ED Slit-Lamp Examination

Andrew Shannon, MD MPH

Department of Emergency Medicine

Jacobi Medical Center

Why bother?

• ED Ophthalmology goals:– R/O or R/I ruptured globe, retained foreign body, corneal abrasion,

diagnose HSV corneal ulcer

• The Slit-lamp Exam:– makes you look like you know what you’re doing– provides superior magnification & stabilizes pt’s head for removal of

corneal FB– tangential illumination aids in dx of uveitis/iritis

• “cells and flare”

– billing?

• Eye exam interactive tutorial at– http://www.kellogg.umich.edu/theeyeshaveit/index.html

The Slit Lamp• Low- to medium-powered binocular horizontally

mounted microscope

1) Magnification

2) Elevation

3) Joystick for R/L movement & to focus

4) Slit width &/or height

5) Slit centration or off-set

6) Slit height & Intensity

– Slit width• Wide- survey globe/cornea• Narrow- depth, width & position of small abnormalities

– beam as wide as cornea is thick– forms a parallelepiped volume: a box of illuminated tissue is seen

• Thin (slit)- narrowest beam forms an optical section – so thin it's just discernible– valuating small changes in clarity & pinpointing depth of pathology

– Light-source intensity• Medium to high: most purposes • High: optical section

– Filters• neutral, cobalt blue (for fluorescein), red-free

– Magnification• low power (~10x) is used for survey• medium to high (16-40x) for optic section & parallelepiped • high (40x) for specular reflection

– normally, light is focused at same point as microscope (“parfocal”)

(+) Seidel’s test: ruptured globe“Welder’s keratitis”-- diffuse punctate lesions

of the cornea caused by UV radiation

dendritic appearance of HSV keratitislinear corneal abrasion

Slit lamp technique• Start w/ 10x eyepieces & lower powered objective

– (“1x” or “12” on JMC scopes)

• Use lowest voltage setting on transformer– ensure open aperture

• Select the longest slit length• Adjust chin rest

– Pt's eyes approx level w/ marker on head rest

• Slit arm in line w/ microscope• Lamp height w/ slit beam centered vertically on Pt's

medial canthus• Focus by moving joystick

locking nut: loose for free movementOcular focus to 0

adjust beam height for tall, narrow vertical beam

adjust width for narrow beam w/ good illumination

slit width adjustmen

t

filter rheostat

magnification adjustment

beam height

slit-width adjustment

slit-arm locking knob

locking nut (horizontal)

intensity locking bar (vertical)

focus &

lamp height

• Magnification adjustment can be found in various locations, including btwn the eyepieces

• The filter rheostat can be used to decrease Pt discomfort under exam w/ the lamp (neutral density filter)

Position of the Light– Slit-arm pivots 1800 around microscope mount

• 450 angle, directed temporal to nasal is standard• In-line w/ scope for initial survey of lids, lashes, lacrimals,

conjunctiva and sclera

• Methods of viewing– Direct illumination: beam directly pointed at specimen

• gross pathology

– Retro-illumination: beam de-centered to illuminate behind area of interest while it is still in focus

• may bring out subtle optical changes – thin vascularization, small incisions, endothelial abnormalities

– Sclerotic scatter: light spreads by total internal reflection • uses a beam ~1mm wide, ½ height of cornea & pointed at limbus• subtle abnormalities as light through the cornea scatters off of any

pathology

Forehead should be in contact w/ restraint

Eyeline should be at level of indicator

Angle of slit-arm ~ 600

Direct/focal illumination• Most common; focused slit; magnification 10x40x

– wide beam for surface study; narrow beam for sections

• Broad beam (parallelepiped) section of cornea• 2mm slit: corneal surface & stroma

• to ascertain depth (FB, abrasion)

• Narrow beam (optic section): easier to determine precise depth• resolution improved by reducing slit width; clarity improved w/ increasing mag

– angle btwn slit-arm & scope ~ 450 - 600

• increasing angle up to 900 will increase amnt of cross-section

– 4 layers of corneal section:• tears (outer)

• epithelium (& Bowman’s membrane)

• stroma: seen as central gray granular area

• endothelium (& Descemet’s membrane): fainter back line

– lens:• opacities scatter & reflect more light - appear white (or pigmented) against gray

background

light source

iris on tangential illumination

outer epithelium of cornea

SLE w/ wide slit on a post-op IOL Pt dx’d w/ Propionobacterium acnes endophthalmitis

SLE thru dilated pupil:

light source

cornea

anterior chamber (AC)

crystalline lensSLE lateral view showing intra-corneal lens anterior to native crystalline lens

