Binocular Vision Exam Questions

• Ariette Acevedo, O.D. presents "Binocular Vision & Accommodative Dysfunctions"

Advantages of Binocular Vision

• Single and clear vision is an advantage.
• Stereopsis, the most precise kind of depth perception is an advantage.
• Visual field enlargement is an advantage
• Compensation for the natural blind spot which falls temporally and is 20° from the fovea, is an advantage
• Each eye compensates for the blind spot of the other, enhancing the overall visual field

Anomalies of Binocular Vision

• Anomalies of binocular vision are divided into categories:

• Binocular Vision (BV) is maintained (fusion), though often with stress

• • These cases may involve heterophorias, fixation disparity, or accommodation anomalies
• • Conditions are associated with excess or deficiency of accommodative convergence

• Binocular Vision is absent (will be covered this semester)

  • Strabismus (heterotropias) is most common in vertical deviations and high refractive error
  • Adaptive processes such as Suppression, amblyopia, eccentric fixation, and anomalous retinal correspondence (ARC)

Heterophoria

• Heterophoria is a binocular vision anomaly
• Phoria position is the "physiological position of rest"
• The position the visual axes take with respect to one another in the absence of all input to fusion.
• Most cases are at distance ortho (parallel) or slightly divergent if no accommodative stimulus is present
• Evaluated under dissociated conditions
• Assessment involves using the Cover Test: Alternating Cover Test (ACT)
• Other dissociation methods can be employed
• Prism – using 6 BD and 12 BI(one to dissociate and another to measure)
• Von Graefe Phorias - requires reliable patients for accurate results

Retinal Correspondence

• Corresponding Retinal Point (CRP) is involved with retinal correspondence
• Two retinal points, in each eye, facing in the same direction, allow for depth perception
• When stimulated simultaneously, they send impulses to the same point in the visual cortex
• CRP produces the perception of seeing a single object known as fusion
• Points nasal to the fovea in one eye correspond to points temporal to the fovea of the opposite eye

Maddox Rod and Diplopia

• Maddox Rod testing performed in OD
• In exophoria cases, with the Maddox Rod in OD, the object is imaged to the right side of the fovea
• Object is seen in the left visual field, resulting in crossed diplopia
• The resulting image is perceived opposite the side of the deviation
• In esophoria cases, with the Maddox Rod in OD, the object is imaged to the left side of the fovea
• Object is seen in the viewer's right visual field = uncrossed diplopia
• The image is perceived on the same side as the deviation.

Anomalous Retinal Correspondence

• Anomalous Retinal Correspondence (ARC) occurs frequently in strabismus
• Corresponding retinal points do not have the same visual directions.
• The fovea of one eye shares a common visual direction with an extrafoveal area in the other eye.
• ARC is an attempt to regain the binocular advantage.
• More likely when the angle of strabismus is small and the extrafoveal point is close to the fovea
• In cases of manifest strabismus, the eyes can see a single binocular image

Retinal Disparity

• Retinal disparity describes the small difference between the images projected on each retina
• A slight or small retinal disparity is necessary for depth perception and stereoacuity and acts as a binocular cue for depth
• Diplopia occurs if retinal disparity is larger is large
• Vergences are necessary for binocularity
• Remember these are binocular eye movements in opposite directions
• Reasons for not having good BV include accommodative and binocular dysfunctions
• When BV skills are tested, test should include: tracking, fusion, stereopsis, vergences and visual motor integration

Vergences

• Motor fusion is necessary to maintain Single Clear Binocular Vision (SCBV)
• Motor fusion is required for maintaining SCBV when vergence demand increases
• Fusional vergence is the maximum vergence movement that allows SCBV to be maintained until the point of diplopia
• Excessive stress on the vergence system, or the inability to converge or diverge correctly, may result in symptoms.
• Sometimes, there is a loss of control of ocular alignment or decompensation of a latent phoria.
• Vergences refers to binocular disjunctive eye movements
• Fusional Demand: amount of vergence required to see single (another term for phoria
• Fusional Reserves: which refer to the amount of vergence remaining after compensating for a phoria
• Positive Relative Vergence (PRV) and Negative Relative Vergence (NRV) are measured from the zero point or demand point
• Positive Fusional Vergence (PFV) and Negative Fusional Vergence (NFV) measured from the phoria position

Fusional Vergence Anomalies

• A phoria differs from a tropia through fusional vergence
• Fusional movements, based on disparity information, prevent the latent deviation from becoming manifest.
• Hyperopia in children is a risk factor in developing functional strabismus
• Constantly using fusional vergence can result in a latent deviation becoming manifest.

