Visual performance of subjects wearing presbyopic contact lenses.

PURPOSE: The purpose of this study is to assess the visual performance of subjects wearing gas-permeable (GP) multifocal contact lenses, soft bifocal contact lenses, GP monovision lenses and spectacles. METHODS: The study included 32 subjects between the ages of 42 and 65 years wearing GP monovision, the Acuvue Bifocal (Vistakon), the Essentials GP Multifocal (Blanchard), and progressive addition lenses (PAL; spectacles group). There were eight subjects in each of these groups who were already wearing these modalities. Binocular low (18%) and high (95%) contrast acuities were recorded using the Bailey-Lovie chart; binocular contrast sensitivity from 1.5 to 18 cycles per degree (cpd) measured with the Vistech VCTS 6500 system, and monocular glare sensitivity at three luminance settings (400, 100, and 12 foot lamberts) was measured using the brightness acuity tester (BAT). Binocular near visual task performance (a modified version of letter counting method used in previous presbyopic studies) was also assessed. RESULTS: For the contact lens-wearing groups, subjects wearing GP multifocals provided the best binocular high and low contrast acuity followed by soft bifocal wearers. There was relative parity between the binocular high and low contrast acuity with PAL and GP multifocal wearers. Monovision acuity, measured binocularly, was determined to be lower than the other three groups with this difference being most significant with high contrast acuity. Among contact lens-wearing groups, it was observed that GP multifocal lens wearers experienced the lowest amount of monocular disability glare followed by soft bifocal wearers and monovision wearers. Subjects wearing soft bifocal lenses and monovision demonstrated slightly reduced binocular contrast sensitivity at all spatial frequencies. In the contact lens groups, GP multifocal lens wearers had the highest binocular contrast sensitivity at all spatial frequencies, on parity with PAL wearers, except at the highest spatial frequency (18 cpd) at which PAL wearers had better vision. Error scores for the binocular near visual task performance between the four groups revealed subjects with GP multifocal lenses and PAL wearers to have the least errors, followed by monovision users and then soft bifocal wearers with the most errors. CONCLUSION: Subjects wearing GP multifocals, soft bifocals, monovision, and PAL spectacles have good binocular contrast sensitivity, satisfactory binocular low and high contrast acuity, and increased sensitivity to glare. Presbyopic subjects requiring the use of contact lenses under dim light levels could benefit from GP multifocal lenses. Contrast and glare sensitivity evaluations provide significant information regarding the visual performance of the presbyopic contact lenses and should be included in regular presbyopic contact lens fitting.     

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.     

Comparison of suppression, stereoacuity, and interocular differences in visual acuity in monovision and acuvue bifocal contact lenses.

PURPOSE: The relationship between visual acuity and stereoacuity has been well documented: as binocular visual acuity increases, stereoacuity improves. We compared interocular differences in visual acuity and stereoacuity in two presbyopic soft contact lens modalities, monovision and a new soft bifocal contact lens, the Acuvue Bifocal. The Acuvue Bifocal is hypothesized to show a smaller interocular acuity difference, increased stereoacuity, and decreased suppression over monovision at distance and near. METHODS: Monovision patients wearing Acuvue or Surevue soft contact lenses were tested for visual acuity, stereoacuity, and suppression at distance and near. Stereoacuity was tested with the Randot Stereotest (near) and the BVAT (distance). Suppression was evaluated with the Acuity Suppression Vectogram (near) and the BVAT (distance). Patients were then fit with the Acuvue Bifocal in each eye. After wearing the lenses for 1 week, the same tests of visual acuity, stereoacuity, and suppression were performed. RESULTS: The mean interocular acuity difference (IAD) at distance with monovision was 0.712 logarithm of the minimum angle of resolution (logMAR) (SD = 0.275) and 0.188 logMAR (SD = 0.252) (p < 0.001) with the Acuvue Bifocal. At near, the mean IAD with monovision was 0.420 logMAR (SD = 0.183) and 0.137 logMAR (SD = 0.147) (p < 0.001) with the Acuvue Bifocal. Of the monovision subjects, 89% (17 of 19) demonstrated suppression at near while only 26% (5 of 19) did with the bifocal lenses (statistically significant at p < 0.001). Stereoacuity at near improved from a median of 200 sec arc with monovision to 50 sec arc with the bifocal lenses. CONCLUSIONS: In this study, correcting presbyopia with the Acuvue Bifocal versus monovision resulted in a statistically significant decrease in the interocular difference in visual acuity at distance and near. The decreased interocular difference in visual acuity improved certain aspects of binocularity as demonstrated by a decrease in suppression and an increase in stereoacuity.     

