Forms of Gonio

Question 1

Forms of gonioscopy

Answer 1

direct and indirect

Question 2

direct gonio

Answer 2

use direct view of angle structure

anterior curve of goniolens is such that critical angle is not reached

light rays are refracted at contact lens-air interface

Question 3

indirect gonio

Answer 3

use reflection of light to view the structure

light rays are reflected by mirror in gonioprism

Question 4

Goniolenses (direct gonioscopy)

Answer 4

1. koeppe: prototype diagnostic goniolens
2. richardson-schaffer: small koeppe lens for infants
3. layden: for premature infant gonioscopy
4. barkan: prototype surgical goniolens
5. thorpe: surgical and diagnostic for OR
6. swan-jacob: surgical goniolens for children

Question 5

koeppe lens

Answer 5

50 D lens

convex cl made of glass or plastic

dia is 16.5 - 22.5 mm

curvature approximately same as cornea

convexity and index of refraction of lens such that refracts light from anterior chamber toward observer

chamber angle is illuminated with barkan handheld illuminator

angle simultaneously examined through hand held binocular goniomicroscope

Question 6

koeppe lens technique

Answer 6

patient reclined

anesthetic dropped and gonio lens positioned on cornea

space b/n lens filed by capillary attraction with saline or methylcellulose bridge

Question 7

koeppe lens image

Answer 7

upright, virtual, magnified

1. 5 x magnified by curvature of lens
   microscope: 1.6 x objective lenses, 10 x oculars (or 16x)

total of 15-24 x

Question 8

koeppe lens advantages

Answer 8

obtain most natural appearance of angle structures

360 degree view of the angle

min. patient cooperation needed

done at bedside

gonioscope moved freely to easily observe angle from various positions

execellent stereo in all quadrants

easy transilllumination

iridonesis more apparent

view both eyes at the same time

Question 9

koeppe lens diasadvantages

Answer 9

more equipment

no slit beam to observe angle

assistant needed to manipulate lens and illumination system

inconvenient

need space to move

more difficult

anatomical interference in sup. quadrant

image not as clear as indirect

Question 10

indirect gonioscopy

Answer 10

indirect view of area of regard

advantage of patient’s position and illumination and mag. offered with microscope

Question 11

gonioprisms (indirect gonioscopy)

Answer 11

1. goldmann 1-mirror: mirror inclined at 62 for gonioscopy
2. goldmann 3-mirror: 3 mirrors; coated front surface avail.
3. zeiss 4-mirror: 4 mirrors; 64 incline; requires holder
4. posner 4 mirror: 4 mirrors; 64 incline; attached handle
5. sussman 4-mirror: handheld zeiss-type 4 mirror
6. goldmann 4 mirror: 4 mirrors; with or without flage; large contact area not well suited for indentation gonioscopy
7. thorpe 4 mirror: 4 mirrors; equires fl bridge
8. ritch trabeculopl: 4 mirrors; 2-59 and 2-62 convex lens

Question 12

indirect gonio image

Answer 12

virtual, unmagnified, reversed

Question 13

indirect gonio advantages

Answer 13

pt can sit up, mag adjusted with slit lamp, illumination varied with slit lamp, may follow contour of slit beam (iris contour, corneal wedge, elevation/depression)

easy, little equipment, not much space needed, stereoscopic view, 3mirror goldmann may be used as retinal lens

Question 14

indirect gonio disadvantages

Answer 14

cooperation of patient

size of mirror limits angle being examined

bionocularity difficult laterally

lens/hand support and repositioning

methylcellulose bridge may be needed

Question 15

goldmann lens

Answer 15

cone shapped

light detachable ring (offers protection against breakage)

antireflection coating for use with laser trabeculoplasty

Question 16

goldmann 3 mirror

Answer 16

4 thumb nail - gonioscopy, retinal examination

3 mirrors spaced at 120

mirrors 2,3 and 4 and lens 1 can be used to evaluate retina

Question 17

goldmann 3 mirror: ACA and retinal/vitreal exam

Answer 17

uses thumb nail mirror

AKA anterior chamber angle

may also be used to view peripheral retinal to ora serrata and vitreous base

Question 18

goldmann lens - exam technique

Answer 18

pre-procedure eval: assessment for contraindication, VH assessment, IOP

disinfect lens

2-4 coupling gel drops on lens

pt’s ocular surface (anesthetize patient)

pos. pt properly in biomicroscope

adjust microscope to 2-3 mm slit; reduce height of slit

set mag to 10x - 16x

pos. microscope and slit lamp perpendicular to front of plane of lens

Question 19

4 mirror lens

Answer 19

small posterior surface type

polished truncated glass pyramid, surfaced in silver

mirrored walls inclined at 64 degrees

posterior curvature of lens similar to cornea so tears can ac t as fluid bridge

Question 20

4 mirror lens type

Answer 20

1) sussman - handheld zeiss type gonioprism
2) posner - zeiss-like design, attached handle
3) zeiss - 9 mm corneal segment, radius 7.72 mm, 64 degree tilt requires holder (unger)

Question 21

4 mirror lens technique

Answer 21

properly disinfect lens

instill anesthetic

position patient properly in biomicroscope

adjust microscope to 2-3 mm slit

set mag to 10 or 16x

position microscope and slit lamp perpendicular to front plane of lens

indentation or compression gonio:
cornea is indented, causing inc. IOP which transmitted to ant. chamber, exerts force on chamber walls, can distinguish b/n appositional closure and synchial closure, with very high IOP indentation difficult and not effective

Question 22

4 mirror advantages

Answer 22

360 degress with minimal rotation

useful with children and small apertures

convenient

comfortable

rapid

no goniogel required

used for indentation or compression gonioscopy

Question 23

4 mirror lens disadvantage

Answer 23

aritifically widen anterior angle in routine gonioscopy

pressure may result in descemet’s folds

bubbles are frequently a problem

stereo difficult laterally

lack of clarity