W. Happe et al., INTRAOCULAR-LENS POWER CALCULATION USING INTRAOPERATIVE RETINOSCOPY, Klinische Monatsblatter fur Augenheilkunde, 210(4), 1997, pp. 207-212
Background Preoperative biometry for calculation of the refractive pow
er of intraocular lenses is not sufficiently reliable in certain cases
. Most frequently inaccuracies tend to occur in highly myopic eyes. Pr
eceding refractive procedures can also impair IOL-calculation or even
make it impossible. Patients In a highly myopic patient IOL-power calc
ulation was not possible with conventional calculation formulas due to
a preexisting refractive silicone lens located between the cataractuo
us natural lens and the iris. In another myopic patient ultrasound mea
surement of axial eye length produced variable and unreliable results.
Therefore retinoscopy was performed intraoperatively in the aphakic e
ye. Refractive power of the IOL was calculated using a new formula. Fo
r validation of the method retinoscopy was performed intraoperatively
in a second group of 11 patients with unproblematic ultrasound biometr
y. Results In 3 eyes IOL power was chosen according to intraoperative
retinoscopy. A maximal deviation of 1.25 D from the aimed refraction r
esulted. In the second group, the retinoscopic method produced partial
ly considerably inaccurate results as compared to the ultrasound biome
try. In accuracies increased with the extent of hyperopia. Conclusions
In cases of difficult or inaccurate preoperative ultrasound biometry
IOL power can be estimated after intraoperative retinoscopy in the aph
acic highly myopic eye. IOL power can be calculated instantly using co
mputer programs or tables. This method additionally enables the surgeo
n to control the refractive result of intraocular lens implantation pr
ior to wound closure. However this method lacks reliability in higher
hyperopic eyes, as in these cases small changes in corneal vertex dist
ance of the lens used for retinoscopy highly alter the result.