The effect of sodium cromoglycate eyedrops compared to the effect of terfenadine on acute symptoms of seasonal allergic conjunctivitis

Role of antihistamines in ocular allergy

Although H(1) antihistamines are commonly used to treat allergic disorders and have demonstrated efficacy in allergic rhinoconjunctivitis, data on the effects of these agents specifically on ocular symptoms are limited. Oral H(1) antihistamines inhibit some symptoms of pruritus and erythema in laboratory models and have been shown to be superior to placebo for relief of symptoms in clinical trials. Eye drops typically provide faster relief of ocular symptoms than oral agents, and combination therapy with a topical agent and an oral agent has been found to be superior to the oral agent alone. In general, oral H(1) antihistamines have been considered superior to intranasal corticosteroids for relief of ocular symptoms, but some studies have shown equal efficacy for these agents, or even superior efficacy for intranasal corticosteroids.

Ocular allergy guidelines: a practical treatment algorithm

The treatment of ocular allergy requires a better understanding of the spectrum of clinical disorders involving various components of the immune system, and of interactions at the conjunctival surface. The immune response focuses primarily on the different levels of activity of Th2 lymphocytes and various other immune cells associated with allergic disorders, including mast cells, eosinophils, fibroblasts, and epithelial and endothelial cells. Ocular allergic disorders include seasonal allergic conjunctivitis (SAC), perennial allergic conjunctivitis (PAC), vernal keratoconjunctivitis (VKC), giant papillary conjunctivitis (GPC) and atopic keratoconjunctivitis (AKC), which, through immunopathological and molecular immunological techniques, can all be better appreciated as being part of a larger spectrum of an atopic disease state. In SAC, pathological changes, such as increased mast-cell activation, the presence of migratory inflammatory cells, and early signs of cellular activation at the molecular level, are minimal. In PAC, these changes are more pronounced in line with the increased duration of allergenic stimulation. In more chronic forms of allergic conjunctivitis, such as VKC in children and AKC in adults, the following changes are evident: a persistent state of mast cell, eosinophil and lymphocyte activation; noted switching from connective-tissue to mucosal-type mast cells; increased involvement of corneal pathology; and follicular development and fibrosis. The treatment of acute and more chronic forms of allergic conjunctivitis has focused in the past on symptomatic relief of symptoms, but with a better understanding of the mechanisms involved we can now provide interventional therapeutic strategies and symptomatic relief. Our advances in the basic understanding of these conditions are providing the foundation for guidelines that improve the ocular health of patients with ocular allergies.

Comparative therapeutic studies with Tilavist

Comparative clinical trials which include known therapies as well as placebos are essential in constructing a solid basis from which to 'launch' any new drug. This applies especially to eye drops for treatment of seasonal allergic conjunctivitis, where the symptomatology, already dependent on the vagaries of the natural pollen challenge season, is further influenced by a positive washing action of the placebo eye drops. Tilavist (2% nedocromil sodium ophthalmic solution) has therefore been compared with sodium cromoglycate eye drops and non-sedating antihistamine tablets, both mainstays in the treatment of seasonal allergy, in a series of double-masked, placebo-controlled, mainly multicentre studies. Nedocromil sodium, twice or four times daily, proved as effective overall as sodium cromoglycate (2% or 4% four times daily) in three seasonal trials, and was the more effective treatment in a study of patients with vernal keratoconjunctivitis. Its efficacy was most evident during peak periods of pollen challenge, when neither placebo nor sodium cromoglycate eye drops controlled breakthrough symptoms. Three further seasonal studies showed nedocromil sodium eye drops to be as effective as standard oral doses of astemizole and terfenadine, whilst a faster onset of action than terfenadine was reported in one multicentre study.

Topical sodium cromoglycate (Opticrom) relieves ongoing symptoms of allergic conjunctivitis within 2 minutes

Twelve patients with seasonal allergic conjunctivitis caused by either birch or timothy grass pollen were challenged out of season in both eyes, with the relevant allergen. Itching, redness, swelling, and tearing were assessed on a 0-3 scale. When a positive reaction, i.e., at least 4 points, had occurred in both eyes, one drop of 2% sodium cromoglycate was administered to one eye and one drop of placebo to the other eye in each patient, in a double-blind, randomized fashion. Symptoms were then assessed after 2, 10, 30, and 60 min. Sodium cromoglycate was statistically better than placebo in reducing the symptoms at 2, 10, and 30 min after the treatment had been administered, showing that topical application of 2% sodium cromoglycate can quickly relieve ongoing symptoms of allergic inflammation in the eye.

Treatment of vernal keratoconjunctivitis a double-masked study

Thirty-one children aged five to 14 years with severe vernal keratoconjunctivitis (VKC) were enrolled in a double-masked study evaluating the efficacy of three ophthalmic preparations: cromolyn sodium (Opticrom) 2%, artificial tears and fluorometholone 0.1% (FML). These drugs were coded respectively as A, B, C, and dispensed in similar bottles. Both eyes were treated, and drug assignment was made at random. Objective assessment of the disease activity was done under slit lamp by two ophthalmologists according to a five-point scale. The results were tabulated and the chi-square test performed. Decoding of the drugs was done only after completion of the statistical analysis. FML was found effective with a statistically significant difference from the other two drugs, both after the first week on the initially assigned treatment (p = 0.05) and on completion of the treatment period according to protocol (p = 0.005). Although several patients improved under cromolyn sodium, there was no statistically significant difference between cromolyn sodium 2% and artificial tears. All the preparations were well tolerated. One patient developed bilateral allergic blepharitis when treated with FML during the study. Another patient who responded well to FML developed posterior subcapsular cataract while continuing treatment with corticosteroids a few months after completion of the study.