- Email: [email protected]
The effect of add power on distance vision with the Acuvue Bifocal contact lens
CLINICAL RESEARCH
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 low-contrast acuity scores. Methods: LogMAR visual acuities of 20 non-presbyopic subjects were measured using high and low-contrast Bailey-Lovie 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 low-contrast 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 low-to-moderate bifocal add requirement, and that clinicians should anticipate decreased low-contrast 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;75:169-74.
ith four million Americans becoming presbyopic every year, the demand for multifocal contact lenses is at an all-time high.' In fact, the year 2000 saw contact lens wear among 40- to 64-year-olds surpass all . ~response to the increased demand, varother age g r ~ u p sIn ious multifocal lens designs have been developed: diffractive, concentric, aspheric, and translating, among others. One of the most-frequently prescribed bifocal contact lenses is the Acuvue Bifocal, a soft hydrophilic lens with a concentric multi-zone design that allows simultaneous distance and near ~ i e w i n g . ~ , ~
W
Although the literature reports varying success rates for -~ study reported only multifocal contact l e n ~ e s ,a~recent a 53% success rate with the Acuvue B i f ~ c a lThe . ~ 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 non-presbyopic subjects. As this study analyzed the effects on distance vision only, concern over the effects of accommodation were considered negligible. 169
V O L U M E 7 5 / N U M B E R 3 l M A R C H 2004
OPTOMETRY
C L I N I C A L RESEARCH
Table. Mean Snellen denominator values Snellen denominator values I-Day Acuvue High-contrast
Mean
SD Low-contrast
Mean SD
+
1.00 Add
+
1.50 Add
+ 2.00
+ 2.50
Add
Add
20.66 4.85 35.65 6.92
22.75 4.34 44.16 8.84
26.37 6.61 48.09 6.88
29.51 6.06 60.68 6.93
17.54 3.41 26.49 3.74
SD, Standard dev~at~on
Methods
In order to be eligible, subjects were required to achieve distance visual acuities of 20120 or better with 1-Day Acuvue soft contact lenses. All subjects were myopic, with refractive errors ranging from -0.75 to -5.50. Before participation in the study, each subject was required to provide written consent.
out, an examiner viewed the inversion marks on each lens with the biomicroscope before equilibration and testing. After equilibration, high-contrast visual acuities were taken. If a -0.25 D lens improved high-contrast visual acuity by 2 or more letters, a new lens was dispensed in the new power and allowed to equilibrate. Thus, high-contrast 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. Low-contrast 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).
Design
Materials
All trials in this study were performed monocularly. An over-refraction of the patients' habitual lenses provided their initial correction for the test lenses. The fit of the 1-Day Acuvue was assessed after 10 minutes of equilibration, after which high- and low-contrast distance visual acuities were measured with a standard Bailey-Lovie 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.
The 1-Day Acuvue lens was selected for baseline measures because it shares similar features with the Acuvue bifocal, such as the 8.5-mm base curve and a 14.2-mm diameter. The 1-Day Acuvue is a spherical, single-vision soft contact lens, available in powers ranging from + 6.00 D to -12.00 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 + 6.00 D to -9.00 D, with add powers of + 1.00, + 1.50, + 2.00, and +2.50. Both lenses are made of etafilcon A, with 58% water content and Dk of 28.0.
A similar procedure was followed for the bifocal lenses. Subjects were fitted and evaluated with each Acuvue Bifocal ( + 1.00, + 1.50, +2.00, and + 2.50 adds) in a randomized, double-blind fashion. To ensure that no lenses were worn inside-
Measures of logMAR acuities showed highly significant differences across all viewing conditions, as shown in the Table. Differences in mean
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.
Results
VOLUME 751NUMBER 3/MARCH 2004
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 ever-growing 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 that-compared to a spectacle correction-both 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 single-vision 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 single-vision 1-Day Acuvue and each decline from a mean rating of 39 (1-Day Acuvue) of the four bifocal powers (repeated-measures 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 low-contrast levels (N = 20, p < 0.000). Figachieved with the 1-Day 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 high-contrast 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 low-contrast lettering. The low-contrast dis~
- -- .
