Under Pressure: Part 2 Treatment of Glaucoma
By: Ellie BatesFollowing on from our last newsletter discussing the diagnosis of glaucoma, this time we will dive further into the treatment of glaucoma cases.
As with most conditions, treatment for glaucoma is split into medical and surgical management with medical management being the most common first choice.
Medical Management
There are three types of glaucoma medications available to use in our patients.
Carbonic Anhydrase Inhibitor
- The enzyme carbonic anhydrase plays an important role in aqueous production and is found in the ciliary body
- Carbonic anhydrase inhibitors reduce the production of aqueous by preventing the enzyme from working
- Reduces IOP by 5-10mmHg
- Can be used in chronic and acute cases
- Good choice for feline patients
- However, make owners aware this treatment can lead to periorbital dermatitis and conjunctivitis .
Drug names: Dorzolamide (Trusopt) and Brinzolamide (Azopt)
Β-Blockers
- Reduce blood flow to the ciliary body which in turn reduces aqueous production
- Limited use as sole drug so often found in combination drops with a carbonic anhydrase inhibitor
- Use with care in patients with cardiac and respiratory disease
- On own will drop IOP by 5-10mmHg but in a combination drop, IOP can be reduced by 10-20mmHg
Drug names: Cosopt (Dorzolamide and Timolol) or Azarga (Brinzolamide and Timilol)
Prostaglandin Analogues
- Only for canine patients
- Very potent drugs and will lower IOP quickly – by 50mmHg in one hour
- Act by increasing the outflow through the uveoscleral route of aqueous drainage
- Use with care in cases of primary uveitis with secondary glaucoma because this drop does cause inflammation so will worsen uveitis
- Do not use in cases of anterior lens luxation with secondary glaucoma because they cause miosis which then traps the luxated lens in the anterior chamber
Drug names: Xalatan (Latanoprost) or Travatan (Travoprost)
Remember glaucoma is a painful condition so alongside topical glaucoma medication always dispense multi-modal pain relief!
The mainstay of glaucoma treatment is medical but there are some surgical options that can be considered in certain cases. These are available at larger referral centres but are not commonly performed. Examples include:
- Cyclocryoablation – destruction of the ciliary body by application of intense cold.
- Cyclophotocoagulation – destruction of the ciliary body by laser.
- Filtration devices – aim to provide a shunt and allow aqueous drainage into the subconjunctival space.
In all glaucoma cases, enucleation should also be discussed as, even with prompt diagnosis and a good response to medical management, eventually the IOP will raise again.
Having a discussion about enucleation at first diagnosis of glaucoma means clients are forewarned and able to better prepare for this procedure should it be required in the future.
