Implantation of phakic intraocular lenses in patients with stabilized keratoconus

To date, extensive experience has been accumulated in the correction of high myopia and myopic astigmatism through the implantation of additional negative lenses (phakic intraocular lenses). However, the use of this method in patients with anatomically altered corneas due to keratoconus remains unresolved.

Purpose: to assess the effectiveness and safety of correcting high myopia combined with myopic astigmatism by implanting phakic intraocular lenses in patients with stabilized keratoconus at stages 1–2.

Materials and methods. The study encompassed results from 27 surgeries involving the implantation of phakic intraocular lenses in patients with high myopia and myopic astigmatism (12.63 ± 4.25 D). These patients had thin corneas and were diagnosed with stage 1–2 keratoconus after undergoing corneal collagen crosslinking treatment – this constituted the main group. The control group comprised 35 surgeries performed on patients with subclinical non-progressive keratoconus (Forme Fruste). All participants underwent evaluations for visual acuity dynamics and refractive stability of spherical and cylindrical components before surgery, immediately post-surgery, and then at 1, 6, and 12 months after implantation. Additional assessments included intraocular pressure measurements, gonioscopy, ultrasonic echobiometry, ultrasonic ophthalmoscopy, biomicroscopy, ophthalmoscopy, endothelial microscopy, vision character and stereopsis determination, ultrasound biomicroscopy, anterior segment optical coherence tomography, electrophysiological studies, and statistical analysis. An IPCL (a type of phakic intraocular lenses made from hydrophilic acrylic) was implanted, capable of correcting myopia up to 30 D and astigmatism up to 10 D.

Results. All patients achieved high uncorrected visual acuity 0.86 ± 0.11. Astigmatism correction was successful in 96% of cases. The average postoperative vault – the distance from the back surface of the phakic intraocular lenses to the anterior lens capsule – was 527.5 ± 40.27 μm (range 460–600 μm), and the intraocular pressure was 11.7 ± 2.08 mm Hg. There was a minor decrease in corneal endothelial cell count from 2599 ± 157.3 to 2375 ± 125.3 cells/mm² in the first group and from 2614 ± 104.8 to 2375 ± 43.3 cells/mm² in the second group respectively (p > 0.05), which falls within the acceptable loss range of 4–7% from preoperative values for both groups. Throughout the observation period, there were no cases of cataract development, pigmentary glaucoma, pupillary block, or other vision-threatening complications.

Conclusions. Implantation of phakic intraocular lenses in patients with early-stage stabilized keratoconus and subclinical non-progressive keratoconus provides an effective and practically safe means of correcting high myopia and astigmatism.

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