Glaucoma is a disease that damages the eye’s optic nerve. The optic nerve is connected to the retina — a layer of light-sensitive tissue lining the back of the eye — and is made up of many nerve fibers, like an electric cable is made up of many wires. It is the optic nerve that sends signals from your retina to your brain, where these signals are interpreted as the images you see. In the healthy eye, a clear fluid called aqueous (pronounced AY-kwee-us) humor circulates inside the front portion of your eye. To maintain a constant healthy eye pressure, your eye continually produces a small amount of aqueous humor while an equal amount of this fluid flows out of your eye. If you have glaucoma, the aqueous humor does not flow out of the eye properly. Fluid pressure in the eye builds up and, over time, causes damage to the optic nerve fibers. Glaucoma can cause blindness if it is left untreated. Only about half of the estimated three million Americans who have glaucoma are even aware that they have the condition. When glaucoma develops, usually you don’t have any early symptoms and the disease progresses slowly. In this way, glaucoma can steal your sight very gradually. Fortunately, early detection and treatment (with glaucoma eyedrops, glaucoma surgery or both) can help preserve your vision.
There are several types of glaucoma:
The most common form of glaucoma is called primary open-angle glaucoma. It occurs when the trabecular meshwork of the eye gradually becomes less efficient at draining fluid. As this happens, your eye pressure, called intraocular pressure (IOP), rises. Raised eye pressure leads to damage of the optic nerve. Damage to the optic nerve can occur at different eye pressures among different patients. Your ophthalmologist (Eye M.D.) establishes a target eye pressure for you that he or she predicts will protect your optic nerve from further damage. Different patients have different target pressures. Typically, open-angle glaucoma has no symptoms in its early stages and your vision remains normal. As the optic nerve becomes more damaged, blank spots begin to appear in your field of vision. You usually won’t notice these blank spots in your day-to-day activities until the optic nerve is significantly damaged and these spots become large. If all the optic nerve fibers die, blindness results. Half of patients with glaucoma do not have high eye pressure when first examined. Some such individuals will only occasionally have high eye pressures on repeat testing; thus, a single eye pressure test misses many with glaucoma. In addition to routine eye pressure testing, it is essential that the optic nerve be examined by an ophthalmologist for proper diagnosis.
A less common form of glaucoma is closed angle (or narrow-angle glaucoma or angle-closure glaucoma). Closed-angle glaucoma occurs when the drainage angle of the eye becomes blocked. Unlike open-angle glaucoma, eye pressure usually goes up very fast. The pressure rises because the iris — the colored part of the eye — partially or completely blocks off the drainage angle. People of Asian descent and those with hyperopia (farsightedness) tend to be more at risk for developing this form of glaucoma. If the drainage angle becomes completely blocked, eye pressure rises quickly resulting in a closed-angle glaucoma attack. Symptoms of an attack include severe eye or brow pain, redness of the eye, decreased or blurred vision, seeing colored rainbows or halos, headache, nausea, vomiting. A closed-angle glaucoma attack is a medical emergency and must be treated immediately. Unfortunately, people at risk for developing closed-angle glaucoma often have few or no symptoms before the attack. People at risk for closed-angle glaucoma should avoid over-the-counter decongestants and other medications where the packaging states not to use these products if you have glaucoma.
Your doctor measures your eye pressure using tonometry. (See photo above) Testing your eye pressure is an important part of a glaucoma evaluation. A high pressure reading is often the first sign that you have glaucoma. During this test, your eye is numbed with eyedrops. Your doctor uses an instrument called a tonometer to measure eye pressure. The instrument measures how your cornea resists pressure. Normal eye pressure generally ranges between 10 and 21 mm Hg. However, people with normal-tension glaucoma can have damage to their optic nerve and visual field loss even though their eye pressure remains consistently lower than 21 mm Hg.
Gonioscopy allows your ophthalmologist to get a clear look at the drainage angle to determine the type of glaucoma you may have. Your ophthalmologist is not able to see your eye’s drainage angle by looking at the front of your eye. However, by using a mirrored lens, he or she can examine the drainage angle to determine if you have open-angle glaucoma (where the drainage angle is not working efficiently enough), closed-angle glaucoma (where the drainage angle is at least partially blocked), or a dangerously narrow angle (where the iris is so close to the eye’s drain that the iris could block it).
Your ophthalmologist inspects your optic nerve for signs of damage using an ophthalmoscope, an instrument that magnifies the interior of the eye. Your pupils will be dilated (widened) with eyedrops to allow your doctor a better view of your optic nerve. A normal optic nerve is made up of more than one million tiny nerve fibers. As glaucoma damages the optic nerve, it causes the death of some of these nerve fibers. As a result, the appearance of the optic nerve changes. This is referred to as cupping. As the cupping increases, blank spots begin to develop in your field of vision.
