Stability of graft refractive power after penetrating keratoplasty

Patients needing penetrating keratoplasty (PK) and cataract extraction with intraocular lens (IOL) implantation may be handled with a single triple procedure or a two-stage procedure with initial keratoplasty and cataract surgery in a later session. The latter approach is considered more safe by some surgeons and allows adjustment of the IOL power to the power of the actual corneal graft. The purpose of this study was to estimate the optimal timing of cataract surgery with IOL implantation by studying the refractive stability of 8 mm penetrating keratoplasty grafts.

Penetrating keratoplasty (8.0 mm graft and recipient bed) was performed in 28 eyes of 28 patients. Corneal topography (TMS-1) was studied at 1, 2, 3, 6, and 12 months after surgery and after suture removal (30 months). The central spherical equivalent graft power was computed from the topographical data (rings 2 through 4).

On average, the spherical equivalent graft power was stable from one month after surgery up to suture removal (range: 41.9 to 42.7 diopters). After suture removal the graft steepened slightly (0.7 diopters). Corneal refractive power of single grafts fluctuated considerably over time. The standard deviation on time-dependent changes in graft power was from 3 months efter PK smaller than the standard deviation on the graft powers at 12 months.

The average central spherical equivalent power of an 8.0 mm donor graft in an 8.0 mm recipient bed was stable from one month after penetrating keratoplasty until suture removal. A two-stage procedure with cataract surgery performed 3 months after PK can, compared to the triple procedure, reduce postoperative ametropia at 12 months if graft topography is taken into consideration at the time of cataract surgery. We recommend that cataract surgery with IOL implantation takes place from 3 months after penetrating keratoplasty.