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OTM 3-Gonioscopy Exam With Accurate Answers
100% Verified
What is the structure that produces the aqueous humor? Ciliary body
What is goniscopy used for? To view the angle of drainage within the eye
The Trabecular Meshwork can be described as? Swiss cheese like (percolated)
What happens to the angle during dilation? Iris pulls back into the angle during dilation *If someone has a very narrow outflow angle dilation can create an acute angle closure (this would be BAD!)
Which is more likely to have a smaller drainage angle: hyperope or myope? Hyperope (smaller axial length- smaller eye)
What is a good parameter what you want to see in each quadrant before you will feel comfortable dilating Anterior trabecular meshwork (TM) in at least 3/4 quadrants *There is no real requirement but whatever you are personally comfortable with
Rubiosis Blood vessels growing on the iris (BVs grow in and tighten it up — blocking outflow of the aqueous)
When would we perform gonioscopy?
- Before dilation when we believe the individual has narrow angles
- Anyone who has had acute trauma to the eye (car accident, professions such as Boxer)
- Evidence of neoplasm, elevation, &/or unusual pigment
If using ultrasound to analyze the angle we would want _____ microns as a minimum in order to dilate 250 microns
Direct: Koeppe method of angle estimation Steep convex "plus" lens (50D) *Great anatomical view *Rare-supine patient- surgical
Ultrasound biomicroscopy (UBM) Uses high frequency ultrasound to produce high resolution image of the anterior chamber angle structure
-Steep surface and viscous solution required What is the image produced by the gonio lens? ERECT virtual image in center lens Finally something is right side up!
In the mirror of the gonio lens there is what view? An indirect inverted view of the angle
What are the advantages of the 3 mirror gonioscopy lens? stable and undistorted image
What are the uses for a 3 mirror gonio lens? Peripheral fundus evaluation as well as angle evaluation
What are the disadvantages of the 3 mirror gonio lens?
- Needs rotation (increases time)
- More difficult to insert/ remove (pt comfort)
- Solution must be utilized along with the procedure (can degrade the quality of the fundus photo
Advantages of a 4 mirror gonioscopy lens?
- Quicker- no rotation in the lens to view all 4 angles
- Easy in/ out* Flangless does not require fluid
A flangeless 4 mirror gonio lens can be used for? Compression/ indentation gonioscopy
Disadvantages of the 4 mirror gonio lens?
- More difficult to control stability for some-flange can fix this
- May see more corneal wrinkling-image may even be degraded from time to time
If you are able to view corneal folds during gonioscopy this indicates to you? You are applying too much pressure to the cornea *Different corneas can take different amounts of pressure *Think of saran wrap pulled and you can not see through it
The ____ 4 mirror has no handle Sussman
The _____ 4 mirror has a handle Posner
What to do if unable to look into view for gonio? Tilt lens towards mirror (away from the pupil)
What kind of light set up on the slit lamp should be used for gonio? Use a parallelpiped -increased light= constriction= false WIDER angle view
Setup/ procedure for gonioscopy
- After IOP is taken J pt is already numb)
- Instruct pt
- Constant reassurance for the pt
Depth
The angle is where the cornea meets the? Sclera
the angle is responsible for? Drainage of aqueous
How many degrees is the angle? 360 degrees
Comparison of Van Herick (VH) to gonio a grade 4 angle in VH would probably have _____ as the most posterior structure visualized CBB (ciliary body band)
What is the most posterior structure that would be seen in a grade 2 VH evaluation? Trabecular meshwork (TM)
What is the color of the cillary body band (CBB)? Light gray — > dark brown (think dark chocolate)
Which structure of the angle is closest to the iris? Most posterior structure= CBB
What is the function of the CBB? Responsible for aqueous production
The CBB is located _____ to the iris root Anterior
How wide is the CBB? Width varies depending on iris contour
What is the color of the scleral spur (SS)? White — > mild gray band (think BONE white)
The scleral spur will be more prominently seen with? A dark TM (CBB/TM contrast= think OREO)
The scleral spur represents? The projection of the sclera -ring of collagen parallel to limbus
So where is the Scleral spur? (Get ready for a fun pic!)
Contraindications for gonioscopy
- Corneal abrasion or moderate/ severe keratitis
Should you perform gonioscopy before or after tonometry? After tonometry! If you perform gonio before tono you will artificially LOWER the IOP (pressure of pushing on cornea will push more aqueous out of the TM — > more outflow with equal inflow will artificially lower the IOP)
An open angle on corneal wedge technique will appear as? Iris beam does NOT meet the junction where 2 corneal beams meet
Where is Schlemm's canal located? Behind trabecular meshwork (TM)
A closed angle on corneal wedge technique will appear as? Iris beam touched junction where 2 corneal beams meet
Can we name the structures based on a photo? LETS FIND OUT!
