Biomicroscopy Tech

7/27/2019 Biomicroscopy Tech

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SLIT-LAMP BIOMICROSCOPY

The slit-lamp biomicroscope is an

important diagnostic instrument for

the examination of the anterior eye

structures as well as the retina.

Being able to proficiently use the

instrument is important. It use

critical in the fitting of contact

lenses.


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THE SLIT-LAMP BIOMICROSCOPE

The instrument is composed of two main components. The slit-lamp is the

light source and the controls to modify the size, shape, direction, color and

intensity of the light.

The biomicroscope is the microscope used to view the eye. The

magnification can be varied.

The accurate term for the instrument is the slit-lamp biomicroscope,however, it is usually called the slit-lamp or the biomicroscope.

Light source

microscope


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Each brand of biomicroscope is slightly different. They have a switch to

turn the light source on. The intensity of the light source can be varied.

The control is often the same dial that turns the light source on or near itdepending on the make of the instrument.


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The slit-lamp biomicroscope can be moved in relation to the

patient using the joy stick for focusing and bringingstructures into view. Other parts of the instrument are the

head and chin rest to hold the patient still and the adjustable

table to hold and adjust the height the instrument for doctor

and patient comfort.

Joy stick to

position instrument

To adjust the

Vertical height

of the instrument

To adjust the heightof the chinrest


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The instrument is designed such that when you use the joystick to move

the instrument towards and away from the patient to focus structureswheel moves on a track. When the instrument moves side to side it

moves along a rod. It can be locked so that one can not move it with the

joystick by tightening down a knob on the rod. It should be locked when

not in use or when moving the instrument.


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The angle between the light source and microscope can be changed by just

moving the arms that hold the light and microscope. They can be locked in

place if desired, however, during the examination the angle between the two

are being changed to obtain the proper views.

Light source and microscope

arms that can be rotated

independently.

Knobs to lock arms in place,

usually used when

biomicroscope in not in use

or being moved.


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Before examining a patient become familiar with the controls.

The width of the light beam can be adjusted by a control on the slit-lamp.

The light beam can also be moved back and forth horizontally. In addition the

light beam can be rotated away from vertical.

Red arrows-slit width control

Green arrows-slit height and filter control


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Different instruments have different controls to

change the magnification. In some cases they alsohave a second set of eyepieces that can be used to

change the magnifications.


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The light beam and the microscope both have to be focused at

the same point. A focusing rod is put in place. The light source,

a narrow beam, is positioned on the rod. This should be at the

click position of the light source. When looking through the

microscope the light source should be in the center of your view

and in focus.


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You must focus the eyepieces for your eyes. With a narrow

beam of light on the focusing rod, look through thebiomicroscope. Looking through only one eyepiece at time,

rotate the eyepiece counter-clockwise until the light beam

appears blurred, then rotate it clockwise until the light beam

just comes into focus.


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PATIENT POSITIONING

Clean the headrest and chin rest with an alcohol swab

before putting the patient behind the instrument.

Some units have paper sheets on the chinrest where a

sheet can be removed between patients.

Before starting the exam the patient must be

comfortably seated behind the instrument with their

chin on the chin rest and head tight against the head

rest. The height of the instrument and chin rest

should be adjusted so the patients eyes are aligned

with the alignment marks on the head rest.

Alignment

mark

Incorrect, the

forehead is not

against theheadrest.


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PATIENT FIXATION

You need to control the patients fixation. The instruments have a

fixation light that can be placed in front of the patient andpositioned so the patient is looking in the desired position. This

may cause the patient to accommodate and converge on the

fixation light causing some discomfort.

Often an easier and quicker way is to have the patient just look at

your ear or a point on the biomicroscope. Then you can just ask

the patient to look down, up, left or right as needed.


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ROUNTINE FOR EXAMINING THE ANTERIOR SEGMENT

In order to be sure you do not miss any anomaly you must getinto the habit of using a set routine. A common order of

examination is:

Lids and lashesConjunctiva and cornea

Instillation of fluorescein and BUT measurement

Eversion of the lids

Anterior chamber and angle measurement

Iris

Crystalline lens

Anterior vitreous


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DIRECT AND DIFFUSE ILLUMINATION

The lids and anterior ocular structures are examined

with the slit lamp beam wide open. This called directillumination. To obtain an even wider view a diffuser

can be placed in front of the light source to give diffuse

illumination.


