Comparison of multifocal and monovision soft contact lens corrections in patients with low-astigmatic presbyopia.

PURPOSE: The purpose of this study was to assess visual performance and patient satisfaction with two presbyopic soft contact lens modalities. METHODS: A crossover study of 38 patients with presbyopia was conducted. Patients were randomized first into either multifocal (Bausch & Lomb SofLens Multifocal) or monovision (SofLens 59) for 1 month. Visual performance was measured with high- and low-contrast visual acuity at distance and near and near stereoacuity. Patients' satisfaction was measured by the National Eye Institute Refractive Error Quality of Life Instrument questionnaire and by recording the patient's final lens preference. RESULTS: Patients maintained at least 20/20 binocular vision with both multifocal (MF) and monovision (MV) contact lenses under high-contrast conditions at distance and near. Under low-contrast conditions, patients lost less than a line of vision from the best spectacle correction to either multifocal or monovision contact lens correction at distance (pMF = 0.001, pMV = 0.006). Under low-contrast conditions at near, multifocal wearers lost five to six letters and monovision wearers lost two letters of vision (pMF < 0.001, pMV = 0.03, pMF/MV = 0.005). The average stereoacuity decreased by 79 s arc with monovision vs. multifocal contact lenses (p = 0.002). On the NEI-RQL, patients reported worse clarity of vision (pMF = 0.01, pMV < 0.001), more symptoms (pMF = 0.09, pMV = 0.01), and an improvement in their appearance with contact lens wear (pMF < 0.001, pMV < 0.001). Seventy-six percent of patients reported that they preferred multifocal contact lenses, and 24% preferred monovision contact lenses (p = 0.001). CONCLUSION: The majority of our patients preferred multifocals to monovision, most likely because the Bausch & Lomb SofLens Multifocal provides excellent visual acuity without compromising stereoacuity to the same degree as monovision.     

The effect of monovision lenses on the near-point range of single binocular vision.

Monovision (MV) contact lenses are commonly used to provide optical correction for presbyopia. Based on their review of the literature on fusional mechanisms, Erickson and Schor predicted that monocular blur associated with MV should not be sufficient to disrupt binocular fusion. We found that fusional vergence ranges in presbyopes corrected with MV were not substantially different from those measured under full binocular nearpoint correction. There were small but statistically significant tendencies for the phoria and base-in vergences to be less exo under MV conditions. Comparisons of findings between a group of successfully adapted MV patients and a group of patients who were unsuccessful with MV indicated no significant differences, suggesting that there is no adaptation effect for these performance variables and that these tests are not effective predictors of MV success.     

Evaluation of two new soft contact lenses for correction of presbyopia: the Focus Progressives multifocal and the Acuvue Bifocal

The clinical performance of Focus Progressives multifocal contact lenses and Acuvue Bifocal contact lenses was evaluated in a group of 42 presbyopes, with equal numbers of individuals having low, medium, and high spectacle add requirements. Following visual performance assessment with an optimal sphero-cylinder spectacle refractive correction, each individual wore each of the two types of contact lenses in successive random order. Each type of lens was used in a daily-wear mode for a period of 7 to 12 days, with follow-up and/or refitting visits occurring after 2 to 5 days, and again after 4 to 7 days of attempted wear. Testing for all three forms of refractive correction encompassed Snellen acuities at distance and near, Bailey-Lovie acuities under high and/or low ambient illumination conditions at near, intermediate, and far viewing distances, stereoacuity, a timed visuomotor task (needle threading), apparent glare/flare, and the nearwork range of subjectively clear binocular vision. The contact lenses also were evaluated for handling, comfort, distance and near ghosting, subjective visual quality, acceptability for common tasks (e.g., using a phone directory), and personal preferences.As might be expected, distance and near acuity, stereoacuity, and visuomotor task performance were somewhat better with sphero-cylinder spectacle correction than with either of the two types of contact lenses. However, several performance differences between the multifocal and bifocal lenses were noted. The Focus Progressives lenses provided significantly better distance acuity under both high and low illumination conditions, and received significantly higher ratings for visual quality (overall and at distance), comfort, and handling. The Focus Progressives lenses were preferred 5:1 over the Acuvue Bifocal lenses. No differences existed between the lenses with respect to near visual acuities, the perceived quality of the near vision, the nearpoint binocular range, stereoacuity, or the acceptability of vision for common nearwork tasks. The results suggest that although both types of lenses afford presbyopes a viable alternative to spectacles, the Focus Progressives lens is superior in many ways to the Acuvue Bifocal lens.     

