A mixed statistical model was used to evaluate visual acuity, accommodative response, and pupil size across the four study visits. Although retaining the ability to evaluate between and within subject differences similar to repeated measures analysis of variance, the mixed model has the advantage of not sacrificing power in the instance of missing data points, an important consideration with the small subject numbers. The mixed model allowed for specification of the covariance structure. Variance components were used. Paired t-tests were used to compare visual and ocular measurements between specific time points. Single p value testing was performed to determine whether the slope of the line across the study visits for each dependent variables was significantly different from zero. p values of ≤0.05 (2-sided) were considered statistically significant.
Eight of the ten subjects enrolled completed all four study visits. Two subjects withdrew from the study because of difficulty completing required study visits. Only the eight subjects completing all study visits were used for analysis. Of the eight subjects, six were female, five were African American, and the remaining three were white. The average age was 57.5 years (±4.75 years). At all four visits, changes in uncorrected near visual acuity, uncorrected objective accommodative response to a near target (Grand Seiko), and pupil size were analyzed. Survey results and homework compliance logs were also analyzed.
Uncorrected logMAR visual acuity was significantly better for distant targets than near (p < 0.001) (Fig. 2). This was expected because the subjects were uncorrected emmetropic presbyopes. There was no significant difference across study visits (before and after treatment) with respect to uncorrected logMAR visual acuity for distance (p = 0.86) or for near (p = 0.78) indicating no treatment effect.
The accommodative response for distance targets showed no significant change across study visits (p = 0.98) (Fig. 3). Similarly, there was no significant overall change in response to near targets (p = 0.96); however, there was a statistically significant increase in the left eye only (0.18 D greater accommodation) in response to a near target at visit 3 (first post-treatment visit) (p = 0.03), yet this did not persist at visit 4 (second post-treatment visit). No significant correlation was found between age and baseline near accommodative response (p = 0.1077 OD, p = 0.4168 OS).
A significant effect on pupil size was found between distance and near targets, with near target testing conditions showing smaller pupils than distance targets (p = 0.006) (Fig. 4). Across all visits, pupil sizes showed no significant difference during distance (p = 0.26) or near testing conditions (p = 0.46).
Subject Surveys and Compliance
At both post-treatment visits (visits 3 and 4), subjects were queried about the quality of their near vision, the use of a reading prescription, compliance with the treatment program, and whether they would recommend this program to a friend. At both visits, seven out of eight subjects (87.5%) reported that uncorrected near vision was slightly to significantly improved since beginning the program. At both post-treatment visits, five of eight subjects (62.5%) reported they used reading glasses “less than before” beginning the program, and one subject reported no longer using reading glasses at the final study visit. Seven out of eight (87.5%) and six out of eight (75%) would recommend this program to a friend at visits 3 and 4, respectively.
Compliance was assessed with home log sheets and through questions on the in-office survey. The data from the home log sheets were incomplete and inconsistent; therefore, little meaningful information was obtained from them. Responses to the in-office survey showed that more than half5 of the subjects reported performing the program 4 to 6 times per week after visit two (the dispensing visit). One subject performed the program every day. By the final visit, only three of the eight subjects continued to perform the activity 4 to 6 times per week. One subject was still performing the program every day, and another had discontinued the program all together.
The RWOG Method claims that daily therapy provided by this program can eliminate the need for reading glasses in presbyopes. By performing the chiastopic fusion activity and stimulating convergence, the authors claim patients can tap into accommodative reserves allowing them to read near text. The authors cite the work of Baker and Gilmartin who showed that as accommodative amplitudes decrease with age, the accommodative convergence (AC/A) response increases.17 With an increase in AC/A, increased accommodation would lead to over-convergence creating diplopia. To prevent diplopia, there is a decrease in the convergence accommodative (CA/C) response and a proposed decrease in proximal vergence cues. The authors of RWOG use this model to explain that presbyopic patients choose fusion over clarity and therefore do not use their full accommodative abilities while reading. This is why, the authors claim that near vision is much clearer while performing the chiastopic therapy; the eyes are allowed to over-converge without experiencing diplopia “releasing residual accommodation for sharp vision.”11 If the assumption that reserves of accommodation are available when the eyes are over-converged is true, it is not clear how practicing this activity would provide improved near visual acuity when the eyes are not over-converged or why this practice would provide any long-lasting effect. The results of the present study showed no change in uncorrected near visual acuity or near accommodative response after the use of the RWOG method, and therefore the claims of the program are not supported.
The authors of RWOG also cite the work of Ostrin and Glasser stating that these researchers found “significant residual accommodation” even at more advanced stages of presbyopia.18 In their research on accommodative measures in presbyopes, Ostrin and Glasser subjectively and objectively measured accommodative amplitudes in adults up to the age of 55. As part of the protocol, subjects were given 1 drop of pilocarpine hydrochloride 6% to stimulate accommodation, and refractive measures were taken with the Hartinger Coincidence Refractometer. In the patients aged 51 to 55 years, the accommodative response to 6% pilocarpine was 0.79 D ± 0.68 D (n = 6).18 Even with pharmacological stimulation of accommodation, the maximum accommodation a patient in this age range should expect to achieve would be <1.5 diopters (although most would achieve <1 D). Arguably, this “residual accommodation” would be unlikely to eliminate the need for reading glasses in absolute presbyopes.
