1.05 Anterior angle assessment

Question 1

what is the limbus

Answer 1

• Transition from cornea to sclera/ conjunctiva
• It’s external part involves bulbar conjunctiva and internal involves anterior angle

Question 2

layers of the limbus

Answer 2

1. ciliary band
2. scleral spur
3. trabecular meshwork
4. Schwalbe’s line
5. angle recess

Question 3

what is aqueous humour

Answer 3

1. produced in the ciliary body in the posterior chamber
2. flows to anterior chamber via pupil
3. circulates in anterior chamber
4. drains away via anterior angle

Question 4

where does aqueous drainage mainly take place

Answer 4

Mainly through the trabecular meshwork into the canal of Schlemm

Question 5

what is trabecular meshwork made of

Answer 5

interlaced cords of tissue extending from the apex of the angle to the margin of the cornea

Question 6

anterior angle

Answer 6

The angle between the anterior iris and posterior cornea is the anterior angle.
Wider angle allows aqueous humour to drain freely so interocular pressure reduces
a narrow or closed angle restricts aqueous drainage so interocular pressure increases.

Question 7

what is the clinical grading scale for anterior angle

Answer 7

Grade 0: angle closed
Grade 1: about 10 degrees
Grade 2: about 20 degrees
Grade 3-4: 20-45 degrees

Question 8

what happens of there is a blocked angle

Answer 8

stops drainage of aqueous
rise in pressure
painful red eyes
loss of vision
primary closed angle glaucoma

Question 9

what techniques are used to assess the angle

Answer 9

• shadow test
• van herick’s
• smiths
• Gonioscopy

Question 10

why can we not look at the anterior angle directly

Answer 10

due to total internal reflection and shape of the cornea

Question 11

what is the shadow test

Answer 11

use a pen torch
low room illumination
bring light forward from temporal side
should light all of the iris
bulging iris causes shadow on nasal side

so basically if theres a shadow on the nasal side and not all of the iris is illuminated then closed angle

Question 12

what is van Herick’s

Answer 12

corneal optic section
shining through the cornea and through anterior chamber to the iris
high illumination, medium magnification and viewing system at 60 degrees to illumination

Question 13

grading system for van hericks

Answer 13

garde 0 - closed
grade 1 - less than 1/4
grade 2 - 1/4 to 1/2
grade 3 - 1/2 to 1
grade 4 - 1

Question 14

what is smiths method

Answer 14

slit lamp beam should be horizontal
1-2mm wide beam
use high illumination
medium magnification

Two images are created:
one from cornea
one from the anterior lens/iris

we need to increase the slit height until the images touch (record slit height)

slit height x 1.4 = AC depth

Question 15

gonioscopy

Answer 15

goniscope lens touches cornea
eliminates refractive surface of the cornea
can look into angle with slit lamp
only way to truly assess angle