Glaucoma is a group of diseases that can damage the eye’s optic nerve.
The optic nerve connects with the retina and is made up of many nerve fibers. Thus, it sends signals and information from the retina to the brain, where they are decoded into images that we can see.
A healthy eye continuously produces a small amount of a light-colored liquid, known as aqueous humor, whose functions are extremely important – nutrition, leveling the IOP and keeping the shape of the eye. If this liquid does not drain appropriately, it can lead to a buildup of pressure inside the eye, resulting in progressive damage to the optic nerve.
Untreated glaucoma can lead to blindness. It is estimated that half the patients who suffer from this condition are not aware of it. Often there are no symptoms at first, but early and appropriate treatment can help protect your eyes against vision loss.
Daytona color image of an optic nerve with glaucoma
Daytona color image of a normal optic nerve
TYPES OF GLAUCOMA
– Open-angle glaucoma: it appears when the trabecular meshwork (the drain of the eye) becomes less efficient in draining the liquid (aqueous humor). In this manner, fluid pressure inside the eye slowly rises and over time, it can damage the eye’s optic nerve. Damage to the optic nerve can occur with different levels of pressure in different people. It is the eye doctor who should establish which is the ideal level of pressure for each patient. On the other hand, measuring the IOP is not the only relevant information to be gathered when dealing with glaucoma. It is essential to analyze vision and examine the optic nerve for an appropriate diagnosis, and once it has been made, for correct control.
– Normal-tension glaucoma: normal eye pressure ranges from 12-21 mmHg. However, there are eyes with low intraocular pressure which still suffer from damage to the optic nerve and visual field loss (usually with the presence of shadows or black spots in vision). In the same way, ocular hypertension is a condition in which the eye pressure exceeds 21 mmHg, but with no damage to the optic nerve nor visual field. These conditions may be signalling glaucoma and for this reason they must be closely monitored.
– Angle-closure glaucoma: also called acute or chronic-closure glaucoma. This type of glaucoma appears when the angle between the iris (what gives color to our eyes) and the cornea is too narrow, resulting in poor drainage of the trabecular meshwork. If this angle gets completely blocked, intraocular pressure may suffer a sudden increase leading to an ACUTE ANGLE-CLOSURE CRISIS. Symptoms include severe pain and nausea, as well as redness of the eye and blurred vision. This condition is a MEDICAL EMERGENCY and requires urgent treatment.
– Secondary glaucoma: when it results from another eye condition or disease, such as: eye injuries, inflammation, steroid drugs, eye tumors, pseudoexfoliation syndrome, pigment dispersion syndrome, etc.
-Congenital glaucoma: it is is a rare type of glaucoma that develops in infants and young children (between birth and age 3). In congenital glaucoma, children are born with a defect in the angle of the eye that blocks the normal drainage of aqueous humor. In time, parents start realizing that the child is over-sensitive to light (photophobia), there is excessive tearing and that the child tends to have his or her eyes closed most of the time. As the disease develops, eyes start to look cloudy and bigger than normal.
Risk factors to develop glaucoma are:
– migraines, diabetes, low blood pressure
– black or hispanic heritage
– Asian heritage (Asians are at increased risk of angle closure glaucoma)
– hyperopia (farsightedness), at increased risk of angle closure glaucoma
– myopia (nearsightedness)
– corneas that are thin in the center
– high intraocular pressure (IOP)
– no attendance to eye medical check-ups
Specific tests for diagnosing glaucoma are:
– Measuring intraocular pressure (tonometry): after applying the anesthetic and fluorescein drops, the inner eye pressure (IOP) will be measured with a Goldmann Applanation Tonometer. A Pneumatonometer, which does not require the application of eye drops, can be also used for certain occasions. The Perkins tonometer is to be used on patients with reduced mobility or who are hospitalized and cannot be seated. None of these procedures causes pain.
– Eye’s drainage angle examination (GONIOSCOPY): this diagnostic exam helps determine whether the angle where the iris meets the cornea is open and wide or narrow and closed. During the exam, eye drops are used to numb the eye. A hand-held contact lens is gently placed on the eye. This contact lens has a mirror that shows the doctor if the angle between the iris and cornea is closed and blocked (a possible sign of angle-closure or acute glaucoma) or wide and open (a possible sign of open-angle, chronic glaucoma). This exam allows the eye doctor to determine the most appropriate treatment for each patient.
