|
Page: Treatment
Main article
| Home > Elderly Health > Treatment |
Although intraocular pressure is only one of the risk factors (albeit a major one) of glaucoma, lowering it via pharmaceuticals or surgery is currently the mainstay of glaucoma treatment. In Europe, Japan, and Canada laser treatment is often the first line of therapy. In the U.S., adoption of early laser has lagged, even though prospective, multi-centered, peer-reviewed studies, since the early '90s, have shown laser to be at least as effective as topical medications in controlling intraocular pressure and preserving visual field.
Drugs
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. Prostaglandin analogs like latanoprost (Xalatan), bimatoprost (Lumigan) and travoprost (Travatan) increase uveoscleral outflow of aqueous. Topical beta-adrenergic receptor antagonists such as timolol, levobunolol (Betagan) , and betaxolol decrease aqueous humor production by the ciliary body. Alpha2-adrenergic agonists such as brimonidine (Alphagan) work by a dual mechanism, decreasing aqueous production and increasing uveo-scleral outflow. Less-selective sympathomimetics like epinephrine and dipivefrin (Propine) increase outflow of aqueous humor through trabecular meshwork and possibly through uveoscleral outflow pathway, probably by a beta2-agonist action. Miotic agents (parasympathomimetics) like pilocarpine work by contraction of the ciliary muscle, tightening the trabecular meshwork and allowing increased outflow of the aqueous humour. Carbonic anhydrase inhibitors like dorzolamide (Trusopt), brinzolamide (Azopt), acetazolamide (Diamox) lower secretion of aqueous humor by inhibiting carbonic anhydrase in the ciliary body. Each of these medicines may have local and systemic side effects. Adherence to medication protocol can be confusing and expensive; if side effects occur, the patient must be willing either to tolerate these, or to communicate with the treating physician to improve the drug regimen.
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.
Marijuana has been shown to lower the intraocular pressure in a few studies but this is generally not used clinically. Studies in the 1970s showed that marijuana, when smoked, lowers intraocular pressure. In an effort to determine whether marijuana, or drugs derived from marijuana, might be effective as a glaucoma treatment, the US National Eye Institute supported research studies from 1978 to 1984. These studies demonstrated that some derivatives of marijuana lowered intraocular pressure when administered orally, intravenously, or by smoking, but not when topically applied to the eye. However, none of these studies demonstrated that marijuana -- or any of its components -- could safely and effectively lower intraocular pressure any more than a variety of drugs then on the market. In 2003, the American Academy of Ophthalmology released a position statement asserting that "no scientific evidence has been found that demonstrates increased benefits and/or diminished risks of marijuana use to treat glaucoma compared with the wide variety of pharmaceutical agents now available."
The first patient in the United States federal government's Compassionate Investigational New Drug program, Robert Randall, was afflicted with glaucoma and had successfully fought charges of marijuana cultivation because it was deemed a medical necessity (U.S. v. Randall) in 1976.
The possible neuroprotective effects of various topical and systemic medications are also being investigated.
Surgery
Main article: Glaucoma surgery
Both laser and conventional surgeries are performed to treat glaucoma. Laser trabeculoplasty may be used to treat open angle glaucoma. It is a temporary solution, not a cure. A 50 um argon laser spot is aimed at the trabecular meshwork to stimulate opening of the mesh to allow more outflow of aqueous fluid. Usually, half of the angle is treated at a time. Laser peripheral iridectomy may be used in patients susceptible to angle closure glaucoma. In it, the laser is aimed at the iris to make an opening in it. This allows a new channel for fluid to flow when the usual channel through the dilated pupil is blocked.
The most common conventional surgery performed for glaucoma is the trabeculectomy. Here, a partial thickness flap is made in the scleral wall of the eye, and a window opening made under the flap to remove a portion of the trabecular meshwork. The scleral 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. 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 type.
There are also several different glaucoma drainage implants. These include the older non-valved tubes, such as the Molteno implant or the Baerveldt tube shunt, or the newer valved implants, such as the Ahmed glaucoma valve implant or the ExPress Mini Shunt. These are indicated for glaucoma patients not responding to maximal medical therapy, with previous failed guarded filtering surgery (trabeculectomy). The flow tube is inserted into the anterior chamber of the eye and the plate is implanted underneath the conjunctiva to allow flow of aqueous fluid out of the eye. Molteno and other non-valved implants require the ligation of the tube until the surgical wound is mildly fibrosed and water-tight. This may induce potentially dangerous spikes in the intraocular pressure (IOP). The Ahmed glaucoma valve on the other hand does not have such a limitation and avoids spikes in IOP. The ongoing scarring over the conjunctival dissipation segment of the shunt may become too thick for the aqueous humor to filter through. This may require preventive measures using anti-fibrotic medication like 5-fluorouracil (5-FU) or mitomycin-C (during the procedure), or additional surgery.
Surgery is the primary therapy for those with congenital glaucoma.
Generally, these operations are a temporary solution, as there is not yet a cure for glaucoma.
|
Important notice:
The content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other
qualified health provider with any questions you may have regarding a medical condition.
|