ed slit-lamp examination andrew shannon, md mph department of emergency medicine jacobi medical...
Post on 31-Mar-2015
222 Views
Preview:
TRANSCRIPT
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.
top related