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Phakic IOL helps treat myopia, astigmatism in eyes with previous PK
J Cataract Refract Surg. 2009;35(7):1166-1173.
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Posterior chamber phakic IOL implantation treated myopia and astigmatism in patients who underwent previous penetrating keratoplasty, a study showed.
"To our knowledge, there are no studies of the implantation of this type of [phakic] IOL after [PK]," the study authors said. "The aim of the present study was to determine whether this surgery is a good alternative for correcting refractive errors after [PK]."
The prospective study included 15 eyes of 15 patients with a mean age of 37.8 years who underwent previous PK and were unable to wear spectacles or contact lenses or to undergo corneal refractive surgery. All eyes received a myopic or toric posterior chamber Visian implantable Collamer lens (ICL, STAAR Surgical).
The mean interval between PK surgery and ICL implantation was 3.35 years.
Investigators assessed uncorrected distance visual acuity, corrected distance visual acuity, refractive error and endothelial cell count before ICL implantation and 24 months after ICL implantation.
At 24 months postop, mean Snellen uncorrected distance visual acuity was 0.51; uncorrected distance visual acuity was 20/40 or better in seven eyes. Mean corrected distance visual acuity showed a statistically significant improvement, from 0.50 to 0.79 (P = .0011). Corrected distance visual acuity was 20/40 or better in 12 eyes and 20/25 or better in six eyes. Spherical equivalent was within 1 D of targeted refraction in 80% of eyes and within 0.50 D in 66.6% of eyes.
No eye lost one or more lines of visual acuity. Seven eyes gained one or more lines.
"Long-term results with a larger sample of patients are needed to assess the predictability of the technique," the authors said. "Future studies should include hyperopic [phakic] IOLs."
This study provides strong evidence that we can use a phakic IOL to reduce anisometropia following keratoplasty. Even though their study evaluated phakic eyes with penetrating keratoplasty, likely their technique would be equally useful in patients who have had deep anterior lamellar keratoplasty for keratoconus, an increasingly popular procedure. These patients also often end up with anisometropia or residual astigmatism. Phakic IOLs have also been used in pseudophakic eyes where the typical piggyback lens isn’t available in the needed power, and this may also be useful in some pseudophakic patients with anisometropia after keratoplasty. Their study evaluates patients up to age 57, and in that age range keratoplasty patients are likely enough to have visually significant cataract develop in the near future because of anti-rejection medication use that I would prefer a lens replacement technique.
– David R. Hardten, MD
OSN
Cornea/External Disease Board Member