2. Chronic-open angled Glaucoma

Definition: 

• Gradual increase in IOP due to clogging of the drainage system (trabecular meshwork).
• The most common type in the UK, affecting 2% of over-40-year-olds. This is why regular screening tests are important over the age of 40 years, especially in people with a family history.
• Gradual onset.
• Affects both eyes.
• Will generally be detected through routine primary care optician services rather than presenting to us in general practice. May present as gradual visual impairment.
• Usually raised IOP (can occur in some with normal IOP, so IOP measurement alone is not a good screening test for glaucoma. Optic disc examination and visual fields should also be assessed by someone with the appropriate expertise.
• Variants
  • Ocular HTN – Inc IOP (>21mmHG) with no VF loss o Normal tension Glaucoma – VF loss, disc cupping, but normal IOP

Rf’s/Etiology: 

• Myopia, older age, black race (x2 risk), family history (x3 risk), T2DM (X2 risk), Drugs (Corticosteroids), Anterior Uveitis (Risk of secondary open-angle glaucoma with corticosteroid treatment)
• People with w/ certain RFs are advised to have their eyes checked
  • >60, 2 yearly until 70, once 70 can be examined annually & is free under the NHS
  • >40 w/1^st-degree relative w/ open angle Glaucoma – can be checked annually & is free under NHS o >40 w/ black African family origin – checked annually

Symptoms: 

• Gradual onset may be detected via routine Optom examination or diabetic screening. Gradual symptom development with VA loss, Peripheral VF loss (tunnel-like)

Investigations/Signs:

• Optic nerve damage (disc cupping), optic disc pallor (atrophy), bayonetting of vessels

Treatment:

• (Treat if IOP >24)
  • Advise all pts >40 to have eyes checked (perimetry, tonometry, slit lamp) o 1^st line: latanoprost OD in the evening (prostaglandin analogue – increased outflow)
  • 2^nd line: timolol 0.25% BD (Beta blocker, dec secretion, often in combo with

1^st line), Dorzolamide TDS (dec secretion), Brimonidine BD (alpha-agonist) o The main treatment is laser trabeculoplasty

Medications For Glaucoma:

Pilocarpine:  

• Miotic agent
• Increases uveoscleral outflow
• Side effects: pupil constriction, headaches, blurred vision
• Contraindicated in anterior uveitis
• Utilised in acute closed-angle glaucoma

Prostaglandin analogues (Latanoprost):

• Increases uveoscleral outflow
• Side effects: iris brown pigmentation, changes in eyelash length

Beta blockers (Timolol):

• Decreases aqueous production
• Can be combined with prostaglandin analogues
• Contraindicated: under 18 years, heart block
• Utilised in chronic open-angle glaucoma

Carbonic anhydrase inhibitors:

• Dorzolamide and acetazolamide
• Decreases aqueous production

Sympathomimetics (Brimonidine):

• Dual action: increases uveoscleral outflow and decreases aqueous production – Side effects: dry mouth, hyperaemia

Key Information  

• Different classes of medication target varying mechanisms:
• Aqueous production reduction: beta blockers, carbonic anhydrase inhibitors
• Uveoscleral outflow increase: prostaglandin analogues, pilocarpine
• Dual action: sympathomimetics

Extra’s

• Driving & glaucoma:
  • Group 1 (car/motorcycle): Currently, you don’t need to inform the DVLA if glaucoma only affects one eye, and the other eye has a normal field of vision. You must tell the DVLA if you have glaucoma and have a medical condition in the other eye, or if you can’t meet the visual standards for driving. The DVLA must be informed if glaucoma affects both eyes.
  • Group 2 (HGV/PSV): You must tell DVLA if glaucoma affects one eye or both eyes

Glaucoma Reference