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Scotogenic lens reviewed as alternative to patching for binocular diplopia
A novel device may preserve patients' visual fields and eliminate binocular diplopia symptoms.
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A novel scotogenic contact lens may be as effective in eliminating binocular diplopia and superior in preserving patients’ visual fields compared with standard occlusion, according to a study.
Binocular diplopia requires immediate symptomatic control, usually with eye patches or opaque contact lenses. In eliminating symptoms, current standard occlusion techniques reduce peripheral vision between 48% and 76%, the study said.
Parashkev Nachev, PhD, MRCP, and colleagues introduced a prototype for a soft contact lens device that creates a monocular central scotoma inversely mirroring the physiological variation in spatial acuity across the monocular visual field, which simply blurs the image in the corresponding pattern.
“The theoretically optimal occlusive treatment for diplopia is not complete occlusion of one eye, but a graded pattern of degradation of the image in one eye, corresponding to the inverse of the spatial acuity function across the monocular visual field. We have created a prototype contact lens that achieves this,” Nachev told Ocular Surgery News.
Novel device vs. conventional patching
The prototype scotogenic lens was created by precipitating barium sulfate within a soft contact lens with radially thinning edges of an overall approximate diameter of 7 mm.
“The device preserves the patient’s peripheral visual field in the occluded eye. This means that the binocular visual field remains essentially normal, preserving the aspects of visual function that are sensitive to having a full field,” Nachev said.
The study evaluated the lens in 12 subjects with artificially induced diplopia and 12 subjects with symptomatic diplopia of varying causes compared with conventional eye patching. Subjects were randomized to wear the scotogenic lens or a black eye patch on one eye for 30 minutes of free reading and room exploration. Comfort, aesthetics, effectiveness in eliminating the symptom and overall success were rated on a 10-point scale questionnaire.
Questionnaire results
The 12 normal subjects graded both methods equally effective in symptom control and comfort, with scores of 8.42 and 6.5, respectively, for the eye patch, and scores of 8.75 and 6.17, respectively, for the scotogenic lens. The lens was rated significantly superior in aesthetics and overall assessment, with scores of 2.33 and 6.42, respectively, for the eye patch, and scores of 8.75 and 8.67, respectively, for the scotogenic lens.
In the patient group, both methods were effective in abolishing symptoms, with the eye patch receiving a score of 9.73 and the scotogenic lens receiving a score of 9.27. The scotogenic lens was significantly superior in all other measures, with scores of 7.45 for comfort, 9.45 for aesthetics and 8.54 for overall assessment, compared with scores of 4.36 for comfort, 2.0 for aesthetics and 4.18 for overall assessment in the eye patch ratings.
“Though seemingly peripheral in significance as well as location, the peripheral visual field is actually crucial to navigation in everyday life, and so preserving it is far more important than seems at first glance,” Nachev said. “The device is also cosmetically more attractive than a patch, for it is no different from a colored contact lens, though of course this is something it shares with fully occlusive contact lenses.”
Marketing the scotogenic lens
Nachev recommended the device for anyone with double vision of any cause in whom contact lenses are not contraindicated and prismatic or other symptomatic correction that aligns the two images is ineffective.
“It could be used long term or as an interim solution while waiting for definitive treatment (eg, surgery),” he said. “It could be particularly helpful for those especially sensitive to changes in their visual field, such as those who live and work in environments that are complex to navigate.”
Nachev and colleagues are currently working on implementation of the device with an industrial partner, with hopes to market the scotogenic lens worldwide in the future.
“That will allow us to make available clinically a full-functional, low-cost device in the near future,” he said. “Though likely to be initially available in Europe, the intention is soon to market it worldwide.” – by Kristie L. Kahl
- Reference:
- Robert MP, et al. Br J Ophthalmol. 2015;doi:10.1136/bjophthalmol-2014-305985.
- For more information:
- Parashkev Nachev, PhD, MRCP, can be reached at the Institute of Neurology, UCL, London WC1N 3GB, UK; email: p.nachev@ucl.ac.uk.
Disclosure: Nachev reports he receives funding from the Wellcome Trust and the NIHR Biomedical Research Centre at University College London Hospitals NHS Foundation Trust and University College London.
Perspective
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Jennifer Loh, MD
In our exciting field of ophthalmology, with some of the most advanced and exciting technology in medicine, it can seem a bit disconcerting to offer a patient with diplopia what could be the oldest treatment for any eye problems: the classic pirate patch. This article by Robert and colleagues describes a novel treatment for diplopia symptoms that gives us an alternative to the cumbersome and cosmetically unappealing eye patch. The authors discuss the problem of reduced peripheral vision with complete patching of an eye and also how diplopic symptoms do not occur in the periphery of vision due to the reduced level of acuity of the peripheral field. Their research and creation of a scotogenic contact lens has shown that by blurring only the central portion of the vision, the peripheral vision of the affected eye is left intact and allows for improved spatial navigation in ones environment. In my opinion, this device would be especially helpful in cases of temporary diplopia, such as from a third nerve palsy. Success of the scotogenic lens could allow ophthalmologists to finally offer an advanced solution to an age-old problem.
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