Glaucoma Flashcards
What is glaucoma?
Group of ocular disorders that result in optic nerve damage, often associated with increased intraocular pressure (IOP). *Glaucoma is the 2nd leading cause of blindness behind cataracts
Classification of glaucoma
Open angle Closed angle Normotension
Describe the flow of aqueous humour normally
The pressure balance of the eye is maintained by the flow of aqueous humour. The ciliary body produces the aqueous humour into the posterior chamber. The fluid then moves towards and around the iris, through the pupil and into the anterior chamber. The fluid drains via the trabecular meshwork (via Schlemm’s canal and into a vein) or by the uveoscleral outflow routes.
Picture/ draw out the simple anatomy of the flow pathway of aqueous humour
What is the anterior chamber angle?
The angle formed between the iris and the cornea
Define angle closure glaucoma
Glaucomatous Sx developing in a patient with increased IOP and narrow/closed anterior chamber angle *Often due to smaller eyes -> smaller chambers i.e. Asians
Classifications of angle closure glaucoma
Acute Chronic
Define open angle glaucoma
Glaucomatous Sx developing in pt with increased IOP and a properly opened angle *Often due to abnormal structural trabecular network
Define normotension glaucoma
Glaucomatous Sx developing in pt with normal IOP and properly open angle * Ass with vasospasm
What is occular HTN?
Increase IOP in patients without Sx of glaucoma or optic disk abnormalities NB: some people have increase IOP but no glaucoma, some people have normal IOP but glaucoma (normotension glaucoma)
What is tonometry?
Measurement of IOP
What is normal IOP?
12-20mmHg
What is pachmetry?
Measurement of the thickness of the cornea
What is gonioscopy?
Measurement of the anterior chamber angle
What are the risk factors of glaucoma?
- increased age - blacks and asians - FHx - Myopes and hyperopes - Corticosteroids - Thin cornea
What is acute angle closure glaucoma (AACG)?
Glaucomatous exacerbation due to an insufficient anterior angle leading to increase IOP
Causes of AACG
Intrinsic: narrow anterior angle anatomically (Asians) Extrinsic: anything that dilates the pupil leading to a AACG attack e.g. dark room, stress, antiACh, SSRIs, sympathomimetics
Pathophysiology of extrinsic cause of AACG
When the pupil dilates the iris relaxes and becomes convex, this leads to a decrease in the anterior chamber angle INSERT PIC
Sx of AACG
Severe ocular pain Red eye, N/V, dilated pupil
Dx of AACG
Tonometry - IOP > 50 mmHg with clinical Sx
Rx of AACG
1st line: IV acetazolamide: carbonic anhydrase inhibitor which reduces aq humour production Other: osmotic diuretic Then referral to opthalmologist Then tonometry, if IOP decreased then administer pilocarpine (parasympathomimetic - constrict pupils)
Causes of chronic angle closure glaucoma (CACG)
a. Periperhal anterior syncechiae (iris adhesions to the lens) b. Narrowed anterior angle (Asians, elderly, cataracts or lens thickening)
Sx of CACG
Pts are typically asymptomatic until alter in the course - mild blurring, visual field deficits, halos, redness and iris blotches (nothing like AACG)
Dx of CACG
Gonioscopy will differentiate CACG glaucoma from open angle glaucoma which presents and progresses similarly
Rx of CACG
Referral to ophthalmology for iridotomy (first line Rx) - burn hole in iris Anti-glaucoma medications needed after surgery
What is Primary Open Angle Glaucoma (POAG)?
anatomically open angle but with an obstructed and slowed drainage system outflow
____ is the most common form of glaucoma in Australia?
POAG
3 major clinical features of POAG
- Progressive visual field loss (peripheries to total blindness) 2. Progressive increase in cup to disc ratio of optic disc 3. Elevated IOP (NB: sometimes may be normal at initial Dx) with normal open anterior angle * pt may present without Sx or may be detected on routine eye exam due to optic disk abnormalities (inc cup:disc). Even if silent, pt will inevitably go on to develop Sx
In POAG what will the cup-to-disc ratio be?
> 0.5
What is the normal cup:disc ratio?
0.3
What is the cup of the optic disc?
White, cup like depression/area at the centre of the optic disc
Sx of POAG
Typically late course of disease: Visual field deficits - paracentral Rainbow halos Mild eye pain Redness
Dx of POAG
Referral to opthalmology with: Fundoscopy to look for optic disc changes Gonionscopy to rule out CACG Tonometery Slit lamp examination Visual field analysis
Describe the progressive change in visual field loss in POAG
Rx of POAG
Goal: decrease IOP by > 25% Medical: eye drops of: a. prostaglandin analogs*: latanoprost b. beta blockers*: timolol c. Alpha-2 agonist : brimonidine d. Miotics: pilocarpine (PNSmimetic) e. Carbonic anhydrase inhibitor Surgery: Argon laser trabeculoplasty (create drainage path for aq humour)
What is normal tension glaucoma?
Considered a type of POAG. Pt must have optic disc changes and may progress to Sx of glaucoma but IOP ALWAYS normal * associated with vasospasm (Hx of migraine, Raynaud’s syndrome)
