Clinical: Biomicroscopy And Illumination Techniques Flashcards
What is the anterior chamber?
The space between the cornea and the iris/lens
What is the anterior chamber filled with?
Aqueous humor
What is aqueous humor?
Clear fluid secreted by the ciliary body
How does aqueous humor travel through the eye?
Via the pupil and exits through the trabecular meshwork
Where is trabecular meshwork located?
In the anterior chamber angle
What is the issue with narrow angles?
They have the potential to close and reduce the aqueous outflow by blocking the path to trabecular meshwork
What is angle closure glaucoma?
Pressure increase due to aqueous buildup
How does angle closure glaucoma occur?
Naturally or can be induced by certain medications
What is the purpose of the Van Herick technique?
To assess the depth and openness of the anterior chamber and anterior chamber angle and determine if the patient is at risk of angle closure
How is the van herick technique assessed?
By comparing the thickness of the cornea to the depth of the peripheral anterior angle chamber
Angle, mag, and beam for van herick technique?
-60 degrees
-medium mag (~16x)
-optic section and full height
Where do you focus the beam when performing van herick?
On the cornea at the edge of the limbus on both nasal and temporal side
Grade 1 van herick
< 1:4
Grade 2 van herick
1:4
Grade 3 van herick:
1:2
Grade 4 van herick:
1:1 or > 1:1
How does the anterior chamber appear normally?
Dark and quiet (empty)
What can be seen in the anterior chamber during light scatter?
-abnormal white blood cells
-pigment and protein
How do white blood cells appear in anterior chamber?
Small white/grey dots
How do proteins appear in the anterior chamber?
Haze
How do red blood cells appear in the anterior chamber?
Red/brown dots
How does pigment appear in anterior chamber?
Brown dots
Angle, mag, illumination, and beam for anterior chamber eval:
-30-45 degrees
-high mag (25x or 40x)
-full illumination
-2-3mm parallel-piped or conical beam
How to perform anterior chamber evaluation after setup?
-place beam within the pupil focusing on cornea
-push lamp to focus on the anterior lens surface
-pull back to focus halfway between cornea and lens
-scan and evaluate
How to prevent reflection during anterior chamber evaluation?
Adjust your beam to fit within the pupil
Where should the light beam NOT touch during anterior chamber evaluation?
-corneal reflex
-iris
-lenticular reflex
Grade 0 cells and flare:
No cells and no flare
Trace cells and flare grading:
-1-5 cells per field
-no flare
Grade 1+ cells and flare:
-6-15 cells
-faint flare
Grade 2+ cells and flare:
-16-25 cells
-moderate flare, lens and iris clear
Grade 3+ cells and flare:
-26-50 cells
-marked flare, iris and lens hazy
Grade 4+ cells and flare:
-50+ cells
-intense flare, fixed coagulation (no movement)
What is the purpose of the indirect illumination test?
To exam the cornea with indirect light
What is indirect illumination useful for?
-corneal infiltrates
-corneal scars
-fine corneal neovascularization
-corneal deposits
What is the method of indirect illumination?
The object/area being viewed is lit indirectly by reflections or scatter from the adjacent beam
Angle, mag, and beam for indirect illumination
-45-60 degrees
-medium mag
-2-4mm parallelpiped
How to perform indirect illumination:
-move slit lamp to area you want to examine
-move slit beam out of click stop to focus beam next to the area
What is the purpose of sclerotic scatter?
To evaluate the cornea for opacities and irregularities using internal reflection
What is sclerotic scattering used for?
Viewing corneal scars and other defects
How does a normal cornea appear during sclerotic scatter?
Dark
Angle, mag, and beam for sclerotic scatter
-45 degrees
-low mag
-narrow parallelpiped
How to perform sclerotic scattering:
-focus the beam at the temporal limbus and look for a halo of light to form on the nasal limbus
-observe cornea to look for haze or opacities
What is retroillumination?
When light is reflected off the most posterior structure providing a backlit effect to observe anterior structures
What are the two types of retroilluminatin?
Direct and indirect
What is retroilluminatin useful for?
-subtle corneal opacities -> scars, neovascularization
-lens opacities
-iris transillumination defects
Steps to direct retroillumination:
-low mag and parallelpiped with 45-60 degrees angle
-focus on what you want to observe
-move the light beam out of click to reflect light off the surface of the iris and illuminate the area from behind
Steps to indirect retroillumination:
-move light beam out of click to reflect the incident beam off the surface of the iris and illuminate the area you want to observe from behind
-the area observed is NOT in the direct pathway of the reflected light
How is retroillumination performed off of the retina?
-low-med mag
-coaxial beam or just off coaxial
-beam height that fits directly in pupil (dilated pt)
-you will observe a bright orange reflex off the retina
What is the purpose of specular \ reflection?
To examine the corneal endothelium or crystalline lens
When does specular reflection occur?
When the angle of incidence and the angle of reflection os the slit lamp beam are equal
How to perform specular reflection:
-low mag using medium parallelpiped
- focus on cornea 30-45 degrees
-adjust slit lamp or change beam until beam split intersects with the corneal reflex
-increase mag to high
-sharply focus the slit lamp on endothelium and observe
What is fuch’s endothelial dystrophy?
-loss of corneal endothelial cells
-formation of gutatta -> accumulations of collagen on descemets membrane where endothelial cells are gone
Purpose of everting eyelids:
To examine the palpebral conj of upper eyelid
When to evert upper lids:
-contact lens wearers
-red eye
-foreign body
How to record finding of palpebral conj:
Normal, or pink and quiet -> DONT need to specify that eyelid was everted
