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146 Theory and Practice of Squint and Orthoptics
disparity gives rise to the perception of
stereopsis of the dissimilar portions (Fig. 6.37C).
Uses of synoptophore
Diagnostic uses
1. Measurement of the objective and subjective
angles of deviation (see page 118).
2. Measurement of the primary and secondary
deviations.
3. Measurement of deviation in cardinal
directions of gaze.
4. Measurement of interpupillary distance (IPD)
5. To investigate the state of retinal correspondence (see page 137).
6. Estimation of grades of binocular vision
(see page 61).
7. To estimate presence and type of suppression
(see page 180).
8. Measurement of range of fusion or vergence
(see page 123).
9. Measurement of angle kappa.
Therapeutic uses
It is used in the treatment of:
1. Suppression (see page 185).
2. Abnormal retinal correspondence.
3. Eccentric fixation.
4. Accommodative esotropia (dissociation
training).
5. Heterophorias and intermittent heterotropias
(improvement of fusional amplitude).
Measurement of anlge kappa with synoptophore
To measure the angle kappa with synoptophore,
a special slide is placed in front of the eye under
observation. This slide consists of a row of
numbers and letters (4 3 2 1 0 A B C D) and
animal pictures (for small children and illiterate
patients) placed at 1° intervals (Fig. 6.38). The
patient is asked to focus on the ‘0’ mark while
the examiner looks for the corneal reflex. If the
corneal reflex is on the nasal side of centre of
pupil, the angle is positive; if it is on the temporal
side, it is negative. The patient is then asked to
look in turn either one letter or one number until
the reflex is centred. The degree of deviation
corresponding to the letter or number is then
recorded. For example, if the left eye is being
tested and the corneal reflex is centred, when
the patient looks at the number 3, the patient
has 3° negative angle kappa in the left eye.
Measurement of interpupillary
distance with synoptophore
To measure the IPD, arms of the synoptophore
are placed at zero and the patient is instructed
to look at the centre of the picture in the right
hand tube with his/her right eye. The examiner,
with his right eye closed, aligns the central white
line which is on the mirror unit of the tube, with
the reflection of the light on the centre of the
patient’s pupil. The same procedure is repeated
with the patient fixing with the left eye and the
examiner closing his right eye. The IPD is then
read on the millimetre scale.
Digital synoptophore
Digital synoptophore, introduced recently, is
likely to soon replace the currently used electric
synoptophore for sensory and motor assessment
of strabismus patients as well as measurement
of the angle of deviation.
Features of digital synoptophore
Digital Synoptophore (Fig. 6.39) comprising of
a computer controlled display device consists
of both hardware and software components:
Fig. 6.38 Synoptophore slide for measurement of angle kappa.
Fig. 6.39 Hardware component of digital synoptophore
147Evaluation of a Case of Strabismus and Orthoptic Instruments
Hardware component consists of various
subunits as described below:
• Computer system with colour monitor.
• Screen divider. An opaque vertical screen
divider, to divide the display screen into 2
equal right and left halves.
• Input device to move the generated screen
targets, such as mouse, trackball, etc.
• Two tubes to carry the images from the display
screen to each eye separately which contain a
lens system and eyepieces assembly with
adjustable interpupillary distance.
• Adjustable chin-rest and head-rest for stabilizing
the patients head.
Software component consists of various
computer programs designed for various
orthoptic tests.
Procedure
Before examination, the interpupillary distance
(IPD) for the patient must be first measured in
millimetres. The distance between the eyepieces
is then set according to this measurement. The
patient places his chin on the chin-rest and his
forehead against the headrest. The chin-rest is
adjusted in such a way that the eye level is at
the centre of screen vertically.
Uses
It is used to perform the following tests on
patients with strabismus:
• Simultaneous perception (foveal, macular and
paramacular)
• Fusion
• Stereopsis
• Assessing retinal correspondence
• After image testing
• Measure the angle of deviation
• Orthoptic exercises
LIVINGSTON BINOCULAR GAUGE
Livingston binocular gauge (Fig. 6.40) is an
apparatus used for the measurement of
convergence and accommodation. Basically, it
consists of a 36 cm long wooden ruler marked
in centimetres and half-centimetres. In the
Fig. 6.40 Livingston binocular gauge.
