Treatment
Steps involved in treating glaucoma
- Confirm the diagnosis
- Quantify the amount of damage
- Set reasonable treatment targets (target pressure )
- Institute appropriate treatment
- Reassess response to treatment
- Maintain / Modify goals of treatment periodically
STEP 1: Confirm the diagnosis
The diagnosis of glaucoma involves the TOPG 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 computerized 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.
STEP2: Quantifying the amount of damage.
Quantifying structural damage to the optic nerve (disc morphometry) with the help of disc photography and Optical Coherence Tomography (OCT) 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: Establish 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
- IOP level prior to treatment
- 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 for 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. Adjustment of treatment to maintain the pre set goals if required, are made.
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.
Issues involved in treating glaucoma
One of the important principles in the management of glaucoma, which must be clearly defined and understood deals with what is glaucoma? In glaucoma damage to different eye tissues is common, however the primary concern is the damage to the optic nerve head. Put simply this damage to the optic nerve is at least partially related to the eye pressure.
Therapeutic goals of treatment in glaucoma?
The objective of treatment (irrespective of the disease) is to maintain or enhance a person’s health. In the context of glaucoma this would involve maintaining or enhancing the health of the person, restoring or at least preventing visual loss and enhancing the person’s emotional, spiritual, psychological and physical health without causing any damage by the therapeutic modalities used. That is to prevent further damage to the optic nerve. To date, the only proven method to prevent damage to the optic nerve head is by reducing the IOP.
- Awareness of goal of therapy is improvement or maintenance of one’s health.
- All treatments have side effects, hence no treatment can be justified without assessing the risk to benefits of treatment .
- It’s important to assess the clinical course of the disease. In early stages, there is ample time to make a decision. For many years, it was assumed that treating people with a raised eye pressure was beneficial, because it was believed that those with raised eye pressure developed visual field loss and become blind. Most patients with raised eye pressure were then treated. The amount of damage caused by treatment then, was probably more than that caused by the glaucoma itself. However, had they not been treated 90% of those individuals would never have developed damage to the optic nerve, while the treatment itself caused unnecessary problems. Only 5-10% of those with eye pressure more than 21 mmHg in the OHTS actually developed visual field loss, the possible benefit of treatment would need to be assessed more meaningfully.
- Therapies for glaucoma involve long-term These goals involve preserving vision. One needs to realize, from the beginning, that it is impossible to recover vision lost from glaucoma. However, it is possible to preserve whatever vision is left and this vision can usually be maintained for life.
- No two people respond to the same treatment in exactly the same way. Similarly, people will also differ in their type and severity of glaucoma. Hence treatment needs to be tailored to the individual patient taking into account several factor.
- Treating glaucoma is a two-way process involving communication between the doctor and patient. One of the best ways of combating blindness from glaucoma is for those involved to work together as a team. It is important to know as much about glaucoma as possible, so that one can ask questions that are important to oneself.
In fact, we welcome your asking these questions. The more one knows, greater the likelihood of being compliant with one’s therapy. The more one complies with therapy, the better it is to preserve one’s vision.
The treatment perspective
The objective of treatment (irrespective of the disease) is to maintain or enhance a person’s health. In the context of glaucoma this would involve maintaining or enhancing the health of the person, restoring or at least preventing visual loss and enhancing the person’s emotional, spiritual, psychological and physical health without causing any damage by the therapeutic modalities used. That is to prevent further damage to the optic nerve. To date, the only proven method to prevent damage to the optic nerve head is by reducing the IOP.
1) Awareness of goal of therapy is improvement or maintenance of one’s health.
2) All treatments have side effects, hence no treatment can be justified without assessing the risk to benefits of treatment .
3) It’s important to assess the clinical course of the disease. In early stages, there is ample time to make a decision. For many years, it was assumed that treating people with a raised eye pressure was beneficial, because it was believed that those with raised eye pressure developed visual field loss and become blind. Most patients with raised eye pressure were then treated. The amount of damage caused by treatment then, was probably more than that caused by the glaucoma itself. However, had they not been treated 90% of those individuals would never have developed damage to the optic nerve, while the treatment itself caused unnecessary problems. Only 5-10% of those with eye pressure more than 21 mmHg in the OHTS actually developed visual field loss, the possible benefit of treatment would need to be assessed more meaningfully.
4) Therapies for glaucoma involve long-term goals. These goals involve preserving vision. One needs to realize, from the beginning, that it is impossible to recover vision lost from glaucoma. However, it is possible to preserve whatever vision is left and this vision can usually be maintained for life.
5) No two people respond to the same treatment in exactly the same way. Similarly, people will also differ in their type and severity of glaucoma. Hence treatment needs to be tailored to the individual patient taking into account several factor.
