LIPSON, MICHAEL J. OD, FAAO; SUGAR, ALAN MD, MS; MUSCH, DAVID C. PhD, MPH
Overnight corneal reshaping (OCR) or corneal refractive therapy (CRT) is a nonsurgical method of improving vision and decreasing dependence on glasses or traditional contact lenses. To compare patients’ experiences and preferences between OCR lenses and 2-week disposable soft lenses, currently the most commonly used mode of contact lens correction,1 we conducted a crossover study in which each subject wore each type of lens for 8 weeks.
The primary goal of this study was to evaluate subjects’ visual acuity, symptoms, and perceptions of vision-related quality of life with 2 different modes of vision correction. We also wanted to determine which mode of correction the subjects preferred. Additionally, the study’s outcomes yield a profile of patient characteristics that suggest which patients may be best satisfied with OCR and those who will prefer daily wear soft disposable lenses.
The instrument used in this study to evaluate subject rating of vision-related quality of life (QOL) was the NEI RQL-42.2 Other vision-related QOL instruments have been used in the past to evaluate vision-related QOL in spectacle wearers and in comparing spectacle or contact lens wear with refractive surgery.3–5 The NEI RQL-42 used in our study includes questions that are more pertinent to the lens-wearing modes in this study.
The study proposal and informed consent document were approved by the University of Michigan Institutional Review Board (IRB). Patients for this study were recruited from Kellogg Eye Center’s Ann Arbor and Livonia contact lens practices using promotional materials in professional multidisciplinary shared lobby/waiting areas, an e-mail newsletter distributed to university employees, a listing in a mailed university newsletter, and word of mouth referrals.
There was no charge for visits or lenses for subjects participating in this study. The initial examination gathered data regarding patient candidacy and baseline readings. The examination included: medical and contact lens history, manual keratometry, topography (Zeiss/Humphrey), pachymetry, subjective refraction (manifest and cycloplegic), Goldmann tonometry, dilated fundus evaluation, and unaided logarithm of the minimum angle of resolution (logMAR) acuity. LogMAR6–9 acuity throughout the study was measured at a 20-foot distance on the Bailey-Lovie wall chart at 40 to 48 lux illuminance. (This is rated as medium to low illumination, making the test more difficult than acuity testing in bright illuminance. This level approximates driving at dusk.)10,11
At the conclusion of the initial examination, the eligible subjects were presented with a written and a scripted oral presentation explaining the study. Patients were enrolled in the study if they satisfied all inclusion and exclusion criteria and signed the informed consent document. Subjects included in the study had the following characteristics: myopia: −.75 D to −4.25 D, astigmatism: <1.12 D, age: 18 to 40 years old, central K reading: 41.00 to 48.00, no soft lens wear 3 days before the study and no RGP wear 2 weeks before the study. Subjects excluded from the study were: those not correctable to 20/20, subjects who have had any prior corneal reshaping, those with corneal pathology such as keratoconus or severe dry eye, subjects who had any corneal or refractive surgery, subjects with significant cataract, and those with diabetes.
Subjects were randomly assigned by selecting one of 2 identical, opaque, and sealed envelopes to wear the daily-wear soft disposable lenses (SCL) or the overnight corneal reshaping lenses (OCR) first. Subjects in SCL were fit with Biomedics 55 (Ocular Sciences Inc., Concord, CA) 2-week disposable soft lenses to achieve best vision and comfort. In the OCR lens-wearing mode, subjects were fit with Paragon CRT (Paragon Vision Sciences, Mesa, AZ) lenses by the examiner (MJL) to achieve proper centration with a goal of plano refraction after lens removal. (Three subjects were fit with custom-designed lenses by Art Optical, Grand Rapids, MI. These lenses were made with a larger diameter [10.8–11.0] in Boston XO material to achieve optimal centration.) In each mode, lenses were changed as necessary during follow-up visits to achieve best fit and vision. Subjects wore each modality for 8 weeks after attainment of proper fit. For subjects wearing SCL first, subjects were asked to wear no contact lenses for a period of 3 days before beginning OCR wear. Subjects wearing OCR first were asked to discontinue lens wear for 2 weeks before initiating SCL (refraction must have returned to within .25 D of the original refraction). While in the OCR mode, subjects were seen at initial lens dispensing and for follow up after their first overnight wear, then at 1 week, 1 month, and 2 months. While in the SCL mode, subjects were seen at initial lens dispensing and again at 1 week, 1 month, and 2 months. Data gathered at OCR follow-up visits included: lens wear time, hours since removal, unaided visual acuity, slit lamp evaluation, subjective manifest refraction, and corneal topography. Data collected at SCL follow-up visits were: wearing time, visual acuity with SCLs, overrefraction, and slit lamp evaluation.
