161 terms

Binocular Vision

4 Reasons why Humans have 2 eyes?
1) Sharper Vision
2) Spare Eye
3) Larger Field of View
4) Depth Perception (Stereopsis)
Binocular Summation
The improved visual acuity that 2 eyes have as compared to one alone.
In addition, 2 eyes allow for improved contrast detection threshold.
Binocular Visual Field in degrees?
120 degrees.
Temporal Crescents?
Monocular portions of visual fields; located laterally to binocular visual field.
5 Monocular Cues to Depth
1) Perspective
2) Occlusion
3) Elevation
4) Texture Gradients
5) Motion Parallax
3 Types of Objective Refraction
1) Retinoscopy
2) Auto-refractors
3) Photorefraction
5 Types of Subjective Refraction
1) Standard Subjective Refraction
2) Delayed Refraction
3) Binocular Refraction
4) Near Cylinder
5) Cycloplegic Refraction
If a patient is fully accommodating for a NEAR target, then the static and dynamic values are _________________.
The same
3 Types of Autorefractors in clinic:
1) Grand Seiko WR-5100K (open field)
2) Nikon Retinomax K+ (handheld)
3) Nidek TonoRef II
What can a "Photorefraction" test for?
1) Refractive Errors
2) Strabismus
3) Cataracts
5 Variations of a Subjective Refraction
1) Alternative Balances
2) Delayed Refraction
3) Cycloplegic Refraction
4) Binocular Refraction
5) Near Cylinder
What are Alternative Balances used for and what are the four techniques?
They are useful in patients that have unequal best corrected acuity between the two eyes.
The four techniques are:
1) Alternate Occlusion
2) Monoclar Build-up (NRA)
3) Equivalent Lag
4) Retinoscopy screening for emmetropia
What is a Delayed Refraction and when do you use it?
The purpose is to maximally relax a patient's accommodation without the use of drops to determine correction of refractive erros.
*Use without drops and when pt shows myopia on tests but you suspect latent hyperope.
*Useful in:
Latent hyperopes, pseudomyopia, accommodative spams, and give variable responses during refraction.
When you looking at near **** for a long time and then you quickly look up at a distance and it is blurry for some time. Use delayed refraction to test.
****Clues to suspect a Latent hyperope/pseudomyope/or accommodative spams?
1) Chief complaint of distance blue following near work.
2) Poor endpoints on refraction.
3) Esophoria at distance
4) High NRA (overminused distance refraction)
5) VA conflict with found Retinoscopy results.
Delayed Refraction procedure:
1) Complete routine refraction sequence.
2) Perform NRA (plus to blur at near)
3) Isolate distance 20/20 line or better
4) Binocularly reduce PLUS by .25D until patient reports the letters are clear--SLOWLY
4 Common CYCLOPLEGIC Agents:
1) Atropine
2) Homatropine
3) Cyclopentolate
4) Tropicamide
Details about Atropine
*Instill 3x/day for 3 days for full cycloplegia
*Cycloplegia lasts for 7-10 days
*Mydriasis lasts up to 2 weeks
*MAY be used in treatment of amblyopia or uveitis.

Tradename is "ISOPTO ATROPINE"
Details of Homoatropine:
*Cycloplegia results in ~45-60 minutes
*Doesn't produce a sufficient cycloplegia for children UNDER 15 years.
*Not used much by OD's...may treat UVEITIS.

Details of Cyclopentolate:
*Short duration cycloplegic.
*Available in both .5% and 1.0% solutions.
*Cycloplegia results in 30-45 minutes and lasts for 25 hours.
*Very commonly used by Optometrists for diagnostic purposes

Tradename "CYCLOGEL"
Also comes in a combo drop with phenylephrine called "Cyclomydril"
Details of Tropicamide:
*Short duration cylcloplegic agent.
*Available in .5% and 1.0% solutions
*Instill 3-4 hors of 1% seperated by 1 minute for full cyclo.
*Cyclo results in 30 minutes and lasts 2-6 hours.
Commonly used for diagnostic purposes

Trade names:
Mydriacyl and Tropicacyl
When do you use Cyclopentolate?
-Every first time patient in Pediatrics Clinic.
-Patients with esoptropia
-->helps to determine if accomm component
-Patients with Large Esophoria
-->Hyper +eso @ near=asthenopic

