Testing accommodation: The case for Nott dynamic retinoscopy in orthoptic assessments

Introduction: Accommodation is most commonly assessed using the RAF Rule. However, this subjective test has multiple sources of error, and an objective measurement of accommodation using Nott dynamic retinoscopy may be a more appropriate test to use. This study aimed to compare Nott dynamic retinoscopy with the RAF Rule and the Plusoptix PowerRef III (gold standard) after a period of close work, to determine whether this is a more suitable test for measuring accommodation.

Methods: Accommodation was measured in 25 students before and after 30 minutes of close work using the RAF Rule, Nott dynamic retinoscopy, and the Plusoptix. The RAF Rule measured the amplitude of accommodation when viewing N5 print. Nott dynamic retinoscopy assessed the lead/lag of accommodation using the UC Cube with N5 print at 40 cm. The Plusoptix measured objective accommodation (slope and response) in binocular and uniocular conditions.

Results: The Plusoptix and Nott dynamic retinoscopy detected accommodative lag within normal limits (under 1D), with no significant change after close work (p > 0.05). No significant change in accommodation after close work was found with the RAF Rule tested uniocularly (p > 0.05); however, a significant decrease in amplitude of accommodation from 12.85D to 11.26D was found when tested binocularly. The Plusoptix confirmed that this was not due to convergence fatigue (p > 0.05).

Discussion: The measurement variations observed with the binocular RAF Rule confirm that the subjective nature of the RAF Rule test makes it more prone to errors. Nott dynamic retinoscopy is comparable to the gold standard Plusoptix; therefore, we suggest that Nott dynamic retinoscopy should be used in the orthoptic assessment of accommodation.