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.     

Visual performance of a multi-zone bifocal and a progressive multifocal contact lens.

PURPOSE: This study measured the relative visual performance of two planned-replacement soft contact lenses for presbyopic correction: a multi-zone bifocal (ACUVUE, Johnson & Johnson Vision Care, Jacksonville, FL) contact lens and a progressive multifocal (Focus Progressives, CIBA Vision, Duluth, GA) contact lens. METHODS: This was a randomized, double-masked, non-dispensing cross-over study. Visual performance was evaluated by log of minimal angle of resolution (LogMAR) measurement of visual acuity (VA) under a representative range of luminances (distance 250 candela[cd]/m2 and 2.5 cd/m2, near 250 cd/m2 and 50 cd/m2) and contrasts (90% and 10%). The 45 presbyopic subjects were equally distributed in three subgroups according to spectacle addition: low presbyopia (+0.75D to +1.25D); medium presbyopia (+ 1.50D to + 1.75D); and high presbyopia (+2.00 to +2.50D). RESULTS: Statistically significant differences were found in overall distance VA (P<0.001; average of four luminance-contrast combinations) and low-luminance distance VA (P=0.004), which, in both cases, favored the multi-zone bifocal lens design. For low presbyopes, the multi-zone bifocal design produced a significantly better visual performance (P=0.004) than did the progressive multifocal. Overall near VA was also significantly better (P<0.001) with the multi-zone bifocal lens. Differences in near VA were particularly marked in high-luminance conditions (high and low contrasts combined) and were statistically significant for all three presbyopic subgroups. CONCLUSIONS: Visual acuity performance with the multi-zone bifocal was superior overall to that achieved with the progressive multifocal design. This study suggests that having only one addition is detrimental to performance with the progressive multifocal lens, particularly for low presbyopes.     

Reaction times in a complex task by presbyopic observers with spectacle and contact lens corrections

Reaction times were measured in a complex three distance task for presbyopic subjects wearing multifocal spectacle corrections or bifocal contact lens corrections; the same task was performed by young control subjects with no correction and further groups of young control subjects wearing hard or soft contact lenses. The targets could be discriminated only if subjects were looking directly at the displays. The reaction times were least for targets presented at the intermediate distance, and increased for near and distance targets. Subjects wearing spectacle corrections gave better performance on the whole than those wearing the contact lens corrections, but there were no significant differences in reaction times between the two spectacle corrections used or between the six contact lens corrections used. Neither of the presbyopic groups performed as well as the young control group.     

Contrast sensitivity with contact lens corrections for presbyopia

We measured contrast sensitivity at three distances (330 mm, 660 mm and 4 m) with six contact lens and two multifocal spectacle corrections for presbyopia. The two spectacle corrections were D-segment bifocals and trifocals and the contact lens corrections were distance contact lens with lookover spectacles, soft progressive bifocals, soft concentric bifocals, monovision, modified monovision, and hard crescent segment bifocals. The spectacle corrections in general gave better results for the contrast sensitivity function (CSF), than did the contact lens corrections. Distance contact lenses with lookover spectacles performed best of the contact lens corrections used. However, the differences in CSF between the various contact lens corrections were small and not statistically significant.     

