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Threshold to Predict Astigmatism Reduction after Pterygium Excision

Pujol, Pere*; Julio, Gemma; de Carvalho, Amelia M.; Kostov, Belchin§; Martí-Huguet, Tomàs

Optometry and Vision Science: July 2014 - Volume 91 - Issue 7 - p 747–751
doi: 10.1097/OPX.0000000000000307
Original Articles

Purpose To compare corneal astigmatism after pterygium excision, using limbal-conjunctival autograft (LCA) with and without mitomycin C (MMC) and to establish a threshold for postoperative astigmatism reduction.

Methods Sixty-eight eyes with primary pterygium were consecutively sampled and assigned to LCA with MMC (MMC+) or LCA without MMC (MMC−). Corneal lesion length, corneal lesion area, preoperative corneal astigmatism (PRCA), and postoperative corneal astigmatism (POCA) at 1, 3, and 6 months were assessed.

Results Thirty-six men and 24 women (60 eyes), aged between 24 and 65 years (mean ± SD, 41 ± 8.2 years), completed the study. Thirty-one eyes were included in the MMC+ group and 29 were in the MMC− group. Both groups showed astigmatism reduction (p < 0.05; paired, two-tailed t test) 1 month after the surgery and remained stable. No differences were found between groups in corneal lesion length, corneal lesion area, or astigmatism results at the four time points (p > 0.05, independent t test). Preoperative corneal astigmatism showed a significant correlation with POCA at 6 months (r = 0.529; p < 0.01). According to receiver operating characteristic curve analysis, the better threshold for astigmatism reduction with the surgery was 1.05 diopters of PRCA, with 82.5% sensitivity and 80.5% specificity.

Conclusions Both surgical procedures could have similar astigmatism results. Pterygium patients with more than 1.05 diopters of PRCA could reduce it after the surgery. Direct relationship between PRCA and POCA revealed that postoperative astigmatism reduction was partial. Therefore, for minimizing final astigmatism, preoperative values should be slightly above the threshold.





Department of Ophthalmology, Terrassa Hospital, Terrassa Health Consortium, Terrassa, Spain (PP, GJ, AMdC); Ocular Surface Research Group, Optics and Optometry Department, Universitat Politècnica de Catalunya, Terrassa, Spain (PP, GJ, TM-H); Transverse Group for Research in Primary Care, IDIBAPS, Barcelona, Spain (BK); Department of Statistics and Operational Research, Universitat Politècnica de Catalunya, Barcelona, Spain (BK); and Department of Ophthalmology, Bellvitge University Hospital, Barcelona, Spain (TM-H).

Gemma Julio Optics and Optometry Department Violinista Vellsolà 37 08222 Terrassa Spain e-mail:

© 2014 American Academy of Optometry