Glaucoma is a group of neuropathies affecting the optic nerve, usually in the context of high eye pressure but not always.
There are many glaucoma subtypes, we will cover the main ones. Physiopathology of glaucoma is not well understood.
Open angle glaucoma or chronic glaucoma is a very insidious disease. The eye pressure is usually higher than it should be for a particular eye. This results in damage to the optic nerve.
At first a patient is fully unaware because the disease is painless, the eye is white and quiet ; early damage to the peripheral visual field cannot be noted by the patient. Only a routine eye exam with your eye doctor can raise the alarm for glaucoma.
Your optometrist will look at the eye pressures, the optic nerves. Your eye doctor will also look at known risk factors such as ethnicity, family history. With all that, if the suspicion is strong for glaucoma, your optometrist will order additional testing that usually includes pachymetry (thickness of the cornea is a risk factor itself), automated visual fields to assess the peripheral vision and an optic nerve OCT which will look at how healthy the nerve fiber layer that surround the optic nerve is. From those studies, your eye doctor may determine you don't have glaucoma. He may follow up closely with you if you are borderline or he may start a treatment. At first, treatment consists of eye drops aimed at lowering the eye pressure.
There are many classes of drugs available to treat glaucoma. They include beta-blockers, prostaglandins analogs, carbonate anhydrase inhibitors or alpha agonists. Sometimes one drop is not enough and your optometrist will decide you need to use more than one eye drop. If that is not sufficient to control the progression of glaucoma, referral to a glaucoma specialist is made. The specialist will advise the patient on surgical techniques geared toward lowering the eye pressure.
Normal Tension Glaucoma or Low Tension Glaucoma shares a lot of similarities with open angle glaucoma, except at first the eye pressure is within normal limits, which means commonly accepted as normal (10-21 mmHg). We now know that low tension glaucoma has a vascular factor in the mechanism of the disease. It affects people with low blood pressure, sleep apnea, migraines or Raynaud disease. The theory is that a drop of blood pressure at night triggers a lack of oxygenation to the optic nerve. Treatment modalities are similar to Open Angle Glaucoma but the eye pressure is lowered for different reasons
Acute Angle Closure Glaucoma. Unlike the two previous types of glaucoma that can take years to develop and create damage, acute angle closure glaucoma is a sudden, extreme rise in intra-ocular pressure than can results in fast vision loss if not treated.
Patients with acute angle closure glaucoma are usually very symptomatic : pain is unbearable , they have nausea and very cloudy vision from one eye. The eye is red and painful ; it is a medical emergency that needs to be addressed immediately .
Our optometry office in North Miami FL offers emergency services and after hours we work with a group of ophthalmologists. Immediate lowering of the eye pressure is necessary. This is done with eye drops and oral medications.
Once the eye pressure is lowered and cornea regains its transparency a hole is made in the iris to prevent the crisis from happening again. This is called a Laser Peripheral Iridectomy, or LPI.
In patients with anatomical risks of angle closure glaucoma, a prophylaxis LPI is indicated. During your routine eye exam at our office in North Miami we always look at the iridocorneal angle to make sure it is not occludable, meaning you are not at risk for an acute glaucoma crisis. If you are at risk, we will recommend an appointment with our glaucoma specialist who will perform a prophylactic LPI so you never have acute angle closure glaucoma event.
Typically patients who are anatomically are risk are hyperopes or people with hypermetropia because the eye is a bit small . The angle closure can happen when the pupil dilates. Pupil dilates naturally at night in a dark environment or in the eye doctor office when we use drops to perform the dilated fundus exam. Don't worry, at our optometry office in Miami, when you come in for an eye exam, we always make sure the "angle" is opened before putting drops to dilate your pupils.