Dr Sevda Aydin Kurna, Omerli Park 2 Sitesi No: 2, Kadirova Mevkii, Omerli, Cekmekoy, Istanbul, TURKEY, E-mail: email@example.com
A 38-year-old woman wearing hydrogel coloured contact lenses presented to the clinic with a painful red eye and epiphora. On biomicroscopy, a large corneal epithelial defect and ring infiltrate were observed. She had been using topical anaesthetic drops for 10 days. After cessation of the anaesthetic drops, the corneal lesions resolved completely in two weeks. On evaluation of a contact lens user with atypical keratitis, misuse of topical anaesthetics should also be considered.
Anaesthetic abuse keratopathy has been characterised by persistent epithelial defects, disproportionate pain, chronic keratitis and ring infiltration of the cornea. Anterior segment inflammation,1 hypopyon,2 descemetocele3 and corneal perforation have also been observed, ultimately leading to corneal transplantation in the majority of published cases.4 Cases with a relentless downhill course may culminate in enucleation.5
Initial presentation of this rare clinical entity creates difficulties in reaching a correct diagnosis. A presumed acanthamoebic keratitis is the first choice among many similar conditions because of the ring keratitis presentation and characteristic history in a contact lens user.4
This case report describes a soft contact lens-wearing patient referred to the clinic with an acanthamoeba-like keratitis due to topical anaesthetic abuse. The clinical appearance, course and treatment of the atypical keratitis are also described.
A 38-year-old woman presented to the clinic of ophthalmology with a painful red eye and epiphora. She was using daily coloured hydrogel lenses (Phemfilcon A material: Dk/t 16) for correcting her mild myopia. She was obtaining her contact lenses from an optical store, replacing the lenses every three to four months and not presenting for aftercare. She admitted occasionally using her contact lenses in hot tubs, ponds or pools. She had a foreign body sensation in her right eye, which was first noticed 10 days earlier, secondary to extended wear of contact lenses at night. Her ophthalmologist advised her not to use her contact lenses henceforth, started her on topical antibiotics and patched her eyes for a night. She reported an increase in her pain and epiphora in the following two days and then came to us with a non-healing corneal epithelial defect.
Her visual acuities were 6/60 with Snellen chart in the affected right eye and 6/6 in the left eye.
Slitlamp examination of the right eye revealed an oedematous upper eyelid, mild conjunctival hyperaemia, corneal epithelial defect and a corneal ring opacity (Figure 1). Corneal scrapings were obtained under topical anaesthesia with a sterile spatula. Cultures of corneal scrapings were negative and the findings for the left eye were within normal limits.
On repeated questioning she confessed that she was using proparacaine hydrochloride 0.5% (Alcaine, Alcon, Fort Worth, TX, USA) drops every 30 minutes for the previous 10 days to relieve her pain. She had received it from a pharmacist. Although her corneal lesion was clinically similar to acanthamoebic keratitis, the nature of the patient's relapsing pain and the history of frequent use of a topical anaesthetic helped us to differentiate the diagnosis. Topical antibiotic (moxifloxacin, three times daily) as prophylactic therapy was administered with a bandage contact lens. Dosing at three instead of four times per day was preferred because moxifloxacin ophthalmic solution 0.5% exhibits enhanced bioavailability due to a unique molecular structure that is highly lipophilic for enhanced corneal penetration with high aqueous solubility at a physiological pH. This antibiotic has greater activity against gram-positive bacteria than previous generation molecules, while maintaining excellent potency against gram-negative organisms and non-tuberculous (atypical) mycobacteria.6
Bandage contact lenses were preferred as long as the patient had an epithelial defect. The patient complained of intensive eye pain and denied stopping topical anaesthetic usage, which is why she was admitted to hospital for close observation and not permitted to use topical anaesthetics. Diclofenac sodium was injected intramuscularly to alleviate her pain when necessary. In the beginning, the main problem with the therapy was her refusal to quit using a topical anaesthetic and attempts to use it by devious means.
