An Injection Primer, Part 1
BY WILLIAM L. MILLER, OD, PHD, FAAO
Nearly half of the continental United States have authorized optometrists to perform injections. Only about one third of states that allow injections provide a provision for subconjunctival and intralesional injections.
My last column addressed the issue of chalazia management and briefly described intralesional injections. This column provides a more detailed description of basic and intralesional injections.
Because the injection will bypass the body's natural barrier system (skin or conjunctiva), you must observe universal precautions (see The Occupational Safety and Health Administration's [OSHA] regulations on bloodborne pathogens at www.osha.gov). Before making the injection ensure that the necessary medication, syringe, needle, topical anesthetic, forceps, alcohol preps, disposable gloves and bandages are available on an instrument tray.
Most syringes used for ophthalmic delivery range from 1ml to 5ml in size, but the 1ml (tuberculin) is used most often. The diameter of the needle typically falls between 20-gauge and 30-gauge (smaller gauge indicates a larger diameter). Injections into ocular structures typically require 27-gauge to 30-gauge needles with larger needles used to withdraw medication. Smaller gauge needles facilitate medication retrieval because many medications used for ocular delivery are viscous and difficult to retrieve from a vial. Medication vials are capped with a silicone or rubber stopper that you must prep with alcohol before withdrawing the medication. Before medication retrieval, apply an equal amount of air into the vial to facilitate flow into the syringe.
For a chalazion injection, fill a tuberculin syringe using a small gauge needle (20-gauge or
23-gauge) with approximately 0.3cc of triamcinolone acetate. The particular bolus of medication will depend on the lesion size. A percutaneous injection is usually preferred, so clean the skin with an alcohol prep before the procedure. Allow sufficient drying to eliminate any burning upon injection.
Apply a chalazion clamp to the lid to allow access to the chala-zion and provide a barrier for inadvertent lid penetration. Replace the 20-gauge or 23-gauge needle with a 27-gauge needle for injection. With the bevel facing you, the needle will tend to displace deeper into the lid, but the chalazion clamp will prevent penetration through the lid and into the globe. Some practitioners apply a topical anesthetic to the skin before injection, but most patients experience more discomfort from the chalazion clamp than from the injection.
Apply the needle into the proximal aspect of the chalazion through the skin. Advance the needle to the distal aspect of the lesion, then apply the steroid. Before medication application, aspirate to ensure that the needle has not entered a blood vessel. This is rare given the relative size of the needle. While injecting the steroid, slowly remove the needle through the entire aspect of the lesion until you withdraw it back through the proximal lesion entry point. You can apply pressure through stacked gauze pads to prevent bleeding.
You can also perform this procedure transconjunctivally, in which case you may use a topical anesthetic agent to facilitate the injection.
Dispose the needle and syringe into a properly labeled Sharp's container. Never recap the needle because this increases the risk of needle sticks and is also against OSHA regulations. You can autoclave some instruments (such as the chalazion clamp) after use, but place any other materials that have been contaminated with blood into a biohazard bag.
Dr. Miller is on the faculty at the University of Houston College of Optometry. He is a member of the American Optometric Association and serves on its Journal Review Board. You can reach him at firstname.lastname@example.org.