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Questions and Answers
Approximately what percentage of glaucoma patients have pressure within normal limits?
What is the name of the artery that supplies the optic disc?
What is the term for the imbalance in anterior fluid dynamics that can give rise to increased IOP?
What is the name of the structure that is usually pale and allows it to be distinguished from the neuro-retinal rim tissue?
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What is the term for the localised loss of nerve fibre layer?
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What is the shape of the normal optic disc?
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What is the primary method to define the edge of the cup?
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In which type of glaucoma is pupil block a contributing factor?
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What is the recommended course of action for all angle closure glaucoma cases?
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What is the primary purpose of gonioscopy assessment in glaucoma?
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What is the characteristic of a nasal step defect in glaucoma?
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What is the purpose of NICE guidelines in glaucoma management?
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What is the characteristic of an artefact in auto-perimetry?
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What is the primary purpose of evaluating the visual field in glaucoma?
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What is the recommended course of action for a patient with a possible cilio-retinal vessel?
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What is the characteristic of a diffuse field loss in glaucoma?
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What is the primary function of the Short Posterior Ciliary Arteries in the optic disc?
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What is the implication of an imbalance in anterior fluid dynamics on the optic disc?
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What is the characteristic of the scleral ring in the optic disc?
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What is the significance of the neuro-retinal rim tissue in the optic disc?
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What is the purpose of assessing the optic disc in glaucoma?
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What is the characteristic of the cup in the optic disc?
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In cases where the edge may be an overhang, what can be used to help identify the cup edge?
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What is the term for the mechanism that can cause angle closure in primary glaucoma?
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What is the recommended course of action for patients with angle closure glaucoma?
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What is the purpose of evaluating the visual field in glaucoma?
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What can cause a false positive result in auto-perimetry?
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What is the recommended course of action for patients with grade 1 angles (Van Herick)?
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What is the purpose of NICE guidelines in glaucoma management?
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What type of glaucoma is associated with pupil block and bowing of the iris forward?
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What is the characteristic of an arcuate defect in glaucoma?
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What is the purpose of evaluating the retinal nerve fibre layer (RNFL) in glaucoma?
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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.
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Description
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.
