GLAUCOMA MEDICATIONS

  Elevated Intraocular Pressure (IOP) is the main risk factor for optic nerve damage in glaucoma and lowering of IOP remains the method to limit the optic nerve damage. The IOP level which prevents further damage of optic nerve is known as target pressure. Greater the optic nerve damage, lower should be the pressure. With mild optic nerve damage IOP may remain around 20 while with severe visual field loss the IOP may be kept at 12 to 14.

Satisfactory medical management depends on good patient compliance. Missing the dose may cause temporary rise of IOP leading to optic nerve damage.

Various medications available are:

  Miotics : Pilocarpine.
  Beta blockers.
  Sympathomimetics.: Epinephrine and Dipivefrin.
  Carbonic anhydrase inhibitors.
  Alpha adrenergic agonists : Brimonidine.
  Prostaglandin analogues : Latanoprost , Unoprostone.
  Hyperosmotic agents : Glycerol , Mannitol.

Pilocarpine

Used from 1877
Very potent drug
It causes contraction of ciliary muscles leading to mechanical traction on scleral spur and trabecular meshwork and opening the pores in trabecular meshwork that increases the aqueous outflow .

  Limitation:

               Use 4 times a day.

  Side effects:

               Headache.
               Redness and watering.
               Change in glass power.
               Makes pupil small : This decreases the vision in patients with central cataract.
               Systemic toxicity : rare include pulmonary oedema, bronchospasm, nausea, vomiting and diarrhoea.

  Contraindications:

               Patients prone to retinal detachment.
               Post operative period and in glaucoma associated with inflammation as it may aggravate inflammation.
               Glaucoma associated with intraocular haemorrhage or neovascular glaucoma.
               Angle recession glaucoma and congenital glaucoma as it decreases uveoscleral out flow.
               May aggravate angle closure glaucoma by increasing the pupillary block.

Beta Blockers

Eg; Timolol and Levobunolol

  Mode of action: 

                It reduces aqueous humor production by acting on beta receptors in ciliary body.

  Dose:

               Twice or once a day.

  Side effects:

               Dry eye and irritation.
               Systemic: Increases asthma, reduces heart rate, fatigue ,depression and anxiety, 
                  masking of hypoglycaemic symptoms and sexual dysfunction ( occasionally ).
            
  Contraindications:

               Bronchial asthma. Chronic bronchitis and pulmonary obstructive diseases.
               Heart block and congestive heart failure.

Selective Beta blockers

Eg: Betaxolol

Lesser efficacy and lesser systemic side effects so better with patients having contraindication for Beta blockers.
Causes more burning sensation.
           
Sympathomimetics

  Mode of action: 

                  It decreases aqueous humor production and increase aqueous outflow by trabecular meshwork and
                     uveoscleral outflow.

  Dose:

               Twice a day.

  Side effects:

               Redness and irritation.
            
  Contraindications:

               Narrow angle glaucoma as it causes dilatation of pupil .
               After cataract operation as may cause cystoid macular oedema.

This is second line of drug that is given with other medications.
             
Carbonic anhydrase inhibitors

  Mode of action: 

              Reduce aqueous humor formation.

  Side effects:

               Mainly systemic :
      
                         Tingling and burning sensation at fingers ,toes and around mouth.
                         Frequent urination. 
                         Malaise ,fatigue, weight loss, loss of appetite.
                         Depression and loss of sexual desire.
                         Abdominal discomfort , metallic taste , nausea and diarrhoea.
                         Formation of renal stones.
                         Aplastic anaemia and bone marrow depression.

               Local: 

                         Rarely transient myopia and choroidal detachment.
             
  Contraindications:

               Allergy to sulfa drugs.
             
Topical Carbonic anhydrase

Eg: Dorzolamide, Brinzolamide

Less effective than oral carbonic anhydrase but has very few systemic side effects. Long use may cause pseudodendritic ulcer.


Brimonidine

  Dose: 

               Topical two to three times a day.

  Mode of action: 

               Decrease aqueous production and increase uveoscleral outflow.

  Advantage: 

               Lowers nocturnal aqueous outflow.
               Reduces the optic nerve damage ( experimental studies ).

  Side effects:

               Ocular allergies as lid oedema, irritation and redness.
               Dry mouth.
               Headache.
               Depression and anxiety.

Latanoprost

  Mode of action: 

                  Increase uveoscleral outflow.

  Dose:

               Once a day preferably at night as a drop. 

  Side effects:

               Change in iris color.
               Increase in size of eyelashes.
               Pigmentation of skin around the eyes.
               Redness of eye.
               Uveitis,
               Cystoid macular oedema.
            
  Contraindications:

               Use with pilocarpine as has contradictory effect.
                         
No systemic side effects

Unoprostone

  Dose: 

               Twice a day drop.

  Less effective than latanoprost