Presbyopic fitting strategies: Fitting lenses to patients,not patients to lenses

Eighty-six presbyopic patients who were interested in contact lens wear but had no history of using contact lenses for the correction of presbyopia were entered into a study performed across five independent contact lens practices. Patients were fit utilizing a fitting strategy flowchart that included monovision, diffractive, and aspheric simultaneous and alternating vision presbyopic corrections. At the conclusion of the study, 83% of the patients were successful utilizing the criterion that the patient was still actively wearing the lenses. Fifty-two percent were fit with monovision, 14% were fit in alternating vision lenses, while 6% and 10% were fit with aspheric and diffractive lenses, respectively, including modified monovision.     

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.     

Monovision vs. soft diffractive bifocal contact lenses: A crossover study

The relative clinical performance of monovision and the Hydro® ECHELON® soft diffractive bifocal contact lens were evaluated in a 1 -month, two-period, open-label crossover study. Wearers' subjective impressions were also elicited. Monovision provided superior low contrast acuity and the bifocal better stereopsis. No difference was found for high-contrast visual acuity or physiological signs. Although monovision was subjectively preferred for reading, no difference was found for other subjective variables. These included visual quality ratings at far and intermediate viewing distances, under dimly lit conditions, when driving at night, and for overall preference. Similiar patient acceptance can be expected for both modalities. The results of this study reflect a significant improvement in performance of the diffractive bifocal lens over previous simultaneous vision bifocal contact lens damage.     

Presbyopic contact lenses

The year 1999 will be remembered as the one in which a very successful bifocal soft contact lens was finally available for the millions of presbyopic and emerging presbyopic Baby Boomers. As a result, soft bifocal fits almost tripled in 1 year. The introduction in 1999 of new daily disposable and new high oxygen permeable extended wear soft contact lenses will give practitioners more options to be successful with monovision. Tips from several practitioners on being successful with bifocal soft lenses are given. It cannot be stressed enough, however, that for patients with presbyopia to be successful with these lenses, they must be willing to compromise somewhat on the quality of vision they remember as a 30-year-old.     

The influence of ocular dominance on monovision--the influence of strength of ocular dominance on visual functions

PURPOSE: Monovision is a method of correction for presbyopia. We have reported the advantage of conventional monovision (the dominant eye is corrected for distance). In this study, we investigated the influence of interocular imbalance of dominancy on the visual function. SUBJECTS AND METHODS: Ten healthy subjects without any ophthalmologic disease participated. After cycloplegia, the eyes of the subjects were corrected by soft contact lenses with an artificial pupil (diameter: 3.0mm). The dominant eye was corrected for distance, and the difference in lens power between the lenses was 2.5 D. The subjects were classified into two groups by strength of the imbalance of sensory dominance, which was determined by using binocular rivalry. Binocular visual functions (visual acuity at various distances, contrast sensitivity, near stereoacuity) were compared between the two groups. RESULTS: Subjects with strong imbalance of sensory dominance showed decreased near visual acuity as well as decreased binocular summation of contrast sensitivity at low spatial frequencies. On the other hand, near stereoacuity was not affected by the imbalance of sensory dominance. CONCLUSION: These results suggest that strong imbalance of sensory dominance interferes with binocular visual functions in monovision. Thus, the evaluation of ocular dominance is crucial for clinical applications of monovision.     

Change in refractive anisometropia in presbyopic adults wearing monovision contact lens correction.

BACKGROUND: Researchers studying the refractive development of infant monkeys suggest that monocular refractive error changes in response to induced ametropia; specifically, slightly blurring one eye may cause a difference to develop between each eye's correction (anisometropia) when none existed before wearing the correction. The important question of whether similar changes occur in humans has not been addressed. METHODS: We compared premonovision correction and the correction after at least 12 months of monovision soft contact lens wear (artificially induced anisometropia prescribed to focus one eye for near and the other for distance so that bifocal glasses are not needed) for 62 healthy predominantly female soft contact lens wearers and (a) 62 age- and sex-matched spectacle wearers and (b) 62 age- and generally sex-matched contact lens wearers. Control patients wore corrections of like power and had similar follow-up periods. RESULTS: Development of anisometropia occurred significantly more frequently among monovision wearers than among spectacle (p = 0.043) or contact lens wearing controls (p = 0.025). Changes in anisometropia greater than or equal to 0.50 D, with amounts up to 1.25 D, occurred in 29% of monovision wearers. CONCLUSIONS: Changes in refractive correction occur for adults who have monocular blur intentionally induced with monovision contact lenses. Similar changes may also occur after refractive surgery if one eye is corrected for a different distance than the other. Care should be taken when counseling presbyopic patients so that they are aware of the possibility of inducing refractive changes after monovision correction.     

