PC - Slitlamp Biomicroscopy 3 (Gonioscopy) - Week 4

Question 1

What grades of Van Herrick should be examined with gonioscopy?

Answer 1

Grades I and II.

Grade I is a must.

Question 2

What Van Herrick ratio is an indication for gonioscopy?

Answer 2

<0.3

Question 3

What iris shadow is an indication for gonioscopy?

Answer 3

> 0.5

Question 4

What 5 pathologies are an indication for gonioscopy (12)?

Answer 4

• Iris neovascularisation
• Retinal ischaemia
• Iris anomalies (lumps, transillumination, bowing, distorted pupil)
• Uveitis
• Trauma (iridodialysis, angle recession)

Question 5

Name the structures seen in gonioscopy in order (6).

Answer 5

Iris
Ciliary body
Scleral spur
Trabecular meshwork
Schwalbe's line
Cornea

Question 6

How do ciliary bodies appear in gonioscopy?

Answer 6

Colour varies, light/dark brown, grey, or mottled band

Question 7

How does the scleral spur appear in gonioscopy?

Answer 7

White band

Question 8

How does the posterior trabecular meshwork appear in gonioscopy?

Answer 8

Pigmented

Question 9

How does the anterior trabecular meshwork appear in gonioscopy?

Answer 9

Pale

Question 10

How does Schwalbe’s line appear in gonioscopy (3)?

Answer 10

Thin grey or pearly white or pigmented line.

Question 11

Name 5 advantages of indirect gonio lens design.

Answer 11

• Can do indentation gonioscopy
• Evaluation of angle in sitting position
• High magnification by SL possible
• Laser treatment of angle
• Fundus and gonio view with the same lens

Question 12

Name 3 disadvantages of indirect gonio lens design.

Answer 12

• Unintentional corneal indentation can open appositional occluded angle
• Angle appears shallower than with a koeppe lens
• Needs viscous coupling fluid, can reduce cornea clarity

Question 13

Name 6 advantages of 4-mirror gonio lenses.

Answer 13

• No viscous medium needed, some say TF is adequate
• Static and dynamic gonio
• Optional flange
• Views 4 quadrants
• Easy removal
• Superior patient comfort

Question 14

Name 4 disadvantages of 4-mirror gonio lenses.

Answer 14

• More difficult to master
• Less stability, can be blinked off
• Inferior view compared to 3-mirror
• Handle difficult

Question 15

How does a 3-mirror gonio lens work?

Answer 15

Suction using a coupling fluid between the lens and the eye.

Question 16

Name 3 advantages of using a 3-mirror gonio lens.

Answer 16

• Good for stable and clear images
• Keeps central position
• Versatile, can do retinal examination at the same time as gonioscopy

Question 17

Name 3 disadvantages of using a 3-mirror gonio lens.

Answer 17

• Lens must be rotated to evaluate the full 360 degrees
• Old cushioning agents can be abrasive and toxic to the cornea
• Patient apprehension due to large lens, appears more invasive

Question 18

Describe the patient instructions for gonioscopy (6).

Answer 18

Indicate what the test involves
Why it needs to be performed
Lens will feel a bit cold
Will touch their eyes for a bit
May feel uncomfortable, wont hurt
May feel liquid down their cheek, is normal

Question 19

Describe 4 ways a gonio lens can be cleaned.

Answer 19

• Lukewarm water with a disinfectant/chlorhexidine
• Some use alcohol swabs
• 1:10 bleach for 25 mins
• Hydrogen peroxide, 3% for 10 mins
• Dry with lint-free cloth

Question 20

Describe the procedure for gonioscopy (5).

Answer 20

Apply coupling medium to the concave surface.
Instil anaesthetic to the patient's eye
-One drop initially, add as needed
-Punctal occlusion
-Advise not to rub eyes

Question 21

What are two contraindications to anaesthetic drops?

Answer 21

Allergies

Anaesthetic reaction

Question 22

How should the slit-lamp illumination be set up during gonioscopy?

Answer 22

Coaxial or slightly off-axis if needed

Question 23

What slit-lamp setup is best for gonioscopy (6)?

