Femtosecond penetrating keratoplasty in keratoconus

    Purpose. To evaluate clinical functional results of femtosecond (Fs) penetrating keratoplasty (PK) with a combined profile in keratoconus.

    Material and methods. The results of Fs-laser PK with a combined profile were analyzed among 30 patients (eyes) with keratoconus of Amsler’s III-IV level performed in 2008 and that formed the main group. The retrospective analysis of a traditional PK with metal trepans was made in 28 patients (30 eyes) with the same diagnosis. Patients’ age was from 14 to 45 years, follow-up was from 6 months to 3 years. To form corneal disks a IntraLase Fs laser was used (with PRF 60 kHz, pulse energy 2.1-2.3 micro J, pulses interval 2-5 µm, levels interval 2-5 µm) and in traditional PK metal plunger trepans were used.

    Results. One year after the traditional PK the average uncorrected visual acuity (UCVA) was 0.1±0.14 (0.1-0.2), after Fs-PK it was 0.5±0.15 (0.4-0.8). Best corrected visual acuity (BCVA) was 0.6±0.12 (0.5-0.8) after traditional PK, and 0.8±0.11 (0.6-1.0) after Fs-PK. Cylindrical refraction component varied from -0.75 to -6.0D (mean 3.25±1.0D) and did not change significantly after the removal of sutures (8-12 months) and during the whole follow-up. In traditional PK the cylindrical component varied from 1.5 to 10.0D (mean 4.5±1.25D) with a maximum value immediately after surgery and decreased after the suture removal (12 months postoperatively).

    Optical coherence tomography of anterior segment after Fs-PK showed a formation of corneal profiles equal to preset parameters and optimal approximation of operative wound edges.

    Viscoelastic properties of cornea significantly improved after both types of operations (corneal hysteresis was 9.3±0.6mmHg after traditional PK, and 10.5±0.4mmHg after Fs-PK; corneal resistance factor was 9.1±0.4mmHg and 9.9±0.5mmHg respectively). The average endothelial cell density index was 2196±205 cells/мм² one year after Fs-PK and 1960±257 cells/мм2 after traditional PK.

    Conclusions. The use of femtosecond laser to form a combined corneal profile in keratoconus improves the PK efficiency because a more accurate conjunction of donor and recipient tissues, a good sealing, a high biomechanical stability of surgical wound are achieved, that promotes a reduction of postoperative astigmatism, a higher visual acuity, as well as a rapider visual rehabilitation.

    Key words: femtosecond penetrating keratoplasty, combined corneal profile, keratoconus.