Glaucoma introduction & POAG

Question 1

What is glaucoma?

Answer 1

A group of eye diseases that damage the optic nerve

Question 2

Which cells are affected in glaucoma?

Answer 2

Retinal ganglion cells (RGCs)

Question 3

What do RGCs do?

Answer 3

When light enters the eye, RGCs will transmit the info to the brain via their axons which are long fibres that make up the optic nerve. They allow you to see as they send the image to your brain

Question 4

Why is glaucoma damage irreversible?

Answer 4

RGCs are part of the body’s central nervous system, which does not regenerate once damaged.

Question 5

What are the types of glaucoma?

Answer 5

Primary:

1. POAG
2. PACG
3. Congenital

Secondary:

1.

Question 6

What is the most common type of glaucoma?

Answer 6

Primary Open Angle Glaucoma (POAG)

Question 7

What is Primary glaucoma?

Answer 7

Occurs without any preceding ocular or systemic disease

Question 8

What is in the ‘open angle describing POAG and how is it measured?

Answer 8

The angle between the cornea and iris measured using van Herrick

Question 9

What happens is open angle glaucoma?

Answer 9

The aqueous drainage is normal from the posterior chamber, to the pupil into the anterior chamber but the problem is with the trabecular meshwork itself.

Question 10

What are the demographic risk factors of POAG?

Answer 10

Over 40, afro-caribbean, family history (they have thinner corneas and more vasculopathy)

Question 11

What are the ocular risk factors of POAG?

Answer 11

High IOP, myopia, thin cornea

Question 12

What are the sytemic risk factors of POAG?

Answer 12

Diabetes, migraine, raynaud’s

Question 13

How does the cornea cause a risk for glaucoma?

Answer 13

Thin cornea is linked to thin lamina cribrosa which is more susceptible to damage hence increasing risk of glaucoma

Question 14

How do the migraines cause a risk for glaucoma?

Answer 14

A link between vasculopathy (disease affecting blood vessels) so those with migraines, raynaud’s and low blood pressure at increased risk. Lack of ocular perfusion around the optic nerve so the blood supply is weaker putting it at risk of damage

Question 15

What are symptoms of POAG?

Answer 15

Asymptomatic until end stages where they get peripheral field loss

Question 16

What tests are important to detect glaucoma?

Answer 16

DAFT discs,angle,fields,tonometry

Question 17

How do you measure IOP?

Answer 17

NCT or GAT

Question 18

Why is CCT (Central corneal thickness CCT) important?

Answer 18

A thin CCT will result in an underestimation of IOP, whilst a thick CCT will cause an overestimation of IOP

Question 19

What is normal CCT?

Answer 19

520 Microns

Question 20

What is normal IOP?

Answer 20

8-23mmHg Does high IOP mean glaucoma? No

Question 21

What is IOP affected by?

Answer 21

-CCT -Diurnal variation

Question 22

What is dinural variation?

Answer 22

IOP higher in the morning

Question 23

When do you refer for suspect POAG based on high IOP?

Answer 23

If 24mm Hg or more then refer only if: you have measured IOP using GAT and done on a different occasion

Question 24

What are the signs of a glaucomatous optic nerve?

Answer 24

Large CD ratio >0.6 CD asymmetry >0.2 NRR thinning (Superior and inferior, ISNT not obeyed) Lamina cribrosa pores visible Notching of NRR Pallor Baring of blood vessels Fly over vessels Bayonetting and nasalization of vessels Peripapillary atrophy (PPA) Optic disc hemorrhages RNFL changes

Question 25

Why race has larger optic discs?

Answer 25

Afro-Caribbean population

Question 26

If the disc is larger then what else is larger?

Answer 26

Larger disc= larger cup

Question 27

How many nerve fibres pass through the optic nerve?

Answer 27

1.2 million

Question 28

What is asymmetry a sign of glaucoma?

Answer 28

Glaucoma is typically an asymmetric disease Early optic nerve head changes may produce a right-left eye asymmetry.

Question 29

What is the Neuroretinal rim?

