One-step thermokeratoplasty for pain alleviating and pre-treatment of severe acute corneal hydrops in keratoconus

AIM:To observe the efficacy of simplified one-step thermokeratoplasty for the treatment of severe acute corneal hydrops in keratoconus.METHODS:In this retrospective,noncomparative clinical study,10 patients(10 eyes) with acute hydrops in keratoconus were treated with simplified one-step thermokeratoplasty.Pain,changes in the corneal curvature,thickness,and size and morphology of the Descemet membrane breaks were detected before and after surgery.Eight patients were successfully treated using modified deep anterior lamellar keratoplasty(DALK).Graft transparency,visual acuity,and immunological rejection were evaluated for 6 to 12mo.RESULTS:Pain and corneal oedema were promptly alleviated,and the intrastromal ruptures diminished within 3 to 6wk after thermokeratoplasty.At 3 to 6wk after corneal oedema was faded,Descemet membrane breaks and intrastromal ruptures were healed.Two patients did not undergo subsequent corneal transplantation after thermokeratoplasty.Eight patients underwent DALK successfully and safely after thermokeratoplasty,without corneal perforation.Central corneal opacity faded or disappeared within 6mo.The mean best-corrected visual acuity was increased to 20/30 at 12mo after DALK.No one was observed with any immune rejection.CONCLUSION:One-step thermokeratoplasty can successfully and efficiently accelerate the absorption of prominent corneal oedema in severe acute hydrops patients.This simple procedure with no complications can be performed in the emergency department by residents.This method can improve the safety of DALK and obtain good postoperative vision.Long-term management of acute corneal hydrops using simplified one-step thermokeratoplasty seems promising.

Dynamical Simulation of Cornea Deformation in Laser Surgery

A dynamical simulation method is presented to model the cornea deformation in surgery of laser thermokeratoplasty. The virtual cornea is constructed as a mass-spring system. The corneal surface tension is simulated by damping spring stretch between mass points on the cornea model. The aqueous humor in the eyeball is modeled as ideal gas, and the intraocular pressure is simulated by gas pressure. The coagulation force is exerted on each photocoagulation spot to demonstrate its collapse caused by the condensation of corneal soft tissue irradiated by laser. An extra viscous drag force is added to each mass point to weaken the mass point oscillation. The use of the effective time-corrected Verlet integral method brings about flowing and stable dynamic simulation procedures. The simulation results show that, comparing to the undeformed model, the curvature of the region between the optical center and photocoagulation spot increases obviously. Moreover, the shape of the deformed virtual cornea is much similar to that of the real cornea after surgery.