Impact Of Tear Film Stability On Corneal Refractive Power Measurement And Surgical Planning For Cataract

To evaluate the impact of tear film stability on corneal refractive power measurement and surgical planning in cataract patients.

Prospective cohort study.

Using Keratograph 5M, patients with cataracts preoperatively were divided into dry-eye group (tear film stability level 2) and control group (level 0-1). Two consecutive valid measurements were performed using IOL Master 700 with an interval of 10 minutes. The standard keratometry (Kf, Ks and K), keratometric corneal astigmatism (KCA), total keratometry (TKf, TKs and TK) and total corneal astigmatism (TCA) were recorded. The IOL power was calculated using SRK-T, SRK-T TK, Haigis, Haigis TK, Barrett Universal II, and Barrett Universal II TK formulas. The variability between two measurements (Δ) or two calculation results, and the mean magnitude of vector difference of corneal astigmatism were calculated and compared between groups.

ΔKf, ΔKCA, ΔTKf, ΔTK, and vector variability of corneal astigmatism were significantly higher in the dry-eye group (all P < 0.05). Bland-Altman analyses showed broader 95% limits of agreement in the dry-eye group. Of all formulas, only the SRK-T formula displayed significantly higher variability in IOL power calculations in the dry eye group compared to the control group (P < 0.05).

Tear film instability can result in deviations in the measurement of preoperative corneal refractive power and corneal astigmatism. Dry eyes contribute to an increased prediction error in the IOL power calculation, especially for the SRK-T formula.