Mini radial keratotomy reduces ocular integrity. Axial compression in a postmortem porcine eye model.

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 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 < or = 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.