Effect of Pneumatic Suction Ring Placement on Intraocular Pressure in Cats

Abstract

Purpose: To determine the effect of placing a pneumatic suction ring on intraocular pressure (IOP) in the cat and to design an improved method to generate a stable elevation of IOP. Methods: A pneumatic suction ring was applied to the eye in cats while the IOP was monitored. Three groups of animals (10 per group) were used. A vacuum pressure of 450 mbar was applied in one step to eyes of group 1 (anesthetized) and to group 2 (euthanized) cats. In group 3 (anesthetized) cats, an initial vacuum pressure of 250 mbar was applied, followed by a vacuum of slowly increasing pressure at a rate of 5 mbar/min for a total of 40 min to 450 mbar. Results: After the one-step application of a vacuum (450 mbar) to the eyes of anesthetized cats (group 1), IOP peaked within the first minute from a basal value of 25 ± 2 mm Hg (mean ± SD) to 90 ± 7 mm Hg. It then rapidly decreased to 69 ± 2 mm Hg 5 min later and continued to decrease to 39 ± 4 mm Hg 40 min later. This sharp peak and decline of IOP were also observed in eyes of euthanized cats (group 2). The basal IOP of these eyes was 8 ± 1 mm Hg. It rose to 18 ± 2 mm Hg immediately after the application of vacuum pressure (450 mbar) and returned to the basal level 5 min later. In contrast, the eyes of group 3 receiving an initial vacuum of 250 mbar followed by a 5 mbar/min vacuum increment exhibited a rapid increase in IOP and a very stable plateau (mean IOP = 62–68 mm Hg), lasting the whole study period (40 min). Conclusion: IOP after a one-step application of a vacuum via a pneumatic suction ring is self-adjusting and declines rapidly over time. This decline in IOP can be overcome by a supplementary increment in vacuum pressure.

Pneumatic Trabeculoplasty versus Argon Laser Trabeculoplasty in Primary Open-Angle Glaucoma

“…During LASIK, IOP increases to 85–120 mm Hg during the suction phase [20,21,22,23,24] and deformation of the eye (1.125 mm axial length increase, mainly affecting the posterior segment) [25] and reversible optic nerve head changes have been detected [26]. However, after several months, no alterations were found in the optic disc, retinal nerve fiber layer [27,28,29], and visual field [30,31].…”

Pneumatic trabeculoplasty vs latanoprost as adjunctive therapy to timolol in primary open-angle glaucoma or ocular hypertension

“…During LASIK, IOP increases (to 85-120 mmHg during the suction phase and up to 150 mmHg during the cutting phase) [17][18][19][20][21]; a transient increase of blood flow in the lamina cribrosa region of the optic nerve head was found 1 day after the treatment, suggesting a reactive hyperaemia after ischemia induced by high IOP levels [22].…”

A new method and device to induce transient retinal ischemia in the rat

“…14,15 However, IOP elevation effected by the suction ring is unstable and declines very rapidly (i.e., within minutes), likely due to the adaptive functions of the aqueous hydrodynamics. 14,15 Another ischemia method 17 involves the placement of two suture loops on the bulbar conjunctiva around the limbus of the eye. The sutures are then pulled in opposite directions until the retinal blood flow is interrupted completely.…”