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Autorefractometry in high myopes with small optical zones less reliable after LASIK, study says
Am J Ophthalmol. 2010;150(6):774-779.
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Autorefractometry was shown to be less reliable after myopic LASIK when compared to autoreactometry in non-operated eyes, a study found.
"The reliability of the [automated refraction] is influenced by the [optical zone] and the preoperative amount of myopia, with a small [optical zone] and high myopia resulting in a greater difference between [automated refraction] and [subjective refraction] and with the [automated refraction] determining more myopic results," the study authors said.
The retrospective study included 250 eyes of 132 patients who underwent LASIK for myopia or myopic astigmatism. Mean patient age was 37 years.
Differences between automated objective refraction and subjective refraction were calculated 1 month after surgery. Patients were grouped according to degree of preoperative myopia and excimer laser optical zone size.
Study results showed a correlation coefficient between automated and subjective refraction of 0.98 before surgery and 0.79 after surgery; the difference was statistically significant (P < .001). Data showed a statistically significant mean difference between spherical equivalents of 0.13 D preoperatively and –0.3 D postoperatively (P < .001).
Postoperative differences between measurements were –0.61 D in eyes with an optical zone of 5 mm to 5.5 mm, –0.36 D in eyes with an optical zone of 5.6 mm to 6 mm, and –0.16 D in eyes with an optical zone of 6.1 mm to 7 mm.