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‘Slow Fast’ evaluation provides complete data on visual performance
The system could become another option for evaluating near vision results from refractive lens exchange and presbyopic surgeries.
ROME – A computerized system provides detailed assessment of near visual performance in patients with or without intraocular implants, overcoming the limitations of traditional visual acuity charts, according to an investigator.
“The problem we have with traditional systems is that results are hardly correlated with real-life vision and cannot take into account the variety of everyday situations that are normally encountered by our patients, such as shopping, going to restaurants or driving a car. Problems that are commonly reported, such as glare and halos, also have no way of being objectively measured and documented during our routine examinations,” said Nicola Hauranieh, MD. She described the new testing system at the European Society of Cataract and Refractive Surgeons Winter Refractive Surgery Meeting.
Through simulation of the most common visual tasks and visual problems on a laptop computer, and by processing the data of a series of subsequent tests, the “Slow Fast” system offers a comprehensive assessment of near and intermediate visual function.
The computer then gives a percentage score of the patient’s visual performance that allows a functional assessment of near vision preop and postop.
“The score is very useful for practical, legal purposes, and to compare the outcomes of different surgeries for presbyopia, such as multifocal and accommodative IOLs, CK, scleral and laser surgeries,” Dr. Hauranieh added.
“The system is easy to use, simple, light and manageable. Patients hold the touch-screen in their hands and select the answers with the tip of a biro,” she said.
The system was created and developed by Dr. Hauranieh and Pietro Giardini, MD, of the ophthalmology department of Poliambulanza Hospital in Brescia, Italy.
Visual acuity and reading speed
The tests are divided into sessions. First, near visual acuity is measured with the patient positioned 40 cm away from the screen. A series of letters of progressively smaller size are shown, and patients stop when they are no longer able to read the letters clearly, Dr. Hauranieh said.
“We particularly insist on computer size characters, as well as print size characters, because computer reading and writing has become an important part of everyday life at all ages,” she said.
A second part of the program measures reading speed, which is “a highly significant aspect of near visual acuity, too often neglected by ophthalmologists,” according to Dr. Hauranieh. The ophthalmologist can choose between texts of three different grades of difficulty, according to the level of education of the patient. Reading speed is timed from the moment the patient starts reading the text on the screen up to the end of the last word. A comprehension test is then performed.
“Measuring reading speed without testing reading comprehension can be misleading. Transmitting information to the brain is an essential task of the visual function. If we don’t test comprehension, patients tend to rush ahead, without allowing themselves enough time to be aware of what is in front of their eyes. What we really want to assess is the reading speed that allows the patient enough concentration for understanding the text, because this is what reading is all about in real life,” she said.
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Everyday visual tasks
The next step simulates a series of everyday visual tasks, often reported to create problems for presbyopic patients.
“We have reproduced on the screen several examples of the most common potentially problematic objects, such as a full-size car dashboard, a door-plate, labels with the price of clothes or with the ingredients of food, a business card, a page from a phone book, a road map, a music score and the instruction leaflet of medications, which often presents difficulties for so many patients,” Dr. Hauranieh said. “These are life-size images, which gives the ophthalmologist the opportunity to directly test the near social visual performance of the patients in outside everyday life.”
An entire chapter is dedicated to newspapers, reproducing titles, subtitles, articles, different colored papers, and the financial page, where numbers and tables are usually printed in smaller than standard characters.
In the final part of the program, diffractive phenomena are simulated with various degrees of intensity. The patients select the images that most closely reproduce night vision.
“We start with a lit car dashboard, in and out of focus, and carry on with various images of traffic, with clear traffic lights, with narrow or large halos, starburst, glare and double vision,” she explained.
At the end of the series of tests, all the data is processed and reported in a numeric scale out of 100.
Toward standardized evaluation
“We end up with a really complete profile of the patient’s near vision, encompassing visual acuity, visual quality and visual problems. In one world, there exists the overall, real-life visual performance of the patient. Results are then filed in the computer archive included in the program and subsequently become precious documentation of the patient’s medical history, useful for the patient’s follow up and also in case of medicolegal problems. If we have tested a patient in this way before implanting an IOL, we can realistically compare visual performance and visual problems before and after the implantation,” she said.
The collected information will also be a data source for research and for comparing different IOL model performances.
This new and more complete way of testing patients also points in the direction of standardizing methods to measure near acuity.
“Standardization is something that has been advocated for a long time now and is becoming an increasingly urgent and crucial issue if we want to scientifically evaluate the results of refractive lens surgery with the implants of the latest generations,” he concluded.
For Your Information:
- Nicola Hauranieh, MD, can be reached at Casa di Cura Poliambulanza, Unità Operativa di Oculistica, Via Bissolati 57, 25124 Brescia, Italy; 39-030-3515748; fax: 39-030-3515366; e-mail: hauraniehoft@virgilio.it.
- Pietro Giardini, MD, can be reached at pgiard@inwind.it.