A NEW-GENERATION OF ALGORITHMS FOR COMPUTERIZED THRESHOLD PERIMETRY, SITA

Purpose: The purpose of this work was to develop a new family of test algorithms for computerized static threshold perimetry which significa ntly reduces test time without any reduction of data quality. Methods: A comprehensive visual field model constructed from available knowled ge of normal and glaucomatous visual fields is continuously updated du ring testing. The model produces threshold estimates and also estimate s of the certainty to which the threshold is known at each point. Test ing is interrupted at each test location at predetermined levels of th reshold certainty. New time-saving methods are employed for estimation of false answers, and test pacing is optimized. After completion of t he test, all threshold estimates are re-computed, taking into account the complete body of patient responses. Computer simulations were used to optimize the different parameters of the new algorithms, to evalua te the relative importance of those parameters, and to evaluate the pe rformance of the algorithm as a whole in comparison with a standard al gorithm. Results: Simulated test results obtained with this algorithm were slightly more accurate than those of the Humphrey Full Threshold test algorithm. The number of simulated stimuli presented was reduced by an average of 29% in normal fields and 26% in glaucomatous fields. Actual clinical test time should be further reduced, since the influen ce of the improved timing algorithm was not included in the simulation s. Conclusions: We applied new methods which take available knowledge of visual field physiology and pathophysiology into account, and emplo y modern computer-intensive mathematical methods for real time estimat es of threshold values and threshold error estimates. In this way it w as possible to design a family of testing algorithms which significant ly reduced perimetric test time without any loss of quality in results .