Forms of Gonio Flashcards
Forms of gonioscopy
direct and indirect
direct gonio
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
indirect gonio
use reflection of light to view the structure
light rays are reflected by mirror in gonioprism
Goniolenses (direct gonioscopy)
- koeppe: prototype diagnostic goniolens
- richardson-schaffer: small koeppe lens for infants
- layden: for premature infant gonioscopy
- barkan: prototype surgical goniolens
- thorpe: surgical and diagnostic for OR
- swan-jacob: surgical goniolens for children
koeppe lens
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
koeppe lens technique
patient reclined
anesthetic dropped and gonio lens positioned on cornea
space b/n lens filed by capillary attraction with saline or methylcellulose bridge
koeppe lens image
upright, virtual, magnified
- 5 x magnified by curvature of lens
microscope: 1.6 x objective lenses, 10 x oculars (or 16x)
total of 15-24 x
koeppe lens advantages
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
koeppe lens diasadvantages
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
indirect gonioscopy
indirect view of area of regard
advantage of patient’s position and illumination and mag. offered with microscope
gonioprisms (indirect gonioscopy)
- goldmann 1-mirror: mirror inclined at 62 for gonioscopy
- goldmann 3-mirror: 3 mirrors; coated front surface avail.
- zeiss 4-mirror: 4 mirrors; 64 incline; requires holder
- posner 4 mirror: 4 mirrors; 64 incline; attached handle
- sussman 4-mirror: handheld zeiss-type 4 mirror
- goldmann 4 mirror: 4 mirrors; with or without flage; large contact area not well suited for indentation gonioscopy
- thorpe 4 mirror: 4 mirrors; equires fl bridge
- ritch trabeculopl: 4 mirrors; 2-59 and 2-62 convex lens
indirect gonio image
virtual, unmagnified, reversed
indirect gonio advantages
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
indirect gonio disadvantages
cooperation of patient
size of mirror limits angle being examined
bionocularity difficult laterally
lens/hand support and repositioning
methylcellulose bridge may be needed
goldmann lens
cone shapped
light detachable ring (offers protection against breakage)
antireflection coating for use with laser trabeculoplasty
goldmann 3 mirror
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
goldmann 3 mirror: ACA and retinal/vitreal exam
uses thumb nail mirror
AKA anterior chamber angle
may also be used to view peripheral retinal to ora serrata and vitreous base
goldmann lens - exam technique
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
4 mirror lens
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
4 mirror lens type
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)
4 mirror lens technique
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
4 mirror advantages
360 degress with minimal rotation
useful with children and small apertures
convenient
comfortable
rapid
no goniogel required
used for indentation or compression gonioscopy
4 mirror lens disadvantage
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