*Suspect latent hyperopia/pseudomyopia/over-minused in previous Rx
When do you use Tropicamide?
On returning patients to the pediatrics clinic:
1) Without strabismus
2) Normal accommodation
3) Cooperative on dry retiniscopy and routine refraction
What is the residual accommodation with tropicamide found to be?
As compared to cyclopentolate?
Residual accommodation: 4-6 hours

With cyclopentolate: .75D
What is Anticholinergic?
It antagonizes acetylcholine receptors.
Inhibits response of iris sphincter and ciliary body muscles.
Thus causes cycloplegia (paralysis of accommodation) and mydriasis (dilation of the pupil)
Who is susceptible to Adverse reactions of Anticholinergics?
1) Those who have had previous adverse reactions
2) Frail cardiovascular system
3) Compromised CNS
-->cerebral palsy
-->Down syndrome
-->Traumatic Brain injury
4) Narrow Angle
Overdose amounts of Atropine for adults and pediatrics?
Peds: 10mg is max dosage but may get adverse reaction with as little as .5mg

Adults: Fatal dose is unknown, up to 1000mg has been given but expected max dosage is 100-200mg.
How much atropine is in a drop of 1% solution?
1% solution=10mg/ml=.6mg/drop
2 drops in each eye gives a total 2.4mg instilled.
Mnemonic for remembering adverse reaction/overdose of ATROPINE:
"Hot as a hare, blind as a bat, dry as a bone, red as a beet, and mad as a wet hen."
What are most newborns "expected" refractive error?
6-8 year olds?
+1.50 to +2.00

+0.50 to +1.00
Astigmatism changes rapidly during first _____________ years and then stabilizes.
1.5 years
Amblyope rates:
Hyperope: >+5.00Ds
Myope: > -8.00Ds
Astigmatism: >-2.50DC

Anisometropia: >1.50 between the two eyes
Consider giving an Rx:
Hyperopes: >+2.00Ds
Myopia: >-5.00Ds @ any age
---- (-3.00Ds) to -5.00, Rx @ ages 1-3 yo
---- (-1.00Ds) to -3.00Ds, Rx at @ ages >3 yo

Astigmatism: >1.25Ds, Rx at age greater than 3yo if deemed stable.
Saladin's Norms:
Phoria: 2XP +-3
BI: x/10/5
BO: 15/20/15

Phoria 4XP +-1
BI: 15/20/15
BO: 15/20/15
Cycloplegic agents that we use are Anticholinergic which means that they:
1) Antagonize Acetylcholine Receptors
2) Inhibit iris sphincter and ciliary body muscles
3) Result in cycloplegia and mydriasis

careful when using drops on patients with down syndrome.
5 Benefits of Binocular Refraction
1) Equal Luminance of Light
2) Greater Control of accommodation
3) Peripheral Vision
4) Vergence feedback stabilizes CA/A.
5) More accurate endpoint of cyl axis.
3 Ways to dissociate
1) Fogging (Humphriss)
2) Septums (Turville, Morgan) (Infinity Balance)
3) Polarized Characters (Vectographic slide)
Case Analysis looks for:
1) Binocular Anomalies
2) Accommodative Anomalies
3) Oculomotor anomalies (comb of the above)
Four approaches to Case Studies:
1) Graphical Analysis
2) Optometric Extension Program (OEP) Analytical Analysis
3) Morgan's system of normative analysis
4) Fixation Disparity Analysis.
Graphical Analysis portion of the case study.
The purpose is to determine is a patient is expected to have clear, single, comfortable binocular vision.
*Achieve this by plotting clinical accommodation and binocular findings.

The test that you usually plot are:
-Dissociated phoria (Von Graefe)
-BI & BO blur/break/recovery
-Amplitude of Accommodation
What does Sheard tell us about?
Tells us that FUSIONAL reserve should be twice the demand (phoria).
Used in regards to Graphical Analysis.
OEP-Optometric Extension program tells us:
It has a regimented 21 point exam using specific instructions.
Chains-groups data.
Uses case-typing to identify the data.
1)Understands that the visual system will deteriorate over time and 2)Vision problems can be prevented through the use of lenses, prisms, and VT.
Normative Analysis (Morgan's System):
Grouping of data based on trends.
Little significance attributed to one given test.
Compare clinical data to Morgan's norms then look for trends in Groups A, B, or C.
Clinically significant if an entire group lies in one direction.
Fixation Disparity Analysis info:
It is #4 on the Case Analysis:
Refers to a small misalignment of eyes under binocular conditions.
Deals with associated phoria which is the amount of prims needed to neutralize the fixation disparity.
Make a graph...four criteria for analysis:
Type of Curve, Slope, X&Y intercepts

