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Editor,—Long acting periocular corticosteroids are commonly used to treat cystoid macular oedema (CMO) resulting from ocular inflammation or cataract surgery that does not respond to topical therapy. Drug localisation to the macular area is considered important for optimal therapeutic effect. In post-cataract CMO refractory to topical therapy, corticosteroids delivered by retrobulbar and posterior sub-Tenon's injections are equally effective.1 Steroids given by sub-Tenon's injection have previously been shown to localise to the macular area.2Retrobulbar anaesthetic injections have been shown to localise in the intraconal space, but not precisely to the macular area.34 We performed ultrasonography after retrobulbar steroid injection to confirm drug localisation in the macular area.
Sixteen patients with chronic CMO secondary to sarcoid, idiopathic uveitis, or cataract surgery (Irvine-Gass syndrome) were included in the study. The main inclusion criteria were presence of a visually significant form of CMO that had either failed topical anti-inflammatory treatment, or was deemed clinically severe enough to warrant systemic or periocular injections of corticosteroids primarily, and willingness to sign informed consent. The main exclusion criteria was refusal to consent to the procedure.
Each eye was injected with 1–2 ml of 40 mg/ml triamcinolone acetonide mixed with 0.5 ml of 2% lignocaine (lidocaine) without adrenaline (epinephrine) using a sharp 1½ inch 25 gauge needle. The needle was inserted at the inferotemporal aspect of the lower lid aiming in the direction of the orbital apex. The patient was asked to look straight ahead while the globe was balloted towards the superior orbit with the index finger of the non-injecting hand. Once the needle was positioned in the muscle cone near the posterior pole, the solution was slowly injected.
B-mode ultrasound was performed within 30 minutes of the retrobulbar injection. After topical proxymetacaine (proparacaine) was given, a methylcellulose coupling agent was placed on the ultrasound probe, which then was directly applied to the ocular surface. Standard longitudinal, vertical transverse, and axial planes were imaged (Figs 1and 2).
In 15 of 16 (94%) eyes the steroid was localised to the macular area defined as the portion of the posterior pole bounded by the optic nerve, major temporal arcades, and 3 mm temporal to the fovea. In eyes where the bolus localised to the macular area, the mean distance between the most anterior aspect of the bolus and the retina was 2 mm with a range of 1–3 mm. In one eye, the steroid bolus was not visualised by ultrasonography. The injections were well tolerated, and no complications occurred.
Depot steroids are an important therapy for treating CMO which is unresponsive to topical therapy. Drug localisation to the macula is considered to be important in maximising therapeutic effect. Steroid therapy delivered by sub-Tenon's and retrobulbar injections is equally effective, and steroids given by sub-Tenon's injection have been localised to the macula previously. The localisation of retrobulbar injections to the macular area may explain the similar efficacy of retrobulbar and sub-Tenon's injection in the treatment of CMO.1 Retrobulbar injection is a procedure familiar to most ophthalmologists, and the decision to perform either a sub-Tenon's or a retrobulbar injection should take into consideration the degree of comfort the administering physician has with the technique.
Financial support: Heed Fellowship (MJT).
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