Faq Glaucoma

What is Glaucoma?

The optic nerve is made up of many nerve fibers that carry images to the brain. It’s like an electric cable containing numerous wires. When glaucoma damages the optic nerve fibers, blind spots develop. If the entire nerve is destroyed, blindness results.

Primary open-angle glaucoma is the most common form of glaucoma. Typically, open-angle glaucoma has no symptoms in its early stages, and vision remains normal.

As the optic nerve becomes more damaged, blank spots begin to appear in your field of vision. You typically 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.

The other common type of glaucoma (angle closure glaucoma) can have sudden increase in eye pressure leading to symptoms like headaches, eye aches, episodes of blurring of vision and coloured haloes around lights. In cases where the pressure increases to a very high level severe headaches associated with nausea and vomiting may occur.

What are the Signs and Symptoms of Glaucoma?

Glaucoma is a group of eye diseases that gradually steal sight without warning. In the early stages of the disease, there may be no symptoms. Experts estimate that half of the people affected by glaucoma may not know they have it.

Vision loss is caused by damage to the optic nerve. This nerve acts like an electric cable with over a million wires. It is responsible for carrying images from the eye to the brain.

There is no cure for glaucoma—yet. However, medication or surgery can slow or prevent further vision loss. The appropriate treatment depends upon the type of glaucoma among other factors. Early detection is vital to stopping the progress of the disease.

It was once thought that high pressure within the eye, also known as intraocular pressure or IOP, is the main cause of this optic nerve damage. Although IOP is clearly a risk factor, we now know that other factors must also be involved because even people with “normal” levels of pressure can experience vision loss from glaucoma.

What Causes Glaucoma?

Our eyes constantly produce a clear fluid called aqueous humor, which bathes and nourishes different regions of the eye (this is different from tears). Normally the fluid drains out of the eye through a ‘drainage canal’ located in the ‘angle’ of the eye, the junction between the cornea and the iris. In persons with glaucoma, the fluid does not drain out as freely as it should, thus increasing the pressure inside the eye, known as intraocular pressure (IOP).

The optic nerve carries all sensations from the retina to the brain. Raised IOP damages the optic nerve.

Glaucoma can sometimes occur with a statistically “normal” IOP. Hence the vulnerability of the optic disc is another factor that needs to be considered. Accordingly, the diagnosis of glaucoma requires more than just the mere measurement of intraocular pressure.

Types of Glaucoma?

There are several types of glaucoma all of which can increase IOP and damage the optic nerve.

In open angle glaucoma, an increase in resistance to the outflow in the canal causes a rise in the IOP. This type develops gradually and the symptoms may not be obvious till the damage has occurred. The patient may lose peripheral vision, leaving only central or ‘tunnel’ vision. This occurs more among people above 45 years of age.

In angle closure glaucoma there is a relative block to the flow of fluid, which causes raised pressure. This occurs more among long-sighted people. In the rarer acute cases, the symptoms are dramatic and may include severe pain in the eye, headache, nausea, reduced vision, and seeing rainbow coloured rings around lights. Stress, anxiety, and reading may also precipitate an attack, which may resolve on its own, but recur after some time.

The more common variety of angle closure glaucoma is chronic angle closure. This behaves similar to open angle glaucoma but here, the ‘drainage’ canal is closed by the iris.

The third type is developmental glaucoma, which may be further divided into congenital glaucoma (occurs in infants from the time of birth) and juvenile glaucoma (occurs in children and young adults).

Glaucoma or high IOP may also be secondary and occur due to other causes such as the use of steroid drops without prescription. Such drops should never be used without monitoring the intraocular pressure.

Who is at Risk?

The risk factors for glaucoma are:

  • Age (65 years and older)
  • Elevated eye pressure
  • Family history of glaucoma
  • Farsightedness or nearsightedness
  • Past eye injuries
  • Thinner central corneal thickness
  • Pre-existing thinning of the optic nerve
  • Not having eye examinations at the recommended intervals
  • Steroid use
  • Other health problems like diabetes, low blood pressure or migraine headaches

Your ophthalmolgist, will weigh all of these factors before deciding whether you need treatment. You may simply need to be monitored closely if your risk of developing glaucoma is higher than normal. Make sure to have regular examinations to detect the early signs of damage to the optic nerve. Comprehensive eye check at 40 years

Individuals with risk factors for glaucoma (e.g. family history of glaucoma or nearsightedness) should have an eye examination every two to four years under 40 years of age, every one to two years between 40 and 54 years, every one year between age 55 and 64 years, and every six to 12 months for age 65 or older.

