Abstract

SA.27.04

A new device for testing distance corrected near visual acuity under standardized circumstances – The Salzburg Reading Desk (SRD)

Dexl A., Schlögel H., Wolfbauer M., Grabner G.
University Eye Clinic, PMU Salzburg, Austria

Objective: To develop a new device for testing NVA parameters, such as reading acuity (RA), reading speed (RS) and critical print size (CPS) under maximally standardized conditions.
Methods: In most clinical studies concerned with the outcome of surgical procedures (e.g. correction for presbyopia), RA is the main target. A comparison between different centres can only be performed with adequate testing methods and meticulous standardization. A device for testing NVA under very standardized circumstances is clearly needed to be able to objectively compare results in different studies. Based on the “Radner-Reading-Charts (RRC)”, we developed the SRD for testing NVA (RA, RS and CPS) under standardized illumination. The reading distance (RD) - by far the most critical parameter in testing NVA - seems to be quite variable for every patient tested, when trial subjects are allowed to freely choose a subjectively convenient distance. Thus measuring NVA at a given, fixed distance does not allow one to draw conclusions on the “every day reading ability” of patients. Therefore the continuously changing RD is also continuously monitored by stereo-photometry and is mathematically taken into consideration. The reading angle, an additional variable parameter, can be chosen freely and adjusted by the patient.
Results: Testing for validity and reliability has been performed with 2184 single measurements in distances between 16 and 63 cm, and reading angles between 0° and 40°. Based on the RRC an error range between logRad 0,004 at 63 cm and logRad 0,016 at 16 cm has been found (this amount is of no clinical relevance).
Conclusions: With this standardized device it is possible to obtain objective, valid and comparable results as far as the true “reading abilities” of trial subjects are concerned. This encompasses RA, RS and CPS. Studies testing NVA following several surgical methods for the correction of presbyopia are currently initiated in Salzburg with the use of the SRD in order to firmly establish the validity of this refined method for NVA evaluation.

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