Visual Skills

• Having more than 20/20 visual acuity is needed to have functional visual skills
• Just because a patient sees 20/20 at distance and near does not mean they "see well"
• Visual skills necessary in day to day tasks include Eye tracking, Eye teaming and Eye focusing
• Remember: 80% of what is learned is received via the visual system
• Case history is important, so be sure to ask specific questions, instead of questions about blurry vision
• There is a 19 item COVD-QOL checklist questionnaire to help gauge vision
• There is a 14 item COVD-QOL questionnaire for vision screening in children with learning disabilities

Common Complaints in Young Patients

• Parents bring their children in because of:
  • Getting too close to read
  • Reporting headaches after school
  • Needing to trace with finger while reading
• Examinations may be unremarkable
• When unremarkable, look carefully on accommodative, binocular or oculomotor dysfunctions
• If all exams are adequate, look for learning disabilities, visual perception, discrimination, and/or memory problems

Definition of Accommodative and Vergence Dysfunction

• Accommodative dysfunction interferes with the eyes' ability to focus clearly at various distances, resulting in unclear retinal images
• Vergence dysfunction involves disjunctive eye movements of convergence or divergence, resulting in the inability of the eyes to fixate and stabilize a retinal image accurately.

Conditions

• Oculomotor Anomalies include Saccadic dysfunctions and Pursuit dysfunctions
• Accommodative Dysfunctions include Accommodative Insufficiency, Accommodative Excess, Accommodative Infacility and III-Sustained Accommodation
• Vergence Dysfunctions include Convergence Excess, Divergence Excess, Divergence Insufficiency, Convergence Insufficiency, Basic Exophoria, Basic Esophoria and Fusional Vergence Dysfunction

Evaluation

• Patient History is important in evaluation processes:
  • Nature of presenting problem and chief complaint
  • Visual, ocular, and general health history
  • Developmental and family history
  • Medication usage and allergies
  • Vocational, educational, and avocational vision requirements
• Ocular Examination: during evaluation processes:
  • Visual acuity (distance and near)
  • Refraction
  • Ocular motility and alignment (cover testing, versions, measurement of heterophoria using Risley prisms in a phoropter, a Maddox rod, or a stereoscopic device)
  • Near point of convergence
  • Near fusional vergence amplitudes (age-appropriate testing)
  • Relative accommodation measurements (positive and negative relative accommodation)
  • Accommodative amplitude and facility
  • Stereopsis
  • Ocular health & systemic health screening
• Supplemental is important in Evaluation processes:
  • Accommodative convergence/accommodation ratio (distance-near method or gradient method)
  • Fixation disparity/associated phoria
  • Distance fusional vergence amplitudes
  • Vergence facility
  • Accommodative lag

Accommodative Conditions

• When a patient presents with an accommodative problem, determine if the cause is functional or organic.
• Organic Accommodative problems, such as paresis of accommodation, are less common than functional anomaly
• Organic accommodative problems have very distinct signs and symptoms:
  • Sudden onset loss of accommodation in one eye
  • Severely diminished amplitude of accommodation
  • Neurological findings may be present:
  • Pupil abnormalities (mydriasis)
    • Non-comitant strabismus
  • Other: sharp headaches, vertigo, dizziness, diplopia, neck stiffness, micropsia or macropsia

Risk Factors for Accommodative Dysfunctions

• Need to sustain increased accommodation for near targets
• Accommodative fatigue
• Accommodative adaptation
• Slow accommodation
• Various drugs and certain systemic diseases: DM and Myasthenia gravis

Accommodative Dysfunction General Symptoms

• Symptoms of Accommodative Insufficiency, Excess and Infacility are:
  • Decreased VA at distance (fluctuating)
  • Decreased VA at near- usually appears after reading for prolonged time
  • Falls asleep or looses concentration easily while performing near work
  • Eyestrain or fatigue
  • Headaches above the eyes while working at near (school days), none on weekends, light sensitivity
  • Letters in and out of focus and bringing reading material very close
  • Visual guessing (misreads words or confuses them)

Accommodative Dysfunction General Signs

• The are VA findings:
  • Fluctuating during the examination is a key finding
  • Inconsistent VA findings between entering VA and refractive status can be a hallmark
• Pupils:
  • Fluctuating pupillary response while reading acuity chart
• Retinoscopy shows:
  • Fluctuating retinoscopy
  • Subjective end point may be unachievable due to constant refractive changes
• BV findings:
  • Reduced vergences
  • Significant phoria may be seen

Tests for Accommodative Dysfunction

• Refraction tests may useful
• Accommodative Amplitudes tests:
  • Donder's
  • Sheard's
  • BCC
  • MEM
• Accommodative Facility tests:
  • NRA
  • PRA
  • Flippers

Accommodative Insufficiency

• It is the most common accommodative problem, affecting approximately 85% of patients
• Symptoms consists of:
  • Blurry vision, headaches or asthenopia to near work
  • Patient reports symptoms 10-15min. after near work
  • Children tend to avoid reading while Young adults work but with less comfort and performance
  • Burning, irritation, photophobia or nausea are sometimes reported
• Signs include
  • Low amplitude of accommodation
  • 2.00D below the minimum AoA typically occurs
  • 5 to 6 diopters less than the expected average for the age
  • Higher lag of accommodation and low PRA (patient cannot stimulate accommodation)
  • Fails monocular and binocular flippers with minus lens difficulty
  • Tendency towards Convergence Insufficiency (CI)
• Typical ages ranges from school age to mid to late 20s
• After 35 y/o it is considered to be “premature presbyopia."

