Indra P Sharma

B.Optom, M.Optom

The magnified tour of the eye with

SLIT-LAMP

BIOMICROSCOPE

Here comes your slit lamp...

...and with it comes your

RESPONSIBILITY

Background

The name

SLIT : A narrow slit beam of very bright light

LAMP : produced by a lamp (illumination

system)

BIO : to view the biological structure (of

eye)

MICROSCOPE : under magnification with a

microscope

Overview

Instrument uniquely designed to give a magnified three dimensional view of the eye and its structuresfor quantitative measurements for documentation.

Because the slit lamp provides a binocular view, the location of abnormalities can be determined with great precision.

The instrument combines variable magnification with controlled illumination.

In simple, to make a magnified tour of the eye.

The History Mystery

History Mystery

Alivar Gullstrand (5 June 1862 – 28 July 1930)

Nobel prize in Medicine and

Physiology (1911) for developing

slit lamp biomicroscope.

Vogt (1919) : Specular

Microscopy

Various modification by Kohler,

Goldmann,

Large reflection free

ophthalmoscope

Manufactured by Zeiss in 1911

Illuminator with Nernst glower

Haag-streit (1920) Bausch and Lomb slit lamp(1926)

Haag-streit 1933 and 1936

Modern Day

The types

1. According to brands

(Company)

According to Brand (company)

Haag-streit

Topcon

Zeiss

2.Illumination types

Horizontal prism reflected light source

Vertical illumination source

3.According to Magnification

exchanger

Grenough type Galilean type

The Optics

Optics

It works on the same principle as a compoundmicroscope.

The objective lens (+22 D) is towards the patient,whose eye forms the object. The objective lensconsists of two planoconvex lenses with theirconvexities facing towards each other.

The eyepiece is +10 to +14 D and is towards theexaminer.

The illuminating system can be adjusted to vary the width, height and angle of incidence of the light beam.

The working principle

Optics

Parfocality : the focus of the slit and the focus

of the microscope are at the same point.

The Parts

Fixation target

Chin rest

adjustment

knob

Joystick

Power switch

Table height

adjustment

Forehead

band

Canthus

alignment

Chin rest

Hand grip

for patients

Lock for slit

lamp base

Low friction plate

Scale for slit

height

Slit height

control

Inclined mirror

Latch to tilt

light column

Light source

Filter control

Centering

screw

Slit width

conrol

Parts of Slit-lamp

1. Illumination system

2. Observation system

3. Mechanical system

1. Observation system

– binocular eyepieces

– camera/video adaptor

– observation tube (demonstration slitlamps)

– magnification changer

2. Illumination system

lamp housing unit

slit width and height control

neutral density filter

cobalt blue light

red-free (green) filter

field size control

diffuser

prism.

3. Mechanical system

Motorized table (Base)

Patient positioning frame

Joystick

forehead rest

chin rest

fixation target

power supply unit

locking controls.

Magnification ranges

Low magnification: 7X - 10X : general eye(Lids, bulbarconjunctiva/sclera,cornea/limbus,tears, anteriorchamber/iris/crystalline lens)

Medium magnification: 20X - 25X : structure of individual layers.

(Epithelium/epithelial breakdown, Stroma, Endothelium, contact lens fit/lens condition)

High magnification: 30X - 40X : details.

(epithelial changes, stromal striae, folds, endothelial folds, polymegethism)

Illumination System: Features

1. Variable light intensity

– low

– medium

– high.

2. Filters

– cobalt blue light

– red-free (green)

– neutral density filter.

3. Width

– optic section

– parallelepiped of Vogt

narrow beam

broad beam

– conical beam.

4. Height

– adjustable slit height

5. Angle

– variable angle formed with the observation

system

– rotation of the prism or mirror enables

observation with an alternate illumination

technique (especially an indirect method).

Controls

Slit width control knob Slit height control knob

The examination procedure

What the Patient Needs to

Know

Instruction to patients:

This instrument is a microscope used to magnify the structures of the eye.

Please keep your chin in the cup with your teeth together and your forehead against the bar. Try not to lean back. The microscope comes close to your facebut will not touch your eye.

Sometimes the light is bright. Unless specifically told not to, you may blink at any time.

Try to keep both eyes open.

This is just a light, not a laser or a camera.

How to start?

Focus the eye piece

Adjust the headrest

Position the fixation target

Decrease the room illumination

Start with diffuse illumination

Order of Examination

Tears

Lid margins/Lashes

Conjunctiva

Cornea

Anterior chamber

Iris

Lens

Anterior vitreous

What is wrong?

