Glaucoma: Causes, Types, Signs, Treatment- Surgery, Laser, Filtering, Drainage Implants
Glaucoma is a collection of eye conditions causing damage to the optic nerve resulting in loss of vision. In this condition, there is an excessive increase of intraocular pressure (pressure within the eyes) resulting in damage to the optic nerve. It is very important to diagnose and treat glaucoma in early stages to prevent optic nerve damage and vision loss. This can be done by going for regular eye checkups.
One of the major of causes of blindness in USA is Glaucoma. In this condition, there is gradual loss of vision and the patient notices this disease when it has progressed very far. There are many types of glaucoma, of which the most common is primary open-angle glaucoma.
Causes of Glaucoma
Glaucoma is caused due to increased intraocular pressure. This happens due to accumulation of aqueous humor, a fluid which passes through our eyes and escapes via a drainage system at the junction of iris and cornea. Any problems in this drainage system results in delay of the filtering speed of this fluid leading to buildup and increased intraocular pressure.
Risk Factors for Glaucoma
- Increased intraocular pressure greatly increases your risk for developing glaucoma.
- Individuals over the age of 60 are at a higher risk for developing glaucoma.
- Individuals of Mexican-American ancestry are at an increased risk for developing angle-closure glaucoma, especially if they are above 40 years.
- African-Americans also are at a high risk for developing glaucoma and should have regular eye exams.
- Individuals of Asian descent are at an increased risk for developing acute angle-closure glaucoma.
- Individuals of Japanese descent are more prone to developing normal-tension glaucoma.
- People with family history of glaucoma are at an increased risk for developing it.
- Other medical conditions, such as heart diseases, hypertension, diabetes, and hypothyroidism increase the risk for developing glaucoma.
- Other eye problems such as trauma, retinal detachment, eye tumors, lens dislocation and eye inflammation, surgery to the eye, being farsighted or nearsighted, also puts a patient at increased risk for developing glaucoma.
- Prolonged use of corticosteroid medications, specifically eye drops increase the risk for developing secondary glaucoma.
Types of Glaucoma
- Primary Open-Angle Glaucoma: In this type, the drainage angle made by the iris and cornea remains open, whereas drainage channels known as the trabecular meshwork, are blocked partially resulting in slow drainage of the fluid from the eye causing buildup of fluid and pressure in the eye. There is gradual vision loss and it becomes noticeable only when the damage is extensive. The cause of primary open-angle glaucoma is not known.
- Angle-Closure Glaucoma: Also known as closed-angle glaucoma, it occurs when there is forward bulging of iris, which restricts or blocks the drainage angle made by iris and cornea resulting in inadequate flow and drainage of the fluid which leads to sudden increase in the intraocular pressure.
- Chronic angle-closure glaucoma is where it occurs gradually.
- Acute angle-closure glaucoma is the sudden development of this condition.
- Normal-Tension Glaucoma: In this type, despite the intraocular pressure remaining normal, the optic nerve suffers damage. The exact cause for this is not understood; but the reason thought to be is diminished blood supply to the optic nerve or a sensitive optic nerve.
- Developmental Glaucoma: In this type of glaucoma, children or infants have glaucoma.
- Congenital Glaucoma: In this type, children are born with glaucoma.
- Infantile Glaucoma: Children develop glaucoma in the initial years of their life.
- Juvenile Glaucoma: In this, children develop glaucoma after crossing 4 or 5 years of age.
- Pigmentary Glaucoma: In this type, the pigment granules present in the iris start accumulating in the drainage channels resulting in blockage or slow drainage of the fluid. Vigorous activities such as running, jogging may shake up the pigment granules leading to them being deposited in the drainage channels. This causes intermittent increases in the intraocular pressure.
Signs and Symptoms of Glaucoma
Symptoms depend on the type of glaucoma.
Symptoms of Primary Open-Angle Glaucoma Include
- Gradual peripheral vision loss, which commonly occurs in both the eyes.
- Patients with advanced stages of glaucoma develop tunnel vision.
Symptoms of Acute Angle-Closure Glaucoma Include
- Eye ache/pain
- Vomiting along with severe pain in the eye.
- Sudden visual disturbances, especially in dim light.
- Patient also experiences blurry vision.
- Patient can see halos surrounding a light.
- Eye appears reddish in color.
Investigations for Glaucoma
- Medical history and complete eye examination.
- Tonometry is one of the initial tests done for measuring the intraocular pressure. This is done after instillation of eye drops to anesthetize your eyes.
- The ophthalmologist also checks for any damage to the optic nerve. This is done by using instruments which help the doctor to visualize directly past the pupil to the posterior region of the eye, so that he/she can detect minor changes which may indicate the start of glaucoma.
- Visual field test is a test done for analyzing the vision of the patient and to see the extent of damage to the vision from glaucoma.
- Visual acuity is a test which helps in checking long distance vision.
