1. determine if patient is at risk for angle closure with dilation
2. glacuoma diagnosis and treatment
3. anterior chamber disease

• for situations in which the IOP is elevated or glaucoma is suspected, the AC should be evaluated to help determine the cause of IOP elevation or help diagnose the type of glaucoma
  • if you suspect POAG, look at AC angle to determine the accessibility of the trabecular meshwork
  • with Pigment Dispersion Syndrome, evaluate teh amount of pigment in teh trabecular meshwork and along Schwalbe's line
  • with Pseudoexfoliation, evaluate the AC angle for the presence of pseudoexfoliative material

Why does anterior chamber disease indicate gonioscopy?

What are you looking for?

• History of trauma to the eyeball
  • angle recession
    • tears between the longitudinal and circular muscles of the ciliary body
    • if the ciliary body is larger than the size of the scleral spur and trabecular meshwork combined, consider angle recession
  • iridodialysis
  • increased pigmentation
  • foreign body in teh anterior chamber
• tumors or other abnormalities of the iris or ciliary body
• inflammation
  • peripheral anterior synechiae
  • inflammatory debris in the anterior chamber
• compromised vascular system
  • especially look for neovascularization when you hav ea patient with diabetes, a history of a central retinal artery occlusion, or a history of a central retinal vein occlusion
• normal vasculature
  • you will sometimes see normal BV in the angle
  • the major circle of the iris can be seen runnig circumferentially
  • radial branches may also be seen; these are often confusd with neovascularization, but the neovascular vessels run more randomly
• neovascularization
  • neo vessels tend to wander erratically and do not follow a radial or circumferential pattern
  • abnormal vessel growth tends to cover teh surface of teh iris an dnot penetrate into the stroma
  • BV should never go beyond scleral spur (if it does, think neovascularization)

• corneal or conjunctival surface disease
• epithelial basement membrane dystrophy (EBMD)
• recent hyphema

• pupil border
• iris
• ciliary body (usually pink to dark brown)
• scleral spur (projection of the sclera; white)
• trabecular meshwork (grey-pink hue due to blood in Schlemm's canal; more pigment closer to ciliary body)
• Schwalbe's line (termination of Descemet's membrane)
  • not easy to identify unless prominent
  • most easily found using narrow beam of light and observing the cornea through the gonioscopy lens - the position in which the anterior and posterior corneal light bands appear to converge is the position of Scwalbe's line
• iris processes (extend from peripheral iris to CB or SS and, ocassionally, to the posterior aspect of the TM of SL)

1. direct gonio lens (Koeppe)
2. indirect goniolens

What view does a direct gonio lens (Koeppe) give?

Why is it not used much anymore?

• allows a direct view of anterior angle structures
• not used much anymore because:
  • patient must be lying down
  • used with a head-mounted microscope and a hand-held illuminator (difficult)

1. suction/fluid lenses
2. non-suction/non-fluid lenses
3. 4-mirror lens
4. 3-mirror lens
5. 2-mirror lens
6. 1-mirror lens

suction/fluid lens:

1. Advantages:
2. Disadvantages:

Advantages:

• better image quality
• easier to use

Disadvantages:

• requires solution

non-suction/non-fluid lens:

1. Advantages:
2. Disadvantages:

Advantages:

• good for screening

Disadvantages:

• decreased image quality
• harder to manipulate

4-mirror lens:

• Design/views:
• Positive:
• Negative:

• Design/views:
  • all four mirrors are for the anterior chamber angle
• Positive:
  • quick
  • enables of view of four areas of the angle without rotating the lens
• Negative:
  • does not include mirrors to view peripheral retina

3-mirror lens:

• Design/views:
• Positive:
• Negative:

• Design/views:
  • one mirror for viewing anterior chamber (D-shaped mirror)
  • three mirrors to view various parts of the retina (2 peripheral, 1 posterior pole)
• Positive:
  • view on the level of the iris
  • good for a detailed exam of the anterior chamber (magnified)
  • includes lenses for retinal exam when dilated
• Negative:
  • lens must be rotated 360 degrees to see all of the areas of the anterior chamber

1 or 2-mirror lens:

• Design/views:
• Positive:
• Negative:

• Design/views:
  • all mirrors are to view anterior chamber angle
• Positive:
  • good for smaller apertures and children
  • lens is lighter so it is easier to hold in place
  • higher vantage point
  • good for photography (less reflection due to fewer mirrors)
• Negative:
  • more bunched-up view due to smaller mirrors
  • lens must be rotated to see all of the areas of the anterior chamber

NOTE: the smaller the mirror, the higher the plane of view (above iris)

• record an abbreviation of the most posterior structure seen in each quadrant (CB, SS, TM, SL)
• iris approach
  • flat
  • convex (associated with hyperopia; increased risk of developing angle closure glaucoma)
  • concave (associated with myopia; increased risk of pigment dispersion syndrome or pigment dispersion glaucoma)
• pigment in the trabecular meshwork (grade from 0-4)
• any abnormalities
  • synechiae
  • excessive numbers of or unusual iris processes

