Therapeutic dilemmas in external ocular diseases.

Three ocular conditions continue to pose therapeutic dilemmas for the practising clinician. Acanthamoeba keratitis, which presents with ocular pain, redness, tearing, photophobia and lid oedema, should be considered in any chronic, progressive corneal ulceration that is unresponsive to conventional treatment. Although the best treatment for this infection has yet to be defined, surgery should be reserved for those patients with progressive destructive disease or corneal penetration. Topical antibiotics and oral ketoconazole may be beneficial, as may surgical debridement in conjunction with topical antibiotic-antifungal combinations. However, since more than two-thirds of reported cases involve contact lens wearers, patients should be instructed as to the importance of regular lens care regimens. Giant papillary conjunctivitis occurs more frequently in soft contact lens wearers than in those wearing hard lenses, but may also occur in association with ocular prostheses, cataract surgery and corneal transplants. Symptoms of increased lens awareness, mucus accumulation, itching and blurred vision occur. Stopping use of contact lenses usually improves or eliminates these irritating effects, but is not always practical. Thus, resolution or improvement of symptoms while the patient continues to wear contact lenses is desirable, making lens hygiene essential in treatment. Pharmacological treatment includes the use of topical corticosteroids and agents that stabilise mast cells, such as cromolyn sodium. The dry eye syndrome can occur alone or as a part of Sjögren's syndrome. The irritation, redness, and other symptoms associated with ocular dryness are usually treated by preparations of either mucomimetics, polyvinyl alcohol or cellulose derivatives, which provide moisture and prevent evaporation from the surface of the eye.