- ~ --
VOLUME 75lNUMBER 3lMARCH 2004
-
~
m
M
-0
--
~
OPTOMETRY
CLINICAL RESEARCH
tance acuity reduction ranged from 1.3 to 3.6 lines.
cal contact lens provides the clinician with a much-needed option for presbyopes.
It is important to note that our findings were obtained with non-presbyopic subjects. Agerelated changes in the eyes-most notably cataracts-would decrease contrast sensitivity even further, possibly leading to more visual syrnptoms.l1J3Clinicians should be aware that distance vision appears to worsen in simulated night-time condition^.^,^ We confirmed that low-contrast conditions exaggerate the effect on both acuity and subjective perception of vision quality.
Acknowledgment and Disclaimer
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 and better stereopwith a spectacle c~rrection,'~ sis 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 low-contrast 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-
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 200 1. 2. Zarrella L. Trends in contact lenses and lens care. B&L Annual Report to Vision Care Professionals, December 2001. 3. Bergenske P. First impressions of a new disposable bifocal. Contact Lens Spectrum, September 1998. 4. Barr J. Bifocals, multifocals, monovision: what works today. Contact Lens Spectrum, May 2003. 5. Gussler CH, Solomon KD, Gussler JR, et al. A clinical evaluation of two multifocal soft contact lenses. CLAOJ 1992;18:237-9. 6. Shapiro MB and Bredeson DC. A prospective evaluation of Unilens soft multifocal contact lenses in 100 patients. CLAO J 1004;20:189-91. 7. Key JE, Morris K, Mobley CL. Prospective clinical evaluation of Sunsoft Multifocal contact lens. CLAO J 1996; 22: 179-84. 8. Key JE and Yee JL. Prospective clinical evaluation of the Acuvue Bifocal contact lens. CLAO J 1999;25:218-21. 9. Erickson P and Robboy M. Performance characteristics of a hydrophilic concentric bifocal contact lens. Am J Optom Physiol Opt 1985;62:702-8. 10. Sheedy JE, Harris MG, Bronge MR, et al. Task and visual performance with concentric bifocal contact lenses. Optom Vis Sci 1991;68:537-41. 11. Cox I, Apollonio A, Erickson P. The effect of add power on simultaneous vision, monocentric, bifocal, soft lens visual performance. ZCLC 1993;20:18-21. 12. 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;76:832-7. 13. Schwartz S. Visual perception: a clinical orientation, 2nd ed. Stamford, Conn.: Appleton and Lange, 1999. 14. Collins M, Brown B, Bowman K. Short-term responses to soft contact lens corrections for presbyopia. Clin Exp Optom 1989;72:40-5. 15. Sheedy JE, Harris MG, Gan CM. Does the presbyopic visual system adapt to contact lenses? Optom Vis Sci 1993; 70~482-6. 16. Scheena L. 3 Contacts with clout. AAO EyeNet magazine, March 2001. Corresponding author: Peter D. Bergenske, O.D. Pacific University College of Optometry 2043 College Way Forest Grove, Oregon 971 16
berg [email protected]
172
OPTOMETRY
V O L U M E 7 5 l N U M B E R 3 / M A R C H 2004
C L I N I C A L RESEARCH
Appendix Subjective questionnaires used to evaluate lens performance.
Subject: Lens:
OVERALL COMFORT
DISTANCE VISION
OVERALL HAHDLXHG
u
EXCELLENT
n
u
.. 40
--
-
-
-
OTHER, S P E W
<----
GOOD
<-.-.
B!XIXR THAN SATISFACTORY
30
-
20
<----
SATIFACTORY
<----
LESS THAN SATISFACTORY
<----
POOR
<----
VERY POOR
-
-
-
10
=-
-
0
VOLUME 75lNUMBER 3lMARCH 2004
OPTOMETRY
C L I N I C A L RESEARCH
Subject:
Lens: RATING <----
OaOsTmO OR 8 H A W W 8
IUU#)
momm uaHm
FLVCTOATIllO VISIOIW
v
0
u
DONT NOTICE AT ALL
<----
NOTICE, BUT NOT BOTHERSOME
0 NOTICE, A LITTLE BOTHERSOME <----
BOTHERSOME <---.
