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Sir,

Conjunctival follicles are known to occur as a result of ocular allergy to topical glaucoma medication, and are located mainly in the inferior bulbar and palpebral conjunctiva. Ocular allergy to topical treatment is associated with symptoms of burning and stinging; however, these symptoms settle and the conjunctival follicles disappear after discontinuing the offending agent. We report a case of bilateral multiple limbal and palpebral conjunctival follicles in a glaucomatous patient.

Case report

An 85-year-old Caucasian man presented in 1998 with hand movement (HM) vision in both eyes. A diagnosis of advanced open angle glaucoma with age-related macular degeneration (AMD) was given and he was registered blind. He had a presenting intraocular pressure (IOP) of 31 and 35 mmHg in the right and left eye, respectively. Retinal examination showed bilateral 0.95 cup/disc ratios with extensive AMD. He had a history of asthma, thus beta-blockers were contraindicated. After a 3-week trial, he became intolerant of Latanoprost 0.005%, which caused symptomatic blurring of vision. He was subsequently treated with topical dorzolamide 2% tds and brimonidine 0.2% to both eyes. No further blurring occurred, and IOP remained stable for 4 years. At this stage the right IOP control deteriorated, and the corresponding visual field showed progressive field loss. An augmented microtrabeculectomy was planned. Surgery at the time of preoperative assessment was postponed however, due to the presence of bilateral, multiple limbal conjunctival follicles (Figure 1). The follicles were noted to occur on the superior and the inferior aspect of the bulbar conjunctiva without any other signs of ocular allergy such as injection or corneal erosions. The patient denied any ocular discomfort or irritation.

Figure 1
figure 1

Anterior segment showing conjunctival limbal follicles.

Visual acuity remained at HM in each eye, and anterior segment examination was unremarkable with no vitreous or retinal inflammation. The IOP was 19 mmHg in both eyes. The dorzolamide and brimonidine were stopped, and pilocarpine 2% preservative free and acetazolamide SR 250 mg po commenced. Chest X-ray, serum angiotensin converting enzyme, calcium, C reactive protein, and autoimmune screen were all normal. The erythrocyte sedimentation rate was 46 mm/h.

After 3 weeks, the follicles were still present albeit in a reduced number, and a right-sided inferior conjunctival biopsy preformed. Histology showed nonspecific infiltrate of lymphocytes and plasma cells without any granulomas. The conjunctival follicles gradually disappeared over the next 3 months. The IOP was maintained on the pilocarpine and acetazolamide. The patient has remained symptom-free throughout.

Discussion

Unlike oral carbonic anhydrase inhibitors that rarely cause ocular side effects, topical dorzolamide is known to cause various effects: stinging, burning, tearing, and blurring of vision. A 4% incidence of lid and/or conjunctival allergy has been reported.1 Brimonidine is also known to cause ocular adverse effects such as hyperaemia, pruritus, foreign body sensation, blurred vision, and stinging sensation. Ocular allergy has been reported in 9.6% of cases.2 In our case the patient was completely asymptomatic, and only on preoperative examination were the presence of bulbar conjunctival follicles noted. Unusually, these were located 360° around the limbus and not just in the inferior aspect of the conjunctiva, thus prompting a search for a systemic cause. Hypersensitivity to either one or both the topical antiglaucoma agents was suspected. In many patients with allergic reactions, the adverse effect is due to the preservative rather than the antiglaucoma agent3 and, considering both agents contain benzalkonium chloride, sensitivity to this preservative cannot be excluded. To confirm our suspicions, ideally the patient would need to be re challenged with the suspected antiglaucoma agents and benzalkonium chloride. It was deemed inappropriate, however, to re-challenge the patient. Withdrawal of the topical agents led to gradual follicle resolution, and since no systemic cause was found and histology confirmed nonspecific inflammation the conjunctival reaction was labelled a probable adverse drug reaction using the criteria proposed by Naranjo et al4 to assess causality of adverse events by drugs.

We recommend that patients about to undergo glaucoma surgery be carefully examined for any signs of ocular allergy even if the patient is asymptomatic.