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LID EXAMINATION

The skin of the lids should be examined for any lumps or bumps

or skin lesions. It is best to start by having the patient close theireyes and scan the lids starting with the upper lid from temporal to

nasal followed by the lower lid. It is important to get in a routine

sequence of examination so you do not miss anything.

Low (7X to 10X) to moderate (10X to 16X) magnification is used

when examining the lids with higher magnifications only used to

study an abnormality. It too high magnification is used you will

miss some abnormalities.


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EXAMINATION OF THE LASHES

The lashes should be examinedfor abnormalities such blepharitis.

With blepharitis there will be

collarettes found at the base of

the lashes.

This photo shows nits (egg

sacs) from lice infestation of

the lashes.


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EXAMINATION OF THE LASHES

The lashes can also be missing. This is called

madaroisis.


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LID MARGINS

After examining the closed lids have the patient open their eyes and

examine the lid margins. You should see the normal structures suchas the meibomian gland openings on both the upper and lower lids.

The puncta (opening for the tears to exit the eye) can be seen at the

nasal side of the lid margin on the upper and lower lids.

Meibomian gland openings puncta


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LID MARGINS

The lid margins should be examined for injection, swelling,

lesions, plugged meibomian glands, chalazion or otheranomalies.

Plugged gland


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EYE MAKE-UP

It is common to see make-up along the lid margins. It can also

be seen in the tear film and may become embedded in the

palpebral conjunctiva. Make-up can create problems with

contact lens wear.


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EXAMINATION OF THE BULBAR CONJUNCTIVA

The conjunctiva visible within the palpebral opening without

pulling the lids back can next be inspected with diffuse

illumination. One should look for injection, dry spots, cysts,pigmentation, pingueculum, pterygium or other anomalies.

Any type of irritation, trauma or infection can cause injection of the

conjunctiva.

Injected conjunctivaNormal conjunctiva


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EXAMINATION OF THE BULBAR CONJUNCTIVA

This photo shows a nevus onthe conjunctiva.

This photo shows a pinquecula,

a raised area on the

conjunctiva that is fairly

common.

EXAMINATION OF THE SUPERIOR AND INFERIOR


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EXAMINATION OF THE SUPERIOR AND INFERIOR

BULBAR CONJUNCTIVA

The superior bulbar conjunctiva isexamined by having the patient

look down and gently pulling the

upper lid up.

The inferior bulbar conjunctiva

can likewise be examined by

having the patient look up and

pulling the lower lid down.


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EXAMINATION OF THE LIMBUS

It is important to examine the limbus, the junction between the

cornea and conjunctiva. A number of normal structures may bevisible including blood vessel loops, nerves, palisades of Vogt and

pigmentation.

A green filter can be used to

better visualize the blood vessels


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This photo shows the Palisades of Vogt which are often visible

with darkly pigmented patients. The palisades are radial

extensions of the sclera towards the cornea at the limbus with

epithelial cells 10 to 12 layers thick between them.


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This photo is of posterior

embryotoxon, an developmental

anomaly where Schwalbes ring

(collagenous tissue between the

end of Descemets membrane

and the trabecular meshwork)

extends further into the cornea

than normal

EXAMINATION OF THE CORNEA WITH


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DIRECT OR DIFFUSE ILLUMINATION

The cornea can be scanned with a wide beam direct or diffuse illumination to

detect anomalies.

Corneal scars, neovascularization, infiltrates, abrasions, foreign bodies and

other conditions can be seen.

Anomalies should not be confused with the reflection of the light source from

the surface of the cornea or from the surface of the crystalline lens.

reflection fromsurface of the cornea

reflection from surface of

the crystalline lens

Corneal scar



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DIRECT OR DIFFUSE ILLUMINATION

Arcus senilis is a build-up of cholesterol and other lipids in the

peripheral cornea. It appears as a whitish or yellowish ring just

inside the limbus. It is found in 60% of patients between 40 and 60

years old and almost all patients over 80.


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EXAMINATION OF THE TEAR FILM

Diffuse or a wide beam direct illumination can also be used to

inspect the tear film. Debris can be seen floating in the tear filmand the debris can increase in dry eye conditions, irritation and

infection.


