Abstract
Background:In case of keratoconus, rigid gas-permeable contact lenses as the correction method of first choice allow for a good visual acuity for quite some time. In a severe stage of the disease with major cone-shaped protrusion of the cornea, even specially designed keratoconus contact lenses are no more tolerated. In case of existing contraindications for intrastromal ring segments, corneal transplantation typically has a very good prognosis.Methods:In case of advanced keratoconus – especially after corneal hydrops due to rupture of Descemet’s membrane – penetrating keratoplasty (PKP) still is the surgical method of first choice. Noncontact excimer laser trephination seems to be especially beneficial for eyes with iatrogenic keratectasia after LASIK and those with repeat grafts in case of “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 will be 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.Results: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, thus resulting in significantly less “all-sutures-out” keratometric astigmatism (2.8 vs. 5.7 D), higher regularity of the topography (SRI 0.80 vs. 0.98) and better visual acuity (0.80 vs. 0.63) in contrast to the motor trephine. The stage of the disease does not influence functional outcome after excimer laser PKP. Refractive outcomes of femtosecond laser keratoplasty, however, resemble that of the motor trephine.Conclusions: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 pitfalls and high postoperative astigmatism.
Highlights
In the case of keratoconus, rigid gas-permeable lenses have been the first-line correction method for good vision results
Prospective clinical studies have shown that the technique of non-contact excimer laser penetrating keratoplasties (PKP) improves donor and recipient centration, reduces “vertical tilt” and “horizontal torsion” of the graft in the recipient bed, resulting in significantly less “all-sutures-out” keratometric astigmatism (2.8 vs. 5.7 D), higher regularity of the topography (SRI 0.80 vs. 0.98) and better visual acuity (0.80 vs. 0.63) in contrast to the motor trephine
There was a decrease in astigmatism in 52% of the eyes of the excimer laser group after suture removal, whereas in the control group there was an increase in astigmatism in 76% of the eyes after suture removal
Summary
In the case of keratoconus, rigid gas-permeable lenses have been the first-line correction method for good vision results. If there are contraindications for intrastromal ring segments [2], corneal transplants are indicated at this stage of the disease, and typically have a very good prognosis [3]. In the year 2014, 50.7% of all corneal transplants were of the posterior lamellar type, with only 3.9% being anterior lamellar grafts (DALK) and 45.4% still being carried out as penetrating keratoplasties (PKP) (Fig. 1). Rigid gas-permeable contact lenses as the correction method of first choice allow for a good visual acuity for quite some time. In a severe stage of the disease with major cone-shaped protrusion of the cornea, even specially designed keratoconus contact lenses are no more tolerated. In case of existing contraindications for intrastromal ring segments, corneal transplantation typically has a very good prognosis
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