At the end of each 8-week phase of lens wear, subjects were asked to complete a 42-question survey about their experiences (the NEI’s RQL-42 Refractive Quality of Life Survey).2 This survey instrument has a standardized grading scale for 13 different attributes. Scoring is on a 0 to 100 scale in which 100 is the best and 0 is the worst. Statistical data analysis included the subjective patient responses on the RQL-42 questionnaire and the objective clinical data, visual acuity, and slit lamp findings. After the last visit, subjects were asked to choose the mode of correction they preferred to continue with after the study. The paired t test was used to analyze differences in the outcome measures collected during the 2 contact lens wear modes. Additionally, subjects were broken down into 2 groups, the group that chose OCR (the OCR preference group) and the group that chose the SCL (the SCL preference group). LogMAR differences are expressed as logMAR(OCR)−logMAR (SCL) (positive number indicates better vision with SCL, negative number indicates better vision with OCR). P values for comparisons of independent means were derived from the independent 2-tailed t test; for comparison of proportions, p values were derived from Fisher’s exact test (for race) the Pearson’s chi-square test (for SCL use and initial treatment). SPSS 12.0 software was used for all statistical comparisons.
Some preliminary results of this study have been presented previously.12 A total of 97 patients were seen for screening with 16 not meeting the study inclusion criteria. As a result, 81 patients enrolled, of whom 65 completed both phases and 16 dropped out of the study. Of the 16 patients who did not complete the study, one was the result of inability to insert/remove lenses of both types, one because of inadequate acuity with the soft lenses, 3 because of inadequate acuity with the OCR lenses, one as a result of discomfort with both modes, and 10 because of inability to keep follow-up appointments (5 during OCR and 5 during SCL). Subjects who dropped out were slightly more myopic than the whole study population (−3.22 D vs. −2.89 D) but showed no significant difference in age or ethnicity. A profile of subjects who participated in the study is listed in Tables 1 and 2. The profile represents a typical mildly to moderately myopic adult population. A total of 71.6% (n = 58) had previously worn soft lenses, 2.5% (n = 2) had worn RGP lenses, and 25.9% (n = 21) had no previous contact lens experience. Attaining best fit required an average of 2.2 lenses with SCL and 3.2 lenses with the OCR lenses.
With SCL, the mean logMAR acuity at the last follow-up visit was 0.06 with a standard deviation of 0.06, whereas the mean logMAR acuity with OCR at the last follow-up visit was 0.10 with a standard deviation of 0.11. The difference between the 2 modes of 0.04 (better acuity with SCL) was statistically significant (p value = 0.008). Subject ratings for the various attributes on the RQL-42 are included in Table 3 for the 65 subjects who completed both phases of the study. Statistically significant differences between OCR and SCL are highlighted and include: LogMAR acuity (better with SCL); activity limitations (better, less limited, with OCR); glare (less bothersome with SCL); symptoms, defined as itching, dryness, or lens awareness (less symptoms with OCR); and dependence on correction (less dependent on correction with OCR).
Breaking down preference mode by amount of original prescription (Table 4) shows: 1) The lower the subject’s refractive error at study entry, the higher the percentage that prefer OCR. Conversely, the higher the degree of myopia, the greater the likelihood that subjects would prefer SCL. In contrasting preferences in subjects whose refractive error was −2.87 D or less (n = 40) to those who were -3.00 D and above (n = 25), a Pearson’s chi-square test yields a result that is highly significant (p = 0.0002). 2) The majority (40 of 65; 61.5%) of our study population was mildly to moderately myopic (<−3.00 D).
Of the 65 completing both phases, 44 (67.7%) chose to continue with the OCR lenses (the OCR preference group)and 21 (32.3%) chose to stay with the soft lenses (the SCL preference group). Table 5 compares demographic and clinical differences between the OCR preference group and the SCL preference group. The OCR preference group was older by 3 years, had lesser original refraction, by approximately 1.2 D, steeper original K reading, by 0.7 D, showed less difference between logMAR visual acuity with OCR and SCL and, like would follow from lesser myopia, had better unaided vision at the initial examination.
Differences between the RQL-42 scores on OCR versus SCL for each preference group were calculated and analyzed. Statistically significant differences between the OCR preference group and the SCL preference group were evident in clarity of vision, glare, suboptimal correction, symptoms, and overall satisfaction and are shown in Table 6. For example, the OCR preference group rated their “clarity of vision” as 12.2 points higher with OCR than with the SCL, whereas the SCL preference group rated their “clarity of vision” as 23.6 points higher while wearing the SCL than with the OCR lenses Also, both groups rated glare as more bothersome with OCR lenses, but the SCL preference group found glare much less of a problem with SCL lenses. In contrast, both groups rated their symptoms less with OCR, but the OCR preference group rated their symptoms significantly less of a problem with OCR lenses than with SCL.
During the course of the study, in which 479 office visits occurred during a 15-month period, there were no adverse events (infection, ulcer, abrasion, and punctate staining beyond grade II).