A complete eye examination – not only the usual reading of the chart – is mandatory, especially after the age of 40. Actually, everyone should have a comprehensive eye examination periodically as it can help detect other preventable, controllable, or treatable diseases such as retinal detachment, diabetic eye disease, and cataract.

How is Glaucoma Diagnosed?

Regular eye examinations by your Eye doctor are the best way to detect glaucoma.

Since the treatment methods for open angle and angle closure glaucoma are different, it is important to identify the mechanism involved. The diagnosis (or

exclusion) of glaucoma requires a detailed and comprehensive eye examination. Your doctor will do the following examinations:

  • A routine vision test that requires reading letters from a chart,
  • Slit lamp (microscope) examination.
  • The pressure inside the eye is measured with an ‘applanation tonometer’ attached to the slit lamp. A hand held version of the instrument is also effective. It may be necessary to obtain multiple readings of the pressure during the course of the day and at night. The older method of resting an instrument on the cornea while the patient lies down is not accurate.
  • An examination of the angle of the eye is done with the help of a gonioscope. This is a contact lens placed on the eye to examine the angle of the eye. Its use is mandatory in determining the type of glaucoma – open angle or angle closure.
  • An optic disc examination on a dilated eye is also required. For obtaining a stereoscopic view on the microscope, a hand-held lens or a contact lens is the best method. A computerized scan of the optic disc may also be done.

Special Tests for Glaucoma

Field Charting (Automated Perimetry):

To confirm the diagnosis, the doctor will conduct an automated field or perimetry test. Damage to the optic nerve limits the field of vision, but regular vision, i.e. the ability to read an ophthalmologist’s eye chart, is affected at a much later stage. In its early stages glaucoma can only be detected or monitored by using an automated perimetry test. A normal patient will have a ‘full field vision’, while a person with glaucoma has black, non-seeing areas in the field of vision.

Many people have difficulty doing the perimetry test at first, and may be better at it the second or the third time. Baseline tests are necessary for future comparison and periodic examinations are essential to check the progression of the disease.

Considering the importance of the test, ANY automated perimeter is NOT acceptable. The field test is a subjective test and it is important to have a calibrated machine with an appropriate normal database against which to compare your results.

Sometimes a diagnosis may not be possible on one visit. In very early cases it may be necessary to repeat the entire examination after a period of observation.

Optic Disc Photography:

Optic disc is the only part of the optic nerve visible to the eye doctor in the back of the eye. The appearance of the disc gives valuable information to diagnose and treat conditions such as glaucoma. It is important to be able to compare the appearance of the disc over a period time in cases of chronic glaucoma. This is made possible by several techniques- one of which is the photography of the disc using the fundus camera.
Optic Nerve Computer Imaging:

In recent years three new techniques of optic nerve imaging have become widely available. These are scanning laser polarimetry (GDx), confocal laser ophthalmoscopy (Heidelberg Retinal Tomography or HRT), and optical coherence tomography (OCT).

The GDx machine does not actually image the optic nerve but rather it measures the thickness of the nerve fiber layer on the retinal surface
just before the fibers pass over the optic nerve margin to form the optic nerve. The HRT scans the retinal surface and optic nerve with a laser. It then constructs a topographic (3-D) image of the optic nerve including a contour outline of the optic cup. The nerve fiber layer thickness is also measured. The OCT instrument utilizes a technique called optical coherence tomography which creates images by use of special beams of light. The OCT machine can create a contour map of the optic nerve, optic cup and measure the retinal nerve fiber thickness. Over time all three of these machines can detect loss of optic nerve fibers.

