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Show Patients With Homonymous Hemianopia Become Visually Qualified to Drive Using Novel Monocular Sector Prisms Adam M. Moss, MD, MBA, Andrew R. Harrison, MD, Michael S. Lee, MD Abstract: Patients with homonymous hemianopia (HH) often fail to meet visual field (VF) requirements for a driver's license. We describe 2 patients with complete HH, who met the minimum VF requirements for driving using a novel, high-power, monocular sector prism system. Baseline VFs were assessed using automated and kinetic perimetry. Patients were fitted with glasses and press-on 57-PD periph-eral monocular sector prisms placed on the lens ipsilateral to the VF defect above and below the visual axis with prisms oriented obliquely. Kinetic perimetry was reassessed both monocularly and binocularly, with and without prisms. The 2 patients had 95° and 82° angle of continuous, horizontal, binocular VF. With the use of the prism system, the binocular VF increased to 115° and 112° angles. Both patients reported improvement in quality of life and each holds a valid driver's license and has successfully operated a motor vehi-cle without any restrictions or accidents. These findings sug-gest that the addition of oblique 57-PD prisms to the ipsilateral spectacle lens above and below the visual axis for patients with complete HH can significantly increase hor-izontal VF, which may help an individual become visually qualified to obtain a driver's license. Journal of Neuro-Ophthalmology 2014;34:53-56 doi: 10.1097/WNO.0000000000000060 © 2013 by North American Neuro-Ophthalmology Society Homonymous hemianopia (HH) occurs after damage to the contralateral retrochiasmal visual pathways. Despite adapting to the visual field (VF) defect, patients experience compromised independence from an inability to meet driving requirements. Although the specific VF requirements to obtain a driver's license vary by state, Minnesota requires that one should have at least 105° angle of binocular VF (1). In an attempt to expand the VF in patients with HH, a number of optical therapies have proposed a variety of mirrors, telescopes, and prisms. A novel approach utilizing monocular sector prisms limited to the peripheral field has been described by Peli (2). The prism is placed across the entire width of the lens above and below the visual axis, thus creating peripheral exotropia. Peli proposed that this would effectively expand the VF in all lateral positions of gaze while maintaining bifoveal alignment and eliminating diplopia. Recently, Bowers et al (3) described a modified technique using obliquely oriented prisms. Two Fresnel press-on 40-PD prism segments (3M Press-On Optics) were placed, base-out, at the upper and lower part of the spectacle lens ipsilateral to the VF defect with its central edge at the level of the limbus, spanning the entire width of the lens (Fig. 1). The individual prism segments were oriented obliquely at 45° angle from the horizontal axis, 7-8 mm apart. At the conclusion of the trial period, prisms were permanently ground and fixed into the lenses (Chadwick Optical, White River Junction, VT). Patients were instructed to gaze through the central, prism-free zone of the lens, rather than looking directly through the prism. No additional formal training was administered. In this report, we describe successful use of the prism system for the treatment of 2 patients with HH, which expanded VFs to allow each to meet minimum require-ments for driver licensure in the state of Minnesota. This study was approved by the Institutional Review Board at the University of Minnesota. CASE REPORT Case 1 A 24-year-old man suffered a right occipital lobe stroke in April 2011. He was emmetropic with a visual acuity of Department of Ophthalmology and Visual Neurosciences, University of Minnesota School of Medicine, Minneapolis, Minnesota. The authors report no conflicts of interest. Supported in part by an unrestricted grant to the University of Minnesota, Department of Ophthalmology and Visual Neurosciences from Research to Prevent Blindness. Address correspondence to Michael S. Lee, MD, Neuro-Ophthalmology Service, University of Minnesota School of Medicine, 420 Delaware Street, SE, MMC 493, Minneapolis, MN 55455-0501; E-mail: mikelee@ umn.edu Moss et al: J Neuro-Ophthalmol 2014; 34: 53-56 53 Clinical Observation Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. 