Researchers in Spain have demonstrated a handheld optoelectronic device that will allow patients to experience how a certain implanted lens would affect their vision by simply looking through it.
Described in journal Optica, the simultaneous vision simulator – or SimVis – could help patients test artificial lens designs before they have surgery.
In the last decade, lens companies have designed intraocular lenses that not only replace the cloudy lens of the eye but can also correct the patient’s vision, to reduce the need for glasses.
Current implanted intraocular lenses are monofocal – they correct only far vision, which creates sharp vision for far-away objects but blurred vision for objects close by. There are also newer multifocal lenses that focus both near and far objects onto the retina at the same time, but with some loss of image quality and contrast for both near and far distances. The choices for monofocal, bifocal and multifocal intraocular lenses keeps growing as more designs enter the market.
‘Currently, the decision on which intraocular lens is implanted during cataract surgery is typically based on the explanations and experience of the surgeon,’ said Carlos Dorronsoro, first author of the paper. ‘But it is difficult for patients to imagine the new visual experience provided by some of these lenses, therefore, it is very difficult to make the decision.’
The SimVis uses an optoelectronic tunable lens that changes shape in response to an applied electric current. To simulate multifocal lenses, the shape of this tunable lens can be switched so quickly that the resulting oscillations in focal positions can’t be perceived by human vision. A patient looking through the device would see near and far distances in focus at the same time, as well as experiencing the loss of image quality and contrast that comes with multifocal lenses.
To test the vision simulator, the researchers asked nine volunteers to use the SimVis to compare seven different lenses providing monofocal, bifocal or trifocal corrections while looking at a poster of a landscape, a laptop, a tablet, and a smartphone, with high contrast text and eye charts placed at different distances. Based on the lens simulations, the testers indicated clear preferences for certain corrections.
‘The favoured or rejected lenses were different for different testers, suggesting the need for this kind of simulation prior to surgery to customise the selection of lenses according to patient requirements,' said Dorronsoro. ‘Clinical use of the SimVis could provide an evidence-based way to assess the subjective needs and preferences of patients before they undergo cataract surgery.’
The researchers are now working on a binocular version of the SimVis that is smaller and can simulate different lenses in each eye. Appearing much like a virtual reality helmet, this new version of the SimVis will also be lighter and have a wider field of view than the device demonstrated in the Optica paper. The researchers are working to complete the necessary clinical validations so that the binocular version of SimVis can be sold commercially by next year.
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