Study Of Transient Intraocular Pressure Elevation During LASIK On The Retinal Structure And Function

ObjectiveTo observe effects of transient intraocular pressure elevation during LASIK on the retinal structure and function.Methods1. Animal model building: New Zealand rabbit received different duration of suction (45 seconds and 3 minutes) to induce intraocular pressure elevation by negative pressure generator (IOP>65mmHg).Corneal epithelium was removed by PTK and received eximer laser (-9.00D, 193nm, 125mJ/cm~2, 10Hz).2. Retinal structure observation: The experimental eyes of 71 anesthetized New Zealand rabbit received different duration of suction (45 seconds and 3 minutes) to induce intraocular pressure elevation (IOP>65mmHg).FFA examinations occurred just before euthanasia and tissue was processed for histopathology and transmission electron microscopy on instant, days 7, 10, 14, 28 and 56.3. Retinal function examination:The experimental eyes of 30 anesthetized New Zealand rabbit received different duration of suction to induce high intraocular pressure (IOP>65 mmHg). F-ERG (250ms, 0.5Hz, 4, 10, 0.1 ~ 75Hz) and F-VEP (250ms,1Hz, 4, 100, 20, 0.1 ~75Hz) examinations occurred just before anesthetized on minutes 10, hours 1, 2 and 12 , days 1, 7,14 and 28.4. RNFL measurement in vivo: The experimental eyes of 15 anesthetized New Zealand rabbit received different duration of suction to induce high intraocular pressure (IOP>65 mmHg). Retinal nerve fiber layer thickness around peripheral optic disc examinations occurred by OCT (4.0mm, 500x500) just before euthanasia on days 7, 10,14, 28 and 56.5. Vitreous amino acids examination: The experimental eyes of 35anesthetized New Zealand rabbit received different duration of negative pressure suction to induce high intraocular pressure (IOP>65 mmHg). Vitreous amino acids (including ASP, GLU, GABA, GLY) examination were occurred by HPLC (4.6mm×150mm, 5μm, 340nm, 450nm) just before euthanasia on instantly, days 7,10,14 and 28. Results1. Retinal structure observation: Angioplerosis and filling defect were not observed on instant, days 7, 10, 14, 28 and 56 post negative suction by FFA. The structure of retina did not changed under light microscopy and electron microscopy after negative suction 45 seconds. But the structure of optic nerve changed lightly under electron microscopy on instant. And they can recoveryed after 7 days. But those were visible disorder on instant,days 7 and 10 after suction 3 minutes. Also they can recoveryed after 28 days.2. Retinal function examination: Amplitude of ERG b-wave increased from minutes 10 to 30 after negative suction 45 seconds (P<0.05). Amplitude of b-wave decreased from minutes 10 to 60 post negative suction 3 minutes (P<0.01). It can recovery to the level before suction with the recovery periods prolonging. Amplitude and incubation period of ERG b-wave and VEP PI-wave did not significantly change after different duration of suction (P>0.05) .3. RNFL measurement in vivo:The most thickness of RNFL is (155±7.38)μm in the control group. The thickness of RNFL was significantly thinner on day 10 after suction 45 seconds than it of the control group (P<0.05). The most thinner of thickness was (127.6±20.01)μm. The thickness of RNFL increased gradually afterward, but it cannot recovery to control level untill 28 days(P<0.05). The thickness of RNFL went back to control level till 56 days(P>0.05). There was significantly thinner in the results of RNFL on days 10 ~ 56 post suction 3 minutes than it of the control group and suction 45 seconds group (P<0.01).There was significantly positive correlativity between RNFL thickness and repair periods after suction 45 seconds or 3 minutes (P<0.05). Also there was significantly negative correlativity between RNFL thickness difference values and repair periods after suction 45 seconds or 3 minutes (P<0.05). Although the thickness of RNFL increased gradually with the prolong of repair time, it was still...