20/20 at distance in both eyes. Visual field testing revealed a complete left HH, which remained stable for more than 9 months. The rest of his neuro-ophthalmic examination was unremarkable. Case 2 A 31-year-old man underwent resection of a right parieto-occipital oligoastrocytoma measuring 5 · 5 · 6 cm in 2006. Postoperatively, he sustained a right posterior cerebral artery stroke. Visual acuity was 20/20 in both eyes, and visual fields demonstrated a complete left HH. The rest of his neuro-ophthalmic examination showed normal results. Both patients were otherwise intact neurologically without evidence of neglect or cognitive impairment. In both cases, VFs were assessed monocularly using Humphrey visual field 24-2 SITA Fast with a size-III stimulus. Kinetic perimetry was performed using dynamic mapping and static perimetric probing with a size-III stimulus. Visual fields were reassessed at multiple time points to confirm stability of the HH. Kinetic perimetry was assessed both monocularly and binocularly with and without the prisms. Fixation was monitored closely for any saccades into the blind hemifield. Case 1 had a left HH with 95° and 65° angle of remain-ing horizontal VF in the right and left eyes, respectively, and FIG. 1. Two 57-PD prism segments placed at the upper and lower part of the eyeglass lens ipsilateral to the visual field loss with the central edges at the level of the limbus, spanning the entire width of the lens. The individual prism segments are placed obliquely at 45° angle to the horizontal with the upper prism oriented base out and down and the lower prism oriented base out and up. FIG. 2. Case 1. Top, kinetic perimetry of each eye without prisms. Bottom, binocular kinetic perimetry with prisms. 54 Moss et al: J Neuro-Ophthalmol 2014; 34: 53-56 Clinical Observation Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. 95° angle binocularly. With the use of the prism system, the binocular VF increased to 115° angle of continuous, horizontal VF (Fig. 2). Case 2 had a left HH with 79° and 40° angle of remaining VF in the right and left eyes, respectively, and 82° angle binocularly. With the use of the prism system, the binocular VF increased to 112° angle of continuous horizontal VF (Fig. 3). Both patients reported an immediate improvement in their VF and spatial aware-ness and rapidly adapted to the prisms over several weeks. Although no standardized questionnaire or formal assess-ment was conducted, both patients noted significant improvement in quality of life. They denied diplopia and visual confusion and reported satisfaction with their prism glasses. Case 1 passed an on-road driver evaluation admin-istered by a driving rehabilitation specialist after several weeks of adapting to the prisms. Case 2 began driving after adapting to the prisms for approximately 6 months. Each holds a valid driver's license in the state of Minnesota and has successfully operated a motor vehicle without any restrictions or accidents for 1 and 5 years, respectively. DISCUSSION Optical devices can provide field-of-view relocation or expansion. Relocation simply shifts the position of the scotoma (binocular sector prisms), whereas expansion actu-ally allows the patient to monitor a larger amount of his environment at any given moment (monocular peripheral prisms). The peripheral placement of the prisms avoids diplopia that could occur with prisms in the visual axis. The oblique orientation of the prisms creates overlapping fields along the horizontal meridian, which may produce superior augmentation of continuous horizontal VF (Fig. 4) as required by most driver licensing agencies. These findings have led to a multicentered randomized clinical trial of these lenses in patients with HH (4). FIG. 3. Case 2. Top, kinetic perimetry of each eye without prisms. Bottom, binocular kinetic perimetry without (left) and with (right) prisms. Moss et al: J Neuro-Ophthalmol 2014; 34: 53-56 55 Clinical Observation Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. Augmentation of VF in a patient with a HH using monocular sector prisms is not surprising, but we have shown