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BLOG: The future of objective functional near vision assessment: reading speed
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Visual acuity is still measured using tools developed more than 150 years ago: the Snellen eye chart, developed in 1862, and the Jaeger near vision chart, first printed in 1867. We have long known these tools are imprecise. Patients with 20/20 acuity can nevertheless have a range of visual quality and visual function.
Surely an update to the metrics by which we evaluate vision, using more advanced technology, is warranted. Researchers are currently exploring a number of interesting ways to do this, from double-pass wavefront technology that can measure the amount of forward light scatter to the retina tracking measures of visual function such as objectively measuring reading speed.
We obtained the first Salzburg Reading Desk (SRD, SRD Vision) in the United States to validate this technology for understanding near and intermediate performance of reading tasks with presbyopia-correcting IOLs. This technology was developed by Günther Grabner and colleagues in Austria and has been validated as an objective, standardized way to evaluate reading acuity at various distances.
We conducted a pilot study in 20 eyes of 10 pseudophakic patients, including seven with bilateral Tecnis Symfony (Johnson & Johnson Vision) extended depth of focus IOLs and three with a “personalized vision” combination of the Symfony in the dominant eye and the Tecnis multifocal (Johnson & Johnson Vision) +3.25, a mid-add diffractive bifocal, in the nondominant eye. We measured uncorrected monocular distance and near, monocular and binocular reading acuity in logMAR, and monocular and binocular reading speed (words per minute, wpm) at 40 cm (near) and 66 cm (intermediate) in high-contrast, high-luminance conditions to gain a better understanding of visual function with these IOLs.
Monocular UNVA was better in the eyes with diffractive bifocal IOLs (0.02 ± 0.04 logMAR vs. 0.25 ± 0.19 logMAR, P = .03), and no difference was observed in UDVA. When we looked at the functional reading speed analysis, we demonstrated objectively a summation effect in both binocular circumstances. Reading speed and acuity improved when patients used both eyes, in both the bilateral EDOF patients and the personalized vision patients. The results of this pilot study support the concept that binocular summation has additional benefits for presbyopia solutions such as increased reading speed.
I look forward to expanding this knowledge with larger-scale prospective studies to understand the relative magnitude of the improvement in reading speed with each lens option. In order to push the limits of visual performance with new IOL technologies, we should embrace more advanced ways of measuring visual acuity and performance.
References:
de Stefano VS, et al. Comparison of reading performance analysis of diffractive presbyopia correcting intraocular lenses using an electronic reading acuity device. Presented at: American Society of Cataract and Refractive Surgery annual meeting; May 3-7, 2019; San Diego.
Hirnschall N, et al. J Cataract Refract Surg. 2014;doi:10.1016/j.jcrs.2013.12.021.
Disclosure: Waring reports he is a consultant for Johnson & Johnson Vision and a member of the Johnson & Johnson Vision optics advisory board.