Eyes on glaucoma
It’s an insidious disorder that can creep up on you and suddenly rob you of your sight.
In conjunction with World Sight Day 2017’s theme of ‘Make Vision Count’, we look at glaucoma, the second leading cause of blindness in the world today.
GLAUCOMA is the name given to a group of eye conditions in which the main nerve to the eye (the optic nerve) is damaged, which leads to loss of vision.
This nerve carries information about what is being seen from the eye to the brain, and as it becomes damaged, vision is lost.
This results in misty and patchy vision, with eventual loss of central vision.
Glaucoma is becoming an increasingly prevalent cause of blindness as the world’s population ages. Statistics gathered by the World Health Organization (WHO) in 2002 showed that glaucoma was the second leading cause of blindness globally, after cataracts.
It has been estimated that by 2020, there will be approximately 80 million people with glaucoma, an increase of about 20 million from 2010.
Furthermore, it is thought that at present, over eight million people are blind due to glaucoma, a figure that is set to rise to over 11 million by 2020, unless improved screening and effective treatment strategies are in place.
There are four main types of glaucoma: primary open angle glaucoma, primary angle closure glaucoma, secondary glaucoma and developmental glaucoma.
Primary open angle glaucoma is the most common form of glaucoma in which the damage is usually caused by too much pressure within the eye (the intraocular pressure or IOP).
The reason for the rise in pressure is usually due to poor drainage of fluid out of the eye (which is required for the healthy function of the eye).
The increased pressure dam- ages the optic nerve by reducing the amount of blood that can get through the tiny blood vessels that supply the nerve, and also by compressing the nerve itself.
Detecting glaucoma
Early detection is key to managing and minimising the effects of glaucoma.
Hence, regular check-ups are recommended, especially as one grows older.
Some symptoms of glaucoma include hazy vision, pain in the eye and/or head, nausea or vomiting, the appearance of rainbow-coloured circles around bright lights, and in extreme cases, sudden loss of sight.
Although any vision that has been lost to glaucoma cannot be recovered, early diagnosis, careful monitoring and regular treatment allows the vast majority of glaucoma patients to retain useful sight for life.
The only way to know if you have glaucoma is to have your eyes checked at your local ophthalmologist.
The three common tests are:
● Ophthalmoscopy: Looking at the appearance of the main nerve in the eye (optic nerve).
● Tonometry: Measuring the pressure in the eye.
● Perimetry: Checking the field of vision.
Treating glaucoma
The majority of people with glaucoma will be treated with eye drops.
If eye drops are not successful in lowering eye pressure, laser or surgical treatment for glaucoma may be needed.
There are several challenges in the management of glaucoma.
Patients at a more advanced stage usually require more than one medication to control their IOP and keep their condition in check.
Multi-drug regimens for glaucoma pose several significant clinical challenges:
● It may negatively affect patient adherence (the extent to which a patient continues an agreed-on mode of treatment without close supervision).
● Reduced effectiveness due to the washing out of earlier medications when later medications are administered.
● Exposure to preservatives. Patient adherence to treatment is crucial for achieving good IOP control and slowing the progression of the disease.
Unfortunately, studies have demonstrated that adherence to treatment is often below optimal standard.
One study has shown that while 49% of patients using one medication for the treatment of glaucoma were compliant, only 32% of those using a combination of two medications were.
The more medications that are prescribed, the higher the chances of non-adherence.
Failure to achieve treatment outcomes due to poor adherence may lead to a perceived lack of efficacy and unnecessary changes in treatment regimen.
Unmet needs in glaucoma treatment
Factors associated with the medication itself, such as side effects and complicated regimens, are known to adversely affect adherence.
Glaucoma patients frequently develop side effects due to long-term exposure to preservatives in the eye drops (commonly benzalkonium chloride).
Although only trace amounts exist in each dose, prolonged exposure from multiple daily doses of eye drops from multiple glaucoma medications can lead to disorders of the surface of the cornea – the transparent layer that forms the front of the eye – such as as ocular surface disease (OSD) and increased risk of surgical failure.
OSD is a frequent complication caused and/or exacerbated by the chronic use of topical anti-glaucoma medication that contains preservatives.
Its overall prevalence ranges from 22%-78% depending on the method of clinical evaluation, with the number of preservative-containing eye drops positively correlating to ocular surface damage.
It stands to reason that the risk for developing OSD would be reduced if preservativecontaining eye drops were substituted with preservative-free eye drops.
The European Medicines Agency suggests avoiding preservatives in two groups of patients:
● Those who are unable to tolerate eye drops with preservatives.
● Those requiring longterm treatment.
A preservative-free fixed-combination anti-glaucoma formulation with once-aday dosing addresses the two major barriers that affect adherence in long-term glaucoma treatment:
● It eliminates side effects caused by prolonged exposure to preservatives.
● It simplifies the treatment regimen.
This article is courtesy of Santen Pharma Malaysia.