Intraocular Lens Calculation In An Eye With Intrastromal Corneal Ring Segments

To report the intraocular lens (IOL) power calculation and outcome of cataract surgery with IOL implantation in a patient who underwent intrastromal corneal ring segments (ICRS) for myopia treatment.

A patient with bilateral ICRS for myopia underwent bilateral sequential phacoemulsification and intraocular lens implant with monofocal toric lenses.

To our knowledge, there’s no published methodology of IOL calculation for eyes with previous ICRS for myopia. We present a 68-year-old man who had ICRS (KeraVision ring) implanted in both eyes for myopia 26 years ago. He presented to us with visually significant bilateral nuclear sclerosis cataracts. His corrected distance visual acuity (CDVA) was 6/30 for the right eye (OD) and 6/24 for the left eye (OS). Phacoemulsification and intraocular lens implantation was performed in both eyes. Target refraction was for monovision; OD was aimed for emmetropia, and OS aimed for -2.0 diopters (D). Our approach was to use post-myopic LASIK formulas with measured posterior keratometry (PK), and a monofocal toric lens (AT TORBI 709MP). IOL formulas used were the Barrett True-K total keratometry (TK) formula, which predicted -0.06 Spherical equivalent (SE) for +11.50D 2.0cyl OD, and -1.80 SE for +14.25D 2.5Cyl OS, and EVO 2.0 post-LASIK formula with measured PK which predicted +0.07 SE for +11.25D 1.5cyl OD, and -1.88SE for +14.50D 2.0cyl OS. If non-LASIK formulas were used, both the Barrett Universal II formula (0.0SE for +10.5D 3.0cyl for OD and -1.86SE for +13.75D 2.5cyl OS) and EVO 2.0 (-0.17SE +10.75D 2.5cyl for OD and -2.03SE for +14.0D 2.0cyl for OS) predicted a more hyperopic outcome. Both eyes were eventually implanted with +11.25D 1.5cyl for OD, and +14.5D 2.0cyl for OS. Postoperatively, SE was +0.25D (OD) and -2.25D (OS).

Using post-myopic LASIK formulas with measured PK for a patient with previous ICRS for myopia had accurate outcomes (within +0.5D of predicted refraction).