The effect of add power on distance vision with the Acuvue Bifocal contact lens

Transcription

1 The effect of add power on distance vision with the Acuvue Bifocal contact lens David Ardaya, Giulia DeVuono, Ivy Lin, Annie Neutgens, Peter Bergenske, O.D., Patrick Caroline, O.D., and Jennifer Smythe, O.D., M.S. Pacific Universiv, College of Optometry. Forest Grove, Oregon Purpose: This study was designed to determine if subjective evaluation of quality of distance vision with the Acuvue Bifocal contact lens could be correlated with high and lowcontrast acuity scores. Methods: LogMAR visual acuities of 20 nonpresbyopic subjects were measured using high and lowcontrast BaileyLovie charts. Each subject wore an Acuvue Bifocal contact lens with add powers +I.00, t1.50, t2.00, and t2.50, each optimized for best distance acuity. Results: Subjects showed significantly decreased acuities with increasing add; a lowcontrast target heightened this effect. Subjects reported a reduction in quality of distance vision, increasing fluctuation, ghostingfshadows, and halos around lights that correlated with increasing add power. Conclusions: Our findings suggest that the Acuvue Bifocal contact lens may be expected to perform best for presbyopes with lowtomoderate bifocal add requirement, and that clinicians should anticipate decreased lowcontrast acuity and reduced overall quality of vision as add powers are increased. Key Words: Acuvue Bifocal, bifocal contact lenses, contact lenses, contrast acuity, multifocal contact lenses, presbyopia, visual acuitv Ardaya 0, OeVuono G, Lin I, et al. The effect of add power on distance vision with the Acuvue Bifocal contact lens. Optometry 2004;75: VOLUME 75/NUMBER 3lMARCH 2004 W ith four million Americans becoming presbyopic every year, the demand for multifocal contact lenses is at an alltime high.' In fact, the year 2000 saw contact lens wear among 40 to 64yearolds surpass all other age gr~ups.~ In response to the increased demand, various multifocal lens designs have been developed: diffractive, concentric, aspheric, and translating, among others. One of the mostfrequently prescribed bifocal contact lenses is the Acuvue Bifocal, a soft hydrophilic lens with a concentric multizone design that allows simultaneous distance and near ~iewing.~,~ Although the literature reports varying success rates for multifocal contact len~es,~~ a recent study reported only a 53% success rate with the Acuvue Bif~cal.~ The simultaneous correction of distance and near vision, while convenient, may result in decreased visual acuity and contrast sensitivity, as well as increased symptoms of halos and glare. More specifically, it has been clinically observed that patient satisfaction is compromised as the add power increases. Although generally accepted, limited attempts have been made to quantify this effect. Because the balance between distance and near vision is critical for a successful bifocal contact lens fit, an estimate of predicted reduction in distance vision with increasing add power would be helpful to clinicians. The purpose of this study was to demonstrate the effect of add power on both subjective and objective visual quality. It is important to note that our findings were obtained with nonpresbyopic subjects. As this study analyzed the effects on distance vision only, concern over the effects of accommodation were considered negligible. 169

2 Table. Mean Snellen denominator values Snellen denominator values I Day Acuvue Add Add Add Add Highcontrast Mean SD Lowcontrast Mean SD SD, Standard dev~at~on Methods Subjects 'henty optometric students between the ages of 23 and 31, all current soft contact lens wearers, served as subjects. All subjects had less than 0.75 D of astigmatism and their refractive errors fell within the available parameters of the Acuvue Bifocal lens. All subjects had undergone a complete eye examination within the last 12 months and were deemed free of ocular or systemic conditions that would contraindicate contact lens wear. In order to be eligible, subjects were required to achieve distance visual acuities of or better with 1Day Acuvue soft contact lenses. All subjects were myopic, with refractive errors ranging from 0.75 to Before participation in the study, each subject was required to provide written consent. Design All trials in this study were performed monocularly. An overrefraction of the patients' habitual lenses provided their initial correction for the test lenses. The fit of the 1Day Acuvue was assessed after 10 minutes of equilibration, after which high and lowcontrast distance visual acuities were measured with a standard BaileyLovie chart at 6 meters under standard room illumination. This test distance was chosen to simulate optical infinity, as the intent was to evaluate distance vision only, and these subjects were not presbyopic. These conditions were constant for all trials. A similar procedure was followed for the bifocal lenses. Subjects were fitted and evaluated with each Acuvue Bifocal (+ 1.00, , +2.00, and adds) in a randomized, doubleblind fashion. To ensure that no lenses were worn inside out, an examiner viewed the inversion marks on each lens with the biomicroscope before equilibration and testing. After equilibration, highcontrast visual acuities were taken. If a 0.25 D lens improved highcontrast visual acuity by 2 or more letters, a new lens was dispensed in the new power and allowed to equilibrate. Thus, highcontrast distance acuity was optimized for each add power before final acuity measures. This protocol adheres to the Acuvue Bifocal fitting guide, and most closely resembles clinical practice. Lowcontrast visual acuities were then measured through the optimized lens (or the original lens, if no change was indicated). In addition, subjects were required to complete questionnaires regarding the visual quality of each optimized lens. Subjects were asked to rate characteristics of the lenses, such as handling, comfort, overall vision, fluctuation of vision, ghosting/halos, etc. on a scale of 1 to 50, with 50 being 'ideal' (see Appendix). Materials The 1Day Acuvue lens was selected for baseline measures because it shares similar features with the Acuvue bifocal, such as the 8.5mm base curve and a 14.2mm diameter. The 1Day Acuvue is a spherical, singlevision soft contact lens, available in powers ranging from D to D. The Acuvue Bifocal is a concentric center distance design with five alternating zones. It also has an inversion indicator of " 1 2 3" on the front surface. The Acuvue Bifocal is available from D to 9.00 D, with add powers of , , , and Both lenses are made of etafilcon A, with 58% water content and Dk of Results Measures of logmar acuities showed highly significant differences across all viewing conditions, as shown in the Table. Differences in mean VOLUME 751NUMBER 3/MARCH 2004

