KERATOCONUS CAUSES AND RISK FACTORS AMBLYOPIA Keratoconus is an inherited condition which affects • Genetics. Up to 50% of family members of patients theAmblyopia, cornea, the commonly transparent known front as surface lazy eye, of is the the eye. most with keratoconus will have at least subtle signs of Incommon keratoconus, cause the of poornormally vision round in children. cornea becomes early keratoconus. thinned,Amblyopia distorted occurs and because irregular, the withpart itsof theshape brain that • Down Syndrome: keratoconus is more common in becomingdeals with increasingly vision for that cone-like. eye has failedInitial tosymptoms develop people with down syndrome. cannormally. be slight blurring or distortion of vision with • Association with certain conditions: keratoconus increased sensitivity to glare and light. As the condition is linked to variety of diseases, including eczema, progresses,The vision centre vision in may the become brain is constantlymore distorted. developing during the first 7-8 years of a child’s life. If the vision is hay fever and asthma. Theinterfered abnormal with shape in any of way, the thecornea brain prevents will start the to preferlight enteringone eye theover eye the from other, being and focusedthe vision correctly in the other on the retina,eye will the suffer. light-sensitive To reverse membrane the process which and enablescorrect DEVELOPMENT OF sight.the vision This resultsin the poor in distortion eye, it is ofnecessary vision. Because to make of the the KERATOCONUS cornea’sbrain use irregular this eye shape,again. patients with keratoconus are usually very near-sighted and have a high degree of In its earliest stages, keratoconus causes slight astigmatism that is not correctable with glasses. blurring and distortion of vision and increased sensitivity to glare and light. These symptoms usually WHAT CAUSES AMBLYOPIA? appear during the late teens or early twenties. SIGNS AND SYMPTOMS Keratoconus may progress for10-20 years before 1. The most common cause of amblyopia is poor slowing in its development. Each eye may be affected • Near-sightedness. KERATOCONUS focusing due to: differently; one eye may have very poor vision while the • Astigmatism. • Hyperopia (far-sightedness). other eye retains perfect vision. In keratoconus, the shape of the •• BlurredMyopia vision (near-sightedness). - even when wearing contact lenses or glasses. normally round cornea becomes • Astigmatism (which is an imperfection in the As keratoconus progresses, the cornea bulges more • Glare at night. cone-like. curvature of the eye’s cornea) that can distort and the vision may become more distorted. Because • Eye rubbing. vision for both near and far objects. the keratoconic cornea is weaker than the normal • Light sensitivity. cornea, it is vulnerable to damage from minor trauma. • Frequent prescription changes in glasses and 2. Strabismus is sometimes a cause of amblyopia. For this reason, people with keratoconus should not contact lenses. Commonly known as a squint or turning-eye, participate in contact sports. strabismus is where the eyes do not look in the same direction. If, for example, one eye in particular turns in, it is likely this eye will become amblyopic.

3. Another cause of amblyopia could be a disruption to the passage of light into the eye, such as: • A scar on the cornea (the surface of the eye), • A cataract (an opaque lens in the eye). • A very droopy eyelid. HYDROPS TREATMENT - SURGICAL

In a small number of cases, hydrops may occur. This PROCEDURES is where there is swelling in the cornea, causing a sudden and significant decrease in vision. This occurs CORNEAL COLLAGEN CROSS-LINKING when the stretching of the cornea causes a tiny split to Most people with keratoconus develop slowly worse develop in its inside surface. The swelling may last for vision for a few years, and then, usually in their 20’s or weeks or months as the crack heals and is gradually 30’s, the cornea stops changing and vision stabilises. 8 St Marks Rd, Remuera replaced by scar tissue. If this sudden swelling There is a treatment available - corneal collagen cross- does occur, your doctor can prescribe eyedrops for linking - which will make the cornea stronger and halt temporary relief. However, there are no medicines that progression at an earlier stage. can prevent the disorder from progressing. Cross-linking takes about an hour, and is carried out under local anaesthetic in an operating theatre. Often the scarring causes the vision to be somewhat To be a candidate for this, the shape of the cornea worse after an attack of hydrops. Sometimes, however, must be shown to be still changing. If the cornea has the scarring may improve the shape of the cornea, stretched too much already, it may become too thin enhancing vision. The cornea may become very thin, for the treatment. Because of this the treatment is best Oasis Surgical & Dry Eye Clinic, but it is very unlikely to spontaneously rupture. carried out in the early stages of keratoconus, and may 2 MacMurray Rd, Remuera prevent a person from progressing to more severe vision loss. TREATMENT - GLASSES AND CONTACT LENSES CORNEAL IMPLANTS Some patients may be suitable for corneal implants, Treatment of keratoconus depends on the severity of which work by flattening the steep part of the cornea the condition. Initially, glasses or soft contact lenses to reduce the vision distortion caused by keratoconus. 3 Fred Thomas Dr, Takapuna should be successful in correcting the myopia (near- The result attained from this will depend on the degree sightedness) and astigmatism. of keratoconus being treated. As the disorder progresses and the cornea continues For severe keratoconus, corneal transplantation (or to thin and change shape, hard contact lenses can graft surgery) may be the only option. This procedure be prescribed to correct vision. In most cases this is is usually performed under general anaesthetic. The adequate, but the contact lenses must be carefully keratoconic cornea is removed and a donor cornea fitted by an optometrist. Frequent check-ups and lens (human tissue provided by the National Eye Bank after changes may also be needed to achieve and maintain careful quality screening) is then sutured in its place. A good vision. A government subsidy may be available to prolonged period of post-operative care is required to Ormiston Medical Clinic, 221 Ormiston Rd help with the costs of contact lens wear. ensure the graft remains healthy. Contact lens wear in keratoconus does not alter the progression of the disease or cure the condition. It merely gives improved vision while the lenses are being worn. When good vision can no longer be attained with contact lenses because of corneal Phone 09 529 2480 or 0800 25 53 93 scarring or intolerance to contact lens wear, surgery Email: [email protected] may be necessary. www.aucklandeye.co.nz