13 - Nonorganic Ophthalmic Disorders

Question 1

Nonorganic Vision Loss

Answer 1

1. Substantial proportion of patients with actual organic disease may also exhibit superimposed nonorganic behavior

Question 2

Afferent Visual Pathway Bilateral NLP

Answer 2

1. Bilateral No Light Perception
   
   1. Patient’s inability to perform NONVISUAL tasks provides evidence of nonorganic vision loss
   2. Proprioceptive testing such as failure to sign paper or adequately perform finger-to-nose test (requires proprioception NOT vision) in absence of neurological disease should alert clinician to problems with patient cooperation
   3. Finger-touching
      
      1. Ask patient to touch fingertips of each hand together — truly blind person CAN still touch fingertips together
   4. Pupillary reaction
      
      1. Normal pupils suggests anterior pathways are intact however does NOT prove nonorganic vision loss — bilateral anterior visual pathways may be involved or pathways posterior to pretectal nuclei i.e. LGN, optic radiations, occipital cortex
      2. Aversive light reaction establishes some level of afferent input
   5. OKN drum
      
      1. If patient’s eyes move with drum then nonorganic vision loss established
      2. VA at least 20/400
   6. Visual Evoked Potentials
      
      1. Flash and pattern-reversal VEPs
      2. VEP with increased latency and decreased amplitude
      3. Abnormal pattern-reversal VEPs may NOT lead to diagnosis of non-organic vision loss — patient may use variety of techniques to suppress VEP (inattention, lack of concentration, defocusing, meditation
   7. Shock Value Test
      
      1. These include a variety of tests including the menace reflex where the examiner presents visual threats such as a closed fist and observes for blinking or flinching. The examiner can also suddenly drop an object to see if a patient will reflexively react.

Question 3

Afferent Visual Pathway Monocular NLP

Answer 3

1. RAPD
   
   1. Absence of RAPD in 1 eye increases likelihood of nonorganic vision loss
2. Base-out prism
   
   1. Place 4-6 base out prism in front of eye while both eyes open. Will cause eye to move toward apex (Light bends toward base and hits temporal retina – fovea moves to light temporally thus eye moves nasally). Will see conjugate eye saccade of both eyes followed by convergent movement of fellow eye back to foveation.
   2. Movement when prism placed over worse eye indicates vision in eye

Question 4

Afferent Visual Pathway Monocular NLP

Answer 4

1. Vertical Prism Dissociation Test — 4 base-down prism in front of GOOD EYE. Nonorganic vision loss will see 2 images from each eye dissociated. If actual organic vision loss then will see 1 image from good eye and unable or blurry image in bad eye

Question 5

Afferent Visual Pathway Monocular NLP

Answer 5

1. Fogging Test (Type of confusion test)
   
   1. Place a plus lens (≥+5.00D over the normal refractive correction) in front of the good/unaffected eye and a lens with minimal power over the affected eye. The patient is then asked to read the chart with both eyes. The patient may not realize that the unaffected eye is fogged and a patient with functional monocular visual loss often reads well with the “affected” eye.
   2. Paired cylinders can also be used. A plus cylinder and a minus cylinder of the same power are placed in parallel in front of the good/unaffected eye. While the patient reads the chart, the axis on one cylinder is rotated 10-15 degrees to fog the good/unaffected eye. If the patient continues to read the chart successfully, they are revealing adequate vision in the “affected” eye.

Question 6

Afferent Visual Pathway Monocular NLP

Answer 6

1. Duochrome Test
   
   1. The patient is given red-green glasses with the red lens over the affected eye. The patient is asked to read the red-green duochrome chart with both eyes. The eye behind the red lens is able to see letters on both sides of the chart, whereas the eye behind the green lens can only see letters on the green side of the chart. If the patient is able to read all of the letters, this demonstrates that the affected eye is able to read the letters displayed.

Question 7

Afferent Visual Pathway Monocular NLP

Answer 7

1. Polarized lens test — patient wears polarized lenses and reads a chart projected with corresponding polarized filters
2. Stereopsis
   
   1. Requires binocular vision. Any evidence of stereopsis demonstrates vision present in bad eye.

Question 8

Monocular Reduced Vision

Answer 8

1. Fogging test, duochrome test, polarized lens test may help obtain a quantitative visual acuity measurement if patient cooperative enough to continue reading
2. Color Plate Test
   
   1. Ability to read the colors indicates at least 20/400 vision in the affected eye.
3. Cycloplegic test
   
   1. For younger patients with the ability to accommodate, a cycloplegic test can be used. Place tropicaimide in only the good eye and saline in the affected eye. After accommodation is paralyzed, check the patient’s visual acuity at near with both eyes open. The patient may not realize that they are only reading with the affected eye and may demonstrate good near visual acuity. Caveat: high myopes will still have good near vision after cycloplegia (near reading focuses image on retina).

