An experimental study of the oculorespiratory reflex (ORR) was conducted on 20 albino rabbits using a square wave (SW) type of stimulus. The ORR could be elicited in 100% of animals. The medial rectus was observed to be most reflexogenic for ORR. The frequency and pattern of ORR was not affected by bilateral vagotomy, intravenous atropine or glycopyrrolate, but could be completely abolished by retrobular block.

SummaryA signifcant reflex fall in mean arterial blood pressure from baseline values was observed during extra-ocular muscle traction in rabbits. This effect could be abolished only by retrobulbar block (afferent pathway block) and not by vagotomy. intravenous atropine or gl.vcopyrronium. suggesting that it is distinct from, and independent oJ the oculocardiac reflex. We suggest that these reflex changes in blood pressure be known as the 'oculodepressor refex'. Key wordsAnaesthesia; ophthalmic. Autonomic reflexes; oculocardiac, oculorespiratory .Reflex changes in heart rate and/or cardiac rhythm during extra-ocular muscle traction are well documented in the literature and constitute the 'oculocardiac reflex' (OCR) [I]. Similarly, reflex changes in respiratory rate and/ or rhythm have been designated the 'oculorespiratory reflex' (ORR) [2].* Reflex changes in arterial blood pressure have not been extensively studied to date and this aspect forms the basis of the present experimental work. The relationship between alterations in blood pressure and the oculocardiac reflex has also been studied. MethodsThe experiments were carried out on 20 albino rabbits of either sex of 1-2 kg body weight. After fasting overnight the rabbits were anaesthetised with intravenous pentobarbitone (40 mg.kg-I). Tracheostomy was performed and the vagi were exposed in the cervical region. A femoral vein was cannulated for intermittent injections and the infusion of anaesthetic drugs. The femoral artery on the same side was also cannulated and connected to a pressure transducer which in turn was connected to one channel of a four channel recorder (Polyrite, INCO). Respiratory values were recorded from the tracheal cannula by a separate trans-*The clinical manifestations of the ORR include bradypnoea, gasping, inspiratory pause, shallow breathing and respiratory arrest. ducer on the second channel. The electrocardiogram (ECG) was recorded by needle electrodes.The rectus muscles, medial (MR), lateral (LR), superior (SR) and inferior (IR), were exposed by a gently performed perilimbal peritomy and a silk suture loop was passed under each muscle. A silk suture with wire hooks on both ends was passed over a pulley fixed on a stand. One hook was engaged in the silk suture loop under the muscle tendon and the other was used to attach weights for the mechanical stimulus.In each rabbit, after taking basal recordings of arterial blood pressure and ECG, traction with 150 g was applied by square wave (SW) stimulus (acute traction sustained for a minimal period of 20 s followed by acute release) to the medial rectus, and changes in arterial blood pressure, heart rate and rhythm were recorded. The procedure was repeated for the lateral, superior and inferior recti after a pause of 3 min in each case.For further study the 20 rabbits were divided into four equal groups. In group 1, after taking the basal recordings, bilateral vagotomy was performed in the cervical region and its effects on blood pressure and OCR were elicited by the square wave stimulus t...

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Objective: To study autonomic imbalance if any in normal tension glaucoma (NTG)patients by heart rate variability (HRV)and head-up tilt (HUT)test. Methods:The study subjects of age between 45 and 65 years of either sex comprised 20 patients with NTG (Group ІІ)and 20 age-and sex-matched healthy controls (Group І). Different variables of time and frequency domain of HRV were analyzed at rest, during HUT and the recovery period.Results: Highly significant decrease in value of root mean square successive difference observed in Group ІІ (p<0.000)in comparison to controls. The high-frequency variables (HF [nu]and HF [ms 2 ])were significantly less (p<0.000)and low frequency (LF)/HF ratio was significantly high (p<0.000) in Group ІІ. Conclusion:During stress test, i.e., HUT there was the greater withdrawal of parasympathetic input to heart; hence, there was relatively over sympathetic activity due to sympatho-vagal imbalance.

Objective: Flammer syndrome or Vascular dysregulation has nowadays become an important topic of debate since it is said to pose a risk in development of glaucomatous optic neuropathy, besides raised intraocular pressure. Our study was implemented to determine the role of flammer syndrome, far less known and often neglected in pathogenesis of glaucomatous optic neuropathy. Methods: The study group consisted of forty age and sex-matched diagnosed normal-tension glaucoma subjects and forty healthy controls. Each of them completed the Flammer syndrome questionnaire. T test was used for data analysis. Results: Statistically significant differences in symptoms like increased sensitivity (cold, drugs, smell, pain), long sleep onset time and a reduced feeling of thirst were existed between cases and control groups (p<0.001). They also demonstrated increased sensation to a few signs and symptoms like cold hands/feet, dizziness, migraines, headaches, and pain compared to controls but not significantly. Conclusion: The study could explain the possible relationship between normal-tension glaucoma and Flammer syndrome. Further research to be done to confirm this link in order to prevent the onset of glaucomatous optic neuropathy.