32 Questions
Approximately what percentage of glaucoma patients have pressure within normal limits?
30%
What is the name of the artery that supplies the optic disc?
Central Retinal Artery
What is the term for the imbalance in anterior fluid dynamics that can give rise to increased IOP?
An imbalance in anterior fluid dynamics
What is the name of the structure that is usually pale and allows it to be distinguished from the neuro-retinal rim tissue?
Scleral ring
What is the term for the localised loss of nerve fibre layer?
Nerve fibre layer defect
What is the shape of the normal optic disc?
Slightly vertically oval
What is the primary method to define the edge of the cup?
Using vessels to identify the point of maximum change of direction
In which type of glaucoma is pupil block a contributing factor?
Primary angle closure glaucoma
What is the recommended course of action for all angle closure glaucoma cases?
Refer all cases urgently, phone RAES
What is the primary purpose of gonioscopy assessment in glaucoma?
To evaluate the anterior chamber angle
What is the characteristic of a nasal step defect in glaucoma?
A defect that respects the horizontal raphe
What is the purpose of NICE guidelines in glaucoma management?
To offer recommendations for 80% of clinical situations
What is the characteristic of an artefact in auto-perimetry?
A high plus or trial lens effect
What is the primary purpose of evaluating the visual field in glaucoma?
To monitor the progression of the disease
What is the recommended course of action for a patient with a possible cilio-retinal vessel?
Refer the patient to a specialist for further evaluation
What is the characteristic of a diffuse field loss in glaucoma?
A widespread defect in the visual field
What is the primary function of the Short Posterior Ciliary Arteries in the optic disc?
To supply the optic nerve head
What is the implication of an imbalance in anterior fluid dynamics on the optic disc?
It can give rise to increased IOP
What is the characteristic of the scleral ring in the optic disc?
It is usually pale and allows it to be distinguished from the neuro-retinal rim tissue
What is the significance of the neuro-retinal rim tissue in the optic disc?
It is a normal part of the optic disc anatomy
What is the purpose of assessing the optic disc in glaucoma?
To identify potential signs of glaucoma
What is the characteristic of the cup in the optic disc?
It is usually horizontally oval and may be sloped
In cases where the edge may be an overhang, what can be used to help identify the cup edge?
Stereo cues and vessel direction changes
What is the term for the mechanism that can cause angle closure in primary glaucoma?
Pupil block
What is the recommended course of action for patients with angle closure glaucoma?
Urgent referral to RAES for management
What is the purpose of evaluating the visual field in glaucoma?
To assess optic nerve damage
What can cause a false positive result in auto-perimetry?
Trigger happy responses
What is the recommended course of action for patients with grade 1 angles (Van Herick)?
Referral for gonioscopy assessment
What is the purpose of NICE guidelines in glaucoma management?
To provide recommendations that will apply to 80% of clinical situations on 80% of occasions
What type of glaucoma is associated with pupil block and bowing of the iris forward?
Primary angle closure glaucoma
What is the characteristic of an arcuate defect in glaucoma?
A defect that follows the course of the RNFL
What is the purpose of evaluating the retinal nerve fibre layer (RNFL) in glaucoma?
To identify corresponding ONH changes
Study Notes
Optic Disc Assessment and Anatomy
- 30% of glaucoma patients have pressure within normal limits, and large numbers of fibers can be lost before a visual field defect can be demonstrated.
- Tools used to assess the optic disc: 78 or 90D lens and slit-lamp, and direct ophthalmoscope.
- The normal optic disc head is slightly vertically oval, and a normal cup often appears slightly horizontally oval.
Blood Supply to the Optic Nerve Head
- Short Posterior Ciliary Arteries
- Circle of Zinn
- Ophthalmic Artery
- Central Retinal Artery
- Lamina Cribrosa
Aqueous Fluid Dynamics and Glaucoma
- An imbalance in anterior fluid dynamics can give rise to increased IOP.
- Examples: angle closure/narrowing, pseudoexfoliation, PDS, anterior chamber inflammation, trauma.
Signs of Glaucoma
- Enlargement of the cup
- Localized loss of neuroretinal rim (NRR)
- Pallor
- Vessel deviations
- PPA (peripapillary atrophy) disc hemorrhages
- Nerve fiber layer defect
- Lamina cribrosa
Defining the Edge of the Cup
- The inner edge of the neuroretinal rim (=cup edge) may be sloped (especially on the temporal side of the disc) or vertical.
- Use small to medium-sized blood vessels to define the cup edge by tracing their path across the scleral ring and then over the rim tissue.
Additional Points
- Larger discs (>2mm) tend to display larger cup-disc ratios.
- Cupping in small discs increases the risk of BRVO (branch retinal vein occlusion).
- Proliferative diabetic retinopathy and carotid artery obstruction are related to CRAO (central retinal artery occlusion).
Angle Closure Glaucoma
- Primary: 0.5% prevalence in age >40, associated with pupil block, causing bowing of the iris forward leading to angle closure.
- Secondary: variety of mechanisms other than pupil block (not relieved by iridotomy/iridectomy).
- Refer all angle closure urgently, and consider referral of all angles of grade 1 (Van Herick) for gonioscopy assessment.
Visual Fields Revision
- Glaucomatous defect: look for corresponding optic nerve head changes.
- Exclude alternative diagnoses.
- NICE guidelines: look for unequivocal, suspicious, and early signs of glaucoma.
NICE Guidelines on Fields
- Threshold or suprathreshold: glaucomatous changes of the visual field that reflect nerve fiber bundle loss.
- Unequivocal signs: arcuate scotomas, nasal steps, altitudinal scotomata, focal defects, and absolute defects.
- Suspicious signs: generalized defect, relative defect, and enlarged blind spot.
- Early stages: mean defect >-6dB, 5% probability level defect for.
Assess your knowledge of the optic disc anatomy and physiology, including the normal appearance of the optic disc, blood supply, and tools used for assessment. This quiz covers important concepts for glaucoma diagnosis and treatment.
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