Glaucomas are a group of eye disorders characterized by progressive optic nerve damage in which an important part is a relative increase in intraocular pressure (IOP) that can lead to irreversible loss of vision.
A series of eye disorders known as glaucoma harm the optic nerve. For clear vision, the optic nerve, which transmits visual data from the eye to the brain, is essential. High pressure in your eye is frequently associated with damage to the optic nerve. Yet, glaucoma can develop with normal eye pressure as well.
Although while it may strike anybody, older persons are more likely to develop glaucoma. For those over 60, it is one of the main causes of blindness.
Many forms of glaucoma have no warning signs. The effect is so gradual that you may not notice a change in vision until the condition is in its later stages.It’s important to have regular eye exams that include measurements of your eye pressure. If glaucoma is recognized early, vision loss can be slowed or prevented. If you have glaucoma, you’ll need treatment or monitoring for the rest of your life.
Glaucomas are categorized as
- Open-angle glaucoma
- Angle-closure glaucoma
The angle at which the iris and cornea converge at the outer edge of the anterior chamber is referred to as the “angle” (see figure Aqueous humor production and flow). The angle is where more than 98% of the aqueous humor leaves the eye, either by the principal exit route—the trabecular meshwork and Schlemm canal, especially in elderly individuals—or the ciliary body face and choroidal vasculature. These outflow routes involve active physiological processes rather than being only a mechanical filter and drain.
There are more than 20 adult varieties of glaucoma, which are further classified into primary (when the source of outflow resistance or angle closure is unknown) and secondary (where the origin of the outflow resistance derives from a recognized condition).
Open-Angle Glaucoma: Classification Based on Mechanisms of Outflow Obstruction
| Type | Means | Examples |
|---|---|---|
| Trabecular | ||
| Idiopathic | Disorder of extracellular matrix | Corticosteroid-induced glaucomaJuvenile glaucomaPrimary open-angle glaucomaPseudoexfoliation glaucoma |
| Obstruction | By red blood cells | Ghost cell glaucomaHemorrhagic glaucoma |
| By macrophages | Hemolytic glaucomaMelanomalytic glaucomaPhacolytic glaucoma | |
| By neoplastic cells | Juvenile xanthogranulomaMalignant tumorsNeurofibromatosisNevus of Ota | |
| By pigment particles | Exfoliation syndrome (glaucoma capsulare)Pigmentary glaucomaUveitis | |
| By protein | Lens-induced glaucomaUveitis | |
| Due to other means | Viscoelastic agentsVitreous hemorrhage | |
| Alterations | Due to edema | Alkali burnsIritis or uveitis causing trabeculitisScleritis or episcleritis |
| Due to trauma | Angle recession | |
| Due to intraocular foreign bodies | ChalcosisHemosiderosis | |
| Posttrabecular | ||
| Obstruction of the Schlemm canal | By particulate matter or collapse of canal walls | Age-related changes in canal wallSickled red blood cellsTrauma |
| Reduced flow in aqueous veins | Due to elevated episcleral venous pressure | Carotid-cavernous fistulaCavernous sinus thrombosisIdiopathic episcleral venous pressure elevationMediastinal tumorsInfiltrative ophthalmopathy (thyrotropic exophthalmos)Retrobulbar tumorsSturge-Weber syndromeSuperior vena cava obstruction |
Angle-Closure Glaucoma: Classification Based on Mechanisms of Outflow Obstruction
| Mechanism | Examples |
|---|---|
| Anterior (pulling mechanism) | |
| Contracture of membranes | Iridocorneal endothelial syndromeNeovascular glaucomaPosterior polymorphous dystrophySurgery (eg, corneal transplant)Trauma (penetrating and nonpenetrating) |
| Contracture of inflammatory precipitates | — |
| Inflammatory membrane | Fuchs heterochromic iridocyclitisLuetic interstitial keratitis |
| Posterior (pushing mechanism) with pupillary block | |
| Lens induced | Intumescent lensSubluxation of lensMobile lens syndrome |
| Posterior synechiae | Iris-vitreous block in aphakiaPseudophakiaUveitis |
| Posterior (pushing mechanism) without pupillary block | |
| Aqueous misdirection | Ciliary block (malignant glaucoma) |
| Cysts of the iris and ciliary body | — |
| Forward vitreous shift after lens extraction | — |
| Intraocular tumors | Malignant melanomaRetinoblastoma |
| Lens induced | Intumescent lensSubluxation of lensMobile lens syndrome |
| Large or anterior displaced ciliary body | Plateau iris syndrome |
| Uveal edema | After scleral buckling, panretinal photocoagulation, or central retinal vein occlusion |
| Retrolenticular tissue contracture | Persistent hyperplastic primary vitreousRetinopathy of prematurity (retrolental fibroplasia) |
Symptoms
The symptoms of glaucoma depend on the type and stage of your condition.
