Intraocular lens calculation in an eye with intrastromal corneal ring segments for myopia: case report

Introduction: This case report describes the approach and outcomes of intraocular lens (IOL) power calculation methods in a patient with previous intrastromal corneal ring segments (ICRSs) for myopia treatment who underwent cataract surgery. The literature on IOL calculations in eyes undergoing cataract surgery post-ICRS is scarce, with none on ICRS performed for myopia in normal eyes. Patient and Clinical Findings: A 68-year-old man had ICRS implanted bilaterally for myopia correction 27 years ago. He developed visually significant cataracts in both eyes. The measured posterior to anterior corneal radius ratio was found to be low, and average total keratometry values were lower than the average keratometry values bilaterally. These biometric parameters were similar to that of postmyopic laser vision correction (LVC) eyes. Diagnosis, Intervention, and Outcomes: Hence, IOL power calculation was made using the EVO 2.0 postmyopic LVC formula with measured posterior keratometry (PK) using IOLMaster 700. Predicted outcomes of both postmyopic LVC and non-LVC formulas were performed postoperatively. Postmyopic LVC formulas were found to be overall more accurate. Non-LVC formulas tended to have a hyperopic error. Conclusions: Using postmyopic LVC IOL formulas with measured PK may potentially be more accurate for patients with previous ICRS implantations for myopia, and whose eyes have a lower measured posterior to anterior corneal ratio.