Aqueous Humour And IOP Flashcards
(20 cards)
What is the function of aqueous humour?
Source of nutrients for avascular tissues, removes waste products, maintains intraocular pressure (IOP)
Avascular tissues include the posterior cornea, trabecular meshwork, lens, anterior vitreous, and zonules.
Define aqueous humour.
The clear fluid that fills the anterior and posterior chambers of the eyeball.
What are the major components of aqueous humour?
- Various ions
- Carbohydrates
- Proteins
- Oxygen
- Carbon dioxide
- Water
- Urea
- Glutathione
How does the protein concentration in aqueous humour compare to plasma?
- Protein concentration ↓
- Glucose ↓
- Urea ↓
- Ascorbate ↑
What are the two pathways for aqueous humour outflow?
- Conventional/Trabecular route
- Unconventional/Uveoscleral route
What is the normal range of intraocular pressure (IOP)?
10-21 mmHg (average of 15)
List factors that can cause fluctuations in intraocular pressure.
- Exercise
- Heart rate
- Trauma
- Fluid intake
- Medications
- Body orientation
- Alcohol and recreational drugs
What primarily produces aqueous humour?
Active secretion (90%) in the non-pigmented epithelium of the pars plicata of the ciliary body.
What is the role of the blood-aqueous barrier?
Prevents blood from entering the aqueous to maintain transparency and immune privilege.
What is glaucoma?
An umbrella term for diseases that increase IOP, resulting in irreversible but potentially preventable vision loss via damage to the optic nerve.
Name the types of glaucoma.
- Primary Open Angle Glaucoma (POAG)
- Primary Angle Closure Glaucoma (PACG)
- Secondary Angle Closure Glaucoma (SACG)
- Secondary Open Angle Glaucoma
- Congenital
- Juvenile
What are common symptoms of Primary Angle Closure Glaucoma (PACG)?
- Severe, sudden ocular pain
- Red eye
- Reduced vision
- Decreased visual acuity
- Headache
- Nausea/vomiting
- Halos of light
- Unresponsive dilated pupil
- Firm eyeball
- High IOP (30-50)
- Large optic cup
What symptoms are associated with Primary Open Angle Glaucoma (POAG)?
- Can be asymptomatic
- Peripheral vision loss
- Arcuate scotoma on visual field testing
- Large optic cup
- Raised IOP (unless normal tension glaucoma)
List some medical treatments for glaucoma.
- Prostaglandin analogues
- Beta blockers
- Carbonic anhydrase inhibitors
- Alpha 2 agonists
- Miotics
What surgical treatments are available for glaucoma?
- Laser trabeculoplasty
- Trabeculectomy
- Shunt insertion
- Laser iridotomy for PACG
Define ocular hypotony.
A potentially vision-threatening condition where IOP falls below 5 mmHg, resulting in loss of structural stability of the globe.
What are the causes of ocular hypotony?
- Acute: Trauma, post-surgery
- Chronic: Medication use, chronic health problems
What pathology is associated with ocular hypotony?
Not enough formation of aqueous humour or excessive loss of aqueous humour.
What happens to the eyeball’s AP length in ocular hypotony?
The AP length shortens, causing the sclera to buckle.
How does ocular hypotony affect vision?
It can affect the macula, retina, and optic nerve, leading to vision impairment.