- Pachymetry is a test done to measure the thickness of the cornea which is important in the diagnosis of glaucoma. The eyes are numbed before this procedure and the corneal thickness is measured. People with thick corneas have higher than normal eye-pressure reading, but glaucoma may still be present. Likewise, people with thin corneas may have readings which are at normal pressure, but still suffer from glaucoma.
- Gonioscopy is a test which helps in differentiating between open-angle and angle-closure glaucoma. In this technique a special lens is kept in the eye which helps in examining the drainage angle.
Treatment for Glaucoma
The aim of treatment is to bring down the increased intraocular pressure. This can be done by medicines to decrease the fluid production in the eye. Doctors also try to correct the fluid drainage system in the eyes so the pressure within the eyes is reduced. There is no complete cure for glaucoma and the damage caused by it is irreversible. The only thing to do is proper treatment on proper time and regular eye checkups, so as to prevent vision loss in individuals having early stage glaucoma. If a patient already suffers from vision loss, then treatment is done to prevent or halt any further vision loss.
- Eye Drops: Medicated eye drops are the initial treatment done in glaucoma. Patient should follow doctor's instructions when using these drops; if not, then the damage to the optic nerve can increase.
Some of the commonly prescribed eye drops are
- Prostaglandins such as bimatoprost and latanoprost are used to treat open-angle glaucoma. They increase the drainage of the fluid from the eye thus resulting in decreased intra-ocular pressure. Side effects include blurry vision, stinging, minor reddening of the eyes; the iris may appear dark. There may also be pigment changes in the skin of the eyelids.
- Beta Blockers, such as timolol and betaxolol, help by reducing the fluid production in the eyes thus reducing the internal eye pressure (intraocular pressure). Side effects include decreased heart rate, difficulty in breathing, hypotension, fatigue and impotency. Beta blockers are contraindicated in patients having heart or lung conditions, as these medications exacerbate existing breathing problems.
- Alpha-adrenergic agonists, such as apraclonidine and brimonidine, also help in reducing the production of the fluid (aqueous humor) and also increase the drainage of this fluid from the eye. Side effects include irregular heartbeat, hypertension, tiredness, itchy, red or swollen eyes, and mouth dryness.
- Carbonic anhydrase inhibitors, such as brinzolamide and dorzolamide, are not used that often. They work by reducing the fluid production in the eye. Side effects include sensation of pins and needles in the fingers and toes and frequent urination.
- Cholinergic (Miotic) agents, such as pilocarpinean and carbachol, also increase the drainage of fluid from the eye. Side effects include small sized pupils, nearsightedness or blurry vision.
- A combination of medications such as alpha adrenergic agonist and beta blocker; carbonic anhydrase inhibitor and beta blocker may also be prescribed by some doctors.
- Oral medications are given if eye drops are not successful in bringing down the intraocular pressure. They are often in the form of carbonic anhydrase inhibitor and help in bringing down the eye pressure. Side effects include: Stomach upset, frequent urination, pins and needles sensation in toes and fingers, depression and kidney stones.
Surgery for Glaucoma
Surgery is done if the patient does not benefit from medications or if for some reason is not able to tolerate the medications. Sometimes more than one surgery is needed to successfully bring down the eye pressure. Eye drops may be needed after the surgery also. Potential complications from surgery for glaucoma include: Inflammation, infection, bleeding, abnormally increased or decreased eye pressure and vision loss. Glaucoma surgery may also increase the risk of cataracts. However, these complications can be successfully treated.
Different Surgeries for Treating Glaucoma Include
- Laser Surgery: Laser trabeculoplasty is an outpatient procedure done for treating open-angle glaucoma. Numbing eye drops are instilled in the eye, after which a high-energy laser beam is used to open the blocked drainage canals so that the fluid is able to drain easily from the eye. Follow up for eye pressure checkups is mandatory after this surgery. At first laser surgery will lower the intraocular pressure; however, gradually it may start increasing again.
- Filtering Surgery: If the eye pressure still remains high even after using eye drops and laser surgery, then another surgical procedure known as trabeculectomy (either inpatient or outpatient) is done. After numbing the eye, the surgeon makes an opening in the sclera and extracts a small part of eye tissue from the base of the cornea from where the fluid exits the eye. This will result in free drainage of the fluid and consequently decreased eye pressure.
- Drainage Implants: This is done in patients having secondary glaucoma or advanced glaucoma or in children suffering from glaucoma. It can be done on an inpatient or outpatient basis. A small tube is inserted in the eye to help in fluid drainage thus resulting in decreased intra-ocular pressure.
Treatment for Acute Angle-Closure Glaucoma
Acute angle-closure glaucoma is a serious condition and requires prompt medical attention to bring down the eye pressure to a normal level. Treatment comprises of medications as well as surgery.
Laser Peripheral Iridotomy is a procedure where the surgeon, with the help of laser, makes a small hole in the iris so that the fluid (aqueous humor) can freely exit the eye. The other eye is also examined and an iridotomy may also be recommended for it, as it also carries a high risk for closure or blockage of its drainage angle.