Visual quality after posterior chamber phakic intraocular lens implantation in keratoconus

To quantify image-quality characteristics after correction of refractive error with a posterior chamber phakic intraocular lens (PC pIOL) in eyes with stable or stabilized keratoconus.

Narayana Nethralaya Postgraduate Institute of Ophthalmology, Bangalore, India.

Case series.

Eyes with stable or stabilized keratoconus that had V4 Visian PC pIOL implantation for correction of refractive error were evaluated postoperatively for visual-quality metrics.

Ten eyes of 7 patients had PC pIOL implantation. The preoperative mean refractive spherical equivalent of -7.21 diopters (D) ± 2.25 (SD) decreased to -0.55 ± 1.53 D at 6 weeks and -0.44 ± 1.21 D at 6 months. The efficacy index was 0.72 and the safety index, 1.13. The mean modulation transfer function (MTF) was 18.96 ± 14.16 (≥ 30 cycles per degree = good), the Strehl ratio was 0.11 ± 0.07 (1 = perfect), and the objective scatter index (OSI) was 4.45 ± 3.29 (≥ 1.5 = significant scatter). The MTF correlated inversely with secondary coma (P=.026), negative vertical coma (P=.014), and the root mean square (RMS) of total aberrations (P=.010) and higher-order aberrations (HOAs) (P=.015). The OSI was directly correlated with secondary coma (P=.021), secondary trefoil (P=.016), the RMS of total aberrations (P=.032), and HOAs (P=.050).

In keratoconus, the refractive error could be corrected with the PC pIOL; however, the associated aberrations had an adverse impact on the ultimate visual quality and have to be addressed.