What is the function of schlemm's canal? Giant vacuoles, where aqueous drains
What is corneal wedge technique?
- Use an optic section, high intensite light, 20 deg SL angle, dim room
- Light focused on: iris, anterior cornea, and posterior cornea
- Anterior/ posterior corneal lights meet= SL
Is Schlemm's canal a structure viewed during gonio? NOPE
Grade 4 would indicate? Widest angle Ciliary body can be visualized w/o tilting the lens
A grade 4 angle (35- 45 deg) is characteristic of what conditions? Myopia and pseudophakia
A grade 1 angle (10 deg) would indicate? A very narrow angle in which only the Schwalbe line & perhaps the top of the trabeculum can be identified
A grade 3 angle (25-35 deg) would indicate? An open angle in which the scleral spur is visible
Ectopic pupil
What is a normal configuration of the iris? Flat= normal
What would be the appearance of a plateau iris? Up and out apperance
What would be the appearance of a convex iris? Iris bowed anteriorly towards cornea -sight of angle may be obstructed (narrow approach) -see angle if possible by positioning the patients gaze or gonio lens (convex iris technique)
How do you accommodate a narrow angle approach on gonio? Alter the angle of the gonioscopy lens to allow for a narrow angle approach
What is the appearance of a concave iris? Iris bowed posteriorly towards crystalline lens
What are the common causes for anterior neovascularization?
- Proliferative diabetic retinopathy
- CRVO
- Ocular ischemia
Peripheral anterior synechiae (PAS) Note: this is different than posterior synechiae where the posterior part of the iris gets stuck to the lens -Iris tissue adhesion to angle wall or cornea -Broad large band of iris (TENT) -since it is a full thickness adhesion to the angle wall it may prevent aqueous from draining out
T/F: a peripheral anterior synechiae (PAS) is a normal finding False, this is never a normal finding
Which gonio lens will give you a better view of iris configuration? 3 mirror
How would you visualize an angle obstructed by peripheral anterior synechiae (PAS)? Perform indentation gonioscopy Need a flangeless 4 to do this Place flangeless 4 on the cornea and cause corneal folds when you indent — > this will force aqueous humor to push back against the iris (Most ODs don't do this) With indentation part of the angle is visualized but PAS remain
What is the theory behind depression (indentation) gonioscopy? A small diameter lens (i.e. 4M lens) is used to flatten the cornea. This allows for aqueous to be pushed down into the angle, forcing iris to move posteriorly.
-may cause TM damage -often features: increase prominence of SS & observation torn iris *Widened view of CBB
Besides history what can help you make a diagnosis of angle recession? History of trauma, retinal pigmented lesion may be present, blood in the angle Look at other eye for angle comparison or other quadrants
What is pigment dispersion syndrome? Condition where there is too much pigment in the trabecular meshwork Too much pigment in the TM will block outflow — > secondary glaucoma
In someone with pigment dispersion syndrome what will you see on the iris? Retroillumination of the iris will cause you to see a red reflex and you may see pigment stuck on the cornea *Must perform gonioscopy
Posterior embryotoxin Anterior displaces schwalbe's line
We would expect a myope or hyperope to have a wider angle? Myope
Would we expect a male or female to have a larger angle? Male
What is considered a significant difference between quadrants? 1/2 a structure
Sampaolesi's line represents? Pigment dispersion- pigment deposit (Pseudo)exfoliation
_____ angle is the widest & most pigmented Inferior (due to gravity)
What happens to the angle with age? It becomes more shallow -may be due to lenticular changes
How to record your gonioscopy results?
- Describe the configuration: flat, steep, convex, concave
- Identify most posteriorly visible structure: CBB, scleral spur, TM, schwalbe's line, no structure visible
- Grade amount of pigment in TM for each quadrant
What does an open angle look like?
What does a closed angle look like?
Gonioscopy is contraindicated in? Patients with a history of a penetrating injury or hyphema (blood in the anterior chamber)
Schwalbe's Line marks the anatomical end of the? Cornea
Angles are usually the largest ______ Inferiorly
Angles are usually smallest _____ Superiorly
Where is the pigment densest? Lightest? Densest: inferiorly Lightest: superiorly
How do you clean the gonio lens?
- Regular disinfecting: clean the lens with soap and water
- High level disinfecting: soak for 25 minutes in a 2% gluteraldehyde solution (caution! This is strong so follow directions carefully)
What are the 3 mirrors angles in a 3 mirror gonioscopy lens? 59, 67, and 73 degrees
Placed at 120 degree intervals
Which mirror(s) on the 3 mirror gonio lens is used to visualize the angle? The smallest mirror= "Thumbnail" aka bullet The mirror with the 59 degree tilt
What is the magnification that should be used when viewing gonioscopy structures? 16X
When performing gonioscopy the angle you are looking in the mirror at is actually _____ 180 degrees away
