Slit Lamp Microscopy Lecture

7/28/2019 Slit Lamp Microscopy Lecture

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Principles Pt 1

SLIT LAMP BIOMICROSCOPY

The EBAA Technician Education Seminar2011

George OD Rosenwasser, MD, CEBTGift of Life Donor Program

Hershey, PA

Slit Lamp Biomicroscopy I

• Overview of the use of the slitlamp in eye banking

• Basic slit lamp anatomy

• Slit lamp designs

• Slit lamp operation

• Eye bank tissue examination

• Advanced techniques• Specular reflection

• Special lighting techniques

The Slit Lamp Exam

• Eye anatomy

• Slit lamp basic• operation

• illumination techniques

• What to look for

amp xamGoal

• Slit Lamp Goal: Does the cadaveric cornea meet eye bankcriteria?

• Determine if the cornea suitable for transplantation

• Assure that corneal donor is anatomically and functionallysuitable, optically clear, and infection-free



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Why do the slit lamp exam?

• To see if there are reasons to exclude the cornea from beingtransplantable

• To determine if the cornea can be used in some applications butnot others

• DSAEK (rim size important)

• PKP (scars, previous refractive surgery may exclude)

• DALK (as in PKP but bad endothelium not an issue)

• Patch Graft (almost any cornea can be ETOH or Glycerinepreserved)

• Slit lamp exams are done to globes orcorneoscleral rims after retrieval in theeye bank

• The specimen needs to be warmed toroom temperature. This preventscondensation on chamber. Do specularexam immediately after.

What, Where and When?

CSVC with IR

thermometer CSVC with Condensation

Whole Globes

• With jar cover off and bottom tilteddownward

Corneoscleral Rims inGlass Scintillation Vials• Cap on, using a 45 degree mirror to

view through the bottom



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Corneoscleral Rims in CSVC’s (Corneal Storage and Viewing Chambers)

• Can view through top optical flat orbottom

So What Do We Look For

Now That We’re There? • Systematically examine the specimen

• Anatomical order• Size of rim

• Clarity/opacity overall

• Conjunctiva

• Epithelium

• Stroma

• Descemet’s

• Endothelium

Atlas of Eye Banking andCorneal Evaluation

http://telemedicine.orbis.org/bins/content_page.asp?cid=1-1581

Anatomy Review

Anterior and Posterior Chamber







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Epithelium

Bowman’s

Stroma

Descemet’s

Endothelium

Corneal Layers: HumanSlit Lamp

Capabilities

• Provides a good, magnified,medium-tech anatomical view

of all corneal layers

• Does not give a functionalview, so metabolic orinfectious status is unknown

Slit Lamp Design

• Horizontal• Zeiss, Topcon, Marco

• Vertical• Haag Streit, Topcon, Marco

• Slit BeamVariability• Height, Width, Focus

• Callibration

• Filters

• Backlighting

Slit Lamp Design•Horizontal• Zeiss, Topcon, Marco



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The Slit Lamp

• Biomicroscope to

examine a living eye

• Parts:• Binocular Microscope

• Produces magnified view of cornea,

with stereopsis

• Converging or Parallel optics

• “Slit” light beam • Intense light, gives cross sectional

illumination

• Fine, delicate optical instrument

Light Source

Microscope

Slit Lamp Styles

• Light source and microscopepivot around same point

• Keeps focus (parfocal)• Light source can be decentered

and used for special illumination• Controls to adjust for slit height

and width• Horizontal or Vertical Slit Beam

Projectors

Slit Lamp Anatomy

Slit Projector

Zeiss and Clones

• Horizontal slit projection system

• Parallel optics

• Four position Galilean telescope tochange magnifications



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Haag Streit and Clones

• Vertical slit projector system withfront surface mirror

• Two or four magnifications

• Converging optics• Older and knock-off models may require

accomodation

Slit Lamp Anatomy

Slit Projector

Holding the Cornea

• Varies by container style• CSVC most common

• Scintillation vial (glass bottle), phenolic cap

• Horizontal• Three finger lab clamp

• Need 90 degree adapter to connect to slit lamp

• Suitable for CSVC

• Vertical• Requires a mirror at 45 degrees

• several commercial and home brew methods



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Glass Scintillation Vial

View the floating/sinkingcornea through the mirror

May need to gently swirl the

cornea to see both sides

Saves the expense of the CSVC

CSVC: Corneal Storage andViewing Chamber

• Gently clamp the fully closed CSVC inthe fingers

• View through optical flats (top isbetter)

Slit Lamp Basics

• Slit Lamp Mechanics• Adjust Oculars

• Par-focality

• Slit adjustment

• Lighting Methods

• Slit Lamp Pathology Just like musicians need to tune

their instruments, we need to

prepare our main instrument

Adjust the Oculars

• Find out if you are slightly near or farsighted and dial this into your oculars• Minus if near sighted, Plus if far sighted

• If there is a reticle, focus based on it

Also adjust the “PD” (pupillary distance)to get full binocular view



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Parallel vs Converging Optics

• Parallel means eyesare focused at infinity

• Converging means astate of near focusing at

all times• important if over forty or

hyperopic (far-sighted)

