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European Journal of Applied Sciences – Vol. 11, No. 2
Publication Date: April 25, 2023
DOI:10.14738/aivp.112.14552.
Ikonomov, L. M., & Kaufman, E. J. (2023). More Than Meets the Eye Evaluating Non-Organic Vision Loss. European Journal of
Applied Sciences, Vol - 11(2). 725-730.
Services for Science and Education – United Kingdom
More Than Meets the Eye Evaluating Non-Organic Vision Loss
Luben M. Ikonomov
New England College of Optometry
University of Virginia Department of Ophthalmology
Evan J Kaufman
University of Virginia Department Ophthalmology
Non-organic vision loss (NOVL), referred to as “functional vision loss”in the literature, is defined
as a decrease in either visual acuity or field of vision without an identifiable underlying organic
etiology.1,2 Suspected NOVL requires extensive chair time, increased hands-on care, and
reassurance with the patient. NOVL has been found to accompany other organic causes in about
15% of cases.3, 4 A diagnosis of NOVL should be made only after other organic causes of visual
loss are ruled out. This may require multiple tests of each part of the visual pathway – many of
which are subjective based on patient responses and may therefore yield inconclusive or
conflicting results.
PRESENTATION
NOVL is usually characterized as a type of conversion disorder, which can also include
disorders of gait and pseudoseizures.5 Conversion is a type of dissociative disorder and implies
that the symptoms are either acute neurologic weakness, such as diplopia or ptosis, or sensory
dysfunction, such as blur or the constriction of the visual field. 5, 6, 7 Pain is not a symptom.5, 7
NOVL can affect both children and adults, with an incidence of 1.75% being found in children,
and 5.25% in adults.3 In addition, women are affected more than men are in all age groups.5
NOVL has also been associated with lower socioeconomic status and poor education.5 The loss
of visual function is usually bilateral and symmetric.4 However, unilateral cases of NOVL have
also been reported, and it is characterized by more severe symptoms in the affected eye.5, 6 The
most commonly reported symptoms are blurry vision or a reduced range of the visual field.4, 5
NOVL can accompany an organic cause of vision loss, which may make diagnosis difficult.2, 5
About 15% of NOVL cases are associated with secondary organic causes of vision loss, 5 with
the presence of a central scotoma in visual field testing being the greatest predictor of organic
vision loss.4 The most common organic sources of vision loss that present alongside NOVL are
central serous chorioretinopathy (CSR) and pseudotumor cerebri.4, 5
EXAMINATION
NOVL is a diagnosis that should be made only after other causes of vision function have been
ruled out, and after the normal visual function of the afferent visual pathway has been
confirmed. 8, 9 This is challenging to do, however, due to the subjective nature of many of the
more commonly used sensory examinations. 5, 8
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VISUAL ACUITY
Alternative testing methods for measuring visual acuities can be done when NOVL is suspected
and an uncorrected refractive error is ruled out.4 A bottom-up approach to traditional visual
acuity, starting with the 20/15 or 20/20 line and going up, accompanied by plenty of
encouragement, can elicit a change or paradoxical responses to the best estimated visual
acuity.4 Comparing discrepancies between distance and near visual acuity can also pin down
changes in visual acuity throughout the exam.4, 9 If optokinetic nystagmus is observed during
optokinetic drum testing, the patient’s visual acuity is at least 20/400.4 If the patient is able to
see any of the numbers on the Ishihara plates during color vision testing, he or she has a near
visual acuity of at least 20/200 when the plates are held at the correct testing distance.9 In cases
of suspected unilateral NOVL, fogging the unaffected eye without the patient knowing can
provide a more accurate test of the visual acuity in the affected eye.4 An alternative to the
fogging method of visual acuity testing for unilateral NOVL is to measure visual acuity
binocularly using red-green glasses to block the unaffected eye without the patient realizing
this.2 The four-prism diopter reflex test (4-PRT) can be used to grossly assess stereo vision in
patients with suspected NOVL as well.2, 4
VISUAL FIELDS
Visual field testing should always be done on patients with suspected NOVL. During
confrontation visual field testing, patients often show full-field constriction in either one or
both eyes4. This test can further be modified by performing a finger-to-nose test while telling
the patient that the test will evaluate his or her coordination. (4) Goldmann visual field-testing
findings include spiraling, crossing, or the stacking of isopters. Automated perimetry cloverleaf
patterns with low-reliability indices are common8, 9. Repeated visual field testing over time can
show paradoxical changes in the size and shape of the constriction in NOVL patients.2
Most visual fields for patients with NOVL will be inconsistent and will favor gross defects.
Understanding if the patient is malingering or simply not paying attention can be difficult.
Backing up an automated visual field with a tangent screen can assure the practitioner of the
validity of the test. Performing a tangent screen test at three and six feet should reveal a
doubling of central vision in a situation of visual constriction. A true visual field defect will
sustain the same visual angle at both distances. Standing twice as far from the tangent screen
will give two times the visual field, causing the central normal vision to be twice as big. A
malingering patient will be confused and thus will yield a defect of the same area on the tangent
screen that does not double in size and does not maintain the same visual angle.
