Background In some situations it is necessary to use biometry from the fellow eye
for lens power calculation prior to cataract surgery. The purpose of this study was
to analyse the lateral differences in biometric measurements and their impact on the
lens power calculation. Methods The analysis was based on a large dataset of 19,472
measurements of 9736 patients prior to cataract surgery with complete biometric data
of both left and right eyes extracted from the IOLMaster 700. After randomly indexing
the left or right eye as primary (P) and secondary (S), the differences between S
and P eye were recorded and analysed (Keratometry (RSEQ), total keratometry (TRSEQ)
and back surface power (BRSEQ)), axial length AL, corneal thickness CCT, anterior
chamber depth ACD, lens thickness LT). Lens power was calculated with the Castrop
formula for all P and S eyes, and the refraction was predicted using both the P and
S eye biometry for the lens power calculation. Results Lateral differences (S-P, 90%
confidence interval) ranged between -0.64 to 0.63 dpt / -0.67 to 0.66 dpt / -0.12
to 0.12 dpt for RSEQ / TRSEQ / BRSEQ. The respective difference in AL / CCT / ACD
/ LT ranged between -0.46 to 0.43 mm / -0.01 to 0.01 mm / -0.20 to 0.20 mm / -0.13
to 0.14 mm. The resulting difference in lens power and predicted refraction ranged
between -2.02 to 2.00 dpt and -1.36 to 1.30 dpt where the biometry of the S eye is
used instead of the P eye. The AL and RSEQ were identified as the most critical parameters
where the biometry of the fellow eye is used. Conclusion Despite a strong similarity
of both eyes, intraocular lens power calculation with fellow eye biometry could yield
different results for the lens power and finally for the predicted refraction. In
10% of cases, the lens power derived from the S eye deviates by 2 dpt or more, resulting
in a refraction deviation of 1.36 dpt or more.
