Lecture 6: Gonioscopy, Ultrasound, Biomicroscopy, Angle Imaging Flashcards
Which goniocope has better optics and stability of image? (3 mirror/4 mirror)
3 mirror
What is the purpose of gonioscopy specifically for glaucoma?
Differentiate between POAG & PACG
- Diagnose
- Congenital
- Secondary
- Angle recession
- Uveitic
- Neovascularization
- ICE (Iridocorneal endothelial syndrome)
- tumors & cyst
- trauma & FB
What are the 6 key structures to evaluate during gonioscopy?
- Pupil border
- Peripheral iris
- Ciliary body band
- Scleral spur
- Trabecular meshwark
- Schwalbe’s line
Label the image
- Pupil border
- Iris periphery
- Ciliary body
- Scleral spur
- Trabecular meshwork
- Schwalbe’s line
Ciliary body band is the most (anterior/posterior) structure
posterior
Where is the insertion point of the iris root located?
ciliary body
Width of the ciliary body depends on the position of iris insertion. Tends to be narrower in ___ eyes & wider in ___ eyes.
hyperopic, myopic
Angle recess represents the dipping of the ______________.
iris as it inserts into the ciliary body
____ is the most anterior pont of the sclera
Scleral spur
Where is the site of attachment of the longitudinal muscle of the ciliary body located?
Scleral Spur
Gonioscopically, the scleral spur is (posterior/anterior) to TM
posterior
This angle structure appears pink/dull brown/slate gray
ciliary body
This angle structure appears as a narrow, dense, shiny whitish band
scleral spur
Scleral spur is necessary to hold ___ open. What happens if the scleral spur is shortened?
Schlemm’s canal
- Shortened scleral spur may reduce mvmt & allow collapse of schlemm’s canal
Trabecular meshwork extends between what 2 structures?
Scleral spur & schwalbe’s line
- Posterior adjacent to scleral spur
- Anterior adjacent to schwalbe’s line
In trabecular meshwork which portion is the functional pigmented part & which portion is the nonfunctinonal part?
- The posterior is the functional pigmented part
- Grayish to translucent appearance if absent pigment
- The anterior is the nonfunctional part lies adjacetn to Schwalbe’s line
- Pale/whitish color
Which part of the angle does pigment accumulate with increasing age?
TM
What are iris processes?
small extensions from the anterior surface of the iris
- Uveal extensions from iris to TM
- Insert at level of scleral spur and cover the ciliary body to varying extent
Iris processes are found in __% of people
35
What are the three types of grading chamber angle? Describe each
- Scheie grading: most posterior structure visible
- Shaffer system: assess geometric angle width in 4 grades angle potential for occlusion
- Spaeth system: spaeth system: 3D structure of angle - level of iris insertion and peripheral iris configuration
If the gonio angle is compressed too hard on the eye, this angle structure can fill up with blood
Schlemm’s Canal
- the episcleral veins and episcleral venous pressure exceeds IOP
This may be identified in the non-pigmented angle as a slightly darker line deep to the posterior trabecular meshwork
schlemm’s canal
Describe the composition of the schlemm’s canal (3)
- Endothelial cells surrounded by CT
- internal collector channels
- connected to episcleral & conjunctival veins via exeternal collector channels, intrascleral venous plexus, deep scleral plexus & aqueous veins
When would a blood vessel be abnormal when looking at the angle of the eye?
- When blood vessels cross scleral spur onto the TM is abnormal
Vessels run a ___ pattern
radial
Describe Scheie Grading System
- grading system is baesd on visible structures
- Scheie granding system is verversed relative to Shaffer system
What is the most anterior angle structure?
Schwalbe’s line
Which angle structure marks the transition from transparent cornea to opaque scleral tissue?
Schwalbe’s line
Appear as an opaque line
Schwalbe’s line
This structure represents the peripheral termination of descemet’s membrane & anterior limit of trabecula
Schwalbe’s line
What lies just anteriorly to schwalbe’s line?
