Lens Can Enhance Image Clarity
By Lee Rigel, OD, FAAO
Over 80 percent of subjects say the sports
vision lens performs equal to or better than to their standard lenses for sports.
SportSight GP lenses filter 100 percent of UV radiation below 400nm, a minimum of 99 percent of total UVA and UVB using Light Architecture Technology. This level of filtration exceeds the minimum requirements of various sunglasses and is beyond that of most contact lenses with standard UV absorbers. In addition, the lenses filter out a minimum of 77 percent of the visible light spectrum below 500nm.
In a prospective, multi-center open-label, non-randomized protocol controlled study, nine sites enrolled patients who represent the general population of current gas permeable contact lens wearers. Some 66 subjects were enrolled, treated and completed this protocol. Subjects wore the SportSight lenses during daylight hours for outdoor sport activity or spectator events. They were asked to use the lenses three or four times during a two-week period for periods of two to eight hours. The lenses were not to be used for night driving. A follow-up examination was conducted two weeks after dispensing the lenses.
Investigators ordered the new lenses from the same laboratory as the original standard lenses and made in the identical parameters. Lenses were inspected by the laboratory and investigator to determine that they conformed to the specification of the original prescription.
During the dispensing visit, subjects completed a standardized questionnaire. The lenses were dispensed and evaluated on eye, and the subjects received instructions on the prescribed wearing of the lenses. Subjects were told to use the same care products used with their standard lenses.
SportSight GP Lenses
Inherent performance advantages of the SportSight lens are provided through filtration of specific wavelengths, such as improved image clarity and definition by reducing haze and glare from refractive elements within the eye, and reduced chromatic aberration. Experts consider that such improvement relates to visual skills such as depth perception, anticipation timing and eye-hand-body coordination.
Prior research has shown that blue light filtration results in improved reaction time, as well as improved depth perception and contour recognition. This new technology provides unique sculpting of light transmission in the peak region of visual sensitivity (500nm to 600nm), aiding in target identification by making the object visually stand out from its background. The SportSight GP lens is based on this technology and is targeted for use in daylight sport and spectator activities.
Findings at Baseline and Dispensing
Some 39 of the 66 subjects were female and 27 were male. The mean age was 38 years with the youngest subject age 12 and the oldest age 66. Table 1 reports the descriptive statistics for the baseline demographics and clinical measures.
TABLE 1: Baseline Characteristics of Cohort
|N = 132 EYES
Table 2 reports statistics for the lens parameters used in the clinical trial.
TABLE 2: Parameters of Study Lenses in the Clinical
|N = 132
The analysis of the questionnaire responses revealed differences that proved statistically significant (p<0.05). The mean of the responses for the SportSight GP lens was higher for vision for sports than was the mean of the rating for the standard lenses. Four subjects did not respond to this question because they did not participate in a sport or spectator activity during the two weeks but did wear their lenses for general outdoor activity.
To test the reliability of the questionnaire, baseline ratings for the standard lenses were compared to the two-week ratings for the same standard lenses.
At the two-week visit, the mean of the ratings for sports vision was lower for the standard lenses than it was at the baseline visit for the same lenses. Subjects appeared to appreciate the visual performance of their standard lenses less for sports vision.
The anatomic clinical measures of horizontal K reading, horizontal visible iris diameter, upper lid position and pupil size were studied for their influence on the questionnaire responses of vision while participating in sports.
For the change in the rating of vision while participating in sports, variations in the anatomic variables accounted for 10 percent of the variation in the reported performance.
The anatomic variables having the greatest effect were the HVID (horizontal visible iris diameter) and the horizontal keratometry reading. Subjects with smaller and flatter corneas tended to report a greater increase in their rating of sports vision performance with the new lens than with their standard lenses.
The lens parameters of lens power, overall diameter, luminous transmission, base curve and optic zone were studied for their influence on the questionnaire response of vision while participating in sports activities.
