Glaucoma 2

Question 1

True or False- Primary closed angle glaucoma is responsible for 20% of all blindness caused by glaucoma

Answer 1

False- Primary closed angle glaucoma is responsible for approx 50% of all blindness caused glaucoma.

Question 2

Describe the mechanism behind Primary Closed Angle Glaucoma.

Answer 2

The major mechanism acting in acute primary angle closure is pupil block

Failure of physiological aqueous flow through the pupil leads to a pressure differential between the anterior and posterior chambers, with resultant anterior bowing of the iris.

Question 3

What are the risk factors for Primary Angle Closure Glaucoma (PACG)?

Answer 3

–Age: (>50 yrs)

–Gender: Females > Men

–Race: Asian Chinese > Indian > African > Caucasian

–Family history

–Hypermetropia

Question 4

How can you assess the anterior chambre angle (not depth)?

Answer 4

–Van Herick assessment

–Anterior Segment OCT

–Gonioscopy

Question 5

What is the gold standard method for assesing the anterior chamber angle?

Answer 5

Gonioscopy

Question 6

What is the treatment for Primary Angle Closure Glaucoma?

Answer 6

• Laser peripheral iridotomy (this is the main one)- Nd/Yag laser creates a small hole in peripheral iris. Allows the aqueous humour to flow through and the iris tissue moves backward
• Peripheral iridoplasty – Argon laser (lower energy) to widen the anterior chamber angle by contraction of the peripheral iris away from the angle recess
• Lens extraction/cataract surgery - because the lens can become fatter overtime causing the anterior chamber depth to become smaller

Question 7

What are the symptoms of an Acute Primary Angle closure Glaucoma attack?

Answer 7

Symptoms - rapid onset (hours) that may include:

• Haloes round lights
• Red eye
• Marked ocular pain
• Blurred vision
• Nausea, vomiting and feeling unwell

Question 8

What are the signs of an Acute Primary Angle Closure Glaucoma attack?

Answer 8

• Decrease in VA – usually 6/60 to HM
• Sudden elevation in IOP >40 mm Hg or more
• Red eye – conjunctival hyperaemia with circumcorneal injection
• Unreactive semi-dilated pupil - vertically oval in shape
• Corneal oedema
• Shallow anterior chamber – check for posterior synechiae and pupil block

Question 9

What is the optometric management of an Acute Primary Angle Closure Glaucoma attack?

Answer 9

• An acute attack is an ocular emergency
• Call an ambulance/arrange transport
• Send patient straight to A+E

Question 10

How can we objectively measure the Anterior chamber angle?

Answer 10

Question 11

Why is Gonioscopy the gold standard for conducting an angle assessment?

Answer 11

It overcomes total internal reflection

Question 12

Which two lenses can we use to conduct gonioscopy?

And what conditions are needed for each one?

How many mirrors does each lens contain?

Which lens provides a more magnified view?

Answer 12

A corneal lens can be used or a scleral lens can be used.

A corneal lens does not require a coupling fluid. A scleral lens does require a coupling fluid e.g. viscotears.

A corneal lens contains 4 mirrors (typically). A scleral lens typically conatins 1 or 2 mirros.

A scleral lens provides a more magnified view.

Question 13

What is the technique for carrying out gonioscopy?

Answer 13

–Advise patient on the procedure

–Carry it own in a darkened room

–Anaesthetise the cornea

–Place lens onto cornea

–Patient looks straight ahead

–High magnification, a short wide beam

–Move the joystick to illuminate each mirror and view the angle (indirectly)

–Care should be taken to avoid light falling on the pupil during the procedure as it would falsely cause angle to open

Question 14

What are the landmarks to look for in gonioscopy?

Answer 14

Question 15

What is Schwalbe’s line - i.e. what does it represent?

Answer 15

Anatomically it demarcates the peripheral termination of Descemet membrane and the anterior limit of the trabeculum.

Question 16

How may Schwalbe’s line appear in young pxs?

