Many of us see a slight deterioration in vision over time as normal. After all, most people need reading glasses as they enter ‘old age’, don’t they?
While it’s true reading glasses are a common feature among the older generation, gradual loss of vision doesn’t always mean you simply ‘need glasses’. Loss of vision can occur as a result of glaucoma – a progressive condition that if left untreated can cause permanent damage to the optic nerve and result in gradual vision loss and blindness if left untreated.
What exactly is glaucoma?
Glaucoma is a condition of increased pressure within the eyeball, causing gradual loss of sight.
The most common form of glaucoma results from increased intra-ocular pressure.
What does this mean?
Well, simply put the eyeball is continually producing and draining fluid – this fluid is known as ‘aqueous humor’. The fluid is produced by certain cells that lie behind the iris (that is, the colored part of the eye). This fluid then circulates through the pupil into the front of the eye and drains out through a complex circular drainage structure in the “angle.”
This angle is formed between the iris and the cornea – which is the clear front covering of the eye. When this fluid cannot drain properly or too much is produced, pressure in the eye becomes elevated – causing damage to vital structures in the eye.
This might sound likely an uncomfortable – or even painful – scenario, but the truth is in many cases people do not realize that pressure is building within the eye or that damage is occuring. You can’t always feel it!
How is glaucoma treated?
The good news is the condition is treatable.
For a long time, prescription eye drops have been the first line treatment for glaucoma. These drops work very well, but they do have their shortcomings. They rely on the fact that patients will use them religiously every day and at the correct time – if you’ve ever had to take medication long term, you’ll be well aware that is far trickier than it sounds!
The drops, just like any medication, can have side effects and can cause allergic reactions. Additionally, eye drops can lose their efficacy over time, necessitating additional drops or other forms of intervention.
Another treatment used in conjunction with eye drops, or possibly as a stand-alone method, is a laser treatment termed ‘selective laser trabeculoplasty’ (SLT).
This laser treatment is unlike LASIK vision correction where the overarching goal is to improve vision. Instead, SLT is a preventative procedure that is done to lower eye pressure and protect the level of vision of a patient. In other words, the procedure aims to prevent further vision loss due to glaucomatous changes that occur if eye pressure is elevated to an unsafe level.
How does SLT work?
The SLT laser targets specific cells in the trabecular meshwork (that is, the drainage system of the eye) to allow it to improve the outflow of fluid. This improved drainage in turn lowers eye pressure.
The effects of SLT are not typically instantaneous, but rather take a few weeks for maximum results. Therefore, prescription eye drops may be continued initially to ensure the eye pressure stays at a safe level. Once the effect from the laser has had time to fully develop, eye drops may be discontinued to determine if the goal eye pressure is maintained.
This process occurs under the care of the ophthalmologist or optometrist.
Is SLT safe?
Selective laser trabeculoplasty is very safe, is done as an outpatient procedure, and the treatment takes just a few minutes.
As discussed above, SLT can be used as a first line approach – but it can also be used in conjunction with eye drops.
Does your eye doctor want to add a second eye drop to your regimen?
It’s possible that SLT could eliminate the need for that.
Are you allergic to an eye drop but your eye pressure is not yet at the goal your eye doctor has set for you?
SLT again could be a solution.
One other optimal use for SLT is in patients that have been diagnosed with glaucoma at a relatively young age. Being on eye drops for 40+ years is less than ideal, and the longer the duration of use, the higher the probability that patients will acquire side effects. Longer use of eye drops can also sometimes cause a decrease in efficacy.
With very few but manageable complications and an approximated 50-80% success rate in patients, selective laser trabeculoplasty is a great treatment option for glaucoma. It is important to note that the efficacy of this technique can wear off over time, necessitating a repeat procedure, addition of eye drops, or further surgical intervention. Therefore, it is important to continue routine eye health checks with your ophthalmologist or optometrist.
In some eyes, the angle described above is narrower than usual, and is called “narrow angle.”
