See the separate related article on Contact Lenses (Types and Care).
Contact lenses (CLs) are now worn by millions of people worldwide and by about 1.65 million people in the UK. The problems associated with wearing them are well recognised. The wearing of CLs causes changes in the cornea in terms of structure, turnover, tear production and oxygen and carbon dioxide levels. These changes in themselves can produce problems and may also exacerbate pre-existing conditions.
CL-related problems may also be associated with the type of lens used (eg, soft, rigid, gas-permeable), the frequency with which the lenses are changed, the cleaning systems used for the lenses as well as wearer-related factors. The range of problems which may occur includes minor problems, from inadequate rinsing to loss of vision as a result of microbial keratitis.
Approximately 6% of CL wearers per year will develop some problem associated with their use, although the majority of these problems will be fairly minor. A recent study has found that they account for 9.1% of the referrals into the eye casualty unit.
- Dry eye.
- Atopic or allergic conjunctivitis.
- Poor lens care or inexperienced CL user.
- Prolonged lens wear including overnight wear.
- Trauma or surgery.
- Increasing age.
- Systemic disease.
Patients presenting with a history of pain and irritation or watering of the eye and a red eye should elicit a high degree of suspicion.
A useful rule of thumb is:
- Does the eye look good?
- Does the eye feel good?
- Is the vision out of that eye normal?
A negative answer to any of these should prompt removal of the CL and assessment for a possible complication. The problems associated with wearing CLs may be:
- Related to the CL itself.
- Associated with conjunctival problems.
- Associated with corneal problems.
Problems with the lens itself
- Poor lens fit. Both tight and loose lens fitting can cause damage. Tight lenses typically feel comfortable initially and then become increasingly uncomfortable over a period of hours. With continued use, tight lens syndrome can develop (see under 'Corneal problems', below). Loose lenses result in lens decentration: the patient complains of an increased awareness of the lens and varying vision with each blink.
- Poor lens care. Failure to clean the lenses properly may lead to the accumulation of protein and lipid deposits on the lens. These can cause irritation of the cornea and impaired visual acuity. Bacteria, protozoa and fungi can form a film over the lens and the fungal filaments may invade the lens itself. Deposits on, or damage to, the lens surface may also occur due to other substances which they may come into contact with, such as hairspray, make-up, smoke and hand cream. It is important to ensure that the patient is using the lenses correctly so as to prevent future deposit formation.
- Lens damage. Damage or spoilage of the CL is more common with soft lenses than with rigid gas-permeable (RGP) lenses. Damage may occur in the form of tears, cracks and chips. These may cause local irritation of the cornea. The lens is then also at greater risk of pathogen colonisation, giving rise to conjunctivitis or keratitis. Warping of the lens may occur if it is squeezed excessively during the cleaning process or if kept in conditions that are too warm (eg, rinsing in hot water or keeping them in a case on the car dashboard). Warping of the lens may result in induced warping of the cornea and difficulty in correcting a refractive error, which can take months to resolve.
- Lens drying. An appearance of 'staring' or reduced blink rate is common in CL wearers and may result in drying of the lens with deposit formation on its surface. It may also give rise to corneal hypoxia (see under 'Corneal problems', below).
- Allergic conjunctivitis.Arises due to sensitivity to thiomersal, a preservative used in CL care solutions. This presents with redness, burning and itching which is worst on lens insertion and reduces over time. But diagnosis is tricky and the conjunctivitis may only gradually appear days or months after initial exposure. There will be evidence of perilimbal injection (ie redness just around the cornea). Treatment is avoidance of thiomersal; advise patients to visit their CL provider for alternative lens care solutions.