1. count the number of structures you see
2. Scheie's system
3. Shaffer system
4. Becker system

Grading Options:

Explain the grading criteria used for:

Count The Number of Structures You See

• Grade 0: no structures are seen, closed angle
• Grade 1: only the most anterior structure (Schwalbe's line) is seen
• Grade 2: 2 structures are seen (Schwalbe's line and TM)
• Grade 3: 3 structures are seen (Schwalbe's line, TM and SS)
• Grade 4: all 4 structures are seen (Schwalbe's line, TM, SS, and CB)

Grading Options:

Explain the grading criteria used for:

Scheie's System

• Grading angle based on visible structures:
  • Wide Open = all details and structures are easily seen
  • Grade I = slightly narrower than wide open, but all structures are visible
  • Grade II = no ciliary body visible
  • Grade III = posterior portion of trabeculum is missing
  • Grade IV = only Schwalbe's line is visible
• Grading the pigmentation of the trabeculum:
  • from 0-4 (0=least or none, 4=most)

Grading Options:

Explain the grading criteria used for:

Shaffer System

based on the angle the iris makes with the ciliary body and the trabeculum:

• Wide open angles: angle closure is impossible
  
  • Grade 4: 45-35 degree angle
  • Grade 3: 35-20 degree angle
• Narrow angle: angle closure is unlikely
  
  • Grade 2: 20-10 degree angle
• Extremely narrow angle: angle closure is probable eventually
  • Grade 1: = or < 10 degree angle
• Partial or complete closure: angle is closed at some point or circumferentially
  • Grade 0: zero degree angle

Grading Options:

Explain the grading criteria used for:

Becker System

based on two aspects of angle anatomy:

• the type of approach the iris makes with the angle
  • flat iris: wide open angle and easy to view all structures
  • convex iris: harder to view structures
• the site of iris insertion on the ciliary body
  • open angle: iris insertion allows CB to be easily seen (deeper valley)
  • narrow angle: insertion is more anterior and makes CB more difficult to be seen

fluid barrier

it is the air/cornea interface which prevents the view, so car must be taken not to trap air bubbles in teh fluid or the view will not be clear or you may not get a view

1. Celluvisc (1.0% carboxymethylcellulose)
2. Goniosol (2.5% carboxymethylcellulose)
3. Patient's own tears or artifical tears

Celluvisc

• Advantages:
• Disadvantages:

• Advantages:
  • less toxic than Goniosol
  • comes in sterile one-serving vial (no preservative)
  • easier to remove air bubbles from under lens
  • typically won't cause as much corneal staining as Goniosol
  • doesn't need to be rinsed out after procedure is finished
• Disadvantages:
  • lets air in easier
  • doesn't provide a strong seal
  • more dexterity and lens control is required by examiner

Goniosol

• Advantages:
• Disadvantages:

• Advantages:
  • less likely to get air trapped between lens and cornea
  • provides a very good seal between the lens and the eye
  • easier lens use
• Disadvantages:
  • very thick so if air is trapped, it is difficult to remove
  • must be stored upside-down to keep solution at the tip of the bottle
  • has a preservative (benzalkonium chloride)
  • the concentration and preservative increase amount of corneal staining
  • must be rinsed out of the eye thoroughly after use

with non-suction lenses which have a curve similar to a cornea

(eg. Zeiss, Possner and Sussman)

Gonioscopy Procedure:

What are the basic steps to properly prepare for using the gonio lens?

(more detail to come)

1. clean the lens
2. disinfect the lens
3. add Goniosol or Celluvisc to concave surface of lens
4. adjust slit lamp
5. instill local anesthetic
6. position the patient

Gonioscopy Procedure:

Step 1: How do you clean the lens?

• place a drop of RGP cleaner on the lens surface
• use your fingers to stir the solution over the lens
• rinse with saline or water
• BLOT dry with a Kim wipe (do NOT wipe the lens or you will scratch it!)

Gonioscopy Procedure:

Step 2: How do you disinfect the lens?

• soak in 1:10 bleach solution for 5-10 minutes or 2% Glutaraldehyde for 5 minutes
• rinse with saline
• do NOT soak in alcohol or hydrogen peroxide - it weakens the seal tha tkeeps moisture from getting inside the lens

Gonioscopy Procedure:

Step 3: How do you add the fluid barrier?

• place the gonio lens on Kim wipe upside-down so concave surface is up
• fill 1/3-1/2 of the "bowl" with solution
  • must keep air bubbles out of the solution
  • Goniosol is kept upside down to keep air out of dispensing tip
  • dealing with bubbles in the solution:
    • they will ruin your view
    • make a point by twisting a Kim wipe
    • carefully scoop out the bubble
• you may use a drop of artificial tears for the non-suction lens placement

Gonioscopy Procedure:

Step 4: How do you adjust the slit lamp?

