Slit Lamp 3 GONIO - Week 4 Flashcards
Name 6 methods for examining anterior chamber
- VH
- Iris Shadow
- Smith’s method
- Spot/cone of light, 60deg, dark room
- Gonioscopy
- OCT
How does OCT examine anterior chamber?
quantify depth, and visualize structures in vivo non-invasively
e.g. iris insertion and configuration
List the indications for performing Gonio:
- narrow angle (VH less than 0.3; iris shadow over 0.5)
- to assess suitability for dilation
- when you suspect glaucoma
- signs of angle-closure glaucoma
- iris neovascularisation, retinal ischaemia
- iris anomalies
- uveitis
- trauma (irididodialysis, angle recession)
What type of iris anomalies serve as an indication to perform gonioscopy?
lumps, transillumination, bowing, distorted pupil etc.
List the anatomical structures visible in gonioscopy from posterior to anterior
- Iris
- ciliary body
- scleral spur
- trabeculae
- schwalbe’s line
- cornea
What anatomical structures are visible in gonioscopy when looking at grade 0 or 1 angle?
Iris and cornea only. Rest are hidden
What does the scleral spur look like in gonioscopy?
White band
What does ciliary body look like in gonioscopy?
Colour varies - light or dark brow, grey or mottle band
What does posterior TM look like in gonioscopy?
pigmented
What does anterior TM look like in gonioscopy?
pale
What does schwalbe’s line look like in gonioscopy?
Thin grey, pearly white, or pigmented line
When using gonioscope, what image do we see when looking into the superior mirror? inferior mirror? nasal? temporal?
superior mirror: lets us look at inferior angle
inferior mirror: superior angle
nasal mirror: temporal angle
temporal mirror: nasal angle
What images appear in a 3-mirror gonio? How does this differ to a 4-mirror gonio?
3 mirror: one mirror = see anterior chamber, other 2 mirrors = look at various parts of retina
4 mirror: all 4 mirrors are same angle therefore all look at anterior chamber
List advantages of 4 mirror gonio:
- don’t require viscous medium
- some suggest tear film adequate?
- can be static or dynamic gonio
- optional flange
- view 4 quadrants (minimal rotation required)
- easy removal (no suction)
- superior px comfort
List disadvantages of 4-mirror gonio
- more difficult to master?
- stability (can be blinked off)
- view inferior to 3-mirror?
- difficult to handle?
List advantages of 3-mirror gonio
- good for producing a stable, clear image
- keeps central position
- versatile
List disadvantages of 3-mirror gonio
- lens must be rotated to evaluate all 360deg of angle
- beware of cushioning agent used (old ones can be toxic(
- px apprehension because of large looking lens (appears more invasive)
List instructions for gonioscopy
- indicate what test involves
- why it needs to be performed
- “lens will feel a bit cold”
Where do you instill the anaesthetic before gonioscopy?
conjunctival fornix
Name 2 contraindications for anaesthetic drops
- allergies
- anaesthetic reaction
Why should you advise a px to not rub eye after anaesthetic?
because they won’t feel it and they may rub too hard and cause damage
What slit lamp settings should you have during gonioscopy?
Use a vertical PPD 2-3mm wide with magnification at 6-16x and low-medium intensity
Why use low-medium intensity in slat lamp during gonio?
To avoid excessive pupil constriction
Should you provide a fixation target during gonio?
yes
How should you hold the gonio lens?
between thumb and 2nd finger
How do you focus the view in gonioscopy?
by moving the slit lamp in and out
What does the centre lens of the gonioscope let us see?
the fundus
How do you record gonioscopy?
Draw an X with each quadrant representing the following angles: superior, inferior, nasal, temporal angles.
In each quadrant/angle, write the initials of the deepest structure you can see
How does pigmentation affect the optom’s ability to make out structures in gonioscopy?
Less pigmented = harder
more pigmented = easier
What if air bubble between cornea and gonio?
Not pressing with gonio enough. Tilt the lens towards the bubble (if bubble is large: reinsert the lens)
What if you see corneal folds in gonio?
Pressing too hard. Apply less pressure
What if patient is blinking in gonio?
- hold the lids
- maybe check if anaesthetic still there/working
What if you are getting reflections in gonio?
change incident beam angle slightly, width, intensity, height
What if poor view in gonio?
- check lens centration and illumination arm is not blocking the objective
What if no structures visible in gonio?
- check centration
- try corneal wedge
- OS - is beam deflected at iris-cornea interface
- try tilting the lens
- try identation
What if schwalbe’s line nor visible in gonio?
try using corneal wedge technique: reduce illumination to a narrow slit, increase intensity and off-set illmination
List 8 contraindications for Gonioscopy
- Anaesthetic Reaction
- Lacerated or perforated globe (pressure will cause aqueous to drain out of the eye)
- Hyphaema (will cause a rebleed)
- Pregnancy (reduced corneal healing)
- Corneal/Conjunctival infection or epithelial basement membrane dystrophy
- Corneal epithelium already weak
- OCT
