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About Glaucoma

Glaucoma

1. What is Glaucoma?
Glaucoma is a progressive optic neuropathy. It is the damage caused to the optic nerve due to increase in intra ocular pressure or deficient blood supply. The chronic variety of this disease is like a slow poison. People seldom notice the symptoms until considerable nerve damage has occurred. Once the damage has occurred, it cannot be reversed. Optic nerve damage causes loss of visual acuity as also field of vision. Hence the important aspect is the early diagnosis and prevention of progression of the disease.
2. What causes Glaucoma & how does it affect the eyes?
In a normal eye there is a continuous circulation of fluid called aqueous humor, which is secreted by a structure called ciliary body positioned behind the coloured portion of eye known as iris. This fluid passes through the central opening, pupil & into the space called the anterior chamber. This fluid then drains into a structure called the trabecular meshwork & into the veins. Aqueous humor is responsible for the nourishment of vital structures as also its pressure helps in maintaining the shape of the eye. This pressure is called the intra ocular pressure (IOP). This pressure can rise either when the secretion of aqueous increases as in inflammation or when the drainage gets blocked. Increased IOP puts pressure on the optic nerve & creates a cup on its surface. This can also block the small vessels in the nerve leading to ischaemia & resultant nerve damage. Alternately if the blood supply to the optic nerve is compromised, there can be optic nerve damage even if the IOP is normal.
3. What are the types of Glaucoma?
Glaucoma generally is of four varieties.

  • Congenital Glaucoma: This condition called Buphthalmos occurs in newborn children, is characterized by abnormally large and cloudy eyes. It has to be treated surgically.
  • Chronic Glaucoma: This is the most common variety. Optic damage can occur, if the IOP is higher than what the eye can tolerate. The normal range is about 14-20 mm Hg. However this is relative and varies individually.
  • Acute Glaucoma: This constitutes a medical emergency. The patient develops a sudden blurring of vision with severe pain around the eye & may also be associated with vomiting. Permanent damage can occur in a matter of few days.
  • Secondary Glaucoma: This occurs as a side effect of some other disease process like, bleeding, inflammation, tumor, hyper mature cataract etc. Anatomically there are two forms of Glaucoma.
    • Open angle Glaucoma: When there is no obstruction to the fluid flow, but the drainage pores are blocked.
    • Closed angle Glaucoma: When the fluid flow is obstructed from reaching the drainage area by the iris bulging forward.
4) What are its Symptoms?

Generally the symptoms are noticed in condition of acute angle closure glaucoma. The patient gets severe pain around the eye associated with headache, vomiting and occasional dehydration. There is blurring of vision. The eyes become congested & the patient complains of seeing coloured haloes around the light. In the chronic type, symptoms like tense feeling and recurrent pain around the eyes, frequent changes in refraction (change of glass prescription especially for near vision) & rainbow coloured haloes around light if seen should alert you to seek a medical opinion. Subsequently, the patient notices constriction of visual fields when considerable damage has occurred.

5) Who are at risk?

Who should undergo screening test? Glaucoma can be present at birth or may develop later as juvenile or developmental glaucoma. However all adults over the age of 35 yrs., with the presence of any of the following risk factors should get a screening test done for glaucoma.

    Risk Factors:
  • Family History
  • Elevated IOP
  • Diabetes / Hypertension
  • Myopia
  • Long-term corticosteroids use.
  • Thyroid disorders.
  • Injury to the eye.

If you are over 35 & say  yes to any of the above, you have to get a screening test for glaucoma.

6. Diagnosis  of Glaucoma

Many a times, glaucoma is detected during routine  eye examinations. When you go for an eye check, it is important for the doctor  to know about your daily medications, family history of glaucoma & general  ailments like diabetes, hypertension, thyroid disorders etc.

 There are some important  diagnostic tests that are essential for the diagnosis of glaucoma.

a) Examination of optic  nerve (OD): During the course of routine eye check, the examination of OD gives  an initial clue about the disease. However this has to be confirmed by stereo  examination of the OD.

 

b) Documentation  of Optic Nerve (OD): The status of the optic nerve at the stage of diagnosis  should then be documented with Fundus photograph which is vital for follow up  of the disease.

c) Visual  Fields: The structural OD defect is then correlated with the functional changes  recorded by doing visual field examination. A positive correlation only can  establish the diagnosis.

 d) IOP:  The intra ocular pressure helps in establishing the intensity of the disease  & acts as a marker for its control. IOP is regarded as a single modifiable  risk factor in controlling glaucoma. After a detailed workup, your doctor  decides an ideal target IOP customized for you to maintain. Generally it is in  range of 12 to 20 mm Hg.

e) Gonioscopy:  This is a very important investigation that helps to know about the type of  glaucoma. The management varies for angle closure & open angle glaucoma  & gonioscopy helps in establishing this fact.

   

f) OCT:  This advanced diagnostic tool is called Optical Coherence Tomography, commonly  known as Eye Scan. This gives a lot of vital information on the thickness of  retinal nerve fiber layer and structural defect of the optic nerve head. This  instrument is also used to measure the corneal thickness which is useful to assess  the target pressure desired for each patient at every stage.

 g) Structural  and Functional Correlation: To conclusively diagnose Glaucoma we have to  clinically correlate the structural defect as detected by Optic Disc exam  /Photo & OCT with the functional defect as determined by Visual Fields.

  

7. Treatment

There are essentially three types  of treatments for the control of glaucoma. All are aimed at reducing the IOP to  the targeted level.

a) Medical: There are different medications for the control of this disease. Your doctor has to decide the best one for you taking into consideration its mechanism of action, side effects and your compliance issues as also the cost. Generally the medication needs to be taken life long.

b) Laser treatment: Two types of lasers have a role. YAG laser is done to create an opening in the iris to overcome the blockage of the fluid in cases of angle closure (Laser iridotomy). Argon laser can be used to increase the flow of fluid towards the drainage area (Laser Trabeculoplasty).

c) Surgery: In the event of both medical & laser options being ineffective, surgery may be required. The commonest surgical procedure done is Trabeculectomy.

8. Instructions  to the patients

  • Use your medications regularly: Make your medication a part of your daily routine. You may forget a meal but please use medication as per schedule. Fluctuation of IOP resultant due to poor compliance is bad & promotes progression of the disease. If you forget a dose, take it immediately when you remember & not wait for the next schedule.

• Your doctor is half of the treatment team. You are the other. While your doctor is your primary resource, you need to work with him to protect your vision. Compliance is the key.

• Stay informed & know your medication: It is recommended that you understand your disease & are also informed about the basic mechanism of action & side effects of the drug you are using.

• Pay attention to how your eyes feel and look: Watch out for any unusual changes & report immediately. Do not stop medication without consulting your doctor. The symptoms to watch out for are excessive irritation, itching, floaters, flashes of light, blurring of vision, congestion, discharge & headaches.

• If you are in control, don’t let Glaucoma limit your life: Barring a little requirement of medication there is nothing to stop you from leading a normal life. Develop a positive attitude to life.

• Regular exercises result in keeping glaucoma under control. It also has a beneficial effect on control of risk factors associated with glaucoma.

9. Remember

• Glaucoma is not curable but it can be properly controlled by medication.

• If it is left untreated it may result in total blindness.

• About 10% of patients may still have progression of loss of vision in spite of proper treatment.

• Regular check ups with your doctor goes a long way in keeping your disease in check.

• Consider Glaucoma not just as a disease but as a way of life & be positive.