Comparative visual performance of three presbyopic contact lens corrections.

We compared the visual performance of a soft diffractive (DIFF) bifocal contact lens, a near center (CN) concentric bifocal design, and monovision (MV), using a comprehensive vision testing protocol. Fifteen presbyopic subjects who were successfully wearing DIFF bifocal contact lenses participated in the study. Of the three systems tested, MV provided best visual acuity at distance and near; less than one line of acuity was lost relative to best spectacle acuity under all lighting and contrast conditions, and there was less disturbance of a point source of light. Both bifocal corrections gave similar visual acuity performance, with more lines of acuity lost relative to spectacles at near compared to distance. However, the concentric bifocal induced more ghosting at near than the other two systems. Stereopsis was compromised at distance with MV correction, but all systems performed worse than spectacles at near. An understanding of the strengths and weaknesses of presbyopic contact lens options allows the clinician to improve management of the presbyope who wishes to wear contact lenses.     

Short term responses to soft contact lens corrections for presbyopia

Eleven subjects were each fitted with five different soft contact lens corrections for presbyopia. The correction types were distance contact lenses with lookover spectacles, concentric bifocals, monovi-sion, modified monovision and progressive bifocal contact lenses. Subjects were asked to rate each contact lens correction in terms of distance, intermediate, near and peripheral vision, confidence when walking and climbing stairs, eye-hand co-ordination, performance on work tasks, vision difficulties in bright and dim ambient illumination and the correction most preferred for daily wear. There were few significant differences between ratings for the different corrections. Monovision, modified monovision and the concentric bifocal corrections were the preferred options for daily wear.     

The effect of monovision contact lens wear on driving performance

Background : A number of studies have highlighted the problems with driving reported by wearers of monovision contact lens corrections. In this study, we wished to investigate this further, by determining whether driving performance as measured on the open road under daytime conditions is worse when drivers wear their monovision contact lenses compared to their habitual correction. Methods : Thirteen subjects with healthy eyes and corrected visual acuity of 6/6 were selected. Each had worn monovision contact lenses for at least three months. All subjects had their driving performance assessed while driving their own vehicles on an open road course, with both monovision contact lenses and their other habitual correction (spectacles or unaided). Results : No statistically significant differences were found in driving performance when subjects wore their monovision contact lenses compared to when they wore their habitual distance correction. Conclusions : The results indicate that monovision does not adversely affect driving performance in daylight hours for adapted wearers. However, limitations in the study design are acknowledged, including the relatively small sample size, lack of standardisation of the habitual correction and the use of adapted wearers. Future studies are recommended to investigate these issues further.     

Task and visual performance with concentric bifocal contact lenses

We evaluated the effects of concentric simultaneous vision bifocal contact lenses on task performance, visual acuity, and stereopsis. Forty extensively screened presbyopes were fitted with CIBA Spectrum center-near bifocal contact lenses (BCL) and with distant contact lenses combined with reading spectacles (DCL) which served as the control. Thirty-two subjects completed the 8-week study. At dispensing and after 8 weeks of regular BCL wear, performance times with BCL were significantly greater than with DCL for all three near tasks. BCL generally resulted in more errors per trial. Visual acuities with BCL were reduced significantly by 0.8 to 1.4 acuity lines compared to DCL. Stereopsis was reduced significantly by 32 to 36 sec arc with BCL compared to DCL at both measurement sessions. It is likely that the decreased task performance with the simultaneous vision BCL is caused by the decreased visual acuity with these lenses. Nonetheless, 27 patients (58.7% of those selected to be fitted; 67.5% of those who were fitted) chose to wear the BCL on a regular basis at the study conclusion. Thus, even though BCL reduced task and visual performance, thoroughly screened and properly fitted presbyopic patients can become satisfied BCL wearers. However, the reduced task and visual performance with BCL should be considered when evaluating prospective BCL candidates.     

