Gonio 1 Flashcards
360 degree circular tube lined by endothelium
Schlemm’s canal
SL demarcates the termination of
Descemet’s membrane, denoted by circular deposition of collagen
Most anterior structure of the anterior chamber angle and denotes the anterior termination of the TM
Schalbes line
Anteriorly displaced and severely hypertrophic SL
Posterior embryotoxon
When schwalbe’s line is pigmented
Sampolesis line
In some eye there is a prominent thickening or elevation at the site of SL
15%
Necessary to establish the type of glaucoma
Gionoscopy
Open vs close angle
Primary vs secondary
Gonioscopy can be used for non glaucoma abnormalities
Tumors
Delivery of certain glaucoma treatments requires
Visualization of the angle
Critical angle for cornea-air interface
46.5 degrees
At the critical angle, light exits
Perpendicular to normal
When angle of incidence is greater than critical angle, light is reflected back into eye
Total internal reflection
The anterior chamber angle is not visible without
A gonioscopy lens bc the critical angle is exceeded
Bc the critical angle (46.60 IS EXCEEDED), light from the anterior chamber is
Reflected back into the eye
What is the goal of gonio
Overcome the critical angle limitation that prevent direct observation of the anterior chamber angle
Direct gonioscopy
Direct observation of the angle , spatial orientation is unchanged
Indirect gonioscopy
Angle is observed through a mirror: provide a mirror image image of the apposite angle
Gonio IOP evaluation
Rule out specific causes for high IOP or significantly asymmetric IOP
Assessment of chamber width of all glaucoma patients
- accurately diagnose open.closed
- rule out secondary glaucoma
- evaluate angle periodically
- asses angle if IOP control is lost
Corneal wedge aids in
Locating schwalbe’s line in difficult to asses angles
Location lines meet = scwalbes
Closure possible
Grade 2
Closure probable
Grade 1
Even with gonio it is impossible to predict
Certainty of ACG
Blood in the anterior chamber, common after blunt trauma
Hyphema
Avoid performing gonio 4 weeks after
Onset of hyphema
Angle recession is a tear between
Longitudinal and circular muscles of the ciliary muscle
Angle recession is associated with
Delayed onset secondary open angle glaucoma
