Retinoscopy measurement differences as a variable of technique.

A study was made to check the reliability of dynamic retinoscopy findings in a modification of the bell retinoscopy technique. The study was to compare findings between two examiners, the authors. Selected subjects in the test sample were retested to determine if the retinoscopy techniques were a variable. One examiner was measuring the light shadow edge of the beam with rather large sweeps of the instrument. The other was measuring the very center of the beam with very small, rapid sweeps of the instrument. The retest data confirm that the technique differences could account for at least 3.50 D difference at the 40 cm test distance. Retinoscopy is one of the basic optometric test procedures for objectively evaluating the optical status of a patient. All of the optometry schools in the United States emphasize both the theoretical and applied aspects of this test procedure in their curricula. Yet some men in optometric practices view retinoscopy findings with doubts and reservation. Many optometrists express a lack of confidence in their ability to interpret the results of dynamic skiametry, particularly the techniques commonly referred to as “book retinoscopy” and “dangle bell retinoscopy.” They question the reliability of these techniques. One of the more disturbing elements of these private “confessions” is that the doubters are often the most competent and thorough clinicians. The present study was carried out to determine the reliability of modified bell retinoscopy findings. We tested the same subjects, using presumably the same procedures and identical instruments, under the same conditions. The tests were modifications of the bell retinoscopy procedure. The data revealed that the findings of the two optometrists were not the same, despite the standard conditions. It was then hypothesized that the different results were due to variation of retinoscopy procedures of the examiners. Additional testing did show that there were two significant test factors not initially recognized. These were: 1) what area of the reflex examiner was looking at during the administration; 2) how he moved his instrument during the procedure.