148 Theory and Practice of Squint and Orthoptics
centre of this ruler, from 6 cm mark to 21 cm
mark, there is a slot into which is present a
slidable convergence rod (white vertical rod, the
centre third of which is painted black). One end
of this ruler is so designed that when in position,
it straddles the patient's nose and rests upon
his/her cheek bones. At this facial end of the
ruler, a detachable occluder is attached which
can be used to occlude either eye while
measuring uniocular accommodation. In this
position, the markings on the ruler indicate
distance from the anterior surface of cornea. At
the other end of the ruler, there is a box-like
attachment which can slide towards the eye.
This box-shaped attachment is 6 cm wide and
has a cross-like opening (cut in the surface facing
the patient) through which the back surface of
the box consisting of a white rectangular card
with a central black vertical line (opposite the
vertical limb of the cross-opening) is seen. The
black vertical line is used for measuring the
convergence. On either side of the black vertical
line, there are three black horizontally placed
letters—ALT, opposite the horizontal limb of the
cross-opening. These letters are used for
measuring accommodation.
Uses of livingston binocular gauge
1. Measurement of objective convergence. The
ruler is fitted on the patient's cheek bone. The
convergence rod is kept farthest from the patient,
who is asked to continuously look at the central
black section of the rod which is moved steadily
towards the patient's eyes. The examiner notes
the scale reading, where the patient's one or both
eyes diverge on the loss of binocular fixation.
Normally, the objective convergence varies
between 6 and 10 cm in young adults.
2. Measurement of subjective convergence. After
fitting the ruler on the patient's face, the central
convergence rod is removed and the box-like
attachment is kept farthest from the patient. The
patient is asked to look at the black vertical line
placed in the centre of vertical limb of crossopening while the box is slid towards the
patient's face. The point where the patient
observes that the line has moved slightly to the
right or to the left or has become double is noted
on the scale. This reading gives the measure-
ment of subjective convergence. The normal
value of subjective convergence is less than
20 cm, but is almost invariably greater than that
of objective convergence.
3. Measurement of accommodation. The instru-
ment is used in the same way as used for
measuring subjective convergence; except that
now the patient is asked to look at the letters
placed corresponding to the horizontal limb of
the cross opening of the box-like attachment. The
point where the patient reports blurring of the
letters gives the reading of his/her near point
(punctum proximum).
VISUSCOPE
It is an instrument similar to ophthalmoscope
(Fig. 6.41) which is used to examine the fixation
pattern of patients during monocular vision. It
was designed by Cupper. With the help of this
instrument, examiner projects a disc with a
green filter having a star in the centre and
surrounded by concentric rings on to the
patient's fundus. The distance between the
concentric rings is ½o. The patient is asked to
look into the star after occluding the eye not
being examined. Normally, the foveolar reflex
of the patient coincides with the star if the
fixation is central. In the presence of eccentric
fixation, the star, will not coincide with the
foveolar reflex and can be anywhere on either
the nasal or temporal retina or above or below
the fovea (Fig. 6.20). The degree of eccentricity
may be known from the concentric ring with
which the star coincides.
Fig. 6.41 Examination of fixation pattern with visuscope.
149Evaluation of a Case of Strabismus and Orthoptic Instruments
EUTHYSCOPE
Euthyscope is a modified form of ophthalmoscope (Fig. 6.41) which is used in pleoptics
for the re-education of the fovea that has lost
its principal visual direction in eccentric
fixation.
This instrument projects an approximately 30
wide beam of light in the centre of which an
opaque 3° or 5° disc can be moved to cause a
black dot. This serves to shield the fovea during
the exposure of the surrounding retina. Since
the light intensity used is moderate, the
peripheral retina is not dazzled but only
stimulated enough to produce an after image.
A green filter disc enables the examiner to locate
the fovea without dazzling the patient's retina.
Since pleoptic treatment is now obsolete, so this
instrument is also not used in the modern
orthoptic clinics.
DIPLOSCOPE
The diploscope consists of a 25 cm long metal
shaft supported by a handle having face-piece
at one end and a card holder at the other end.
Depending upon the model, the face-piece can
rest on the nose (Fig. 6.42), the cheek bones, or
the upper lid. The card holder contains a card
with white background. On this card are printed
letters DOG, with a green square placed
centrally above the O and a red square centrally
below the O. About 6.5 cm in front and parallel
to the card holder is mounted a metal septum
which is perforated by four holes, each 8 mm in
diameter. The two holes are situated horizontally 15 mm apart from each other and at an
equal distance from the centre of the septum.
The other two holes situated vertically, one
below the horizontal left-hand hole and other
above the horizontal right-hand hole.
