Article

A mystery with no ‘physiologic basis’

The curious incident of visual deterioration years after pediatric cataract surgery.

A 9-year-old female presented for an additional opinion after nearly a year of progressively deteriorating vision of the right eye. She had multiple prior examinations by outside ophthalmologists and a significant, extensive ocular history.

The patient first presented to an ophthalmologist at age 4, after decreased visual acuity of the right eye was detected on a school-screening exam. She was found to have a posterior lens opacification with resulting visual acuity of 20/100, and shortly after diagnosis underwent cataract extraction with IOL placement. Over the course of the following year, she had three YAG capsulotomies for posterior capsular opacification and was subsequently noted to have a visual acuity of 20/20 with normal stereopsis and ocular alignment.

Approximately one year prior to presentation to us, the patient visited her ophthalmologist with complaints of decreased vision in the right eye. She underwent vitrectomy of the right eye in May 2016 for residual media opacities. She was noted to have fluctuating visual acuities, ranging 20/60 to 20/800 at multiple visits between May and December. Workup, including MRI brain, OCT macula and fluorescein angiography, revealed no underlying cause for her fluctuating decreased vision. Despite a minor adjustment in her glasses prescription and patching of the left eye, she continued to complain of decreased vision of the right eye.

The patient’s medical and surgical histories were otherwise unremarkable, and family history was noncontributory. The patient was in fourth grade at the time of presentation and doing well in school. A full review of systems was otherwise negative.

OUR TURN TO EXAMINE THE CLUES

Our examination revealed the patient to have CF vision in the right eye, 20/20 in the left. Her pupils were equal and reactive without a relative afferent pupillary defect. Visual fields were full to confrontation and she had full motility with ortho alignment of both eyes. On stereopsis testing, she had a positive fly at 2 cm, 3/3 animals and 6/9 circles. Initially, her color vision in the right eye was tested to be 0/11 with Ishihara plates, but on repeat testing of the right eye with coaching she was able to perfectly trace all numbers.

We noted the patient had a well-fixated, well-centered PCIOL with anterior capsular opening of 5 mm to 6 mm and posterior opening of 3 mm to 4 mm. We saw a small amount of peripheral cortical proliferation, greatest inferiorly and not encroaching on the optical center. Her fundus exam was normal. Her cycloplegic refraction revealed a 1-D myopic shift with minimal change in cylinder power and axis.

Having no organic explanation of her decreased vision, her visual acuity was retested. She was shown HOTV letters progressively increasing in size and instructed to take guesses. Her responses were wrong up to 20/600 with 30 consecutive wrong guesses ­— with 0.75 probability of being wrong on each guess, the probability of 30 wrong guesses is less than 0.0002.

“WHEN YOU HAVE ELIMINATED THE IMPOSSIBLE, WHATEVER REMAINS …”

We made a diagnosis of functional visual disturbance. Upon discussion with family, they took the diagnosis very graciously and noted that the patient can be very theatrical, having received a lot of attention at school for her extensive ocular history. A new glasses prescription was given; we instructed the patient to continue patching the left eye and that we expected the vision to completely recover soon. Upon follow-up, the patient described complete resolution of vision loss within one week after the initial visit.

THE PHENOMENON AFOOT

Functional visual disturbance, also called nonorganic or nonphysiologic vision loss, is defined by decreased vision or a visual field defect with no underlying physiologic basis.1 It accounts for 1% to 5% of referrals to ophthalmology.2,3 Research indicates that initial medical workup of these patients is greater than $500, and that millions of dollars are spent on fraudulent disability claims due to this disease.4

The disturbance can either be conscious and purposeful, as in the cases of disability or malingering, or it can be unconscious, such as somatization or conversion disorder or accompanying true organic disease. Distinguishing between bilateral and unilateral functional impairment can aid in assessment of behavior, use of different diagnostic strategies and expected secondary gains and recovery. The aim of evaluation of these patients is to confirm that the vision is better than what is claimed.3

For a claim of total binocular blindness or severely decreased vision in both eyes, information can be gathered just by observing the patient interact with her environment. Assessment of response to tasks that require proprioception as opposed to visual clues can be very telling. Nonsuppressible nystagmoid movements can be appreciated using mirrors or moving striped material, indicating a visual acuity of at least light perception and 20/400 respectively.1,3

A claim of monocular visual loss is more common, and assessment should focus on testing that requires binocularity and ocular viewing confusion principles.3 Pupillary response, stereopsis testing and gradual fogging or use of prisms over the “good eye” while testing vision with both eyes open often establishes the diagnosis.

Formal perimetry testing can be very useful, showing tunneling of the visual field or spiraling, crossing or stacking on a kinetic field.1,3 Other specialized testing to consider to rule out organic pathology includes OCT for optic nerve or macular pathology, FA or autofluorescence for subtle macular pathology, ERG, VEP or MRI.

In our case, with HOTV visual acuity testing, we could have gone smaller with test letters — opposite of what we did — until the patient started getting some correct; this would have been the level at which she really could not see them. This method has the added advantage of actually yielding a visual acuity.

KEEP FURTHER DISTURBANCES AT BAY

Many of these patients have triggers such as psychosocial events, trauma or psychiatric illness.5 Stressing a good prognosis and providing a way out for the patient helps to resolve all visual symptoms in 45% to 78% of cases.3,6 Follow-up should be sought to maintain good rapport and for any necessary re-examination to continue to look for coexistent organic disease. OM

REFERENCES

  1. American Academy of Ophthalmology. The patient with nonorganic ophthalmic disorders. Basic and Clinical Science Course: Section 5 - Neuro-ophthalmology, Chapter 13. 2016.
  2. Bose S, Kupersmith MJ. Neuro-ophthalmologic presentations of functional visual disorders. Neurol Clin. 1995;13:321-339.
  3. Chen CS, Lee AW, Karagiannis A, Crompton JL, Selva D. Practical clinical approaches to functional visual loss. J Clin Neurosci. 2007;14:1-7.
  4. Keltner JL, May WN, Johnson CA, Post RB. The California syndrome. Functional visual complaints with potential economic impact. Ophthalmology. 1985;92:427-435.
  5. Lim SA, Siatkowski RM, Farris BK. Functional visual loss in adults and children patient characteristics, management, and outcomes. Ophthalmology. 2005;112:1821-1828.
  6. Thompson HS. Functional visual loss. Am J Ophthalmol. 1985;100:209-213.

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