VISUAL EVOKED POTENTIALS & ELECTRORETINOGRAMS
Visual evoked potentials (VEP) or electroretinograms (ERG) are used to objectively test the
integrity of the afferent visual pathway.4, 8 Both full-field testing and multifocal testing localized
to only the portions of the visual field shown to be affected during perimetry testing have both
been shown to be successful.4, 8 Unfortunately, these tests are not easy to obtain in most clinical
settings.4
MANAGEMENT
NOVL is a distressing and a debilitating condition. However, not all patients with NOVL require
psychiatric evaluation.5 Indications for a potential referral for psychiatric evaluation include a
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Ikonomov, L. M., & Kaufman, E. J. (2023). More Than Meets the Eye Evaluating Non-Organic Vision Loss. European Journal of Applied Sciences, Vol
- 11(2). 725-730.
URL: http://dx.doi.org/10.14738/aivp.112.14552.
previous history of a psychiatric diagnosis,5 other behavioral impairment,5 or the failure of the
visual loss to resolve over time.5, 10 Other instances that require immediate reporting and
referral are suspected cases of child or sexual abuse.5, 12No current consensus has been reached
regarding the appropriate psychiatric management of NOVL, and therapy is usually determined
based on the suspected underlying cause of the disorder.5, 9 A literature review suggests that
the treatment of NOVL cases include reassuring the patient that the vision loss is real but will
get better over time, 3, 13, 14 or prescribing placebo visual exercises for the patient to perform at
home.12, 15 Currently, no studies in the literature suggest the efficacy of one treatment modality
over others for treating NOVL. 9, 16
CASE PRESENTATION
A 28-year-old Caucasian female presented with progressive vision loss since graduating from
high school 10 years ago. An initial comprehensive eye examination in 2012 revealed no
problems with her eyes or vision. Subsequent eye exams in 2017 and 2018 also elicited no
pathologic etiology with her eyes. The patient was referred to University of Virginia for a
complete visual evaluation by her primary care provider. She reported intermittent bouts of
monocular double vision persisting in either eye. The patient’s ocular history was negative for
any childhood vision problems, the patient had never worn glasses, or any corrective
procedures. Her medical history was positive for anxiety, Crohn’s disease, inflammatory
arthritis, irritable bowel syndrome, iron-deficiency anemia, and migraines. She was negative
for a history of trauma and her family history was unremarkable.
The entering uncorrected visual acuity in the right eye was 20/100, and 20/200 in the left eye.
No improvement of her vision with a pinhole was noted. Her best-corrected visual acuity was
20/80 in the right eye and 20/200 in the left eye. Her pupils were equal, round, and reactive to
light. Her extraocular movements (EOM) were smooth, accurate, full, and extensive in both
eyes. Her confrontational fields were full right eye (OD) and showed inferior-temporal
constriction in the left eye (OS). The patient’s color vision, measured with Ishihara plates, was
reduced to 7/14 OD and 7/14 OS. In addition, her intraocular pressure was 19 mmHg in the
right eye and 21 mmHg in the left eye when measured with rebound tonometry. A slit lamp
examination revealed that all anterior and posture structures were unremarkable in both eyes.
Her estimated Cup-to-Disc ratios were 0.30r OD and 0.30r OS.
Ancillary testing was unremarkable for both eyes. The patient’s central corneal thickness was
596 um and 580 um in the right eye and left eye, respectively. Her corneal topography showed
no irregularities with a Keratopathies of 42.16D spherical in the right eye and 42.49/42.01 toric
in the left eye. Pentacam corneal tomography with Belin/Ambrósio analysis showed no
thickening, ectasia, or irregularities in both eyes. In addition, no signs of anterior or posterior
elevation were found. The total D value (0.34 for the right eye and 0.08 for the left eye) showed
statistical normal rate curvature in the general population. A baseline retina nerve fiber layer
(RNFL) ocular coherence tomography (OCT) resulted in average thickness, with no cupping, no
significant signs of depression, and no pallor in either eye. A baseline macular thickness OCT
showed an average thickness of 237 um in the right eye, 236 um in the left eye, and a normal
foveal contour, and all layers were intact bilaterally. Fundus autofluorescence was
unremarkable, with no areas of marked hyper- or hypo-fluorescence found in the macula, optic
nerve head, or posterior pole.
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A baseline HVF 30-2 SITA Standard V was performed, with foveal sensitivity decreasing to 22
dB and 23 dB in the right eye and left, respectively. The test showed full-field constriction in
both eyes (OU) with an apparent minimal clover-leaf pattern and a high false negative rate in
both eyes (see Figure 1). 4
Figure 1. An HVF 30-2 SITA Standard V indicates full-field constriction OU with an excessively
high false negative rate and an apparent cloverleaf pattern OU.
Based on the patient’s history, clinical presentation, and testing, a tentative diagnosis of chronic
category 2 vision loss OU with a questionable psychosomatic component. A brain lesion and
rod-cone dystrophy were in the differential diagnosis. Magnetic resonance imaging (MRI) with
contrast was ordered along with a follow-up visit to perform a full-field electroretinogram
(ERG). A repeat field tangent screening was the next step in the patient evaluation.