EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
Issue link: https://digital.eyeworld.org/i/357599
55 EW RESIDENTS Introduction Surgical monovision is an intention- ally induced form of anisometropia that has become a popular treatment option among cataract surgeons who hope to offer patients excellent uncorrected visual acuity at both near and far distances. Although monovision has the potential to offer high levels of patient satisfac- tion and spectacle independence, judicious patient selection is key to its success because some patients can be intolerant of the result. With in- creasingly high patient expectations for the refractive outcomes of cat- aract surgery and with the increas- ing amount of treatment choices available given the development of premium intraocular lenses, it is important that we hone our ability to pick the right treatments for the right patients. Study summary The article "Binocular function in patients with pseudophakic mono- vision" 1 by Ito et al represents a significant effort to evaluate the im- portance of ocular deviation and ste- reopsis in patients who underwent pseudophakic monovision surgery. The retrospective study evaluated 60 patients who underwent pseudopha- kic monovision surgery. The study examined the relationship between preoperative near exophoria angle and postoperative stereopsis and binocularity. They found that pa- tients who had preoperative moder- ate-angle exophoria had decreased postoperative stereopsis and fusion when compared to patients who had preoperative small-angle exophoria. This article explored many interesting aspects of patient assessment and outcomes of pseu- dophakic monovision surgery, such as the importance of pre-existing exophoria and the potential for inducing worsened binocularity and stereopsis. These issues may be extremely important in identifying the best candidates for pseudophakic monovision. However, we believe this study, because of its design and limitations, fails to provide con- clusive evidence regarding these topics. The authors' conclusion, "Inclusion criteria should consider the preoperative exophoria angle for effective pseudophakic monovision outcomes," requires more careful evaluation before becoming regular practice. Comments In many ways, the authors' conclu- sions were limited by the study's design. This comparative case study's sample size was somewhat limit- ing, especially when considering that only 16 patients were included in the moderate-angle exophoria group. Another limitation of the study design was the inconsistency of the variables measured pre- and postoperatively. The authors com- pared preoperative motor testing (the degree of exophoria) with post- operative sensory function (stereop- sis and binocular fusion), giving an "apples to oranges" analysis of the effect of pseudophakic monovision surgery. There was no reporting of preoperative stereopsis and binoc- ular fusion. Granted, preoperative stereopsis would be more difficult to assess and likely reduced in patients with decreased visual acuity from cataract, but the omission of this information should be recognized as a significant limitation to the inter- pretation of the data. It is unknown whether stereopsis and binocular fusion worsened as a result of the monovision correction—this is a crucial piece of data for the authors' conclusion. A second major limitation of the study's design is that it lacked a control group of patients who were orthophoric. Although we appreci- ate the beneficial comparison of fusional outcomes in patients who had small-angle exophoria com- pared to those who had moder- ate-angle exophoria, it is important to know the effect of not having a phoria at all. This could only be accomplished by having a control group of orthophoric patients, however there was no such group of normal in the study. Having an or- thophoric group would have offered a baseline of expected fusional abili- ties. Given that the study lacked any orthophoric subjects, we believe the title of this paper is misleading and should indicate that this study only pertains to patients with preopera- tive exophoria. The lack of a control group in addition to the aforemen- tioned absence of a consistent com- parison between preoperative and postoperative outcome measures of fusional abilities limit the ability to reach meaningful conclusions—even if the study question is compelling. Ultimately, the most important measure of success of pseudophakic monovision is patient satisfaction. While pseudophakic monovision has been shown to have high levels of patient satisfaction in JCRS previously, 2,3 there are some cases where it simply does not succeed in providing patients with their desired visual outcomes. It would seem that an aspiration of this study would be to help in patient selection for pseudophakic monovision, however there was no patient satisfaction data shown. Although the study examined fusional ability, it remains an assumption that fusional ability is a surrogate for patient satisfaction. The fallibility of this assumption was Difficulty keeping pseudophakic monovision straight by Philip I. Niles, MD, Justin M. Risma, MD, and A. Tim Johnson, MD, PhD August 2014 Binocular function in patients with pseudophakic monovision Misae Ito, CO, PhD, Kimiya Shimizu, MD, PhD, Takahiro Niida, MD, PhD, Rie Amano, MD, PhD, Hitoshi Ishikawa, MD, PhD J Cataract Refract Surg (Aug.) 2014;40:1349–1354 Purpose: To evaluate the relationship between ocular deviation and stereopsis and fusion in patients who underwent pseudophakic monovision surgery. Setting: Department of Ophthalmology, Kitasato University Hospital, Kanagawa, Japan. Design: Comparative case series. Methods: This study comprised 60 patients who underwent surgical monovision correction with monofocal intraocular lens placement followed by routine postoperative examinations. The average age of patients was 70.2±7.7 years. The alternate prism cover test was used to measure motor alignment; sensory tests for binocularity included sensory fusion determinations using the Worth 4-dot test, near stereopsis test, and fusion amplitude measured with a prism bar. Patients with monovision were categorized as either having small-angle exophoria (≤10 prism diopters) or moderate-angle exophoria (>10 prism diopters). Results: The difference between the mean stereopsis values in patients with small- vs. moderate-angle exophoria was statistically significant (p<0.001). In the moderate-angle exophoria group, 10 patients (62.5%) developed intermittent exotropia after surgery, but no serious ocular deviation problems were observed. The fusion amplitudes in patients with pseudophakic monovision were approximately similar to normal value. Patients with moderate-angle exophoria were more likely to fail the Worth 4-dot test than those with small-angle exophoria. Conclusions: In patients with pseudophakic monovision having a near exophoria angle of >10 prism diopters, the possibility of changes in ocular deviation and stereopsis after surgery is a concern. Moreover, the application of monovision in patients with a previous moderate-angle exophoria should be carefully considered. continued on page 56 Thomas A. Oetting, MD Director, ophthalmology residency program University of Iowa EyeWorld journal club Pseudophakic monofocal monovision continues to be a common refractive strategy for cataract patients. I asked the Iowa residents to review a paper appearing in this month's JCRS, which considers whether exophoria is a risk factor for these patients. –David F. Chang, MD, chief medical editor