Octaviano Magalhães

Effect of Needle Type and Injection Technique on Pain Level and Vitreal Reflux in Intravitreal Injection

PURPOSE To evaluate the amount of reflux and degree of pain with intravitreal injection (IVT) using 6 different types of syringes/needles and 5 techniques of scleral incision, including 3 modifications of a beveled scleral incision. METHODS This was a study conducted in 205 eyes of 205 patients. IVT of bevacizumab for retinal pharmacotherapy with 6 types of needles and 5 techniques of scleral incision. The severity of subjectively evaluated pain (0-10) and the width of the subconjunctival bleb arising from the vitreal reflux. Secondary outcomes were increase in intraocular pressure and complication rate. RESULTS The straight technique caused greater vitreal reflux than the beveled approaches, when compared individually or as a group (P < 0.01). No difference in the severity of pain was found among all 5 types of incisions (P > 0.05). There was greater reflux with 26- and 27-gauge needles in comparison to 29- and 30-gauge needles (P < 0.001); however, the width of the needle significantly affected the degree of reflux only when using the nonbeveled incision (P < 0.001). The patients injected with the 26- or 27-gauge needle experienced more pain matched to the 29- and 30-gauge needles (P < 0.001). No difference was found between the incision technique or width of subconjunctival reflux and the increase in intraocular pressure (P > 0.05). Postinjection events included transient mild uveitis, disease-related vitreous hemorrhage, foreign body sensation, conjunctival hemorrhage, and mild punctuate keratitis. CONCLUSIONS The beveled scleral incision showed benefit in performing IVTs. The 29- and 30-gauge needles caused less pain.

Vitreous dynamics: vitreous flow analysis in 20-, 23-, and 25-gauge cutters.

Purpose: To evaluate porcine vitreous flow and balanced saline solution (BSS) flow rates in different vitrectomy systems. Methods: Porcine vitreous was obtained within 24 hours of slaughter. A high-speed (2 samples/s) balance, precise to 0.01 g, was used. Variable cut rates and vacuum pressures were analyzed in vitreous and BSS. The vitreous was labeled with glass microspheres and triamcinolone acetonide. A high-speed (400 frames/s) camera was used to record cutting for each condition. Results: For all cutters, there was no vitreous flow at zero cut rates (off). In 25-gauge cutters, at 500 mmHg of vacuum, the electric cutter produced higher average flow rates at high cut rates (600 cpm, 0.004 mL/s, and 1500 cpm, 0.013 mL/s) than pneumatic, which demonstrated a decreased flow at speeds higher than 1000 cpm (1000 cpm, 0.015 mL/s, and 1500 cpm, 0.006 mL/s). The percentage of vitreous flow rate/BSS flow rate in different aspiration and cut rates showed an ascending curve. This demonstrates evidence of flow obstruction in 25- (all cut rates), 23- (all cut rates), and 20-gauge (all cut rates). Flow obstruction and surge movements were seen in the high-speed videos. Conclusions: The vitrectomy systems each illustrate different performances of vitreous removal. The physical characteristics of vitreous resulted in nonuniform flow in all vitreous cutters.

Ability of New Vital Dyes to Stain Intraocular Membranes and Tissues in Ocular Surgery

PURPOSE To evaluate the ability of novel dyes to stain lens capsule (LC), internal limiting membrane (ILM), epiretinal membrane (ERM), and vitreous. DESIGN Experimental study in animal and human donor eyes. METHODS Thirteen dyes, methyl violet, crystal violet, eosin Y, sudan black B, methylene blue, toluidine blue, light green, indigo carmine, fast green, congo red, evans blue, brilliant blue, and bromophenol blue, were injected onto the LC and ILM of enucleated porcine eyes. The vitreous was stained with 2 mL of dyes for 1 minute. Six dyes (indigo carmine, evans blue, fast green, light green, bromophenol blue, and brilliant blue) were selected for experiments in human donor eyes and freshly removed ERM. RESULTS In the porcine eyes, ILM staining with methylene blue, toluidine blue, indigo carmine, evans blue, bromophenol blue, and fast green was moderate, and methyl violet, crystal violet, brilliant blue, or sudan black resulted in strong staining. Methyl violet, crystal violet, sudan black, toluidine blue, and methylene blue caused histologic damage in porcine retinas. Vitreous examination revealed moderate staining with congo red, crystal violet, fast green, eosin Y, methylene blue, toluidine blue, brilliant blue, bromophenol blue, and methyl violet and strong staining with light green and evans blue. ERMs showed strong staining with 0.5% evans blue and moderate staining with 0.5% light green, fast green, brilliant blue, and bromophenol blue. Evaluation of donor eyes disclosed moderate staining with evans blue, light green, and bromophenol blue and strong staining with 0.5% brilliant blue. Moderate or strong staining of the vitreous occurred with most dyes. LC evaluation showed moderate staining with 0.5% evans blue, fast green, and brilliant blue, whereas 0.5% light green produced strong LC staining. CONCLUSIONS Brilliant blue shows the best ILM staining, whereas bromophenol blue, evans blue, and light green also stain ILM. Most dyes bind well to LC, vitreous, and ERM.

