Autorefraction/autokeratometry and subjective refraction in untreated and photorefractive keratectomy-treated eyes
K. D. Oyo-Szerenyi, L. Wienecke, U. Businger and I. Schipper
Lucerne Eye Clinic, Cantonal Hospital, Switzerland.
OBJECTIVE: To examine the relative accuracy of autorefraction and
autokeratometry (autorefraction/autokeratometry) and subjective refraction
in untreated and photorefractive keratectomy (PRK)-treated eyes. DESIGN:
Results of autorefraction/autokeratometry obtained by means of 2
contemporary devices (Nidek ARK 2000 and Canon Rk-3) were compared with
those of subjective refraction in 48 untreated eyes and in 78 eyes treated
with (PRK). RESULTS: A trend toward greater differences between subjective
and objective methods in PRK-treated eyes was observed. Both autorefraction
devices showed similarly higher differences from subjective readings in
PRK-treated eyes with regard to sphere (P < .001) and cylinder (P =
.02), but not axis (P =.4). For autokeratometry, the mean difference from
manual readings was highly significant when all K readings were considered
together, but not so for the individual differences in keratometric
astigmatism (Canon RK-3 and Nidek ARK 2000 vs manual results: P =.03 and P
=.93, respectively) and keratometric axis (Canon RK-3 and Nidek ARK 2000 vs
manual results: P =.88 and P =.19, respectively). CONCLUSIONS: Refractive
and keratometric readings obtained with the automated devices tested in
this study varied more from those obtained with subjective methods when the
eyes examined had been treated with PRK. Corneal topographical changes
inherent in the wound-healing process may influence objective measurement
with automated devices.
