International contact lens clinic (New York, N.Y.)最新文献

Ultrasonic measurements of corneal thickness (CT) more than 25 points from a 6-mm diameter area of the central cornea were used to create computerized CT maps. Two subjects were evaluated in different sessions by topographical ultrasonic pachometry. The thickness values were stored as a two-dimensional array z(x,y), whose indices refer to positional coordinates x (in the nasal–temporal direction) and y (in the superior–inferior direction). Pachometric maps were then constructed by plotting thickness values against horizontal and vertical (x,y) position coordinates. Assisted computer interpolation between data points provides color-coded continuous pachometric maps. Data were processed and analyzed separately and an average map was also obtained for each subject. Goodness of fit for the average maps measured by coefficient of determination (r²) was very high in both examples (r² = 0.98 and r² = 0.99). Fitting standard error was 5.42 μm and 4.17 μm, respectively. Also, points not measured in the ultrasonic evaluation could be automatically predicted from the fitted model. The technique described provides an affordable and reliable method for thickness mapping of full corneal tissue, enabling accurate anatomical evaluation of the changes induced in the cornea by refractive surgery procedures, contact lenses, or disease.

The aim of this study was to quantify the complexity of contact lens (CL) fitting following penetrating keratoplasty (PKP).

The CL care of 40 eyes following PKP was analyzed retrospectively and compared to that of 40 age-matched and gender-matched controls. We evaluated the numbers of diagnostic and ordered rigid gas permeable (RGP) CLs, office visits for 6-month follow-up, best spectacle and RGP CL-corrected logMar visual acuities (VAs), and RGP CL success and complication rates. Post-PKP corneas required more diagnostic CLs (p = 0.009), ordered CLs (p = 0.0003), and office visits (p = 0.001) than did controls. Corrected logMAR VAs post-PKP improved from 0.31 ± 0.31 (mean ± SD) with spectacles (20/41) to 0.076 ± 0.19 (20/24) with RGP CLs (p < 0.0001). Controls logMAR spectacle and CL-corrected VAs were 0.0043 ± 0.12 (20/20) and −0.023 ± 0.058 (20/19), respectively (no significant difference, p = 0.096). Ninety percent of PKP eyes and 100% of controls were successful, and 30% of PKP and 12.5% controls had CL-related complications; these differences did not reach statistical significance.

Post-PKP eyes require more diagnostic CLs, ordered CLs, and professional office visits. They also have greater improvement of VAs with RGPs than normals compared to spectacles. CL wear post-PKP does not statistically increase the rate of CL complications or alter the success rate of CL wear.

One-day disposable contact lenses are experiencing rapid market growth in certain markets, such as the United Kingdom. Because of the huge numbers of lenses required to satisfy this modality of wear, both practitioners and patients need to be reassured about the quality of these products. Analysis of the accuracy and reproducibility of each of three currently available 1-day disposable lenses was conducted with respect to the following lens parameters: total diameter, back optic zone radius, center thickness, water content, and back vertex power. Fourteen of the 15 parameters measured (three lenses × five parameters per lens) were found to fall within ISO-defined tolerances. Reproducibility was similar for the three lens types and was considered clinically acceptable. Practitioners and patients can be confident that the current generation of 1-day disposable lenses can be relied on to give consistent ocular and visual performance.

Glassy corneal striae (GCS) are fine colorless lines that run parallel to each other in a vertical or near-vertical orientation in the central cornea near the level of Descemet’s membrane. It is postulated that GCS “brace” the stroma, thus adding stability to the cornea. The purpose of this study was to determine the incidence of GCS in patients with “normal” corneas and to determine whether a correlation exists between the presence of GCS and gender, age, iris color, or corneal astigmatism (toricity). Modified marginal retro-illumination biomicroscopy was used to evaluate the cornea for the presence of GCS. One hundred thirteen “normal” right corneas were evaluated for the presence of GCS. A total of 85.8% (97/113) of subjects in our study sample exhibited GCS. However, we were unable to establish a statistically significant correlation between the presence of GCS and gender, age, iris color, or corneal toricity.

Historically, rigid gas permeable (RGP) lens parameters have been determined through trial fitting. Nevertheless, practitioners would likely welcome the opportunity to empirically fit RGP lenses if they could be confident of the outcome. This clinical investigation sought to evaluate the potential success of empirically fitting 9.0 mm Polycon II lenses. Based on both objective and subjective outcomes, this study suggests that empirically fitting the larger 9.5 mm Polycon II design, in combination with a lid attachment approach, would yield greater initial patient satisfaction.

Discontinuation from contact lens wear has been cited as a contributing factor to the lack of growth of the contact lens market in North America. To determine the reasons and extent of abandonment from contact lens wear among patients from optometric practices, 4415 questionnaires were randomly mailed to patients from 16 practices in Quebec, Canada, and were returned as anonymous responses to the Centre for Contact Lens Research in Waterloo. Thirty-three percent (n = 1444) of the surveys were returned. After 5 ± 6 years of lens wear, 34% of patients had discontinued lens wear at least once. Of the patients who discontinued, 77% resumed wear and 48% of those discontinued a second time. Those who had discontinued were fitted at an older age (by approximately 2 years), were in the professional/health care/management occupation sector, and had a slightly lower myopic prescription. Before discontinuation, the wearing time of this group was approximately 1 day/week less than those continuing to wear lenses. Of the patients who had discontinued, 49% had been refitted at least once, and the primary reason for refitting was discomfort. The primary reasons for abandonment were discomfort, dryness, and red eyes. Improved comfort and relief of dryness were the primary factors that would improve contact lens wear for the group that had discontinued. Practitioners may be able to target specific patient groups with remedial measures to improve contact lens-wearing success.