Competency 3.1.2 Flashcards
Low Mag SL Techniques
- Diffuse illumination
- Optical section
- Parallelpiped
- Sclerotic scatter
- Tangential viewing
- Van Herick’s
Medium Mag SL Techniques
- Optical section
- Parallelpiped
- Conical beam
- Retro-illumination
- Specular Reflection
High Mag SL Techniques
- Optical section
- Parallelpiped
- Retroillumination
- Specular reflection
Definitions of Coupled and Decoupled Systems
- Coupled is when the illumination and observation systems both swing around the same pivot point.
- De-coupled refers to when the illumination system is moved to the side and therefore no longer meets the optimal focus of the observation system.
Indirect Illumination SL Techniques
- Retro-illumination
- Sclerotic scatter
Optical Section SL Technique
- Very thin beam
- Images a section of cornea or lens
- Must be at 90 degrees to the corneal surface
- Variable magnification
Parallelpiped SL Technique
- Slightly broader beam than optical section (avg width 1mm)
- Variable angle of illumination system
- Can be used to assess how flat conjunctiva is and can be used to visualise SPK
Conical Beam SL Technique
- Circular beam and medium magnification
- Illumination system positioned temporally 45 to 60 degrees
- Observation system remain central
- Observe the space between lens conical section and corneal conical section for cells
- Avoid hitting iris to allow for darkest environment
Grading of Anterior Chamber Activity
Measured in a 1x1 conical beam
- Grade 0 (None) - No cells in field
- Grade 1 (Faint) - 6 to 15 cells
- Grade 2 (Moderate) - 16 to 25 cells
- Grade 3 (Marked) - 26 to 50 cells
- Grade 4 (Intense) - Over 50 cells
Tangential SL Technique
- Employed to observe iris
- Illumination system is swung out to almost a right angle
- Observation system remains infant of patient
- Raised lesions viisble as shadows
Specular Reflection SL Technique
- Illumination and observation systems at an equal angle to the normal of the area of cornea which you wish to assess
- Move the corneal section onto a purkinje image, causing hyper illumination of epithelium and endothelium
- Zone into less luminous endothelial layer
Retro-Illumination SL Technique
- Decouple systems when looking through pupil to allow for assessment of lenticular opacity using red reflex
Sclerotic Scatter SL Technique
- Create a corneal section then decouple the illumination so it illuminated the limbus
- TIR occurs within cornea
- Any faint corneal lesions will scatter light allowing for detection
Cobalt Blue SL Filter
- Enhances view of NaFl dye
Red-Free SL Filter
- Appears green
- Enhances appearance of vessels and haemorrhages
Neutral Density SL Filter
- Colourless/grey filter
- Reduces illumination for photosensitive patients
Wratten 12 SL Filter
- Yellow filter
- Improves ability to visualise NaFl lesions
- Useful to aid contrast in RGP fit
Van Hericks SL Technique
- 60 Degree angle between illumination and observation
- Patient needs to be looking towards the illumination system
- Conducted nasally and temporally
Van Hericks Technique Grading
VHG4 (wide open) - gap is size of corneal thickness
VHG3 (Open) - half the size of corneal thickness
VHG2 (Narrow) - quarter size of corneal thickness
VHG 1 (extremely narrow) - Less than quarter of corneal thickness
