Original paper
Nott and MEM dynamic retinoscopy: Can they be used interchangeably?

Introduction:
Previous studies suggest that monocular estimate method (MEM) and Nott retinoscopy yield identical results in the assessment of the accommodative lag. However, two recent studies suggested that the accommodative lag measured with MEM retinoscopy is twice that with Nott. This study was designed to re-evaluate the agreement of MEM and Nott retinoscopy techniques.
Material and methods:
One hundred and thirty (130) subjects aged between 18 and 30 years (22±3 years – mean ±SD), with no history of contact lens wear, ocular and systemic disease or ocular surgery, participated in the study. Nott and MEM Retinoscopy were used to assess the lag of accommodation through the Corrected Ametropia Most Plus (CAMP) subjective refraction at 40 cm.
Results:
The mean difference between both sessions for Nott retinoscopy was 0.01±0.1 D (mean ±SD). The mean difference between both sessions for MEM retinoscopy was – 0.002±0.11 D (mean ±SD). The mean difference between Nott and MEM dynamic retinoscopy was 0.01±0.13 D (mean ±SD) with 95% limits of agreement ranging between +0.26 and -0.25 D. For both Nott and MEM, there was no significant difference (P>0.05) of the measured lag between the four measurement sessions and no significant difference (P>0.05) was found between both methods.
Conclusions:
We conclude that in normal healthy subjects with normal accommodative and binocular function, MEM and Nott dynamic retinoscopy techniques may be used, interchangeably, to assess the lag of accommodation at 40 cm.