Lecture 7: Optic disc in glaucoma Flashcards
At what stage of glaucoma is a px likely to show a visual field defect?
25% retinal ganglion cell death
What is the appearance of a normal optic disc?
*Healthy and pink neural retinal rim
*Relatively small cup to disc ratio
*White physiological scleral rim (elschning)
*Yellow-white sieve-like appearance of lamina cribrosa
*Rim width configuration-ISNT rule
What optic disc changes can you get in glaucoma?
*Enlargement of optic cup
*Loss of disc rim (neural tissue)
*Vascular changes
*Increased pallor (if pallor is most predominant feature without the cupping, can be other optic neuropathy like AION.)
*Pre-papillary atrophy
*RNFL changes
-optic disc atrophy
What type of optic cup enlargement is more worrying?
disc is more vulnerable in superior and inferior pole. Vertical cupping is more significant.
*Inter-eye asymmetry
*Lamina baring or backwards bowing
*ISNT and notch
generalised enlargement is more common
What are the correction factors for disc diameter for different volk lenses?
superfield: 1.5
90D: 1.4
78D: 1.1
66D: 1.0
What vascular changes can you get to the optic disc?
*Vessel configuration
-nasalisation
-bayonetting-deflection
Flyover/overpass
-circumlinear baring
*Calibre of vessels-narrowing
*Collateral vessels-where someone has had CRVO associated with raised IOP
*Haemorrhage
What is disc hemorrhage a sign of?
Where is it most common?
*Active sign of progression
-can be other causes
*Common in NTG
*More common in inferior-temporal sector
*Can come and go as they can reabsorb in 6 weeks
*Can reoccur
What are the types of peri-papillary atrophy?
Where do you normally get it?
*a-zone: further out. Partial thinning
*b-zone: closer to optic disc. More concerning.
*Usually corresponds to area of maximum neuro-retinal rim thinning and visual field loss
What is the optic disc checklist for glaucoma?
is the vertical C/D ratio more than 0.5?
is the C/D ratio consistent with disc size?
Is the cup more vertically oval than the disc?
does the rim differ from ISNT rule?
any notches or pallor regions in NRR?
any disc haemmoraghes?
is the inter-eye C/D ratio asymmetry more than 0.2?
has there been a change of more than 0.15 in C/D ratio?
How should you record your assessment of the optic disc?
How can you categorise disc size?
sketch
mention volk used
measure height of disc
1.SMALL (less than 1.5 mm)
2.MEDIUM (1.5-2.00 mm)
3.LARGE (more than 2.00mm)
What defect can you get for RNFL assessment?
wedge-shaped defect
What congenital disc abnormalities can you get?
coloboma
optic disc pit
titled disc
drusen
myelinated fibres
myopic disc
What vf defects can you get for glaucoma?
paracentral
arcuate
nasal step
what diagnostic tests should you do for glaucoma assessment?
IOP using GAT
-CCT measurement
-gonioscopy
-central threshold testing-VFs
-dilated volk ONH assessment and fundus
