Purpose
To assess quantitatively the efficacy of monovision correction in the treatment of acquired small-angle binocular diplopia in adult patients.
Design
Prospective, interventional case series.
Methods
Twenty patients with symptomatic diplopia were enrolled in a prospective treatment trial at a tertiary university neuro-ophthalmology practice. All had stable deviations of 10 prism diopters or less for more than 3 months. Each received monovision spectacles, contact lenses, or both with distance correction in the dominant eye. Half received a +3.00-diopter add and the others received +2.50 diopters. The validated and standardized Diplopia Questionnaire and Amblyopia and Strabismus Questionnaire were used to quantify the efficacy of monovision correction for diplopia by measuring the functional impact on vision-specific quality of life.
Results
primary outcome: Based on the results of the Diplopia Questionnaire, 85% of patients experienced significant improvement in diplopia symptoms after monovision correction. There was a statistically significant 58.6% improvement in the Diplopia Questionnaire score in our patients ( P < .0001). secondary outcome: The Amblyopia and Strabismus Questionnaire scores demonstrated improved quality of life and daily function after monovision correction ( P = .03), especially in the areas of double vision( P = .0003) and social contact and appearance ( P = .0002).
Conclusions
Monovision decreased the frequency of diplopia and improved subjects’ quality of life. Monovision may be a feasible alternative for presbyopic diplopic patients who are dissatisfied with other conservative treatment options.
The management of binocular diplopia can be challenging. Treatment is based on eliminating the doubled image through monocular occlusion or through restoring binocularity. Binocularity can be achieved through prism spectacles, strabismus surgery, or botulinum toxin injection into an extraocular muscle. Prism correction with spectacles is the principal conservative treatment, but limitations include correction of ocular misalignment in primary position of gaze only and significant optical distortions in prisms beyond 8 or 10 prism diopters (PD). Although effective, surgical correction is not an option for patients with small-angle deviations because of the risk of overcorrection. Both surgery and botulinum injections are invasive procedures, and as such, expose the patient to risks including undercorrection, overcorrection, infection, vision loss, and risks of anesthesia. Patients with a primary inability to fuse (horror fusionis) and those with variable deviations are not amenable to fusion treatment. For these patients, only occlusion is available to eliminate the diplopic image. These cosmetically obvious treatments are often unacceptable to patients who object to losing use of a functioning eye and report diminution of the visual field.
Monovision correction holds promise as a treatment option for presbyopic patients with diplopia. By focusing one eye at distance and the other at near, the diplopic image may be blurred sufficiently to facilitate suppression. Typically used in contact lenses and refractive surgery, monovision correction was designed by Westmith in 1958 to allow presbyopic patients to wear contact lenses without the need for bifocals. There are only 2 small case series in the current literature reporting success with monovision correction for diplopia. These are retrospective reports with no quantifiable outcome measures. The purpose of this study was to assess quantitatively the efficacy of monovision correction in the treatment of acquired small-angle binocular diplopia in adult patients.
Methods
Twenty adult subjects (older than 45 years) with acquired strabismus and symptomatic uncorrected diplopia were recruited consecutively from a tertiary neuro-ophthalmology practice and were enrolled in a prospective interventional case series. Subjects with small-angle deviations of less than 10 PD were included because they were not surgical candidates and had limited treatment options, despite significant symptomatic diplopia. All study subjects were required to have stable deviations of at least 6 months in duration with diplopia lasting more than 50% of the day. All patients were required to have best-corrected visual acuity of 20/40 or better in each eye. Subjects were excluded if they were not presbyopic or if they were satisfied with prism correction for their diplopia.
