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Biomedical subjects

E S Bennett

Publications and source records attributed to E S Bennett.

10 recordsLinked to original sources
PubMed1992

Clinical evaluation of fitting presbyopic patients with contact lenses.

This clinical investigation was performed to determine the success of using a system designed as a flow chart to fit presbyopic patients with contact lenses. The value of this type of system is to provide practitioners with a simple step-by-step approach to fitting presbyopic patients and reducing the costs of several trial fitting sets. Patients were fit with monovision, simultaneous vision bifocal, alternating vision bifocal or diffractive bifocal contact lenses. The patients were fit first with monovision, and, if unsuccessful with this or any of the above lens designs, they proceeded to the next stage. Stage 2 used the simultaneous lens design, Stage 3 the alternating lens design and Stage 4 the diffractive lens design. Of the 22 patients enrolled in the study, 17 (77.3 percent) were successful through Stage 3 and 18 (81.8 percent) were successful through Stage 4. The first three stages are those proposed by Bausch & Lomb as the Presbyopic Fitting System. The Presbyopic Fitting System was found to be simple to follow and successful in fitting presbyopic patients.

Adult↗
PubMed1992

The effect of rigid gas permeable lens cleaners on lens parameter stability.

The introduction of fluoro-silicone/acrylate rigid lens materials has provided wearers with benefits that include, among others, enhanced surface wettability. However, several reports have associated these lens materials with lens power, base curve radius and center thickness changes over time, especially with long-term use of an abrasive cleaner. The purpose of this study was to evaluate the effect of abrasive and non-abrasive cleaners on these specific lens parameters. Twenty-four fluoro-silicone/acrylate lenses, 12 low minus and 12 high minus in power, were cleaned a total of 200 times each. Each lens was cleaned with one of-three different cleaners (1 non-abrasive and 2 abrasive) using one of two cleaning methods; palm of the hand or between the fingers (digital). Lens power was changed on 14/24 lenses (58.3 percent); the primary changes occurred with use of one of the abrasive cleaners. In addition, a slight reduction in center thickness was observed after abrasive cleaner use. Warpage occurred at a much higher rate with the digital cleaning method and with the use of an abrasive cleaner. It was concluded that practitioners should routinely reverify rigid lens power, center thickness and base curve radius; patients should be educated to carefully handle their lenses, notably cleaning them in the palm of the hand.

Contact Lenses↗
PubMed1992

The effect of modification procedures on rigid gas permeable contact lenses: the UM-St. Louis Study.

The purpose of this study is to evaluate the effect of frequently performed modification procedures on quality of vision, surface wettability, optical quality and subjective response. One subject was optimally fitted with both silicone/acrylate (S/A) and fluoro-silicone/acrylate (F-S/A) lens materials of identical design. Two methods of surface polishing, edge polishing and repowering were used in addition to three different spindle speeds. Each pair of lenses was worn by the subject for a period of 4 hours and the subjective response was then compared to the baseline or premodification data. In addition, both low magnification photography and Scanning Electron Microscopy (S.E.M.) were performed on each lens. The results showed that the addition of 0.50D minus power reduced visual acuity, contrast sensitivity function and optical quality with one of the methods used. Front surface polish and edge polish procedures did not appear to affect short-term performance. Controlling polish, application and tool pressure on certain procedures resulted in similar findings. Further studies would be beneficial to evaluate the effect of longer wearing periods and the use of other modification procedures. The authors conclude that S/A and F-S/A lens materials can be successfully modified in-office with adherence to recommended guidelines.

Contact Lenses↗
PubMed1990

How important are lens oxygen ratings? They are one of many performance factors.

