6.1.8 Evaluates glaucoma risk factors to detect glaucoma and refer accordingly Flashcards
What is IOP determined by? What increases IOP and what decreases it?
– IOP determined by balance of Aqueous humour production and outflow. 10 -21mmHg normal variation. IOP determined by age, body position, exercise etc.
* Raising IOP – Age, Increase in BP, Valsalva Manoeuvre, Block or restricted TM, external pressure, cycloplegic and corticosteroids.
* Lowering IOP – Exercise, Decrease in BP, Anaesthesia, Ocular trauma, intraocular surgery, retinal detachment, inflammation.
What is ocular hypertension?
when IOP >21mmHg, with normal optic disc and VF. OHT describes individual who need to be more closely
observed for the onset of glaucomatous damage.
What is primary open angle glaucoma? RFs?
RFs: o Older Age
o Afro/Caribbean Race
o Thin Cornea
o Myopia of >4.00D
o FHG
Signs:
* VHG4
* IOPs >21mmHg
* Visual fields show glaucomatous changes
* Optic Nerve head shows glaucomatous changes
* C:D ratio asymmetry of >0.2 bilaterally
* Loss of ISNT rule
* Notching of the RNFL
* Baring, Bayonetting and Overpassing of the vessels around the optic nerve head
What is normal tension glaucoma? RFs?
Normal IOP, Optic disc – focal notching and haemorrhages, Women x2, VF defect close to fixation (paracentral scotoma)
RFs: women, Japanese ethnicity, Migraines & Raynauds (linked to lower BP)
What is acute angle closure glaucoma? RFs?
RFs: o FHG
o Age of >40
o Women
o Chinese Race
o Short axial length
o Hyperopia
o Dense cataract
Signs: * VHG1/closed
* IOPs above 40mmHg
* Painful red eye
* Corneal Oedema
* Haloes around lights
* Nausea
* Vision severely blurred
o With pupil block – apposition between lens and iris, mid dilated state, Iris bombe due to posterior pressure
build up
o Without pupil block – Plateau iris (deep central AC and shallow in periphery)
Describe Optic disc and NRR in glaucoma?
- Optic Disc
o Vertical elongation of the cup, thinning of the neuroretinal rim, Notching, Haemorrhages, Vascular changes,
Peripapillary Atrophy, NFL defect
o Optic disc size 1.33-2.66mm, correlates with size of optic cup and NRR - NRR – More important than the cup, loss of tissue from inner (nasal) edge is cardinal sign check for any focal
notching and haemorrhages. Asymmetry between the NRR in the eyes.
Describe C:D ratio, vascular changes, RNFL, PPA and Optic disc haemorrhages in glaucoma?
- CD Ratio - CD Ratio has high variability within the population, Asymmetry of >0.2 early sign of GON
- Vascular Changes – Kinking/ Bayonetting, Nasal migration, Bowing, Baring, Sharper appearing vessels
- RNFL – Red free light – look for striation, brightness, visibility of the peripapillary vessels, look for diffuse and
localised loss - Peripapillary Atrophy – Alpha zone: hypo/hyperpigmentation. Beta zone: atrophy of the RPE and choriocapillaries.
Large Beta zone correspond to thin NRR. Progression of beta zone = progression of glaucoma. - OD Haemorrhages – indicates progression, Splinter haemorrhages, transient, recurrent, precede notching, NFL
defect and field loss.
Describe small disc vs large disc and glaucoma?
- Small Disc and Glaucoma – damage is slow and mild – VF loss present despite normal disc appearance – PPA more important than disc changes.
- Large Disc and Glaucoma – in absence of info >0.5 examined for extra care – look for cup shape and changes in NRR
What VF defects may occur in glaucoma?
- nasal step
- temporal wedge
- arcuate defect
- paracentral scotoma
- tunnel vision
What is referral for glaucoma based on?
Progression of optic neuropathy
What is selective laser trabeculoplasty?
- 1st line NICE tx for POAG
- Laser triggers regeneration of cells in trab meshwork to increase & improve outflow of aqueous humour in OAG. Helps unclog drainage channel
- Decreases IOP by ~30%
- Procedure often repeated as wears off over time
- Q-switched frequency doubled Nd: YAG laser
What is trabeculectomy?
- Helps drain fluid out of eye and into small blister (a bleb) under conj.
- Op creates trapdoor for fluid to pass through, bupassing normal drainage channel therefore lowering IOP
- Awake, local anaesthetic, 1-2 hours
- Risks: cataract development, Infection of bleb
What is peripheral iridotomy?
- Nd: YAG laser used to create another drainage hole to decrease IOP and increase flow of aqueous
- Under top lid to avoid creating another pupil
- Normally used for ACG or narrow angles
What is iStent (MIGS)?
- 1mm tube inserted into drainage channel
- Made of titanium
- 2 or 3 iStents
- Aims to bypass blockages in drainage channel and improve flow of fluid out eye and decrease IOP
What is Ab-interno canaloplasty with iTrack (MIGS)?
- Canaloplasty cleans out drainage channel
- Ab-interno: drainage channel accessed from front of eye in front of pupil during surgery
- iTrack: tube inserted into drainage channel
- Gel injected through tube, opening up drainage channel & breaks any blockages. Flow of fluid increases, decreasing IOP
Describe prostaglandin analogues?
- e.g. Bimatoprost, Latanoprost
- Increases uveoscleral outflow by ciliary muscle relaxation (and some conventional trab outflow)
- decreases IOP 25-35%
- side effects: conj hyperaemia, periocular pigmentation, increases eyelash growth, irritation
- once at night
- Combo drop: Ganfort (bimatoprost and timolol)
Describe beta blockers?
- e.g. Timolol
- decreases aqueous production by blocking sympathetic pathways of ciliary epithelium
- decrease IOP by 20-25%
- Contraindications: asthma, chronic pulmonary conditions, heart conditions, hx of lung disease
- Combo drop: Ganfort (bimatoprost and timolol)
Describe carbonic anhydrase inhibitors?
- e.g. Brinzolomide, Dorzolamide
- Decreases aqueous production by inhibiting enzyme carbonic anhydrase which is found within ciliary epithelium
- Side effects: transient blurred vision, eye irritation, eye pain, FB sensation, hyperaemia
- Decreases IOP by ~20%
Describe adrenergic agonists?
- e.g. Brimonidine, Apraclonidine
- Decreases aqueous production and increases uveoscleral outflow
- Usually combined with other drops
- Decreases IOP ~20-25%
- High rate of allergy to Brimonidine
- Causes follicular conjunctivitis
- Contraindications: MAOI antidepressants (Increased risk of hypoteension), severe cardiac disease
- Side effectL dry mount, fatigue, low BP, blurred vision
Describe mitotic/cholinergic?
- e.g. Pilocarpine
- increases aqueous outflow and induces miosis
- contraindiations: uveitic, neovascular and other secondary ACG
- side effect: peripheral/night viison problems, brow pain, accomm spasm, RD and breaks, GI upset, heart block