3 C L I N I C A L RESEARCH I I. Discussion. j HIGH CONTRAST LOW CONTRAST / figure 1 Decrease in Snellen acuity with increased add power., IAmnl 2 showed no statistical sinnifi. cance were overall comfort and overall handling, as anticipated. However, subjects' ratings of distance vision, fluctuating vision, ghostinglshadows, and halos around lights indicated a significant decline in subjective assessment of quality of vision as add power increased (p < 0.000). Figure 2 provides a summary of the mean subjective ratings. With an evergrowing number of the population becoming presbyopic, it is increasingly important for the clinician to successfully fit bifocal contact lenses. While many patients may favor contact lenses for their convenience and cosmesis, proper patient selection/screening is essential for wearing success. Clinically, it is commonly held thatcompared to a spectacle correctionboth visual performance and task performance are often compromised with simultaneous vision contact l e n ~ e s. ~Our ' ~ study measured both the quality of vision and visual acuity for increasing add powers when compared to a standard singlevision lens. Distance vision, fluctuating vision, ghostinglshadows, ~ O r ~ and I halos around lights were all I Decreasein subjective rating of quality of vision with increasing add power. rated lower as add power increased. Subjective assessment monoc.ular logmar acuities were significant of quality of distance vision showed the greatest between the singlevision 1Day Acuvue and each decline from a mean rating of 39 (1Day Acuvue) of the four bifocal powers (repeatedmeasures to 19.6 (+2.50 add). analysis of variance [ANOVA], N = 20, p < 0.000). In addition, differences were significant Our objective findings validated the patients' among lenses of the same power between highsubjective assessments. Compared to the acuity and lowcontrast levels (N = 20, p < 0.000). Figachieved with the 1Day Acuvue, subjects ure 1shows the linear decrement in Snellen acuexperienced a reduction in distance acuity of 0.7 ity as add power increases for both contrast levels. to 2.3 LogMAR units under highcontrast conditions with the Acuvue Bifocal. The decrease Statistically significant differences were found for in distance acuity was amplified when tested four of the six subjective measures. The two that with lowcontrast lettering. The lowcontrast dis~. ~ VOLUME 75lNUMBER 3lMARCH 2004 ~ m M 0 ~