Adaptation to monovision

Many patients who begin wearing monovision contact lenses report that it requires days or weeks for them to become adjusted to the anisometropia; however, it is not clear if there are measurable improvements in their vision during this period. We therefore studied both the objective and subjective characteristics of adaptation to monovision over a period of 8 weeks. Sixty presbyopic subjects wore high water content hydrogel lenses in the study. During the 8 weeks of monovision wear, there were no significant changes in the subjects' visual acuities (distance, intermediate, or near) in high- and low-luminance conditions, near stereopsis, or interocular blur suppression characteristics. Nevertheless, the subjects reported significant improvement in various aspects of visual performance during the same period. Forty-eight percent of the subjects reported complete tolerance to the vision with their correction within the first week of monovision wear and a total of 78% of subjects were completely satisfied with the monovision correction at the completion of 8 weeks wear. The improved tolerance to monovision may be related to changes in aspects of vision other than those measured in this study or may reflect a psychological adjustment to the anisometropia.     

A clinical evaluation of two multifocal soft contact lenses.

We fit two multifocal soft contact lenses, Bausch & Lomb's Bi-Tech and the Unilens contact lens from Unilens Corporation, in two separate populations of presbyopes. Most patients (24/42, 57%) had no prior contact lens experience. Patients were evaluated at 6 and 12 months for comfort, visual acuity, lens fit, and corneal findings. Both distance and near vision were found to be slightly decreased with each contact lens when compared to best corrected visual acuity with spectacles. Seventy-seven percent (14/18) of the Unilens wearers and 67% (16/24) of the Bi-Tech wearers continued to wear their lenses for at least 1 year. Those who discontinued lens wear did so because they were dissatisfied with their vision. Presbyopes who seek correction with soft contact lenses appear to be more tolerant of a decrease in distance vision than a decrease in near vision. Both lenses were comfortable and no corneal pathology was induced. Our results suggest that the Unilens (simultaneous vision design) provides more predictable correction of presbyopic symptoms than the Bi-Tech (alternating vision design) because it is independent of lower lid position and translation. Both of these lenses are viable options for the correction of presbyopic symptoms.     

Vision and task performance with monovision and diffractive bifocal contact lenses.

We measured vision and task performance on 26 presbyopes, ages 46 to 65 years, fitted with diffractive bifocal contact lenses (BFCL) and monovision contact lenses (MVCL). Distance contact lenses combined with reading spectacles (DCL) served as the control condition. Twenty subjects completed the 6-week study. All subjects wore BFCL and MVCL daily for a period of 3 weeks each. Performance times for three near tasks were 6 to 8% longer with BFCL compared with DCL and 2 to 6% longer for MVCL compared with DCL. There were significant reductions in distance visual acuity with BFCL (0.4 to 1.5 Snellen lines) and MVCL (0.5 to 0.8 Snellen lines) compared to DCL. At the conclusion of the study, given a choice between BFCL and MVCL, 2 of the 20 subjects chose to continue wearing BFCL, whereas 18 of the 20 subjects chose MVCL. Our results show greater visual compromise and decreased task performance with BFCL and MVCL compared to DCL and greater patient preference for MVCL.     

Investigation of the performance of the Menifocal Z gas-permeable bifocal contact lens during continuous wear.

PURPOSE: The Menifocal Z is an alternating vision, concentric, bifocal gas-permeable (GP) contact lens; center distance is connected to near periphery by a smooth transition zone. The lens is produced using tisilfocon A (Menicon Z material), which is approved for up to 30 days of continuous wear (CW). The aim of this study was to evaluate the clinical performance of the Menifocal Z when worn for up to 30 days of CW for 6 months. METHODS: Thirty-five existing GP lens wearers were enrolled in the study. Subjects were fitted with Menifocal Z lenses and follow-up visits were conducted after 2 weeks of daily wear and 1 day, 1 week, 6 weeks, 3 and 6 months of CW. A range of objective and subjective clinical performance measures were assessed, including distance and near visual acuity, the physiological response to CW, and subjective evaluation of vision and comfort. RESULTS: Twenty-seven subjects (77%) completed the study and eight (23%) discontinued: five (14%) as a result of lens-related problems (four vision, one comfort) and three (9%) as a result of non-lens related reasons. Average CW time achieved by the subjects was 22 +/- 2 days. Mean binocular logarithm of the minimum angle of resolution (logMAR) acuities at 6 months were: high contrast distance 0.03 (20/20-), low contrast distance 0.63 (20/80-), and high contrast near 0.26 (20/25, N4). Adverse responses and lens binding were minimal, and there were no significant increases in corneal staining, corneal vascularization, or superior palpebral conjunctival papillae over time (p > 0.05). Problems with night vision (distance and near) with the lenses were the most common difficulties reported by the subjects. CONCLUSIONS: The Menifocal Z appears to be a promising option for presbyopic vision correction, providing successful correction of distance and near vision in a group of experienced GP lens wearers. The hyper Dk tisilfocon A (Menicon Z) material allowed for safe wear of the lenses on a CW basis.     

