Glaucoma

 What is Glaucoma?

Glaucoma refers to a group of eye conditions in which increased fluid pressure inside the eye causes irreversible damage to the optic nerve. The optic nerve is responsible for carrying visual information from the eye to the brain. If left untreated, glaucoma will eventually lead to blindness. Glaucoma is the second most common cause of blindness in the United States, and first worldwide. Glaucoma can affect anyone at any age.

About the Disease

• • A major risk factor for glaucoma is increased eye pressure that occurs when fluid in the eye that is used to transport nutrients to the lens and cornea – accumulates and cannot drain naturally.
  • Over time the trapped fluid builds up, causing increased pressure in the eye, which can damage the optic nerve and destroy vision.
  • The first sign of glaucoma is often a loss of peripheral or side vision. Untreated glaucoma can lead to tunnel vision and eventually can cause total blindness.

View Video

Glaucoma can be grouped into two categories:

• • • • • Open-angle glaucoma – Represents the majority of all glaucoma cases. Open-angle glaucoma is asymptomatic – meaning it occurs without noticeable symptoms appearing – and can often go undiagnosed without proper checkups, and worsen over time.
        • Angle-closure glaucoma – Less common but more severe, and is marked with a rapid rise in eye pressure and severe vision loss.

       

  View Video

 

 

Glaucoma Treatments

While there is still no actual cure for glaucoma, Rapid City’s Black Hills Regional Eye Institute does offer treatment options to slow, stop, and in some cases reverse the effects of the disease.

The goal of any procedures/glaucoma treatment is to reduce eye pressure, as this is the inevitable cause of vision impairment. Depending on the type of procedures/glaucoma, medication and surgery are currently the only viable options. The most common treatment method prescribed is medicated eye drops, which reduce pressure and in some cases protect the optic nerve from further damage. Eye drops are usually prescribed to patients with open-angle and secondary procedures/glaucoma and in some cases angle-closure. For those suffering from angle-closure procedures/glaucoma, the pain caused by an attack will dictate emergency medical attention. If left untreated, angle-closure procedures/glaucoma can result in blindness in a matter of days. Medicated eye drops or pills may be prescribed, but in all likelihood, laser surgery will be necessary. Laser surgery for both angle-closure and congenital procedures/glaucoma reopens or creates new channels for fluid in the eye in order to reduce swelling.

Glaucoma and Marijuana

One of the commonly discussed alternatives for the treatment of glaucoma by lowering IOP is the smoking of marijuana.  It has been definitively demonstrated, and widely appreciated, that smoking marijuana lowers IOP in both normal individuals and in those with glaucoma, and therefore might be a treatment for glaucoma.  Less often appreciated is marijuana’s short duration of action (only 3-4 hours), meaning that to lower the IOP around the clock it would have to be smoked every three hours.  Furthermore, marijuana’s mood-altering effects would prevent the patient who is using it from driving, operating heavy machinery, and functioning at maximum mental capacity.  Marijuana cigarettes also contain hundreds of compounds that damage the lungs, and the deleterious effect of chronic, frequent use of marijuana upon the brain is also well established.

Other means of administering the active ingredient of marijuana, tetrahydrocannabinol (THC), include oral, sublingual, and eye drop instillation.  The first two avoid the deleterious effect of marijuana smoke on the lungs, but are limited by the other systemic side effects.  In one study in which doctors offered some of their patients with worsening glaucoma the option of pills containing tetrahydrocannabinol and/or smoking marijuana, 9 of 9 patients had discontinued use by either or both methods within 9 months due to side effects.  Given that glaucoma is a lifelong disease, commonly requiring treatment for decades, these results strongly suggest that systemic use of THC is not a reasonable treatment option for such patients.  The use of eye drops containing THC, or related compounds, has been investigated, but it has not yet been possible to formulate an eye drop that is able to introduce the drug into the eye in sufficient concentrations due to the low water solubility of the active ingredients.

Although marijuana does lower the IOP temporarily, IOP lowering is only one consideration in slowing the optic nerve damage of glaucoma.  For instance, there is a growing body of evidence that inadequate blood supply to the optic nerve may contribute to glaucoma damage.  Since marijuana given systemically is known to lower blood pressure, it is possible that such an effect could be deleterious to the optic nerve in glaucoma, possibly reducing or eliminating whatever beneficial effect that conferred by lowering IOP.   For this reason, marijuana, or its components administered systemically, cannot be recommended without a long-term trial which evaluates the health of the optic nerve.

An exciting finding in the past decade is the discovery of receptors for the active components of marijuana in the tissues of the eye itself, suggesting that local administration has the possibility of being effective.  Furthermore, there is evidence from research in the brain that there may be properties of the cannabinoid components of marijuana that protect nerve cells like those in the optic nerve.  This raises the hope that marijuana or related compounds could protect the optic nerve not only through IOP lowering but also through a neuroprotective mechanism.  However, unless a well-tolerated formulation of a marijuana-related compound with a much longer duration of action is shown in rigorous clinical testing to reduce damage to the optic nerve and preserve vision, there is no scientific basis for use of these agents in the treatment of glaucoma.

Summary: Although marijuana can lower the intraocular pressure (IOP), its side effects and short duration of action, coupled with a lack of evidence that its use alters the course of glaucoma, preclude recommending this drug in any form for the treatment of glaucoma at the present time.

The Black Hills Regional Eye Institute will not be prescribing marijuana for our patients at this time.