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AtopicKeratoconjunctivitis

It is a kind of allergic keratoconjunctivitis which affects people who are suffering from atopic dermatitis (rash).
It is always a bilateral form, and the symptoms include ocular itching, the sensation of an external body, excessive lacrimation and an abundant mucous excretion.
While the symptoms are similar to those of vernal keratoconjunctivitis, they usually show later, when people are between their 20s and 60s.
There is no association with the seasonal time. Typical are palpebral dermatitis and chronic blepharitis (that is, inflammation of the eyelid), with the thickening of the eyelids and the disfunction of Meibomio’s glands (they are glands which are located inside the eyelids and which synthesise one of the components of tears).
In the most severe cases, even the loss of sight can occur, due to the protracted inflammation of the cornea with peripheral neovessels and its cicatrization with a tissue which is no longer transparent, and therefore does not let light filter through it.
The therapy mainly consists in taking local and systemic corticosteroids.

Allergic keratoconjunctivitis resulting from medicines

Allergic reactions resulting from the contact with ophthalmic medicines are common and the medicines which mostly cause such reactions at the level of the conjunctiva and the palpebral skin of particularly sensitive people are neomycin (an antibiotic), atropine and phenylephrine (drugs which are used to expand the pupil and which have also an anti-inflammatory action), penicillin.
Obviously, the diagnosis should be assumed only if such substances have been used and must be confirmed by allergic tests, in any case.
Besides, the disappearance of the marks after the drug has been suspended will provide a further confirmation.
It’s really important to remember the name of the medicine in question, so that the doctor and the oculist could be warned in order to avoid a second contact.

Related articles: Allergic article 7 of 8.

Found in P.O. Professional Optometry April 2008

Vernal keratoconjunctivitis

Vernal keratoconjunctivitis is a severe chronical form of allergic conjunctivitis concerning the cornea and the conjunctiva. It mostly affects male children and young boys, and often subjects who already suffer from rash, asthma or hay fever.
It usually occurs in spring, probably due to vernal allergens, although some perennial forms exist, too.
It is generally possible to find out a positive anamnestic response -which can be personal or familiar- to the allergy, and in many cases it is possible to find out the specific allergen to which the patient is sensible, thanks to the anamnesis and the allergic cutaneous tests (for example, the acarus of the home dust with its faeces, represents a particularly common triggering allergen).
The main symptoms of keratoconjunctivitis are itching, intense photophobia and the presence of mucus filaments.
It is characterized by the presence of giant papillae, usually located on the superior tarsal conjunctiva.
Even the conjunctiva above the limbus can be affected by oedema and reddening.
The patient often complains about an intense itching.
Common symptoms are excessive lacrimation, the production of mucus, photophobia, inflammation and the sensation of an external body.
The classic palpebral mark of the vernal keratoconjunctivitis is represented by giant papillae in the superior tarsal conjunctiva, which the oculist can analyse overturning the eyelids.
These papillae significantly increase the mass of the superior eyelid and, consequently, the ptosis (that is, the lowering of the superior eyelid) is an additional typical mark.
The inflammation of the bulbar conjunctiva is variable: a knotty prominence can be found in the inferior fornix.
The keratopathy tipically starts with a superficial diffuse suffering of the cornea.
If the inflammation persists, after the release of inflammation mediators, the damage becomes more serious, causing evident epithelial defects.
Such lesions have been called shield ulcer for their shape. The longer the damage remains, greater is the possibility of a full-thickness ulceration and of a bacterial superimposition.
As far as the therapy is concerned, besides following the hygienical rules which we reminded of for allergic vernal conjunctivitis, the systemic therapy with cortisone is really useful to chronic patients.
For less severe cases, a systemic anti-histaminic therapy is advisable, whereas a systemic therapy is preferable to a topic one for the patients with severe allergic diseases, especially as it has a long-lasting effect and also because they sometimes become sensible to the preservatives contained in the ocular anti-histaminics on the market.
The use of monodoses keeps away the problem of the sensitivization to preservatives. As already mentioned, local therapy includes the use of corticosteroids and antihistaminics, especially in order to fight the sharpest marks of the inflammation, while the sodium cromoglicate, being a membrane stabiliser, should be given before the insorgence of the symptoms and during the whole period of the exposition to the antigen.
Even in this pathology, dual action medicines (e.g. Ketotifen fumarate, antihistaminic and membrane stabiliser) can be used both for the prevention and during the chronic periods with excellent results.
One of the most effective treatments against vernal keratoconjunctivitis is that of reducing the exposition to antigens, therefore it is advisable for the patients to move where temperatures are cooler and less allergens are present in the air.
Surgical therapy is not frequent, but it may happen that the presence of huge papillae under the eyelid could cause the sensation of external bodies or ptosis.
The combined excision of the tarsal bones and the conjunctiva, together with criotherapy (application of a probe that freezes and so destroys the surrounding tissues) can have positive effects, but only for a brief period.
Support therapy may be cold water -which stops the allergic reaction-, a correct periocular hygiene -accomplished through specific products- and dark sunglasses.