BAD ENOUGH I WOULD NOT
WEAR <----
IMPAIRS VISION <----
DEFINITELY IMPAIRS VISION <---
OPTOMETRY
V O L U M E 7 5 l N U M B E R 3 l M A R C H 2004
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 low-contrast acuity scores. Methods: LogMAR visual acuities of 20 non-presbyopic subjects were measured using high and low-contrast Bailey-Lovie 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 low-contrast 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 low-to-moderate bifocal add requirement, and that clinicians should anticipate decreased low-contrast 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;75:169-74.
ith four million Americans becoming presbyopic every year, the demand for multifocal contact lenses is at an all-time high.' In fact, the year 2000 saw contact lens wear among 40- to 64-year-olds surpass all . ~response to the increased demand, varother age g r ~ u p sIn ious multifocal lens designs have been developed: diffractive, concentric, aspheric, and translating, among others. One of the most-frequently prescribed bifocal contact lenses is the Acuvue Bifocal, a soft hydrophilic lens with a concentric multi-zone design that allows simultaneous distance and near ~ i e w i n g . ~ , ~
W
Although the literature reports varying success rates for -~ study reported only multifocal contact l e n ~ e s ,a~recent a 53% success rate with the Acuvue B i f ~ c a lThe . ~ 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 non-presbyopic subjects. As this study analyzed the effects on distance vision only, concern over the effects of accommodation were considered negligible. 169
V O L U M E 7 5 / N U M B E R 3 l M A R C H 2004
OPTOMETRY
C L I N I C A L RESEARCH
Table. Mean Snellen denominator values Snellen denominator values I-Day Acuvue High-contrast
Mean
SD Low-contrast
Mean SD
+
1.00 Add
+
1.50 Add
+ 2.00
+ 2.50
Add
Add
20.66 4.85 35.65 6.92
22.75 4.34 44.16 8.84
26.37 6.61 48.09 6.88
29.51 6.06 60.68 6.93
17.54 3.41 26.49 3.74
SD, Standard dev~at~on
Methods
In order to be eligible, subjects were required to achieve distance visual acuities of 20120 or better with 1-Day Acuvue soft contact lenses. All subjects were myopic, with refractive errors ranging from -0.75 to -5.50. Before participation in the study, each subject was required to provide written consent.
out, an examiner viewed the inversion marks on each lens with the biomicroscope before equilibration and testing. After equilibration, high-contrast visual acuities were taken. If a -0.25 D lens improved high-contrast visual acuity by 2 or more letters, a new lens was dispensed in the new power and allowed to equilibrate. Thus, high-contrast 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. Low-contrast 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).
Design
Materials
All trials in this study were performed monocularly. An over-refraction of the patients' habitual lenses provided their initial correction for the test lenses. The fit of the 1-Day Acuvue was assessed after 10 minutes of equilibration, after which high- and low-contrast distance visual acuities were measured with a standard Bailey-Lovie 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.
The 1-Day Acuvue lens was selected for baseline measures because it shares similar features with the Acuvue bifocal, such as the 8.5-mm base curve and a 14.2-mm diameter. The 1-Day Acuvue is a spherical, single-vision soft contact lens, available in powers ranging from + 6.00 D to -12.00 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 + 6.00 D to -9.00 D, with add powers of + 1.00, + 1.50, + 2.00, and +2.50. Both lenses are made of etafilcon A, with 58% water content and Dk of 28.0.
A similar procedure was followed for the bifocal lenses. Subjects were fitted and evaluated with each Acuvue Bifocal ( + 1.00, + 1.50, +2.00, and + 2.50 adds) in a randomized, double-blind fashion. To ensure that no lenses were worn inside-
Measures of logMAR acuities showed highly significant differences across all viewing conditions, as shown in the Table. Differences in mean
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.
Results
VOLUME 751NUMBER 3/MARCH 2004
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 ever-growing 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 that-compared to a spectacle correction-both 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 single-vision 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 single-vision 1-Day Acuvue and each decline from a mean rating of 39 (1-Day Acuvue) of the four bifocal powers (repeated-measures 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 low-contrast levels (N = 20, p < 0.000). Figachieved with the 1-Day 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 high-contrast 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 low-contrast lettering. The low-contrast dis~
- -- .
- ~ --
VOLUME 75lNUMBER 3lMARCH 2004
-
~
m
M
-0
--
~
OPTOMETRY
CLINICAL RESEARCH
tance acuity reduction ranged from 1.3 to 3.6 lines.
cal contact lens provides the clinician with a much-needed option for presbyopes.
