[Precision of lamellar refractive corneal lenticules]

We studied the changes in central lenticular thickness in 40 porcine corneal specimens subjected to refractive modification on the "Hamburg Refractive Bench." The changes in thickness attempted were +0.1 mm (group 1), +0.2 mm (group 2), -0.15 mm (group 3), and -0.25 mm (group 4). The lenticular thickness was determined by ultrasound in nine positions. When the intended changes in central corneal thickness were compared with the actual changes, the findings were +0.1047 in group 1, +0.169 in group 2, -0.1047 in group 3, and -0.2185 in group 4. We conclude that minor modifications in lenticular thickness can be achieved with high precision, but for large corrections in the hyperopic direction, only 85% of the desired changes can be accomplished.