CO III Anesthetics and Tonometry

Topical anesthetic purpose

Temporarily anesthesize the cornea and/or conj to allow certain procedure to be done by blocking nerve conduction

Topical anesthetic actions

Increase corneal permeability to increase the clinical effectiveness of mydriatics and cycloplegics

Prevent stinging and/or burning of dilating agents, increasing pt comfort

Decrease systemic absorption due ot anesthetic-induced inhibition of tear flow

Topic anesthetic mechanism of action

Local anethestics stabilize neuronal membrane si the nuron is less permeable to Na+ ions by preventing initiation and transmission of nerve impulses, therevby producing the local anesthetic actions

Topical anesthetic procedures

ERG

Goldmann

Gonio

Forced duction

ERG purpose

Determines function of rods and cones

DTL electrode

Silver thread that touches conj/cornea to anesthesize pt

Goldmann tono

Touches cornea

Accurate

Vasovagal syncope

Handheld applanation tonometers examples

Tono pen

Anesthetic drop recommended

Gonio

Uses anesthetic drops

Uses 3-mirror and 4-mirror lens

Suctions eyeball and makes more contact with cornea so more anesthetic is needed

Measures ant. chamber angle

Forced duction testing

For pts with trapped/paretic muscles- can perform with cotton-tipped application

Can use topical lidocaine 4%, proparacaine HCl 0.5%, tetracaine HCl 0.5%, or TOOTHED FORCEPS

Toothed forceps

Used in forced duction testing

Can use topical cocaine 4%, lidocaine, proparacaine HCl 0.5%, or tetracaine HCl 0.5%

ASSESS CORNEA/CONJ OF FB

Schirmer No. 2 Test

Paper touching cornea to ASSESS THE TEAR FILM QUANTITY AND REFLEX TEARING

Anesthetic takes away the reflex tearing so that you can measure the true amount of tears

Tears collect on paper tab and blue dye drains down- measure in mm how much the blue dye has moved down to measure the quantity of the tear film

Topical anesthetic therapeutic provedures

Cornea/conj. FB removal

Lacrimal dilation and irrigation

Punctal occlusion

Periocular injections

Corneal FB removal

SLE: High mag of corneal surface

Check upper lid (lid eversion)

Lacrimal dilation and irrigation

Treats blocked tear ducts

Small metal rods widens cannulicula and injects saline- you can taste saltwater in the back of your throat

Blocked = you're meeting hard resistance

Punctal occlusion

For pts with dry eye

Insert pieces of collagen into puncta to create a clogged duct to keep tears on the eye

Periocular injections

i.e.: Avastin

Use speculum to keep eye open and inject needle

When to NOT use topical anesthetics

Pts have:

Hypersensitivity

Known allergic reaction

Cultures (preservative-free)

Cannot exceed recommended dose because they can prevent healing and cause total breakdown of the epi, stromal edema, and severe pain

NEVER GIVE TO CL WEARERS TO TAKE HOME!!!!

Topical anesthetic onset

5-20 sec

Topical anesthetic duration

1 drop lasts for 10-20 mins; can be prolonged with repeated application

Topical anesthetic side effects

Ocular: Slight disruption of the corneal epi which may cause mild keratitis, transient conj. hyperemia, light sensitivity, and transient corneal edema

Systemic: Rare; if overdose w/ systemic toxicity, effects may affect CNS, cardiovascular, or respiratory system

Examples of anesthetic agents

Proparacaine Hcl 0.5% solution

Tetraciane

ALTAFLUOR AKA BENOXINATE HCL 0.4% PLUS 0.25% FLUORESCEIN SODIUM

Proparacaine HCl 0.5%

Ester linkage- meta amino benzoic acid

aka spectro-caine, ak-tiane, alcaine, ophthaine

Tetracane Hcl 0.5% solution

Ester linkage: PABA

aka AK-T-Caine

Benoxianate HCl 0.4% plus 0.25% fluorescein sodium

AKA ALTAFLUOR

Used prior to applanation tono

Vasovagal syncope

Intense emotional experiences leads to muscle vasodilator system to become powerfully activated -> bloodflow in muscles increase, so HR slows and arterial pressure falls -> reduced bloodflow to brain = FAINTING

