Glaucoma (Primary Open Angle)
Damage in the optic nerve or the nerve connecting the eyes to the brain can cause primary open angle glaucoma. This leads to the total loss of sight or vision. This is due to an increased pressure in the eyes. By reducing the pressure in the eyes, it can delay or prevent glaucoma from worsening. The adults who are aged thirty five to forty are at high risk for this disease and should have regular check-ups for their eyes to detect glaucoma as early as possible.
The following are the different kinds of glaucoma:
- Primary open angle glaucoma or chronic glaucoma – this type is very common. This disease would normally develop slowly and the damage to the optic nerve and loss of vision would be gradual. The ‘open angle' term for the disease is referring to the normal angle of the iris and sclera. The rest of this leaflet will primarily deal with this disease.
- Acute angle closure glaucoma – this type of glaucoma is very rare and the ‘angle' in this type is narrowed. There is an increase in pressure in just one eye which can quickly become red and painful.
- Secondary glaucoma – this is due to other eye conditions that also increase pressure in the eyes.
- Congenital glaucoma or buphthalmos – this type of glaucoma is initially present since birth.
The Eyes and the Aqueous Humour
It is very important for the eyes to maintain their shape so the light rays can be accurately focused to the retina. The vitreous humour is a jelly-like bulk component that fills the majority of the eye. But the clear fluid, aqueous humour, fills the front of the lens.
The aqueous humour is fluid by nature and is made up of cilliary body cells. This provides an outward pressure to keep the shape of the eye. The fluid is made up of sugars and oxygen to give sustenance to the many different parts of the eye. The aqueous humour drains into the bloodstream via a sieve-like meshwork of trabeculae which is found near bottom of the iris. To sum it up, there should be a continuous production and draining of this fluid.
Mechanism for Primary Open Angle Glaucoma
Primary open angle glaucoma occurs when partial blockage occurs in the trabecular meshwork. This would then restrict the aqueous humour from being drained. This leads to the pressure build up of the aqueous humour and eventually it would affect the pressure at the back of the eyes as well. The increase in pressure could then lead to damaging the optic nerve and the nerve fibers that run along the retina. This could then lead to permanent loss of vision or blindness or at least some parts of the eyes or ‘patches'.
Glaucoma and Increase in Eye Pressure
Glaucoma involves an increase in eye pressure that would damage the optic nerve. But one in every five patients with glaucoma would have normal eye pressure ranges or ‘normal pressure glaucoma'. This is a condition wherein optic nerve damage is caused by a low eye pressure. There are other factors that affect this low eye pressure such as reduced blood supply which could render the optic nerve to become very sensitive even to small eye pressures. On the contrary, those people who have high eye pressure will have no damage to their optic nerve. But as a caution, having a high eye pressure gives a person a higher risk of contracting glaucoma and eventually loss of vision.
Risk Factors for Primary Open Angle Glaucoma
One in every five people in UK who are over forty years of age has glaucoma. It is very unusual for people below the age of thirty-five to acquire this disease. The elderly are at higher risk for glaucoma but it can also affect anyone:
- Those who have a familial history or have family members afflicted with glaucoma.
- People who are short-sighted
- Those afflicted with diabetes
- People who are of Afro-Caribbean or African origin.
Symptoms for Primary Open Angle Glaucoma
There are no symptoms initially; no redness nor pain in the eyes. Most of the patients do not see that they have problems until they lose some of their vision. The outer or the peripheral vision tends to be the first part of the sight to be affected while the central vision, which focuses on objects such as reading, is spared until the last part of the disease. Although glaucoma can affect both eyes, the severity by which each eye is affected may differ.
Some of the symptoms for glaucoma especially for the elderly can be dismissed as being part of getting old. The elderly patients may not see the need to consult nor have their eyes checked. Leaving glaucoma untreated is one of the most common factors to cause blindness. But it should be noted that once glaucoma is treated, then there is a high probability that blindness can also be prevented.
The elderly or people over the age of thirty five or forty should have their eyes checked regularly at least once in every five years. For those who are older than fifty years old, eye check-ups should be done at least twice or thrice every five years. The eye check-up would be great to detect any anomaly in your eyes and prevent any complications that could lead to glaucoma and eventually blindness.
The eye check-up would be composed of these activities:
- eye pressure measurement
- using a special torch to view the back portion of the eye
- checking for the field of vision of both eyes
Some people can have free eye check-ups especially if the person is aged over forty and has a family member who has glaucoma.
Treatment for Primary Open Angle Glaucoma
The treatment aims for the eye pressure to be lowered. Once the eye pressure is lowered, any damage to the optic nerve can be delayed or prevented. The treatment also varies from case to case especially if the patient has very high eye pressure.
- Eye drops – there are a lot of eye drops in the market and they work in two ways:
- The amount of aqueous humour is lowered
- The draining of the aqueous humour is increased.
Some eye drops would not be suitable for people with asthma while some eye drops would have side effects. Consult your eye specialist to make sure that you have the right eye drop for your condition. It usually takes about two different eye drops to have the eye pressure at a low level. Always remember to apply the eye drops as instructed. If you are having any problems applying the eye drop, ask your doctor or nurse to help you.
- Tablets – this type of medication works by lowering the aqueous humour amount in the eye. There are known side-effects when using some drugs and doctors do not recommend this for their patients.
- Surgery – trabeculectomy is an operation which involves the creation of a channel from inside the front of the eyes to the conjunctiva. This operation makes the aqueous humour bypass the blockage in the trabecular meshwork. This creates a minute ‘safety valve'. This option can be advised if the patient does not have lowered eye pressure after using one or two eye drops. This is also advised for younger people. Undergoing surgery is not without side effects and in some cases the operation would be repeated because a scar tissue may form at the area of the channel. The scar tissue may prevent the newly created channel from draining the aqueous humour.
- Laser treatments – the trabecular meshwork is burned with a laser to improve the drainage for aqueous humour. Another laser technique destroys the cilliary body parts to lower the aqueous humour amount being produced. However, laser treatments are not done often because the treatment would only last for a short period of time.
Glaucoma and Driving
If the patient is a driver or can drive and has glaucoma with both eyes, then the law states that he should inform the Driver and Vehicle Licensing Authority (DVLA) because the patient would need to undergo a special test for the eyes. The test checks on the severity of your condition and how serious glaucoma has affected your vision. In most cases, the patient can pass the test and is still able to continue on driving.
- Acute Glaucoma
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