Open-angle glaucoma
- No symptoms in early stages
- Gradually, patchy blind spots in your side vision. Side vision also is known as peripheral vision
- In later stages, difficulty seeing things in your central vision
Acute angle-closure glaucoma
- Severe headache
- Severe eye pain
- Nausea or vomiting
- Blurred vision
- Halos or colored rings around lights
- Eye redness
Normal-tension glaucoma
- No symptoms in early stages
- Gradually, blurred vision
- In later stages, loss of side vision
Glaucoma in children
- A dull or cloudy eye (infants)
- Increased blinking (infants)
- Tears without crying (infants)
- Blurred vision
- Nearsightedness that gets worse
- Headache
Pigmentary glaucoma
- Halos around lights
- Blurred vision with exercise
- Gradual loss of side vision
Causes
When the optic nerve is harmed, glaucoma results. Blind patches appear in your eyesight when this nerve progressively deteriorates. This nerve injury is typically correlated with elevated ocular pressure for reasons that doctors are unsure of.
A accumulation of fluid that circulates across the interior of the eye causes elevated ocular pressure. The aqueous humor is another name for this substance. Normally, it exits via a tissue at the point where the iris and cornea converge. The trabecular meshwork is another name for this tissue. Since it allows light to enter the eye, the cornea is crucial to vision. Eye pressure may rise when the eye produces too much fluid or when the drainage system isn’t functioning properly.
Open-angle glaucoma
This is the most common form of glaucoma. The drainage angle formed by the iris and cornea remains open. But other parts of the drainage system don’t drain properly. This may lead to a slow, gradual increase in eye pressure.
Angle-closure glaucoma
This form of glaucoma occurs when the iris bulges. The bulging iris partially or completely blocks the drainage angle. As a result, fluid can’t circulate through the eye and pressure increases. Angle-closure glaucoma may occur suddenly or gradually.
Normal-tension glaucoma
No one knows the exact reason why the optic nerve becomes damaged when eye pressure is normal. The optic nerve may be sensitive or experience less blood flow. This limited blood flow may be caused by the buildup of fatty deposits in the arteries or other conditions that damage circulation. The buildup of fatty deposits in the arteries also is known as atherosclerosis.
Glaucoma in children
A child may be born with glaucoma or develop it in the first few years of life. Blocked drainage, injury or an underlying medical condition may cause optic nerve damage.
Pigmentary glaucoma
In pigmentary glaucoma, small pigment granules flake off from the iris and block or slow fluid drainage from the eye. Activities such as jogging sometimes stir up the pigment granules. That leads to a deposit of pigment granules on tissue located at the angle where the iris and cornea meet. The granule deposits cause an increase in pressure.
Glaucoma tends to run in families. In some people, scientists have identified genes related to high eye pressure and optic nerve damage.
Risk factors
- High internal eye pressure, also known as intraocular pressure
- Age over 55
- Black, Asian or Hispanic heritage
- Family history of glaucoma
- Certain medical conditions, such as diabetes, migraines, high blood pressure and sickle cell anemia
- Corneas that are thin in the center
- Extreme nearsightedness or farsightedness
- Eye injury or certain types of eye surgery
- Taking corticosteroid medicines, especially eye drops, for a long time
Diagnosis
- Measuring intraocular pressure, also called tonometry
- Testing for optic nerve damage with a dilated eye examination and imaging tests
- Checking for areas of vision loss, also known as a visual field test
- Measuring corneal thickness with an exam called pachymetry
- Inspecting the drainage angle, also known as gonioscopy
Such patients (as well as those with any risk factors) should be referred to an ophthalmologist for a thorough examination that includes a detailed medical history, family history, examination of the optic disks (preferably using a binocular examination technique), formal visual field examination, tonometry (measurement of IOP), measurement of central corneal thickness, imaging of the optic nerve and/or retinal nerve fiber layer using optical coherence tomography, and gonioscopy (visualization of the anterior chamber angle with a special mirrored contact lens prism).
When typical signs of optic nerve damage are present and all other potential causes, such as multiple sclerosis, have been ruled out, glaucoma is diagnosed. High IOP increases the likelihood of a correct diagnosis, but it is not necessary to make the diagnosis because it can occur without glaucoma. In the United States, around one-third of all open-angle glaucoma cases are low-tension (low-pressure) or normal-pressure glaucomas (glaucoma occurring with IOP 21 mmHg), which are much more prevalent in Asia.
Screening
Primary care physicians can assess visual fields using frequency-doubling technology (FDT) perimetry and ophthalmoscopic examination of the optic nerve to screen for glaucoma. Using a desktop device, FDT perimetry can test for glaucoma-related visual field aberrations in 2 to 3 minutes per eye. IOP measurement is important, however screening with IOP alone has poor sensitivity, specificity, and positive predictive value. Every one to two years, patients over the age of 40 and those who are at risk for developing open-angle or angle-closure glaucoma should undergo a thorough eye exam.
Treatment
The damage caused by glaucoma can’t be reversed. But treatment and regular checkups can help slow or prevent vision loss, especially if you catch the disease in its early stages.
Glaucoma is treated by lowering intraocular pressure. Treatment options include prescription eye drops, oral medicines, laser treatment, surgery or a combination of approaches.