Related article: Allergies Article 6 of 8.

Found in P.O. Professional Optometry April 2008

Allergic conjunctivitis:
Finally,we cannot omit the allergic conjunctivitis. There are different types of ocular allergies; the most important ones are reported below.

Seasonal allergic conjunctivitis
It is often experienced by people affected by allergic rhinitis. They suffer from typical rhinitis symptoms such as ocular itching and lacrimation, often associated with sneezes and nasal congestions.
Clinical signs and symptoms are recurrent, often appearing and disappearing with the seasons, but sometimes they are perennial.
The allergens which are in the air, like pollen, mould, dust and animals’scurf, can trigger an immediate allergic reaction in the nose and in the conjunctiva.
We don’t know exactly how this happens, but it seems that the allergens dissolve themselves into the lacrimal film and react with specific lgE receptors which are linked to cells (mastcells and basophils) present into the conjunctiva.
The symptoms of ocular inflammation can vary during the period when symptomology is more evident. Sometimes the conjunctiva can appear as completely clear and silent, whereas other times swelling and redness can affect the eyelids and the conjunctiva.
However, even in the case of a silent conjunctiva, a deeper analysis may reveal a soft oedema of the bulbar conjunctiva and signs of inflammation of the tarsal one, both in the superior and the inferior part.
An increase of the mucus occur in the lacrimal film and in the inferior fornix. The symptomology is the result of the degranulation of the cells containing histamine or of other inflammation mediators.
It is useful to carry out regular checks on the environment, including air-conditioners and air-purifiers, filtrating systems, mattresses and lingerie, as well as to take care of the house cleaning, being particularly careful of the moquettes and the domestic animals, which sometimes must be kept away, especially in the most severe forms of allergy.
During the pollination period, it is necessary to avoid staying outdoors. The allergist can provide a helpful support for a reliable cutaneous test and for the spotting of the allergens causing the allergic conjunctivitis.
The treatment must include:

- environmental checks,

- a specific periocular hygiene,

- systemic antihistamines, when the exposition to the environmental allergen cannot be avoided; this should reduce the immediate effects of the histamine released by the mast cells, which starts losing granules after the contact with the allergen,

- antihistamines and topic corticosteroid therapy in low dosage and for a short period to deal with acute exacerbations,

- agents stabilizing the membrane of the macrophages for the periods of allergy known by the patients,

- medicines with the double function of antihistamine and membrane stabilizer, whose aim is to be used both for prevention and in the most acute and chronical phases with very good results.

We must remind that even immunotherapy and hyposensitisation often have positive results in reducing the severeness of nasal symptoms, but are not so effective for the ocular ones; therefore they are not useful to those patients who do not associate an allergic conjunctivitis with a nasal pathology.
The vasoconstrictors, if chronically used, can cause reddening as reaction, so they are unadvisable for the treatment of these pathologies.
The usage of contact lenses should be suspended during the symptomolgy period and started again at the end of the season.

Related article: allergies Article 5 of 8.

Found in P.O. Professional Optometry April 2008

Allergic bronchial asthma:
it is characterised by respiratory difficulties and hissing breathing, which occur in presence of the allergen to which one is sensible.

Allergic Rhinitis: it is marked by a lot of sneezes, watery nasal drainage (allergic rhinitis wets but does not spoil the handkerchief!) and blocked nose.
We might think of an allergy above all if we are in presence of a conjunctivitis.

Anaphylactic shock:
it is the most dangerous allergic reaction, since it can turn out to be fatal. It is characterised by a severe pressure fall and the obstruction of the respiratory tract as a consequence of a huge release of histamine into the circulation due to an allergic reaction.
The causes of all this can be food, medicine, as well as bee or wasp stings.

