Photokeratitis: Arc Eye & Snow Blindness - PDF

Arc eye, welder's flash and snow blindness are descriptive terms that specify why a patient has light-induced damage of the corneal epithelium (photo or actinic keratitis). They are common conditions encountered by all doctors from time to time. In almost every case the patient will know exactly why...

Arc eye, welder's flash and snow blindness are descriptive terms that specify why a patient has light-induced damage of the corneal epithelium (photo or actinic keratitis). They are common conditions encountered by all doctors from time to time. In almost every case the patient will know exactly why they have an eye problem and making the diagnosis is easy. Treatment is simple and most cases can be dealt with by GPs. Included in this document History Examination Differential Management Follow up When to refer Patient counselling Key points History Making the diagnosis is usually straightforward. Many patients volunteer the diagnosis as soon as they walk in the door and most are fully aware why they are in distress. If you do need to take a history, ask about skiing, high altitude climbing, welding (or watching someone weld) and use of a sun bed or lamp with or without eye protection. Some patients have had multiple episodes. Patients typically experience increasing pain and photophobia a few hours after exposure to ultraviolet or far-blue light. Because the symptoms begin 6–12 hours after exposure many people retire to bed fine only to awake in distress a few hours later. By the time they see you in the middle of the night or early the next morning they are usually in severe pain, exhausted and completely miserable. Affected eyes are very painful, photophobic, profusely watery and impossible to open. The report ‘It’s like someone threw sand/acid in my eyes’ is very common. Examination Patients are best examined in a darkened room after the liberal administration of a topical anaesthetic such as amethocaine. Although pain relief with anaesthetic is usually instantaneous, reflex tearing takes a few minutes to settle so wait before checking the vision and pinhole vision. The vision should be near normal. Look for ‘sunburn’ on the face and around the eyes. Some patients have quite marked lid oedema. The eyes are usually diffusely red and the conjunctiva may be oedematous. The pupil is small because light scattered by the damaged epithelium is a powerful stimulus to pupillary constriction. Instil fluorescein into the tears and look for corneal staining. You don’t usually need a blue light or slit lamp to see the typical and usually severe corneal changes. The damaged cells of the corneal epithelium are either swollen or lost and this gives rise to the typical staining patterns seen in these patients. In some patients, swollen epithelial cells jut out into the tear film, and appear as dark spots in the sea of fluorescein stained tears (Fig. 1). In other cases, epithelial cell loss creates small ‘potholes’ on the corneal surface (Fig. 2). The fluorescein stained tears are thicker in these areas and appear as bright areas of fluorescein ‘staining’ (Fig. 2). Usually a mixture of patterns is seen and the changes are most prominent in the area of the cornea which is not normally covered by the eyelids, i.e. the centre one-third or ‘interpalpebral’ area. The cornea is otherwise crystal clear, because the deeper corneal layers are unaffected. Fig. 1. Actinic keratitis. Swollen Fig. 2. Actinic keratitis. epithelial cells protrude into and thin Fluorescein stained tears fill the fluorescein stained tears and areas of epithelial cell loss and appear as small black islands in a sea the thicker tear film in these of green. areas results in bright  fluorescein spots. Differential The history, symptoms and signs of actinic keratitis are usually very typical. Contact lens overwear can mimic the disease but these patients are also highly aware of why their eyes are so painful. The symptoms of lagophthalmos (the eyelids drift open while sleeping, allowing the cornea to dry) are similar but usually much less severe. Management Treatment of actinic keratitis is essentially supportive as the cornea almost always heals rapidly and without consequence. First and foremost the patient needs good pain relief until the cornea heals itself. Secondly the cornea needs to be protected so that infection, although very rare, does not develop. Whatever you do, DO NOT be tempted to give or prescribe topical anaesthesia. Sometimes you have to watch patients very carefully as theft of topical anaesthetics by sufferers of actinic keratitis is not uncommon. Local anaesthesia is contraindicated because its use slows epithelial healing and masks both non-resolution and the development of complications. Be generous however, with oral analgesia. The condition is very painful and makes it very difficult to sleep. Consider a hypnosedative. Except in mild cases, instil an antibiotic ointment such as chloramphenicol into the eyes and pad either the most affected eye or both eyes. Firm padding prevents the patient's lids from moving and thus provides significant pain relief. The ointment creates a greasy layer between the eyelid and damaged epithelium and gives further relief. A further drop of topical anaesthetic at this point will make these tasks much easier (and also make the patient's trip home easier to bear). Use a double pad technique, as the lid must be held firmly down. Fig. 3 demonstrates the proper double pad technique. You do not need to tape the eyelid and there is no need to apply a layer of gauze. Ask the patient to keep both eyes gently closed until the whole operation is completed. Fold the first pad in half and secure the second over the top. The pattern with which the tapes are applied is critical. Pull the tape tight and arc the second and third tapes around to ensure that the medial and lateral parts of the pad are pushed down firmly onto the eyelid. Fig. 3. Double padding an eye. The first pad is folded in half. Tapes are then applied over the second pad in an arcuate fashion so that they compress the pad onto the full extent of the upper eyelid. If patients are in severe pain, consider instilling several drops of cyclopentolate to relieve pupillary and ciliary spasm. Cyclopentolate lasts for about twelve hours. Do not use tropicamide or atropine which last for four hours and two weeks respectively. A medical note allowing the patient a day off work is not unreasonable as it will be 24–48 hours before the eyes are back to normal. Follow up Most cases do not need to be reviewed again. Patients should be instructed to remove the eye pad 24 hours later and, if the eye feels better, instil antibiotic ointment for a further 24 hours. If the eyes are not better when the pad comes off or if they are not essentially back to normal within 48 hours they should see you again. Patients who require review should be carefully checked for signs of corneal infection. When to refer Any patient with decreased vision and corneal opacification requires immediate review by an ophthalmologist. Patient counselling Actinic keratitis is a relatively benign condition. Nevertheless the condition should serve as a warning that the patient has received high doses of solar radiation which are not without risk to the patient's eye and skin. This is particularly true in welders who often have a rather blase attitude to ‘arc eye’. Patients should be encouraged to review their eye protection and seek advice on this from an optometrist, optician or the Cancer Society. Key points There should be a clear history of light exposure. Examination usually requires the instillation of local anaesthesia, but  anaesthetic agents should not be given to the patient to take away as they delay healing and mask the development of sinister complications. The key to treatment is a combination of oral analgesia, eye ointment, cycloplegia, padding and rest. A sedative may be required. Most patients do not require review unless their symptoms fail to settle after 48 hours. © GP Eyes - Dr Malcolm McKellar 2011