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.     

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 Quest for Spectacle Independence: A Comparison of Multifocal Intraocular Lens Implants and Pseudophakic Monovision for Patients with Presbyopia

ABSTRACT

We performed a literature review comparing multifocal intraocular lens (IOL) implantation with pseudophakic monovision to treat presbyopia. Multifocal IOLs utilize refractive or diffractive principles to treat both distance and near vision, with a single lens implant. Monovision uses traditional monofocal lens implants to treat the dominant eye for emmotropia, and the non-dominant eye for myopia. This planned anisometropia is designed to enhance intermediate or near vision. Generally, distance vision was similar with both types of lens implantation, near vision was better with multifocal IOLs, and intermediate vision appeared to be better in the monovision group. For patients requiring cataract surgery, both multifocal IOLs and monovision appear to address presbyopia with a high level of patient satisfaction. More patients reported complete spectacle independence with multifocal IOLs, but more glare and halos were reported by multifocal IOL patients as well.     

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.     

Surgical monovision and monovision reversal in LASIK

PURPOSE: This study was designed to assess the success of surgical monovision in presbyopic patients. METHODS: A university refractive surgery center retrospective chart review of 82 patients who elected to undergo surgical monovision with laser in situ keratomileusis (LASIK) between January 2000 and January 2003 was conducted. Specific factors included for analysis included preoperative and postoperative defocus spherical equivalent, whether the patient underwent enhancements, whether the patient underwent a preoperative monovision trial with contact lens, and whether the patient underwent monovision reversal. RESULTS: Eighty-two patients who underwent LASIK for monovision were analyzed. Mean preoperative spherical equivalent in the distance-corrected eye was -4.07 (standard deviation (SD), 2.49); for the eye corrected for near vision, mean preoperative spherical equivalent was -4.10 (SD, 2.56). Postoperative spherical equivalent in the distance eyes was -0.01 (SD, 0.38) and in the near eyes -1.24 (SD, 0.91). There were 6 enhancements in the near eyes (7%) and 17 enhancements in the distance vision eyes (21%). This difference was statistically significant (P = 0.007). Thirty patients underwent a contact lens trial of monovision before LASIK, and none of those patients elected monovision reversal. There were 52 patients who did not undergo a contact lens monovision trial before LASIK monovision, and 2 of these patients underwent monovision reversal. Monovision success in this population was 97.6%. CONCLUSION: Surgical monovision can help presbyopic patients achieve their goal of reduced dependence on spectacles. A trial of monovision contact lenses or spectacles may be important in helping surgeons select patients for successful surgical 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.     

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.     

Monovision矫正屈光不正的应用

Monovision(MV)矫正方法以往常用于老视和老视前期患者,即1眼矫正视远,另1眼矫正视近,其机制是双眼间的模糊抑制。近几年也用于中年近视的矫正。我们就MV矫正的机制、应用方式、对双眼视功能的影响以及研究进展作一综述。     

Peripheral visual acuity with monovision and other contact lens corrections for presbyopia

We have conducted two experiments to investigate the effect of monovision and other contact lens corrections for presbyopia upon peripheral visual acuity. In the first study, we measured binocular peripheral visual acuity using Landolt rings with seven subjects wearing a monovision correction. The Landolt rings were presented at eccentricities of 10, 20, 40, and 70 degrees on each side of the subject, with near additions of +1.50 D, +2.50 D, and no addition. We found no significant effect of monovision correction on peripheral visual acuity. In the second experiment we measured the peripheral visual acuity of 11 presbyopic subjects wearing distance contact lenses with lookover spectacles, soft progressive bifocal contact lenses, soft concentric bifocal contact lenses, monovision contact lenses, modified monovision contact lenses, and hard bifocal contact lenses using Koenig bar targets. There were no significant differences in peripheral visual acuity between any of the contact lens corrections for presbyopia.     

Ocular dominance testing

Clinicians typically apply the distance correction to the dominant sighting eye when fitting monovision contact lenses on presbyopic patients. This study investigates if this form of dominance testing correlates with a second type of dominance testing, the eye that will accept the least plus power when viewing a distance target binocularly. The plus lens test more closely simulates the condition under which the patient will be using the monovision correction. The theory is that the nondominant eye will accept more plus to blur than the dominant eye. Our study population consisted of subjects from the ages of 10 to 72 years. Fifty (64%) of the 78 subjects preferred the same eye by the plus lens testing as they did for sighting dominance. Seven subjects (9%) showed the opposite eye dominance with the plus lens test, and 21 subjects (27%) demonstrated no preference in the plus lens testing. The results could indicate that same-eye dominance on both tests may enhance the changes of a successful monovision adaptation.     

