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E. B. Rodrigues, O. Magalhaes Jr., F. M. Penha, E. Dib, M. Maia, J. Abechain, V. Stefano, M. E. Farah; Investigation on the Techniques, Syringes and Needles Used in Intravitreal Injections. Invest. Ophthalmol. Vis. Sci. 2010;51(13):5131.
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Intravitreal injections (IVT) are the main drug delivery method for retinal pharmacotherapy. The purpose of this study was to evaluate several features in regard to the techniques, syringes and needles used for IVT.
Seven aspects in patients and laboratory were investigated: 1. The outcome of various needles sizes (26, 27, 29, 30G; and 8, 12.7, 13mm) on the pain, reflux and ocular pressure changes; 2. Efficacy of a beveled scleral incision to prevent vitreal reflux; 3. Variations of entry&exit angle of the needle in beveled incisions; 4. Benefit of a roll-over technique to examine the vitreous base right after IVT; 5. Ultra-structure of needles for IVT with electron microscopy; 6. Composition of vitreal reflux after IVT with trypan blue; 7. Extent of the amount of residual volume in syringes/needles with high-precision weight-scale.
1. Smaller needles of 29- and 30G promoted less reflux and pain (P <0.001), and no increase in intraocular pressure was noticed (P> 0.05); 2. The beveled scleral incision decreased diameter of subconjunctival bleb from 3 mm to 1 mm (P <0.01); 3. The angle of entry is important for formation a successful scleral tunnel, although the angle of exit of the syringe/needle poses no influence on the reflux degree; 4. The roll-over technique allows great visualization of the vitreous base and peripheral retina after IVT; 5. Electron microscopy showed many unexpected irregularities and debris on the surface of all needles, while the angle and shape of the tip of needles varied; 6. The vitreal reflux was colored mostly dark blue similar to trypan blue but not transparent as the vitreous; 7. Long needles attached to smaller syringes of 0.3ml demonstrated smaller residual volume in the experimental set-up.
Ultra-structure of needles varies among commercial brands, and their surface shows irregularities and debris which may promote inflammatory reactions. Drug may be lost due to the vitreal reflux. Smaller-gauge needles and beveled incisions cause less vitreal reflux. The 29- & 30-gauge needles induce less pain.
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