January is National Glaucoma Awareness month and awareness is vital as Glaucoma can cause vision loss without any symptoms. Scary, right?! Open-angle glaucoma, the most common form, rarely causes symptoms until it’s in an advanced stage. Hence why it’s known as the silent thief of sight.
Being proactive and getting your eyes checked regularly is incredibly important as your eye doctor can spot the signs of glaucoma like worse peripheral vision (side vision), optic nerve damage and elevated eye pressure. Let’s dive into the nitty gritty details to get a better understanding of this disorder.
So what is Glaucoma exactly?
Glaucoma’s a progressive disease of the optic nerve caused when the pressure in the eye is higher than the optic nerve can stand. Progression occurs over time and it tends to be inherited. There are many types and forms – the most common causes a patient to slowly lose their vision, starting peripherally. Patients with glaucoma rarely have complaints.
Worldwide it’s the second leading cause of irreversible blindness, impacting 6 million individuals who are blind in both eyes.
Who’s at risk of developing Glaucoma?
Anyone can get glaucoma, however some are at higher risk than others.
- African Americans
- 40+ years of age
- Family history of glaucoma
- Patients with diabetes
What can cause Glaucoma?
Glaucoma is a group of eye diseases that in most cases is due to an increased pressure in the eye. Pressure levels vary for each patient and even throughout the day. Over time, changes in pressure will cause damage to the optic nerve.
The aqueous humor or fluid is constantly produced by a tiny gland - the cilliary body. It flows between the iris and the lens, then out of the eye through a very small drain called the trabecular meshwork. When this drain becomes clogged, the fluid can’t leave the eye and the fluid causing the pressure is still being produced.
Since the eye is a closed compartment, it doesn’t overflow; instead the backed up fluid causes an increase in pressure resulting in damage to the optic nerve over time. There are two basic theories as to why excessive ocular pressure causes glaucoma.
- Vascular Theory--High pressure decreases blood flow to the optic nerve
- Physical Theory --High pressure, over time, destroys the individual nerve fibers
What symptoms might one experience?
Typically, patients don’t notice any symptoms until the late stages of the disease – usually has progressed and damaged almost 50% of the nerve tissue. Eek! That silent sight thief!
Without treatment, patients with glaucoma may find that they have reduced peripheral vision. Optic nerve damage caused by glaucoma is permanent - making it super important to seek treatment in the early stages of the disease rather than waiting until symptoms are noticed.
Most people think they have glaucoma if the pressure in their eye is high. Not always true. Whether or not you get glaucoma depends on the level of pressure that your optic nerve can tolerate without being damaged. This level is different for each person. Although normal pressure is usually said to be between 12-21 mm Hg, a person might have glaucoma if pressures fall lower than, in between, or higher than this limit.
What’s the process for diagnosing?
Thanks to recent advances & new studies the ability to diagnose glaucoma earlier and more accurately continues to improve. A typical evaluation should include:
- Comprehensive Dilated Eye Exam: eye exam should include dilation of the pupils and a stereoscopic view of the retina
- Gonioscopy: a lens is placed on the eye that lets the doctor evaluate the trabecular meshwork or “drain”. This is where the fluid drains into our lymphatic system.
- Pachymetry: measuring the thickness of the cornea. One of the major findings of the Ocular Hypertension Treatment Study was that if we are measuring the internal pressure of the eye through a thick cornea the pressure will measure higher then it truly is and conversely if the cornea is thin the pressure will be measured lower than it really is. To know the true intra-ocular pressure, we measure the cornea's thickness.
- Tonometry: measuring the pressure in the eye, by gently pressing on the patient's cornea
- Fundus photos : a photograph is taken of the retina and the optic nerve to help monitor for progression or changes to the nerve itself.
- Threshold Visual Field: since the primary symptom of glaucoma is a progressive decrease in peripheral vision, one of the most important tests is a visual field which detects how dim of a light a patient can detect in their peripheral vision.
- Scanning Laser Ophthalmoscopy: measures the thickness of the layer of nerve fibers leading to the optic nerve and may define the shape of the optic nerve to monitor for progression. Think of it like an ultrasound of the eye.
How is Glaucoma treated?
When diagnosed and treatment is begun, it is a lifelong disease that will require continuous treatment. We can control or slow the progression but unfortunately cannot cure it. There are many medications available, and depending on severity more than one medication may be used. If glaucoma can’t be controlled with medications other procedures, including surgery, may be considered.
Everyone over 40 should have a regular comprehensive eye exam to check for signs of glaucoma and other eye conditions. Keeping a pulse on your eye health and getting in for regular exams is your best bet for allowing yourself to see the world!