Gathered under binocular vision...most effective method for determining the amount of prism to prescribe.
Integrative analysis:
attempts to take the other 4 methods together and analyze the data.
Requires 3 distinct steps:
1) comparing individual tests to table of expected findings
2) grouping the findings that deviate from expected findings
3) identify the syndrome based on the first 2 steps
3 Types of Binocular Refraction
1) Humphriss (fogging)
2) Infinity (Turville/Morgan SEPTUM)
3) Vectographic slide (vectograms)
2 Types of Symptom checklists in Integrative Analysis:
2) Convergence Insufficiency Symptom Survey (CISS)
---want a score of 15 or less on the COVD QOL.
How do we determine if there are clinical signs of convergence insufficiency?
Exam with the following:
1) Refractive Error/Visual Acuities
2) Binocular Alignment and Vergence Ranges
3) Fusion-motor & sensory
4) Accommodation
5) Ocular Motility
How to test MOTOR fusion?
Cover test at distance and near.
Phoria at distance and near (von Graefe)
Fixation Disparity
AC/A and CA/C ratios
How to test for SENSORY fusion?
Suppression=worth 4 dot
Local (contour) stereopsis
Global Stereopsis.
How to test for Accommodation?
Monocular/Binocular Accommodative Amplitude.
Monocular/Binocular Accommodative Facility.
MEM Retinoscopy.
Fused cross-cylinder (FCC)
Tests of Ocular Motility?
NSUCO ---saccades AND pursuits.
DEM-Developmental Eye Movement Test.
-->reading eye movement test. difference between vertical and horizontal eye movements.
VISAGRAPH: reading test with infrared goggles that track where the eyes are.
Advantages of Integrative Analysis:
checks, chains, and types.
2 unique concepts: status of the visual system can deteriorate over time. vision probs can be prevented.
looks at groups of findings vs individual data
binocular conditions are included in the test data.
What are the 3 steps of Integrative Analysis:
1) Compares individual tests to table of expected findings
2) grouping the findings that deviate from expected findings
3) identify the syndrome based on the first 2 steps
Integrative Analysis divides Optometric Data up into 6 different groups:
1) Positive Fusional Vergence
2) Negative Fusional Vergence
3) Accomodative System
4) Vertical Fusional Vergence
5) Ocular Motor System
6) Motor Alignment and Interaction
Tests to evaluate Positive Fusional Vergence:
BASE OUT--forces eyes to converge & accommodate

Positive Fusional Vergence Facility.
Binocular Accommodative Facility with PLUS lenses.
Fused Cross Cylinder
Tests to evaluate Negative Fusional Vergence:
BASE IN--cause the eyes to diverge and relax accomm

Binocular accommodative facility with minus lenses.
MEM retinoscopy
Fused cross-cylinder.
Tests evaluating the Accommodative System
Monoc and Binoc accommodative facility testing with +/- lenses.
MEM retinscopy
Fused Cross-Cyl

normal lag?
what's the amplitude?
Tests to evaluate the Vertical Fusional Vergence:
Fixation Disparity.

no accommodation plays a role
Tests to evaluate the Ocular Motor System:
NSUCO--saccades & pursuits
How many 6 groups, but how many "common accommodative, ocular motility, and binocular vision problems" to choose from?
Based on Duane-White classification.
Distance phoria + AC/A
A low AC/A tells us there is going to be an ____________.
A high AC/A tells us that it's going to be an _________________.
Different types of Accommodative Anomalies:
*Accommodative Insufficiency
*Ill-sustained accommodation
*Accommodative excess (spasm)
*Accommodative infacility
Ocular motor anomalies can be divided into:
Saccadic deficiency.
Pursuit deficiency.
Used to predict how tonic, accommodative, and fusional vergence results in the final eye position.
Graphical Analysis.
Visually represents the ranges of stimulus values through which a patient will have comfortable binocular vision.
Zone of Clear Single Binocular Vision.
On the graphical analysis, the horizontal axis represents ___________ while the vertical axis represents the _______________.
Convergence = x axis
Accommodation = y axis
The graphical analysis determines the relationship between 3 things:
1) Interpupillary distance
2) Accommodative Demand
3) Vergence Demand
What is the demand line?
An oblique line drawn through the graph that connects points that indicate stimulus to accommodation & convergence stimulus when the target distance was varied without a change in lens or prism power.

