The Slower the Better: On the Instability of Gas Jets in a Model of Pneumatic Retinopexy

PURPOSE. To investigate the effect of injection technique parameters on the formation of multiple gas bubbles in a porcine eye model for pneumatic retinopexy. METHODS. Three hundred twenty-four adult porcine eyes were injected with 0.4 mL of C3F8 with variations in the depth of injection, speed of injection, and size of needle bore. The number of gas bubbles in the eye was assessed with indirect ophthalmoscopy. RESULTS. Shallow injections resulted in a higher incidence of a single bubble than did deep injections (P Ͻ 0.001; Fisher exact and Wilcoxon rank sum tests). Slow injections were significantly advantageous in producing a single gas bubble during shallow as well as during deep injections (P Ͻ 0.001, Fisher exact and Wilcoxon rank sum tests). With a shallow needle insertion, the slow speed of injection produced a single bubble in 75.9% of the eyes, whereas moderately brisk injections resulted in one bubble in 50.9% of the eyes. During deep needle insertion, 44.4% of the eyes had one bubble if the gas was injected slowly and only 11.1% had a single bubble with moderately brisk gas injections. The bore of the needle did not significantly change the number of bubbles during deep or shallow injections. CONCLUSIONS. The factors that were found to be important in reducing the formation of multiple gas bubbles in the eye were shallow depth of injection and slow speed of gas delivery. (Invest Ophthalmol Vis Sci. 2007;48:2734 -2737) DOI:10.1167/ iovs.06-1384 P neumatic retinopexy (PR) has been established as a treatment modality for rhegmatogenous retinal detachment (RD). This outpatient procedure consists of transconjunctival cryopexy with intravitreal gas injection, followed by head positioning. Alternatively, laser photocoagulation can be applied around the tear instead of cryopexy when the retina is attached 1 or 2 days after the initial gas injection. One potential complication of PR may occur if small bubbles ("fish eggs") are formed in the vitreous cavity during gas injection. This occurrence may facilitate migration of one of the bubbles into the subretinal space. 1,2 Subretinal gas in the vicinity of the tear will prevent sufficient chorioretinal scarring, leading to the persistence of the RD. 3 In addition, the subretinal gas bubble can shift and detach more areas of the retina, including the macula. 5-7 We designed an experiment to test the effect of injection technique parameters on the formation of multiple gas bubbles in a porcine eye model. The effect of the depth of injection, speed of injection, and the needle bore on the formation of gas bubbles was studied. METHODS Three hundred fifty adult porcine eyes were purchased (Clougherty Packing Co., Los Angeles, CA). Of the 350 eyes, 26 were not used because of either corneal scars (22 eyes) or ruptured globe (2 eyes). Each study eye was mounted in an artificial head, and secured with pins to prevent movement. A volume of 0.4 mL perfluoropropane (C3F8) gas (Alcon Surgical, Fort Worth, TX) was placed in a 1.0-mL tuberculin syringe, fitted with a 25-, 27-, or a 30-gauge needle (BD Biosciences, Franklin Lakes, NJ). To make the injection site uppermost, the artificial head was placed supine with a 45°tilt. The needle was then passed into the eye perpendicular to the sclera, on the temporal side 3.0 mm posterior to the limbus. Injection of the entire volume of gas was performed, and the needle was withdrawn from the eye with the plunger held down. The depth of the needle during gas injection was approximately 3 mm (one-fourth needle length) for the shallow injections (after initial insertion of 6 to 8 mm to penetrate the anterior hyaloid) and 12 mm for the deep injections (full needle length). The speed of injection had two variations. Fast injections were performed in a moderately brisk fashion. The injection was given smoothly and quickly but not with excessive force. Slow injections, in contrast, were performed in a period of 8 seconds (timing by counting "one-one thousand, two-one thousand. . . ,"). Immediately after the gas injection, an anterior chamber paracentesis was performed with a 30-gauge needle mounted on a 1.0-mL syringe without a plunger, to reduce the pressure associated corneal edema. An indirect ophthalmoscope with a 20-D lens was used to assess the number of gas bubbles in the vitreous cavity. We performed a total of 324 gas injections: 216 shallow injections and 108 deep injections. Of the 216 shallow injections, 108 injections were performed slowly and 108 were delivered in a moderately brisk fashion. At each injection speed, 36 injections were made with each needle size (25-, 27-, and 30-gauge). Of the 108 deep injections, 54 injections were performed slowly and 54 were given briskly. For every injection speed, 18 injections were performed with each needle size (25-, 27-, and 30-gauge). RESULT

Novel heavy dyes for retinal membrane staining during macular surgery: multicentre clinical assessment

Purpose: To evaluate the feasibility of two novel ‘heavy’ dye solutions for staining the internal limiting membrane (ILM) and epiretinal membranes (ERMs), without the need for a prior fluid-air exchange, during macular surgery. Methods: In this prospective nonrandomized multicenter cohort study, the high molecular weight dyes ILM-Blue™ [0.025% brilliant blue G, 4% polyethylene glycol (PEG)] and MembraneBlue-Dual™ (0.15% trypan blue, 0.025% brilliant blue G, 4% PEG) were randomly used in vitrectomy surgeries for macular disease in 127 eyes of 127 patients. Dye enhanced membrane visualization of the ILM and ERMs, ‘ease of membrane peeling’, visually detectable perioperative retinal damage, postoperative best-corrected visual acuity (BCVA), dye remnants and other unexpected clinical events were documented by 21 surgeons. Results: All surgeries were uneventful, and a clear bluish staining, facilitating the identification, delineation and removal of the ILM and ERMs, was reported in all but five cases. None of the surgeries required a fluid-air exchange to assist the dye application. BCVA at 1 month after surgery improved in 83% of the eyes in the MembraneBlue-Dual™ group and in 88% in the ILM-Blue™ group. No dye remnants were detected by ophthalmoscopy, and no retinal adverse effects related to the surgery or use of the dyes were observed. Conclusion: The ‘heavy’ dye solutions ILM-Blue™ and MembraneBlue-Dual™ can be injected into a fluid-filled vitreous cavity and may facilitate staining and removal of the ILM and/or ERMs in macular surgery without an additional fluid-air exchange

Testicular function and semen characteristics of Awassi rams treated with melatonin out of the breeding season

The objective of this study was to evaluate the effect of long-term melatonin treatment applied during the non-breeding season on semen characteristics, endocrine function of testicles and baseline level of insulin-like growth factor-I (IGF-I) in Awassi rams kept in the temperate continental zone of Europe and used as semen donors in an artificial insemination (AI) programme. On 23 February (day 0), slow-release melatonin implants were inserted subcutaneously into rams (n = 8). Control animals (n = 8) received no treatment. In both groups, basic semen parameters (concentration, total motility, fast and slow forward motility, morphology), GnRH-induced testosterone response and basal IGF-I concentration were evaluated on days 0, 47 and 71. No differences were found in concentration of spermatozoa, total motility, and numbers of spermatozoa with fast and slow progressive motility and normal/abnormal morphology between the melatonin-treated and the control group. However, in melatonin-treated animals, basal and GnRH-induced testosterone levels were slightly elevated on day 47 and became significantly higher on day 71 (P < 0.05) as compared to controls. There was no difference in plasma IGF-I levels between the groups. In conclusion, slow-release melatonin applied during the non-breeding season improves testicular testosterone production but does not influence the semen characteristics and the IGF-I level of semen donor Awassi rams used in an AI programme and kept in the temperate continental zone of Europe. © 2009 Akadémiai Kiadó