Visual quality after posterior chamber phakic intraocular lens implantation in keratoconus

Purpose: 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.

Setting: Narayana Nethralaya Postgraduate Institute of Ophthalmology, Bangalore, India.

Design: Case series.

Methods: 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.

Results: 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).

Conclusion: 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.