There are instances where the meshwork does not function due to inflammation, or the presence of white blood cells, from various causes. Inflammation of any sort is called “-itis,” but the reason for the inflammation may or may not be known. So, a “trabeculitis” may cause the meshwork to malfunction, and the pressure of the eye to increase despite an open angle, due to inflammation from infection (for example, herpes), after surgery, from autoimmune diseases, or unknown causes (Posner-Schlossman syndrome).
Steroid-induced glaucoma is a special case of reversible elevation of pressure in the eye. Steroids, either by eye drops or by mouth, have the potential to cause glaucoma by stabilizing cell membranes of the cells in the meshwork that have to “catch and release” the aqueous. Therefore, the function is slowed. People who have a tendency for elevated eye pressure with short or minimal exposure to steroids are termed “steroid responders,” and some studies indicated that these people may even be at greater risk for OAG as they age.
Narrow angle (angle-closure) glaucoma (NAG) is caused by a narrowing of the access to the meshwork lying in the angle between the iris and the cornea. NAG can happen intermittently, bouncing the pressure in the eye up and down (chronic narrow angle glaucoma, or CNAG); or it can occur in the form of a sudden, painful attack of severely elevated pressure. People who are at risk for NAG can have a short eye, with a narrower angle, or a developing cataract, which pushes the iris forward and narrows the angle, or a thick iris, which is more common in the Asian populations.
There are rare reactions to medications that either dilate the iris of a susceptible person (dilating drops, allergy medications, certain antidepressants) or cause a shift in the musculature of the ciliary body (Topamax) that can cause a narrow angle attack. An attack of narrow angle glaucoma causes a quick, severe, and painful rise in the intraocular pressure (IOP). Its symptoms are pain, redness, colored haloes around lights, and sometimes nausea and vomiting. Angle-closure glaucoma is an emergency. You should not wait to contact your ophthalmologist if this occurs, even if the symptoms clear up.
If you have had acute glaucoma in one eye, you are at risk for an attack in the second eye, and your doctor is likely to recommend preventive treatment (see below).
Congenital glaucoma may occur in families (hereditary). It is present at birth, and is the result of the abnormal development of the fluid outflow channels in the eye. Other structures in the eye may also be affected, such as the cornea, the iris and the lens. The hallmark of congenital glaucoma is a cloudy cornea, due to the aqueous being forced into it by the elevated pressure in the eye. The infant may also have tearing, redness and appear to be sensitive to light.
An examination of the eye may be used to diagnose glaucoma. However, checking the intraocular pressure alone (tonometry) is not enough because eye pressure changes. The doctor will need to examine the inside of the eye by looking through the pupil, often while the pupil is dilated. Additional tests are used to detect glaucoma.
Remember that the hallmark of glaucoma of any type is pressure in the eye sufficient to damage the optic nerve. Usually this means IOP that is elevated above the range of 8-22, but it also can mean that the vascular supply or the supporting structures or the optic nerve make it more susceptible to damage at “normal” IOP.
Usually the doctor will perform a complete examination of the eyes.
Visual Acuity Visual field measurement.
This measures the subjective functioning of the nerve fiber layer and can show characteristic loss of the peripheral vision. It can clearly indicate the presence of glaucoma in a person who is a good test taker (specificity), but it may not detect glaucoma until there is already considerable damage (not sensitive). It is also subject to a number of potential sources of error, like patient reliability and attentiveness, or problems of the eye like cataract or macular degeneration not related to glaucoma.Pupillary reflex response, which will not be equal if one eye is more damaged from glaucoma than the other.
Retinal Examination and Your Eye Doctor
Sometimes, the diagnosis of glaucoma is not clear. If someone walks into the exam with an IOP of 40, that’s an easy diagnosis. But if someone has no symptoms, a strong family history of OAG, is over 50 and he has a borderline eye pressure (say, 23) and a large cup-to-disc ratio (C/D), what should the physician do? What is the visual field is not reliable, and a cataract makes the nerve fiber layer analysis less than optimal? Sometimes, the answer can only be determined over the course of several visits, over months or even years. All the while, the patient may not have any symptoms at all!
