Open-angle glaucoma

Question 1

What is Open-angle glaucoma?

Answer 1

• A collection of disorders resulting in progressive optic neuropathy
• It is characterised by a normal angle between the iris and the cornea

Question 2

What is Ocular Hypertension?

Answer 2

• This refers to elevated IOP without the presence of changes seen in glaucoma
• This may offer an early opportunity to offer early treatment and prevent the development of visual loss
• IOPs greater than 21 mmHg are generally said to be raised

Question 3

What are the Risk Factors for Open- Angle Glaucoma?

Answer 3

• Age
• Afro-Caribbean heritage
• Raised intra-ocular pressure
• Diabetes
• Hypertension
• Family History
• Myopia

Question 4

What are the causes of Primary Open-Angle Glaucoma?

Answer 4

• Raised IOP appears central too many cases
• Though it is disputed as to whether this occurs due to increased production, reduced drainage, anatomical differences or a combination of factors.

Question 5

What are the causes of Secondary Open-Angle Glaucoma?

Answer 5

• Rare and normally due to reduced drainage of aqueous humour and raised IOP.
• Occur secondary to a process:
  1. Neovascular Glaucoma: neovascularisation that occurs due to ischaemia and impairs drainage of the aqueous humour
  2. Pseudoexfoliative Glaucoma: Deposits of pseudoexfoliative material in the trabecular meshwork impairs drainage of the aqueous humour
  3. Pigmentary Glaucoma: Deposits of pigment in the trabecular meshwork impairs drainage of the aqueous humour
  4. Uveitic Gluacoma: secondary to uveitis where inflammation leads to reduced outflow of aqueous humour
  5. Glucocorticoid-induced Glaucoma: Corticosteroids increase resistance to drainage of aqueous humour. Most common with topical drops may occur with any preparation of corticosteroids

Question 6

How do you make a diagnosis of Open-angle Glaucoma?

Answer 6

• Ophthalmoscopy: optic disk shows cupping in glaucoma
• Visual fields
• Intraocular pressure
• Gonioscopy: anterior chamber and internal drainage system
• Central corneal thickness: Pachymetry allows for the assessment of a patients corneal thickness

Question 7

What is the managment of Open-angle Glaucoma?

Answer 7

• Topical Prostaglandin analogue (Latanoprost): These reduce IOP by increasing the uveoscleral outflow. Contraindicated in pregnancy and breast feeding, cautions in those with COPD/Asthma. Brown pigmentation of the iris, pigmentation of the peri-ocular skin and local irritation
• Topical Beta-Block (Timolol): Lower aqueous humour production. Caution in Asthma and COPD
• Topical sympathomimetics (Brimonidine tartrate): These reduce IOP by lowering the production of aqueous humour and increased uveoscleral outflow. Cautions: Pregnancy, breast feeding, local irritation, dry mouth, unpleasant taste
• Carbonic anhydrase inhibitors (Acetazolamide, Brinzolamide): Reduction in the secretion of aqueous humour
• Topic miotics ( Pilocarpine): Induce miosis, pulls the iris away from the trabecular meshwork and improves the outflow of the aqueous humour. Caution: local irritation, myopia, vitreous haemorrhage and retinal detachment.

Question 8

What is first lime treatment in patients with suspected chronic open angle glaucoma and an IOP of 24 mmHg or greater?

Answer 8

• topical prostaglandin analogue is normally used as first lime therapy
• advanced disease surgery = pharmacological augmentation (Mitomycin C)

Question 9

What is second line treatment for someone with glaucoma?

Answer 9

• in those whom IOP is not reduced enough with topical prostaglandin analogues
• consider:
• A topical beta-blocker
• A topical carbonic anhydrase inhibitor
• A topical sympathomimetic
• Laser trabeculoplasty
• Surgery with pharmacological augmentation (mitomycin c)