Purpose  The purpose of this study was to investigate the effects of transisent high perfusion pressure during phacoemulsification on the retinal circulation and retinal ganglion cells.
Methods  The animals were divided into four groups (n=5 in each group). In group A and C,the perfusion pressure was increased to 60 mmHg and 100 mmHg for 3 min separately. In group B and D, perfusion pressure was maintained to 60 mmHg and 100 mmHg for 5 min respectively. Retinal vascular diameters were evaluated during the infusion, immediately after infusion, 5 min, 10min and 30min after infusion based on the fundus photographs. Optical Coherence Tomography was used to study the changes of rabbits’ retinal nerve fiber layer(RNFL). The eyes were removed after 24 hours. Damage to retinal ganglion cells (RGCs) was analyzed by histological. At the same time terminal deoxyribonucleotidyl  transferase-mediated dUTP-digoxigenin nick-end labeling (TUNEL) assay was used to detect retinal apoptosis in rabbit eyes.
Results  Retina beomes whiten and papilla optica pale during perfusion. Measurements showed signi?cant decrease in retinal artery and vein diameter during perfusion in all of the four groups at the 10 pixel away from the edge of the optic disc. The changes are significant in the two 100mmHg goups compared with 60mmHg-3min group (p=0.025, 0.000). The diameters recovered completely after 30min of reperfusion. The results of factorial analysis showed that perfusion pressure impact more than perfusion time (p1=0.007,p2=0.752). There were significantly fewer cells in the GCL in the 100mmHg-5min group (34/mm) compared with than in the control eyes(37.8/mm). The thickness of RNFL was increased after 3 days in the 100mmHg-5min group, while these changes were not signi?cant (p＞0.05). Any TUNEL positive cells were found in the four groups.
Conclusions  Transient fluctuations during uneventful phacoemulsification leads to structural changes of retinal vessels, which affect the retinal blood circulation and damage RGCs. Furthermore, perfusion pressure impact more than perfusion time.