Pilot study on dry eye affecting the accuracy of intraocular lens power measurement in age-related cataract

Background

The incidence of dry eye is gradually increasing, and the aging of population is one of factors. Researches showed that the change of tear film stability leads to shift of corneal refractive power, which probably affects the measurement of intraocular lens (IOL) power. The influence of dry eye on the calculation of IOL power is worth paying close attention.

Objective

This study was to investigate the influence of dry eye on the accuracy of IOL power calculation in age-related cataractous patients.

Methods

A non-randomized controlled clinical study was performed. Two hundred and sixteen eyes of 216 cataract patients were enrolled in Yanbian Eye Ear Nose and Throat Hospital from May 2013 to February 2014. The visual acuity, intraocular pressure, break up time of tear film (BUT), SchirmerⅠtest (SⅠt) and corneal fluorescein staining were examined in all the eyes, and then the patients were assigned to mild dry eye group (73 eyes), severe dry eye group (68 eyes) and non-dry eye control group (75 eyes). The axial length (AL) and anterior chamber depth (ACD) were measured using IOL Master for the calculation of IOL power and K value (corneal curvature). Phacoemulsification with IOL implantation was performed on all the eyes, and the refractive power was measured with KR 8100 automatic optometry 2 months after operation. The mean absolute refractive error (MARE) between actual refraction and predicted refraction was calculated, and percentage of eyes in different refractive error ranges was compared between the dry eye group and non-dry eye control group. The correlations of dry eye-related parameters with peroperative K value and refractive error were analyzed. This study was approved by the Ethics of Yanbian University, and written informed consent was obtained from each subject prior to entering the cohort.

Results

No significant differences were found in age, gender, AL, ACD and MARE among the mild dry eye group, severe dry eye group and non-dry eye control group (all at P>0.05), and significant differences in BUT, SⅠt and corneal fluorescein staining scores were found among these three groups (F=5.460, 4.521, 3.572, all at P<0.05). The K values were (43.59±1.39), (44.66±1.53) and (43.42± 1.32)D in the mild dry eye group, severe dry eye group and non-dry eye control group, and the K value in the severe dry eye group was significantly higher than that in the non-dry eye control group (P=0.012). The percentage of eyes with + 0.50-+ 0.75 D deviation was significantly elevated(28.8% versus 13.3%), and that with -0.50–0.75 D deviation was significantly declined (17.3% versus 28.0%)in the dry eye group compared with non-dry eye control group (χ²=4.513, P=0.032; χ²=4.236, P=0.037). A negative correlation was found between BUT and K value (r=-0.204, P=0.011).

Conclusions

Dry eye affects the accuracy of the determination of IOL power. Compared with the preoperative refraction predictive value, the postoperative refraction shift toward hyperopia.