After psychiatric counselling that resulted in prescribing diazepam (Nervium, Saba, Istanbul, Turkey) intramuscularly and orally, the patient's anxiety was relieved. With medical treatment and the cessation of anaesthetic drops, the corneal lesions resolved completely in two weeks (Figures 2 and 3).
Topical anaesthetics are used commonly by ophthalmic practitioners for ocular examination and procedures and are potential causes of toxic keratopathy, which might have a serious outcome.
Currently used topical anaesthetics including tetracaine, procaine, benoxinate and proxymetacaine (proparacaine) inhibit the conduction of corneal nerve impulses. Both tetracaine and proparacaine have toxic effects on stromal keratocytes related to drug concentrations and time exposure.7
Repeated or prolonged application of topical anaesthetic drops leads to inhibition of corneal re-epithelisation, near total cell death within the corneal stroma or scarring and thinning of the stroma.4
Risk factors for anaesthetic abuse might include recent corneal trauma, surgery or infection, psychiatric diseases, low pain-control threshold, history of analgesic drug abuse, access to a topical anaesthetic and symptoms and signs that do not correlate with the clinical history.1,4,5,8 Patients might obtain anaesthetic drops from eye-care practitioners, pharmacists in some countries, theft from practitioners' offices and over the counter in some developing countries.4 Ardjomand and colleagues9 reported a patient who presented with necrotising ulcerating keratopathy due to topical anaesthetic abuse. The patient was a medical doctor and denied using topical anaesthetics. A corneal transplant was performed to relieve the pain and improve vision.
Anaesthetic abuse keratopathy produces significant visual morbidity with the three classic features of Munchausen's syndrome (self-inflicted illness, pathological lying and seeking treatment from many practitioners). Psychiatric consultation might assist with the management of these patients.2
Ophthalmic practitioners should educate patients, primary or emergency caregivers and pharmacists about the potential risk of permanent visual loss in cases of anaesthetic abuse due to the corneal toxicity of topical anaesthetics on the human keratocytes and endothelial cells.7
Topical anaesthetic abuse in the early stages of contact lens use might be easily overlooked by ophthalmic practitioners because the clinical features mimic commonly seen conditions, such as corneal abrasions and ulcers. At presentation, clinicians should distinguish whether eyes are infected or whether they are just sterile infiltrates. Some assessment of corneal sensation might be helpful. Abuse of topical ocular anaesthetic drops should be included in the differential diagnosis of cases with chronic keratitis, as it might masquerade as acanthamoebic keratitis with ring-like keratitis and pain.8
The differential diagnosis of the ring infiltrate includes acanthamoebic keratitis, fungal keratitis, Varicella infection, properdin-mediated rings from bacteria (especially Pseudomonas and Escherichia coli) and recurrent corneal epithelial erosions.10
Acanthamoebic keratitis occurs from an opportunistic free-living soil amoeba that is most commonly associated with incorrect contact lens handling and exposure to unsanitary conditions. Patients with acanthamoebic keratitis typically present with a unilateral painful red eye, initial epitheliopathy progressing to ulceration with infiltration, limbal inflammation, radial keratoneuritis or perineuritis, disciform stromal keratitis, pseudo-dendritic keratitis, anterior uveitis, granulomatous stromal reaction and stromal ring infiltrate.9 The correct diagnosis of acanthamoebic keratitis occurs 23.1 (95% CI, 6.86–77.8) times more often when a ring infiltrate is present.11
Although functional and anatomical results after appropriate treatment are usually poor for anaesthetic abuse, the present case responded well to the cessation of use and the application of a bandage contact lens and topical antibiotic for one week. The corneal ring infiltrate resolved completely within two weeks. This might be related to the early diagnosis and close observation and maintenance of the patient's compliance with strict hospital control.
In conclusion, on evaluation of a contact lens-wearing patient with atypical keratitis, topical anaesthetic misuse should be considered as a possible cause. Early diagnosis might be helpful for improving the prognosis.
This case report was presented as a poster at the 40th ECLSO (European Contact Lens Society of Ophthalmologists) Meeting, 10–12 September 2010, Warsaw.