The ChromaGen contact lens system: colour vision test results and subjective responses

The ChromaGen lens system is designed to enhance colour perception in colour vision deficiency (CVD). To investigate its efficacy, 14 CVD subjects were prescribed ChromaGen contact lenses. Colour vision tests (Ishihara, Farnsworth Munsell D-15, Farnsworth Lantern) were administered at baseline, lens dispensing, and after a 2-week lens-wearing trial during which subjective responses were recorded daily using visual analogue scales. ChromaGen lenses significantly reduced ishihara error rates (p < 0.001; ANOVA), particularly for deutan subjects. There was also a significant reduction in errors (p < 0.005) on the D-15 test. Conversely, lens wear had no significant effect on Farnsworth Lantern test performance. Subjectively, subjects reported enhanced colour perception, but poor vision in dim light. Judgement of distance and motion were only slightly affected. We conclude that ChromaGen lenses may enhance subjective colour experience and assist in certain colour-related tasks, but are not indicated as an aid for CVD in occupations with colour vision-related restrictions.     

Is binocular contrast sensitivity at distance compromised with multifocal soft contact lenses used to correct presbyopia?

PURPOSE: The purpose of this investigation was to determine whether new experimental multifocal optical designs incorporating diffractive/refractive optics for correction of presbyopia in a soft contact lens would compromise binocular contrast sensitivity at distance while achieving 20/20 binocular visual acuity at near. METHODS: Thirty presbyopic volunteers were fitted with Acuvue Bifocal soft lenses, two (FO1 and 3B1) experimental diffractive/refractive multifocal soft lenses separately and in combination as a pair and soft spherical lenses. Visual performance was evaluated via binocular contrast sensitivity and binocular distance high- and low-contrast visual acuity after 1 week of lens wear. RESULTS: The experimental lenses FO1 and the combination FO1/3B1 performed as well for binocular contrast sensitivity, binocular distance high-contrast visual acuity, and binocular distance low-contrast visual acuity as the habitual presbyopic correction and the spherical soft distance correction. A strong correlation (r = 0.73 and 0.53, respectively) was found between binocular contrast sensitivity and binocular distance low-contrast visual acuity with experimental FO1 and FO1/3B1 lenses. However, the correlation (r = 0.37 and 0.60, respectively) between binocular contrast sensitivity and binocular distance high- and low-contrast visual acuity with FO1 was weaker than that with the combination FO1/3B1 lenses. Subjective responses support the objective data. DISCUSSION: The data show that experimental FO1 lens and the experimental combination of the FO1/3B1 lenses can be prescribed to not compromise distance binocular contrast sensitivity.     

Stereopsis in presbyopes wearing monovision and simultaneous vision bifocal contact lenses

One of the advantages suggested for contact lens bifocals over monovision treatment of presbyopia is that there may be less impairment of binocular function. We evaluated nearpoint stereoposis on the Titmus stereotest for 10 presbyopic patients. Testing was done under five conditions; monovision and binocular correction with each of four marketed simultaneous bifocal contact lenses. Simultaneous vision bifocals tested produced at least as much reduction in stereopsis as monovision compared to baseline spectacle correction. Repeat testing of bifocal stereopsis with best near over-refraction suggested that a substantial portion of the stereo reduction could be attributed to insufficient effective adds with the bifocal contacts.     

