PURPOSE: To evaluate the changes in central corneal thickness (CCT) and corneal volume (CV) in eyes that have undergone myopic photorefractive keratectomy (PRK). METHODS: CCT and CV obtained with an Oculus Pentacam before 1, 3, and 6 months after PRK were analyzed in 84 eyes with a mean preoperative refraction of -4.93 +/- 2.23 diopter. The changes were compared with the amount of refractive treatment. The differences were evaluated with the Student t test and the correlations with the Pearson index. RESULTS: One month after PRK, CCT and CV mean differences were 73.2 +/- 31.5 mum (P < 0.001) and 2.2 +/- 1.7 mm (P < 0.001), respectively. Three months after PRK, CCT and CV mean differences were 66.6 +/- 26.7 mum (P < 0.001) and 1.4 +/- 1.3 mm (P < 0.001), respectively. Six months after PRK, CCT and CV mean differences were 65.3 +/- 25.7 mum (P < 0.001) and 1.4 +/- 1.3 mm (P < 0.001), respectively. The effective treatment at each follow-up point was correlated with CCT changes (R = 0.62, 0.71, and 0.73, respectively), but not with CV changes (R = 0.04, 0.04, and 0.01, respectively). CONCLUSIONS: Our findings support the hypothesis that after myopic PRK, when a series of corneal lamellae are severed centrally, the remaining peripheral segments relax. The squeezing force on the matrix is reduced, and the distance between the lamellae expands.
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