Statistical analysis studied the effect of variation of the lens parameters on the change in rating. For the change in the rating of vision while participating in sport activities, variations in the lens parameters accounted for eight percent of the variation in the reported performance. The lens parameter variable having the greatest effect on sports vision was the base curve. Subjects with flatter base curves tended to report a greater increase in their rating of sports vision performance with the SportSight GP lens than with their standard lenses.
Variation in luminous transmission did not demonstrate any significance as a predictor of visual performance. Variation in the luminous transmission of the lenses used in the study across the cohort did not result in a significant change in the questionnaire response. This observation is impressive given the range of luminous transmission values seen. The range of luminous transmission was the result of the various lens power and lens thickness combinations.
Light transmission of SportSight GP lens.
The percentage of subjects that preferred the study lenses, standard lenses or neither for sports was determined by tabulating the number of subjects that reported a higher response, equal or lower response with the study lenses compared to the standard lenses. Some 62 subjects rated both their standard lenses and the study lens for sports: 29 (47 percent) preferred the SportSight GP lens for outdoor sports vision and spectator activities, 23 (37 percent) rated the SportSight GP lens equal to their standard lens and 10 (16 percent) preferred their standard lenses for outdoor sports vision and spectator activities.
Discussion and Conclusion
The study data indicated that nearly a three times greater number of subjects (47 percent) preferred the SportSight GP lens for sport activities than those preferring their standard lenses (16 percent). Results also indicated that SportSight GP lenses perform equal to or better than standard lenses while performing sport activities (84 percent). The mean of the rating with study lenses is greater to a statistically significant degree than the mean for standard lenses.
Those subjects that rated their standard lenses better than their study lenses (16 percent) were asked to comment on a reason for their preferences. The responses indicated three issues: difficulty going indoors with the study lenses on eye, cosmetic appearance of the lens, and the general category of "visual noise." Some subjects reported the study lenses allowed light around the edge of the lens and caused variation of vision on the blink.
It is the impression of the investigators that there are clinical strategies for problem solving when subjects report variation in vision upon blinking or the presence of light "leaking" around the lens. The investigator group reported a recommended strategy of increasing optic zone diameter and reducing the intermediate and peripheral curve radii to reduce the reported phenomena. Further research may prove valuable to establish the effectiveness of this strategy for raising the overall level of satisfaction.
The study data also indicated that duplicating the parameters of the patient's standard use GP lenses is an effective and successful dispensing strategy.
SportSight GP appears to be a valuable adjunct to conventional use gas permeable lenses. This study indicates that the majority of subjects representing the general gas permeable contact lens wearing population preferred SportSight GP lenses when used for daytime outdoor sport and spectator activity.
The following practitioners served as investigators in the study: Jim Boucher, OD; Norman Leach, OD; Thomas Quinn, OD; Kevin Reeder, OD; John Schachet, OD; Thomas Hixson, OD; Pat Caroline, FAAO; John Rinehart, OD.
This study was sponsored by Paragon Vision Sciences.
References are available upon request. To receive references via fax, call (800) 239-4684 and request document #64. (Be sure to have a fax number ready.)
Dr. Rigel is in private practice in lansing, Mich. He is a fellow of the American Academy of Optometry and frequently participates in contact lens studies.
See P. 43 for additional study
Patient Questionnaire -- Study Lenses: Two Week
Patient Name __________________________________________________ Date _________________
1. A. What, if anything, do you like about this pair of study lenses?
B. What, if anything, do you dislike about this pair of study lenses?
2. On average, how many days a week did you wear your study lenses?
3. On average, how many hours a day did you wear your study lenses?
4. Please rate the study contact lenses and your regular contact lenses on the following:
Check only one box per line
with 10 being Excellent and 1 being Poor
Vision while participating in sport activities STUDY
10 9 8 7 6 5 4 3 2 1
Vision while participating in sport activities REGULAR
10 9 8 7 6 5 4 3 2 1
5. Did you rate your regular lenses as better than the study lenses? If so, please describe how the study
lens performance was worse.
Contact Lens Spectrum, Issue: September 2000