Retinal and Ocular Toxicity in Ocular Application of Drugs and Chemicals – Part II: Retinal Toxicity of Current and New Drugs

Aims: Retinal pharmacotherapy has gained great importance for the treatment of various retinal diseases. An increasing number of drugs have been constantly released into the market, especially for wet age-related macular disease and diabetic macular edema. In this review, the issues concerning the toxicity of current and new classes of drugs are discussed. Methods: An extensive search of the literature was performed to review various aspects of drug toxicity in retinal pharmacotherapy. The different major classes of drugs, such as corticosteroids, antibiotics, antimetabolites, antineoplastic agents, monoclonal antibodies (mAbs), nonsteroidal anti-inflammatory drugs, enzymes, fibrinolytics, miscellaneous anti-inflammatory and antiangiogenic agents, as well as toxicity unrelated to the drug were identified and discussed. Results: Corticosteroids like fluocinolone, dexamethasone or triamcinolone at low dose cause little damage to the retina, but at high doses signs of toxicity have been well documented. Complications like cataract and glaucoma are quite common with corticosteroids. Aminoglycosides showed differences in the type and doses associated with toxic reactions, thereby the following order of toxicity can be described (from most toxic to least toxic): gentamicin > netilmicin = tobramycin > amikacin = kanamycin. Vancomycin at the usual dose of 1 mg is not toxic to the retina, while further studies are necessary in order to clarify the safety of new-generation quinolones. 5-Fluorouracil has been shown to be nontoxic to the retina after an injection of 2.5 mg in animals. mAbs like ranibizumab and bevacizumab were demonstrated to be safe to the retina in cell culture, animals and humans at high doses. The exact biocompatibility of nonsteroidal anti-inflammatory agents like diclofenac needs further evaluation. Preservatives like benzyl alcohol and changes in pH or osmolarity exert an influence on the toxic effects of intravitreally applied drugs. Conclusions: A great number of drugs are now used mainly intravitreally without relevant retinal toxicity.

Subretinal bevacizumab detection after intravitreous injection in rabbits.

PURPOSE To evaluate subretinal detection of bevacizumab 2 hours after intravitreous injection of 1.25 mg in rabbit eyes. METHODS Anterior chamber paracentesis using a 30-gauge needle was performed in nine female Dutch-belted rabbits by removal of 0.05 mL of aqueous humor. Transscleral retinal detachment was performed with a modified 25-gauge infusion cannula connected to a bottle of physiologic saline solution (PSS). The animals were divided into experimental group 1, with intravitreous injection of 0.05 mL of (1.25 mg) with a 30-gauge needle (n = 6) and the control group 2, with intravitreous injection of 0.05 mL of PSS with a 30-gauge needle (n = 3). Two hours after the intravitreous bevacizumab or PSS injection, subretinal fluid was aspirated and immunoassayed to measure the level of bevacizumab. The rabbits were killed by intravenous pentobarbital injection. The eyes were enucleated and fixed in 10% formaldehyde. The pars plana site at which the transscleral cannula was introduced was analyzed by light microscopy, to exclude iatrogenic retinal tears. Eyes with accidental retinal tears were excluded. RESULTS Subretinal bevacizumab molecules were detected in the six eyes that received an intravitreous bevacizumab injection. No subretinal bevacizumab was detected in the control eyes. Light microscopy showed no evidence of retinal tears or holes in any rabbits used for the bevacizumab detection and control group. CONCLUSIONS Bevacizumab molecules were detected in the subretinal space after intravitreous injection of 1.25 mg of bevacizumab, possibly as the result of diffusion through the retina in a rabbit model.

Fluid dynamics in three 25-gauge vitrectomy systems: principles for use in vitreoretinal surgery.

Purpose:  To compare infusion and extrusion fluid volumes with three 25‐gauge vitrectomy systems.

Experimental investigation of needles, syringes and techniques for intravitreal injections

Background:  To assess the techniques and materials used in intravitreal injections.

