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 pressure 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