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Man experiences bilateral photosensitivity and decreased vision after cataract surgery
Examination found bitemporal visual field loss with bilateral cecocentral depression.
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A 75-year-old man was referred to the New England Eye Center for progressively decreasing vision. He complained of photosensitivity, poor near and distance vision, and decreased color vision in both eyes since having uncomplicated cataract surgery in the right eye approximately 6 months previously. His symptoms started in the right eye initially and then progressed to involve the left eye.
His ocular history was otherwise significant for a distant history of right eye trauma without loss of vision and a cataract in the left eye. His medical history was remarkable for hypothyroidism, gout, diabetes mellitus, hypertension, chronic obstructive pulmonary disease, sleep apnea and low testosterone. He had a 35 pack-year history of smoking but quit several years ago, and he denied alcohol use. His family history was significant for heart disease, diabetes mellitus and Alzheimer’s disease.
Examination and testing
On presentation, the patient’s best corrected vision was 20/200 in the right eye and 20/800 in the left eye. His pupils were mildly reactive without a relative afferent pupillary defect, and his IOP was 15 mm Hg in the right eye and 17 mm Hg in the left eye. He identified no Ishihara color plates in either eye. Extraocular motility was full in both eyes.
Figure 1. Humphrey Visual Field testing showed bitemporal field loss with bilateral cecocentral depression involving fixation.
Images: Williams SL, Hedges TR
Figure 2. Fundus image of the right eye (left) showed a normal-appearing optic nerve, peripapillary atrophy and mild foveal retinal pigment epithelium changes. The left eye (right) showed a normal optic nerve and mild foveal retinal pigment epithelium changes.
Figure 3. OCT of the retinal nerve fiber layer showed mild nerve swelling.
A 24-2 Humphrey Visual Field showed bitemporal loss with bilateral cecocentral depression, worse in the left eye (Figure 1). Anterior segment exam of both eyes was relatively unremarkable except for a posterior chamber IOL in the right eye and a moderate nuclear sclerotic cataract in the left eye. Posterior segment exam was significant for peripapillary atrophy of the right eye, normal-appearing optic nerves in both eyes without hyperemia, telangiectasis or atrophy, and mild foveal retinal pigment epithelium changes in both eyes (Figure 2). Optical coherence tomography of the retinal nerve fiber layer showed mild thickening in both eyes (Figure 3). OCT and fluorescein angiography of the macula were unremarkable.
What is your diagnosis?
Bilateral vision loss
The differential diagnosis of bilateral vision loss in an elderly man, in the absence of obvious intraocular pathology, suggests optic neuropathy.
The bitemporal nature of the visual field defect is consistent with a compressive lesion at the optic chiasm, such as pituitary adenoma, craniopharyngioma, aneurysm, metastasis or lymphoma. In the absence of compressive optic neuropathy, this presentation is concerning for autoimmune retinopathies, such as cancer-associated retinopathy (CAR) and melanoma-associated retinopathy (MAR). CAR is typically associated with an extinguished electroretinogram, while MAR shows decreased scotopic B-wave amplitudes. Toxic, nutritional and hereditary optic neuropathies should also be considered. Toxic optic neuropathy has been associated with substances such as ethambutol, amiodarone, lead, methanol, isoniazid, cyanide and carbon monoxide. Nutritional optic neuropathy occurs in the setting of prolonged poor nutrition and chronic alcohol consumption, leading to B1, B12 or folate deficiency. Our patient reported having a healthy diet and denied any systemic exposures to toxic substances. Hereditary optic neuropathies such as Leber’s hereditary optic neuropathy (LHON) and Kjer’s autosomal dominant optic atrophy are also on the differential, although less likely given our patient’s age and lack of family history.
Diagnosis and management
Our patient had an unremarkable MRI of the brain and orbits. In addition, his vitamin B12 level was within normal limits. ERG testing showed mildly reduced scotopic amplitudes in both eyes but was otherwise normal. Genetic testing for CAR and other paraneoplastic syndromes was negative. However, upon further review of his case, testing was done for LHON. This was positive for the 14484 mitochondrial DNA mutation. At his most recent follow-up visit, the patient had visual acuity of 20/400 in the right eye and 20/200 in the left eye. He was started on idebenone and was referred for low vision services.
Discussion
Leber’s hereditary optic neuropathy typically begins with acute onset of painless monocular vision loss. Vision loss is central, occurring in the second eye within weeks to months or even years later. Visual acuity can vary widely but is usually severely decreased (less than 20/200) and symmetric between the two eyes. Loss of color vision is often more pronounced than visual acuity. In contrast, patients with toxic or nutritional optic neuropathy typically experience concurrent bilateral vision loss that is slowly progressive. Visual field testing may show mild abnormalities progressing to dense cecocentral scotomas. Pupillary reaction is usually normal.
Classic fundus findings in LHON include optic disc hyperemia or swelling (without leakage on fluorescein angiography), peripapillary telangiectasis and vascular tortuosity. However, the fundus may have a normal appearance in more than 40% of cases, especially in the early period after vision loss occurs. OCT findings have suggested that retinal nerve fiber layer thickening can occur in the presymptomatic stage of the disease. With time, however, papillomacular bundle atrophy and temporal optic disc pallor develop.
LHON results from a single base-pair nucleotide mutation of mitochondrial DNA, most commonly at the 11778 position and less commonly at the 3460 or 14484 position. This leads to impaired adenosine triphosphate production and chronic increases in reactive oxygen species, which is thought to result in cell degeneration. Patients may experience slight visual recovery over time, occurring most frequently with the 14484 mutation (65%) and least frequently with the 11778 mutation (4%). The disease shows maternal inheritance and typically affects boys and young men between the ages of 10 and 30 years; however, women account for 10% to 20% of cases. New diagnoses have rarely been made in patients older than 50 years. It is unclear why boys and young men are more likely to be affected or if a precipitating event leads to the onset of symptoms.
Although, there is no proven treatment for LHON, coenzyme Q, succinate, idebenone and other antioxidants have been used to increase mitochondrial energy production. Avoiding potential mitochondrial stressors, such as tobacco and excess alcohol, is also advised.