Question 9

Binocular Reduced Vision

Answer 9

1. Bottom-up acuity
   
   1. Bottom-up visual acuity testing: Begin with the smallest line (20/10 if available). Progressively increase the size saying that the size is “doubled” in size and express astonishment that the letters cannot be seen. This can often uncover better visual acuity than top-down visual acuity testing in patients with functional vision loss.
2. Visual Aids
   
   1. “Vision aids”: The patient is given trial frames with four lenses equaling the correct prescription and told that the lenses are special magnifying lenses. This may lead to improvement in visual acuity indicating a nonorganic component.
3. Near vision testing discrepancy
   
   1. A large discrepancy between near-visual acuity and distance acuity provides evidence of nonorganic disease.
4. Specialty charts
   
   1. Specialt charts with 20/50 optotype instead of 20/400 optotype may be useful in patients who can only read “top line” or

Question 10

Visual Field Defect - Automated Perimetry

Answer 10

1. Monocular and binocular visual field testing: If the patient reports a monocular visual field defect, the visual field test can be repeated with both eyes open. If the field defect is still present under binocular testing, the monocular defect can be assumed nonorganic. This can be done with confrontation visual field testing or with formal evaluation such as Humphrey or Goldmann visual field testing.

Question 11

Visual Field Defect - Confrontation Testing

Answer 11

1. Confrontation Testing
   
   1. The examiner asks the patient to count fingers in the “non-seeing” field and instructs to report “none” when none are seen. As the test progresses, the examiner changes to showing fingers silently. A patient response of “none” when the fingers are silently displayed in the “non-seeing” field confirms vision in that area.

Question 12

Visual Field Defect - Kinetic Perimetry

Answer 12

1. Nonorganic visual fields often demonstrate a spiraling field that becomes smaller as the test object is moved around the field. Crossing isopters or a visual field that remains the same size regardless of the size or brightness of the test stimulus (yielding isopters nearly one on top of another) is also often seen in functional visual field loss.

Question 13

Visual Field Defect - Tangent Screen Testing

Answer 13

1. A tangent screen test can be performed at two different distances from the screen (usually 1 and 2 meters) while maintaining the same ratio of target size to target distance (i.e., larger target at further distance). A patient with organically constricted visual fields will show an increase in the size of the visual field when moved to a farther distance while a patient with functional visual field loss will often report the same absolute size of the field (tubular or gun-barrel field).
2. A nonorganic tubular visual field can also be elicited with repeated confrontation visual field testing at 1 meter and at 2 meters from the patient.

Question 14

Ocular Motility and Alignment

Answer 14

1. Voluntary Flutter
   
   1. Sometimes misdiagnosed as nystagmus characterized by irregular brief bursts of rapid-frequency and low-amplitude eye movements with no slow phase
2. Gaze palsy
   
   1. Patient reported inability to move eyes may be overcome with variety of maneuvers including OKN drum, mirror tracking
3. Spasm of Near Reflex
   1.

Question 15

Pupils and Accomodation

Answer 15

1. Fixed and Dilated Pupil
   
   1. CN 3 palsy, Adie tonic pupil, pharmacologic blockade — may also occur because of inadvertent or purposeful application of mydriatic or cycloplegic drops; may also occur from touching fingers contaminated through use of scopolamine patch or touching certain plants with parasympatholytic chemicals
   2. Pilocarpine test — in pharmacologic blockade 1% pilocarpine cannot overcome the recepter blockade and pupil remains large. Dilute pilocarpine will constrict a dilated pupil in majority of patients with CN 3 palsy or Adie tonic pupil.
2. Changes in pupil size
   
   1. Widely dilated pupils may be observed in young patients most likely caused by increased levels of circulating catecholamines
   2. A few patients are able to voluntarily dilate both pupils
3. Changes in Accomodation
   
   1. Weakness or paralysis of accomodation soemtimes occurs in children and young adults even in presence of appropriate plus lens. If patient with normal distance vision fails to read despite near vision correction a nonorganic condition is possible

Question 16

Eyelid Position and Function

Answer 16

1. Ptosis
   
   1. Eyelid droop from nonphysiologic causes can be distinguished by position of brow. True ptosis = brow elevated as a patient tries to widen palpebral fissure. Nonorganic ptosis = orbicularis overactivity causes brow to be lowered; patients cannot simultaneously elevate eye and maintain a drooping eyelid thus in upward gaze ptosis will resolve (patient may not cooperate with EOM exam) — one can use thumb to manually elevate eyelid and patient will look upward and once thumb released ptosis “resolves” whereas if organic ptosis then ptosis returns once thumb released
2. Blepharospasm
   
   1. May be triggered by emotionally traumatic event and may cause nonorganic ptosis. Pressure over supraorbital notch useful in raising eyelids

Question 17

Management of patients with Nonorganic Vision Loss

Answer 17

1. Best managed with understanding and encouragement
2. Stress good prognosis which provides a way out and gives patient opportunity to recover
3. Important to schedule at least 1 follow-up as occasionally an organic disorder becomes apparent later and may be managed