Keypoints

Patient education is an important aspect of the slit lamp

exam.

A comfortable patient is a more cooperative patient.

Before beginning, adjust the ocular power and pupillary

distance

(PD).

Using lower voltage settings preserves bulb life.

Manipulate the microscope with one hand on the light

source

and the other hand on the joystick.

Developing and following an examination protocol will help

ensure quality patient care.

Accurate, legible documentation is the last step of any slit

The illumination technique

Illumination Techniques

1. Diffuse.

2. Direct.

3. Indirect.

4. Retro-illumination.

5. Specular reflection.

6. Sclerotic scatter.

7. Tangential.

1. DIFUSE ILLUMINATION

• 45 degree angle between light and

microscope

• Fully open slit

• Diffusing filter

• Variable magnification (low to high)

Overall view of:

Lids and lashes.

Conjunctiva.

Cornea.

Sclera.

Iris.

Pupil.

2. Direct Illumination

Observation and illumination systems are

focused

at the same point.

Vary angle of

illumination

Low to high

magnification

Vary width and height

of light source

2.1 Optic Section: Slit width 1mm or less

Illumination angle 45-60° or more

High illumination & magnification

Application:

Corneal depth, layers, scars, vessels, Lens opacity

2.2 Parallelepiped: wider beam

Slit width 2-4 mm obliquely focusing

quadrilateral block of light illuminate the

cornea Application

To examine corneal epithelial,

stroma

To ascertain depth (FB, abrasion),

breakdown, lens surface and endothelium.

2.3 Conical Beam: Narrow, short & bright slit of light

45°-60° light source directed to pupil

Magnification 16x-25x

Application :

Inflammatory cells, flare, pigmented cells, metabolic

wastes

Assessment of particles floating in the A/C

3.Indirect Illumination

Observation and illumination systems are not

focused at the same point.

Focal light beam is directed adjacent to the

area of observation. Vary angle of illumination

Slit beam is offset

Vary beam width

Low to high magnification

Valuable for observing:

Iris pathology.

Epithelial vesicles.

Epithelial erosions.

Iris sphincter.

4.Retro-illumination

Object of interest is illuminated by light

reflected

from the structures behind it. Vary angle of illumination

Moderately wide beam

Slit beam is offset

Medium to high magnification

Reflected light from iris or

fundus

Valuable for observing: Vascularization.

Epithelial oedema.

Microcysts.

Vacuoles.

Dystrophies.

Crystalline lens opacities.

Contact lens deposits.

5. Specular Reflection

Angle of incidence = angle of reflection

Slit width < 4mm

Magnification 35x

Best view with one eye

Application :

Assessment of surfaces

Corneal epithelium

Corneal endothelium

Lens surface

Assessment of tear film

6. Sclerotic scatter

Light incident on the limbus with 2-4mm slit at

an angle of 45° - 60°

The microscope focused centrally

Total internal reflection of the incoming light at

inner corneal boundaries (endothelium and

epithelium)

Applications

Scars, foreign bodies, corneal

defects

Irregularities in the cornea

Localized epithelial oedema.

7. Tangential

A narrow light beam is projected almost

parallel along the structure to be observed

Elevated structures are visible by shadowing

Illumination angle 70-90°

Magnification 10-25x

Application :

Elevated abnormities or changes in the iris

Tumors, cysts

Key Points

An appreciation of what is normal is necessary

before one can identify that which is abnormal.

Documenting that a structure is normal is just

as important as notating irregularities.

There are variations of normal that you will

learn as you continue to examine eyes with

the slit lamp.

The accessories

Filters

a) Open aperture

b) Heat absorption screen: decreases patient discomfort

c) Grey filter: decreases maximum brightness for photosensitive patients

d) Red free filter- enhances blood vessel and haemorrhage

e) Empty space for extra filter

Cobalt blue filter

Enhance fluorescein stain

Associated instrument

Goldmann applanation tonometry

Lenses

Laser delivery system

Slit lamp is the an important instrument for an

eye health personnel (treat it as an asset)

User level care & maintenance is very much

important to get optimum performance & long

life from it.

An careful eye examination can make a

difference in someones life.

Slit lamp examination is an artof

science.....Practice, practice practice

6/17/2017

indrapsharma@gmail.com

optomindra.blogspot.in6/17/2017