Bifocal hydrogel lenses: an overview

Until the advent of bifocal hydrogel lenses, monovision or reading glasses were the modes of correction for hydrogel contact lens wearing presbyopes. Recent design innovations and improvements in the manufacturing technology of soft contact lenses have made possible new developments in bifocal hydrogel lenses. Patient selection and patient education play key roles in optimizing patient success. There are several hydrogel bifocal designs that are possible for the presbyope. The variations of these designs and their pertinent considerations are discussed.     

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.     

Optical and visual performance of aspheric soft contact lenses.

PURPOSE: This study was conducted to investigate whether aspheric design soft contact lenses reduce ocular aberrations and result in better visual acuity and subjective appreciation of clinical performance compared with spherical soft contact lenses. METHODS: A unilateral, double-masked, randomized and controlled study was undertaken in which ocular aberrations and high and low contrast logMAR visual acuity were measured on myopic subjects who wore aspheric design (Biomedics 55 Evolution, CooperVision) and spherical design (Biomedics 55, CooperVision) soft contact lenses. Ten subjects who had about -2.00 D myopia wore -2.00 D lenses and 10 subjects who had about -5.00 D myopia wore -5.00 D lenses. Measurements were made under photopic and mesopic lighting conditions. Subjects were invited to grade comfort, vision in photopic and mesopic conditions, and overall impression with the two lens types on 100 unit visual analogue scales. RESULTS: There was no significant difference in high contrast or low contrast visual acuity between the two lens designs of either power under photopic or mesopic conditions. Both lens designs displayed lower levels of spherical aberration compared with the "no lens" condition under photopic and mesopic light levels (p < 0.0001); however, there were no differences in aberrations between aspheric and spherical lens designs. There were no statistically significant differences in subjective appreciation of clinical performance between lens designs or lens powers. CONCLUSIONS: At least with respect to the brand of lenses tested, the fitting of aspheric design soft contact lenses does not result in superior visual acuity, aberration control, or subjective appreciation compared with equivalent spherical design soft contact lenses.     

Predicting and assessing visual performance with multizone bifocal contact lenses.

PURPOSE: To investigate how bifocal contact lenses, when combined with the aberrations of the eye, will affect visual performance. Also, to investigate the relationship between the patient's predicted and actual visual benefit with bifocal contact lenses. METHODS: The monochromatic aberrations of 16 subjects were measured and used to simulate visual quality with three bifocal contact lens designs. Actual and computed visual benefit was compared for an Acuvue bifocal contact lens in 5 of the 16 subjects. RESULTS: Subjects were predicted to have either a bifocal response or an increase in depth of focus for all lens designs. Our subjects were predicted to have a decrease in visual benefit for distance viewing and a gain in visual benefit at near compared with not wearing a contact lens. We found a statistically significant association between our subjects' predicted and actual visual benefit with the Acuvue Bifocal contact lens (r = 0.685, p = 0.008). CONCLUSIONS: Bifocal contact lens designs, when combined with the aberrations of the eye, will not always provide bifocal vision. Visual quality with a bifocal contact lens can be predicted based on a patient's ocular aberrations.     

The effect of add power on simultaneous vision,monocentric, bifocal,soft lens visual performance

The visual acuities of 13 pre-presbyopic subjects were tested using high- and low-contrast logMAR charts under high- and low-illumination conditions while alternatively corrected with simultaneous, monocentric, soft, bifocal contact lenses with add powers of + 1.25, +2.00, and +2.75 D. The results revealed significantly poorer low-contrast and low-illumination visual acuities for the higher add power lenses. It is suggested that the use of simultaneous vision bifocal soft contact lenses may not be the optimum form of correction when fitting the older presbyopic contact lens patient.