When in use, the septum dissociates the two
eyes in such a way that each eye can see only
o
two of the three letters on the white card and
only one of the two-coloured squares. The left
eye sees the letters OG and the lower red square,
while the right eye sees the letters DO and upper
green square (Fig. 6.43).
Uses
1. Suppression and the presence or lack of
binocular vision can be detected. With normal
retinal correspondence and bifoveal fixation,
when the two images of O are fused, the patient
will see three holes with the word DOG in them
(Fig. 6.43).
2. The main use of the instrument is to exercise
for relative convergence, when binocular
single vision is present. To perform exercise,
patient is asked to move his/her eyes in
relation to septum and card at four different
positions (described below). As the patient
does so, he/she sees a change in the relative
position of the letters and colours as perceived
by each eye simultaneously. This movement
of letters into a definite pattern is utilized in
training the patient to appreciate and control
the position to which his/her eyes are
directed. Thus, it teaches the patient to switch
easily from distant to near fixation and vice
versa improving the fusional amplitudes
which are essential for a comfortable binocular
single vision.
Fig. 6.42 Diploscope.
Procedure
The four positions of fixation and the various
kinds of physiological diplopia, when practising
with the diploscope, are as follows (Fig. 6.43).
Position 1. The point of fixation is central letter
O on the card. In this position, letter D falls on a
point temporal to the fovea in the right eye and
is projected to the left of O, while G falls on point
temporal to the fovea in the left eye and is
projected to the right of O. Thus, the letters DO
are seen with the right eye and the letters OG
150 Theory and Practice of Squint and Orthoptics
Left eye Right eye
Fig. 6.43 Principle of diploscope and observations made by the patient while in use at positions 1, 2, 3 and 4 (for explanation,
see text).
with the left eye and in the presence of binocular
single vision patient will perceive three holes
with the word DOG in them.
Position 2. The second point of fixation is the
centre of metal septum midway between the two
horizontally placed holes (Fig. 6.43). When the
patient's eyes converge on this point, the images
of O no longer fall on both foveas, but on a retinal
element nasal to the fovea in each eye. Consequently, the O will be seen in uncrossed (homonymous)
diplopia and the patient sees DO and OG. When
the patient will exert a greater amount of
convergence, he/she may see only DG, because
the D and O and the G and O will overlap.
Position 3. The point of fixation is tip of a pencil
or other object held midway between the septum
and his/her eyes. When the patient's eyes
converge on this point, the images of both D and
O in the right eye and G and O in the left eye fall
on a retinal element nasal to fovea in each eye and
thus will be projected temporally, and the patient
will see OGDO on the card.
Position 4. The point of fixation is an object
(such as a picture on the wall) situated beyond
the printed card. When the patient fixates at this
distant point, the images of D and O and G and
O fall on retinal element temporal to fovea in
each eye and thus will be projected nasally, and
the patient will see D O O G.
Note: The aim of exercise with diploscope is
to teach the patient to obtain and maintain all
four positions with ease so that effortless
convergence and divergence is fully established.
It is advisable to practise for 2 to 3 minutes for 2
to 3 times a day. Position four is quite useful in
improving the fusional divergence (fusional
negative convergence).
151Evaluation of a Case of Strabismus and Orthoptic Instruments
REMY SEPARATOR
Remy separator is a simple instrument which
consists of a septum with a handle having a
transparent slide holder at one end and a nosepiece at other end (Fig. 6.44). The patient resting
the septum on his/her nose is instructed to look
through the slides at an object beyond them. If
his/her eyes are properly focused for the distant
object, the picture of the slides (such as a star
and a circle) will be imaged one on each fovea
and will be seen superimposed by the patient
(Fig. 6.45).
Uses. The instrument is designed in such a
way that when used properly, it teaches the
patient to relax his/her convergence and
strengthen the fusional divergence.
Fig. 6.45 Optical principle of Remy separator.
READING BARS
Reading bars are simple devices used to train
the patient for subjectively controlling the
maintenance of binocular vision.
Principle. All reading bars are based on the
principle of physiologic diplopia.
Common reading bars include thumb bar reader,
zig-zag bar reader, the Mayan bar reader, the
Jaual grid, Tibb's physiologic diplopia reader.
Method. By introducing a bar between the
patient's eyes and the reading material, the
patient is made aware of physiologic diplopia
(Fig. 6.46). As the patient reads the print
binocularly, he/she perceives the bar in crossed
diplopia, each image of bar hiding on position of
the print from one eye, but not the other, so that
Fig. 6.44 Remy separator.