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Bubbles, also called frothing, can sometimes be seen in the tear

film, especially along the lid margins. This can indicatemeibomianitis.


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Colored interference fringes may also beseen on the tear film over the cornea.

These are visible when the oily layer of the

tear film is thicker than normal.

These are most often seen just above thelower lid margin. By pressing on the

lower lid and forcing the oily material from

the meibomian glands, this will enhance

the fringes.

INSTILLATION OF FLUORESCEIN


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Following a general overview of the visible portion of the anterior

segment and prior to significant manipulation of the lids, fluorescein

should be instilled to measure the break-up time of the tear film(B.U.T.), look for corneal staining, conjunctival staining and papillae.

The method of instilling fluorescein is important. The fluorescein

strip should be moistened with saline solution. Do not touch the tip

of the bottle to the strip. After putting a drop on the strip shake the

excess off prior to instilling it on the eye. You do not want to add

excessive solution t the eye, just the stain.

Correct

Incorrect-do

not touch strip to

bottle


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To instill fluorescein, have the patient look down, rest your wrist on

the patients forehead and grasp the upper lid with the index finger

over the lashes. The patient should not be able to blink. With thepatient still looking down, pull the lid up and gently lay the flat side

of the strip against the conjunctiva. Do not rub the fluorescein strip

across the eye. Gently lift it off and release the lid.

Do not use a dry fluorescein strip or dab the fluorescein strip

against the lower lid as this unnecessarily irritates the patient and

causes reflex tearing.


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Another method of instilling fluorescein is to have the patient look

up and while holding the lids instill the fluorescein on the inferior

conjunctiva.

The fluorescein strip will cause some staining of the conjunctival

which is normal. You should not touch the strip to the cornea as

this will cause the patient discomfort and staining of the cornea.


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FLUORESCEIN STAINING

Fluorescein is a water soluble stain that will stain the tear film and

any disruption of the ocular surface. It will show any breaks in theepithelium and be absorbed by cells which have damaged

membranes.



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Fluorescein staining can be

highlighted by the use of filters.

The biomicroscope has a cobalt(blue) filter that can be placed in

the light beam. The blue filter

enhances the visibility of the

stain.

The visibility of the staining can

be further enhanced by placing a

yellow filter (ie. a Wratten #12 or

Tiffin #2) over the objective of the

biomicroscope.

The top photo shows a filter being

placed over the objective. The

bottom photo shows some

different filters that can be used.



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The yellow filter filters out the

blue light to give better

visualization of the greenfluorescence of the fluorescein.

The top photo is with the yellow

filter in place.


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MEASURING THE TEAR FILM BREAK-UP TIME

The time it takes for the tear film to break-up following a blink is an

indication of the quality of the tear film. Immediately following theinstillation of fluorescein the B.U.T. should be measured. The room

lights should be out and filters in place. The patient is asked to blink

3 or 4 times and then to look straight ahead and not blink. The time

in seconds from the last blink until a dark spot or streak develops in

the tear film is the B.U.T. Do not hold the lids open.

TEAR FILM


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TEAR FILM

In addition to the light green staining of the tear film seen over the

corneal surface, the tears in the tear meniscus (also termed tearprism, lacrimal lake, or tear strip) along the lid margins is easily

seen. With dry eyes this tear meniscus is decreased in size and

may be essentially absent in places.

CORNEAL STAINING


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CORNEAL STAINING

If only the superficial epithelial cells are damaged, the

fluorescein staining will be limited to the area of damage. If the

full thickness of the epithelium is damaged, fluorescein will seepinto the stroma giving a larger area of staining. The borders will

not be as distinct since the fluorescein is slowly diffusing

through the stroma.

CORNEAL STAINING


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CORNEAL STAINING

Rubbing the cornea through the eyelid can cause an epithelial

mosaic staining pattern (Schweitzers Lines). This lasts only afew minutes.

CONJUNCTIVAL STAINING


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CONJUNCTIVAL STAINING

Using the wide beam or diffuse illumination and the filters, the

conjunctiva should be examined for staining. It is normal to haveareas of pooling of fluorescein, especially in older patients where

the conjunctiva is looser and more wrinkled.