Soft disposable lenses provide clear, comfortable vision correction for millions of wearers (approximately 33 million in the United States—nearly 12% of the U.S. population—representing approximately 50% of those who need vision correction between the ages of 18 and 34).1 Even so, many SCL wearers are not comfortable wearing lenses all day or for all activities. At the end of 2004, it was estimated that there were 50,000 OCR wearers (J. Jacobsen, personal communication, January 2005) in the United States. Previous studies have documented the corneal responses to OCR lenses13–18 and to soft disposable lenses.19–22 Soft disposable lenses have been used since the late 1980s, whereas Paragon’s CRT lens was granted U.S. Food and Drug Administration approval in June of 2002.23 Given the chance to experience these 2 modes of lens wear, two thirds of our study subjects preferred OCR lenses. This study population was mildly to moderately myopic. As such, these results must be considered relevant for such patients only.
The outcomes in this study show some definite differences between OCR and SCL wear. First, logMAR acuity with SCL was better than acuity with OCR. Even so, subjects’ rating of their vision was not significantly different between the 2 modes. Second, subjects felt less activity-restricted, had fewer symptoms of discomfort, and felt less dependent on correction while in the OCR mode but were more affected by glare while wearing the OCR lenses. It is apparent that subjects separate vision from comfort. As described in the “Results,” subjects who chose OCR rated their symptoms 20 points better (less symptoms) with OCR than with SCL. On the other hand, subjects choosing SCL rated their clarity of vision 23 points higher with SCL and glare 40 points better with SCL. Wavefront testing that is becoming standard in LASIK evaluations may explain some of the reasons for the glare/visual distortions.24–28 A recent study of higher-order aberrations in clinically successful OCR cases showed significant increases in third-order (coma-like) and fourth-order (spherical-like) aberrations.29 Their study concluded that the increases in higher-order aberrations correlated with the amount of the myopic correction. It would be very helpful to be able to predict which patients will be bothered by glare/aberrations before treatment, but this study’s data could not be used to make that distinction.
Comparing mean OCR results on the RQL-42 with the normative data2 shows close similarities on all attributes except “glare” (lower with OCR, 58.3 vs. 76.4 in the normative data or more bothersome with OCR), “symptoms” (better with OCR, 90.3 vs. 79.2 in the normative data), and “dependence on correction” (better with OCR, 94.6 vs. 42.3 in the normative study or less dependent with OCR). The SCL mean results showed very close correlation to normative data on all attributes.
Although SCL are easy to wear, both the SCL preference group and the OCR preference group rated their symptoms as better with the OCR lenses. Subjective choice in this study showed a majority (67.7%) choosing to continue with OCR lenses.
In comparing alternative modes of vision correction, one study compared RQL-42 scores for a group of patients with OCR (CRT) versus a group of patients undergoing LASIK. That study showed no significant vision-related quality-of-life differences between the 2 groups at 3 months after treatment.30 These data suggest that OCR may compete with or complement LASIK as a result of similar candidate profiles.31 Another study compared RQL-42 of OCR with silicone/hydrogel lenses worn for 30 days continuously32 showing a significant difference in the “dependence on correction” attribute (possibly because of the nature of the instrument questions). The other attributes did not show statistically significant differences.
Safety in various modes of contact lens wear is a serious consideration. In this study, there were no adverse events with OCR or SCL. However, the 8-week follow up in this study was not long enough to establish relative safety or frequency of adverse events with either mode of lens wear. Previous studies have evaluated risk of adverse events while wearing soft disposable contact lenses on a daily-wear basis.33 Estimates are between one in 1500 and one in 15,000 soft lens wearers per year having events of microbial keratitis. There have been no studies as to the incidence of microbial keratitis with OCR, although there are published case reports of these events34,35 that total 41 cases worldwide (7 in the United States and 34 in other countries).
The strengths of this study were: 1) It was a randomized crossover study in which each subject wore both modes, they were their own control. 2) The RQL-42 is a validated instrument and there are normative data for refractive quality-of-life attributes. 3) The study outcomes were subjective and patient-focused. 4) Investigator bias was minimized because most of the outcomes were based on the patient’s self-report, not on investigator evaluations. Also, there was equal sponsorship by the manufacturer of each mode of lens wear. One weakness of the study is that most patients attracted to the study stated they were interested in these “new” type lenses. Subjects may have been somewhat biased toward the OCR lens mode because of their interest in OCR or because of problems with their current lenses (a large majority previously wore SCL). Also, there was no cost to subjects for lenses in the study. Cost factors could influence patient preferences in a clinical practice setting. The study only dealt with subjects who had lower levels of myopia and therefore does not provide information on OCR versus SCL use in subjects with moderate to high myopia.
Visual acuity was good with both modes of lens wear but slightly better with SCL. However, this difference alone was not enough to determine overall preference. Our data show that of those subjects who experienced both modes of lens wear, 67.7% preferred OCR with a decreasing OCR preference as myopic refractive error increased. Lens preference is likely influenced by factors in addition to visual acuity. As the RQL-42 findings show, attributes like dependence on correction, glare, symptoms, and activity limitations differ between lens types and play a role in the patient’s overall assessment of their lens preference.
Study support provided by the University of Michigan–Kellogg Eye Center, Paragon Vision Sciences, Ocular Sciences Inc., Art Optical Contact Lens Inc., and Research to Prevent Blindness, Inc.
Michael J. Lipson
19900 Haggerty Rd. #111
Livonia, MI 48152
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