IMPERFECT ‘PERFECT’ VISION

20/20 uncorrected is the standard for cataract surgery outcomes today. Yet even when it’s achieved, many patients aren’t satisfied, and may even suffer significant loss of visual function, 2012 Binkhorst Medal recipient Randall J Olson MD told the annual ASCRS symposium opening session. So what drives dissatisfaction in this “20/20 unhappy†group? Dysphotopsias, including glare, shadows and doubling of vision, according to recent research presented by Dr Olson, who is CEO of the John A Moran Eye Centre and chair of the Department of Ophthalmology at the University of Utah, Salt Lake City, US.

Not only were dysphotopsias found to be statistically related to patient dissatisfaction while uncorrected visual acuity was not, dysphotopsias also correlated with loss of patient function as measured by the National Eye Institute Visual Function Questionnaire, or NEI-VFQ. But the extent and causes of post-cataract dysphotopsias are not well understood, Dr Olson said in his Binkhorst Lecture, “Where are we on the Road to Optical Perfection?†With patients increasingly demanding refractive precision, “it’s time to figure out the causes, address the concerns and come up with new products.â€

Beyond annoying

The problem isn’t new. Dr Olson recalled a patient he saw as a resident before the days of intraocular lenses (IOLs). The patient had achieved 20/20 vision with aphakic spectacles, but suffered a raft of day-to-day visual problems including disabling glare. Finally she asked Dr Olson if he had saved her cataracts – and could they be put back. “The realisation that it was that severe showed me that intraocular lenses were going to be a godsend for us as they have been.â€

But even today, patients have similar complaints after surgery. To give an impression of how disabling glare and light-scatter can be, Dr Olson noted that light hitting a dirty windshield can completely obliterate vision in an instant, and had in fact recently caused him to drive off the road. Existing studies suggest the link between dysphotopsias and dissatisfaction may be strong. In a study Dr Olson and colleagues published in the Canadian Journal of Ophthalmology, a survey of cataract patients found dysphotopsias to be much more strongly correlated with dissatisfaction, at an r value of 0.6017 (p<0.0001), than best corrected visual acuity, which was only marginally correlated at 0.2593 (p=0.040). But this study was not looking specifically at the link between dysphotopsias and dissatisfaction, Dr Olson noted. There were also many confounding pathologies in the sample that clouded the results.

To isolate the contribution of dysphotopsias to satisfaction, Dr Olson conducted a new survey including only patients with no pathologies including PCO or dry eye, uncomplicated surgery, excellent corrected vision and no complaints in the medical record at least one year after implantation of an AcrySof single piece IOL. Out of 2,953 patients operated, just 82 met all the inclusion criteria. The patients were evaluated for refractive error, logMAR visual acuity, mesopic logMAR acuity, mesopic 10 per cent acuity and mesopic 10 per cent contrast logMAR with glare. Glare was tested by placing two halogen bulbs beside the 10 per cent chart, simulating oncoming headlights. Stray light was tested with the Oculus C-Quant, the NEI-VFQ was administered to assess functional vision. A survey of the presence of dysphotopsias and a satisfaction survey were also given.

Uncorrected visual acuity did not correlate with either satisfaction or disability as measured by the NEI-VFQ, Dr Olson reported. Neither did any visual function study correlate with satisfaction or disability. The C-Quant results did correlate with mesopic 10 per cent contrast acuity, but not with visual function or satisfaction questionnaire results.

What did correlate with satisfaction were the NEI-VFQ, with an r value of -0.47 (p<0.001), and even more strongly the dysphotopsia survey, with r value -0.58 (p<0.001). “This supports our previous research,†Dr Olson said. But there was a surprise – dysphotopsias was the only thing that correlated with NEIVFQ. “This tells us that dysphotopsia is not just an annoyance, it is a dysfunction in overall visual capability,†Dr Olson said. Further analysis showed the correlation was because of dysphotopsia. “I think this takes the question to another level, that indeed for these patients it actually has an impact on their real function.â€

Biggest problems

Among the most common disabling effects were problems with bright lights, with 21 per cent of patients ranking it five or higher on a scale of 1-10, with 10 as debilitating. Temporal darkness was reported by 20 per cent with four listing it at eight or more. Peripheral light causing a central flash was noted by 40 per cent, with eight rating a five or greater. Dr Olson emphasised that these patients had never complained and had good measured visual acuity.

“We’ve got patients out there with this condition who have never complained about it. This was surprising. We thought we had done away with it by treating the edge of the lens.†Dr Olson said the results do not mean uncorrected vision and glare are not issues, they just didn’t show up in this sample, which had no acuity or PCO issues.

Emerging technologies may help eliminate postoperative dysphotopsia and refractive errors, Dr Olson said. Higher order aberrations and cylinder errors appear to be major culprits. These may be reduced through better biometry and improved formulae for calculating effective lens position, and intraoperative aberrometry to detect and correct errors during surgery. Better lens design also could help, as could dialing in results after surgery with light-adjustable lenses or manipulating lenses in situ with femtosecond lasers. “Hopefully, the era of the 20/20 unhappy patient may soon be a thing of the past.â€Â