Real time intraocular pressure and lamellar corneal flap thickness in keratomileusis

Background. To measure real time intraocular pressure (IOP) during keratomi leusis and to determine variability of corneal flap thickness by using diff erent suction ring pressure settings. Methods, Eight human cadaver eyes, tw o groups of four each, were used. The suction ring of the UniversalKeratome was applied to each eye, the same as for a standard automated lamellar ker atoplasty (ALK) or laser in situ keratomileusis (LASIK) procedure, to creat e a lamellar corneal flap. The pressure of the suction ring on each eye was raised to one of two different levels, four eyes to 488 and the remaining four to 600 mmHg. IOP was continuously recorded by manometer, from applicat ion of the suction ring through the end of the passage of the microkeratome . Central corneal thickness was measured, both before and after each proced ure. Results. IOP increased by >90 mmHg after application of the suction ri ng at a pressure of either 488 mmHg or 600 mmHg. Corneal flaps performed un der a suction ring pressure of 488 mmHg measured 159.98 +/- 5 mum, whereas flap thickness for the 600-mmHg group varied 1.4-266.2 mum. Two flaps exhib ited irregular configurations. Conclusions. Real time IOP can be measured d uring keratomileusis. The results demonstrated a significant increase in IO P during the procedure. Suction ring pressure setting is an important varia ble in determining consistent corneal flap thickness during the keratomileu sis procedure.