Eyes with narrow angles are at risk of developing “angle closure” in which access to the drain is closed off completely and fluid that is being produced in the eye is trapped and cannot escape the eye. This leads to a sudden increase in eye pressure to dangerous levels, which can result in permanent vision loss in a short amount of time.
Most patients who have narrow angles are hyperopic, or “far sighted.” Typically these are individuals who have never needed glasses to see clearly, with the exception of reading glasses after the age of 40 or so. Hyperopic eyes tend to be shorter and smaller than the average eye, so everything is condensed in the eye, including the angle.
Besides hyperopic patients, elderly patients who have not had cataract surgery are also at risk because as a cataract develops, it pushes the iris forward, narrowing the angle.
Typically, narrow angles are asymptomatic – that is, they don’t cause any noticeable problem to the patient. On the other hand, angle closure – if it develops – often leads to dramatic symptoms, such as:
Occasionally, patients with narrow angles suffer from intermittent episodes of angle closure attacks; these are usually associated with a mild or moderate headache in dark light conditions, blurring of the vision for a few hours, redness, and sometimes nausea and vomiting.
What is the best treatment option for narrow angles?
There are several options for narrow angles, and your doctor will review which option is the best depending on the overall health of the eye.
In general, treatment involves either laser surgery or cataract surgery.
Laser surgery typically involves making an iridotomy, which is a small hole in the iris that causes the angle to become less acute, and to open further. This laser is different than the first laser discussed above.
If one has narrow angles as well as a cataract, cataract surgery can sometimes be performed since it will both improve the vision and usually cure the narrow angle as well—removing a large cataract frees up space inside the eye giving more room for other structures.
Not only can cataract surgery be useful in treating narrow angles, but it can also be advantageous in patients with mild to moderate open angle glaucoma.
These patients are typically:
What exactly are cataracts?
A quick review of cataracts reminds us that a cataract is a normal, age-related process that occurs when the natural lens in your eye begins to cloud. This clouding causes vision to be decreased and induces uncomfortable glare, among many other symptoms. When cataracts begin to interfere with a patient’s daily lifestyle, surgery is warranted.
As discussed above, glaucoma is a disease that typically occurs due to increased pressure within the eye because the outflow of fluid in the eye is not enough or the drainage system of the eye cannot keep up with the eye’s production of fluid.
If eye pressures become too high, irreversible damage to the optic nerve can result in permanent vision loss. Typical initial treatment for glaucoma is medication in the form of eye drops or selective laser trabeculoplasty as discussed previously. These drops work well, but side effects, decreased efficacy, and questionable patient compliance with drops are all issues that can arise.
Newer technology is on the horizon and surgeons now have access to a device with the capability to lower eye pressure safely and bypass all of the above issues associated with eye drops.
The iStent, developed by Glaukos, is an FDA approved glaucoma therapy device for use during routine cataract surgery. It is a trabecular meshwork micro-bypass system designed to increase outflow of aqueous humor (the fluid in your eye that gives it its shape) and in turn lower the eye’s intra-ocular pressure. It works in a similar manner that stents do to help prevent heart attacks or strokes, but of course the goal of the iStent is to improve the outflow of fluid in one’s eye – in short, it is an eye drop-less form of glaucoma treatment.
Fun fact: Did you know that the iStent is the smallest device that can be implanted into the human body?
There are a number of benefits to the iStent:
It is important to note that not all patients with glaucoma are deemed good candidates for this procedure. Therefore, a thorough examination will be performed by an ophthalmologist or optometrist prior to any recommendations being made.
The iStent works in a large percentage of patients; however, because glaucoma is a degenerative condition, routine follow up appointments with an optometrist or ophthalmologist to monitor eye health is still necessary after this procedure.
If you have glaucoma or are farsighted, you should have at least one eye exam a year to make certain your eye pressures are stable and to ensure you have not developed a narrow angle.
As you age it’s always a good idea to have routine eye health check ups – after all, your vision is precious!
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