Gonio structures Flashcards
Importance of gonio?
to check and view optic nerves and glaucoma
and observe angles
function of angle
aqueous production and aqueous outflow
Review: van herick technique grades
Grade 4: aacd >= ACT
Grade 3: aacd 1/2 - 1/3 ACT
grade 2: aacd 1/4 act
grade 1: aacd < 1/4 act
Gonio Principles
Critical angle: light which comes from the anterior chamber angle (ACA) usually undergoes total internal reflection. A viewer cannot observe angle with just direct ophthalmoscope or slit lamp
General concepts
superior angle generally the narrowest
inferior the widest
greatest pigment generally in the inferior angle
factors affecting angle width - chamber depth
refractive error: myopes and emmetropes have wider angles than hyperopes
age: angle narrower with age
race: asians smaller angles
cataract: lenticular swelling makes chamber shallow
aphakia: iris flattens
peripheral iridectomy: alllows iris to lie flatter/angle wider
trauma: surgical, accidental
congenital abnormalities
anatomy of the anterio chamber angle
posterior wall: root of the iris
angle recess: the longitudinal bundles of the ciliary muscle
anterior wall: scleral spur, trabecular meshwork, schwalbe’s line, schlemm’s canal (behind the trabecular meshwork) (acronym: I Can’t See This Stuff)
Iris
pupillary ruff, collarette, crypts
contour: slightly convex (average adult, hyperope)
flat: post iridotomy, aphakia, pseudphakia
slightly concave: myopes and aphakes
abnormal: pigment disperson syndrome
plateau iris configuration
Roll of Fuch’s
Largest roll of the iris
last roll of the iris
plateau iris syndrome: a feature of this syndrome an abnormally prominent last roll
root of the iris
posterior border of the angle
fairly flat
inserts cil body unevenly, creating scaloped edge
thinnest portion of the iris
ciliary band
forms angle recess
anterior aspect of ciliary muscle
pigmented structure and is typically gray to black
width of the band depends on level of iris insertion
consistent width, not usually wider than TM
Scleral spur
seen as white/grayish white line
projection of collagen fibers from inner sclera
represents most anterior portion of sclera
may be obsured by iris processes vaulting over it pigment
trabeculae beams attach at anterior edge
ciliary body muscle fibers attach posteriorly
trabeculum
spans anteriorly from end of descemet’s membrane at schwalbe’s line posterior to blend with scleral spur
typically light to dark brown (pigment color vary)
appears as intricate latticework
may appaear translucent because of spaces by drainage system
consists of crisscrossing collagen fibers covered by endothelium
bridges scheral sulcus in schlemm’s canal
Trabeculum - 2 portions
anterior: non-pigmented, non-filtering (b/w post. portion and SL)
psterior: more pigment, filtering, inc. pigmentation with aging and disease processes, skin and hair color have little correlation with trabecular pigment
Schwalbe’s line
most anterior portion of the angle
represents end of descemet’s membrane
site of transition between transparent corneal tissue and off-white translucent tissue of scleral
transition of steeper corneal surface to flatter curvature of angle recess and sclera
appearance: too faint, but sometimes appears as thin white line
corneal light wedge: cornea will appear in 3D, schwalbe’s line will collapse to 2D
Schwalbe’s line
sampaolesi’s line: pigmented schwalbe’s line
posterior ebryotoxon: SL is prominent and anterior (normal varient, may also be associated with abnormal structure such as axenfeld-rieger syndrome
canal of schlemm
located behind TM
not normally visible
blood in schlemm’s will appear as pink band
iris process
iris process bridge the angle recess from ant. iris surface to TM usually in scleral spur area
process are pigmented in brown iridies
must be differentiated from anterior synechiae
may be broken with traumatic angle recession
Iris process vs. anterior synechiae
iris process: fine, extend scleral spur, follow concavity of recess, underly structures seen, iris moves with identation, broken with angle recession
synechiae: broad, extend beyond scleral spur, bridge concavity of recess, obscure structures, resist movement, intact
abnormal structure: evidence of trauma
angle recession: rupture cil body face, resulting in tear between longitudinal and circular fibers of ciliary muscle
b= cyclodialysis - creation of communication b/n anterior chamber of eye and suprachoroidal space (glaucoma)
c= irdodialysis - sepration of iris from ciliary attachment
d = meshwork tears
pigment dispersion syndromekruckenberg spindle
pigment on endothelium of cornea, typically elongated vertical pattern
iris defects, pigment on iris surface and pigment in angle
pseudoexfoliation syndrome
systemic disease with primary ocular manifestation characterized by deposition of whitish grey protein on lens capsule, iris, ciliary body, zonules, corneal endothelium and trabecular meshwork.
gonio clinical correlation
corneal: pigment, blood staining, trauma
anterior chamber: inflammation, blood
lens: exfoliation, pigment, catarct, subluxation
vitreous: inflammation, blood, prolapse
retina: ischemia, inflammation, trauma
optic nerve: Glaucomatous cupping, atrophy
gonio indications
assesss depth of anterior chamber anlge
patient with high IOP
patients with glaucoma
signs of pigmentary glaucoma
history of ocular trauma
inflammation of suspicion of synechia
any ocular ischemia rubeosis iridis (diabetic retinopathy, hypertensive retinopathy, central retinal artery occulsion, central retinal vein occlusion, branch retinal vein occlusion)
when masses seen/suspected (intumescence, dislocation, or subluxation of crystalline lens, iris atrophy, evidence of ocular trauma observed, congenital anterior chamber angle anomalies)
gonio contraindications
perforated globe, intraocular fb, intraorbital fb, trauma (acute), recent ocular surgery, corneal insult, sensitivity to pharmaceuticals, infection
