Interocular difference in axial length raises odds of postoperative refractive error

This retrospective cohort study analyzed whether differences in ocular biometry measurements between eyes could predict refractive outcomes after cataract surgery.

Study design

Researchers reviewed the charts of 729 patients (1,458 eyes) who underwent sequential bilateral clear corneal phacoemulsification at a surgery center in Canada between 2013 and 2015. Interocular axial length and corneal power were measured using the IOL Master 500 (Carl Zeiss AG).

The primary outcome was the difference of 0.5 D of refractive error from refractive target. Analyses also included 0.25 D and 1.0 D from targets and patients with uncorrected visual acuity (UCVA) greater than 0.3 logMAR.

Outcomes

When stratifying the primary outcome by interocular axial length differences, 70% of eyes were within 0.5 D of refractive target for interocular axial length (AL) differences greater than 0.4 mm. In comparison, 80% of eyes with interocular AL difference less than 0.4mm were within 0.5 D of refractive target.

Interocular differences in corneal power did not associate with declining refractive error from target but did correlate with worse UCVA.

Limitations

The study did not evaluate interocular axial length and corneal power differences by more than one biometry instrument or other adjunctive devices. Also, measurements were not repeated.

Clinical significance

When biometry detects significant interocular differences between axial length and corneal power measurements, physicians can better counsel patients on realistic expectations of refractive outcomes.