Fig. 6.46 Zig-zag bar reader in use.
152 Theory and Practice of Squint and Orthoptics
the print can be read normally. Maintaining the
correct position of his/her eyes despite this
obstacle will strengthen the binocular vision of
the patient. This is a very useful and simple
home exercise.
CHEIROSCOPE
The cheiroscope (Fig. 6.47) is an instrument for
anti-suppression exercises. It consists of a
working base, a picture carrier to one side, a
headrest containing a pair of +7.0D spherical
lenses, and an obliquely placed septum
extending from the centre point between the
lenses to the base of the picture carrier. A plane
mirror is attached to the septum on the side
where the picture is located. The distance
between lenses and the working base is 14 cm,
which is the focal length of each lens and the
eyes are consequently focused for distance. Most
cheiroscope models may be turned around so
that the mirror is in front of the right or left eye,
depending upon which eye is required to fixate.
Uses. The instrument can be used in cases of
heterophorias, intermittent tropias, or small
tropias (in the latter, prisms to neutralize the
deviation have to be taped over the eyepiece).
Procedure. The picture to be copied is placed in
the picture carrier and a sheet of paper on the
base of the instrument. The patient should look
with his/her fixating eye into the mirror and
with the suppressing one on the paper. He/she
is instructed to trace the picture (which has black
outlines) on the paper using a pencil (a redcoloured pencil is very helpful, especially in the
beginning). Steady fixation of the picture should
be stressed to prevent rapid alternation, which
can be suspected, if the patient's drawing is
either smaller or larger than the picutre or if
parts of the picture are missing.
TIBB'S BINOCULAR TRAINER
The Tibb's binocular trainer (Fig. 6.48) is a
haploscopic instrument designed for home use.
However, in offices where a major amblyoscope
is not available, it can also be used as a
diagnostic instrument. It consists of three parts:
A middle septum and two wingboards that fold
together like a book. The middle septum has a
mirror on both sides so that it can be used with
either eye fixating. Each of the wingboards has
a vertical scale of 20 base-up and base-down
and a horizontal scale of 40-base in and baseout. Four cards (target carriers) come with the
instrument and consist of peripheral, macular,
and foveal superimposition and fusion pictures.
Uses. It can be used for both diagnosis and
treatment of suppression and abnormal retinal
correspondence and for increasing fusional
amplitudes.
Procedure. One wingboard is placed so that it
rests along the table at a slight angle to it. The
vertical wingboard is to the right side, when the
right eye is the fixating one; it is to the left side,
when the left eye is fixating. The patient places
the bridge of his/her nose against the curved
part of the septum so that his/her visual axis is
perpendicular to the table. His/her head should
not be tilted.
One target carrier (such as the dog) is taped
on the vertical wingboard so the zero mark
shows in the window. This target is seen in the
Fig. 6.47 Cheiroscope.
Fig. 6.48 Tibb's binocular trainer. Direct cover test depicting
left exotropia.
153Evaluation of a Case of Strabismus and Orthoptic Instruments
mirror. The patient places another target on the
horizontal wingboard (such as the cage for
superimposition or another dog for fusion) and
moves it until the two images are superimposed.
This target is not viewed in the mirror.
COMPUTER-BASED ORTHOPTIC VISION THERAPY PROGRAMS AND INSTRUMENTS
Orthoptic vision therapy programs are
specialized therapeutic interventions designed
to improve and enhance a person's binocular
vision and eye teaming abilities. Orthoptic
vision therapy aims to correct issues such as
amblyopia (lazy eye), convergence and
divergence disorders, and other binocular vision
problems. Here's an overview of orthoptic vision
therapy programs:
GOALS OF ORTHOPTIC VISION THERAPY
1.Correct eye alignment: For conditions like
strabismus, the primary goal is to realign the
eyes so that they work together in a coordinated
manner.
2.Enhance vinocular vision: Vision therapy
helps improve the brain's ability to fuse the
images from both eyes, leading to better depth
perception and three-dimensional vision.
3.Strengthen eye muscles: Exercises and
activities are designed to strengthen the
extraocular muscles that control eye
movements.
4. Improve eye teaming and coordination: Vision
therapy helps individuals improve their ability
to converge (bring the eyes together) and
diverge (move the eyes apart) efficiently and
accurately.