Answer 23

Mag at 10x, vertical, parallelepiped 2-3mm wide with the beam height encompassing the gonio lens diameter, and low/med intensity to avoid excessive pupil constriction.

Question 24

Describe how a gonio lens is placed onto an eye.

Answer 24

Three ways:
-Patient asked to look up, pull their inferior eyelid down, place the lens on their inferior conjunctiva, and have them look forward.
-Patient asked to look down, pull their superior eyelid up, place the lens on their superior conjunctiva, and have them look forward.
Release the lids only once the lens is straight and contacting the cornea.
-Use two hands to raise/lower the eyelids, then use forefinger and thumb to place the lens directly on the cornea.

Question 25

How should the gonio lens be aligned on the cornea?

Answer 25

The pupil should take up the central mirror.

Question 26

In what order should the mirrors be assessed?

Answer 26

With the widest and most pigmented: | I>T>N>S

Question 27

What should be done when viewing the lateral mirrors?

Answer 27

Beam should be rotated to horizontal

Question 28

Should the gonio lens be rotated?

Answer 28

Yes, once the first four quadrants are assessed, it should be rotated 45 degrees

Question 29

Describe the recording for gonioscopy.

Answer 29

Specify which eye, the drops used, time, amount, and no contraindications. Draw 4 quadrants, and in each write the most anterior structure visible.

Question 30

Describe the Shaffers grading system for gonioscopy.

Answer 30

``` Based on the most anteriorly visible structure: Grade IV - ciliary body Grade III - scleral spur Grade II - trabecular meshwork Grade I - shwalbe's line Grade 0 - cornea ```

Question 31

Troubleshoot the following for gonioscopy: | Air bubbles

Answer 31

Gonio lens isnt flat, tilt the lens towards the bubble | If it large, reinsert the lens

Question 32

Troubleshoot the following for gonioscopy: | Corneal folds

Answer 32

Too much pressure, apply less

Question 33

Troubleshoot the following for gonioscopy: | Blinking

Answer 33

Hold the lens still, or add more anaesthetic drops

Question 34

Troubleshoot the following for gonioscopy: | Reflections

Answer 34

Change the incident beam slightly, width, intensity, height

Question 35

Troubleshoot the following for gonioscopy: | Poor/no view

Answer 35

Check lens centration and illumination arm not blocking the objective

Question 36

Troubleshoot the following for gonioscopy: | No structures visible

Answer 36

Check centration Try corneal wedge Tilt the lens Try indentation

Question 37

List 4 tips when performing gonioscopy.

Answer 37

Carry out binocularly to compare Rest elbow on a box Pushing too hard pushes aqueous to the periphery, angle appears wider Perform gonio in a dark room with a narrow beam

Question 38

Why should gonioscopy be performed in a dark room?

Answer 38

AC is narrowest in the dark due to the peripheral muscles thickening and a more convex iris, and so the risk of angle closure glaucoma is greatest under dim illumination.

Question 39

Name 7 other gonioscopy findings that may be seen.

Answer 39

Synechia: uveitis Pigmentation: pigment dispersion syndrome Pseudofoliative material Blood vessels: neovascularisation Particles Blood: post trauma Inflammatory deposits: keratic precipitates

Question 40

What are iris processes? What age group are they seen highest in? Where to they begin and project to?

Answer 40

They are normal anomalies, seen most in childhood and wither with age. Begin at the iris periphery and bridge the CB and insert into the TM.

Question 41

Where do anbormal iris processes insert into?

Answer 41

Schwalbes line

Question 42

Name 7 contraindications of gonioscopy, and why if applicable.

Answer 42

``` Anaesthetic reaction -self explanatory Lacerated or perforated globe -Pressure will cause aqueous to drain out of the eye Hyphaemia -Will cause a rebleed Pregnancy -Reduced corneal healing Corneal/Conjunctival infection or epithelial basement membrane dystrophy -Corneal epithelium already weak ```

Question 43

What 6 things can an OCT scan give information about?

Answer 43

``` CCT Corneal curvature AC depth AC volume Iris angle Plateau iris ```