– Ophthalmoscopy (examine your optic nerve for glaucoma damage)
– Perimetry (visual field test)
– DTC (Diurnal tension curve)
– Pachymetry: a simple, painless test to measure the thickness of your cornea
– OCT (Optical Coherence Tomography) non-invasive imaging test that takes cross-section pictures of your optic nerve, macula and anterior segment.
– Color retinography of both optic nerves
Glaucoma treatment will depend on your specific type of glaucoma and its the severity.
– Eyedrops: there is a number of eyedrops which can be used to treat glaucoma. It is of the utmost importance to let your doctor know if you are under any medication for another pathology, such as diabetes, heart problems, blood disorders, aspirins, psychiatric medication, etc. in order to prescribe the most appropriate medication for you. Eyedrops must be taken every day. Treatment mustn’t be interrupted and in case of any problem, see your doctor immediately.
– Periferal Iridotomy with Yag Laser: indicated treatment for acute glaucoma and chosen also as preventive treatment for predisposed patients (narrow angles). It consists in opening a small hole in the most peripheral part of the iris, to facilitate drainage of the aqueous humor. It is performed with eyedrops and a special magnifying glass. After the procedure, anti-inflammatory drops are prescribed for some days. Sometimes more than one session is needed.
– Laser peripheral iridotomy (LPI) with argon laser:: it works by making small holes in the periphery of the iris, allowing it to fall back from the fluid channel and helping the fluid drain. It is usually prescribed for Plateau Iris Syndrome and sometimes for treating people with closed-angle glaucoma.
– Trabeculectomy: it is the most common laser surgery to treat glaucoma and it is performed when all previous treatments had no success in lowering the IOP or when the disease shows progression. Laser trabeculoplasty can also be used as a first line of treatment for patients who are unwilling or unable to use glaucoma eye drops. During the surgery, a laser makes tiny, evenly spaced burns in the white of the eye (sclera) to create a trap-door, which is then stitched in a way that prevents aqueous humour from draining too quickly. This is the most common surgical procedure for patients who suffer from glaucoma, but the way it is performed is constantly evolving. Trabeculectomy surgery is often performed under topical anesthesia, though it may also be performed under peribulbar anesthesia.. It is an outpatient surgery and patients usually leave the OR with a compression eye patch on the operated eye. During the surgery, some specific drugs (antimetabolites) may be applied to the surface of the eye for a brief period of time to reduce scarring. After surgery care is extremely important, the stitches do not dissolve and are usually removed in the clinic two to three weeks after surgery.
– Glaucoma drainage devices (Ahmed Valvle): traditionally, tube shunts were used to control eye pressure in patients in whom traditional eye surgery to relieve fluid pressure had previously failed, or in patients who have had previous surgeries or trauma. Tube shunts have also been successful in controlling eye pressure in other types of glaucoma, such as glaucoma associated with uveitis or inflammation, neovascular glaucoma. In recent years, some surgeons are using tube shunts or glaucoma drainage devices as first-line surgery. The Ahmed glaucoma valve is the most commonly used type of shunt. The shunt is shaped like a miniature computer mouse with a tube at the end of it. Because the various tube shunts have different sizes, features, and surgical techniques associated with them, the decision of which tube shunt to have implanted depends on your particular situation and your surgeon’s preference. The tube shunt is made of silicone or polypropylene, a material that won’t break down in the body. The procedure is done under peribulbar anesthesia. The most frequently chosen quadrant of tube placement for the first device is the superotemporal but additional valves may be placed in other quadrants. These kind of valves may go through a hypertension period between week 4 and week 16 after the surgery. It is important to be on the alert during this phase, to incorporate supplemental glaucoma eye drops if need be.
– Schlemm Canal Surgeries: they include canaloplasty, Trabectome and the iStent procedure, which has been recently approved in our country but its use dates back all over the world. These procedures are prescribed only for very specific cases of glaucoma. Your doctor will tell you in due time the best option for your particular situation.