6) Treating glaucoma is a two-way process involving communication between the doctor and patient. One of the best ways of combating blindness from glaucoma is for those involved to work together as a team. It is important to know as much about glaucoma as possible, so that one can ask questions that are important to oneself.
In fact, we welcome your asking these questions. The more one knows, greater the likelihood of being compliant with one’s therapy. The more one complies with therapy, the better it is to preserve one’s vision.
The treatment perspective
Treatment is usually begun with topical medication. If necessary, other topical or systemic drugs are added. When medication fails to control the intraocular pressure, laser energy applied to the trabecular meshwork (laser trabeculoplasty) may be used to increase aqueous outflow. When drugs and laser trabeculoplasty fail to control the intraocular pressure, a new route for aqueous egress can be created surgically.
Medical treatment
Medical treatment is both, an art and a science. The goal of treatment is to preserve visual function. Lowering the IOP is only a secondary goal. It is necessary to tailor the treatment to the needs of the patient and when doing so, the following need to be kept in mind –
A) The target tissues of topically applied ocular hypotensive medication are within the eye. Ocular conditions which can limit bio availability such as tear film deficiency, corneal scarring, chronic non-specific blepharoconjunctivitis and intra ocular inflammation and may co-exist.
B) Compliance with instructions for instilling eye drops can be improved by
- Being aware about nature of the disease
- Emphasizing need for life long treatment.
- Assessing ability to instill eye drops correctly and in accordance to dosage schedule.
- Being aware about possible side effects
- Avoiding eye drops with specific side effects, as part of individualized treatment.
- Use drops which affect the daily routine minimally.
- Can the treatment regimen maintain the desired target IOP for 24 hours in a day ?
- Is the patient amenable to follow up to assess the response to treatment?
- Simpler the treatment regimen, better the compliance.
- Fewer side effects mean better patient compliance.
- Topical preparations contain preservatives which may cause conjunctival inflammation and cytotoxic effects on the ocular surface. Preservative free preparations would be ideal, particularly when multiple drugs are being used.
Most drugs for glaucoma are applied topically. Because of the brief contact time and the strong protective barrier of the eye, the drug solutions need to be concentrated. Excess drug drains through the nasolacrimal duct into the nose, where it may be absorbed into the systemic circulation. For example, Timolol administered to one eye enters the bloodstream in a concentration sufficient to cause a measurable decrease in intraocular pressure in the opposite eye. Those who use topical drugs should occlude the nasolacrimal duct with either digital pressure or simple eyelid closure for about five minutes, this maneuver increases intraocular drug concentrations and decreases systemic concentrations.
There is no single accepted drug of choice in glaucoma therapy. The initial drug of choice could vary depending on the likely compliance with treatment, socioeconomic and health status of the patient, efficacy of the drug and the geographical location of the treating physician. The drug given initially to patients with most types of glaucoma is a non selective, topical beta adrenergic-antagonist drug, such as Timolol maleate (in the absence of any contraindication), because of the pressure lowering efficacy, long duration of action, and few ocular side effects of this class of drugs. A second drug, if needed, might be a prostaglandin analogue (such as Latanoprost / Bimatoprost /Travtoprost) or an alpha 2 adrenergic agonist (Brimonidine). However the choice of the initiating drug could also be a prostaglandin analogue or selective alpha 2 adrenergic agonists.
Topical carbonic anhydrase inhibitors (such as Dorzolamide) constitute the third choice. Cholinergic’s like Pilocarpine, have often been relegated to the last because of their ocular and visual side effects. However, in the Indian context they provide effective IOP lowering which is cost effective. It is important to select the right candidates – aphakes and pseudophakes who are not high myopes.
When therapy with a topical drug is instituted, it may be applied to one eye, with the opposite, untreated eye used as a control. This method makes it possible to determine whether any change in intraocular pressure is due to the drug or to the normal variation of intraocular pressure. However, this is usually not possible in the Indian scenario.
If there is no response, the drug is discontinued in order to avoid unnecessary costs and side effects. If there is a substantial decrease in intraocular pressure but the eye pressure remains high, another drug should be added. Different classes of drug have additive effects on intraocular pressure. Exceptions are nonselective beta adrenergic-antagonist drugs and nonselective adrenergic agonist drugs, which have little additive effect when given together. Cholinergic drugs and prostaglandins with adequate spacing can also be used together .
- Multiple drops are less likely to be instilled correctly as compared to single preparations.
- Combination drops are more likely to be instilled correctly than drops from multiple bottles.
- Fixed drug combinations offer the advantage of less toxicity by preservatives and lower costs, than fixed preparations.
- Combination therapy with identical mechanism of action should be avoided.
Although there are numerous medications available with different modes of action, about 2/3 of patients require combination treatment. With monotherapy a 25 % reduction can be expected in the relative IOP. From combination therapy 35% and from maximal medical therapy 40% of IOP reduction from baseline. A golden rule of treatment is to always use the least amount of drug, in the lowest concentration, least number of times such that one effectively gets the highest efficacy with the least possible side effects.