Can occur during applanation tono, gonio, contact lens insertion, and BIO

How to manage syncope

Never leave pt by themselves and stabilize pt's head

Instilling anesthetic drops

Check label + expiration date

Do not put cap on surface to touch the tip of bottle to pt's eye

Hold upper + lower lids and have pt look down

Applanation tono

aka Goldmann

Measures IOPs in mmHg- helps diagnose and treat all forms of glaucoma, and diagnose ocular hypertension (OHTN)

Measures IOP by providing force required to flatten the cornea- INCREASE FORCE UNTIL THE AREA OF THE CORNEA EQUALS THE AREA OF THE PROBE

Variable force applanation tonometers

Goldmann

Perkins

Tono-pen

APPLANATED AREA OF CORNEA SHOULD BE EQUAL TO THE AREA OF THE PROBE OF 3.06 MM

Applanation tono force

Size of tono tip is meant to minimize the impact of the corneal resistance and surface tension of the tear film

Turn tension knob that alters force applied to the cornea and the IOP is determined when internal part of 2 semicircles touched ach other

How to use D-KAT tono in Keeler slit lamps

Place probe at 180 or 0 degrees if less than 3D of corneal astig

If MORE than 3D of corneal astig, align prims to the negative cyl axis at EITHER THE RED LINE OR THE "A" IN D-KAT TONOS

Pre- and post-corneal scan

After instilling Altafluor, quickly scan the cornea with the cobalt blue filter in place both prior to doing tono and after tono to see if you caused something

How to do applanation tono

1. Base and joystick towards doctor

2. Align prism viewing "outside" the instrument first

3. Center prism before contact

4. Observe nasal flow or light blow mires (ghost mires) before contact

5. Hold upper lid to accommodate probe (do not push on globe and hold under the lashes)

6. If pt needs to focus on something on pt left, they need to look right

7. Properly align semicircle mires- inner should touch inner (they need to go past each other) via moving drum. Upper and lower circles should be equal size and centered.

What should you do here?

Lower pressure

What should you do here?

Pull back on probe

What should you do here?

Increase pressure a little bit (move the drum away from you)

Should you increase or decrease the measuring drum?

Increase

What's wrong here?

Mires too wide- gives a falsely high IOP

What's wrong here?

Left: Too much fluorescein

Right: Probe too low and you need to move joystick up to make semicircles equal in size

What's wrong here?

Contact with the probe is too high

gtt

How many drops in charting

Goldmann procedure

1. Keep probe on cornea for no more than 5 sec

2. If you see 2 semi-circles on the cornea and need to make fine adjustments, do so without taking the probe off the cornea

Tono procedure

After slit lamp and before gonio (NO NEED TO INSTILL ANOTHER ANESTHETIC DROP)

1. Disinfect probe/prisms by rinsing probe for 30 sec and then putting the probe in hydrogen peroxide for 10 min then rinse for 30 sec with water followed by a 60 sec immersive soak. Pat and dry. Explain procedure to pt.

2. Instil Altafluor or tono agent

3. Check pre-tono corneal staining

4. Set pressure on probe to appropriate level (10 mmHg for lab)

5. Give pt instructions, including a target

6. Put tono in place w/ cobalt blue light on probe

7. Applanate cornea

8. Adjust biomicroscope so that the fluorescein semicircular patterns are symmetrical and centered

9. Align mires

10. Retract probe and assess cornea w/ blue filter

Ensure probe is in correct side of prism hodler

If there's a glob of fluorescein...

Pull slit lamp back and put saline on tissue while holding prism holder

Dab prism holder gentle

If the mires are shaky...

Keep control of the joy stick and pressure

Mires interlocking/too high

Dial reading set too high = circles overlap a lot

Turn dial counterclockwise (toward you) until only the inner borders touch

Mires vertically misaligned

Tono probe too high or low on cornea

Use joystick to move vertical height until circles are equal in size

Mire bands too thick

Too much fluroescein, making thick rings that overestimate pressure

Ask pt to gently dab closed eye w/ tissue and clean probe tip and restart