Comparison between MEM and Nott Dynamic Retinoscopy

We have considered the interesting comments regarding our article by Dr. Tassinari and would like to respond to a few points made in his letter. First of all, he writes that we conclude 1 that “the insertion of supplementary measuring lenses during MEM… invalidates MEM as a measure of accommodative response.” In no place in our article do we say that the MEM method is an invalid technique. The only thing that we can assert, as is stated in the conclusions of the study, is that the dynamic retinoscopy results are different when performed MEM and Nott retinoscopy. In fact, when we consider the effects of the supplementary measuring lenses, we use the words “likely,” “must be” or “may be,” because we have not compared our results of MEM dynamic retinoscopy with an objective method to confirm such an assertion. With regard to the comments about the reasons for having different results in accommodative lag with MEM vs. Nott, we would like to make the following responses. First, certainly the test card was placed on a near-point rod at 40 cm instead of clipping the card to the retinoscope. It is clear that when performing retinoscopy with the card, the retinoscope was placed in contact with the back surface of the near-point card. This situation is the same as using the card clipped to the retinoscope. Second, regarding the use of a phoroptor for assessing the MEM retinoscopy, we state on page 651 that we used a trial frame instead of a phoroptor. Regarding the “normal reading condition” or the “patient's habitual glasses” during dynamic retinoscopy, we used the result of the subjective refractive exam, as is recommended by Scheiman and Wick. 2 The reason for this is as follows: if the patient is not wearing the results of a subjective refraction, has been overcorrected, or undercorrected, interpretation of the MEM result will be affected. For example, a MEM finding of +1.25 D is considered to represent underaccommodation. If, however, the patient is a hyperope and is not wearing his glasses (because his habitual correction is zero), the MEM finding in this case would simply reflect the presence of this uncorrected hyperopia. Similarly, an uncorrected myope might exhibit less ‘plus’ than expected on MEM retinoscopy. Third, regarding the use of the lens bar, it is true that some authors recommend the use of loose trial lenses 3, 4; however, other authors 2, 5-7 do not specify how to use the supplementary lenses. The only statement made by these authors is that the measuring lenses have to be briefly introduced so as not to alter the accommodative response (< 0.5 s, 6 0.36 s 7), as we did in our study. Finally, Dr. Tassinari states that our Nott dynamic results are equivalent to MEM results in previous studies. The references cited by him are not comparable with our results. The populations studied were different and the methods used were not the same. The sample of Rouse et al. 6 (with a mean of OD: +0.33 D, OS: +0.35 D for accommodative lag) consisted of children between 4 and 12 years old who wore their habitual spectacle corrections during MEM dynamic retinoscopy. Furthermore, they performed MEM at the habitual working distance of children, so that there were different working distances. Jackson and Goss 8 also studied a sample of children with ages between 7.9 and 15.9 years, assessing MEM dynamic retinoscopy with a phoropter (mean of accommodative lag: +0.23 D). The results of Locke and Somers 4 would be the only one comparable with ours; they studied a population with a mean age similar to that used in our sample. However, we have to consider that they only examined 10 subjects against 50 patients considered in our study. Ma del Pilar Cacho Martínez