- Giant papillary conjunctivitis.This allergic condition arises as a direct consequence of the lens itself and presents as intolerance to the lens associated with irritation and redness of the eye. On closer inspection, large papillae (>3.0 mm) may be seen in the upper tarsal conjunctiva. These are thought to be due to chronic irritation and mediated by both immune and mechanical means. Treatment consists of removing the lens until the condition has resolved, and improving care/fit of lenses if necessary. Topical mast cell stabilisers (eg, sodium cromoglicate) may be used, but preserved drops should not be instilled with soft lenses.
- Toxic conjunctivitis.May occur as a result of the cleaning solutions used for the lens due to absorption into the lens of the preservatives. This is more of a problem when using soft lenses. The lenses can also become coated with other substances which may be on the hand of the wearer when inserting the lens - eg, perfume or hand cream. The eye becomes red and may develop corneal abrasions ± fine infiltrates and superior limbic keratoconjunctivitis. Once again, treatment is by removal of the lens until the condition has resolved. If severe, ocular lubricants may be required together with a short course of topical steroids.
- Superficial punctate keratitis (SPK). This is the most common problem associated with CL wear and may occur as a result of dry eye. It is then usually seen in the lower half of the cornea as little scattered fluorescein staining dots when the cornea is viewed with the cobalt blue light of a slit lamp. The dry eye may be aggravated by concurrent factors such as smoke, dust, air-conditioned rooms and medication (eg, antihistamines, diuretics and psychotropic agents). SPK may also arise in association with any of the conditions described below.
- Mechanical injury. Due to cracked or damaged lenses or trauma when inserting or removing the lens. It can also arise from the friction of accumulated debris on the lens.
- Tight lens syndrome (3 o'clock and 9 o'clock staining).Seen mainly with RGP lenses and especially if lenses are worn overnight: the lens does not move on blinking and appears to be stuck on the cornea. Generalised corneal oedema is seen with particular damage seen at 3 o'clock and 9 o'clock positions where there may be epithelial erosions and neovascularisation. It is aggravated by decreased blink rate and low-riding rigid CLs, resulting in inadequate lid closure and poor condition of the patient's lids/meibomian glands/tear layers, causing localised corneal desiccation. It is relieved by improving the fit of the lens together with use of lubricants.
- Corneal hypoxia. Due to decreased oxygen diffusion produced by the lens. This is uncommon these days due to the quality of the lenses but can occur when individuals do not replace lenses or use them beyond the recommended time. In the acute stage, this may produce corneal ulceration and pain. Chronic hypoxia may be asymptomatic but results in changes in corneal structure and in neovascularisation. This latter feature is more common in hydrogel lens wearers but may occur with RGP lenses too. Superficial neovascularisation (1-2 mm) may be monitored but deeper growth can result in intracorneal bleeding and impaired vision. Treatment in an eye unit is by removal of the lens and treating the corneal ulcer with topical antibiotics and cycloplegic agents. Topical steroids may also be required if severe. Topical and subconjunctival bevacizumab in combination with superficial keratectomy may have a role. Patients should be fitted with RGP lenses if they wish to continue wearing CLs and should be educated with regard to healthy use.
- CL-induced red eye (CLARE), or CL-associated infiltrative keratitis. Arises as a result of extended CL wear and is associated with an acute onset of red eye associated with infiltrates. It may resemble microbial keratitis (refer if unsure). Treat by removing the lens until complete resolution has occurred; treat any associated blepharitis. Recurrence is common if extended use lenses are worn once more.
- Microbial keratitis:[12, 13, 14]
- Essence: this is the most severe (and the most common) complication of CL use and may result in impaired vision.With daily CL wear, the incidence is about 2-4 per 10,000 wearers per year. It is more common in soft lens users wearing their lenses on an extended basis, when it occurs in 20 per 10,000 per year.
- Aetiology: it is most commonly caused by infection with Pseudomonas spp. and Klebsiella spp., although other bacteria and fungi may also produce the problem. Notably, the organism Acanthamoeba spp. can cause a rare but potentially devastating sight-threatening keratitis. Suspect this in the patient who swims in pools.
