Celego Near Vision Test
Celego is a new type of test devised for rapid self-assessment and self-monitoring of vision at a reading distance. The test depends on the everyday observation that the time needed to read a text depends on its font size. Celego measures the smallest size allowing accurate reading within a fixed time window. The test circumvents the cultural and learning problems associated with traditional printed tests by presenting ever-new combinations of letters and digits, similar to vehicle licence plates. By using voice recording and subsequent playback the user self-scores results: no outside supervision is needed. Test results are stored internally. Once a baseline has been established, repetition allows monitoring of any changes over time.
Celego is aimed for everyone desiring to follow the state of central vision over time. Applications include monitoring previously diagnosed disorders like age-related macular degeneration and clouding of the eye-lens (cataract) and assessing the effects of various forms of treatments. Celego can also alert to a need of upgrading reading glasses.
Central vision can be affected by a multitude of disorders and differential diagnosis requires ancillary examinations. Hence, on its own, Celego cannot provide a diagnosis. What Celego can do is to precisely monitor evolution of central vision over time. Incidentally, the Celego name derives from the Latin terms for quick and reading.
Celego is CE-marked as a medical Device , Class I
Background Central vision is most commonly assessed by letter acuity charts and text-reading tests, which are used at long and short distances, respectively. There exist many variants of such tests. None is suitable for self-testing. This is because the test outcomes must be decided by an outside examiner who listens to the subject’s responses and judges their accuracy.
The Celego test delegates these tasks to the user, who dictates his or her responses following each presentation. Following the last presentation Celego replays the audio responses to allow the user to check their accuracy.
Conventional tests suffer a severe disadvantage in that they do not control testing time: everyone will perform better with an unlimited test duration than with a capped one. Standardized capping is tedious and difficult to arrange with conventional tests. Celego solves this problem by using a fixed presentation time.
Conventional reading tests suffer additional disadvantages in that cultural backgrounds and education levels may influence on the results. Further, repeated presentations may introduce unwanted gains from memorization. Celego solves these problems by using ever-new combinations of letters and digits in a format similar to familiar vehicle registration plates. The sole requirement for testing is familiarity with Latin letters and Greek digits.
The Celego test principle Celego uses the Helvetica font and holds 14 different font sizes, stepped by 0.1 log unit. In a first phase, a barely legible target size is selected manually. The actual test then presents this target size plus two smaller sizes plus one larger size, three times each, in random order, for a total of 12 presentations holding 2 “words” each. Each presentation has a duration of 2 s, corresponding to a rate of 60 words per minute.
There is a 4-second pause after each presentation. This provides ample time for the user to dictate a response. All responses are recorded in an audio file. Following the final presentation, the test enters scoring mode. Here, the targets used during testing are re-displayed in a large font size and the audio file is played back. Comparing each target with the recorded response, the user indicates whether the response was correct or incorrect. Finally, a score is calculated. The scoring principle is similar to the one often used with one of the most widely used letter acuity charts, the Early Treatment Diabetes Retinopathy Study (ETDRS) chart, and provides a maximum score of 100. Following scoring, results are plotted as a function of time.
To see the actual test procedure outlined in detail select Guide on Celego’s opening page. Here it may suffice to emphasize the need for constant test conditions to ensure maximum reproducibility.
Evaluation of test results Definition of normal outcomes in conventional tests is fairly complicated even where carefully standardized conditions have been employed. In reality, there is no magic cut-off number like the commonly touted 20/20 level: stating that 20/20 is normal is much like stating that normal shoe size is 7.
Many factors influence on normal limits, for example, age. Visual acuity typically peaks around age 25 and drops monotonically as the years pass. Further, normal subjects of one and the same age show a considerable spread of test results. This is true also for the Celego test: a recent scientific study showed that normal subjects aged 74 ± 13 (mean ± standard deviation) years obtained a score of 86 ± 9. In the same subjects, conventional acuity and text-reading tests showed similar spreads of scores, 88 ± 5 and 79 ± 7, respectively.
Not only is there a considerable spread between normal individuals but each and every individual shows variability between successive examinations. Because of normal day-to-day variation, several measurements are required to establish a reliable baseline. Actually, it is good practice to disregard the first few measurements as they may be influenced by training effects. A reliable baseline is essential for identifying trends among subsequent measurements: trends are the critical indicators of change.
In case of uncertainty of interpretation it may be useful to seek a second opinion, by using Celego’s result export function. Select PDF for graphs or CSV (Comma-Separated Values) for numerical data. Numerical data has the advantage of allowing formal statistical analysis.
Expressing results in a 0 – 100 score format is convenient but does not allow direct comparisons with results of conventional reading tests. These latter tests usually express results in terms of font sizes. However, Celego scores can easily be converted to font sizes by reference to the diagram shown below. For example, a Celego score of 70 means that a font height of minimum 1.7 millimeter (ca. 3.5 point in printer’s terminology) is required to permit accurate reading at a rate of 60 words per minute.
Please not that Celego Near Vision Test cannot provide a diagnosis. Celego monitors evolution of central vision over time.
The Celego Vision Test was developed by Lars Frisén, MD, PhD, Professor of Clinical Neuro-ophthalmology (ret), University of Gothenburg, Sweden. Website: www.neuro-o.se