What is Secondary Glaucoma?
Secondary glaucoma is caused by an underlying medical issue that increases the eye's intraocular pressure (IOP), leading to permanent optic nerve damage. The optic nerve is the communication pathway between your eye and brain.
Glaucoma can lead to serious vision changes and blindness if not treated.
The constant flow of aqueous humor, the clear liquid that gives the eye shape and nutrients, controls eye pressure.
The liquid must drain out of the eye at the same rate it comes in to maintain a constant pressure. It does this through the drainage angle. If the balance is off even slightly, IOP can increase, causing glaucoma and serious damage to the optic nerve.
The most common types of glaucoma stem from problems with the drainage angle. Primary open-angle glaucoma and acute angle-closure glaucoma result in either a slowing of the drainage rate or a blocked drain. Both types cause high intraocular pressure.
People over the age of 60 are at the highest risk of developing glaucoma. However, because an identifiable medical event triggers secondary glaucoma, it can happen at any age.
What Causes Secondary Glaucoma?
Several medical conditions that increase eye pressure can cause secondary glaucoma. These include:
- Eye injury
- Eye inflammation
- Certain medications (steroids)
- Sickle cell disease
People with diabetes are 50% more likely to develop glaucoma. Annual eye exams and maintaining healthy blood sugar levels are the best ways to prevent secondary glaucoma in people diagnosed with both type 1 and type 2 diabetes.3
Types of Secondary Glaucoma and Their Symptoms
Secondary glaucoma can be classified as either secondary open-angle glaucoma or secondary angle-closure glaucoma and may occur in one or both eyes.
The different types of secondary glaucoma are:
1. Steroid-induced glaucoma
Steroids are a common medication that treat and prevent inflammation. Steroids can be prescribed as:
- Eye drops
- Topical ointment
- Oral medication
- Eye injections
- Intravenously (IV)
While steroids are highly effective as an anti-inflammatory, the side effects from prolonged use can have adverse consequences. This includes an increase in eye pressure, leading to secondary glaucoma.
Steroid-induced glaucoma is open-angle glaucoma caused by interference with the outflow of aqueous humor. This disturbance causes a slow increase in eye pressure that can damage the optic nerve and result in permanent vision changes.
Steroid-induced glaucoma can happen at any age, including in infants. Prolonged use of steroids (longer than 3 weeks) can lead to IOP increase. While the increase in eye pressure is treatable, damage to the optic nerve is irreversible.5
Because the increase in eye pressure is slow, steroid-induced glaucoma is typically asymptomatic, and only an eye doctor can discover it during a routine eye exam. Some people may notice blurry vision as an early warning sign. Eyebrow pain has also been associated with IOP. However, these symptoms only occur if IOP is very high.
Stopping the use of steroids or reducing the dose is the first line of treatment for steroid-induced glaucoma. Glaucoma medications can help lower eye pressure.
2. Trauma-induced glaucoma
Trauma-induced glaucoma is caused by an eye injury that usually involves blunt trauma (bruising of the eye) or penetrating eye injury (sharp object or flying debris).
Other factors that increase the risk for more severe eye injuries include:
- Severe myopia (nearsightedness)
- Previous injury
- Eye infection
- Prior surgery
Intraocular pressure can occur immediately following the eye injury or develop over time.
Glaucoma caused by blunt trauma, such as a sports-related injury, causes damage to the ciliary body (where the eye fluid is produced), leading to bleeding. Bleeding can clog the drainage system, increase eye pressure, and damage the optic nerve.
Glaucoma from a penetrating eye injury may develop after the wound heals. Tissue damage and scarring can block the drainage canal, gradually causing IOP to rise over time.
Symptoms of traumatic glaucoma depend on the nature of the injury and how fast eye pressure increases. Often glaucoma symptoms (blurry vision, blind spots) don't develop until there is damage to the optic nerve, which can take months or years.
After an eye injury, medical professionals will typically prescribe preventive medications (glaucoma medication, steroids, and antibiotics) to reduce IOP and prevent inflammation and infection.
3. Uveitic glaucoma
Uveitis, inflammation of the eye's middle layer (uvea), causes uveitic glaucoma. Twenty percent of uveitis cases will lead to uveitic glaucoma.7
Common causes of uveitis include:
- Autoimmune disorder
Debris from inflammation can clog the eye's drainage system, leading to an increase in eye pressure. Scar tissue can also disrupt the outflow of eye fluid, which often leads to IOP increase.