• van Herick’s Technique: to assess anterior chamber angle– low mag (6x or 10x) – set beam 600 to side of scope– place narrow slit as close to limbus as possible & perpendicular to the cornea– compare width of cornea seen by optical section w/ the dark section seen btwn front

surface of iris & back of cornea• GRADE 4: ratio of aqueous to cornea is 1:1 - open angle• GRADE 3: ratio of aqueous to cornea is 1:2 - open angle• GRADE 2: ratio of aqueous to cornea is 1:4 - narrow angle• GRADE 1: ratio is < 1:4 - dangerously narrow angle

• Conical beam: used to detect aqueous flare– inflammatory cells in AC (eg acute anterior uveitis)

• room illumination must be completely dark• can only be seen using conical beam of light• set slit-arm angle btwn 450 -- 600

• focus onto front surface of cornea w/ high magnification

– W/ pupil as dark background, flare may be seen btwn focused beam of light on cornea & the out-of-focus beam on lens

• in normal eye this space will be clear

“flare” in anterior chamber (AC)

cornea

iris

                                                                  

                                                      

keratic precipitates

cornea

cells & flarecells & flare corneairis light sourcelight source

cornea

iris

no cells no cells or flareor flare

Indirect Illumination• Evaluate tissue outside directly illuminated area

– reduced glare; easier to view opacities, corneal nerves & limbal vessels• focus on feature directly & then swing lamp to one side

• Retro-illumination (rarely useful in ED!)– light reflected off deeper structures (iris or retina) w/ microscope focused on ant.

structures• study cornea in light reflected from iris; lens in light reflected from retina

– light-opaque features are dark agnst light backgrnd (scars, pigment, vessels containing blood)

• light-scattering features appear lighter than background (e.g. corneal precipitates)

– useful for examining size / density of opacities (not location)– 1) use a parallelepiped beam, focus on retina– 2) direct retro-illumination: observed corneal feature viewed in direct pathway of

reflected light• angle btwn microscope & illuminating arm ~ 60°

– 3) indirect retro-illumination: angle is greatly reduced /increased so feature on cornea is viewed against dark bckgrnd

keratic precipitates (direct & retro-illumination )

“Rust ring” residual from metallic FB

Hypopyon layering in AC

References:• My Hanh Nguyen. Ophthalmology Grand Rounds. Tufts Unviersity.

http://ocw.tufts.edu/Content/37/topics/487903/488024. Content accessed 9/23/08.• Introduction to Slit Lamp Technique. CYBER-SIGHT: Copyright © 2003 Project ORBIS International Inc.

http://www.cybersight.org/bins/content_page.asp?cid=1-1581-1604. Content accessed 9/23/08.• G Papaliodis. Propionibacterium acnes Endophthalmitis. Ocular Immunology and Uveitis Foundation.

Massachusetts Eeye Research and Surgery Institution. Copyright © 1996-2008 C. Stephen Foster M.D. http://www.uveitis.org/medical/articles/case/P_acnes.html. Content accessed 9/23/08.

• Vance Thompson. Postoperative Care for Phakic Intraocular Lens Implants. In: Phakic Intraocular Lenses: Principles and Practice by Hardten, Lindstrom, and Davis. Slack, Inc. www.slackbooks.com/excerpts/66402/66402.asp. Content accessed 9/23/08.

• Jared Schultz. One intracorneal segment treats keratoconus better than two. Copyright 2008 SLACK Inc., www.osnsupersite.com/view.asp?rID=23456. Content accessed 9/23/08.

• Craig Blackwell. Narrated Eye Exam: Copyright 2008. www.blackwelleyesight.com/narrated-eye-exam/. Content accessed 9/23/08.

• Patient Glossary. Ocular Immunology and Uveitis Foundation. Massachusetts Eeye Research and Surgery Institution. Copyright © 1996-2008 C. Stephen Foster M.D. http://www.uveitis.org/patient/glossary/a_f.html. Content accessed 9/23/08.

• JG O'Shea, DA Infeld, RB Harvey. Uveitis- a photoessay. http://medweb.bham.ac.uk/easdec/eyetextbook/Uveitis/uveitis.htm. Content accessed on 9/23/08.

• Second Year 99/00: Clinical Optometry 3. Slit lamp examination: Practical. http://www.academy.org.uk/lectures/eperjesi5.htm. Content accessed 9/23/08.

• KJ Knoop. Slit-lamp exam. Uptodate.com. Last updated: February 12, 2008. http://www.uptodateonline.com/online/content/topic.do?topicKey=ad_proc/2391&selectedTitle=1~61&source=search_result. Content accessed 9/23/08.