Sampaolesi’s line
Grading of the angle main aims are to evaluate what? (3) & is important to determine what? (5)
Main aims:
- functional status of the angle
- degree of closure
- risk of further closure
It is important to determine:
- Angle width
- Shape & contour of the peripheral iris
- Most posterior structure seen
- Presence of peripheral anterior synechiae (PAS)
- Amount of trabecular pigmentation
Describe Shaffer grading system
- Grades angle width in degrees, and risk of closure
- Does not provide information on iris shape or level of insertion
Describe Spaeth grading system
Describe pigment grading
- grade amount of pigment present in the TM
- Greater pigment = increase risk of aqueous blockage
Describe grading of the iris approach
Abnormal gonioscopic findings may include
- Peripheral angle synechiae (PAS)
- Excessive pigmentation
- Blood vessels (cross scleral spur –> TM)
- Angle recession
What is Peripheral Anterior Synechiae (PAS)? What causes PAS? (6)
- Adhesion of the iris root to the TM, scleral spur or peripheral cornea
- May be caused by
- position angle closure
- creeping angle closure
- inflammation
- neovascular membranes
- migrating corneal endothelial cells (ICE syndrome: bottom photo)
- Trauma
What can cause excessive pigmentation in the TM
- Pigment dispersion syndrome (PDS)
- Pigmentary glaucoma (PDG)
- Pseudoexfoliation syndrome (PXS)
- Uveitis
- Trauama
Pigment dispersion is (unilateral/bilateral)
bilateral
What is pigment dispersion?
- Characterized liberation of pigment granules from the iris pigment epithelium and deposition in the anterior surface including zonules & ciliary body
- Elevation of IOP is caused by pigmentary obstruction of intrabecular spaces and damage to TM
What does pigment dispersion look like when performing gonioscopy?
- Wide open angle
- Concavity of peripheral iris near the insertion
- Trabecular hyperpigmentation
- Pigmentation is most pronounced on the posterior TM
- Dense, uniform band
- Schwalbe’s line is often pigmented too
- Pigment heaviest inferiorly
- Diminishing to almost no pigment superiorly
In pseudoexfoliation syndrome, gonioscopy shows what? (5)
- TM hyper pigmentation
- Pigment greatest inferiorly
- Pigment lies on surface of TM
- Pigment has a “patchy” or “chocolate chip” appearance
- Pigmentation running onto or anterior to schwalbe’s line also known as sampolesi’s line is also frequently seen
Always do ___ on patients with CRVO. Why?
gonio
- dont want to miss any neo in angle.. happens here first with these patients
Patients with “buds” at the pupillary margin will likely preced __ in the angle
neo
Don’t apply excessive pressure when viewing neo. why?
even light pressure can collapse the tufts of neo and render them clinical invisible
What can cause blood in schlemm’s canal?
- pressure from gonio lens - but goes away
- Pathological
- cavernous sinus fistual
- struge weber syndrome
- obstruction of superior vena cava
Always perform gonio on patients with blunt trauma. What should you look for?
- Angle recession
- Trabecular dialysis
- Iridodialysis
- Cyclodialysis
- Presence of small FB
Describe angle recession
- Characterized by marked widening of the CBB
- important to compare normal to abnormal areas within same eye
angle recession is the most common sign of ___
post contusional injury - 9% of pt will develop angle recession glc
Describe cysts
- incidental finding
- if asymptomatic = no tx required
Describe tumors in the eye
- rare - iris or ciliary body melanoma
What is ultrasound biomicroscopy (UBM)
- Non-invasive technique for evaluating the presence of narrow anterior chamber angles, angle closure glaucoma, and ciliary body
- Direct contact of transducer to the eye or through immersion technique
- Provides quantitative measurements of the anterior chamber angle (ACA) that are useful for accurate diagnosis and management
What are the standard measurements in UBM?