- Presentation: the patient will present with pain, watery eyes, irritation, photophobia ± red eye; this is usually unilateral. Acanthamoeba keratitis may initially present with a dendritic-type ulcer and be misdiagnosed as herpes simplex: any dendritic keratitis in a CL wearer should be assumed to be caused by Acanthamoeba spp. until proved otherwise.
- Management: patients should be referred as an emergency. The lenses and cleaning solution should accompany the patient and will need to be cultured. A corneal scrape may be used to culture the organism. Intensive antibiotics ± hospital admission are required. Topical antibiotics used include vancomycin, gentamicin, tobramycin or a fluoroquinolone. Acanthamoeba spp. infection requires specialised treatment with combinations of anti-amoebic agents.
- Prognosis: corneal scarring is a common complication and some patients will require corneal grafts as a result.
Herpes and adenoviral infections can occur during CL wear, although no association has been found between the two. Consider discarding CLs that have been worn during an active viral infection and dispensing new ones after the infection has resolved.
HIV transmission and CLs
Although HIV has been isolated from ocular tissues, tears and soft CLs used by patients with AIDS, there are no documented cases of HIV transmission through contaminated tears or CLs.
Most problems associated with CLs are not serious and will resolve if the lens is removed for a period of time. Any CL wearer who presents with irritation of the eye should have:
- Full history, especially with respect to previous ophthalmic history, type of lens, use of lens, type of cleaning solutions, other medications, and history of allergy or atopy.
- Examination of the eye with ophthalmoscope ± with a slit lamp, after staining. Examination of the internal surface of eyelids for papilla formation.
- Advice regarding removal of the lens until the problem has resolved, followed by a repeat visit to an optometrist to check fit/type/suitability of the lens.
- Treat corneal abrasions with topical antibiotics and cycloplegic agents - but only if you are sure this is a true abrasion and not microbial keratitis; if in doubt, refer.
- Most problems caused by CLs will make a full recovery following removal of the lens.
- Neovascularisation and microbial keratitis can cause permanent visual impairment if not treated quickly and adequately.
It has been shown that about 80% of CL wearers are unaware of the risks associated with wear and specifically with poor CL hygiene. This has prompted some to suggest obtaining a formal consent before CLs are prescribed, with a clear explanation of the care and the risks.
Further reading and references
; Acanthamoeba keratitis: diagnosis and treatment update 2009. Am J Ophthalmol. 2009 Oct148(4):487-499.e2. Epub 2009 Aug 5.
; Contact lenses and associated anterior segment disorders: dry eye disease, Immunol Allergy Clin North Am. 2008 Feb28(1):105-17, vi-vii.
; Informed consent and medical devices: the case of the contact lens. Br J Ophthalmol. 2005 Jun89(6):782-3.
; Contact lens referrals to Hull Royal Infirmary Ophthalmic A&E Unit. Cont Lens Anterior Eye. 2008 Jul 1.
; Microbial contamination of contact lenses, lens care solutions, and their Eye Contact Lens. 2010 Mar36(2):116-29.
; The incidence of contact lens-related microbial keratitis in Australia. Ophthalmology. 2008 Oct115(10):1655-62. Epub 2008 Jun 5.
; Risk factors for nonulcerative contact lens complications in an ophthalmic Ophthalmology. 2009 Mar116(3):385-92. Epub 2009 Jan 22.
; Contact lens complications. Ophthalmol Clin North Am. 2003 Sep
; Allergy and contact lenses. Chem Immunol Allergy. 200792:166-75.
; College of Optometrists, October 2010
; American Optometric Association, 2006
; College of Optometrists, July 2013
; Updates in Acanthamoeba keratitis. Eye Contact Lens. 2007 Jan33(1):1-8.
; College of Optometrists, February 2012
; Contact lens-related microbial keratitis: what can epidemiologic studies tell us? Eye Contact Lens. 2003 Jan29(1 Suppl):S85-9
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