Podcast Beta
Questions and Answers
What percentage of glaucoma patients have pressure within normal limits?
What is the purpose of the Circle of Zinn in the optic disc?
What is the characteristic of the cup in a normal optic disc?
What is a potential cause of increased intraocular pressure (IOP) in glaucoma?
Signup and view all the answers
What is the purpose of the scleral ring in the optic disc?
Signup and view all the answers
What is a common feature of the cup edge in the optic disc?
Signup and view all the answers
What is the recommended approach to define the edge of the cup?
Signup and view all the answers
What is a characteristic feature of an overhang in the disc?
Signup and view all the answers
What is the primary mechanism of angle closure glaucoma?
Signup and view all the answers
What is the recommended action for all angles of grade 1 (Van Herick)?
Signup and view all the answers
What is a key distinguishing feature of a glaucomatous defect?
Signup and view all the answers
What is a potential limitation of auto-perimetry?
Signup and view all the answers
What is a characteristic feature of an arcuate defect?
Signup and view all the answers
What is the recommended approach to confirm a glaucomatous defect?
Signup and view all the answers
What is a complication of CRAO?
Signup and view all the answers
What is a characteristic feature of a small disc?
Signup and view all the answers
What is the primary mechanism that can give rise to increased intraocular pressure?
Signup and view all the answers
What is the characteristic shape of the normal optic disc?
Signup and view all the answers
What is the function of the Short Posterior Ciliary Arteries?
Signup and view all the answers
What is the characteristic appearance of the neuro-retinal rim tissue?
Signup and view all the answers
What is a potential sign of glaucoma?
Signup and view all the answers
What is the purpose of using a 78 or 90D lens and slit-lamp?
Signup and view all the answers
What is the primary reason for not relying solely on the colour change from the pink of the rim to the pallor of the cup to define the edge of the cup?
Signup and view all the answers
In what type of angle closure glaucoma is the mechanism of pupil block relieved by iridotomy/iridectomy?
Signup and view all the answers
What is the primary purpose of referring all angles of grade 1 (Van Herick) for gonioscopy assessment?
Signup and view all the answers
What is the characteristic feature of a nasal step defect in a visual field?
Signup and view all the answers
What is the recommended approach to exclude alternative diagnoses in a patient with a glaucomatous defect?
Signup and view all the answers
What is the primary reason for using retinal vessels to define the edge of the cup?
Signup and view all the answers
What is the primary purpose of monitoring grade 2 angles (Van Herick) regularly?
Signup and view all the answers
What is the characteristic feature of a diffuse field loss in a visual field?
Signup and view all the answers
What is the primary purpose of considering the statistical analyses of the visual field machine?
Signup and view all the answers
What is the recommended approach to defining the edge of the cup in cases where there are no vessels as a guide?
Signup and view all the answers
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.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Description
Test your knowledge of the optic disc's anatomy and physiology, including its assessment and blood supply. Learn about the normal optic disc shape and cup appearance, and how to use tools like the direct ophthalmoscope. Ideal for students of ophthalmology and optometry.