To prevent corneal edema in most patients, contact lenses must transmit oxygen to the following minimum degree: (a) in daily wear, 24.1 x 10(-9) (cm x ml O2)/(s x ml x mm Hg), and (b) in extended wear, 34.3 x 10(-9) (cm x ml O2)/(s x ml x mm Hg). High Dk/L ratings are particularly important for patients wearing extended wear lenses and for those with exceptionally high corneal oxygen demand. Nevertheless, it is well known that other lens performance properties can be compromised by manipulating material or design parameters to increase the Dk/L rating. Increasing the Dk/L of hydrogel lenses, for example, may lead to problems such as fragility, dehydration, and corneal adherence. Similarly, high-Dk/L, rigid gas-permeable lenses may exhibit poor surface wettability and flexural resistance, base curve radius changes, and possible corneal adherence. Because such problems can compromise visual acuity, affect ease of handling, or decrease comfort, nonoxygen factors may exert a stronger influence on successful lens wear than high oxygen transmissibility alone for most patients. Among the nonoxygen factors important for contact lens wear are good movement, surface wettability, resistance to deposit buildup, and flexural resistance. Clinicians must consider these properties, along with oxygen transmission ratings, when fitting patients with contact lenses. Lenses that exhibit good overall performance, in my view, provide the greatest probability of successful wear.

Contact Lenses↗
PubMed1987

Clinical investigation of the Paraperm EW rigid gas-permeable contact lens.

Paraperm EW is a high oxygen flux silicone/acrylate rigid lens material currently under clinical investigation for extended wear. The purpose of this paper is to report the clinical findings after 12 months of a 2-year investigation of 18 patients fitted with this material. Fifteen were successfully wearing Paraperm EW lenses at 1 year. The only significant clinical finding was keratometric flattening at the 1-month visit. It was concluded that the Paraperm EW lens was durable, comfortable, and provided excellent visual acuity during the course of this investigation without inducing any of the ocular complications sometimes associated with extended wear of hydrogel lenses.

Adolescent↗
PubMed1987

Evaluation of endothelial integrity in extended wear.

The purpose of this investigation was two-fold: 1) to evaluate and compare the endothelium of hydrogel and rigid extended wear contact lens patients and 2) to evaluate a new technique for in-office endothelial photography. Endothelial photography was performed on seven patients who had worn low water content ultrathin soft lenses and seven patients who had worn rigid extended wear lenses for 1 year. In addition, seven non-lens wearers were used as a control group. Endothelial polymegathism and pleomorphic changes were evaluated via photographic observation using a new endothelial photography technique developed by G. Michael Murphy, O.D. The results showed that this was a viable method of endothelial photography for monitoring extended wear contact lens patients.

Conjunctival Diseases↗
PubMed1986

Hydrogel versus rigid gas permeable lenses for extended wear: criteria and differences.

The clinical investigation of several high oxygen flux lens materials has demonstrated that practitioners should soon have a viable alternative to hydrogel extended wear lenses. Practitioners can base their decision on several factors prior to selecting the appropriate lens. In many cases a rigid lens may be the appropriate alternative based on these factors.

Contact Lenses, Extended-Wear↗
PubMed1986

Rigid gas-permeable lens problem solving.

The introduction of high oxygen-permeable rigid lenses for daily wear has provided practitioners with an excellent alternative to other available lens materials. However, compromise in material properties may, in fact, result in lens-induced complications. This paper describes eight such "typical" problems including a treatment plan and possible alternative methods of treatment. A comprehensive summary table is provided for reference use by practitioners.

Contact Lenses, Extended-Wear↗
PubMedDate not supplied

Evaluation of variation in oxygen transmission in rigid contact lens extended wear.

Variation in thickness is known to affect the Dk/L of rigid gas permeable contact lenses. Our study was designed to evaluate the variability of central and average thickness of Oxyflow EW lenses. In addition, the relationship between overnight swelling of the central cornea and Dk/L was examined to determine whether Dk/L calculated with central lens thickness correlated better with lens-induced edema than Dk/L calculated with average lens thickness. The results showed marked variation among lens center thicknesses for all powers (-6 D, -2 D, +2 D, +6 D) examined, and, as expected, more variation for centrally calculated Dk/L with high minus lenses. Average Dk/L did not vary significantly with power. Average and central Dk/L values had a near 1:1 relationship for -2 D lenses for the base curve (7.8 mm) ordered; but only when power was kept constant was a good correlation seen between central and average Dk/L. A one-patient study evaluating the overnight central swelling response to three +6 D and three -6 D (high, medium, and low center thickness) lenses showed that central Dk/L correlated better with lens-induced edema than average Dk/L. Thus, specifying central thickness on lens orders appears to be a primary variable influencing extended wear edema at night. Peripheral Dk/L, however, may influence corneal physiological variables other than central edema and warrants further study.

Adult↗