Glaucoma

Glaucoma is a disease of the optic nerve. The major risk factor for most glaucomas is increased intraocular pressure of aqueous fluid in the aqueous chamber of the eye. One person may develop nerve damage at a relatively low pressure, while another person may have high eye pressure for years and yet never develop damage. Untreated glaucoma leads to permanent damage of the optic nerve and resultant visual field loss, which can progress to blindness.

The loss of visual field often occurs gradually over a long time and may only be recognized when it is already quite advanced. Once lost, this damaged visual field can never be recovered. It is the second leading cause of blindness in the world.

Primary open-angle glaucoma - This is caused by blockage where the aqueous fluid in the eye drains out. Because the microscopic passage ways are blocked, the pressure builds up in the eye and causes imperceptible very gradual vision loss. Peripheral vision is affected first but eventually the entire vision will be lost if not treated, leading to total blindness. Diagnosis is made by looking for cupping of the optic nerve. The goal of treatment with eye drops is to increase fluid outflow or decreasing fluid inflow.
Primary angle-closure glaucoma - This is caused by contact between the iris and angle of the eye, which in turn obstructs outflow of the aqueous fluid from the eye, gradually causing damage to the outflow function, causing the pressure rises. In over half of all cases, prolonged contact between iris and angle causes the formation of synechiae (effectively "scars"). These cause permanent obstruction of aqueous outflow. In some cases, pressure may rapidly build up in the eye causing acute pain and redness. In this situation the vision may become blurred, and halos may be seen around bright lights. Accompanying symptoms may include headache and vomiting. Diagnosis is made from physical signs and symptoms: pupils mid-dilated and unresponsive to light, cornea edematous (cloudy), reduced vision, redness, and pain. However, the majority of cases are asymptotic. Prior to very severe loss of vision, these cases can only be identified by examination, generally by an eye care professional. Once any symptoms have been controlled, the first line treatment is via laser. The goal of treatment is to reverse and prevent contact between iris and angle.

Risk factors
In some populations only 50% of patients with primary open angle glaucoma have elevated ocular pressure. Those of African descent are three times more likely to develop primary open angle glaucoma. Higher age, thinner corneal thickness, and nearsightedness are also at risk. People with a family history of glaucoma have about a six percent chance of developing glaucoma.

Many Asian groups, such as Mongolian, Chinese, Japanese, and Vietnamese, are prone to developing angle closure glaucoma due to their shallower anterior chamber depth, with the majority of cases of glaucoma in this population consisting of some form of angle closure. Inuit also have a twenty to forty times higher risk than Caucasians of developing primary angle closure glaucoma.

Women are three times more likely than men to develop acute angle-closure glaucoma due to their shallower anterior chambers.

Regarding the secondary glaucomas, risk factors include prolonged use of steroids and conditions that severely restrict blood flow to the eye, such as severe diabetic retinopathy, central retinal vein occlusion, ocular trauma,and uveitis.

Those at risk for glaucoma are advised to have a dilated eye examination at least once a year.

Diagnosis
Testing for glaucoma should include measurements of the intraocular pressure via tonometry, anterior chamber angle examination or gonioscopy, pachymetry to measure the cornea thickness, and examination of the optic nerve to look for any visible damage or change in the cup-to-disc ratio, rim appearance, and vasculature. A formal visual field test should also be performed. The retinal nerve fiber layer should be assessed with statistical imaging techniques such as scanning laser ophthalmoscopy or Heidelberg Retina Tomography (HRT). Examination for glaucoma also could be assessed with more attention given to sex, race, history of drugs use, refraction, inheritance and family history.

Management
The modern goals of glaucoma management are to avoid nerve damage and preserve visual field and total quality of life for patients with minimal side effects. This requires appropriate treatment and follow-up examinations. Glaucoma should be monitored via follow-up examination once every 3 months. These routine follow-ups provide the opportunity to routinely monitor pressure in the eye, and well as carry out testing to note for any progrssion of visual problems associated with glaucoma. Visual fields, gonioscopy, and HRTs should be performed on a yearly basis. Fundus photography should be performed every 6 months to note any changes in the optic nerve.

