Glaucoma testing tests

TESTS IN GLAUCOMA

When Glaucoma is suspected or diagnosed, a
variety of tests are used to determine the extent of
the disease. Visual field is probably most
commonly used tool. Some tests are only helpful
in evaluating the type of glaucoma such
Gonioscopy. Here are some of the common tests
used in glaucoma evaluation.

Visual fields
Nerve Fiber Layer Analyzer
Pachymetry
Gonioscopy
Disc Photos
Fluorescein Angiography ( only in
neovascular glaucoma to find the cause)

EXAMPLES OF VISUAL FIELDS IN GLAUCOMA

A normal looking visual field
There are no dense scotomas
or blind spots on this test

A superior field defect,
most probably caused by
glaucoma in suspected or
diagnosed case. Optic
nerve appearance should
co-relate with this field

Superior and inferior
defects. This case is more
advanced and may need
aggressive approach to
save the remaining tunnel
vision

This field shows very
advanced case, almost
end stage. Some cases
may continue to reach
stage like this despite
treatment

PERIMETER OR

VISUAL FIELD ANALYZER

Visual field testing or simply side vision

testing is done in medicine in numerous

conditions, such as neurology and brain

disorders but in ophthalmology this test is

used most in the diagnosis and

management of glaucoma. There are

numerous manufacturers out there

producing excellent pieces of equipment

but Humphrey Field Analyzer is probably

most used machine in the US.

This test can be done in several modes

such as screening but a threshold test is

more desirable since it does more in depth

analysis but also takes more time. Even a

threshold test does not pick up very early

damage from glaucoma.

The visual field test is used to assess any

damage to peripheral vision and if any

defect is found then rest is repeated

periodically to see if the progression of

glaucoma has been arrested. If a

subsequent test shows worsening of the

field defect, then more aggressive

treatment may be needed.

HUMPHREY FIELD
ANALYZER

GONIOSCOPY

Gonioscopy is evaluation of the drainage angle of the eye and is done in

the office by the examining physician using the slit lamp and a contact lens

generally called gonioprism.

In Glaucoma cases it is important to know the anatomical structure of the

eye, specially the draining area, space between Iris and the Cornea. This

area or the angle as it is called should be adequately open to allow free

flow of Aqueous Humor or fluid inside the eye. In some cases this space

may be narrow or shallow and flow of Aqueous Humor may be impeded.

Sometimes a small opening in the Iris using a laser may be necessary to

keep the angle open.

The angle is also evaluated for other factors which can effect the pressure

in the eye, such as synechia ( scarring and adhesions), pigment on the

surface of the Trabecular

Mesh work

( blocking the drainage) or presence

of blood vessels ( a key factor in neovascular type of glaucoma

)

SLIT LAMP AND GONIOPRISM

DIAGRAM OF AN EYE WITH ANGLE
( SPACE BETWEEN CORNEA AND IRIS ) WIDE
OPEN AND FLUID SHOULD FLOW FREELY
ON THE RIGHT ANGLE IS VERY NARROW OR
ALMOST CLOSED

PHOTOGRAPH OF A VERY
NARROW ANGLE

EYE TREATED WITH IRIDOTOMY
( SMALL OPENING IN THE IRIS ) BY
A LASER TO FACILITATE FLUID
CIRCULATION

PHOTOGRAPHY OF THE OPTIC NERVE HEAD

( DISC PHOTOGRAPHS)

SERIAL PHOTOGRAPHS OF THE OPTIC NERVE HEAD ARE

VERY VALUABLE TOOL IN THE MANAGEMENT OF

GLAUCOMA.

VERY SMALL CHANGES IN THE CENTRAL CUP OR

CHANGES IN THE NERVE FIBER BUNDLES OR EVEN SMALL

HEMORRHAGES COULD EASILY BE MISSED BY NAKED

HUMAN EYE BY WHEN SERIAL PHOTOGRAPHS ARE

COMPARED, SUCH MINUTE CHANGES CAN BE PICKED UP

AND TREATMENT COULD BE ADJUSTED ACCORDINGLY

SOME EXAMPLES OF
THE OPTIC NERVE
CHANGES OVER TIME
IN GLAUCOMA

PACHYMETRY

Pachymetry is measurement of corneal thickness and is done

using an

ultrasound machine called "Pachymeter". Thickness of the

cornea can

effect the

intra ocular

pressure

measurement and

therefore it is

usually

checked in the beginning

and p

ressure readings are

adjusted

accordingly.

Since the corneal thickness does not change through out life, unless

person had a refractive surgery like LASIK, test is done only

once.

NERVE FIBER LAYER ANALYZERS

GDX AND OCT

In the treatment or suspected cases of glaucoma a very common test

is used to look at health of the optic nerve. Optic nerve is a little over a

millimeter in thickness and conveys images from the retina to the brain.

Though very small in diameter, the optic nerve has over a million

fibers packed inside it.

These instruments, Optic Nerve Fiber Analyzers, use scanning laser

technology to look at the thickness and health of these nerve fibers.

These instruments are very precise and are extremely valuable in the

management of glaucoma. Tests may be repeated periodically to

assess status of the optic nerves and progression of the disease.

There are several different instruments of this kind available today.

Our office uses two of them, GDX and OCT, which are almost a

standard today in the management of glaucoma.

GDX

GDx Nerve Fiber Analyzer is a scanning laser system that detects early

glaucoma

by measuring the thickness of the retinal nerve fiber layer.

GDX has a database containing bilateral retinal-verve fiber

measurements on

hundreds of normal subjects. The database compares patients' scans

with normals matched for age, race and gender and generates a color

printout of the results.

The GDx is capable of identifying early damage to the optic nerves and in

such cases treatment can be started before patients have visual field

loss from glaucoma. Test is done when glaucoma is suspected and

periodically repeated to see if the progression has been stopped.

A look at GDX report
Left side shows
extensive nerve
fiber layer loss,
right side is normal.

Moderate nerve fiber loss on GDX and
associated loss of peripheral vision

Examples of normal vision and
gradually constricting visual
fields in glaucoma. Under the
photos are corresponding GDx
scans

St. Louis STL

EYE CENTER of MISSOURI

3535 S. Jefferson, Suite S-4
Saint Louis, MO 63118
Phone 314-771-3000