5. Reduce suppression: In cases of amblyopia or
suppression (ignoring one eye's input), therapy
aims to eliminate suppression and encourage the
use of both eyes.
6.Enhance visual skills: Vision therapy can
improve skills such as tracking, focusing, and
visual processing, which are crucial for reading
and other visual tasks.
COMPONENTS OF ORTHOPTIC
VISION THERAPY PROGRAMS
1.Assessment: The first step involves a
comprehensive evaluation of the patient's visual
system, including eye alignment, binocular
vision, and eye movements. This assessment
guides the development of a personalized
therapy plan.
2.Customized therapy plan: Based on the
assessment, the orthoptist or optometrist
designs an individualized therapy plan that
includes specific exercises and activities tailored
to the patient's needs and goals.
3. In-office and home-based therapy: Orthoptic
vision therapy can be conducted both in the
clinical setting (in-office sessions) and through
prescribed home exercises. In-office sessions
typically occur weekly or biweekly, while home
exercises are performed daily or as instructed.
4.Vision therapy activities: Activities may
include eye exercises, games, puzzles, prisms,
3D stereograms, and computerized vision
training programs. These activities challenge the
visual system and gradually improve its
function.
5. Monitoring and progress evaluation: Progress
is regularly monitored, and therapy plans may
be adjusted to accommodate the patient's
changing needs and improvements.
6. Duration of therapy: The duration of orthoptic
vision therapy varies depending on the severity
of the condition and individual progress.
Therapy may last several weeks to several
months.
Computer-based Orthoptic Vision Therapy
Programs have brought a revolutionary change
in the diagnosis and management of orthoptic
disorders. Computer-based orthoptic practice
includes:
• Computerised orthoptic-diagnostic programs
for sensory as well as motor evaluation, and
• Computer-based orthoptic therapy programs
for vision therapy, and neurovision therapy.
• Combined diagnostic and therapeutic
programs. Some of these are listed below:
I. Computer-based diagnostic programs
• Electronic vision testing programs.
• Optodrum [Software for optokinetic drum
(OKN)].
• Digital Hess chart and diplopia chart
• BVA (Binocular Vision Assessment Program)
154 Theory and Practice of Squint and Orthoptics
• PTS (perceptual therapy system)
• ReadAlyzer eye movement recording system
• TOVA (test of variable attention)
• Visagraph
• Eye-tracking systems
• Video oculography (VOG)
• Digital visual acuity charts
• Stereopsis testing software
• Accommodative and convergence testing
Apps
• Visual field testing software
• Prism measurement tools
II. Computer-based therapeutic programmes
• Vision therapy programmes
• Neurovision therapy programmes.
III. Computer-based combined diagnostic and
therapeutic systems
• TRYe vision therapy software
• Computer orthoptics programe by HTS INC
solutions.
• Computer orthoptics DeStrain by Bynocs.
I. COMPUTERISED ORTHOPTIC DIAGNOSTIC
PROGRAMS AND INSTRUMENTS
Several applications are available for smartphones, tablets, laptop, and PCs that reproduce
many eye tests. These can be used by
optometrists, ophthalmologists and some
programs by the patients also. Computer
orthoptics includes complex monocular and
binocular stimuli, which allow automatic testing
and measurement of the following skills:
Oculomotor (pursuits and saccades); fusional
ranges; phorias; motor fields; fixation disparities,
suppressions; retinal correspondence; accommodative facility; stereopsis, visual memory and
aniseikonia.
Some common such programs are described
briefly.
1. Electronic vision testing programs. Electronic
charts are available for far as well as near vision
testing. Few examples are:
• Chart Pro (www.eyechartprotoapp.com)
• Optos’ chart remote (blog.optos.com/index.php/
optos.chart.remote.ipad.app)
• Vision Test (https://itunes.apple.com/ca/app/
vision-test/id380288414?mt=8 or https://
play.google.com/store/apps/details?
id=com.threesidedcube.visiondroid)
• With sight Book (www.digisight.net/patients/
vision_testing)
• AAPOS Vision Screening App.(www.aapos.org/
ahp/aapos_vision_screening_app) has optotype
for both adults and children, and can be used
by anyone including healthcare workers.
2. Optodrum. The Optodrum (www.linsay.
com/Linsay_associates_Medical/
Optodrum.html) is a good alternative to the
expensive and bulky optokinetic drum for
adults and children. It even has a version for
the iPad that uses its camera to record a video
of the patient’s eye movement while looking at
moving patterns.