A larger PD causes a greater vergence demand.

Demand = 1/test distance (m)
Convergence Demand (stimulus) = PD(cm) x fixation distance (D)
The zone of binocular vision is greater/less than the zone of clear binocular vision.
_____________ determines the height of the zone of clear single binocular vision (ZCSBV).
Amplitude of Accommodation.
The Left side of a graphical analysis stands for what?
The right side?
BI Blur.
BO blur
The width from the phoria to BI blue is the ____________________.
The width from the phoria to BO blur is the ____________________.
Negative Fusional Convergence.
Positive Fusional Convergence.
Sheard's Criteria are used for what?
What is the formula?
Reserve (R) should be twice the demand (D).

Prism to Rx = (2/3)D-(1/3)R
Percival's Criterion
Demand should fall within the middle 1/3 of ZCSBV.
Lesser amount (L) of Vergence ranges (BI or BO) should be at least half of greater amount (G).

Prism to Rx= (1/3)G-(2/3)L
Formula for "Prism to Rx (BO)"
(Esophoria - base in recovery)/2
Prescribing prism will _____________ shift the demand line.
Prescribing BI prism shifts the line to the ___________.
Lenses alter the demand on accommodation without directly affecting vergence.
Prescribing lenses VERTICALLY shifts the demand line.
Plus lenses shift the demand line DOWN because less accommodative demand is needed.
What is the left limit of the ZCSBV?
What is the right limit of the ZCSBV?
BI blur findings.
BO blur findings.
CA/C is affected by BO prism how?

how about with BI prism?
BO prism:
-causes convergence
-stimulates accommodation
-patient must compensate by relaxing accommodation

BI prism:
-causes divergence
-relaxes accommodation
-patient must compensate by stimulating accommodation.
What does the banana curve compare?
Compares the relationship between the dissociated phoria (cover test) and the fixation disparity.

Suppression and Variability are abnormal.
3 Criterion for matching the Banana Curve:
1) Phoria and fixation disparity in the SAME DIRECTION. (both exo or eso). Measurements of ortho, 1 eso or exo don't matter.

2) Magnitude of fixation disparity between 4'eso and 6'exo, regardless of phoria magnitude

3) Magnitude of fixation disparity is proportionate to the phoria as depicted by the banana curve.
What test is designed to reveal a latent exophore?
Forced Vergence Test

let patient fuse with a BI prism for 1-2minutes.

Record prism amount for neutrality -4=finding
Kinetic Cover Test
Objective measurement.
Can determine AC/A.
Indirectly measures accommodative spasm.

-neutralize phoria @ 50cm, then push in to 10cm.
-continue alt cover test while moving target closer to patient.
-look for phoria differences.
What is Visual Efficiency and what are the four components?
The ways in which various ocular systems operate over time and under various viewing conditions.
1) Sufficiency (amount/amplitude)
2) Facility (flexibility)
3) Accuracy
4) Stamina
Visual Efficiency typically looks at 3 areas:
1) Oculomotor (eye tracking)
2) Accommodation (eye focusing)
3) Binocular Status (eye teaming)
Accommodative and BV disorders are _______ times greater than prevalence of ocular disease in children 6months to 5 yo.

They are _____________times greater in kids 6yo to 18 yo.
In a study of ~1600 patients between ages 18-36 ______% had symptoms related to BV dysfunction.
Roughly ____% of patients schedule a vision exam based on computer related vision complaints.
______million eye care exams provided annually cuz of CVS.
10 million
Visual symptoms occur in ______-______% of people who work at visual display terminals
Signs of CVS
Receded NPC
Low or high AC/A
Reduced vergence ranges
Low accommodative amplitude
Greater exo or eso at near than distance.
Giving ________ works well for patients with accommodative issues as well as patients with a high AC/A ratio.