- Angle opening distance (AOD): perpendicular distance between the trabecular meshwor at a point 500um anterior to the scleral spur, and the iris
- Angle recess area (ARA): triangular area bound between the AOD line and the angle recess
- Anterior chamber depth (ACD): distance between the central corneal endothelium and the anterior surface of the lens
- Lens vaults: distance of the lens located anterior to the perpendicular line between the scleral spurs
Why would you perform UBM vs gonioscopy?
- Detailed
- Pt dark adapted
- Changes position of angle anatomy
- May reveal angle closure
- Can be difficult to determine details via gonio in some cases
- anatomy can be tough
- can perform gonio with dim illumination - but difficult to see
- can assist in diagnosis of ant seg tumors/cyst
- can assist in the diagnosis of primary angle closure glaucoma
UBM is particularly useful to confirm presence of ____
iris plateau
Describe the image (UBM)
Typical UBM section in a patient with wide open angle
Describe the image (UBM)
- The posterior concavity of peripheral iris in a patient with pigment dispersion syndrome
Describe the image (UBM)
Pupillary block
What is pupillary block?
- Flow of aqueous from the posterior anterior chamber is inhibited, causing iris bombe
What causes pupillary block?
- may be simply due to genetic predisposition & anterior segment anatomy, e.g. convex iris configuration (primary pupil block)
- OR from posterior synechiae, lenticular enlargement or displacement of the lens or IOL (secondary pupil block)
What is the difference between relative vs. absoulte pupil block?
- Absolute is RARE: iris is completely bound down to the lens by posterior synechiae
Describe the image (UBM)
Pupillary block: e.g. iris bombe
Describe the image (UBM)
UBM of narrow angle in a patient with acute intermittent angle closure glaucoma due to pupillary block
Describe the image (UBM)
In this case the iris root touches th peripheral cornea ahead of the trabecula due to pupillary block
Describe the image (UBM)
-
Incomplete angle closure
- the angular recess creates an open tunnel, which is located between the iris and trabecula
Describe the image (UBM)
-
Complete angle closure
- complete occlusion of the TM
Describe the image (UBM)
-
Plateau iris syndrome
- Flat iris configuration with a sharp bending back at level of the trabecula which gives rise rise to the creation of a particularly narrow angular recess
- When pupil dilates, the iris tissue bunches up in (crowds). the restricted angular space and closes the angle
Patients with plateau iris syndrome need ____.
IRIDOPLASTY
- Iridectomy or laser iridotomy are ineffective. These patients need IRIDOPLASTY
Describe the image (UBM)
- Iris & ciliary body cyst
What does the AS-OCT standard measure? (6)
-
Corneal thickness (CT)
- distance btw the anterior surface of the epithelium and posterior surface of the endothelium
-
Epithelial thickness (ET)
- distance below tearm film –> above Bowman’s layer
-
Angle opening distance (AOD)
- perependicular distance betwen TM at a point 500u anterior –> scleral spur & iris
-
Angle recess area (ARA)
- triangular area bound between the AOD line and the angle recess
-
Anterior chamber depth (ACD)
- distance btw central corneal endothelium and the anterior surface of the lens
-
Lens vault
- distance of lens located anterior to the perpendicular line between the scleral spurs
What are the limitations of AS-OCT? (3)
- Cannot penetrate iris
- Can not define scleral spur 25% of time
- therefore can not accurately define angle anatomy
- Therefore our diganosis may be wrong 25% of time
- Uses light to obtain the image so angle anatomy will be altered
What is the difference between AS-OCT vs. UBM
- Both angle imaging technologies
- Both produce cross-sectional images of the anterior segment
-
UBM
-
can view ciliary body anatomy
- huge role in glc diagnosis & tx
- well established tech
- more involvement to obtain images
-
can view ciliary body anatomy
-
AS-OCT
- higher res images of iris and angle
- obtaining image is very easy
- Potential for further development
