Comparison Of Pentacam With Videokeratography Keratometry For Post Radial Keratotomy Intra-Ocular Lens Power Calculation

Bhushan Wadekar

Purpose: Radial keratotomy(RK) as a therapeutic modality for refractive correction of myopia is an outdated procedure. However, a phaco surgeon does encounter the challenge of providing the best possible intra-ocular lens(IOL) power in cataract patient who have undergone RK a couple of years back. We sought to compare the outcomes of application of pentacam(PC) versus videokeratography(VKG) keratometry in post-RK cataracts.

Methods: We collected data from 25 consecutive post-RK cataract patients who had undergone uneventful phaco-emulsification surgery with foldable IOL implantation at our centre. Only those patients whose IOL power calculation was based on either pentacam or VKG were included. Pre-operative keratometric values(K1 and K2) and 6 weeks post-operative residual spherical equivalent were noted. Success of IOL power calculation was defined by residual spherical equivalent of less than ±2.0 Dioptres.

Results: 11 eyes of 11 patients with pentacam based IOL power calculation and 14 eyes of 14 patients with VKG based IOL power calculation were analysed. Success rate for the pentacam group was 100% while that for the VKG group was 21.42%. The mean residual spherical equivalent for the pentacam group was -1.09D while that for the VKG group was +3.53D. Mean K1 and K2 values recorded for the pentacam group were 26.31D and 30.4D respectively while those recorded for the VKG group were 32.78D and 40.64D.

Conclusions: After RK, cornea becomes flatter which cannot be accurately picked up by VKG resulting in undesirable hyperopic shift. Pentacam is a better keratometric basis for post-RK IOL power calculation.