Ralph E. Gundel

Standardized rigid contact lens fitting protocol for keratoconus

Keratoconus is typically managed by a variety of rigid contact lens fitting techniques and lens designs. The two most fundamental fitting techniques are apical corneal touch (including divided or three-point touch) and apical clearance. In the course of designing a multi-center study of keratoconus patients, a standardized keratoconus fitting protocol was developed. All contact lens parameter options are uniform except for base curve and secondary curve radii, which are determined by interpretation of fluorescein patterns using the CLEK Study trial lens set and protocol. The initial trial lenss base curve is the average keratometric reading; sequentially steeper lenses are applied until definite apical clearance is observed. We have evaluated the feasibility of this standardized fitting protocol on 30 keratoconus patients. Our results suggest that we have developed a standardized contact lens fitting set and fitting protocol to simplify contact lens management in patients with mild to moderate keratoconus.

Variables affecting rigid contact lens comfort in the collaborative longitudinal evaluation of keratoconus (CLEK) study.

Purpose. To identify factors associated with rigid contact lens comfort in keratoconus. Methods. Baseline data from the 16 Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study clinical sites were analyzed for all patients wearing a rigid contact lens in their more severely keratoconic eye (as determined by steep keratometry). Corneal transplant patients, patients who did not wear a rigid contact lens in either eye, patients who did not wear a rigid lens in their worse eye, and patients with missing contact lens comfort data were excluded from the sample. A total of 751 eyes were included. Variables assessed included measures of disease severity, visual acuity through the patients’ habitual rigid contact lenses, contact lens wearing time, the apical fitting relationship of the contact lens, the degree of peripheral clearance, and the presence of corneal scarring and staining. Comfort was measured by asking the patients “In general, how comfortable are your contact lenses?” (1 = very comfortable through 5 = very irritating). Results. Measures of disease severity (steep keratometry and the first definite apical clearance lens) were not associated with lens comfort. There was no difference in self-reported contact lens comfort between patients fitted with apical touch vs. apical clearance. Patients with a peripheral clearance rating of “minimal unacceptable” (more common among patients with milder keratoconus) were approximately half as likely to report good contact lens comfort compared with patients with “average” peripheral clearance (unadjusted odds ratio, 0.39; 95% confidence interval, 0.19 to 0.79). There was no association between contact lens comfort and the other peripheral clearance ratings compared with ratings of average. Conclusions. There does not appear to be an association between decreasing patient-reported rigid lens comfort and increasing disease severity as measured by steep keratometry or first definite apical clearance lens in this sample. The apical fitting relationship (flat vs. steep) does not appear to be associated with patient-reported comfort. Minimal peripheral clearance may contribute to decreased rigid contact lens comfort in keratoconus.

Feasibility of fitting contact lenses with apical clearance in keratoconus.

ABSTRACT Despite the wide variety of rigid contact lens fitting philosophies for the visual correction of keratoconus, questions remain, including which approach—flat, divided support, or steep—contributes the most toward the preservation of a clear cornea. One goal of the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Pilot Study was to determine the feasibility of managing early keratoconus patients with apical clearance rigid contact lenses. Of 30 keratoconus patients identified with at least 1 nonscarred cornea, 17 patients (30 eyes) were randomly assigned to a steep lens fitting protocol. After trial fitting with a standardized lens design demonstrating minimum apical clearance, lenses were dispensed whose base curve was 0.2 mm steeper than the minimum apical clearance lens. Patients were re-evaluated on a quarterly schedule concluding at 12 months. Changes in keratometry between baseline and 12 months identified unequal steepening of the flat and steep corneal curvatures, suggestive of corneal molding. Best corrected rigid lens visual acuity measures illustrated no significant changes over the course of the study. Clinically significant corneal compromise pleting the pilot study and fitted with apical clearance developed mild corneal scarring.

Parameter consistency in disposable lenses.

