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Barbara M Junghans, Siyu Liu, Yvette Yeung, Kathleen Watt, Lisa Asper; The impact of target type and verbal instructions on accommodative status during objective refraction. Invest. Ophthalmol. Vis. Sci. 2014;55(13):2716.
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In order to encourage relaxation of accommodation during objective refractive techniques such as retinoscopy, practitioners employ a variety of fixation targets and verbal instructions. There appears to be no agreement on which is the best technique. This study investigated the effect of commonly-used targets and instruction sets upon accommodative status of pre-presbyopic subjects under conditions of blur similar to that during retinoscopy.
Using a binocular open-field autorefractor (Shin-Nippon NVision-K 5001), readings were obtained for one eye of 54 subjects aged 18-34 years (mean 20.1±3.1) whilst fogged by +0.75D over their optimal distance correction and viewing a randomized presentation of 6 targets positioned 4m away (namely, a green laser speckle, the green then red the side of a duochrome chart, a green spot, a white spot, and a 20/200 E). The E was repeated under a different instructional set to particularly encourage the subject to “look far away”. Each of the 5 refractive readings per target was inspected for cylindrical consistency and any findings of >0.75DC were removed before establishing a mean spherical equivalent, consistent with the expectation of no cylinder for an over-refraction and the variance of auto-refractors. One subject then had no useable data.
On average, subjects demonstrated a slight accommodative lag for all target presentations (+0.14±0.50DS) and for both sets of instructions (0.13±0.48DS). There was no significant difference in accommodative status adopted between the 6 targets or the two sets of instructions, whether myopic (n=33) or not, or naïve to the process of objective refraction (n=38) or not. However, naïve subjects had only a very mild lag of accommodation (mean across all targets 0.07D±0.08SE) versus experienced subjects (0.30±0.11SE). Myopes exhibited a slight lead of accommodation (mean across all targets -0.04D±0.0.08SE) whereas non-myopes exhibited a lag (mean +0.41D±0.10SE).
During objective refraction using an open-field autorefractor, there is no practical difference between the commonly used targets or instructions on the accommodative response when a small fogging lens is used. We suggest that target type or instructions may similarly be of little importance during retinoscopy. Furthermore, a viewing distance of 4m appears to be effective for relaxing accommodation during objective open-field refraction
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