Effects of cervical sympathetic nerve block on the change of electroretinogram by raising intra-ocular pressure in rabbits
Matsuura, M.; Miyake, Y.
Nippon Ganka Gakkai Zasshi 86(3): 307-314
1982
ISSN/ISBN: 0029-0203 PMID: 7102484 Document Number: 187404
Intraocular blood flow is increased by cervical sympathetic nerve block in animals with no ocular circulatory disturbances. Block of the stellate ganglion, one of the cervical sympathetic ganglions has been applied in the therapy of some ocular diseases including central serous chorioretinopathy, subretinal neovascularization, cystoid macular edema and retinal arterial obstruction. Intraocular circulatory disturbance is suspected to be one of the possible etiologies in these diseases. This clinical application has brought unexpectedly good results. No attempt was previously made to prove that the intraocular blood flow is also increased in eyes with ocular circulatory disturbances by the cervical sympathetic nerve block. The mechanism of the recovery of the visual functions in clinical patients mentioned above should be studied. An ocular circulatory disturbance was produced by raising intraocular pressure of albino rabbits, and the cervical sympathetic nerve was blocked with local anesthetic drug. The ocular circulatory disturbance and its recovery were evaluated by measuring a- and b-waves of the electroretinogram (ERG). When intraocular pressure was raised and perfusion pressure (mean arterial blood pressure minus intraocular pressure) was kept within .apprx. 40 mm Hg under a certain mean arterial blood pressure, amplitudes of a- and b-waves declined raidly and did not recover. After cervical sympathetic nerve block with 1 ml of 2% lidocaine, in which a- and b-waves declined remarkably, both a- and b-waves recovered immediately in all cases. This recovery of ERG following by the block is considered to be due to the increase in intraocular blood flow. With the block, mean arterial blood pressure rose slightly at first and then returned to pre-block level. Even when the blood pressure returned to the pre-block value, amplitudes of a- and b-waves remained recovered. The increase in intraocular blood flow caused by the cervical sympathetic nerve block is considered to have a relationship with increased perfusion pressure at an earlier stage and with reduced vascular resistance at a later stage. Apparently, the block of cervical sympathetic nerve is effective in increasing the intraocular blood flow even in eyes with circulatory disturbances.