Contact Lenses PDF

Every GP has patients who wear contact lenses and will, from time to time, have to treat both contact lens related problems and eye disease in patients who wear contact lenses. Included in this document Why contact lenses? Types Problems and their management Tips When to refer...

Every GP has patients who wear contact lenses and will, from time to time, have to treat both contact lens related problems and eye disease in patients who wear contact lenses. Included in this document Why contact lenses? Types Problems and their management Tips When to refer Why contact lenses? People wear contact lenses for a variety of reasons. For many, the principal attraction is cosmetic, but there are considerable optical benefits as well. Contact lenses don't fog up and can’t be knocked off like spectacles. They are useful in wet environments and when playing sport. Some patients, for example those with keratoconus and high myopia, see much better with contact lenses than with glasses. The principal disadvantages are cost and inconvenience. Apart from the initial outlay and cost of replacement, contact lenses require specialised solutions and cleaning regimes. It takes several minutes a day to clean your contacts, and the solutions which you need to carry with you, cost several hundred dollars a year. Types There are two kinds of contact lenses; 'hard' and 'soft'. Hard lenses are made of rigid, partially oxygen-permeable ('gas- permeable') materials. They float in the tear film and effectively replace the front surface of the cornea. Hard lenses are more difficult to get used to and need to be worn for a similar period of time each day. Hard lenses can correct a wider range of refractive abnormalities than soft lenses, including keratoconus and corneal scarring, but they are more brittle and unsuitable for contact sports. Soft lenses are more of a lifestyle lens; they are easier to adapt to and patients can adopt a much more flexible wearing regime. They are ideal for sport and can be used cosmetically to change the appearance of the eye. They are made from materials that have a very high water content and wrap themselves onto the corneal surface. Because of this they are less likely to result in vision as good as that possible with hard lenses, particularly if the corneal surface is irregular or the patient has high astigmatism. Some patients develop allergic problems from allergen (denatured tear proteins, pollens and cleaning solutions) sequestration within the lens substance. Problems and their management Fig.1. Multiple epithelial abrasions following difficulty removing a contact lens. Corneal abrasions Corneal abrasions can occur at the time of insertion or removal and when the eye is subjected to trauma (Fig. 1). Simple abrasions can be treated like those from any other cause (antibiotic ointment/cycloplegic/pad etc as required). The lenses should be left out for 24 hours to allow the epithelium to heal. Red eye Contact lens wearers suffer from all the normal diseases that cause red eyes but they also have a much higher incidence of corneal abrasions and corneal infections. Therefore beware of a contact lens wearer with a red eye. Examine the patient very carefully for any evidence of a corneal ulcer. Patients with signs of corneal infection such as decreased vision, marked redness, and white or cloudy areas (Fig. 2) in the cornea need immediate referral. Sterile immune ulcers are common in contact lens wearers but patients should always be referred to exclude the presence of disease. Acanthomoebic keratitis is a rare but sight-threatening corneal infection that most commonly affects patients who make up their own saline solutions or use tap water to rinse their lenses. Never encourage homemade solutions and don’t give patients bags of normal saline. Dry eyes Contact lenses can exacerbate or precipitate the symptoms of dry eye. Many wearers need occasional tear supplements, especially if they work in smoky or air-conditioned environments. Prescribe any of the low viscosity tear supplements such as Tears Plus™, Poly-Tears™ or Tears Naturale™. The ‘single use’ unpreserved tear supplements such as Refresh are very useful as they do not expire and a few vials can be stored in a variety of locations in case they are needed (home, car, work etc). Itchy eyes Some patients develop hypersensitivity reactions to contact lens solutions, complaining of redness and irritation shortly after lens insertion. Advise such patients to try rinsing off solutions more thoroughly or trying a new cleaning regime. Advice on cleaning solutions can be obtained from optometrists, ophthalmologists and pharmacists. Displacement of lenses Fig. 3. Recentering a contact lens. This cosmetic contact lens has decentred upward. The patient has been asked to look downward and a dry finger is placed on the lens. The patient will now be asked to slowly look up until their cornea lies directly beneath the lens. Most contact lenses decentre from time to time. Occasionally they become completely displaced