Correlation between corneal button size and intraocular pressure during femtosecond laser-assisted keratoplasty

Purpose: To evaluate changes in intraocular pressure (IOP) in recipient and donor eyes during femtosecond laser-assisted keratoplasty (FLAK) and to assess for differences in the diameter of trephinated corneal buttons according to changes in pressure. Materials and Methods: Twenty porcine whole eyes (recipient model) and 20 porcine-comeoscleral rims (donor model) were prepared, and anterior chamber pressures were measured using a fiberoptic sensing device (Opsens, Quebec, Canada) during the femtosecond laser corneal cutting process. To detennine the diameter of corneal buttons, 10 porcine whole eyes (recipient model) and 12 corneoscleral rims (donor model) of each baseline IOP were cut with the femtosecond laser programmed to the following pattern: "vertical side cut"; 1200 urn (depth), 8 mm (diameter). Digital photographs were obtained using microscopy and subsequently analyzed. Results: The IOP (mean ± SD) for tie recipient model was 10.2 (±0.9) mm Hg at baseline and ranged from 96.6 (±4.5) to 138.4 (±3.8) mm Hg during die corneal cutting process. This shows that the maximum IOP during FLAK increased 13.5 times compared with baseline. In the donor model, the mean pressure elevation from baseline artificial anterior chamber (AAC) pressure to corneal cutting was 15.8 (±5.4) mm Hg. This showed a positive correlation with baseline IOP [correlation coefficient (CC) = 0.827, P = 0.006], As the baseline IOP in the recipient eye increased, trephinated corneal button size was reduced by up to 3.9% in diameter (CC = -0.945, P = 0.015). In addition, in donor eyes, the diameter was decreased by up to 11.7% as the baseline AAC pressure increased (CC = -0.934, P = 0.006). Conclusions: During the FLAK procedure, die IOP increases in both recipient and donor e>es. The diameter of the trephinated donor and recipient corneal buttons was decreased as the initial baseline IOP increased. Ophthalmic surgeons ean detennine die AAC pressure based on the baseline IOP in the recipient patient.