4 tance acuity reduction ranged from 1.3 to 3.6 lines. It is important to note that our findings were obtained with nonpresbyopic subjects. Agerelated changes in the eyesmost notably cataractswould decrease contrast sensitivity even further, possibly leading to more visual syrnptoms.l1j3 Clinicians should be aware that distance vision appears to worsen in simulated nighttime condition^.^,^ We confirmed that lowcontrast conditions exaggerate the effect on both acuity and subjective perception of vision quality. Our study used monocular measures; one would expect superior visual acuities in a clinical setting due to binocularity.1 Benefits of a simultaneous vision contact lens include stereopsis similar to that with a spectacle c~rrection,'~ and better stereopsis and near task performance than with monovision or modified monovision.14 One study found that after 8 weeks of adaptation, presbyopic patients showed improved near task performance, despite unchanged acuities and stereopsis.15 Therefore, it seems that with time patients can adapt to functioning with their reduced acuity. Our subjects were not presbyopic and were only allowed a minimal adaptation time. Results with adapted presbyopic subjects would need to be determined to further explore the effects we found. Success rates are dependent on proper patient selection and patient motivation. Anecdotal reports indicate as much as a 20% increase in satisfaction rate with the lens after moddymg patient selection criteria.16 Higher fitting success rates may be accomplished if the following ideas are taken into account: 1. Visual acuity decreases with increasing add power; therefore, patients who require or tolerate a lower add power may be more satisfied with these lenses. 2. Visual acuity will show an even greater decrease with lowcontrast targets or in dim illumination; therefore, an older presbyope's visual system may be compromised more than that of a younger presbyope. 3. Fluctuating vision, ghosting, and halos are all significantly correlated with increasing add power; therefore, educating the patient that these are normal side effects associated with the lens may increase acceptance. However, despite the subjective and objective decreases in visual performance, the Acuvue Bifo 172 cal contact lens provides the clinician with a muchneeded option for presbyopes. Acknowledgment and Disclaimer Dr. Bergenske is a paid consultant and clinical investigator for Vistakon, manufacturer of the Acuvue Bifocal. Dr. Smythe is a clinical investigator for Vistakon. None of the other authors has any financial or proprietary involvment with any of the companies or products used or referred to in this article. References 1. Barr J. Annual Contact Lens Report. Contact Lens Spectrum, January Zarrella L. Trends in contact lenses and lens care. B&L Annual Report to Vision Care Professionals, December Bergenske P. First impressions of a new disposable bifocal. Contact Lens Spectrum, September Barr J. Bifocals, multifocals, monovision: what works today. Contact Lens Spectrum, May Gussler CH, Solomon KD, Gussler JR, et al. A clinical evaluation of two multifocal soft contact lenses. CLAO J 1992;18: Shapiro MB and Bredeson DC. A prospective evaluation of Unilens soft multifocal contact lenses in 100 patients. CLAO J 1004;20: Key JE, Morris K, Mobley CL. Prospective clinical evaluation of Sunsoft Multifocal contact lens. CLAO J 1996; 22: Key JE and Yee JL. Prospective clinical evaluation of the Acuvue Bifocal contact lens. CLAO J 1999;25: Erickson P and Robboy M. Performance characteristics of a hydrophilic concentric bifocal contact lens. Am J Optom Physiol Opt 1985;62: Sheedy JE, Harris MG, Bronge MR, et al. Task and visual performance with concentric bifocal contact lenses. Optom Vis Sci 1991;68: Cox I, Apollonio A, Erickson P. The effect of add power on simultaneous vision, monocentric, bifocal, soft lens visual performance. ZCLC 1993;20: Kirschen DG, Hung CC, Nakano TR. Comparison of suppression, stereoacuity, and interocular differences in visual acuity in monovision and Acuvue Bifocal contact lenses. Optom Vis Sci 1999;76: Schwartz S. Visual perception: a clinical orientation, 2nd ed. Stamford, Conn.: Appleton and Lange, Collins M, Brown B, Bowman K. Shortterm responses to soft contact lens corrections for presbyopia. Clin Exp Optom 1989;72: Sheedy JE, Harris MG, Gan CM. Does the presbyopic visual system adapt to contact lenses? Optom Vis Sci 1993; 70~ Scheena L. 3 Contacts with clout. AAO EyeNet magazine, March Corresponding author: Peter D. Bergenske, O.D. Pacific University College of Optometry 2043 College Way Forest Grove, Oregon berg 1 IOl@pacificu.edu VOLUME 75lNUMBER 3/MARCH 2004

5 Appendix Subjective questionnaires used to evaluate lens performance. Subject: Lens: OVERALL COMFORT u EXCELLENT DISTANCE VISION n OVERALL HAHDLXHG.. < u 40 GOOD OTHER, S PEW B!XIXR THAN <.. SATISFACTORY 30 < SATIFACTORY 20 < LESS THAN SATISFACTORY 10 = < POOR 0 < VERY POOR VOLUME 75lNUMBER 3lMARCH 2004

6 Subject: Lens: RATING OaOsTmO OR 8HAWW8 0 < DONT NOTICE AT ALL IUU#) momm uahm u FLVCTOATIllO VISIOIW < 0 NOTICE, BUT NOT BOTHERSOME v < NOTICE, A LITTLE BOTHERSOME <. BOTHERSOME < BAD ENOUGH I WOULD NOT WEAR IMPAIRS VISION < < DEFINITELY IMPAIRS VISION VOLUME 75lNUMBER 3lMARCH 2004