Evaluating Calibrated Retinoscopy

Abstract

 

Purpose

 

To evaluate the accuracy of a 6-8° off axis mathematically based retinoscopic technique using calibrated converging light to produce a +0.50D retinoscopic endpoint, the retinoscopic measurements were compared to those of a subjective refraction. The optical clarity of the +0.50D retinoscopic endpoint was also compared to an infinity endpoint using diverging light.

 

Methods

 

A Copeland Optec 360 Streak Retinoscope (Fig. 1) was calibrated for a 65cm retinoscopic working distance (RWD) and marked for a +0.50D retinoscopic endpoint using +1.00D converging light (CCR_+050D) and a infinity retinoscopic endpoint (∞) using -1.50D diverging light. Slide locks maintained the alignment of the calibration line with the marked positions. The CCR_+050D retinoscopic technique uses the principles of conventional retinoscopy and doesn’t require a fogging lens. With a phoropter, twenty-six normal and abnormal eyes of patients aged 11-77 with undilated pupils were retinoscoped using the CCR_+050D technique as they read the Snellen chart. The +0.50D endpoint was compared to the infinity endpoint by adding a +1.50D sphere and elevating the calibration line from the +0.50D position to the ∞ position with the thumb slide. A subjective refraction was performed and the results compared to the CCR_+050D measurements.

 

Results

 

The mean differences and 95% confidence intervals between the spherical equivalents (SE) and crossed cylinders (X/Cyl) of the CCR_+050D endpoints and subjective refractions were: 0.03(-0.21 to +0.21)D_SE and 0.00(-0.21 to +0.21)D_X/Cyl. The +0.50D pupillary reflexes were brighter, sharper and easier to evaluate than the dull infinity pupillary reflexes.

 

Conclusions

 

The results indicate a high degree of accuracy for the CCR_+050D technique in contrast to the accuracy/repeatability studies of conventional retinoscopy. This is due to the calibrated visible retinoscopic endpoint plus eliminating the fogging lens, the 0.50D zone of doubt, the dull undetectable infinity endpoint, cycloplegics and other disadvantages of conventional retinoscopy. Since retinoscopes are the only uncalibrated instruments used to measure a refractive error, they can produce different spherical measurements and many cannot be calibrated. The clear CCR_+050D endpoint should improve the efficiency of the office and make retinoscopy easier to perform and teach.

 

 

Fig. 1 Retinoscope calibrated for CCR_+050D and infinity pupillary reflexes and the RWD.

 

Keywords: 718 spectacle lens • 754 visual acuity • 672 reading