For patients with
keratoconus, rigid gas-permeable
contact lenses are the first line correction method and allow good visual acuity for quite some time. In severe stages of the disease with major cone-shaped protrusion of the cornea, even specially designed
keratoconus contact lenses are no longer tolerated. If there are
contraindications for intrastromal ring segments,
corneal transplantation typically has a very good prognosis. In patients with advanced
keratoconus - especially after corneal
hydrops due to
rupture of Descemet's membrane -
penetrating keratoplasty (PKP) is still the first line surgical method. Non-contact
excimer laser trephination seems to be especially beneficial for eyes with iatrogenic keratectasia after
LASIK and for patients with repeat grafts due to "
keratoconus recurrences" due to small grafts with thin host cornea. For donor
trephination from the epithelial side, an artificial chamber is used.
Wound closure is achieved with a double running cross-stitch
suture according to Hoffmann. Graft size is adapted individually, depending on corneal size ("as large as possible - as small as necessary"). Limbal centration is preferred intraoperatively, due to optical displacement of the pupil. During the last 10 years, femtosecond
laser trephination has been introduced from the USA as a potentially advantageous approach. Prospective clinical studies have shown that the technique of non-contact
excimer laser PKP improves donor and recipient centration, reduces "vertical tilt" and "horizontal torsion" of the graft in the recipient bed, and thus results in significantly less "all-
sutures-out" keratometric
astigmatism (2.8 vs. 5.7 D), more regular topography (surface regularity index [SRI] 0.80 vs. 1.0) and better visual acuity (0.80 vs. 0.60), in comparison to the motor trephine. The stage of the disease does not influence functional outcome after
excimer laser PKP. However, the refractive outcome of femtosecond
laser keratoplasty resembles that with motor trephine. In contrast to the undisputed clinical advantages of
excimer laser keratoplasty with orientation teeth/notches in
keratoconus, the major disadvantage of femtosecond
laser application is still the necessity of suction and applanation of the cone during
trephination, with intraoperative disadvantages and high postoperative
astigmatism.