An evaluation of parameter consistency and edge defects as they might relate to premature lens fracture was undertaken for 2 disposable lens types, 50 Johnson & Johnson Acuvue lenses and 50 Wesley–Jessen FreshLook lenses. Diameter measurements varied from 13.97 to 14.48 mm (mean=14.28 mm, SD=0.138 mm) for Acuvue and 14.30 to 14.63 mm (mean=14.41 mm, SD=0.064 mm) for FreshLook. Based on previously reported information, these diameter variations for Acuvue may be sufficient to affect lens fitting characteristics. Calculated back surface sagittal depth varied from 3.27 to 3.38 mm (mean=3.32, SD=0.029 mm) for Acuvue and 3.68 to 3.87 mm (mean=3.75 mm, SD=0.039 mm) for FreshLook. Center thickness was generally consistent across the power range evaluated (–5.00 to –4.00 D) for the FreshLook lenses, and appeared to increase significantly for low minus powers for the Acuvue lenses. Twenty–one (44%) Acuvue lenses and 6 (12%) FreshLook lenses showed edge defects that might contribute to premature lens fracture.

Use of Acular LS in the Pain Management of Keratoconus: A Pilot Study

Purpose. The purpose of this pilot study was to determine the efficacy of ketorolac tromethamine 0.4% for pain management in conjunction with rigid gas permeable contact lenses in keratoconus. Any potential side effects and complications of this application were examined. Methods. A total of 12 current keratoconus patients who were presently experiencing discomfort or pain associated with their rigid gas permeables for keratoconus and/or who were contact lens-intolerant were identified from the existing patient population at the SUNY University Optometric Center. Symptomatic subjects were identified through positive feedback to a study Inclusion Questionnaire mailed to their homes. Subjects were treated on the basis of each eye separately in a modified monocular trial that spanned 5 weeks. After establishing that all inclusion and exclusion criteria were met, subjects were instructed to first use an unlabeled bottle of artificial tear solution (placebo) for 2 weeks, and then an unmarked bottle of ketorolac tromethamine 0.4% for 2 weeks in the designated eye. One drop was instilled twice a day, and the eye not assigned to take the drops served as the control. Subjects were monitored through weekly follow-up visits and repeated Keratoconus Symptom and Severity Questionnaires. Results. Responses from the Keratoconus Symptom and Severity Questionnaire were analyzed using a 2-factor Repeated Measures Analysis of Variance. Among the small subject subset, there was no statistically significant predilection for the ketorolac tromethamine 0.4% in managing the discomfort and pain associated with keratoconus. The artificial tear solution appeared to be equally effective in improving comfort. Conclusions. There was no conclusive result as to the efficacy of the ketorolac tromethamine 0.4% vs. the artificial tear solution in the pain management of keratoconus. This could be attributed to a number of physiological and situational factors, as well as small sample size.

Anterior hydrogel lens deposits: polished vs. unpolished surfaces.

Traditionally, lathe cut hydrogel lenses receive both back and front surface polishing to eliminate any surface irregularities that might serve as potential attachment sites for lens deposits or even microorganisms. However, with the advent of newer more technologically advanced lathing equipment, the need for lens polishing may require renewed justification. This study sought to compare, by scanning electron microscopy (SEM), anterior lens surface deposit formation on polished and unpolished 55% water hydrogel lenses. A total of 10 subjects wore in 1 eye (control) a lens with both front and back lens surfaces polished and on the other eye (test) a lens with only the back lens surface polished for a period of 2 weeks on a daily wear basis. Each lens was then scanned (using SEM), with 3 separate regions photographed at 30x using a 10 kV electron source. Using a Wilcoxon Signed-Ranks test on the differences between average deposit ratings for the polished and the unpolished lenses, by subject pair, we failed to reject the null hypothesis that the difference was zero.

Manual of Contact Lens Prescribing and Fitting

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Quantitative analysis of visual acuity through amber discolored lenses.

Discoloration of hydrogel contact lenses is frequently encountered in clinical practice and often precipitates lens replacement. This investigation sought to determine if lens discoloration was associated with a compromise in low or high contrast, high illumination visual acuity. This association would lead to a more scientific rationale for lens replacement. Amber lens discoloration was achieved using human-worn 55% water hydrophilic contact lenses (Methafilcon-A) heated in a 1% potassium sorbate, low pH saline solution. A spectrum of 6 discolored lenses was obtained with a peak absorbance at 320 nm. Fifteen subjects, between the ages of 22 and 38 years, were tested wearing each of the discolored lenses. None of the differences in high or low contrast acuity between our discolored and nondiscolored lenses were found to be statistically significant using a paired t-test at the 99% significance level.