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[Experiences with the hand-held autorefractometer "Retinomax" in adults and children]
1Höhere Fachschule für Augenoptik, Köln.
Background:
A measurement of ametropia with a table-top mounted autorefractor can be difficult or impossible on children--especially when the children are very young or handicapped. A hand-held autorefractor, however, may be successfully applied in some of these problematic cases.
Methods:
Results of comparative measurements are presented concerning the accuracy and applicability of the hand-held autorefractor. The data were obtained on healthy young adults (100 eyes) and children (age 2-10 years, 50 eyes). In the group of adults, the autorefractor readings (obtained with a Retinomax K-plus) were compared with the results of subjective refractions. The effectiveness of the technique to relax accommodation was also evaluated. All children were measured with a Retinomax in cycloplegia. Here, retinoscopy and a conventional autorefractor served as reference methods. The accuracy of measurement was analysed by using the following criteria: "Difference of the spherical equivalents" (delta SA), "difference of the cylinder powers" (delta C), "axis difference" (delta A), and "difference of the cylindrical corrections" (delta CK).
Results:
a) Adults: On average, the spherical equivalent of the autorefractor was +0.28 D larger than the subjectively obtained value. In 88% of all cases, the difference of the spherical equivalents fell into the interval [-0.25 D, +0.75 D]. delta C and delta A were < or = +/- 0.5 D in 95% and 87% respectively. b) Children: When compared with retinoscopy, delta SA fell into the interval [-0.25 D, +0.75 D] in 72% of all cases. delta C and delta A were < or = +/- 0.5 D in 86% and 87% respectively.
Conclusions:
The accuracy of measurement of the handheld autorefractor is comparable to conventional table-top autorefractors. As it is also applicable in some problematic cases, such as small children, on whom objective refraction data can not be obtained with ordinary autorefractors, it seems to be a valuable addition to the existing set of ophthalmic refraction devices.