Perspective on Fluid and Solid Dynamics in Different Pars Plana Vitrectomy Systems

PURPOSE To summarize current concepts and recent data from the literature about different vitrectomy machines and small-gauge systems based on physical laws. DESIGN Interpretive essay. METHODS Review and synthesis of selected recent literature with interpretation and perspective. RESULTS Pars plana vitrectomy can be performed with a wide variety of treatment strategies, for multiple diseases, and with different materials (solids and fluids). We discuss a variety of machines and system settings (peristaltic pump, duty cycle, aspiration, and infusion controls) targeting safer and the most effective surgery with detailed explanations of the physical properties. CONCLUSIONS Effective management of new surgical strategies is based on recognizing and addressing various physical characteristics in disease and ocular settings. Although the properties of machine are expanding, the long-term efficacy and safety of most new approaches have yet to be established in controlled clinical trials.

Effect of lens status in the surgical success of 23-gauge primary vitrectomy for the management of rhegmatogenous retinal detachment: the Pan American Collaborative Retina Study (PACORES) group results.

Purpose: To determine the effects of lens status on the success rate of primary pars plana vitrectomy (PPV) for rhegmatogenous retinal detachment using either perfluoropropane gas (C3F8) or silicone oil (SO) tamponade. Methods: A retrospective chart analysis was made of 97 eyes from 92 patients with rhegmatogenous retinal detachment with no proliferative vitreoretinopathy that were treated with primary 23-gauge PPV. Eyes included in this were phakic (n = 28), pseudophakic (n = 41), or phakic eyes subject to simultaneous phacoemulsification, intraocular lens implantation, and PPV during primary rhegmatogenous retinal detachment repair (n = 28). Tamponade at the end of PPV was with either C3F8 (n = 65) or SO (n = 32). Success was defined as retinal reattachment at 1 year follow-up after a single procedure in eyes submitted to C3F8 injection; in eyes treated with SO injection, the success rate was defined as retina reattached 1 year after oil removal. Statistical comparisons were made between groups using chi-square, Fishers exact test, Kruskal–Wallis, Mann–Whitney, and multivariate analysis. All eyes were operated by 2 experienced retina surgeons and had a minimum follow-up of 12 months. Results: The vitreoretinal redetachment rate in eyes subjected to C3F8 tamponade was significantly higher (28.6%) for phakic eyes (P = 0.011) compared with pseudophakic or phakic eyes that underwent to phacoemulsification and intraocular lens implantation (4.5%). Eyes in which SO was used at the end of the surgical procedure demonstrated a similar trend of higher reoperation rates in phakic eyes (28.6%) compared with pseudophakic or phakic eyes (8%) subjected to phacoemulsification and intraocular lens implantation; however, no statistically significant difference was observed (P = 0.201). No statistically significant differences were found between groups in relation to the number of tears (P = 0.863) and their location (inferior: P = 0.189, superior: P = 0.708, nasal: P = 0.756, and temporal: P = 0.08). Conclusion: The success rates of primary 23-gauge PPV with either C3F8 or SO tamponade in pseudophakic eyes with rhegmatogenous retinal detachment was higher than the same procedure performed in phakic eyes. Still, the retrospective and limited data presented is too preliminary to suggest or recommend that practitioners perform simultaneous combined cataract surgery with retinal detachment and requires further studies in a larger and prospective design to confirm these present findings.

Analysis of a 23-gauge ultra high-speed cutter with duty cycle control.

Purpose: The purpose of the study was to determine the performance of dual pneumatic ultra high–speed 23-gauge cutters operated with variable duty cycle (DC) settings. Methods: Frame-by-frame analysis of high-speed video was used to determine the DC in core, 50–50, and shave modes. Using three cutters at various cycles per minute and aspiration levels, mass of water or vitreous removed from a vial was measured within a specified time period. Average flow rates were calculated for each aspiration level and cut rate with the different DC options. Results: The DC increased with increasing cut rate in the shave mode was relatively stable in the 50–50 mode and decreased for the core mode. The DC converged at 5,000 cycles per minute for the 3 different modes. Water flow curves followed the DC variation. Vitreous flow rates for all the DC modes increased with increasing cut rates and peaked at 5,000 cycles per minute (P < 0.05). The results of the 50–50 mode, which had isolated the DC influence, showed that increasing aspiration and/or cut rate independently increased the vitreous flow rate. Conclusion: Progressive values of aspiration and/or cut rate increase the vitreous flow rate, independently of the DC. The DC control also has an important effect on the vitreous flow, but this effect was reduced at high cut rates because of convergence of the DC modes.