Accommodating intraocular lenses

PURPOSE OF REVIEW: With the advent of interest in accommodative lenses as a solution for presbyopia and the growing baby-boomer demographic, ophthalmic surgeons will have the opportunity to provide this technology to facilitate near, intermediate, and distance vision for their patients. RECENT FINDINGS: At present, six corporate entities and lens designs are attempting to commercialize accommodative intraocular lens devices. One Food and Drug Administration (FDA) clinical trial has been completed and the first FDA-approved accommodating lens is available. SUMMARY: For the first time, ophthalmic surgeons will be able to provide a full range of visual focus in each eye of a patient to maintain binocular function while also avoiding the unwanted mesopic and scotopic visual disturbances that are experienced with monovision and multifocal lens technologies. Accommodative intraocular lenses could revolutionize not only cataract visual rehabilitation but also the surgical approach to presbyopia.     

Binocular function and patient satisfactionafter monovision induced by myopic photorefractive keratectomy

Purpose:To measure binocular function and patient satisfaction with monovisioninduced by photorefract ve keratectomy (PRK) in myopic presbyopic patients.Setting:Refractive Department; Cleveland Clinic; Cleveland, Ohio, USA.Methods:This study comprised 21 myopic presbyopic patients with monovisioninduced by PRK. Sixteen emmetropic patients who had PRK served as a control group. Monovision was induced by undercorrecting the nondominant eye by 1.25 diopters for near vision and correcting, the dominant eye with emmetropia for distance vision. Monocular and binocular uncorrected Snellen visual acuities at 20 feet and 13 inches, manifest refraction, ocular dominance, stereopsis at 20 feet and 13 inches, Monocular and binocular contrast sensitivities, Worth-4-Dot test at 20 feet and ⅓ of a meter, and fusional convergence amplitudes were examined in each patient.Results:In the monovision group at near and distance, 20 patients (95.3%) had binocular visual acuity of 20/25 or better. No patient in the monovision group used reading glasses postoperatively; 4 of 16 patients (25.0%) in the control group used such glasses. All patients maintained binocular fusion and stereo acuity ranging from 40 to 800 seconds of arc. Mean patient satisfaction was 86% (range 40% to 100%). In the control group, 12 patients (75.0%) had binocular distance visual acuity of 20/25 or better and 11 (68.8%) had binocular near visual, acuity of 20/25 or better.Conclusion:Monovision PRK patients had better near vision than control PRKpatients, with minimal compromise in stereo acuity and overall high patient satisfaction.     

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.     

Monovision and LASIK.

BACKGROUND: Many LASIK patients are early and mid-presbyopes. Monovision is commonly targeted for these patients because of demographics. Considerations are reduced stereopsis, reduced acuity, night driving, and liability. CASE REPORTS: Case studies are used to illustrate contact lens and alternative trials for presbyopic and prepresbopic monovision LASIK patients. CONCLUSION: A preoperative monovision contact lens trial can be used to demonstrate monovision effects to the candidate for refractive surgery. Selection of add power, selection of distance and near eye, residual astigmatism, management, and gradual transistioning with regards to adaptation 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.     

Comparison of myopes and hyperopes after laser in situ keratomileusis monovision

PURPOSE: To compare the results of laser in situ keratomileusis (LASIK) monovision in myopes and hyperopes. SETTING: Private practice, Little Silver, New Jersey, USA. METHODS: In this retrospective study, 391 consecutive patients older than 40 years who had LASIK between December 1999 and June 2001 were examined. All patients were asked to complete a questionnaire, and study results are based on the analysis of data from patient charts correlated with questionnaire responses. RESULTS: Visual results were excellent in both groups, with all monovision patients achieving 20/30 acuity or better in the distance eye and J2 or better acuity in the near eye. Satisfaction scores were high in all groups. Statistical analysis indicated that visual results for distance were better in myopes than in hyperopes (P =.043), enhancements were higher in monovision (P =.04) and in hyperopia (P =.08), and satisfaction was higher among myopes (P =.012) and full distance patients (P =.002). Monovision hyperopes had the most difficulty with 6 side effects (P =.00). CONCLUSION: Hyperopic monovision was a viable but more problematic solution to correcting presbyopia than myopic monovision.     

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.     

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.