Fluorescein pooling in

folds of the conjunctiva Spots of staining from drying

ROSE BENGAL STAINING


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ROSE BENGAL STAINING

Rose bengal stain is used to stain dead or degenerating cells as

well as mucous. It is used to show staining with dry eye patients.

It is supplied on strips like fluorescein or as a solution. Only asmall amount of stain is required. If too much is used it will be

uncomfortable. One must be careful as it will stain clothing and is

not as easily washed out as fluorescein. Another stain which

stains similar cells as rose bengal but is more comfortable is

lassime green.

PALPEBRAL CONJUNCTIVA EXAMINATION


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It is important to evert the upper lid and examine the palpebral

conjunctiva for papillae, cysts, concretions, foreign bodies,irritation and other anomalies. With the patient in the head rest,

have the patient look down and grasp the upper lid margin over

the lashes. With a cotton-tipped applicator or other stylus placed

at the upper lid sulcus (the fold in the upper lid) and lift the lid up

and evert it over the stylus.

HOLDING THE EVERTED LID FOR EXAMINATION


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HOLDING THE EVERTED LID FOR EXAMINATION

Hold the lid in the everted

position with your thumb and

examine the palpebral

conjunctiva with the

biomicroscope.



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The upper conjunctiva should be

smooth and not injected. A common

problem with contact lens wear is thedevelopment of papillae (raised areas

of inflammatory tissue). Each

papillae has a central blood vessel

stalk. With fluorescein it is easier to

detect the papillae.



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The lower conjunctiva should also be examined. Just pull down

the lid. Look for cysts, follicles, embedded make-up, concretions

or other anomalies.

concretionEmbedded make-up

CORNEAL EXAMINATION-SCLEROTIC SCATTER


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CORNEAL EXAMINATION SCLEROTIC SCATTER

An illumination called sclerotic

scatter is useful in detectingcentral corneal clouding (corneal

edema) created with rigid contact

lenses and other corneal opacities

such as scars, foreign bodies and

abrasions.

A light beam about 2 to 4 mm wide

is focused on the temporal limbus.

The light source should be rotated

such that it is off to the side of the

viewing area (the microscopefocused on the center of the

cornea and the light source on the

limbus). When properly set up the

limbus 180 degrees from the light

beam will glow.

PARALLELEPIPED


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PARALLELEPIPED

One of the most useful illuminations is the parallelepiped. This is a

relatively wide beam of light that illuminates a block of the cornea.

The microscope is directly in front of the patients cornea and the

light source is approximately 45 degrees from the straight ahead

position. Low to moderate magnification can be used to scan the

cornea with high magnification used to examine structures in

detail.

Width of beam

(front surface of cornea)

Back surface of the

cornea

Light reflected

off of the iris

CORNEAL EXAMINATION WITH THE PARALLELEPIPED


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The corneal should be scanned with a parallelepiped as it is the

illumination that is used to detect and examine corneal structures

and defects.

Corneal nerve seen with

a wide parallepiped.

Pigment on the back of

the cornea seen with a

more narrow beam.

A corneal scar seen with

a relatively wide beam



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The parallelepiped can be used to detect corneal striae that

develop when corneal edema occurs with hydrogel lens wear, in

keratoconus and normally in some older patients.

They are seen as small, usually vertical, white lines deep in the

corneal stroma. They are best seen with high magnification. With

greater amounts of edema folds develop in the same area which

appear as dark lines.

striae

fold

CORNEAL EXAMINATION WITH THE OPTIC SECTION


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When scars, abrasions or other

anomalies are detected one often

wants to know how deep they go intothe cornea. This is when an optic

section is used. The optic section is

a very thin parallelepiped and

optically cuts a very thin slice of the

cornea. The distance from the front

and back of the section gives you the

location within the cornea.

The epithelium (front surface of the

cornea) gives a bright reflection. With

high magnification a speckle patter isseen within the normal stroma. The

back of the optic section is the

endothelium.

Front of cornea Back of cornea



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The top photo shows a corneal scar

with a wide beam of illumination.

The bottom photo shows an opticalsection through the scar indicating

the depth within the cornea-in this

case very superficial.

MEASURING THE SIZE OF DETAILS


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MEASURING THE SIZE OF DETAILS

It is important in following and

documenting conditions to accurately

measure them. The width or height of a

structure can be measured by using a spotof known diameter or a parallelepiped of

known width. Biomicroscope have a scale

on the light source that indicates the width

of the beam. They also have apertures of

different diameters that can be used.