Pachymetry (Central Corneal Thickness):

Corneal thickness is important because it can mask an accurate reading of eye pressure, causing doctors to treat you for a condition that may not really exist or to treat you unnecessarily when are normal. Actual IOP may be underestimated in patients with thinner CCT, and overestimated in patients with thicker CCT. This may be important to your diagnosis.It is important to make sure your doctor takes your CCT into account for diagnosis.

Ultrasound Biomicroscopy (UBM):

This is an advanced technology in ultrasonography, which permits high-resolution pictures of the front of the eye. The technology enables the measurement of the angle of the eye, which is otherwise not accessible for measurement. The angle of the eye is the path through which the fluid in the eye finds access outside. The angle can become closed in certain individuals. This propensity to closure of the angle can be more adequately predicted using this advanced testing. Following injury to the eye, sometimes abnormal communications develop leading to excess drainage of fluid and resulting soft eyes. These abnormal sites can be best identified by UBM. Some of these tests may not be necessary for everyone. These tests may need to be repeated on a regular basis to keep track of any changes in your condition.

Treatment

It is important to realize that there is no cure for glaucoma. Once nerve fibers die and visual function is lost, it cannot be recovered. Treatment can only help preserve remaining vision; hence it is imperative to detect the disease in its earliest stage.

The management of glaucoma must be an individualized effort. Simplistically speaking, in angle closure glaucoma doctors use a laser to create an alternative

 

path for the fluid to drain out. However, this approach works for early cases; advanced cases require medication and surgery as for open angle glaucoma. An

 

attack of closed angle glaucoma is an emergency and the IOP must be lowered as soon as possible to prevent damage to the optic nerve.

For open angle glaucoma, initially eye drops are used to lower IOP; your doctor will select the one most suited for your condition. If the disease is advanced, and/or medical treatment fails, surgery may be necessary.

Medical therapy is expensive, and likely to be life-long. As with any treatment, there is a risk of side effects. Sometimes the side effects may be more uncomfortable for the patient, and less acceptable, than living with the disease. Therefore doctors consider the risk-benefit ratio of the treatment options for glaucoma. The main criterion is how much functional capacity is affected rather than the actual degree of vision loss. Your doctor will select the treatment most suited for your condition, please follow the advice meticulously.

In some patients glaucoma may be controlled by medicine alone, while others may need laser treatment or surgery. Surgery usually involves cutting a piece of tissue from the angle of the eye and allowing the fluid to accumulate under the transparent skin that surrounds the eyeball. However, glaucoma surgery is not as predictable as cataract surgery and carries more risks, including loss of the eye from devastating bleeding or infection. It is usually used if drugs fail to control eye pressure, or for socioeconomic considerations.

Non-penetrating surgery can also help decrease eye pressure and has fewer complications than the standard approach. But its results are not as good. Hence it is not a first line of treatment for glaucoma.

In cases with poor potential for visual recovery or function, a different kind of laser may be used to reduce eye pressure. This is usually reserved for advanced cases.

Need for Constant Care

Life long monitoring is essential, the frequency of follow up visits depends on the individual case. At each visit most of the tests may be repeated to determine the progression of the disease and to decide whether change in treatment is needed.

Glaucoma damages the optic nerve. The optic nerve is the part of the eye that carries the images we see to the brain. If your vision seems blurry, contains blank spots, or if you have eye pain or see rainbow-colored halos around lights, call your Eye M.D. right away.

The optic nerve is made up of many nerve fibers that carry images to the brain. It’s like an electric cable containing numerous wires. When glaucoma damages the optic nerve fibers, blind spots develop. If the entire nerve is destroyed, blindness results.

As the optic nerve becomes more damaged, blank spots begin to appear in your field of vision. You typically won’t notice these blank spots in your day-to-day activities until the optic nerve is significantly damaged and these spots become large.

Glaucoma Filtration Surgery

Also known as: Trabeculectomy
What it is:
Glaucoma Filtration Surgery is the most common surgery for open-angle glaucoma. It helps the eye drain liquid more effectively.
What You Can Expect:
This is an outpatient surgery usually performed in less than an hour. You will be able to go home the same day.
Who Is a Good Candidate:
If your glaucoma medications cannot lower eye pressure enough, your ophthalmologist (Eye M.D.) will probably recommend surgery.