What is glaucoma?
Glaucoma is an eye condition where abnormally high pressure inside your eye can result in optic nerve damage, which may eventually lead to blindness. Glaucoma damage is permanent and cannot be reversed.
In a healthy eye, a clear fluid called aqueous humor is continuously produced and circulates inside the front part of your eye. Typically, this fluid will drain in equal amounts with what is produced in order to maintain a safe intraocular pressure (IOP). If the amount of fluid produced is greater than the amount of fluid that drains, the IOP increases and pushes against the optic nerve. When the pressure remains too high for too long, the optic nerve tissue can be damaged - causing blind spots. IOP rises and falls throughout the day, so a single pressure check may not indicate the presence of glaucoma. It is important to have a dilated eye exam along with special testing so the optic nerve can be examined by an ophthalmologist and properly diagnosed/treated.
There are several different types of glaucoma:
- Open-Angle Glaucoma - This is the most common form of glaucoma and occurs when the drainage system in the eye becomes less efficient, causing fluid to build up and IOP to rise.
- Low-Tension Glaucoma - This form of glaucoma is similar to open-angle glaucoma, but can cause optic nerve damage in affected patients even when the IOP is in the range considered to be "normal".
- Narrow-Angle Glaucoma - Also known as "angle closure glaucoma", this form of glaucoma happens when the iris (colored part of the eye) is too close to the drainage angle inside the eye, causing a blockage of the drain and a rapid increase in IOP. An angle-closure event is a medical emergency and requires urgent treatment.
- Secondary Glaucoma - This form of glaucoma can present as a result of another eye condition which interferes with the functionality of the drainage system causing the IOP to rise. Causes of secondary glaucoma can include: eye injury, abnormal blood vessel growth, use of medications containing a steroid, and inflammation of the eye.
- Congenital Glaucoma - This is a rare form of glaucoma which affects infants and young children - often resulting in blindness if not diagnosed and treated early.
- Glaucoma Suspect - Some patients don't have signs of current optic nerve damage, but still need to be closely monitored. There are two situations in which someone might be classified as a glaucoma suspect: 1. They have a normal IOP, but the appearance of the optic nerve or test results may look suspicious for glaucoma. 2. Known as "ocular hypertension", they can have a higher-than-normal IOP, but have no other signs (the appearance of the optic nerve or test results are normal).
Risk factors for developing glaucoma include: being over the age of 40, having a family history of glaucoma, having African/Hispanic/Asian heritage, having diabetes, migraines, high blood pressure, or other conditions that affect the whole body.
What are the symptoms of glaucoma?
With glaucoma, there are no obvious initial symptoms. Blind spots will develop in the peripheral vision and will gradually spread into the central vision as optic nerve damage progresses. These blind spots can go unnoticed until after there has already been significant damage to the optic nerve, or until damage is detected through a comprehensive eye exam.
With narrow angle glaucoma, there are usually no symptoms prior to an attack, but may include: blurred vision, halos, eye pain, and mild headache. During an angle closure attack, there may be: nausea/vomiting, headache, severe pain in the eye or around the forehead, decreased/blurry vision, and redness of the eye.
How do we treat glaucoma?
The goal of glaucoma treatment is to maintain a safe IOP in order to prevent the progression of damage to the optic nerve. Methods of treatment vary depending on the specific type and severity of the glaucoma, as well as how well it responds to treatment. Most patients can expect to be seen every 4-6 months for routine IOP checks - at least some of which will be dilated in order to view and document the appearance of the optic nerve. In addition, annual testing will measure the thickness of the nerve layer using Ocular Coherence Tomography and map out any blind spots (or lack thereof) using a visual field analyzer - allowing detection of any progression. Your doctor will determine a target IOP and the best course of treatment based on ongoing IOP readings, appearance of the optic nerve, and test results (target IOP will be different for everyone based on these factors).
The most common method and first line of treatment for most types of glaucoma is through the daily use of eye drops which will either increase the amount of fluid that drains or decrease the amount of fluid produced from within the eye. The use of more than one type of eye drop may be necessary to reach the target pressure.
Selective laser trabeculoplasty (SLT) is a low-energy laser which specifically targets cells in the drainage angle, opening up the drain work and lowering IOP by allowing fluid to drain more quickly. SLT can potentially eliminate the need for pressure-lowering eye drops, or can be used in addition to eye drops if the target pressure is not reached with the laser alone. It can also be used as a first line treatment for patients unwilling or unable to use eye drops. The effect of the SLT is not permanent and can fade over time, eventually requiring repeat laser treatments.
Endocyclophotocoagulation (ECP) is a laser procedure which lowers IOP by ablating the ciliary processes, which produce the aqueous humor. This procedure requires an incision to reach the ciliary body and is typically performed in conjunction with cataract surgery.
Narrow-angle glaucoma may require a special laser procedure called a "peripheral iridotomy" (PI). This procedure creates a small hole through the iris to improve the flow of fluid to the drainage angle. Your doctor may recommend a prophylactic PI to help prevent an angle-closure attack, or will initiate one if an attack is in progress. If a PI is unable to stop an acute attack, a "peripheral iridectomy" might be necessary, where a small piece of the iris is removed to give fluid access to the drainage angle again.
If all other methods of treatment fail to control IOP, surgery beyond laser may be required. A "trabeculectomy" creates a small filtration bleb (or reservoir) under the skin of the eye which allows the fluid to collect and reabsorb into the blood vessels around the eye. An aqueous shunt may be necessary if a trabeculectomy cannot be performed. The shunt is a small plastic tube/valve connected to a reservoir which is placed on the outside of the eye below the conjunctiva (the thin membrane that covers the white part of the eye) where the fluid is absorbed into the blood vessels.
Pressure emergencies may be treated in-office with multiple doses of oral medication and eye drops designed to lower IOP. IOP is repeatedly checked and treatment adjusted until the IOP comes back under control. It may be necessary to continue use of this medication at home, once IOP has been brought under control in the office.