Angle-closure glaucoma: Description, Causes and Risk Factors:Abbreviation: ACG.Angle-closure glaucoma affects nearly half a million people in the US. There is a tendency for this disease to be inherited, and often several members of a family will be afflicted. It is most common in people of Asian descent and people who are farsighted.In people with a tendency to angle-closure glaucoma, the anterior chamber is smaller than average. As mentioned earlier, the trabecular meshwork is situated in the angle formed where the cornea and the iris meet. In most people, this angle is about 45 . The narrower the angle, the closer the iris is to the trabecular meshwork. As we age, the lens routinely grows larger. The ability of aqueous humor to pass between the iris and lens on its way to the anterior chamber becomes decreased, causing fluid pressure to build up behind the iris, further narrowing the angle. If the pressure becomes sufficiently high, the iris is forced against the trabecular meshwork, blocking drainage, similar to putting a stopper over the drain of a sink. When this space becomes completely blocked, an angle-closure glaucoma attack results.Angle closure may occur 2 ways:The iris may be pushed forward up against the trabecular meshwork.
The iris may be pulled up against the trabecular meshwork.
In either case, the position of the iris causes the normally open anterior chamber angle to close. Aqueous humor that should normally drain out of the anterior chamber is trapped inside the eye, thereby increasing the intraocular pressuer (IOP).If the ensuing rise in pressure is sudden, pain, blurred vision, and nausea may occur. Optic nerve damage may also occur due to the increased IOP, either in a sudden attack or in intermittent episodes over a long period of time.Sometimes, the attack may be caused by dilation of the pupils, possibly during an eye examination.Symptoms:Symptoms of angle-closure glaucoma may include:Hazy or blurred vision.
The appearance of rainbow-colored circles around bright lights.
Severe eye and head pain.
Nausea or vomiting (accompanying severe eye pain).
Sudden sight loss.
Some people may experience intermittent episodes of angle-closure and elevated IOP without ever having a full-blown attack of angle-closure glaucoma. This is called subacute angle-closure glaucoma.People with subacute angle-closure glaucoma may have no symptoms, or they may experience mild pain, have slightly blurred vision, or see haloes around lights. These symptoms resolve spontaneously as the angle reopens.Diagnosis:Diagnosis is made on history and examination. Diagnosis of ACG is based on the finding of 2 symptoms of ocular pain, nausea/vomiting, and a history of intermittent blurring of vision with halos and at least 3 signs of: IOP > 21 mmHg, conjunctival injection, corneal epithelial edema, mid-dilated non-reactive pupil and shallower chamber in the presence of occlusion.During an examination for angle-closure glaucoma, your ophthalmologist performs the following tests: gonioscopy, tonometry, biomicroscopy, and ophthalmoscopy.Treatment:Treatment in this condition needs to be rapid. It takes the form of drops, medicines given intravenously and orally, laser surgery and sometimes surgical treatment. Systemic medicines (carbonic anhydrase inhibitors) as the pressure is very high inside the eye, this needs to be dropped rapidly and therefore medicines, such as acetazolamide are given rapidly into the circulation through a vein. This should reduce the pressure quite quickly.Surgical Options:Peripheral iridotomy (PI) - this refers to (usually 2) holes made in each iris with a laser, usually at around the 11 and 2 o'clock positions (they can be seen when assessing the red reflex when they are patent). The idea is to provide a free-flow transit passage for the aqueous to prevent further pupil block. Both eyes are treated, as the fellow eye will be predisposed to an AAC (acute angle-closure) attack too. This procedure can usually be carried out within the week following the acute attack, once corneal edema has cleared enough to provide a good view of the iris.
Surgical iridectomy - this is carried out where PIs are not possible. It is a less favored option, as it is more invasive and therefore more prone to complications.
Lensectomy - one of the few situations where cataract surgery is performed on an urgent basis is when the cataractous lens has swollen to precipitate an attack of AAC. The lens is extracted at the earliest opportunity. Beyond this particular cause of AAC, there is some debate as to whether a lensectomy should be routinely performed.
NOTE: The above information is for processing purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
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