Effect of Baseline Corneal Hysteresis With Refractive Changes After Cataract Surgery
Purpose
To investigate the hypothesis that low corneal hysteresis (CH) is correlated with postoperative refractive error.
Methods
Retrospective chart review analyzed visual outcomes of 73 patients (121 eyes) who underwent cataract extraction with phacoemulsification and received all standard diagnostic testing. Those with previous ocular surgery and conditions affecting intraocular pressure (IOP) were excluded. Patients’ eyes were dichotomized based on expected (spherical equivalent between -.75 and +.5) and unexpected refractive outcomes ≥3 months later. Demographic and biomechanical variables of the two groups were compared using means and standard deviations of both groups as well as comparative Student T-tests. Eyes were also grouped based on low, medium, and high CH for similar analysis of refractive outcomes.
Results
67 eyes met expected refraction while 54 had unexpected changes by spherical equivalent. Spherical equivalent absolute value (SEAV) mean was 0.864 ± 0.791. Mean CH was 10.169 ± 1.858 mmHg. Among low CH eyes, there was more refractive error than high CH eyes (SEAV 0.964 vs. 0.723), though not statistically significant. Among low CH eyes, 37.5% of those with decreased IOP after surgery experienced refractive error (67% myopic, 33% hyperopic). Furthermore, among those with low CH and a postoperative increase in IOP, every patient experienced refractive error (57% myopic, 43% hyperopic). Regression analyses were negative for significant findings.
Conclusion
Though corneal hysteresis is a proven prognostic tool in glaucoma and keratorefractive surgery, this pilot study suggests CH is less useful in predicting refractive surprises after cataract surgery. Though this study’s patients with low CH had higher average refractive error, there was no significant association between CH and refractive outcome.