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| Steps involved in treating glaucoma : |
1) Confirm the diagnosis
2) Quantify the amount of damage
3) Set reasonable treatment targets (target pressure )
4) Institute appropriate treatment
5) Reassess response to treatment
6) Maintain / Modify goals of treatment periodically
STEP 1 : Confirm the diagnosis
The diagnosis of glaucoma involves the TOP- G test
Tonometry to assess the eye pressure . It needs to be done at every visit using an instrument which uses blue light .
Ophthalmoscopy to look at the optic nerve in the back of the eye. Damage to the optic nerve can result in blindness and is the end point of glaucoma . The aim of early detection and treatment is to ensure that further damage to the optic nerve does not take place.
Perimetry is a computerised test to assess the field of vision. As the disease progresses causing damage to the optic nerve, the field of vision ( part of space we see with one eye closed ) gradually gets restricted .
Gonioscopy involves a special contact lens being placed over the eye to look at the fluid outflow facility. What kind of glaucoma one has is determined by this test alone. It is essential to know the type of glaucoma one has because treatment varies depending on the type of glaucoma . The open type of glaucoma is usually treated first with drops failing which a glaucoma surgery may need to be done. The closed type of glaucoma is usually treated with a laser iridotomy. If required, medication in the form of drops may also be required (depending on the severity) . When these don't work a glaucoma surgery may need to be considered.
A relevant medical history must complement the examination for diagnosis.
STEP 2 is about quantifying the amount of damage.
Quantifying structural damage to the optic nerve (disc morphometry ) with the help of disc photography, optical coherence tomography (OCT), nerve fibre layer analyzer (GDXVcc) and the Heidelberg retina tomograph (HRT ) are essential.
Quantification of damage to the optic nerve also requires as a pre requisite functional assessment of the optic nerve with the help of automated perimetry ( Octopus / Humphrey) prior to quantifying the structural damage .
STEP 3: Establishing treatment targets
Though we realize that factors other than eye pressure may be involved in the development of glaucoma, currently eye pressure is the only factor we can modulate .
CHOOSING A TARGET PRESSURE : It is difficult to specify exact guidelines for target IOP levels, the following levels may be used as a reasonable guide
1. IOP level prior to treatment
2. Optic nerve related damage
3. Rate of progression of glaucoma
4. Age of patient
5. Life expectancy of patient
6. Presence of other risk factors necessitates lower IOP .
The target pressure varies amongst patients and may need to be modified during the course of the disease, especially if damage to the ONH progresses despite IOP's within the desired target range.
STEP 4: Treatment
Treatment involves reducing the eye pressure by decreasing the amount of aqueous humor produced by the ciliary body or by increasing its outflow through the trabecular meshwork, through the uveoscleral pathway, or through a surgically created pathway.This can be done by medical / laser / surgical methods . Please refer to section on treating glaucoma in more detail.
STEP 5: Assessing response to treatment
After institution of treatment, usually a followup visit in 3-4 weeks would need to be scheduled (or as the situation demands) . Response to treatment is not just to assess the efficacy of the treatment, but also to look for side effects of treatment, clarify any additional apprehensions / concerns. If all is well treatment is continued.
Step 6: Maintain / Modify goals of treatment periodically
With continuation of treatment, periodic assessment of the eye pressure and optic nerve status is done with the help of tests which assess structural and functional integrity of the nerve. Since damage cannot be reversed, the emphasis is more on prevention of further damage. Its like taking the car for servicing at regular intervals. Adustment of treatment to maintain the pre set goals if required, are made.
The glaucoma, if it shows subtle signs of worsening, will requiring modification of treatment .This is possible only if these progressive changes are detected early. Overall, the aim is to preserve vision and hence maintain one's quality of life.
Excerpts from the lecture "A step by step approach to treating glaucoma" by Dr. Devindra Sood at India Habitat Centre ,New Delhi, second glaucoma meeting organized by the S K Glaucoma Care Foundation, New Delhi, June 2007 |
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