Symptoms of uveitis include:
- Light sensitivity
- Blurry vision
Because high eye pressure usually develops over time, uveitic glaucoma may not produce symptoms until permanent damage to the optic nerve occurs. Treating the underlying cause of uveitis is the first line of treatment for uveitic glaucoma.
4. Neovascular glaucoma
New blood vessels growing over the angle or drainage system cause neovascular glaucoma. Growth occurs where the iris (colored part of the eye) meets the cornea (transparent front part of the eye). This can cause angle blockage, which then disrupts the fluid flow and triggers an increase in eye pressure, eventually leading to glaucoma.
Diabetes is a common cause of neovascular glaucoma. Other causes include:
- Chronic retinal detachment
- Ocular ischemic syndrome (decreased blood flow to the eye)
New blood vessel growth can occur when blood flow to the eye slows down. The eye releases chemicals called vascular endothelial growth factor (VEGF) to compensate for low blood flow, which prompts new blood vessel growth to supply the eye with more oxygen.
Symptoms of neovascular glaucoma can include vision loss, pain, and redness. However, the early stages of the disease may not produce any symptoms. Annual eye exams are essential for people with diabetes and for those at risk for neovascular disease.
5. Exfoliative glaucoma
Exfoliative glaucoma, also called pseudoexfoliation, is the most common secondary glaucoma. Its primary cause is a buildup of flakey protein in the drainage system of the eye, which can cause an increase in eye pressure.
People from Russia, Scandinavian countries (Sweden, Finland, Norway), and Greece are at a higher risk of developing exfoliative glaucoma.
Exfoliative glaucoma is associated with higher and faster rates of increased eye pressure, making treatment and management more difficult than other types of secondary glaucoma.
As with other forms of glaucoma, people with exfoliative glaucoma might not have any symptoms until there is damage to the optic nerve, which results in vision loss.
6. Pigmentary glaucoma
Pigmentary glaucoma stems from pigmentary dispersion syndrome, which involves pigment flaking off the iris into the aqueous humor.
Pigmentary glaucoma occurs when these pigments block the eye's drainage system, increasing eye pressure. Pigmentary dispersion syndrome leads to glaucoma 30% of the time.10
Vigorous exercise, such as jogging or playing basketball, has been linked to pigmentary glaucoma. This type of secondary glaucoma occurs more frequently in young Caucasian males who are nearsighted.
Early signs of pigmentary glaucoma include blurry vision and halos around lights. Eye doctors treat it with medication that lowers eye pressure.
Secondary Glaucoma vs. Open Angle Glaucoma
Primary open-angle glaucoma is the most common type of glaucoma. Open-angle means that the drainage system is open.
Open-angle glaucoma is often associated with a gradual progression of increased IOP that is caused by a slowing drainage rate, similar to a clogged drain.
Many types of secondary glaucoma are also classified as secondary open-angle glaucoma, depending on how the drainage system is affected. These include:
- Steroid-induced glaucoma
- Pigmentary glaucoma
- Exfoliation glaucoma
- Traumatic glaucoma
When the drainage system is completely blocked, this is called acute angle closure glaucoma, which is a medical emergency.
Treatment for Secondary Glaucoma
The cause and type of secondary glaucoma will determine the treatment plan. The initial goal of treating glaucoma is to get the intraocular pressure down to a normal level through daily eye drops and other medications.
If medication does not effectively lower eye pressure, an eye doctor might recommend laser or traditional surgery.
These surgeries may include:
- Trabeculoplasty. Improves the drainage angle for better fluid flow.
- Iridotomy. Creates a small hole in the iris to improve fluid drainage.
- Trabeculectomy. Creates a new drainage channel.
- Glaucoma drainage device. Implants a tiny drainage tube.
Secondary glaucoma is caused by an underlying medical condition that increases eye pressure. If not treated, glaucoma can cause vision loss and blindness.
The most common causes of secondary glaucoma are diabetes, inflammation, prolonged steroid use, and eye injury.
Symptoms of secondary glaucoma may not present in the early stages of the disease. Late-stage symptoms, when there is permanent damage to the optic nerve, can include blurry vision, redness, pain, blind spots, and halos.
Initial treatment for secondary glaucoma focuses on finding the root cause of the IOP increase and using medication to lower it. Laser therapy and traditional surgery can treat glaucoma when medication alone is ineffective.
An annual comprehensive eye exam from a licensed eye doctor is the best way to catch glaucoma early.
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