Intraocular Fluid-Air Exchange Reduces Retinal Ganglion Cell Activity

Abstract

Aim: To demonstrate the influence of intraocular fluid-air exchange on retinal ganglion cell activity. Methods: In two cats lensectomy and vitrectomy were performed in a two-step approach 2 weeks prior to recording experiments. To measure retinal activity, up to two fiber microelectrodes were inserted via a scleral port. Precise micromanipulator positioning of the electrodes’ tips onto the inner retinal surface were verified by ophthalmoscopy and simultaneous electrical recording. Neuronal activity of the retina was continuously recorded with or without visual stimulation. We maintained the intraocular pressure constant at 29 mm Hg. Fluid-air exchange and fluid refill were performed with an infusion tube integrated in the manipulator and slowly to avoid direct mechanical/stream-based damage of the retina. Results: We found that fluid-air exchange leads to a rapid reduction of spontaneous as well as visually evoked retinal ganglion cell activity. The activity started to diminish within few minutes, and then it halved approximately every 3 min. Even 1 h after eye fluid refill, the retinal activity recovered only partially. Conclusion: Decrease in retinal activity after fluid-air exchange can be explained by mechanical stress-induced drying of the inner retinal surface and by potential changes of extracellular ion concentration. Since even moderate airstream-based fluid-air exchanges can lead to retinal damage, the surgeon should minimize the quantity of air passing open sclerotomy sites until a better understanding of the retinal effects of this essential technique in modern vitrectomy is available.

Study of Intraocular Pressure After 23-Gauge and 25-Gauge Pars Plana Vitrectomy Randomized to Fluid Versus Air Fill

“…Although generally considered benign, postoperative air fill is not without risks, including the potential complications of cataract formation or secondary glaucoma. [44][45][46][47] Even through beveled incisions, the mean IOP tends to fluctuate based on gauge size and time of measurement, and this study further contributes to our knowledge and experience using small-gauge transconjunctival PPV. We recommend careful examination of sclerotomy sites after trocar removal with a low tolerance for the placement of a suture for closure.…”

“…28,29,31,43 However, fluid-air exchanges are not without risk because several reports have cited damage to the retina or optic nerve resulting in decreased retinal ganglion cell activity, visual field defects, or morphologic changes in the optic disk after fluid-air exchange. [44][45][46][47] The objective of this study was to prospectively evaluate whether a difference in intraocular pressure (IOP) or hypotony rate exists between eyes randomized to fluid fill versus those randomized to air fill after 25-gauge and 23-gauge vitrectomy through beveled incisions. We are unaware of any prospective randomized study evaluating the effect of these parameters in small-gauge transconjunctival PPV.…”

Comparing the Effects of Two Different Irrigation Solutions on an Isolated Perfused Vertebrate Retina

“…Endoillumination [1], continuous flow of an irrigation solution to maintain inner pressure during and after vitrectomy [2], the mechanical manipulation of the retina up to an artificial detachment and the suppression of blood flow reducing the nutrition of neuronal tissue have been shown to have a negative effect on the retina [3,4,5]. The fact alone that surgery on the retina is necessary indicates in most cases that the retina is already damaged in morphology and function.…”

Testing the Biocompatibility of a Glutathione-containing Intraocular Irrigation Solution by Using an Isolated Perfused Bovine Retina Organ Culture Model — an Alternative to Animal Testing

“…In the course of vitreo-retinal surgery, many factors have to be considered that could be harmful to the retina, including: the source of endoillumination (5); the continuous flow of an irrigation solution (6); the mechanical manipulation of the retina; and the suppression of blood flow, which can potentially affect the neuronal tissue. All of these factors have been shown to have negative effects on the retina (7)(8)(9).…”