Prevalence of spectacle and contact lens wear in the UK fire service

Despite the fact that firefighting has been shown to be a visually demanding occupation, the present visual standards for firefighters prohibit the use of spectacles or contact lenses operationally. To determine the proportion of the UK fire service currently using spectacles and contact lenses, and how many may benefit from optical correction, a questionnaire was distributed. This contained 30 questions and was sent to 1550 firefighters. The data from 1064 returned questionnaires have been analysed. The results show that approximately 20% of those serving in the fire service have used an optical correction at some time in their lives. When not working, approximately 6% of firefighters wear spectacles for distance vision and 15% wear them for reading. Only 0.4% of firefighters use contact lenses. Half of this contact lens wearing group use their lenses while on operational duty. In total, approximately 2% of firefighters use an optical correction for operational duties. The results indicate that a high visual standard at the time of entry into an occupation cannot guarantee good vision throughout an individual's career. In addition, an estimated 11 000 firefighters in the UK, who have spectacles or contact lenses, do not use them for operational duties. The present visual standards prevent this group of firefighters from obtaining their optimal visual performance at work.     

Visual function with presbyopic contact lens correction

All forms of ophthalmic correction for presbyopia require compromises in viewing flexibility and visual function. The unique effects on vision of contact lenses used in managing presbyopia are especially intriguing and potentially problematic. Bifocal contact lenses produce unique changes in the nature and quality of the retinal image. In monovision (MV) correction, anisometropia is intentionally created by fitting one eye to see clearly at optical infinity and the other eye to see clearly at the near working distance. Our review of the literature indicates that most visual functions are affected by these departures from the conventional optical correction strategies used on nonpresbyopes. Sensory functions such as contrast sensitivity and stereoacuity are affected most, whereas motor functions such as convergence and accommodation are not noticeably impaired. MV appears to produce a more widely acceptable visual compromise than currently available bifocal contact lenses for most patients.     

Overnight corneal reshaping versus soft disposable contact lenses: vision-related quality-of-life differences from a randomized clinical trial.

PURPOSE: The purpose of this article is to evaluate patients' visual acuity, symptoms, and perceptions of vision-related quality of life in a randomized crossover clinical trial of overnight corneal reshaping (OCR) and daily wear soft lenses (SCL). METHODS: Qualified subjects were randomly assigned to wear one mode of contact lens for 8 weeks and then, after a washout period, they wore the alternate mode for 8 weeks. On concluding each contact lens wear mode, subjects completed the NEI-RQL42 questionnaire. During the SCL mode, subjects wore lenses during their waking hours. During the OCR mode, subjects wore lenses only while sleeping. Soft lenses were Biomedics 55 2-week disposable lenses. OCR lenses were CRT lenses by Paragon. (Three subjects were fit with custom-designed OCR lenses in Boston XO material, manufactured by Art Optical.) LogMAR acuity was measured and slit lamp evaluation was performed at specified intervals during follow up. After completing both phases of the study, patients chose which mode they preferred. RESULTS: Of 81 enrolled patients, 65 completed both phases and 16 dropped out during the study. Significant differences (p<0.01) favoring SCL wear included better visual acuity and less trouble with glare. Significant differences (p<0.01) favoring OCR wear included less activity limitations, less trouble with symptoms, and less dependence on refractive correction. Of 65 completing both phases, 44 preferred the OCR lenses and 21 preferred the soft lenses. Subjects who preferred the OCR lenses were less myopic and had steeper K readings at baseline, and showed less difference between visual acuity during OCR wear and visual acuity with SCL. CONCLUSION: In subjects with mild myopia who experienced both SCL and OCR, better visual acuity and less glare resulted from SCL wear, whereas activity limitations, symptoms, and dependence on refractive correction were less troublesome with OCR wear. When the study was completed, 67.7% chose OCR lenses worn only while sleeping, whereas 32.3% preferred 2-week disposable soft lenses worn during the day as their preferred correction.     

Factors influencing success and failure in monovision

This study compared the visual performance of 70 successful and 18 failed monovision (MV) wearers, measured before contact lens dispensing. Compared with successful MV wearers, the failed group showed greater levels of ghosting at distance and near, lost more stereoacuity at 6 m, and lost slightly more near visual acuity. The failed MV group was also older on average than the successful group. Both groups showed worse visual acuity at distance and near with MV than at spectacle baseline, as well as worse stereoacuity at 6 m and 40 cm. Discriminant analysis indicated that distance ghosting, distance stereoacuity, and age were predictive of both success and failure (78% sensitivity; 82% specificity). An investigation, before lens fitting, of other effects of monocular blur on binocular function, as well as an assessment of personal characteristics such as motivation and the nature of visual demands, may further improve the accuracy of prediction of patient success with MV found in this study.