Ophthalmology Flashcards
What is acute angle-closure glaucoma?
= an acute rise in intraocular pressure due to narrowing of the anterior chamber angle of the eye, causing optic nerve damage & sight loss.
- Ophthalmological emergency
What are the risk factors of acute angle-closure glaucoma?
- Increasing age → >65yrs
- Anatomical predisposition → shallow anterior chamber, short eyeball length, hypermetropia (long-sightedness)
- Family history
- Female → 4x more likely than men
- Chinese & East Asian ethnic origin
- Pupil mid-dilation → precipitates pupillary block
- Being in a dark room
- Medications → anticholinergics (oxybutynin), SSRIs
How does acute angle closure glaucoma present?
History:
- Symptoms develop over hours to days
- Patient may have been in a dark room when symptoms began, or may be taking medications that cause pupil dilation.
- Unilateral severe eye pain
- Associated headache, nausea, & vomiting
- Profound reduction in visual acuity or visual loss
- Rainbow colour halos around bright lights
- Red eye
- Hazy cornea → due to raised IOP causing corneal oedema
- Fixed, mid-dilated pupil which does not react to light
- Hard eyeball on gentle palpation → ask patient to close their eye & gently palpate
- Very high IOP → >30mmHg
What are the two key investigations for acute angle-closure glaucoma?
- Tonometry → typically >30mmHg
- Gonioscope → gold standard for assessing the angle between the iris & cornea. Mandatory for establishing the diagnosis
How is acute angle closure glaucoma managed?
Requires immediate admission & secondary care management. Conservative measures whilst waiting for an ambulance:
- Lie patient flat on their back → gravity helps bring the lens away & open the anterior chamber angle.
- Oral analgesia & antiemetic
- Pilocarpine eye drops → acts on the muscarinic receptors in the sphincter muscles, causing pupil constriction, helping the flow of aqueous humour.
- Acetazolamide → reduces the production of aqueous humour
Laser iridotomy → definitive treatment, where a hole is made in the iris using a laser, which allows the aqueous humour to drain directly from the posterior to anterior chamber.
What is retinal detachment, and what are the common causes?
= when the neurosensory layer of the retina (which contains the photoreceptors & nerves) separate from the retinal pigment epithelium.
- Neurosensory retina relies on blood vessels of the choroid for its blood supply → detachment can lead to damage to the photoreceptors, making it sight-threatening.
- Most commonly due to full-thickness retinal tear → allows the vitreous fluid behind the neurosensory retina.
- Other types:
- Tractional → vitreous membranes pull on the retina, causing it to separate. More common in patients with diabetic retinopathy.
- Exudative → underlying retinal disease leads to the build-up of exudative fluid underneath the retina.
How does retinal detachment present?
Symptoms:
- Painless loss of vision
- Flashing lights & floaters
- Cobwebs in peripheral vision
- Shadow or grey curtain moving across visual field → loss of peripheral vision
- Poor visual acuity
- Relative afferent pupillary defect
- Altered fundal reflex
- Slit lamp → tobacco dust (Shafer’s sign)
How is a retinal detachment managed?
- Vitrectomy
- Most common treatment for RD.
- Keyhole surgery on the eye, vitreous is drained, cryo/laser therapy is used to seal the retinal tear & the eye is then filled with an absorbing gas to hold it in place.
- Patient must maintain a head position post-operatively & cannot fly for 3-6 months.
What is a normal intraocular pressure?
10-21 mmHg
How does glaucoma present?
- May be asymptomatic & picked up on routine eye testing.
- Glaucoma affects the peripheral vision first → gradual onset of peripheral vision loss (tunnel vision), particularly in the superior visual field.
- Blurred vision
- Headaches
- Halos around lights, particularly at night
What is the gold-standard investigation for open-angle glaucoma?
- Goldmann applanation tonometer → gold standard
- Device is mounted on a slit lamp & makes brief contact with the cornea after using numbing eye drops.
- Measures the pressure needed to indent the cornea.
At what point is treatment commenced for open-angle glaucoma, and what does that involve?
Treatment will commence when IOP>24mmHg.
360 degree selective laser trabeculoplasty (SLT) → recommended for all newly diagnosed patients requiring treatment.
Medical Management:
- Involves a variety of eye drop preparations that either reduce the production or increases the outflow of aqueous humour.
- 1st line → prostaglandin analogue, eg latanoprost
- Increases uveoscleral outflow
- Side effects → eyelash growth, eyelid pigmentation, iris pigmentation
- Other eye drop options:
- Beta-blockers → eg, timolol, reduce the production of aqueous humour
- Carbonic anhydrase inhibitors → eg, dorzolamide, reduce production of aqueous humour
Surgical Management:
- Trabeculectomy → required where other treatments are ineffective.
How does optic neuritis present?
- Acute-subacute unilateral loss of vision
- Visual acuity can vary from being normal to (rarely) becoming ‘no perception of light’.
- Can be central scotoma or diffuse.
- Worsens over hours to days → recovery starts within 2 weeks
- Pain → retrobulbar & peri-ocular
- > 90% of cases
- Exacerbated by eye movements
- Can precede or occur with visual loss.
- Reduced contrast sensitivity & colour vision
Examination:
- Relative afferent pupillary defect → positive for the affected eye unless there is pre-existing disease in the contralateral eye.
- Optic nerve swelling & pallor
- Normal extraocular muscle movement
How is optic neuritis managed?
- High-dose corticosteroid therapy
- IV methylprednisolone → reduces the risk of developing MS for the first 2 years
What are the symptoms of age-related macular degeneration?
- Gradual loss of central vision
- Reduced visual acuity
- Metamorphopsia → crooked or wavy appearance to straight lines
- Symptoms can be bilateral or unilateral
- Wet AMD → presents more acutely, within days
