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M. Claesson, W.J. Armitage; Astigmatism and the effect of relaxing incision after penetrating keratoplasty: data from the Swedish Cornea Transplant Register. . Invest. Ophthalmol. Vis. Sci. 2004;45(13):2912.
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Purpose:Astigmatism is a major problem after penetrating keratoplasty. The aims of this investigation were to determine whether there is a relation between preoperative diagnosis and postoperative astigmatism, and to investigate the benefit of relaxing incisions. Methods:Approximately 90% of the corneal transplants performed in Sweden since 1996 have been reported to the Swedish Cornea Transplant Register. Preoperative and 2–year postoperative data were collected. Astigmatism was measured in 844 patients after suture removal. In 81 of the patients relaxing incisions were used to decrease the postoperative astigmatism. The data were analysed by multiple regression methods. Results:The overall mean astigmatism was 4.6 D (95% CI 4.4 to 4.8) with 33% of the grafts having <3 D of astigmatism. Multiple regression analysis after square root transformation of astigmatism showed no differences between different diagnostic groups although there was a slight increase in astigmatism with increasing recipient age (p=0.001). There was evidence of a centre effect, with 2 of the 7 clinics included in the analysis achieving lower levels of astigmatism (p=0.001). Relaxing incisions resulted in a significant reduction in postoperative astigmatism from 8.5 (95% CI 7.9 to 9.1) to 4.2 (95% CI 3.2 to 5.3) dioptres (p=0.001). Conclusions:The lack of influence of recipient factors, including diagnosis, agrees with the contention that the postoperative astigmatism is related to the surgical procedure itself. This is further supported by the presence of a centre effect. Relaxing incisions halved the astigmatism.
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