Anterior Segment Refractive
Figure 4: The Variety of Images Used to Collect Data in the System
1. Near
the outcomes of various surgeries for presbyopia (multifocal IOLs, accommodative IOLs, conductive keratoplasty, scleral bands or laser keratorefractive surgery).
The system is easy to use, relatively time-efficient (a five-minute time test) and the results are easily understandable. Patients hold the tablet PC in their hands and select the answers with the tip of a pointer on the touchscreen.
Tests that are featured in the device are EyeVisPod tests, near visual acuity measurement, reading speed and comprehensive test, social reading quality, photic phenomena calculator and automatic defocus curve. The tests are usually administered sequentially.
2. Newspaper
First, near visual acuity is measured with the patient positioned 40cm away from the screen. A series of progressively smaller letters are shown and the patient stops when no longer able to read them (see Figure 2). The size of the letters is presented in multiple systems simultaneously. They are shown inside the red ellipse. This value is recorded by the Eyevispod.
3. Intermediate
The next test is reading speed. The program comes in seven languages and reading passages are rated as low, medium and high difficulty. Once the patient begins reading the passage, a stopwatch on the Eyevispod is started and then stopped at the end of the passage. The reading speed is then automatically calculated and recorded. Afterwards, the patient is asked a series of questions to estimate their comprehension of the passage. We believe that measuring reading speed in such way is the best measure for near vision performance (see Figure 3).
Measuring reading speed without testing reading comprehension can be misleading; transmitting information to the brain is an essential task of visual function. If we do not test comprehension, we would not know whether the patient was rushing his or herself for the test, without actually allowing enough time to comprehend what they were reading as they would in a real-life situation. What we really want to assess is the functional everyday reading speed, which is that speed at which the patient is able to still concentrate enough to understand the text.
Social Reading Evaluation
The next test is a series of everyday visual tasks that are often problematic for presbyopic patients. Standardised images are presented on the tablet PC, both pre- and post-operatively. Several examples of these commonly problematic objects are reproduced on the screen and divided into three categories: near vision (reading newspapers), intermediate vision and photopic phenomena.
In the near vision category, there is an entire set of near images devoted to newspapers. It includes titles, subtitles, body text, different paper colours and the ‘financial section’, in which numbers and tables are usually printed in the smallest fonts. The intermediate vision category contains examples of images from intermediate distance daily tasks. These include a full-size car dashboard, door plates, price tags, nutrition information labels, road maps and a music score (see Figure 4). All are actual size images, which allow us to directly test the patient’s everyday social visual performance at both near and intermediate distances. In the last category, diffractive images and aberrations are simulated with various degrees of severity. Patients select the images that most closely replicate their own night
48 EUROPEAN OPHTHALMIC REVIEW
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