General Flashcards
Causes of poor fundal view for fundoscopy
Cataracts
Vitreous haemorrhage
Corneal scarring
Define: Amblyopia
Poor vision in an eye due to obstruction of vision during childhood.
- No anatomical abnormality in the eye.
-
Most common causes of amblyopia
Uncorrected hypermetropia
Constant squint
Carotid-cavernous fistula
- Definition
Connection between the ICA or ECA and venous networks of the cavernous sinus
- Leads to high flow shunt from ICA/ECA to venous drainage in cavernous sinus
- Causes impaired drainage of blood from the orbit.
Carotid-cavernous fistula
- Presentation
Proptosis
- pulsatile
Orbital bruit
Chemosis
Ptosis
Ocular misalignment,
Carotid-cavernous fistula
- Causes
Trauma (most common)
Spontaneous
Examples of IOP raising medications
Steroids
Tropicamide (pupil dilator, anticholinergic)
Ketamine
Examples of IOP lowering medications
Prostaglandin analogues (increases aqueous drainage via uveoscleral flow) - i.e. latanoprost
Beta-blockers (reduce aqueous production)
- i.e. timolol
Carbonic anhydrase inhibitor (reduce aqueous production)
- i.e. dorzolamide (topical), acetazolamide (systemic)
Alpha-2 agonist (reduces aqueous production, increases uveoscleral flow)
- i.e. apraclonidine
Mitotics (contracts ciliary muscles which increases trabecular meshwork drainage)
- i.e. pilocarpine
Osmotics (decreases aqueous volume)
- i.e. mannitol
Define keratometry
Measures the anterior corneal surface curvature
Corneal topography
- Definition
- Indications
Measures and quantifies the curvature of cornea
- Provides information about the whole corneal shape.
Indications
- Keratoconnus
- Astigmatism
- Laser eye surgery
- Contact lens fitting
ULTRASONIC PACHYMETRY
- definition
Investigation that uses ultrasound to measure the central corneal thickness (CCT)
Normal central corneal thickness ranges between…
530 and 545 micrometres
Side effects of fluorescence angiography (4)
Urine discolouration
Nausea
Vasovagal syncope
Anaphylaxis
Contraindication of fluorescence angiography
Shellfish allergy
Idocyanine green angiography
- Definition
- Contraindication
Uses near-infrared light to detect indocyanine green bound to albumin in the blood
- Helps to visualise choroidal vasculature
Contraindications
- Pregnancy
- Seafood allergy
- Iodine allergy
What does an electroretinogram (ERG) do?
Assess electrical activity of the retinal in response to a light stimulus
What does an electro-oculogram do?
Reflects the activity of photoreceptors and retinal pigmental epithelium
Indications of ERG and EOG
Best disease
Retinitis pigmentosa
Factors that can lead to incorrect tonometry measurements
Excessive fluorescein (overestimates IOP)
Low/high CCT
Astigmatism
Calibration errors
Gonioscopy
-Definition
Investigations that assess whether the iridocorneal angle is open or close
- Inability to visual all structures indicates a closed angle
Structures
- Schwalbe line
- Nonpigmented and pigmented trabecular network
- Scleral spur
- Ciliary body
Perimetry
- Definition
- Examples
Investigations to assess visual field defects
Examples
- Humphrey visual field analysis
- Goldmann visual field testing
Which cases have to be notified to the DVLA
Diplopia
Visual field defects
- i.e. retinitis pigmentosa, bilateral glaucoma
Nyctalopia (night blindess)
Blepharospasm (involuntary twitch/blinking)
The first and second most common causes of infectious blindness are…
1- Trachoma
2- Onchocerciasis (Onchocerca volvulus parasitic worm)
Deficiency of what vitamin is the most common cause of childhood nutritional blindess in Africa?
Vitamin A