Giving _______ works well for those with a vertical heterophoria.
3 Important components of eye movements
1) Saccades
2) Fixations
3) Regressions
Saccade info:
take up approximately 10% of reading time
average saccade is 8-9 letters.
saccade length can vary from 2-18 characters
Fixation info:
occur between saccades
normal readers: average duration of 200-250ms
Duration can range from 100 to over 500ms
Regression info:
Right to left eye movement.
Occurs when reader overshoots target, misinterprets text, or has difficulty understanding text.
Skilled readers have this happen 10-20% of time.
3 theories about the relationship between eye movements and reading
1) eye movement disorders can cause below average reading ability.
2) random, unskilled eye movements found in poor readers are secondary to deficient language skills that cause reading disorders.
3) combination of the first 2.
By age 3yo, should be able to maintain steady constant fixation of a target for ______ seconds.
10 seconds
How long does the average saccade last?
What are the duration of saccades?
What are saccades used for? How fast can they go? What are the normal latency? Basic facts?
They enable rapid redirection of the line of sight to allow foveal viewing.
They are the fastest eye movement with velocities up to 700degrees/second.
The normal latency is about 200ms.
Reaction time can depend on luminance, size, contrast of target, motivation, and attention.

Used in reading, 2 degree visual angle, roughly 8-9 character spaces, and take up approximately 10% of reading time.
What are PURSUITS used for? Maximum velocity? Latency? Basic facts?
These enable continuous clear vision of moving targets. They allow for continuous foveal fixation of moving objects.
The maximum velocity is approximately 60 degrees per second.
Have a shorter latency period than saccades...about 130ms.
Affected by age, attention, motivation.
Drugs that affect eye movements: potential causes of OMD
Diazepam (anxiety)
Phenytoin (seizures)
Phenobarbital (seizures)
Methadone (opioid dependence, severe pain)
Chloral hydrate (insomnia)
Lithium (bipolar)
DEM (Developmental Eye Movement Test) facts:
Has a visual verbal format to test saccades.
Patient is frequently asked to call off a series of numbers as quickly as possible. 2 vert, 1 horiz.

Determines SACCADIC problem and looks at Rapid Automated Naming (RAN).
DEM results:
1) Normal Vertical, slow to very slow Horizontal
2) Slow vertical, normal horizontal
1) Classic SACCADIC dysfunction
2) Paradoxical
NSUCO test info
Only test that involves PURSUITS.
Developed by Dr. Maples.

Direct observation of saccades and pursuits.

Rate patient based on ability, accuracy, and head & body movement. Graded on 1-5 scale.
Harmon Distance:
distance from the patient's elbow to middle knuckle.
Coding and bIlling of Oculomotor Dysfunction:
Abnormal fixations: irregular eye movements; unspecified disorder of eye movements

Abnormal saccades: saccadic deficiency/dysfunction

Abnormal pursuits: pursuit deficiency/dysfunction
Irregular eye movements: 379.59
Unspecified disord of eye movements 378.9

saccadic deficiency/dysfunction 379.57

pursuit deficiency/dysfunction 379.58
Oculomotor dysfunction deals with problems with _________, __________, & ___________.
Test(s) to evaluate saccades:
Test(s) to evaluate pursuits:
Roughly _____% of schoolchildren in the USA are diagnosed with learning disabilities.

Of these, approximately _______% have reading problems
3 things that cause an increased % for learning disabilities
1) Malnutrition
2) Low Birth Weight
3) Premature birth (less than 37 weeks, normal is 40 weeks)
Definition of Reading:
The transfer of an idea (concept, information, emotion) from one person to another through a visual code.
Reading efficiency decreases when print size is smaller than _________times the BVA.

20/20 BVA = print size 20/__or larger.

1st grade font is typically 20/100
12 point font is typically 20/70
Reduction in__________ allows for reading that is more comfortable, faster, and with better comprehension
Psychoeducational evaluations consist of 4 major areas:
1) History
2) Cognitive Functioning
3) Academic Achievement
4) Emotional Functioning

required in most states to be classified with a learning or reading disability.
Psychoeducational eval-Cognitive testing evaluates:
1) Language
2) Memory
3) Auditory and Visual perceptual skills
4) Visual motor abilities
5) Attention and concentration
6) Processing speed
7) IQ level
Fixational Disparity
1) Small misalignment of the eyes under binocular conditions.
2) Under these binocular conditions, the 2 eyes may converge to a point either in front of or behind the intended point.
Slight OVERconvergence=______ fixation disparity
Slight UNDERconvergence= ______ fixation disparity
Fixation Disparity Targets consist of 2 parts:
1) Binocular Fusion Lock
--binocularly visible parts
2) Two nonius lines
--seen monocularly via Polaroid Filters
--if a patient has a fixation disparity, both nonius lines will be seen but will be misaligned.
Saladin banana curve compares _______________ and _____________.