Subjects underwent a complete ophthalmic examination at each visit, which included distance and near best-corrected visual acuity, versions, alternate cover testing, Worth 4-dot suppression testing, and Titmus stereopsis testing at near. According to individual preference, each subject received monovision correction via spectacles or contact lenses with their distance correction in the dominant eye. Dominance was determined by the hole-in-the-card test and the plus lens test. Subjects were instructed to increase the use of their monovision correction by 2 to 4 hours daily over the course of 1 week until they were wearing the correction daily during all waking hours. At any point during the study, subjects who became intolerant of contact lens wear were given the option of switching to monovision spectacles, and subjects who encountered difficulty adapting to monovision correction via spectacles were given the option of switching to contact lenses. The first 10 patients received a +3.00-diopter (D) add in the nondominant eye, whereas the following 10 received a +2.50-D add. The strength of the add was decreased after the first 10 patients because 7 of the patients disliked the close working distance when using a +3.00-D add.
The primary outcome of the study was the improvement in diplopia symptoms after monovision correction. For this purpose, the Diplopia Questionnaire was used to quantify the frequency of diplopia in 7 positions of gaze. The Diplopia Questionnaire has been validated against the Goldmann diplopia field with an intraclass correlation coefficient of 0.53 to 0.9. Compared with the Goldmann diplopia field, however, the Diplopia Questionnaire better represents diplopia in everyday life because it accounts for suppression and adaptation.
The secondary outcome of this study was to assess the improvement in subjects’ vision-specific quality of life after monovision correction, measured by the validated and standardized Amblyopia and Strabismus Questionnaire (ASQE). This 26-item self-administered Likert scale questionnaire contained 5 subscales addressing fear of losing the better eye, distance estimation, visual disorientation, double vision, and social contact and appearance. The subscale fear of losing the better eye was not included in the analysis because we excluded subjects who had amblyopia or a discrepancy in best-corrected visual acuity of more than 3 Snellen lines between eyes. The ASQE has shown good correlation with disability questionnaires and has been validated in large patient cohorts. The validation was performed in subjects with vision better than 20/50, which was accounted for in our inclusion criteria.
Both the Diplopia Questionnaire and the ASQE were administered when patients were examined at baseline and 6 to 8 weeks after their enrollment in the study. Differences between premonovision and postmonovision scores as well as the scores of the +2.50-D and +3.00-D monovision groups were analyzed via paired t tests, with statistical significance defined as P ≤ .05.
Results
Of the 20 subjects, 8 (40%) were men and 12 (60%) were women. The average age of the subjects was 58.6 years, and the mean duration of diplopia was 44.3 months, ranging from 6 to 96 months. According to the inclusion criteria, all deviations in primary gaze were less than 10 PD, with the average deviation being 5.35 PD. Eleven subjects (55%) previously had tried prism correction and were dissatisfied with the residual diplopia. Nine (45%) subjects had never received any treatment for their diplopia, except 1 subject who constantly wore an occlusion patch over the deviating eye. Subject demographics, cause of diplopia, and previous diplopia treatment are outlined in Tables 1 and 2 . None of the 20 subjects were withdrawn from the study. Table 2 also provides exact alignment measurements for each subject at the beginning and at the conclusion of the study. At the end of the study, the mean change in the deviation was a 2.07-PD increase for the horizontal portion of the deviation and a 2.5-PD increase for the vertical portion.
