Visual outcome in corneal grafts: A preliminary analysis of the Swedish Corneal Transplant Register. (Clinical Science).(Statistical Data Included)

Aim: To assess visual outcome and the incidence of complications at 2 years postoperatively in corneal grafts reported to the Swedish Corneal Transplant Register.

Methods: Preoperative and 2 year follow up data were submitted to the Swedish Corneal Transplant Register by surgeons in eight corneal transplant clinics in Sweden. Preoperative data on 1957 grafts and 520 grafts with 2 year follow up were included in the analysis. Data were analysed by multiple linear and logistic regression methods, as appropriate.

Results: The major diagnostic categories were keratoconus (29%), bullous keratopathy (21%), and "other diagnosis" (32%). Fuchs' endothelial dystrophy and stromal dystrophies accounted for 15% and 3% of grafts, respectively. At 2 years the overall incidence of complications, other than rejection and regrafting, was 26%, with an increasing frequency from keratoconus < Fuchs' dystrophy < bullous keratopathy < "other diagnosis." Rejection was observed in 15% of grafts and was more likely in the bullous keratopathy (OR 3.1, 95% CI 1.1 to 9.0, p=0.04) and "other diagnosis" (OR 2.6, 95% CI 1.1 to 5.9, p=0.03) groups. Regrafting, which occurred in 10% of cases, was not influenced by diagnosis, but it was related to the incidence of rejection (OR 14.8, 95% CI 6.1 to 35.9, p<0.001) and other complications (OR 4.4, 95% CI 1.9 to 10.4, p=0.001), and to the presence of other sight threatening pathology in the eye (OR 3.6, 95% CI 1.3 to 9.9, p=0.001) Visual acuity was improved in a high proportion of the patients, especial ly those with keratoconus and Fuchs' dystrophy where, respectively, 86% and 54% of grafts achieved a visual acuity of [greater than or equal to]0.5 at 2 years, compared with only 31% with bullous keratopathy and 35% in the "other diagnosis" group. 60% of grafts for keratoconus and Fuchs' dystrophy achieved a visual acuity equal to or better than the other eye. Postoperative astigmatism was higher in the bullous keratopathy (p=0.0l) group. Patients with high astigmatism benefited from refractive surgery, showing a reduction from 7.9 (95% CI 6.9, 8.7) to 3.2 (95% CI 2.6, 3.9) dioptres (p<0.00 1). A centre effect was evident in visual outcome.

Conclusion: The overall incidence of complications was related to diagnosis. Complications other than rejection and regrafting were most likely in the "other diagnosis" group, and further analysis of this group is therefore planned. The best improvement in visual acuity and the lowest astigmatism were achieved in the keratoconus and Fuchs' dystrophy groups; but the influence of diagnosis on astigmatism was small and, overall, the statistical model accounted for only 8% of the variability in astigmatism. Refractive surgery was, however, effective in reducing astigmatism. It is hoped that a better understanding of the factors that determine the visual outcome of grafts will emerge from future analyses of the Swedish Corneal Transplant Register, helping to refine the criteria for patient selection and to guide clinical practice.

The main purpose of the majority of corneal grafts is to improve vision, but other benefits for patients include pain relief or even simply saving an eye. With some notable exceptions, (1) many analyses of the outcome of corneal grafting have focused primarily on graft survival and immunological rejection, which still remains the most common cause of early graft failure and the continuing subject of both laboratory and clinical follow up studies. (2) Since many of the factors influencing visual outcome remain uncertain, the Swedish Corneal Transplant Register was started in 1997 to collect data from the 500--600 grafts performed each year in Sweden. The emphasis of the register is on visual outcome with the purpose of providing evidence to support or to change current practice in patient selection and the management of grafts. Sweden is a suitable geographical area for such a register as grafts are performed in only eight clinics and it is usually possible to trace the patients for follow up. Moreover, the gr oup of fewer than 20 corneal graft surgeons is able to meet regularly to discuss the register and results.

In many reports, the end point for follow up is only 1 year. However, healing after corneal transplantation is an extended process and procedures such as suture removal and refractive surgery are most likely to occur after 1 year. We therefore decided to collect data at 2 years when all sutures will have been removed and the eye has a fairly stable refraction.

METHODS

Forms were developed to collect data preoperatively and at 2 years postoperatively. At the time of surgery surgeons provided patient details (age, sex, diagnosis, type of procedure, visual acuity, lens status). The diagnosis was divided into five groups: keratoconus, Fuchs' endothelial dystrophy, bullous keratopathy (corneal oedema resulting from previous ocular surgery), stromal dystrophy, and "other diagnosis." Preoperative visual acuity (visual acuity with best preferred correction) was measured by Snellen charts in both eyes. Type of procedure was defined as penetrating keratoplasty (PKP), triple procedure (penetrating keratoplasty combined with an extracapsular cataract extraction and implantation of an artificial intraocular lens), or other procedure, such as PKP combined with replacement of an intraocular lens, secondary intraocular lens, vitrectomy, iris suture or other reconstructive surgery. All of the …