How may Schwalbe’s line appear in older pxs?

Answer 16

It may be barely discernible, particularly in younger patients.

In contrast, there may be pigment deposits on or anterior to Schwalbe line (Sampaolesi line) that may make interpretation of the angle structures difficult.

Question 17

How may you identify Schwalbe’s line in a young px?

Answer 17

The corneal wedge is useful in locating an inconspicuous Schwalbe line. Using a narrow slit beam, two distinct linear corneal reflections can be identified, one on the inner and one on the outer corneal surface; the outer reflection will arc round across the corneoscleral interface – due to the sclera being opaque – to meet the inner reflection at the apex of the corneal wedge which coincides with the Schwalbe line.

[The two faint white lines, which are highlighted by the red arrows where it says cornea on the diagram]

Question 18

How does the appearance of the trabeculum change overtime?

[Trabeculum is labelled as TB on the diagram and further split into the nonpigmented trabeculum and the pigmented trabeculum]

Answer 18

The posterior, pigmented functional part has a greyish-blue translucent appearance in the young. Trabecular pigmentation is rare prior to puberty, but in older eyes pigmentation is heavily present.

Question 19

What does patchy trabeculum pigmentation in dangerously narrow angle raise suspicion of?

Answer 19

Patchy trabecular pigmentation in a suspiciously narrow angle raises the possibility of intermittent iris contact.

Question 20

Where can the Schlemm canal be found?

Why may blood be found in the Schlemm canal?

Answer 20

Schlemm canal may be identified in the non-pigmented angle as a slightly darker line deep to the posterior trabeculum. Blood can sometimes be seen in the canal either physiologically (sometimes due to excessive pressure on the episcleral veins with a goniolens), or in the presence of low intraocular or raised episcleral venous pressure.

Question 21

Where can the ciliary body be found in gonioscopy?

What does it’s width depend on?

Answer 21

The ciliary body stands out just below the scleral spur as a pink to dull-brown to slate-grey band. Its width depends on the position of iris insertion and it tends to be narrower in hypermetropic eyes and wider in myopic eyes.

Question 22

What are iris processes and in what percentage of px’s are they seen in via gonioscopy?

Answer 22

Iris processes are small extensions of the anterior surface of the iris which insert at the level of the scleral spur and cover the ciliary body to a varying extent. They are present in about one-third of normal eyes and are most prominent during childhood and in brown eyes

Question 23

What grading system do we use for gonioscopy and how do we use it?

Answer 23

The Schaffer grading system - it grades based on what structures you can see (which are a direct indication of the openness of the angle).

Using this grading system we grade each of the four quadrants seen with the gonio lens!!!!

Question 24

Describe the Schaffer grading system, including what is required for each grade and what the clinical interpreation of each grade is.

Answer 24

Question 25

What is the Schaffer grading angle?

Answer 25

Shaffer angle - angle between the anterior surface of the iris and the inner surface of the trabeculum

Question 26

If the Posterior trabecular meshwork is not visible for at least two quadrants (i.e. at least two quadrants with Schaffer grade 1 or 0) what do we term the eye?

Answer 26

An occludable eye. i.e there is a risk of angle closure

Question 27

What is Peripheral Anterior Synechiae (PAS) and how may this affect IOP?

Answer 27

Peripheral Anterior Synechiae are Adhesions between the peripheral iris and cornea.

They cause an obstruction of aquous outflow.

Question 28

How is an Acute attack of angle closure managed (before treatment)?

Answer 28

• Patient lies supine (i.e. lies down) (to try to break adhesion between the iris and the lens)
• Medical therapy (to reduce pressure):
• Acetazolamide is given intra-venously and/or orally (aqueous suppressants to reduce pressure)
• Mannitol (vitreous suppressant to reduce pressure)
• IOP lowering drops and steroid drops (to reduce inflammation) to the affected eye
• Pilocarpine drops instilled (pupil constriction to avoid adhesions)

Question 29

What is the treatment for an Acute Angle Closure attack?

Answer 29