3. BVA is a stand-alone binocular vision
screening program. It is capable of automatic
testing of heterophorias, fusional range,
saccades, pursuits, accommodation,
suppressions, fixation disparities and an
asthenopia survey.
4. PTS test. Computerized perceptual therapy
system allows automatic testing for speed of
information processing, visual sequential
processing, visual simultaneous processing.
5. ReadAlyzer eye movement recording
system. This system allows fixations,
regressions, fixation duration, reading speed,
cross correlation between right and left eye,
play-back of recorded eye movements.
6. TOVA (test of variables attention). It assesses
ADD, ADHD and impulsivity.
7. Visagraph an eye movement recording
system is capable of computerized recordings
of reading eye movements, saccades and
fixations.
8. Eye-tracking systems: These systems use
specialized cameras and software to monitor eye
movements and gaze patterns. They can assess
how well the eyes work together and track the
ability to follow moving objects smoothly.
9. Video oculography (VOG): VOG systems
record eye movements and are used to diagnose
and monitor nystagmus (involuntary eye
oscillations) and other eye movement disorders.
They provide detailed data on eye movement
characteristics.
155Evaluation of a Case of Strabismus and Orthoptic Instruments
10. Digital visual acuity charts: These
computerized charts display letters or symbols
on a screen and allow for precise measurement
of visual acuity. Patients read the characters
from a computer monitor, and the results are
recorded automatically.
11. Stereopsis testing software: Computerised
stereopsis tests present 3D images or objects on
a screen to assess the patient's depth perception
and stereopsis. They can be more engaging for
children and provide quantitative data on
stereopsis.
12. Accommodative and convergence testing
apps: There are apps and software programs
designed to assess accommodation and
convergence abilities. Patients view targets on
a screen and respond to prompts, providing
valuable data on their binocular vision function.
13. Visual field testing software: Computerized
perimetry tests assess the visual field and can
help detect and monitor conditions like
glaucoma or visual field restrictions. Patients
respond to stimuli displayed on a screen.
14. Prism measurement tools: Digital devices
can measure the amount and direction of prism
needed to correct eye misalignment. These
measurements are essential for prescribing
prism lenses accurately.
15. Digital Hess screen. See page 131.
16. Digital synoptophore. Described on page
146.
II. COMPUTER-BASED VISION THERAPY AND
NEUROVISION THERAPY PROGRAMS
VISION THERAPY PROGRAMS
Vision therapy is effective for:
• Eliminating amblyopia
• Breaking suppressions
• Improving oculomotor skills
• Improving visual memory
• Improving accommodative facility
• Altering retinal correspondence; increasing
fusional ranges; and/or treating strabismus.
The gamepad and mouse allow the patient’s
therapy responses to alter the target demands.
The Computer Orthoptics graphics are instantly
moved, rotated or changed to create any base-
in base-out disparity. A few computer-based
orthoptic programs are mentioned below.
1. Computer vergence system (CVS)
This program uses random dot stereograms to
form pictures that require bi-foveal fixation to
stimulate the vergence system. The program
gradually increases the amount of vergence
required to appreciate the stereogram picture
and can monitor progression on line. This may
be used as part of the home therapy program
and the results of the computer program are
often followed by an eye care professional with
print outs that can be brought in to the office
visit. A maintenance program consists of
activities that preserve the patient’s present level
of function and/or prevent regression of that
function. Maintenance begins when the therapeutic goals of a treatment plan have been
achieved, or when no additional functional
progress is apparent or expected to occur.
2. Perceptual visual tracking program (PVT)
This program is designed to improve specific
tracking deficits that are often found in persons.
Perceptual visual tracking skills are basic to all
aspects of reading and other academic areas.
Improvement in tracking is often accompanied
by improvement in reading, spelling, attention,
and speed of working. PVT contains a variety of
visual tracking programs that have been clinically
proven. They are game-like in nature so that
improvement takes place almost effortlessly.
Individuals of all ages from five years up can
benefit from PVT. It is a sophisticated yet userfriendly computer application that will run on
almost any personal computer.
3. Vision builder: Computer vision training
A home vision training program designed to
treat both binocular vision disorders such as
convergence problems (i.e. eye-teaming problems),
accommodation problems (i.e. non-refractive
focusing difficulties), suppression (i.e. “lazy
eye”) and eye-tracking difficulties, as well as
visual perceptual or visual information
processing difficulties that can impact on a
student’s learning by limiting their ability to
understand and remember what they see.