Glaucoma is a condition that affects the optic nerve which is responsible for transmitting perceived images from the retina to the brain. If not treated, damage to the optic nerve will cause blind spots which are undetectable in the early stages. As the disease progresses, loss of side vision occurs followed by loss of central vision and even blindness as the end result.
Glaucoma is a leading cause of blindness in the United States among adults. However, this can be prevented with early detection and treatment. In many instances there are no symptoms. Optic nerve damage is irreversible when it occurs. For these reasons it is very important for all adults to have regular eye examinations in order to be screened for this condition.
How does glaucoma cause optic nerve damage?
A clear fluid called the aqueous humor, which is produced in the front part of the eye, circulates in a space called the anterior chamber and it drains from an area where the cornea and iris meet called the angle (see figures 1 and 2). When the fluid drains too slowly through the trabecular meshwork of the angle or is blocked, it builds up in the eye causing elevated pressure. Most cases of optic nerve damage from glaucoma are due to elevated eye pressure but some cases can develop without increased eye pressure.
What are the factors that increase the risk of developing glaucoma?
The most common risk factors include age, elevated eye pressure, family history of glaucoma/anatomic predisposition, African or Hispanic heritage, vascular conditions such as diabetes and/or hypertension, nearsightedness, farsightedness, previous eye injuries and a cornea that is thinner than normal.
What are the different forms of glaucoma?
Primary open angle glaucoma is the most common form of glaucoma and is usually due to the drainage angle of the eye becoming less efficient.
Angle closure glaucoma occurs when the angle between the iris and the cornea is very narrow especially in farsighted and short eyes. This usually leads to complete blockage of the drainage angle leading to a rapid buildup of eye pressure causing an acute episode of blurred vision, severe eye pain with redness, headache, haloes around lights, nausea and vomiting. This is a medical emergency as the acute and severe rise in eye pressure can lead to blindness. If you are experiencing any of these symptoms, you need to call an ophthalmologist immediately as prompt treatment with eye medications followed by laser surgery can relieve the blockage, lower the eye pressure and protect vision.
How is glaucoma detected?
The only definitive way to detect glaucoma is through a comprehensive glaucoma evaluation, including central visual acuity testing, intraocular pressure measurement (tonometry), examination of the drainage angle (gonioscopy), examination of the optic nerve, side or peripheral vision testing (visual field perimetry), scanning of the optic nerve structure (optical coherence tomography) and measurement of the corneal thickness (pachymetry).
How is glaucoma treated?
Daily medication eyedrops which lower eye pressure are usually given. The goal of treatment is to lower the pressure to a normal level of 20 or below. In cases where eyedrops are not effective or causing side effects, laser treatment can be performed. In open angle glaucoma, multiple laser spots are applied to increase the fluid drainage through the trabecular meshwork. This procedure, called trabeculoplasty, can decrease eye pressure and dependence on eyedrops (see figure 3). In closed angle glaucoma, the laser makes a hole through the iris called iridotomy, thus relieving the fluid blockage in the drainage angle (see figure 4).
In cases where medication eyedrops or laser treatment is not effective, glaucoma surgery is performed to create a new filter or drainage channel for the fluid to leave the anterior chamber. This procedure is called trabeculectomy.
What are new options in glaucoma surgery?
Dr. Khouri went to the Agarwal Eye Hospital in India during the month of July 2014 and trained with well known ophthalmologist Dr. Soosan Jacob on a new glaucoma surgical technique which she developed in 2013 called stab incision glaucoma surgery (SIGS). SIGS is a simplified filtering procedure which does not require dissection of eye tissues as in trabeculectomy. Therefore, postoperative filter scarring and failure are reduced. Recovery is also quicker as this new procedure is less invasive. For more details, please refer to her video which won an award at the American Society of Cataract and Refractive Surgery in April 2014 at http://eyetubeod.com/series/daily-coverage-boston-april-2014/sigs-technique/