Author details

Dr. Mohammad Ihsan Fazal (BMBS BSc)

Foundation Year Two Doctor, Watford General Hospital, West Hertfordshire Hospitals NHS Trust, UK

Aims

This article aims to introduce the reader to intravitreal injections and to describe the basic technique and considerations of performing the procedure.

Introduction

Intravitreal injection is the delivery of a drug via needle directly into the vitreous humour. This is useful in conditions where there is retinal oedema such as in wet AMD, diabetic macular oedema, or retinal vein occlusion. In these conditions, drugs such as Anti-VEGF or corticosteroids are injected intravitreally. These drugs diffuse across the pathological blood retina barrier and act on the retinal blood vessels to reduce neo-vascularisation and inflammation and ultimately reduce the degree of retinal oedema. Intravitreal injections can also be used to administer antimicrobials in case of endophthalmitis. Intravitreal drugs usually need to be given as a course of several injections. Some of the commonly used intravitreal drugs in the UK include Eylea (Aflibercept), Lucentis (Ranibizumab) and Ozurdex (Dexamethasone). These drugs are usually in a pre-prepared syringe with other required equipment available in sterile intravitreal injection packs.

Informed consent

Prior to injection, informed consent should be obtained. When consenting the patient for the procedure you should inform them of reason for the injection and the possible complications.

The main aim of intravitreal injections is to improve or prevent further deterioration in vision. There are specific indications dependent on underlying pathology. For example, in endophthalmitis, intravitreal injection of antibiotics is done to eradicate the pathogen from the eye. However, in wet AMD the indication is to reduce the macular oedema.

The main possible complications of intravitreal injections are:

• Endophthalmitis
• Retinal tears or detachment
• Traumatic cataract
• Subconjunctival or vitreous haemorrhage

Preparation

After obtaining informed consent from the patient and confirming the eye and drug to be injected local anaesthesia should be administered. In most cases, topical eyedrops such as tetracaine should be sufficient, however, some patients may benefit from subconjunctival or retrobulbar block – for example, an inflamed eye in endophthalmitis. The patient should be positioned supine with good head support as nervous patients may involuntarily extend their neck and push back into the headrest.

Ensure all equipment is present before scrubbing hands and donning sterile gloves. Most available intravitreal drugs come in a prepared syringe from which air needs to be expelled to prevent air bubbles in the eye. Ensure this is done before cleaning the eye with povidone-iodine 5% solution and draping the eye. Evidence suggests that draping is not necessary and this is reflected in guidelines, however, drapes are often present in the sterile equipment pack, there is no harm in using them and it allows an ophthalmology trainee to practice draping properly (Pilli et al 2008).

Once the eye is draped and anaesthetised, speculums need to be inserted to prevent the eyelids / lashes interfering with the procedure and contaminating the needle. An early study of Anti-VEGF indicated an increased number of complications when speculums were not used (Gragoudas 2004). Speculum insertion can be made easier by asking the patient to look down while inserting the upper blade and to look up while inserting the lower blade. This should be followed by instilling a drop of povidone-iodine to the ocular surface before proceeding with injection.

Identifying Injection Site

After the speculum is inserted, an IVT marker is used (available as part of the sterile IVT pack) to mark the site of injection. Measuring posterior to the corneoscleral limbus, 4mm is recommended for phakic eyes and 3.5mm for pseudophakic eyes. The reason for this is to avoid hitting the crystalline lens/IOL with the needle and potentially causing a traumatic cataract or lens dislocation. Injecting at a point further than this measurement can lead to retinal tears or detachments depending on the path of the needle. The inferotemporal quadrant is the preferred injection site as the hand does not have to contend with the patient’s nose and is freer to manoeuvre. Additionally, asking the patient to look away from the injection site increases the area available to work in i.e. encouraging the patient to gaze superonasally for an inferotemporal injection. The superotemporal quadrant is also a popular injection site as if a tear occurs it is easier to repair with pneumatic retinopexy.

Injecting

Upon marking the injection site, the syringe with 30-gauge needle should be held perpendicular to the ocular surface in the dominant hand with the wrist anchored onto the patient’s cheek for stability. Insert the needle at the marked site and depress the plunger with the non-dominant hand or available fingers on the dominant hand. While doing this, be careful not to exert pressure on the eye through the syringe as this can be quite uncomfortable for the patient. Upon removal of the needle instilling topical antibiotic such as chloramphenicol is commonly done however, no randomised controlled trials show a reduction in endophthalmitis with antibiotic use post-intravitreal injection (Moss et al, 2009).

Post-procedure

Once the procedure is complete, the drape should be removed, and povidone-iodine wiped from the patient’s eye with gauze soaked in BSS or distilled water. If the patient requires an injection in the other eye, this can be done in the same session as bilateral intravitreal injections are considered safe (Chao et al, 2014).

After-care

The patient should be informed that they will likely see an increase in floaters for the next 24-48 hours due to air bubbles. They should also be made aware of the symptoms of retinal detachment or endophthalmitis in case of complications and where to go if they experience these symptoms. Patient follow-up should be dictated by the underlying condition.

References

Chao DL, Gregori NZ, Khandji J, Goldhardt R. Safety of bilateral intravitreal injections delivered in a teaching institution. Expert Opin Drug Deliv 2014;11(7):991-3.

Gragoudas ES, Adamis AP, Cunningham ET, Jr., Feinsod M, Guyer DR, Group VISiONCT. Pegaptanib for neovascular age-related macular degeneration. N Engl J Med 2004;351(27):2805-16.

Moss JM, Sanislo SR, Ta CN. A prospective randomized evaluation of topical gatifloxacin on conjunctival flora in patients undergoing intravitreal injections. Ophthalmology 2009;116(8):1498-501.

Pilli, Suman; Kotsolis, Athanasios; Spaide, Richard F.; Slakter, Jason; Freund, K. Bailey; Sorenson, John; Klancnik, James; Cooney, Michael. Endophthalmitis Associated with Intravitreal Anti-Vascular Endothelial Growth Factor Therapy Injections in An Office Setting American Journal of Ophthalmology 2008; 145 (5): 879–882.