Eye Correction Surgery Treatment
The objective of eye correction surgery is to reduce intraocular pressure. Depending on the type of glaucoma, this is achieved with medications or by surgery.
Open-angle glaucoma treatment:
There are several classes of eye drop medications that can be used to decrease the IOP, either by slowing down the formation of aqueous, or by increasing its outflow. All medications have their specific benefits and risks, and it is important that you discuss these with your doctor for any medication suggested. Sometimes, more than one medication may be necessary. Oral medications are available to decrease IOP, but they have systemic effects that usually make them a last choice.
A type of laser procedure is available (SLT, selective laser trabeculoplasty) that seems to be safe and effective for milder cases of glaucoma. It works by causing a low grade inflammation from absorption of green light by melanin pigment-containing cells in the trabecular meshwork. The cells responding to the inflammation “clean house”, and lay down new collagen, much like the cells of the skin responding to certain rejuvenating lasers.
More aggressive IOP control can be achieved using various types of procedures and devices to drain the aqueous, bypassing the meshwork entirely, or physically changing the shape of the meshwork to open the fluid outflow channels (ligature procedures). Again, the various options entail different risks and benefits and deserve a thorough discussion with your surgeon.
Narrow angle glaucoma treatment:
Chronic angle closure glaucoma may only be noted by the patient by occasional blurring of vision and redness, but is detected by the doctor by a narrowing of the outflow angle on gonioscopy. The treatment is the creation of one or two holes in the iris with a laser (iridotomy). This equalizes the pressure on either side of the iris and has the effect of the iris falling back just a bit, but sufficient to prevent an acute NAG attack. It is a very safe procedure.
Acute angle-closure attack, with pain, blurring from corneal edema from elevated IOP, and redness of the involved eye, is a medical emergency. Blindness will occur in a few days if it is not treated. Both drops and oral medications are used to lower the pressure, before performing iridotomy as soon as corneal clearing allows.
Congenital glaucoma treatment:
This form of glaucoma is almost always treated with eye surgery to open the outflow channels of the angle, under general anesthesia. If a cataract is present or corneal scarring, that might be addressed as well with an eye doctor.
Open-angle glaucoma: You can manage open-angle glaucoma and almost always preserve your vision, but the condition cannot be cured. It’s important to carefully follow up with your doctor. With good care, most patients with open angle glaucoma will not lose vision.
Angle-closure glaucoma: Rapid diagnosis and treatment of an attack is the key element to preserving vision. Seek emergency care if you have the symptoms of angle-closure attack.
Congenital glaucoma: Early diagnosis and treatment is important. The baby’s prognosis depends on other problems involving the eye. The follow-up for evaluation and treatment is crucial for a good visual outcome.
Call your health care provider if you have severe eye pain or a sudden loss of vision, especially loss of peripheral vision.
Make an appointment with your health care provider if you have risk factors for glaucoma and have not been screened for the condition.
Preventing Open-Angle Glaucoma
As most eye doctors and lasik eye surgeons will tell you, there is no way to prevent open-angle glaucoma, but you can prevent vision loss from the condition. Early diagnosis and careful management are the keys to preventing vision loss.
Most people with open-angle glaucoma have no symptoms. Everyone over age 40 should have an eye examination at least once every 5 years, if not more, if they find themselves in a high-risk group. Those in high-risk groups include people with a family history of open-angle glaucoma, and people of African or Latino heritage. Studies are equivocal whether the presence of diabetes is a risk factor for glaucoma. Hypertension does NOT seem to be a risk factor.
Glaucoma & Laser Eye Surgery
People at high risk for acute glaucoma may opt to undergo laser iridotomy before having an attack. Patients who have had an acute episode in the past may have the procedure to prevent a recurrence and should consider having a preventative iridotomy in the fellow eye. Again, this is a very safe procedure.