| Group | Mean Age ± SD (y) | No. of Male Subjects | No. of Female Subjects | Mean ± SD Duration of Diplopia (mos) | Average ± SD Deviation in Primary (PD) |
|---|---|---|---|---|---|
| Both | 58.6 ± 10.7 | 8 | 12 | 44.3 ± 32.4 | 5.35 ± 2.4 |
| Monovision with +2.50-D add | 65.2 ± 9.3 | 3 | 7 | 39.0 ± 33.4 | 6.1 ± 2.7 |
| Monovision with +3.00-D add | 51.9 ± 7.7 | 5 | 5 | 49.6 ± 32.3 | 4.6 ± 2.0 |
| Patient No. | Cause of Diplopia | Deviation in 1 Degree before Treatment | Deviation in 1-Degree after Treatment | Previous Treatments | Monovision Add (D) | Glasses or Contact Lenses | Subjective Improvement with Monovision |
|---|---|---|---|---|---|---|---|
| 1 | Third-nerve palsy | 5 XT | 2 XT, 3 LHT | Occlusion | 3.00 | Glasses | No |
| 2 | Decompensated esophoria | 6 ET | 10 ET | Prisms | 3.00 | CLs | Equivocal |
| 3 a | Decompensated esophoria | 6 ET | 10 ET | Prisms | 3.00 | CLs | Yes |
| 4 a | Fourth-nerve palsy | 4 RHT | 2 RHT | Prisms | 3.00 | Glasses | Yes |
| 5 | Decompensated exophoria | 4 XT | 2 XT | Prisms | 3.00 | CLs and glasses | No |
| 6 | Fourth-nerve palsy | 6 LHT, 10 ET | 12 LHT, 6 ET | None | 3.00 | Glasses | Equivocal |
| 7 | Skew deviation | 3 LHT | 5 LHT | Prisms | 3.00 | CLs and glasses | No |
| 8 a | Fourth-nerve palsy | 8 LHT, 8 XT | 8 LHT, 8 XT | None | 3.00 | CLs | Yes |
| 9 a | Fourth-nerve palsy | 2 RHT | 2 RHT | Prisms | 3.00 | CLs | Yes |
| 10 a | Decompensated esophoria | 6 ET | 6 ET | Prisms | 3.00 | Glasses | Yes |
| 11 | Fourth-nerve palsy | 4 HT | 6 ET | Prisms | 2.50 | Glasses | No |
| 12 | Sixth-nerve palsy | 2 ET | 4 ET | Prisms | 2.50 | Glasses | No |
| 13 | Ocular myasthenia gravis | 8 ET | 10 ET | Prisms | 2.50 | Glasses | No |
| 14 a | Ocular myasthenia gravis | 4 XT, 5 RHT | 10 XT, 12 RHT | None | 2.50 | Glasses | Yes |
| 15 a | Fourth-nerve palsy | 8 RHT | 8 RHT | None | 2.50 | Glasses | Yes |
| 16 | Fourth-nerve palsy | 8 RHT, 4 XT | 8 RHT, 6 XT | Fresnel prisms | 2.50 | Glasses | No |
| 17 a | Fourth-nerve palsy | 6 RHT, 10 XT | 4 RHT, 10 XT | None | 2.50 | Glasses | Yes |
| 18 a | Fourth-nerve palsy | 3 LHT, 2 XT | 3 LHT | None | 2.50 | Glasses | Yes |
| 19 | Decompensated exophoria | 10 XT | 10 XT | None | 2.50 | Glasses | No |
| 20 a | Fourth-nerve palsy | 8 RHT | 14 RHT | None | 2.50 | Glasses | Yes |
a Patients reporting a subjective improvement in diplopia with monovision correction.
Improvement in Diplopia Symptoms After Monovision Correction
According to the Diplopia Questionnaire, where a score of 100 signifies constant diplopia in all positions of gaze, both the +2.50-D and +3.00-D monovision groups had a significant decrease in their mean Diplopia Questionnaire score after monovision treatment. Overall, when the results of the 2 groups were pooled, there was a mean ± standard deviation 27.2 ± 22.5-point improvement in diplopia scores ( P < .0001). No significant differences were found between the +2.50-D and +3.00-D groups when both the premonovision and postmonovision scores were considered ( P = .65 and P = .50, respectively). Of the 20 subjects, 17 (85%) experienced an improvement in their diplopia score after monovision, 2 (10%) subjects’ scores remained unchanged, and 1 (5%) subject (Patient 7) demonstrated a worsening of the diplopia score by 8 points ( Table 3 ).
| Group | Premonovision Score | Postmonovision Score | Improvement | P Value |
|---|---|---|---|---|
| Both | 65.6 ± 18.4 | 38.4 ± 27.7 | ↓27.2 ± 22.5 | <.0001 |
| Monovision with +2.50 D add | 64.0 ± 19.5 | 42.8 ± 19.9 | ↓21.2 ± 13.9 | .0009 |
| Monovision with +3.00 D add | 67.2 ± 18.2 | 34.0 ± 34.4 | ↓33.2 ± 28.2 | .0047 |
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