Other terms commonly used in the medical treatment of glaucoma are: – Maximal Medical Therapy (MMT): When a patient is on representative medication from each of the available groups of antiglaucoma medication. Maximal Tolerable Medical Therapy (MTMT): Maximal Medical Therapy where drugs to which the patient is intolerant, have been excluded, in an effort to achieve medical control of IOP. Systemic carbonic anhydrase inhibitors may be added if the IOP remains uncontrolled with MMT or in situations where the IOP is extremely elevated. The patient’s tolerance may dictate whether these medications are used for a short or long time. Because of the potential for side effects, they are not used on a long-term basis.
Surgical treatment
Glaucoma surgery is needed in patients who have a progressive visual field loss or optic nerve damage on maximal tolerable medical treatment. Indications for primary glaucoma surgery include:
- Patients who are poor candidates for conventional medical treatment.
- Patients in whom the target IOP is unlikely to be achieved with topical medications alone.
- Visual field loss is such that further progression is likely to affect the patient’s quality of life.
- Patients with rapidly progressive glaucomatous optic neuropathy where quality of life would suffer unless rapid IOP lowering occurs to the desired target level.
Filtering surgery reduces the IOP, medical treatment may still be required. Although effective in 85 to 95% of previously unoperated eyes, the potential success of the operation must by measured against the potential effect of complications on the patient’s quality of life. Although long-term control is often achieved with filtering surgery, many patients will require repeat surgery or supplemental medical management, or both. Glaucoma surgery combined with cataract extraction, may be indicated in patients who require visual rehabilitation with cataract extraction, in addition to IOP lowering.
Aqueous drainage devices are generally reserved as a last resort for patients with glaucoma that is refractory to standard filtering surgery. This includes patients with extensive conjunctival scarring, chronic inflammation, and ocular trauma. IOP lowering with glaucoma drainage devices is generally not superior to filtering surgery and has its own limitations. Cyclophotocoagulation is another alternative for patients with glaucoma that is refractory to other interventions and where the visual potential is poor.
Trabeulectomy with / without Mitomycin C is the most common form of surgery for glaucoma. It does not require an overnight stay and is done under local anesthesia. In this surgery a new passage is created within the walls of the eye and under the eye lid, bypassing the existing clogged drainage system. No foreign material is implanted. May not last a lifetime and may need to be supplemented with eye drops or needs to be repeated in the future.
Laser treatment
Laser’s in Open Angle Glaucoma
Most patients with open angle glaucoma can be controlled by antiglaucoma medications. Alternatively, Argon laser trabeculoplasty (ALT) / selective laser trabeculoplasty (SLT ) can provide a clinically significant reduction of IOP in some people. The advantages of trabeculoplasty over medical treatment include lack of systemic adverse effects, minimal patient compliance, and decreased incidence of ocular problems that could possibly compromise subsequent surgical therapy. However, it seldom reduces the number of required glaucoma medications. Also, the effect of this procedure is temporary. For these reasons and also because its efficacy has not yet been demonstrated in Indian eyes, laser trabeculoplasty is not considered a viable option in Indian eyes.
ALT: Uses an argon laser to mechanically open up the drainage spaces in the trabecular meshwork
SLT: Uses a frequency-doubled YAG laser to open up the drainage spaces in the trabecular meshwork by using the body’s own immune cells to remove the debris in the trabecular meshwork.
Lasers in Angle Closure Glaucoma
A laser iridotomy with the Nd YAG laser is required for those who have been diagnosed with narrow-angle glaucoma or where it is has been determined that the laser iridotomy is the appropriate treatment. A laser iridotomy involves placing a small hole in the brown part of the eye (iris) to create a passage for the fluid to drain from the back to the front of the eye. Without this new channel the eye pressure may build up rapidly causing damage to the delicate optic nerve which can cause a permanent loss of vision. A laser iridotomy can halt or prevent an attack of acute angle closure.
The iridotomy site is a small hole, usually positioned under the upper eyelid. It will not be noticed by you or anyone looking at you. The purpose of the iridotomy is to open the fluid passages/prevent them from closing further, thereby helping to control the eye pressure and thus preserve vision. Following the procedure, one may still require medication or other treatment options may need to be considered to keep the eye pressure in the desired range. The need for this additional treatment is dependant, in addition to an individual response on the extent of damage to the outflow channels / optic nerve prior to the iridotomy.
Diode laser in treatment of glaucoma
Typically, the diode laser is used as a destructive procedure when all possible modalities for control of glaucoma are unacceptable or have failed to lower the IOP. It is a non surgical procedure which may need to be repeated often. Diode cyclophotocoagulation (TSCPC) uses a diode laser to reduce the fluid production of the eye and is commonly used in eyes with poor vision.