Answer 29

Layer of neural tissue between edge of disc and edge of cup.

Question 30

How does the NRR appear in a healthy eye?

Answer 30

ISNT obeyed, thickest to thinnest

Question 31

What thins first in glaucoma?

Answer 31

inferior or superior NRR thinning

Question 32

What is the lamina cribrosa?

Answer 32

A connective tissue meshwork located deep in the optic nerve head, contains pores through which all retinal ganglion cell axons pass on their way to the brain

Question 33

Why is LC pores being visible a sign of glaucoma?

Answer 33

Increased visibility associated with larger CD ratio

Question 34

What is notching?

Answer 34

Notching of the NRR represents a focal loss of the nerve fibres and is especially of concern if the notch is located infra-temporal or supratemporal.

Question 35

What type of NRR is more common in open angle glaucoma?

Answer 35

Diffuse loss more common that localised loss so notching is less common)

Question 36

What does pallor mean?

Answer 36

As nerve fibres die so the disc becomes paler

Question 37

What is baring of blood vessels?

Answer 37

Baring of the circumlinear vessel occurs when areas of pallor develop between these small branches of the central retinal vessels and the cup margin

Question 38

What is bayoneting?

Answer 38

In areas where the rim has been lost, retinal vessels can sharply change direction as they pass under the overhanging edge of the cup. This is known as bayonetting

Question 39

What is nasalisation?

Answer 39

As glaucomatous cupping occurs, the blood vessels appear to shift nasally due to loss of the neuroretinal rim.

Question 40

What are fly over vessels?

Answer 40

Fly-over vessels are seen when rim tissue underlying the retinal vessels that cross the disc margin is lost, which can give the appearance of vessels floating above areas of deeper cupping.

Question 41

What is PPA?

Answer 41

Atrophy surrounding the disc. A and b zone

Question 42

What is a zone and b zone PPA?

Answer 42

The a-zone atrophy is more common in normal eyes and is located on the outer surface of zone beta if present. The inner ß-zone beta represents loss of retinal pigment epithelium and is uncommon in non-glaucomatous eyes

Question 43

What are Optic disc hemorrhages shape and location?

Answer 43

Splinter- or flame-shaped and located in the pre-laminar area of the optic disc in the superficial retinal nerve fibre layer. They can also be found in deeper parts of the disc margin and in the disc cup. Haemorrhages associated with glaucoma are often observed in the inferotemporal sector of the optic disc Image shows splinter

Question 44

What are other conditions can cause a disc haemorrhage?

Answer 44

Posterior vitreous detachment, optic disc drusen, non-glaucomatous optic neuropathies, and vascular occlusive diseases of the retina. Systemic disorders: diabetes, systemic hypertension, systemic lupus erythomatosis and leukaemia. They can also be associated with use of anti-coagulants.

Question 45

What is the RNFL?

Answer 45

The retinal nerve fibre layer (RNFL) describes the radial expansion of the optic nerve fibres from their point of entrance at the optic disc. These opaque striations form arcuate bundles of nerve fibres where changes can occur in glaucoma.

Question 46

How can you examine RNFL defects?

Answer 46

OCT= Red-free (green) light to enhance contrast, examining the peripapillary region for slit shaped, wedge shaped or diffuse defects.

Question 47

What VF defect do you see in glaucoma?

Answer 47

Nerve fibre bundle defects (paracentral, arcuate, nasal step) and overall depressions, baring of the blind spot and enlargement of the blind spot. Defects tend to follow the distribution of nerve fibres, be asymmetric between eyes and hemispheres and can be variable and intermittent.

Question 48

What do VF defect do you see in end stage glaucoma?

Answer 48

Tunnel vision

Question 49

What is the GHT?

Answer 49

The glaucoma hemifield test compares the number and severity of the pattern deviation probability symbols between the top and bottom halves of the field and has been shown to be sensitive to early glaucoma visual field loss. The mean deviation, pattern standard deviation and visual field index provide summary measures that may be useful metrics in the assessment of progression.