Open Angle Glaucoma Flashcards
(19 cards)
Normal intraocular pressure is []-[] mmHg, created by the resistance to flow through the trabecular meshwork
Normal intraocular pressure is 10-21 mmHg, created by the resistance to flow through the trabecular meshwork
Describe the flow of aqueous humour in the eye [4]
Produce in the ciliary bodies
Flows from posterior chamber to the anterior chamber and then into the trabecular meshwork into the canal of schlemm
Describe the anatomy of the optic disc and cup
Optic cup is found within the optic disc
- Normally the optic cup is half the size of the optic disc, if bigger than is abnormal
Describe the pathophysiology of open-angle glaucoma [+]
With open-angle glaucoma, there is a gradual increase in resistance to flow through the trabecular meshwork.
- The pressure slowly builds within the eye.
- Raised intraocular pressure causes cupping of the optic disc. In the centre of the optic disc is an indent called the optic cup.
- The optic cup usually is less than 50% of the size of the optic disc.
- Raised intraocular pressure causes this indent to become wider and deeper, described as “cupping”. A cup-disk ratio greater than 0.5 is abnormal.
Glaucomas can be classified based on whether the peripheral iris is covering the trabecular meshwork, which is important in the drainage of aqueous humour from the anterior chamber of the eye. In open-angle glaucoma, the iris is clear of the meshwork
Describe the risk factors for open-angle glaucoma [+]
Increasing age
Family history
Black ethnic origin
Myopia (nearsightedness)
HTN
Corticosteroid use
DM
How does open glaucoma present? [
The rise in intraocular pressure may be asymptomatic for a long time and diagnosed by routine eye testing.
- Glaucoma affects the peripheral vision first, resulting in a gradual onset of peripheral vision loss (tunnel vision) - nasal scotomas progressing to ‘tunnel vision’
* Fluctuating pain
* Headaches
* Blurred vision
* Halos around lights, particularly at night
Describe the fundoscopy signs of POAG [4]
- Optic disc cupping - cup-to-disc ratio >0.7 (normal = 0.4-0.7), occurs as loss of disc substance makes optic cup widen and deepen
- Optic disc pallor - indicating optic atrophy
- Bayonetting of vessels - vessels have breaks as they disappear into the deep cup and re-appear at the base
- Additional features - Cup notching (usually inferior where vessels enter disc), Disc haemorrhages
Name and describe the gold standard investigation for assessing the draining angle of the anterior chamber between the iris and cornea [1]
Gonioscopy is the gold standard investigation for assessing the drainage angle of the anterior chamber between the iris and cornea.
How do you measure intraocular pressure? [1]
Non-contact tonometry is the commonly used machine for estimating intraocular pressure by opticians. It involves shooting a “puff of air” at the cornea and measuring the corneal response. It is less accurate but gives an estimate for general screening purposes
- Goldmann applanation tonometry is the gold-standard way to measure intraocular pressure. It involves a device mounted on a slip lamp that makes contact with the cornea and applies various pressures.
Dx of PAOG is based off which assessments? [5]
- Goldmann applanation tonometry for the intraocular pressure
- Slit lamp assessment for the cup-disk ratio and optic nerve health
- Visual field assessment for peripheral vision loss
- Gonioscopy to assess the angle between the iris and cornea
- Central corneal thickness assessment
At what IOP do you start treatment for PAOG? [1]
Treatment is typically started at an intraocular pressure of 24 mmHg or above.
Describe the management plan for PAOG [+]
First line: - 360° selective laser trabeculoplasty is recommended in the NICE guidelines (updated 2022) for all patients needing treatment. - During the procedure, a laser is directed at the trabecular meshwork, improving drainage. It may delay or prevent the need for eye drops. A second procedure may be necessary at a later date.
Medical Mx:
- Prostaglandin analogue eye drops (e.g., latanoprost)
- are the first-line medical treatment. They increase uveoscleral outflow.
- Beta-blockers (e.g., timolol) reduce the production of aqueous humour
- Carbonic anhydrase inhibitors (e.g., dorzolamide) reduce the production of aqueous humour
- Sympathomimetics (e.g., brimonidine) reduce the production of aqueous fluid and increase the uveoscleral outflow
Trabeculectomy surgery may be required where other treatments are ineffective.
- This involves creating a new channel from the anterior chamber through the sclera to a location under the conjunctiva, causing a bleb on the conjunctiva. From here, it is reabsorbed into the general circulation.
NB: 360° SLT can delay the need for eye drops and can reduce but does not remove the chance they will be needed at all
Name a side effect of latanoprost treatment? [3]
Notable side effects are eyelash growth, eyelid pigmentation and iris pigmentation (browning).
The following are all medications for PAOG.
Which should be avoided in asthmatics?
- Prostaglandin analogues (e.g. latanoprost)
- Beta-blockers (e.g. timolol, betaxolol)
- Sympathomimetics (e.g. brimonidine, an alpha2-adrenoceptor agonist)
- Carbonic anhydrase inhibitors (e.g. Dorzolamide)
- Miotics (e.g. pilocarpine, a muscarinic receptor agonist)
- Beta-blockers (e.g. timolol, betaxolol)
The following are all medications for PAOG.
Which should be avoided in patients taking MAOI or TCA antidepressants?
- Prostaglandin analogues (e.g. latanoprost)
- Beta-blockers (e.g. timolol, betaxolol)
- Sympathomimetics (e.g. brimonidine, an alpha2-adrenoceptor agonist)
- Carbonic anhydrase inhibitors (e.g. Dorzolamide)
- Miotics (e.g. pilocarpine, a muscarinic receptor agonist)
The following are all medications for PAOG.
Which should be avoided in patients taking MAOI or TCA antidepressants?
- Prostaglandin analogues (e.g. latanoprost)
- Beta-blockers (e.g. timolol, betaxolol)
- Sympathomimetics (e.g. brimonidine, an alpha2-adrenoceptor agonist)
- Carbonic anhydrase inhibitors (e.g. Dorzolamide)
- Miotics (e.g. pilocarpine, a muscarinic receptor agonist)
The following are all medications for PAOG.
Which have adverse effects including a constricted pupil / headache / blurred vision?
- Prostaglandin analogues (e.g. latanoprost)
- Beta-blockers (e.g. timolol, betaxolol)
- Sympathomimetics (e.g. brimonidine, an alpha2-adrenoceptor agonist)
- Carbonic anhydrase inhibitors (e.g. Dorzolamide)
- Miotics (e.g. pilocarpine, a muscarinic receptor agonist)
The following are all medications for PAOG.
Which have adverse effects including a constricted pupil / headache / blurred vision?
- Prostaglandin analogues (e.g. latanoprost)
- Beta-blockers (e.g. timolol, betaxolol)
- Sympathomimetics (e.g. brimonidine, an alpha2-adrenoceptor agonist)
- Carbonic anhydrase inhibitors (e.g. Dorzolamide)
- Miotics (e.g. pilocarpine, a muscarinic receptor agonist)
An elderly patient with a history of hypertension presents with decreasing visual acuity and peripheral visual field loss. Fundoscopy reveals optic disc cupping - primary open-angle glaucoma
Muscarinic agonist