Curve is based on ________ __________.

What is it NOT a plot of?
compares dissociated phoria and fixation disparity.

It is based on population norms.

It is NOT a plot of a patient's fixation disparity.
When is it good to do a Fixation Disparity Test?
The patient has symptoms and no signs.
Pt has signs and no symptoms
Need to determine the amount of prism to Rx.
Determining the progress of VT.
The Forced Vergence Fixation Disparity Curve measures what?
how do you do the test?
Measures the robustness of the binocular system.
Places increasing amounts of prism and measures the fixation disparity.

Measure with test in the following sequence:
no prism, 3BI, 3BO, 6BI, 6BO, until patient no longer maintains fusion.
BI=causes divergence (NFV), thus gives ESO
BO-causes convergence (PFV), gives EXO
What is the difference between a "fast" disparity vergence system and a "slow" vergence adapation system?
eliminates retinal disparity, restores single binocular vision, fixation disparity remains.

increases tonic vergence.
Provides vergence needed to compensate for prims thus reduces levels of fast disparity vergence.
results in reduced amount of fixation disparity.
On a fixation disparity curve what is plotted on the horizontal axis, and what is plotted on the vertical axis?
horizontal axis: Amount of prism
vertical axis: amount of fixation disparity.
What are the Y-intercepts, X-intercepts, and the slope on a Fixation Disparity Curve?
Y-intercept: fixation disparity (no prism in place)

X-intercept: associated phoria (amount of prism required to produce no fixation disparity)

Slope: typically measured as the rate of change between 3BI and 3BO. Shallower slopes lead to less symptoms and steeper slopes mean more symptomatic.
Type I fixation disparity curve?
Most people show type I pattern
60% when tested @ distance
70% when tested @ near.
FD changes gradually with added prism in the fusional vergence range.
FD changes much more rapidly towards the limits of fusion until diplopia reached
Type II fixation disparity curve?
ESOphoric patients
"Flat on the BO side"
25% of population when tested at distance or near.
Flat region on BO side.
May never cross the x-axis.
Sharply curved on the BI side.

Very very poor adapation to BI prism
Type III fixation Disparity curve?
"Flat on the BI side"
0% of population when tested at distance
10% of population when tested at near.
Flat region occurs on BI side
Sharply curved on BO side.

Poor adaptation to BO prism
Type IV Fixation Disparity curve?
"little change with added prism"
5% of population when tested at distance or near.
Very little change in FD with increased vergence demand from increasing prism.
May show no x-intercept.
Associated with ANISEIKONIA and other sensory fusion problems.
What type of lenses work well for symptomatic esophoric patients?
PLUS lenses.
Shift fixation disparity plot upward or downward

Esophoria=use PLUS lenses
Divergence excess= use MINUS lenses
What should you start with when you aim to use Prism to fix disparity curve?
you should start with the Dissociated Phoria or associated phoria.
The big goal of VT is to ?
Increase Vergence Adaptation capability.
flattens the fixation disparity curve.
patients with steep slopes are good candidates for vision therapy.
Units used to test for fixation disparity include:
Disparometer, mallet box, wesson card, and saladin card.
3 Ways to treat Fixational Disparity:
1) Prisms (Rx off associated phoria)

2) Added lenses
-determine amount of added lens power needed to reduce fixation disparity to zero

3) Vision Therapy
-improves vergence adaptation
-flattens the slope of the fixation disparity curve
Convergence Insufficiency Symptom Survey & COVD QOL
15 questions.
Score >16 is diagnostic for children age 9-17 yo.
Score >21 yo is diagnostic for adults 18yo+
Change in 10 points in clinically significant

30 items; now 19-item survey for improved efficiency.
score >20 diagnostic
What is the Sequential Management Approach in General Treatment?
1) Optical Correction of Ametropia
2) Added lens power
3) Prism
4) Occlusion
5) Vision Therapy
6) Surgery
Prisms are used to decrease the demand on ________ ___________.