Intraocular pressure can be lowered with medication, usually eye drops. There are several different classes of medications to treat glaucoma with several different medications in each class. Although intraocular pressure is only one of the major risk factors for glaucoma, lowering it with pharmaceuticals and/or surgical techniques is currently the mainstay of glaucoma treatment.

Poor compliance with medications and follow-up visits is a major reason for vision loss in glaucoma patients. Patient education and communication must be ongoing to sustain successful treatment plans for this lifelong disease with no early symptoms.

Commonly used medications
Prostaglandin analogs like Xalatan, Travatan, and Lumigan increase uveo-scleral outflow. These drops should be taken once daily, before bedtime.

Topical beta-adrenergic receptor antagonists such as Betagan, Betoptic, Timoptic and Istalol decrease aqueous fluid production. These drops should be taken twice daily, once in the morning and one a night.

Alpha2-adrenergic agonists such as Alphagan work by a dual mechanism, decreasing aqueous fluid production and increasing uveo-scleral outflow. These drops should be taken twice daily, once in the morning and one a night.

Combigan is a combination beta-adrenergic receptor antagonist/alpha2-adrenergic agonist that combines the effects of both medications into one effective dosage. It decrease aqueous fluid production and increases uveo-scleral outflow. These drops should be taken twice daily, once in the morning and one a night.

Carbonic anhydrase inhibitors like Trusopt and Azopt lower secretion of aqueous fluid. These drops should be taken three time daily. Cosopt combines the carbonic anhydrase inhibitor Trusopt with the beta-adrenergic receptor antagonist Timoptic for a more potent effect of decreasing aqueous fluid production. These drops should be taken twice daily, once in the morning and one a night.

Natural compounds
Natural compounds of research interest in glaucoma prevention or treatment include fish oil and omega 3 fatty acids, bilberries, vitamin E, carnitine, coenzyme Q10, curcurmin, Salvia miltiorrhiza, dark chocolate, erythropoietin, folic acid, Ginkgo biloba, Ginseng, L-glutathione, grape seed extract, green tea, magnesium, melatonin, methylcobalamin, N-acetyl-L cysteine, pycnogenols, resveratrol, quercetin and salt.

Laser surgery
Laser trabeculoplasty may be used to treat open angle glaucoma, but it is a temporary solution, not a cure. An argon or YAG laser spot is aimed at the trabecular meshwork in the aqueous chamber to stimulate opening of the mesh to allow more outflow of aqueous fluid. Usually, half of the angle is treated at a time.

YAG Laser peripheral iridotomy may be used in patients susceptible to or affected by angle closure glaucoma or pigment dispersion syndrome. During laser iridotomy, laser energy is used to make a small full-thickness opening in the iris. This opening equalizes the pressure between the front and back of the iris correcting any abnormal bulging of the iris. In people with narrow angles, this can uncover the trabecular meshwork. In some cases of intermittent or short-term angle closure this may lower the eye pressure. Laser iridotomy reduces the risk of developing an attack of acute angle closure. In most cases it also reduces the risk of developing chronic angle closure or of adhesions of the iris to the trabecular meshwork.

Trabeculectomy
A partial thickness flap is made in the wall of the eye, and a window opening made under the flap to remove a portion of the trabecular meshwork. The flap is then sutured loosely back in place. This allows fluid to flow out of the eye through this opening, resulting in lowered intraocular pressure and the formation of a bleb or fluid bubble on the surface of the eye. Scarring can occur around or over the flap opening, causing it to become less effective or lose effectiveness altogether. One person can have multiple surgical procedures of the same or different types.

The previous information is based on a current review of the literature and it is updated on a regular basis. We tailor our treatment plan to each individual.