• check the PD and focus
• microscope in clickstop
• illumination system at 0-10 degree from microscope
• medium parallelpiped
• start with about 15x magnifications

Gonioscopy Procedure:

Step 5: How do you instill local anesthetic?

• remember to discuss case history and reactions before using DPA's
• rule out any contraindications to performing gonioscopy
• place one drop of anesthetic in each eye
  • even if planning on only performing on one eye, anesthetize both eyes for blink reflex and patient comfort

Gonioscopy Procedure:

Step 6: How do you properly position the patient?

• adjust the slit lamp so that you and the patient are comfortable
  • you will have to hold the lens in place so have a support for your arm
  • some people use a Kim wipe box
• align the canthal mark with the canthus
• discuss the reasoning for performing this test, letting the patient know exactly what they will experience:
  • "I'm going to use this lens to look at the area where the fluid drains from your eye. This specialized lens is the only way to observe this area."
  • "It may feel cool.  You should not feel any pain or even irritation"

Gonioscopy Procedure:

What are the eight basic steps to placing a suction gonio lens on the patient's cornea?

1. hold the lens with the index finger and thumb (use opposite hand of eye)
2. have the patient look up
3. pull the lower lid down using the ring finger of the hand holding the gonio lens
4. rotate the lens into place on teh sclera
5. have the patient SLOWLY look straight ahead
6. center the lens on the patient's cornea
7. continue to hold the lens in place (you do NOT need to exert pressure on the globe, just hold in place)
8. rest your other fingers on the patient's cheek

Gonioscopy Procedure:

What are the three basic steps to placing a non-suction gonio lens on the patient's cornea?

1. hold lens with the index finger and thumb (use opposite hand of eye)
2. patient should look straight ahead
3. place the lens directly on the cornea

Gonioscopy Procedure:

What lens should be by your index finger when placing the gonio lens on the patient's cornea?

• put the D-shaped lens by your index finger
  • you will be viewing the patient's angle with the D-shaped lens
  • you usually start by observing the inferior angle so you want the D-shaped lens at the top of the lens when it is put on the patient's eye
  • do this by starting with the D-shaped lens by your index finger

Gonioscopy Procedure:

What is the proper way to rotate the lens into place on teh sclera?

• keep the lens horizontal until the last possible second to keep the Celluvisc in the lens
• quickly, but not violently, place the lens on the cornea without losing the fluid and without letting a bubble underneath

Gonioscopy Procedure:

How do you perform the gonioscopy examination once the lens is in place on the cornea?

• direct the beam of light towards the center of the gonio lens (this is to orient yourself)
• keep about 0-10 degrees between the microscope and the illumination
• observe the inferior angle:
  • mirror must be at the top
  • parallelpiped should be certical (perpendicular to angle being evaluated)
  • focus on the image in the miror
• observe the superior angle (rotate mirror to inferior position if needed)
• Observe the nasal and temporal angles
  • rotate mirror 180 degrees away from angle you are viewing
  • light should be rotated horizontal

Gonioscopy Procedure:

What do you do if bubbles start to form during the exam?

• you are not keeping the lens even on the cornea
• tilt the gonio lens in the direction of the bubble (as if you are trying to squish it out from underneath)
• if you can't get rid of the bubble, remove the lens and start over

Gonioscopy Procedure:

How do you properly remove the lens??

• do NOT just pull it off!!!
  • there is a fair amount of seal between the lens and the globe
  • you could create some trauma and may make a real popping sound
• break the seal by having the patient look towards their nose and gently applying pressure to the globe through the lower lid

Gonioscopy Procedure:

When and how do you irrigate the eye?

• irrigation is only necessary if you use Goniosol (very uncomfortable)
• how to irrigate:

1. make a dam of paper towels
2. use saline or artificial tears to irrigate
3. spray a stream into the eye then blot with a towel or Kim wipe
4. repeat several times

Gonioscopy Procedure:

What do you do after the lens has been removed?

• clean the gonio lens (do NOT let Goniosol dry on the lens)
• check for corneal staining

• too much pressure from the gonio lens on the cornea may distort the true appearance of the angle
  • eg. a flattened cornea will increase pressure, therefore bulge open the angle
• the angle may appear closed if the iris bows - all structures may be visible with a higher vantage point or after angling the gonio lens

Gonioscopy Procedure:

What are four common errors with gonioscopy that result in an inability to see any of the structures?

1. poor lens centration - the lens needs to be centered and flat over the corneal apex
2. bubbles in the Celluvisc - you may have started with a bubble or let one under the lens by not holding the lens flatly against the cornea
3. poor slit lamp positioning - the parallelpiped isn't on the miror or you are not focused on the mirror
4. obstruction of the view - your finger, thumb or a part of the biomicroscope may be hiding your view