Eyedrops
Glaucoma treatment often starts with prescription eye drops. Some may decrease eye pressure by improving how fluid drains from your eye. Others decrease the amount of fluid your eye makes. Depending on how low your eye pressure needs to be, you may be prescribed more than one eye drop.
Prescription eye drop medicines include:
- Prostaglandins. These increase the outflow of the fluid in your eye, helping to reduce eye pressure. Medicines in this category include latanoprost (Xalatan), travoprost (Travatan Z), tafluprost (Zioptan), bimatoprost (Lumigan) and latanoprostene bunod (Vyzulta).Possible side effects include mild reddening and stinging of the eyes, darkening of the iris, darkening of the pigment of the eyelashes or eyelid skin, and blurred vision. This class of drug is prescribed for once-a-day use.
- Beta blockers. These reduce the production of fluid in your eye, helping to lower eye pressure. Examples include timolol (Betimol, Istalol, Timoptic) and betaxolol (Betoptic S).Possible side effects include difficulty breathing, slowed heart rate, lower blood pressure, impotence and fatigue. This class of drug can be prescribed for once- or twice-daily use depending on your condition.
- Alpha-adrenergic agonists. These reduce the production of the fluid that flows throughout the inside of your eye. They also increase the outflow of fluid in your eye. Examples include apraclonidine (Iopidine) and brimonidine (Alphagan P, Qoliana).Possible side effects include irregular heart rate, high blood pressure, fatigue, red, itchy or swollen eyes, and dry mouth. This class of drug is usually prescribed for twice-daily use but sometimes can be prescribed for use three times a day.
- Carbonic anhydrase inhibitors. These medicines reduce the production of fluid in your eye. Examples include dorzolamide and brinzolamide (Azopt). Possible side effects include a metallic taste, frequent urination, and tingling in the fingers and toes. This class of drug is usually prescribed for twice-daily use but sometimes can be prescribed for use three times a day.
- Rho kinase inhibitor. This medicine lowers eye pressure by suppressing the rho kinase enzymes responsible for fluid increase. It is available as netarsudil (Rhopressa) and is prescribed for once-a-day use. Possible side effects include eye redness and eye discomfort.
- Miotic or cholinergic agents. These increase the outflow of fluid from your eye. An example is pilocarpine (Isopto Carpine). Side effects include headache, eye ache, smaller pupils, possible blurred or dim vision, and nearsightedness. This class of medicine is usually prescribed to be used up to four times a day. Because of potential side effects and the need for frequent daily use, these medicines are not prescribed very often anymore.
Because some of the eye drop medicine is absorbed into your bloodstream, you may experience some side effects unrelated to your eyes. To minimize this absorption, close your eyes for 1 to 2 minutes after putting the drops in. You also may press lightly at the corner of your eyes near your nose to close the tear duct for 1 or 2 minutes. Wipe off any unused drops from your eyelid.
You may have been prescribed multiple eye drops or need to use artificial tears. Make sure you wait at least five minutes in between using different drops.
Oral medications
Eye drops alone may not bring your eye pressure down to the desired level. So your eye doctor may also prescribe oral medicine. This medicine is usually a carbonic anhydrase inhibitor. Possible side effects include frequent urination, tingling in the fingers and toes, depression, stomach upset, and kidney stones.
Surgery and other therapies
Other treatment options include laser therapy and surgery. The following techniques may help to drain fluid within the eye and lower eye pressure:
- Laser therapy. Laser trabeculoplasty (truh-BEK-u-low-plas-tee) is an option if you can’t tolerate eye drops. It also may be used if medicine hasn’t slowed the progression of your disease. Your eye doctor also may recommend laser surgery before using eye drops. It’s done in your eye doctor’s office. Your eye doctor uses a small laser to improve the drainage of the tissue located at the angle where the iris and cornea meet. It may take a few weeks before the full effect of this procedure becomes apparent.
- Filtering surgery. This is a surgical procedure called a trabeculectomy (truh-bek-u-LEK-tuh-me). The eye surgeon creates an opening in the white of the eye, which also is known as the sclera. The surgery creates another space for fluid to leave the eye.
- Drainage tubes. In this procedure, the eye surgeon inserts a small tube in your eye to drain excess fluid to lower eye pressure.
- Minimally invasive glaucoma surgery (MIGS). Your eye doctor may suggest a MIGS procedure to lower your eye pressure. These procedures generally require less immediate postoperative care and have less risk than trabeculectomy or using a drainage device. They are often combined with cataract surgery. There are a number of MIGS techniques available, and your eye doctor will discuss which procedure may be right for you.
After your procedure, you’ll need to see your eye doctor for follow-up exams. And you may eventually need to undergo additional procedures if your eye pressure begins to rise or other changes occur in your eye.
Treating acute angle-closure glaucoma
Acute angle-closure glaucoma is a medical emergency. If you’re diagnosed with this condition, you’ll need urgent treatment to reduce the pressure in your eye. This generally will require treatment with medicine and laser or surgical procedures.
You may have a procedure called a laser peripheral iridotomy. The doctor creates a small hole in your iris using a laser. This allows fluid to flow through the iris. This helps to open the drainage angle of the eye and relieves eye pressure.