Allergic conjunctivitis is a common disease of the ocular surface. Most of the time though not always it is a consequence of allergic triggering factors. There are five main clinical forms of allergic conjunctivitis.
The most common form is acute and seasonal conjunctivitis (SAC). It is often associated with rhinitis and affects mainly children and young adults. 14.6% of European children aged 13 to 14 are affected. The benign form is more common in countries of high economic level.
Perennial allergic conjunctivitis (PAC) is another benign form of allergic conjunctivitis. It affects mostly young adults living in towns.
The severe forms are much less common: the least rare is vernal keratoconjunctivitis (VKC). It accounts for 3.2 per 10,000 individuals in Western Europe. Atopic keratoconjunctivitis (AKC) and giant papillary conjunctivitis (GPC) are close and rare entities.
Signs and symptoms of allergic conjunctivitis are largely dominated by ocular itching, to such an extent that some consider this symptom as mandatory to assess the diagnosis. Moreover patients often complain of watery eyes or red eyes. These symptoms are shared by all the clinical forms of allergic conjunctivitis but they are mostly consistent with benign forms (SAC and PAC). The diagnosis is easily made by the general practitioner or the paediatrician. When the itching is intense, bordering on eye pain, when secretions appear, with eyes glued in the morning, when light is poorly supported (photophobia), it is necessary to refer the patient to the ophthalmologist. In such cases the physician can observe swellings scattered in the inside of the eyelid (known as giant papillae on the everted tarsal conjunctiva) or inflammation of the corneal limbus (the junction area between the white and the coloured part of the eye), which is an area rich with inflammatory cells. The involvement of cornea (the lens which covers the coloured part of the eye) is called keratitis: it is evoked when the patient complains of photophobia or vision trouble. These medical complications can also occur in the 4th clinical form of allergic conjunctivitis which is called atopic keratoconjunctivitis (AKC).
The 5th clinical form, giant papillary conjunctivitis is a close clinical form of the 2 previous forms VKC and AKC). It is a rare consequence concerning wearers of soft contact lenses.