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Keiichiro Minami, Ayami Masuda, Yosai Mori, Ryohei Nejima, Kazunori Miyata; Change of corneal irregular astigmatism after pterygium excision surgery. Invest. Ophthalmol. Vis. Sci. 2013;54(15):535.
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Advanced pterygium degrades the visual acuity due to an irregular astigmatism on the cornea. Surgical excision of the pterygium healed or reduced the irregular astigmatism while the corneal disorder may persist after the surgery. There were assessment of the postoperative disorder irregularity, but the number of subjects was not enough. This retrospective survey was to investigate change of irregular astigmatism after the pterygium excision.
Eyes that had undergone excision surgeries of pterygium on the nasal side at Miyata Eye Hospital from August 1999 to December 2008 were reviewed. Size of the pterygium was graded by the position of the end of pterygium: G1 was until one-third of corneal diameter, and G2-4 corresponded to until, within, and over the pupil, respectively. After excision of the pterygium and intraoperative mitomycin C, the bare sclera was covered by sliding adjacent superior conjunctiva. Corneal topography was measured at pre-op and 1, 3, 6, and 12 months after the surgery. Changes of the topographic index SRI were examined postoperatively for each grade by the paired-ANOVA with Bonferroni multiple comparison. Difference between the grades was also assessed by one-way ANOVA. Effect of an advanced ratio that was ratio of length of pterygium to the corneal diameter, on the SRI at 1 month was also evaluated.
562 eyes were included, consisting of 119, 338, and105 eyes of G1, G2, and G3, respectively. The mean age at the surgeries was 66.4 years (SD: 8.9). Mean SRI in G1 was 0.75 at 1month and decreased to the level before the surgery in 3 months. The SRI of G2 was 0.85 at 1 month and significantly decreased (P<0.001) up to 3 months (0.70). There was no significant difference between G1 and G2. In the SRI in G3, there was a significant decrease from 1.02 at 1 month to 0.91and 0.72 at 3 and 12 months, and G3 was also higher than both G1 and G2 until 6 months. The advance ratio was significantly and weekly correlated with the SRI (P<0.001).
The irregular astigmatism after the excision surgery and the restoration period were associated with the size of pterygium. Since topographic index SRI is associates with visual acuity, it was demonstrated that cases in G3 would require 6 months to restore the normal visual acuity.
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