Atopic dermatitis:
it shows up especially during childhood, but can persist also in adulthood (it is more unlikely to break out in the adult subject). It concerns above all the face, the perioral area, the cervical and the area behind the knee.
The causes are various and not yet so clear.

Contact dermatitis:
it is characterised by erythema and small blisters that form in the exact point where the cute comes into contact with the allergen.
The most common form of it is caused by the nichel. There are also professional contact dermatitis (hairdressers, masons).

Urticaria/angiooedema:
Itchy pores are spread all over the body, sometimes associated with the swelling of the lips and the eyes.

Alimentary allergy:
it generally shows up as urticaria/angiooedema or, in the most severe cases, as anaphylaxisanafilassi after eating something.
The most allergenic types of food are: milk, eggs, wheat, crustaceans, fish, peanuts, tomatos.

Allergy to insect stings:
the most important form is the allergy to bees and wasps, as they can be responsible for an Anaphylactic shock.
This kind of allergy is more frequent in those who are professionally exposed (farmers, gardeners, bee-keepers), while it is less severe and less frequent in children.

Allergy to medicines:
it clinically manifests itself in different ways concerning not only the cute (urticaria, erythema), but also the respiratory system (asthma), or being sometimes responsible for hepatitis or nephritis.
The anti-inflammatories and the antibiotics (penicillin) are the most frequently involved molecules.

Related article: allergies article 4.

Found in P.O. Professional Optometry April 2008

The eye defences

The task of the eye defence is performed by the ocular surface, which is made up of the eyelids, the conjunctiva, the limbus, the cornea and the lacrimal film.
While the eyelids have principally a mechanical function of protection, the lacrimal film has a double function: a cleaning one -by increasing the tear production, it can move away whatever irritates the eye-, and a transport one, as it carries the antibodies produced by the plasma cells.
When the antigen comes up, the antibodies fix to it forming an antigen-antibody complex which activates another kind of cells widely spread in the ocular tissues: the mastcells.
These cells are present in the conjunctiva and it is calculated that there are around 50 million cells in the ocular tissues and the surroundings.
Each mastcell contains several hundred histamine grains which are released when its membrane receptors are stimulated by the presence of lgE.
The histamine triggers an inflammatory reaction which causes itching, the reddening of the eye and the swelling of tissues. Even the limbus shows anti-inflammatory features similar to the above-mentioned ones.

Which are the most common allergens?
The allergens that come into contact with the organism are various and of different nature. The most common ones are pollen, dust acari, domestic animals’ hair and mould.

Pollens
The pollens that can cause allergies are, by definition, the anemophilous ones, that is those which take advantage of the wind to fertilize other plants and that, therefore, differentiate from entomophilous ones, which use insects.
In spring, the bloom of several plants leads up to the appearance of typical symptoms (rhinitis, conjunctivitis, cough, dyspnea or breathlessness, asthma) during rather short and precise periods: it is really important for the allergologist to know when the first symptoms appeared in order to link them to a single plant, thanks to the results of the cutaneous allergologic tests.
Even because an allergic person’s tests usually show a polisensitization (that is, positivity to different allergens) which might lead to mistakes.

Dust acari
The Dermatophagoides pteronyssinus is the origin of the strongest allergen which causes asthma.
It well adapts to our home life, dwelling principally in our beds and feeding on human skin flakes which fall off with the physiological disquamation.
They are around 0.3 mm long and their faeces are approximately 20 thousandth of a millimetre, so they are likely to be deeply inhaled by the nose and the lungs.

Moulds
They belong to the fungus kingdom, are well adaptable and can grow anywhere there is enough oxygen and humidity.

Domestic animals
Nowadays they are one of the main causes of allergic reactions. It is not necessary the presence of the animal for the allergy to burst out. Indeed, the allergens remain in the air and in the home dust, in the case of cats even a lot of time after the animal has gone.

Food
Those who are allergic to pollen can experience, usually during pollination periods, the appearance of symptoms such as the oedema of the lips and of the mouth, together with an intense itching, after eating fruit or vegetables.
This fact can be explained with the presence of common allergens in the pollens and this kind of food: this disease is called Oral Allergy Sindrome and affects around the 25% of the pollinic patients.
The symptomatology can reach the oedema of the glottis, causing respiratory difficulty. Therefore, patients must prudentially avoid to eat suspicious food, which could lead to a croos-reaction with the pollens to which the subject is allergic.

In relation to the target of these substances, different types of allergy will occur.

Related article: Allergies Article 3 of 8.

Found in P.O. Professional Optometry April 2008