The visual field test will check for blank spots in your vision. The results of the test show your ophthalmologist if and where blank spots appear in your field of vision — including spots you may not even notice. The test is performed using a bowl-shaped instrument called a perimeter. When taking the test, a patch is temporarily placed on one of your eyes so that only one eye is tested at a time. You will be seated and asked to look straight ahead at a target. The computer makes a noise and random points of light will flash around the bowl-shaped perimeter, and you will be asked to press a button whenever you see a light. Not every noise is followed by a flash of light. Visual field testing is usually performed every 6 to 12 months to monitor for change.
the clear window at the front of the eye (pachymetry) Because the thickness of the cornea can affect eye pressure readings, pachymetry is used to measure corneal thickness. A probe called a pachymeter is gently placed on the cornea to measure its thickness. The more recent way to measure in the OCT, which is more accurate, non-touch and more complete than the ultrasound pachymeters. So, at PVSC we prefer the OCT-Pachymetery.
Early structural progression of glaucoma may be better detected with pattern-based GCC parameters of the RTVue-OCT
Optical coherence tomography (OCT) has proven to be a useful tool in diagnosing and managing retinal and optic nerve disease. Recent technology has progressed to include examining the anterior segment. Anterior segment OCT (AS-OCT) generates in vivo, cross-sectional scans of the tissue to assist in analyzing the cornea, anterior chamber angle, iris and lens. Exceptional quality images, captured at a high speed rate, allow practitioners to embrace the new technology once reserved for the posterior segment.
The Diopsys® NOVA-VEP Vision Testing System is a part of the Diopsys® NOVA suite of tests which use a technology called Visual Evoked Potential (VEP) to objectively measure the functional responses of the entire visual pathway from the anterior segment of the eye to the visual cortex. Using VEP test results can help improve sensitivity and specificity in diagnosing visual pathway disorders when used in conjunction with other diagnostic tests. The Diopsys® NOVA-VEP system comes equipped with two protocols – the Diopsys® NOVA-LX and Diopsys® NOVA-TR.
Fundus automated perimetry is a technique that images the retina during visual field testing, enabling a correlation to be made between visual function and retinal structure.1 Advantages of Fundus Automated Perimetry over Standard Automated Perimetry include the possibility to measure sensitivity at specific retinal locations, higher accuracy thanks to retinal-tracking based compensation of eye movements and the simultaneous assessment of function (expressed by retinal sensitivity) and structure (images of the ONH, of the RNFL and of the retina). Fundus Automated Perimetry provides a simultaneous, quantitative assessment of fixation characteristics. Use of Fundus Automated Perimetry in the clinical management of glaucoma has been limited so far, as available systems were lacking compliance with the standards of automated perimetry. COMPASS overcomes such limitations and brings visual field analysis to the next level! In particular COMPASS, for the first time, extends field coverage to 30° + 30° and employs luminance parameters and a sensitivity scale as used in standard automated perimetry.
Glaucoma can be treated with eye drops, pills, laser surgery, traditional surgery or a combination of these methods. The goal of any treatment is to prevent loss of vision, as vision loss from glaucoma is irreversible. The good news is that glaucoma can be managed if detected early, and that with medical and/or surgical treatment, most people with glaucoma will not lose their sight. • SLT vs. medications. Surgeons say it’s been their experience, both in clinic and in reviewing published studies, that SLT is as good as medical therapy as a first-line treatment. A recent prospective, randomized study comparing SLT to drugs analyzed 127 eyes of 69 patients with open-angle glaucoma or ocular hypertension.3 The patients were randomized to 100 SLT applications encompassing 360 degrees of their trabecular meshwork, or medical therapy with a prostaglandin analog. Fifty-four patients reached the nine to 12 month follow-up point (29 SLT patients and 25 medical-therapy patients). Starting from similar baseline intraocular pressure levels, the mean IOP at the last follow-up was 18.2 mmHg (a 6.3-mmHg pressure reduction) in the SLT group and 17.7 mmHg (7-mmHg reduction) in the medical group. By the last follow-up, 11 percent of the SLT eyes required an additional SLT treatment and 27 percent of the medical group needed additional medication. The researchers say that even though the medical group needed more therapy to reach the target pressure, there was no statistically significant difference between the two groups. – See more at: http://www.reviewofophthalmology.com/content/i/1533/c/28664/#sthash.2NMNPA1t.dpuf
Eyedrops contain medicines that are used to treat many eye diseases and conditions. Some are helpful for relieving eye discomfort. Putting drops in your eye may seem difficult at first, but it becomes easier with practice. To learn how to insert eyedrops properly, follow these steps.
