Objective: This study aimed to examine ocular rupture force in pig eyes after 'minimally invasive radial keratotomy' (MRK) and standard radial keratotomy (SRK). Design: Experimental study. Materials: A total of 71 pairs of pig eyes (51 control eyes) were examined. Intervention: An axial-torsional Materials Testing System (MTS, Eden Prairie, MN) was used to apply blunt force to the corneal surface. A force transducer measured the rupture forces in control eyes and in eyes with MRK or SRK. Five groups of paired eyes were compared: 2.0-mm MRK versus control (N = 12), 3.5-mm MRK versus control (N = 21), 6.5-mm SRK versus control (N = 18), SRK versus 3.5-mm MRK (N = 10), and 3.5-mm MRK versus 2.0-mm MRK (N = 10). Main Outcome Measure: Ocular rupture force (newtons) was measured. Results: The mean rupture force in newtons was 746.3 for control eyes, 514.2 for 2.0-mm MRK, 353.1 for 3.5-mm MRK, and 246.2 for SRK. Analysis of variance showed a statistically significant difference (P ≤ 0.04) between paired comparisons. Conclusion: The MRK and SRK significantly weakened ocular integrity compared with control eyes not operated on. MRK required significantly more force to rupture than SRK. MRK eyes, however, ruptured at 50% to 70% of the force required to rupture eyes not operated on. Any patient considering radial keratotomy should be counseled about the risk of greater ocular damage in trauma.
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