It is important to note that our findings were obtained with non-presbyopic subjects. Agerelated changes in the eyes-most notably cataracts-would decrease contrast sensitivity even further, possibly leading to more visual syrnptoms.l1J3Clinicians should be aware that distance vision appears to worsen in simulated night-time condition^.^,^ We confirmed that low-contrast conditions exaggerate the effect on both acuity and subjective perception of vision quality.
Acknowledgment and Disclaimer
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 and better stereopwith a spectacle c~rrection,'~ sis 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 low-contrast 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-
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 200 1. 2. Zarrella L. Trends in contact lenses and lens care. B&L Annual Report to Vision Care Professionals, December 2001. 3. Bergenske P. First impressions of a new disposable bifocal. Contact Lens Spectrum, September 1998. 4. Barr J. Bifocals, multifocals, monovision: what works today. Contact Lens Spectrum, May 2003. 5. Gussler CH, Solomon KD, Gussler JR, et al. A clinical evaluation of two multifocal soft contact lenses. CLAOJ 1992;18:237-9. 6. Shapiro MB and Bredeson DC. A prospective evaluation of Unilens soft multifocal contact lenses in 100 patients. CLAO J 1004;20:189-91. 7. Key JE, Morris K, Mobley CL. Prospective clinical evaluation of Sunsoft Multifocal contact lens. CLAO J 1996; 22: 179-84. 8. Key JE and Yee JL. Prospective clinical evaluation of the Acuvue Bifocal contact lens. CLAO J 1999;25:218-21. 9. Erickson P and Robboy M. Performance characteristics of a hydrophilic concentric bifocal contact lens. Am J Optom Physiol Opt 1985;62:702-8. 10. Sheedy JE, Harris MG, Bronge MR, et al. Task and visual performance with concentric bifocal contact lenses. Optom Vis Sci 1991;68:537-41. 11. Cox I, Apollonio A, Erickson P. The effect of add power on simultaneous vision, monocentric, bifocal, soft lens visual performance. ZCLC 1993;20:18-21. 12. 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;76:832-7. 13. Schwartz S. Visual perception: a clinical orientation, 2nd ed. Stamford, Conn.: Appleton and Lange, 1999. 14. Collins M, Brown B, Bowman K. Short-term responses to soft contact lens corrections for presbyopia. Clin Exp Optom 1989;72:40-5. 15. Sheedy JE, Harris MG, Gan CM. Does the presbyopic visual system adapt to contact lenses? Optom Vis Sci 1993; 70~482-6. 16. Scheena L. 3 Contacts with clout. AAO EyeNet magazine, March 2001. Corresponding author: Peter D. Bergenske, O.D. Pacific University College of Optometry 2043 College Way Forest Grove, Oregon 971 16
berg [email protected]
172
OPTOMETRY
V O L U M E 7 5 l N U M B E R 3 / M A R C H 2004
C L I N I C A L RESEARCH
Appendix Subjective questionnaires used to evaluate lens performance.
Subject: Lens:
OVERALL COMFORT
DISTANCE VISION
OVERALL HAHDLXHG
u
EXCELLENT
n
u
.. 40
--
-
-
-
OTHER, S P E W
<----
GOOD
<-.-.
B!XIXR THAN SATISFACTORY
30
-
20
<----
SATIFACTORY
<----
LESS THAN SATISFACTORY
<----
POOR
<----
VERY POOR
-
-
-
10
=-
-
0
VOLUME 75lNUMBER 3lMARCH 2004
OPTOMETRY
C L I N I C A L RESEARCH
Subject:
Lens: RATING <----
OaOsTmO OR 8 H A W W 8
IUU#)
momm uaHm
FLVCTOATIllO VISIOIW
v
0
u
DONT NOTICE AT ALL
<----
NOTICE, BUT NOT BOTHERSOME
0 NOTICE, A LITTLE BOTHERSOME <----
BOTHERSOME <---.
BAD ENOUGH I WOULD NOT
WEAR <----
IMPAIRS VISION <----
DEFINITELY IMPAIRS VISION <---
OPTOMETRY
V O L U M E 7 5 l N U M B E R 3 l M A R C H 2004