In some patients with glaucoma, surgery is recommended. Glaucoma surgery improves the flow of fluid out of the eye, resulting in lower eye pressure. A surgery called laser trabeculoplasty is often used to treat open-angle glaucoma. There are two types of trabeculoplasty surgery: argon laser trabeculoplasty (ALT) and selective laser trabeculoplasty (SLT). During ALT surgery, a laser makes tiny, evenly spaced burns in the trabecular meshwork. The laser does not create new drainage holes, but rather stimulates the drain to function more efficiently. With SLT, a low level energy laser targets specific cells in the mesh-like drainage channels using very short applications of light. The treatment has been shown to lower eye pressure at rates comparable to ALT. Even if laser trabeculoplasty is successful, most patients continue taking glaucoma medications after surgery. For many, this surgery is not a permanent solution. Nearly half who receive this surgery develop increased eye pressure again within five years. Many people who have had a successful laser trabeculoplasty have a repeat treatment. Laser trabeculoplasty can also be used as a first line of treatment for patients who are unwilling or unable to use glaucoma eyedrops.
When laser iridotomy is unable to stop an acute closed-angle glaucoma attack, or is not possible for other reasons, a peripheral iridectomy may be performed. Performed in an operating room, a small piece of the iris is removed, giving the aqueous fluid access to the drainage angle again. Because most cases of closed-angle glaucoma can be treated with glaucoma medications and laser iridotomy, peripheral iridectomy is rarely necessary.
The current approach in the management of patients with glaucoma begins with laser trabeculoplasty followed by medications, and then either a trabeculectomy or a glaucoma drainage device. Both are highly effective, yet invasive and complication-prone solutions. Traditional trabeculectomy and tube shunt procedures require substantial dissection of the ocular tissues, and have a relatively high complication rate (up to 50% at one year). Unfortunately, these procedures are not only invasive, but also have a high degree of variability that can lead to too little or too much intraocular pressure reduction (IOP). Despite these high complication rates and variability, these procedures are still the most common glaucoma surgeries performed globally due to the need for significant efficacy. Worldwide, doctors accept that the subconjunctival outflow pathway delivers the greatest IOP reduction because it has been proven in millions of cases during 50+ years of usage. AqueSys has developed a new technology that is designed to have similar efficacy as the invasive gold standard procedures yet through a standardized minimally invasive procedure that has the potential to significantly lower traditional complication rates.
Gonioscopy-assisted transluminal trabeculotomy (GATT) is a minimally invasive, ab interno approach to a circumferential 360Âº trabeculotomy. This surgical technique lowers IOP by cleaving the trabecular meshwork, thereby improving aqueous outflow through the normal conventional pathway. Although often regarded as a pediatric glaucoma surgical technique, circumferential trabeculotomy has been shown to be effective in adults as well. GATT builds upon the success of traditional trabeculotomy by eliminating conjunctival and scleral dissection with an excellent safety profile.
In trabeculectomy, a small flap is made in the sclera (the outer white coating of your eye). A filtration bleb, or reservoir, is created under the conjunctiva — the thin, filmy membrane that covers the white part of your eye. Once created, the bleb looks like a bump or blister on the white part of the eye above the iris, but the upper eyelid usually covers it. The aqueous humor can now drain through the flap made in the sclera and collect in the bleb, where the fluid will be absorbed into blood vessels around the eye. Eye pressure is effectively controlled in three out of four people who have trabeculectomy. Although regular follow-up visits with your doctor are still necessary, many patients no longer need to use eyedrops. If the new drainage channel closes or too much fluid begins to drain from the eye, additional surgery may be needed.
If trabeculectomy cannot be performed, aqueous shunt surgery is usually successful in lowering eye pressure. An aqueous shunt is a small plastic tube or valve connected on one end to a reservoir (a roundish or oval plate). The shunt is an artificial drainage device and is implanted in the eye through a tiny incision. The shunt redirects aqueous humor to an area beneath the conjunctiva (the thin membrane that covers the inside of your eyelids and the white part of your eye). The fluid is then absorbed into the blood vessels. When healed, the reservoir is not easily seen unless you look downward and lift your eyelid. Important things to remember about glaucoma: There are a number of ways to treat glaucoma. While some people may experience side effects from glaucoma medications or glaucoma surgery, the risks of side effects should always be balanced with the greater risk of leaving glaucoma untreated and losing vision. If you have glaucoma, preserving your vision requires strong teamwork between you and your doctor. Your doctor can prescribe treatment, but it’s important to do your part by following your treatment plan closely. Be sure to take your medications as prescribed and see your ophthalmologist regularly.