Accommodative Insufficiency (associated conditions)

• Associated Conditions:
  • Convergence Insufficiency
  • Emotional distress or fatigue
• Conditions that cause overall debilitation include:
  • Endocrine condition, especially if poorly controlled
• Decompression sickness “bends"
• Down Syndrome tend to have muscular hypotony and cerebral Palsy and ADHD
• Management:
  • Treat any underlying systemic condition if present
  • Correct any uncorrected refractive error
  • Plus lenses at near are important

Accommodative Insufficiency (Treatment)

• Prescribe plus lenses as: SV only near, or Bifocal at lower margin of the pupil or PAL 4mm above pupil margin
• Orthoptics such as Vision Therapy
  • Expected to increase 1.00D per week until patient reaches normal levels
  • Pencil Push Ups, Hart Charts both at distance and near
  • Increase PFV and NFV in office training

Accommodative Infacility

• Inadequate speed and accuracy
• Symptoms
  • Intermittent blur when change in point of focus occurs
  • Headache and Asthenopia at near is present
• Symptoms include:
  • Poor attention/concentration while reading and may report diplopia and fatigue
  • Poor facility of accommodation: May be the only sign
• Often fails flippers monocular and binocular can include difficulty with plus and minus lenses -Low NRA and PRA may also be present - Fluctuations during MEM or BCC test can exist without AoA and a normal lag
• Etiology is normally Unknown but has been associated with: Learning disabilities, Measles, Graves' Disease, Diabetes Mellitus, alcoholism, migraines, cerebral palsy, Adie's tonic pupil
• Treatment aims at performing: best refractive error correction, Flipper lens training and prescribe plus lenses on cases that have a positive response

III-Sustained Accommodation

• Blurry after prolonged near work & asthenopia occurs
• Symptoms usually includes Low PRA, (ability to relax accommodation), May cause failures in monocular and binocular flippers if not prescribed,
• Trouble with flippers may arise if trouble with lenses often appear.

Symptoms of Repeated Accommodative Testing

• Normally, AoA should provide some fatigue (after along period of time fatigue & blur", but these could change the case-history
• To accurately evaluate symptoms, be sure to repeat the testing protocols multiple times, especially with the lenses/test)
• Slow accommodation can be observed Other evaluations included but limited to at first evaluation with a normal to high lag via MEM & BCC

Sustained accommodations

• Treatment:
  • Correction of ametropia
  • VT for accommodation to Increase speed and tone
  • Plus lenses
• Etiology:
  • Stage of convalescence from a debilitating illness is commonly linked
  • In the stage of generalized tiredness, some side effects tend to occur as well. For example:
• Muscle fatigue is linked to small accommodations

Accommodative Excess

• Accommodative Excess (AE) is a greater than normal accommodative response for a given stimulus or demand resulting from over stimulation by the eyes.

AE effects: Occurance

• The problem is a result of prolonging near work and diminishes 10 minutes after ceasing the task
• Presents a wide variety of symptoms due to it's intermittent process

Accommodative Excess: Causes

• Young hyperopes accomidating or younger myopes excessive near work and convergence
• Patients with astigmastim are improperly fitted (or un-fitted) with spectical fit

Symptoms: - Intermittent blurred vision (especially at distance) - Asthenopia - Headaches

Accommodative Excess: Effects

• Have shown to have history of ineffective prescriptions or frequent changes, and change from Distrance to N/N to D

Accommodative Excess continued

• Spasm of Accommodation Signs:
  • Triad of convergence, over accommodation and miosis
  • Esophoria at near and possibly at distance
  • Psychogenic, strong miotic, Pilocarpine Psychogenic, strong miotic, iredocytelitus, brain lesion

Accommodative Excess (Treatment)

• Treatment:
  • Decrease near work as much as possible for several weeks
  • Correct with best SRx if ametropia Preferable when cycolorefraction or VT is emphaizedon accempting excess plus at and facility on or vision

Differential Diagnosis of Accommodative Dysfunctions

• Emerging myopia: rule out with cycloplegic refraction
• Spasm of accommodation/near reflex: worse than AE
  • Near triad present
• Accommodative paralysis: is usually related to illness, lead poisoning, head trauma
  • Be careful with unilateral presentation this is a sign of serious etiology!
• Binocular vision dysfunction: CI or CE can cause secondary accommodative dysfunction
• Uncorrected refractive error
• Streff syndrome: bilateral reduced VA, minimal RE, eventually improves to 20/20 with plano or low plus lenses, tubular VF at 1m and 2m

Treatment of Accommodative Dysfunction

• Plus for near normally for the eye, but exceptions can arise with Accommodative Spasm
• VT is utilized with an increased emphasis to improve vergence for the aily
• Ocluar hygiene for a 20-20-20 rule, and also: Harmon's Distance to avoid accommodating

Test your knowledge of binocular vision with these multiple-choice questions. Topics include: stereopsis, eye strain related to binocular vision, exophoria, adaptations to refractive error, visual field, strabismus, and the importance of visual skills beyond acuity. A detailed case history is also considered crucial for assessment.