Animal models of presbyopia have demonstrated that with increasing age, the ciliary muscle maintains its ability to contract against the intraocular lens; however, the lens becomes less pliable (more rigid) and unable to change refractive power.1,5,6 This would explain why Ostrin and Glasser's presbyopes showed very little accommodation even with 6% pilocarpine. Even if the ciliary muscle is able to maximally contract, the presbyopic lens is too rigid to change shape.1,5,6 The RWOG method claims to “isolate specific eye muscles to strengthen accommodation” much “like Nautilus equipment.”11 If the RWOG method does indeed stimulate the ciliary muscle through convergence training, it will likely produce no effect against the rigid crystalline lens. As expected, the data from the present study showed no statistically or clinically significant effect of the training on accommodative response to near targets and do not support the claims of the RWOG program.
It is also worthy to consider depth-of-focus, as it relates to age and its effects on tolerance to defocus in the presbyopic population. Depth-of-focus increases with age secondary to pupillary miosis and increasing subjective tolerance to defocus.19 The pupillary miosis seen as a function of aging decreases the size of the blur circle on the retina, thereby increasing the depth-of-focus and acting in a compensatory manner to the blur at near experienced during presbyopia. As expected in the present study, pupil size was smaller at near as compared with distance; however, no significant change in pupil size was noted across treatment visits. This suggests that the perceived benefit from the training is not related to effects on pupil size or depth of focus.
Although near visual acuity and accommodative response showed no change after treatment, many patients reported that they felt as if their near vision had improved since beginning the program, and more than half stated they were using reading glasses less often. A similar result was found by Leydolt et al. in their study of near vision in pseudophakic patients.20 In this prospective, randomized, examiner masked study, patients undergoing cataract surgery were placed into a “motivated” or “control” group after surgery. The “motivated” group was instructed that they were receiving a special protocol to increase their accommodative ability and ultimately decrease their dependence on reading glasses post-surgically. The patients were given 1% atropine at baseline (day 1 post-operatively) and 1% cyclopentolate 4 times/d for the following 10 days. They were also told not to wear any reading glasses for 3 months after surgery in order to “train” their near vision. Subjects in this group were allowed a maximum of +1.00 D readers if they were completely unable to read. Members of the control group were given no special post-operative protocol and were allowed to wear reading glasses. Three months after surgery, there was no difference in near unaided visual acuity or reading speed between the groups; however, the “motivated” group reported less dependence on reading glasses.20
It is also possible to consider blur adaptation as an explanation for the perceived benefit from the RWOG Method, despite the lack of statistically significant improvement in near visual acuity. Webster et al. found that “judgments of focus were strongly biased by adaptation.”21 Subjects viewing blurred natural images for prolonged periods ultimately reported these images looked less blurry. Although targets used in this study were not text and optotypes, it may give some clues as the perceived benefit of the program. If subjects in the present study felt motivated to decrease the use of reading glasses as a result of this program, they may have become more tolerate of defocused images.
In both the Leydolt and the present study, objective measures of treatment effect showed no improvement, but the expectations of the patients provided some subjective benefit.18 In both studies, patients were educated that these methods might decrease dependence on reading glasses.20 Despite the lack of findings to support this, patients in both studies reported a reduced dependence on glasses for near work.20 The results of the present study suggest that benefits reported by users of the RWOG method are the result of their own expectations of the program; a placebo effect.
It is possible that errors in measurement or test–retest repeatability of our outcome measures may have contributed to the lack of change found in accommodative response and/or near visual acuity. Studies on both the Grand Seiko and the MNRead have shown good repeatability, suggesting that any clinically significant effects from treatment with the RWOG Method should have been detected.22,23 Although the present study had a sample size of only eight, this was large enough to provide 85% power to detect a 0.50 D spherical equivalent change in accommodation at near using the Grand Seiko autorefractor. Changes in accommodation <0.50 D were not considered clinically significant enough to alter near visual acuity and thus the study was adequately powered.
Monitoring treatment compliance is a challenge in any home-based therapy study. Subjects in this study were asked to complete home log sheets to report when they performed the therapy as well as the duration of each training session. The reported compliance was overall very good, with more than half of the subjects performing the therapy 4 to 6 d/week in the weeks after dispensing of the DVD. The reported adherence to therapy cannot be objectively confirmed and therefore should be considered an estimate of the true compliance. It is difficult to predict if compliance would have been better or worse outside of the study. It is possible that better compliance with the treatment program may have affected the outcome of this study, but it seems unlikely and cannot be determined from this study.
The training regimen prescribed by the authors of the RWOG Method does not show a clinically or statistically significant effect on unaided near visual acuity. It also shows no clinically significant effect on near accommodative response. It is possible that a more comprehensive training program or more frequent training with the RWOG Method may have proven more effective, but it cannot be determined from the results of this study. Despite the lack of clinical, objective evidence of a treatment effect, some patients report less dependence on glasses after using the program. Patient expectations and motivation may provide a placebo benefit for some patients using the RWOG method.
Caroline B. Pate
UAB School of Optometry
1716 University Blvd
Birmingham, AL 35294-0010
Statistical assistance for pilot work was provided by Dr. David Corliss. Thanks to Dr. Mark Swanson for his statistical support and to Dr. Ailsa Colbert for her assistance with data collection. This study was presented at the American Academy of Optometry annual meeting, San Francisco, 2010. The authors have no financial interest in the product mentioned in this manuscript.
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Keywords:© 2012 American Academy of Optometry
presbyopia; accommodation; orthoptics; vision therapy; reading glasses