There is a lot of belief that glaucoma is the cause of every blindness. But the fact is that if you have been diagnosed with glaucoma, you can still maintain functional vision throughout your life.
What is glaucoma?
Glaucoma is an eye condition that progressively impairs vision by inflicting harm on the optic nerve. In a healthy eye, fluid drainage occurs through the drainage angle as more aqueous humor flows in, keeping the eye pressure stable. In glaucoma, the function of the drainage angle is impaired leading to a fluid build up, which in turn increases the eye pressure (called the intraocular pressure). According to the American Academy of Ophthalmology, “Glaucoma is a leading cause of blindness for people over 60 years old. But blindness from glaucoma can often be prevented with early treatment”. The National Eye Institute also states that vision loss from glaucoma can be averted with early prevention and treatment.
What are the two major types of Glaucoma?
Primary open angle glaucoma (POAG)- This is the most prevalent type of glaucoma. Here, there is an elevated resistance to the normal flow of aqueous humor, which causes a rise in intraocular pressure. In the initial phases, symptoms are usually absent, highlighting the importance of early detection. In fact, POAG does not cause any eye pain. However, as the disease progresses over time, it can result in vision loss and blindness if not treated. Clinical trial evidence shows that reducing intraocular pressure effectively halts the progression of the disease in both its early and advanced stages.
Primary closed angle glaucoma (PACG) – In PACG, angle closure is the primary concern, while elevated intraocular pressure (IOP) results from the angle closure. The most common mechanism here is pupillary block. This happens when the aqueous humor is unable to move freely from the posterior chamber, located behind the iris, to the anterior chamber, situated in front of the iris, because the lens is too close to the back surface of the iris. This variation in pressure leads to a forward displacement of the peripheral iris, thereby blocking the trabecular meshwork and contributing to an increase in intraocular pressure (IOP). Recent research studies has shown that the angle closure process can be halted in the early stages preventing PACG.
What are the contributing factors to vision loss in glaucoma?
There are factors that promote vision loss in glaucoma. And without the knowledge of these factors and what to do to forestall them, you will be caught unawares by this “silent thief of sight’. That is to say that if patients with Glaucoma are not diagnosed early, these factors progress over time leading to irreversible blindness. Some of the factors include;
1. Elevated intraocular pressure: This is a significant risk factor for glaucoma. Higher IOP in patients can lead to damage to the optic nerve, which is crucial for vision. Increased IOP has been attributed to higher disease risk by 10%. However, this factor can be modified and according to a series of randomized trials, treatments focused on decreasing baseline intraocular pressure (IOP) can be successful in preventing the development and progression of open-angle glaucoma (POAG). It is important to note that exercise like heavy weightlifting, intense resistance training, or activities that involve breath-holding (Valsalva maneuver) should be avoided if you’ve been diagnosed with IOP. This is because research studies have shown that it causes transient surges in intraocular pressure (IOP).
2. Age- The occurrence of open-angle glaucoma rises with advancing age. Studies show that among Americans aged 73 to 74 years, the prevalence rate stands at 3.4%, and rises to 9.4% for individuals over the age of 75. There is a correlation between older age and a higher degree of optic nerve damage, as well as an accelerated rate of glaucoma advancement. The aging process is believed to heighten the susceptibility of the optic nerve to damage associated with intraocular pressure (IOP). Hence, older patients need enhanced intraocular pressure management to avert the progression of the disease.
3. Optic Nerve Properties: The anatomy of the optic nerve can vary, and factors such as the cup-to-disc (CDR) ratio may indicate a greater likelihood of damage and visual deterioration. The CDR is the relationship between the size of the optic cup (which is the depression found in the optic nerve) and the size of the optic disc (the area through which the optic nerve enters the eye). A CDR of 0.6 or higher raises suspicion for glaucoma, though it does not confirm the diagnosis.
4. Genetic Factors: A family history of glaucoma increases the risk of the disease. Genetic factors like mutation in specific genes play an important role in the development and progression of glaucoma through various pathogenic mechanisms. For instance, the MYOC (myocilin) gene mutations contribute to roughly 8-36% of juvenile open-angle glaucoma (JOAG) and about 2-4% of adult-onset primary open-angle glaucoma (POAG). This prevalence differs based on the ethnicity of the population examined.
5. Thinner Central Cornea: There is a significant association between central cornea thickness and risk of developing glaucoma. A reduced cornea thickness has been linked to a heightened risk of disease progression. For every 40 micrometer reduction in central corneal thickness (CCT),the probability of disease progression rises with an odds ratio (OR) of 1.45. This suggests that corneas of reduced thickness are associated with an increased risk of developing glaucoma.
Why is early detection/prevention encouraged?
Glaucoma is asymptomatic in its early stages which makes it challenging to be diagnosed clinically. It frequently goes undetected until significant vision impairment has taken place. Early detection of glaucoma reduces visual impairment and blindness, while also being an effective means of reducing costs. Efficient methods of glaucoma screening are therefore warranted for early detection of disease. Routine eye examinations are essential, particularly for individuals who are at an elevated risk, such as older adults and individuals with a familial predisposition to glaucoma. These assessments facilitate the early identification of increased IOP, angle closure or other concerning indicators that could result in any type of glaucoma.
For individuals identified as having primary angle closure suspects (PACS), advancements in treatment like the laser peripheral iridotomy and/or iridoplasty, are proving effective to open the angle or halt the angle closure process in primary angle-closure glaucoma. Hence, with early detection, PACG may be preventable in the early stages. For the management of IOP, more effective and better tolerated drugs are being developed. In 2023, the FDA approved iDose TR (Glaukos), a travopost implant designed to effectively reduce intraocular pressure (IOP) in patients suffering from open-angle glaucoma. This has been reported to reduce ocular pressure by 6-7 mmHg. Also, there are ongoing advancements in the creation of new treatments designed to directly target and preserve the retinal ganglion cells that suffer damage due to glaucoma.
Ultimately, with regular eye examinations, glaucomatic symptoms can be identified and treated preventing disease progression and averting blindless.