It is also possible to have a reticule in the

eyepiece to make the measurement,

however, most biomicroscopes do not have

such a reticule.

MEASURING THE MOVMENT OF A CONTACT LENS


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MEASURING THE MOVMENT OF A CONTACT LENS

The amount of movement of a lens can be estimated by using a

spot of light of known size. For example with a soft lens, a spotsize of 0.2 mm to 1 mm can be used. The amount of movement of

the lens edge with a blink in relation to the spot size can be

determined.

RETRO AND INDIRECT ILLUMINATION


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Many corneal defects are not easily seen

with direct illumination. Such things as

microcystic edema, microcysts andneovascularization are examples.

Retro-illumination is where a relatively

narrow beam (1-3 mm) is reflected off

the iris and the object of interest isviewed against the bright iris. If the

object is opaque it will appear dark.

Indirect is similar except you view the

area of the cornea next to the light beamhits the cornea and not against the

reflection from the iris. In practice both

are used more or less similtaneously.



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These photos show an foreign

body in direct illumination (top)

and indirect illumination (bottom)



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This photo shows microcystic

edema and vacuoles from

wearing a thick hydrogel contact

lens in retro illumination.

RETRO-ILLUMINATION


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Neovascularization (new vessel growth) near the limbus is

often difficult to visualize. Retro-illumination makes thevessels easier to see.

RETRO ILLUMINATION

RETRO-ILLUMINATION


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This photo shows epithelialmicrocysts (small dots) in the

corneal epithelium from the

wearing of an extended wear soft

contact lens. It is often easiest to

detect such small defects alongthe edge of the retro-illumination,

this is sometimes termed

marginal retro-illumination.

RETRO ILLUMINATION

RETRO-ILLUMINATION


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When the pupil is dilated, retro-illumination, can give a red reflex

against which corneal defects can be seen. The beam is passed

through the periphery of the pupil to obtain this view. This photoshows an area of localized edema.

RETRO ILLUMINATION

SPECULAR REFLECTION


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SPECULAR REFLECTION

Specular reflection is when the angle

between the light source and microscope

is such that a specular reflection isobtained from the cornea.

A bright reflection is obtained from the

surface of the cornea and a less bright

reflection form the posterior surface ofthe cornea. This illumination is obtained

by using a narrow parallelepiped and

placing the microscope directly in front of

the patients eye with the light source

approximately 45 degrees to the side.

The angle of the light should be moved

until a very bright reflection is obtained

from the corneal surface.

SPECULAR REFLECTION


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SPECULAR REFLECTION

Specular reflection is mainly used to

view the endothelium, the single layer

of cells on the back surface of thecornea. The highest magnification

available should be used. To view this

layer look just to the side of the bright

reflection from the font surface of the

cornea. If the parllelepiped is too wide

you will not be able to see the

endothelium. To view different areas

of the cornea have the patient change

their gaze as well as you changing the

angle of the microscope and light

source.

The endothelium will appear as a fine,

rough surface due to the individual

endothelial cells.

endothelium

reflection from the

front surface

SPECULAR REFLECTION


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SPECULAR REFLECTION

Endothelium guttata, polymegethism (variation in size of the

cells) and dystrophies may be detected and studied with

specular reflection.

guttata

USING THE BIOMICROSCOPE TO MEASURE ANGLES


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The biomicroscope can be used to measure rotation, for example

the rotation of soft toric contact lenses.

To measure the rotation of a lens, locate the mark indicating thebase of the prism or horizontal marks on the lens. Using a narrow

parallelepiped, adjust the height of the instrument such that the

center of the beam is approximately in the center of the pupil.

Rotate the beam until it goes through the mark on the lens and the

center of the pupil. The amount of rotation can be read from thescale on the slit-lamp.

lens with mark at base

rotating nasallylens with markings in

horizontal plane rotating

scale on the slit-lamp

showing degrees of

rotation

BIOMCROSCOPY TECHNIQUE


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BIOMCROSCOPY TECHNIQUE

You should practice using the biomicroscope until you are

proficient at using the controls and can do an examination of theanterior surface of the eye in an efficient and smooth manner.

Biomicroscopy Tech

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