Glaucoma 3 - Optic discs in Glaucoma Flashcards
Glaucoma - Definition
Refers to a group of disorders in which there is eventual development of an optic neuropathy with characteristic changes at the optic nerve head. These changes are likely to lead to a depression of visual function and eventual loss of visual field.
Raised intra-ocular pressure often appears to be a significant factor in its development.
What is structure vs function in glaucoma?
• Changes in optic disc and retinal nerve fibre layer usually precede onset of VF defects with standard white on white perimetry
• Even with advanced changes in optic nerve morphology visual field change may or may not be present
Whats important about finding out earliest changes of Glaucoma?
• The earliest changes in glaucoma are seen at the retinal nerve fibre layer and at the optic disc with characteristic changes
Optic Disc Assessment of glaucoma:
• ISNT rule - normal disc rim is thickest inferiorly then superiorly and then nasally
• Notice rim colour - pallor should correspond or be slightly less than cup
• Tilted discs are difficult to interpret (look carefully for glaucomatous features and correlate visual field.(ST VF defects not central esp myop)
Optic disc assessment : Size of optic disc?
• Note size of optic disc -Disc size can be measured with the normal disc being 1.5 to 2.0 mm in vertical diameter or assessed in relation to the calibre of the blood vessels which are fairly constant in size
• small discs in hypermetropes apparently normal CD ratio may be misleading
• Large discs have large cups - look at NR rim
10 Signs to look out for in Glaucomatous disc:
- CD ratio
- Blood vessel position
- Rim thickness
- Pallor
- Peri-papillary atrophy
- APON acquired pit
- Haemorrhage
- Nerve fibre layer defects
- Notch
- Laminar dots
Optic disc assessment questions:
•Evidence of glaucomatous nerve damage? i.e. apon
• Difference in the appearance between two optic nerves?
• Reason other than glaucoma for difference in two optic nerves?
• Appearance of the optic nerve indicate any acquired change?
- Progressive?
Spaeth , referring to glaucoma, states that:
•Change from former state
•No “first sign” or pattern of glaucomatous disc - commonest patterns are:
1) Concentric enlargement
2) Focal extension with thinning of NR rim
(Inferiorly/Superiorly)
• Disc Damage Likelihood Scale (DDLS)
Signs of change if glaucoma:
•Shift in position of blood vessels
• Thinning of NR rim
• Developing notch
• Hemorrhage crossing disc rim
• Developing focal pallor
• Change in peripapillary atrophy
Disc damage likelihood scale: DDLS (Spaeth)
• Based on:
1. Size of Disc
2. Thinning of NR rim (inverse of CD ratio) in thinnest areas and degrees of involvement
3. incorporated in new Glaucoma SIGN
Guidelines for referrals
DDLS stage 4 or above - requires referral
Correction factors when measuring optic disc size:!
• Volk:
60D-0.88
66D-1.0
78D-1.2
90D-1.33
• Nikon
60D-1.03
90D-1.63
Concentric enlargement is?
Enlargement of the cup/increase in cup to disc ratio
Temporal Unfolding?
• Variant of Concentric cupping, where theres principle loss of the neuroretinal rim on the temporal side
Vertical extension sign?
•Starts as small centrap cup
•Cup enlarges superior or inferiorly
Notching as a sign?
•Similar to Vertical extension but:
- High focal loss of tissue in region forming “notch”
Acquired pit of optic nerve (apon)
•Like notch
•Develops inferior temporal
- Blood vessels “disappear into pit” and then pop out again
Pits can be:
•Acquired
- Superior/inferior
- are smaller
•Congenital
- central/temporal
- Tend to be larger
Nasal cupping is:
• Tend to get loss of tissue on nasal side
- Opposite to that of temporal unfolding but on nasal side
Senile sclerosis
•Older patients (90+)
• Not obvious cupping but gradual palor/increase in optic disc
- Generalised gradual process
Generalised pallor is:
• A pale look of the optic disc/periphery
Differential Diagnoses for Disc abnormalities:
Excavated disc abnormalities
• Optic N coloboma
• Congenital optic N pit
•Morning glory synd
• tilted disc syndrome
• peri-papillary staphyloma
Differential diagnosis for Pale Optic Discs:
• AION
• CRAO
• Heredofamilial optic atrophies
• Other optic neuropathies (inflammatory, infectious, toxic, nutritional, compressive)
What is optical coherence tomography and Stereophotography
•Optical Coherence tomography
- uses low-coherence interferometry to assess disc and peripapillary RNFL thickness by the difference in temporal delay of back-scattered light from the RNFL and a reference beam
• Stereophotography
- i.e.Topcon imaging systems Kowa
provides a high quality (3D) permanent record of disc appearance at presentation and at any desired subsequent follow-up for comparison.
(use with stereo-viewer)
