Visual acuity and astigmatism after eccentric penetrating keratoplasty - a retrospective study on 117 patients

Abstract

The purpose of this study was to asses the functional results of eccentric homologous penetrating keratoplasty in respect of diagnosis as well as position and size of the corneal graft. In this retrospective study, visual acuity and astigmatism of 117 cases of a round eccentric homologous penetrating keratoplasty in 91 eyes of 91 patients were analysed. The PK became necessary because of a corneal ulcer (104), 6 eyes with corneal scars and 7 eyes with ectatic corneal diseases. Using 84 postoperative slides the following parameters were quantified: graft diameter and transparency, distance of the geometric centre of the cornea from the central trephination margin (distance) as well as from the geometric centre of the graft (decentration). Seventeen grafts were classified as eccentric peripheral keratoplasty (mean diameter 5.0 +/- 1.7 mm) with the optical axis through the host cornea and 67 as eccentric central keratoplasty (7.0 +/- 1.3 mm) with the optical axis through the graft. The average follow-up period was 25 months. The astigmatism after 3/12/24 months was 6.7/6.3/5.5 D, but was irregular and not measurable in 74 %/52 %/49 %. The astigmatism increased with increasing decentration (24 months, p = 0.04). After 3/12/24 months, the VA in ulcers was 0.1/0.16/0.16, in scars 0.2/0.6/0.5 and in ectatic diseases 0.3/0.5/0.6. The position of graft and the visual acuity did not correlate significantly. After 24 months, larger the graft size was associated with better visual acuity. With increasing decentration the visual acuity decreased (p = 0.02) and was significantly lower (0.15) in the case of - 2.0 < distance < 2.0 mm than in the case of distance > 2.0 mm (0.4; p = 0.01). The diagnosis resulting in eccentric penetrating keratoplasty seems to have a major impact on the long-term functional prognosis of visual acuity. In addition, visual acuity is limited by high and often irregular astigmatism. Our results indicate that an increasing decentration of the graft is not invariably associated with decreasing visual acuity, provided the graft-host junction is not located in direct proximity of the optical axis.