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Eyedrops are medical products in drop form that are instilled into the eyes, for example to treat conjunctivitis, dry eyes, or glaucoma. Some 60 years ago, preservatives were added to these products. The aim was to ensure optimum safety for patients, by preventing any contamination by bacteria or molds after a multidose vial is first opened. The water present in ophthalmic preparations makes them sensitive to microbial contamination. Benzalkonium chloride (BAK) is the preservative most widely used in eyedrops to ensure their sterility.
An important advance in the pharmaceutical industry.1 25 years ago, ophthalmologists discovered the harmful effects of preservatives. Several studies suggested that their use in eyedrops was linked to various inflammatory reactions of the eye surface.1 In most patients, they caused mild temporary reactions, but these could develop into chronic damage to the eye surface in the case of repeated treatment, high dose or lifelong treatment. These adverse effects appear promptly, but are felt only several months, or even several years after the start of treatment.
The use of preservatives in ophthalmology is a public health issue, because in treating a known disorder, patients worsen their condition, either by developing a new disorder or by aggravating their existing one.
The adverse effects firstly involve the conjunctiva and the cornea. In persons being treated with preserved eyedrops, 48% reported pain or discomfort on instillation (against 19% of persons treated with preservative-free eyedrops), 42% reported a sensation of a foreign body (against 15%) and 35% reported eye dryness (against 16% with no preservative).2
Quality of life and well-being can thus often be impacted by the harmful effects of preservatives on the eye surface.
Secondly, the preservatives affect the deeper structures of the eye such as the crystalline lens or the trabecular meshwork, and even deeper ones such as the retina.3
Patients being treated for glaucoma, for example, are especially concerned, because preservatives can cause inflammation.4 Glaucoma most often affects persons aged over 45, and is generally caused by an increase in the pressure inside the eye, which can damage the optic nerve. The most frequent treatment is daily instillation of an ocular hypotensive agent. If it contains a preservative, there is a risk of red eyes and inflammation of the eye surface. In a study conducted in 2016, 95% of patients who had previously been using preserved eyedrops were satisfied or very satisfied with the tolerability of their new preservative-free treatment after 3 months instillation.5
In some cases, surgery can be offered to patients with glaucoma to favor the elimination of aqueous humor. For such surgery to succeed, it is important to have a healthy conjunctiva. However, it can be inflamed through year-long use of preserved eyedrops This can jeopardize the surgery, which will accentuate the already existing inflammation. Fewer surgical complications have been observed in patients who were treated with preservative-free eyedrops.6 Chronic disorders such as dry eye syndrome can also occur with glaucoma, owing to the toxicity of the preservatives.
It is therefore preferable to avoid eyedrops containing preservatives, especially in the case of chronic treatment such as for glaucoma or dry eye syndrome (diminished quality and quantity of tears), or eye allergy; (e.g. allergic conjunctivitis), or if eye surgery is planned (cataract, glaucoma, refractive surgery, etc.).
If you wear contact lenses, preserved eyedrops can damage them. It is advisable to use preservative-free eyedrops.
In addition, contact lens wearers tend to have a more fragile eye surface than the general population.7 They often use artificial tears to hydrate and lubricate their eye surface. They can thus greatly benefit from using preservative-free eyedrops.
Given the abundance of preserved eyecare products on the market, you may surely wonder whether they perform better than non-preserved solutions. Studies have shown that preservative-free eyedrops have the same effectiveness as preserved ones.
In addition, the benefits of non-preserved eyedrops include
Preservative-free eyedrops are especially recommended in the case of chronic treatment (glaucoma, dry eye), and when the eye surface disorder is inflammatory (e.g. allergy).8
Many studies have reported different symptoms between preserved and non-preserved eyedrops. In one study on 9658 patients:2
Leaders with the first preservative-free multidose vial, ABAK®, Laboratoires Théa are pioneering the development of preservative-free ophthalmic eyedrops that favor better ocular well-being for patients. The ABAK® vial allows a treatment of up to three months after opening, guaranteeing maximum protection against contamination once the vial has been opened. Théa’s watchword: safety. Safety made possible through the development over many years of preservative-free ophthalmic products for the eye surface.