Used in the following situations
Fusional Vergence.

horizontal & vertical relieving prism,prism to aid vision therapy, prism when visual therapy not possible, prism at the end of vision therapy, brain injury, cosmetic.
How do you determine the amount of horizontal PRISM to Rx?
1) Sheard's Criterion
-Reserve (R) should be twice the demand (D)
-demand equals phoria
-Prism to Rx = (2/3)D-(1/3)R

2) Percival's Criterion
-Demand should fall in middle 1/3 of ZCSBV
-Lesser amount (L) of vergence ranges (BI or BO) should be at least half of greater amount (G)
-prism to Rx = (1/3)G-(2/3)L

3) 1 to 1 Rule
-recovery > phoria
-mostly used for esophoria
-recovery used is opposite base direction as phoria measurement
-Prism to Rx (BO)=(esophoria - base in recovery)/2
When is occlusion typically used?
Patching recommendations for:
moderate amblyopia: 20/30-20/80?
severe amblyopia: 20/100 or worse?
Patch for 2 hours a day with at least 1 hour of near work.
Patch for 6 hours a day with at least one hour of near activities
Long term effects of Vision Therapy?
Develops normal motor and sensory fusion, accommodative skills, and oculomotor control.

-reduces symptoms, increases accom amplitude & facility, eliminates accomm spasm, improves near point of convergence, increases fusional vergence amps & facility, eliminates suppression, improves stereo, improves accuracy of saccades & pursuits, and improves stability of fixation.
When do you want to consider Surgery?
Highly unlikely for nonstrabismic binoc vision, accomm and oculomotor disorders.
May want to consider is HORIZONTAL PHORIA EXCEEDS 30 diopters.
Convergence Insufficiency facts:
ortho or low exo at distance
Receded near point of convergence.
Reduced positive fusional vergence.

Reported in 3-5% of population.
Typically rests head on hand/covers eyes.
Can take the Convergence Insufficiency survey!
low MEM
Convergence Insufficiency secondary conditions.
Accommodative Excess and Accommodative Insufficiency

Accom Excess:
overusing accomm convergence to supplement reduced positive fusional vergence.
Tank with "+" lenses.
NRA reduced!
May lead to accom spasms!

Accom Insufficiency:
pseudo convergence
Patient underaccommadates, reduced convergence
Huge demand on PRV
Tanks with "-" lenses.
Low PRA and Amp of Accom
Divergence Insufficiency facts:
Greater ESOPHORIA at distance than near.
Reduced Divergence at distance.
normal versions

Least common
Symptoms of Divergence Insufficiency:
Intermittent diplopia at distance.
worsens at end of day or when fatigued.
Greater eso at distance than near.
difference can be as little as 8^.
Comitant in all positions of gaze.
DDx of Divergence Insufficiency:
1) Convergence Excess
-Greater ESO at near than distance
2) Basic Esophoria
-normal AC/A.
-roughly same phoria at distance and near.
Signs of 6th nerve palsy
occasionally found in Divergence insufficiency.

-noncomitant deviation
-Endpoint is nystagmus.
What type of prism do you use to fix DI?
Horizontal BO prism.
With VT to treat DI, what are the goals?
Goals are to increase NFV @ distance, improve vergence facility, eliminate diplopia, reduce/eliminate all of patient's symptoms.
Convergence Excess (CE)
Most common BV problem (1.5-8.2%)
Eso at near, gets GREATER at distance
Reduced NFV.

associated with reading/near work.
What is the % of the population that suffers from Convergence Excess?
Convergence Excess details...what is diagnostic?
Greater ESO at near than distance.

difference as little as 3^ between distance and near may be diagnostic.

HUGE lag on MEM.
4 pharmaceuticals that can cause convergence excess:
1) Eserine
2) Pilocarpine
3) Excessive Vitamin B1
4) Sulfonamides
What pharmaceutical can treat convergence excess?
-echothiophate iodide drops, diisopropyl fluorophosphate ointment, causes miosis and ciliary spams.
Reduces ESO, less accomm convergence.
Divergence Excess symptoms:
Greater EXO at distance than Near.
Only BV issue that has completely normal convergence ability.
Exo deviation may be a phoria or tropia.
Normal stereo at near.
What percentage of strabismic patients have Divergence Excess?
7-24% of patients had divergence excess type exotropia.
What % of Divergence excess patients have been found to have a vertical deviation?

may be related to overreaction of inferior oblique.