from the cornea. Patients present in pain and distress and many need reassurance that contact lenses never go around behind the eye. Wash your hands then instil a drop of local anaesthetic; anaesthesia makes it much easier to examine the patient and reposition the lens. First ascertain that there is actually a lens on the eye. It is quite common for patients to believe that their lens is in the eye when in fact it was lost during or following insertion, especially if there is an epithelial abrasion causing pain. If the lens is present but displaced it will almost always be found hidden underneath the top eyelid or sitting laterally but still within the palpebral aperture. Ask the patient to look down. Pull the upper lid up and away from the globe and shine a torch or ophthalmoscope onto the globe and into the upper fornix. Contact lenses are difficult to find; try shining the light from the side to see if you can catch a reflection off the surface. Once you see the lens instruct the patient to look directly away from the position of the lens, usually they have to look down and nasalward. Place your finger gently on the lens (Fig. 3) and then ask the patient to slowly look towards your finger. You need to exert just enough pressure to stabilise the lens while the patient slowly rotates their cornea to the site of the displaced lens. The cornea has a different curvature to the sclera, and once the lens is sitting once again on the cornea it will usually centre automatically and stay in the correct place. You may need to attempt the manoeuvre several times and it can help, especially with soft lenses, to dry your finger on a clean gauze pad between attempts. If you fail you can also try to simply nudge the lens back onto the cornea. Once the lens is back in position ask the patient to remove it, as there are often a few epithelial abrasions as a result of your manoeuvring. The cornea needs 24 hours to heal. Fig. 4. Technique for mobilising a stuck contact lens. The lower lid is being pressed against the edge of the lens and a bubble of air can be seen entering beneath the lens. Stuck lenses Patients occasionally experience difficulty removing their lenses, usually because a vacuum has developed beneath the lens. Such lenses may be centred or decentred. Instilling local anaesthetic may enable the patient to remove the lens, otherwise try pushing gently on the edge of the lens to break the vacuum. The latter is best achieved by pushing the lid margin directly backward onto the lens with your finger (Fig. 4). If all else fails, lever the lens gently off the eye with a small surgical instrument. Acute overwear Occasionally, usually after festivities or excess alcohol, patients leave their contact lenses in when retiring to bed. Their corneas become hypoxic and oedematous and they are awoken by severe pain several hours later. Those patients who are  able to remove their lenses at the time often visit their own GP the following day, still in some discomfort. Some patients however are in so much pain that they cannot remove the contacts and present to After Hours surgeries in the early hours of the morning. They are well aware of the diagnosis. Instilling a drop of local anaesthetic allows the patient to remove their lenses. Following removal, instillation of a cycloplegic such as cyclopentolate 1% and an ophthalmic ointment are reasonable palliative measures. Padding is normally of little use, the corneal epithelium is usually intact and the pain is due to oedema of the corneal stroma. Give simple oral analgesia and consider a hypnosedative. Broken lenses Very occasionally hard contact lenses break due to trauma. The small shards are quite sharp and can damage the cornea. Remove any obvious pieces and refer the patient to their optometrist or ophthalmologist for review. Tips Fluorescein and contact lenses NEVER instil fluorescein into an eye with a contact lens in situ. Some soft lenses absorb the dye and become permanently stained and unusable. Storing contact lenses If for some reason you need to store a patient's contact lenses, a specimen pottle with a few mils of saline makes an ideal temporary container. Finding lenses lost on the floor If a patient drops a lens onto your floor ask everyone to remain still. Many lenses are finally found when someone stands on them. Be careful to check the patient's face and clothes, many dropped lenses never reach the floor. Otherwise, for lenses on the floor, other than getting down on one's hands and knees, a useful trick is to darken the room and then scan around with your ophthalmoscope looking for the lens's small but quite bright reflection. When to refer Patients with chronic problems such as discomfort, dryness, redness etc should see the practitioner who fitted the lenses. Those with any sign of infection should be immediately referred to an ophthalmologist, bypassing their optometrist. DO NOT instil any antibiotic into these eyes as it may interfere with the collection of tissue for microbiology. © GP Eyes - Dr Malcolm McKellar 2011