that our patients achieved the 105° VF requirement from the Department of Motor Vehicles in Minnesota. There are conflicting data regarding quantifying the impact of VF loss on the ability to operate a motor vehicle. In patients with glaucoma, it has been documented through the use of driving simulators and real-world self-reported data that having a horizontal VF of 100° angle or less is associated with a significantly higher risk of accidents (5). In patients with HH, Bowers et al (6), using a driving simulator, showed a decreased blind-side detection of obstacles, while Niehorster et al (7) employed visual displays to demonstrate a reduction in visual motor control. However, Wood et al (8,9), using on-road driving performance, have reported that some indi-viduals with homonymous VF defects may be safe to drive. Further study is required to better define the relationship of driving simulators to on-road performance and to determine the minimum VF required to drive safely. The state of Minnesota requires that individuals have at least 105° angle of horizontal VF to obtain a license to operate a motor vehicle (1). Both of our patients were able to meet these requirements with the use of the prism system and subsequently have been driving accident free. To the best of our knowledge, the oblique orientation of the peripheral prism segments to meet the driver license requirements has not been reported. It should be emphasized that patients with HH may benefit from a training and adaptation period dur-ing which they learn to safely utilize their prism system before driving on the open road (10). We acknowledge the limitations of our report. We only evaluated 2 patients with HH. Both were young without other neurological deficits. Our findings may not be generalizable to all patients with a HH, particularly older patients or those with cognitive impairment or neglect. Nevertheless, clinicians should consider using this prismatic system in patients with HH as a potential aid in obtaining a driver's license to operate a motor vehicle. REFERENCES 1. Office of the Revisor of Statutes. Minnesota Administrative rules. Available at: https://www.revisor.mn.gov/rules/? id=7410.2400. Accessed June 6, 2013. 2. Peli E. Field expansion for homonymous hemianopia by optically induced peripheral exotropia. Optom Vis Sci. 2000;77:453-464. 3. Bowers A, Tant M, Peli E. A pilot evaluation of on-road detection performance by drivers with hemianopia using oblique peripheral prisms. Stroke Res Treat. [published online ahead of print December 20, 2012] doi: 10.1155/2012/ 176806. 4. Clinical trial of peripheral prism glasses for hemianopia. Available at: http://www.clinicaltrials.gov/ct2/show/ NCT00494676?term=NCT00494676&rank=1. Accessed January 27, 2013. 5. Szlyk J, Mahler C, Seiple W, Edward DP, Wilensky JT. Driving performance of glaucoma patients correlates with peripheral visual field loss. J Glaucoma. 2005;14:145-150. 6. Bowers AR, Mandel AJ, Goldstein RB, Peli E. Driving with hemianopia: I. Detection performance in a driving simulator. Invest Ophthalmol Vis Sci. 2009;50:5137-5147. 7. Niehorster DC, Peli E, Haun A, Li L. Influence of hemianopic visual field loss on visual motor control. PLoS One. 2013;8: e56615. doi: 10.1371/journal.pone.0056615. 8. Wood JM, McGwin G, Elgin J, Vaphiades MS, Braswell RA, DeCarlo DK, Kline LB, Meek GC, Searcey K, Owsley C. On-road driving performance by persons with hemianopia and quadrantanopia. Invest Ophthalmol Vis Sci. 2009;50:577-585. 9. Wood JM, McGwin G, Elgin J, Vaphiades MS, Braswell RA, DeCarlo DK, Kline LB, Owsley C. Hemianopic and quadrantanopic field loss, eye and head movements, and driving. Invest Ophthalmol Vis Sci. 2011;52:1220- 1225. 10. Szlyk J, Seiple W, Stelmack J, McMahon T. Use of prisms for navigation and driving in hemianopic patients. Ophthalmic Physiol Opt. 2005;25:128-135. FIG. 4. Case 2. Kinetic perimetry of the left eye using peripheral prism segments placed above and below the visual axis with the prisms oriented horizontally (left) and obliquely (right). The oblique orientation results in greater improvement in continuous horizontal visual field. 56 Moss et al: J Neuro-Ophthalmol 2014; 34: 53-56 Clinical Observation Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. |
