In general, soft contact lenses have more side effects than rigid lenses in the long term. The commonest complication of wearing modern contact lenses is losing them. Patients are well advised to have a pair of glasses at hand in case they have contact-lens-wearing problems or a lens is lost. More serious trouble can result from clumsy handling of the lens or leaving a rigid lens in the eye for too long a period. Such patients quite often present with severe pain in the eye, and examination reveals a partially healed corneal abrasion. This must be treated in the usual manner and the patient advised against wearing the lens again for several weeks, depending on the extent of the abrasion. The contact lenses themselves should also be examined by the patient's fitter to make sure that they are not faulty. Bearing in mind the troubles that can ensue when an abrasion becomes recurrent, the indications for wearing the lenses in the first place should be reconsidered.
The risk of infection by lens contamination or secondary to corneal abrasions is increased. Recently, Acanthamoeba keratitis has been described. This disease occurs more often in contact lens wearers.
Another sequel to wearing contact lenses, either rigid or soft, is the appearance of chronic inflammatory changes in the conjunctiva, often characterised by a papillary conjunctivitis. The resulting irritation and redness of the eyes can persist for some weeks after the wearing of the contact lenses ceases. Unfortunately, these symptoms can appear after wearing lenses successfully for some years and they tend to recur in spite of renewing or modifying the lenses. Some patients who tolerate contact lenses well can develop corneal changes after some years. Peripheral vascularisation can become evident and in neglected cases, there could be band degeneration of the cornea. Some contact-lens wearers complain of recurrent blurring of their vision and this could be due to an ill-fitting lens producing corneal epithelial oedema or simply to the excessive accumulation of mucus on the lens (Figure 10.1).
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