACT
Success in contact lens wear is often judged on the basis of patient "survival" rather than the achievement of satisfactory performance based on specific criteria. In 1971, Sarver and Harris defined a series of standards for successful polymethyl methacrylate (PMMA) lens wear which incorporated criteria for wearing time, comfort, vision, ocular tissue changes, and patient appearance. In this paper we propose a revision of these criteria based on current understanding of the ocular response to contact lens wear. These revised CCLRU (Cornea and Contact Lens Research Unit) standards for success are intended as realistic performance objectives, and can be applied in clinical trials to evaluate and compare the clinical performance of present and future rigid and soft contact lenses, worn for daily and extended wear.
Subject(s)
Contact Lenses, Extended-Wear/standards , Contact Lenses/standards , Humans , Patient SatisfactionABSTRACT
Eleven unadapted contact lens wearers wore a high (74%) water content hydrogel lens (Permaflex, CooperVision) of oxygen transmissibility Dk/Lav 14 x 10(-9) in one eye and a low (43%) water content hydrogel lens (Aquaflex Superthin) of Dk/Lav 4 x 10(-9) in the other eye under open-eye conditions for 8 h. After 8 h, average corneal edema for the lower water content lens was 7.9 +/- 2.6%, which was significantly more than that for the higher water content lens, 1.7 +/- 1.6%. Significantly fewer corneal striae and folds were also seen in the eyes wearing the higher water content lens. Subjective ratings of lens comfort were significantly better for the higher water content lens. Low water content positive power hydrogel lenses of the thicknesses used in this study place unacceptable hypoxic stress on the cornea and therefore should not be used for all-day wear.
Subject(s)
Contact Lenses, Hydrophilic/adverse effects , Corneal Edema/etiology , Adult , Humans , Oxygen ConsumptionABSTRACT
The oxygen transmissibilities (Dk/L) of a set of 48 contact lenses made from 8 different materials were measured by 4 laboratories. The L/Dk measurements from each laboratory were compared and correlated. Samples which were not masked with a fixed front surface aperture during measurement were corrected for edge effects. This paper shows that provided L/Dk is calculated for each lens using the same technique and Dk is derived using a graphical method of calculation, similar results can be obtained by all laboratories. However, the agreement was less good for materials of Dk greater than 70 x 10(-11) (cm2/s) (ml O2/ml x mm Hg).
Subject(s)
Contact Lenses , Oxygen , Materials Testing , Mathematics , Permeability , Polarography , Regression AnalysisABSTRACT
One of the main factors determining the comfort of a rigid contact lens is the shape of the edge. The comfort of four different contact lens edge shapes was assessed with four unadapted subjects in a randomized masked trial. Lenses with well rounded anterior edge profiles were found to be significantly more comfortable than lenses with square anterior edges. There was no significant difference in subjective comfort between a rounded and square posterior edge profile. The results suggest that the interaction of the edge with the eyelid is more important in determining comfort than edge effects on the cornea, when lenses are fitted according to a corneal alignment philosophy.
Subject(s)
Contact Lenses , Adult , Equipment Design , Eyelids/physiology , Female , Humans , Male , Random Allocation , SensationABSTRACT
The edema response over a 24-hour sleep/wake cycle of ten subjects wearing a rigid gas-permeable (RGP) lens in one eye and a hydrogel lens in the other was evaluated. Lenses that result in equivalent amounts of overnight edema were selected. There was no significant difference in the rates of deswelling during the initial hour. However, at three and five hours after eye opening, the amount of residual edema was greater in the eye wearing the hydrogel lens. We suggest that when an RGP lens provides the same closed-eye level of oxygen as a hydrogel lens, the greater tear exchange of the RGP lens will result in a greater open-eye oxygen supply, leading to less daytime edema. This suggests that the more complete deswelling we observed with RGP lenses can be attributed to a lower stimulus to open-eye swelling. Biomicroscopy, subjective vision, and patient comfort were also rated on waking and ten hours after eye opening. On eye opening there was significantly more back-surface debris (P = 0.01) with the RGP lenses. Patients wearing RGPs rated comfort as poorer and vision as better but only the latter attained statistical significance.