Converging vs Parallel

Slit Beam Adjustment• Place calibration rod, or a card as a target

• Position slit projector between the oculars• narrow the slit,

• should be in the center

• focus it on the card or rod

• rod is always at the focal plane

• If not, check if you can adjust it or call arepair technician

• Turn the adjustments on the eye pieces oneat time to focus, while the other eye is closed

Calibration Rod

Thin slit should be inperfect focus, adjustoculars to same focalpoint



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Parfocality• Microscope head

• pivots on the same axis as the slit projector

• Both come to focus at the same plane, the focal plane

• When changing the magnification, the focal plane is notchanged

• Slit projector and both eyepieces,

• at all magnifications,

• focus in the same plane

• are parfocal

• If this doesn’t happen with your slit lamp, it requires

adjustment or repair

Parfocal vs Decentered

Parfocal vs Decentered



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Decentration

The Slit ProjectorSlit Beam Adjustment

• When the light beam is wide with no slit, we call theillumination “Broad Beam”

• Two knife edges moving together cause a slit to form,narrowing until the edges meet and occlude the light

• The height of the slit is variable as well



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Slit Beam Height Adjustment

Video Video

• The height of the slit is variable as well

• Different schemes to vary height

• Useful for making measurements

Vertical (Haag-Streit andSimilar)

Turn knob here

Read scale for height here



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Slit Beam Width Adjustment

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Haag-Streit

Width Adjustment

Illumination

• A rheostat (variable resistor) controls thebrightness of the illumination (brighter isbetter!)

Joystick and Lock

• Up-Down

• Right-Left

• Focus In-Focus OutLock



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Slit Lamp Overdrive

• An extra burst of light power isavailable for specular microscopy insome older slit lamps (Zeiss)

The Power Surge Effect

• Overusing high illumination willcause early or immediate bulbfailure

Poor Light Intensity

• Neutral density filters may be in theway, and may need to be switched

off (Haag Streit)



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Know Your Equipment! Slit Lamp Examof the Donor

• Most important exam of donorcornea

• Limited donor history in some

cases

• Detects ocular disease

• Detects previous eye surgery ortrauma

• Duty of technician and surgeon

Whole EyeExamination

• Penlight for in-situ

• Slit Lamp required if enucleation

• Uncap eye jar

• Wet the cornea with sterile BSS

• Tip jar and examine

• Prior to laboratory excision

• Best view of prior surgery

•YAG PI(Laser)

•Surgical PI

Thoughts During Exam

• Transplantable quality?

• Previous surgery may be OK• Refractive Surgery

• RK, AK, PRK, LASIK, TK

•Cataract surgery

• Glaucoma surgery

• Laser iridotomy*

• May save corneal storage media if grosslyunacceptable during whole eye exam

LASIK Donor



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Slit Lamp TrainingTechniques

• Bright illumination, ambient darkness is sometimes essential

• Vary your illumination angles, generally use 350-450

• Swing the illuminator through its full arc (CSI flashlight)

• USE 40x mag for specular reflection

• Posterior illumination

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Illumination -Overview

• Diffuse

• Direct focal

• Specular reflection

• Retroillumination

• Sclerotic scatter• Indirect

• Diffuse PosteriorDiffuse Broad beam Slit beam



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Diffuse Illumination

• Uniform light of large area

• Overview of cornea

• Useful for gross abnormalities

Overview

• Rim Size, Shape

• Foreign Material

• Extraneous anatomical parts



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Contact Lens

Surgical

Peripheral

Iridectomy

Corneal Transplant

Direct Focal Illumination

• Basis for biomicroscopy• Light’s focal point coincides with microscope’s focal point

• Tissue reflects, absorbs, transmits, and scatters light

• Can pinpoint findings in layers

• Parallelpiped (box/curved cube)

• Optic Section (knife like cross section)

Optical Block

• Oblique light incidence gives: “Optical

Block” or “Parallelpiped Prism”

• Narrow “slit” light beam pinpoints

depth and details

parallelpiped

lens

cornea

aqueous flare

Back

Front



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Keratic Precipitates

Specular Reflection

• Means reflection through a mirror

• Look to side of dazzling light tosee endothelium

•

Can see cell outlines & guttata• Can estimate cell count



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Retro-illumination

• Microscope’s focal point andlight’s focal point are are ondifferent spots

• Good for epithelial edema, KP,delicate scars, and bloodvessels

Light focused here

Microscope focused here

Corneal Cap

Removal withLens Implant

and Iris



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2

Sclerotic Scatter

• Use decentered,

focused beam

• Direct at limbus

• Light disperses

• Total Internal reflection

• Good for diffuse scars

Sclerotic Scatter

EKC – EpidemicKeratoconjunctivitis

Foreign Bodies

Sclerotic Scatter:Epithelial Abrasion



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2

Indirect Retroillumination Indirect/ObliqueIllumination

• Elements of sclerotic scatter andretroillumination

Focus medium to narrow beam adjacent to

observation area, e.g., scar

Place light source at wide angle tomicroscope

Broad Beam Illumination



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Radial Keratotomy4-16 incisions Tangential

Thin

SlitAlvarGullstrand

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Slit Lamp Microscopy Lecture

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