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Teen reports decreasing vision in one eye
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A 16-year-old white male presented complaining of decreased vision in the right eye, which he had noticed for several weeks. He had gone to another optometrist, who did not find a problem and referred him to this office. The patient remembered an incident of blunt trauma to his eye during a basketball game recently and thought it might be connected. He denied any flashes of light, floaters or curtain encroaching on vision.
The patient’s family history was not significant for any ocular conditions other than cataracts. His personal history was unremarkable, as well, and he took no medications regularly. At the initial visit, visual acuities were 20/250 OD (pinhole no improvement) and 20/20-1 OS. No relative afferent papillary defect (RAPD) was observed. Intraocular pressures were 14 mm Hg OD and 12 mm Hg OS. The anterior segment evaluation revealed no abnormalities. During color vision testing, the patient correctly identified 0/10 plates with the right eye and 10/10 plates with the left.
Fundus photos indicated slight pallor of the optic nerve head temporally in the right eye, but they were otherwise normal. Optical coherence tomography revealed a below-average ganglion cell count nasally in the right eye, but a normal count in the left. The optic nerve head and retinal nerve fiber layer analysis returned normal results in both eyes. A central scotoma manifested in the visual field of the right eye. The left eye’s visual field was clear. A tentative diagnosis of traumatic optic neuropathy was made and the patient was referred to a neuro-ophthalmologist for further testing.
The next month, at an appointment with the neuro-ophthalmologist, the patient’s visual acuities were 20/400 OD and 20/40-2 OS. There was no RAPD, a slight electroretinography (ERG) abnormality (but it was generally normal), a large central visual field defect in the right eye, a small central visual field defect in the left eye and a normal-appearing fundus. An inability to fixate resulted in no visual-evoked potential (VEP) results. The patient correctly identified 0/8 plates with the right eye and 7/8 plates with the left. The presumed diagnosis was traumatic optic neuropathy. Lab tests were ordered, and the patient was to return in 6 weeks.
At the follow-up visit in 6 weeks, the patient complained of increasing difficulty seeing. His visual acuity had declined to 20/400 OD and 20/60 OD, with no RAPD. The lab results for CBC, basic metabolic panel, B12, folic acid, NMO antibody, ACE and ANA were all normal. Visual field defects appeared similar to the previous visit. Upon examination of the fundus, mild telangiectasia was visible on both optic nerves.
In an additional 2 weeks, the patient’s visual acuities had declined to counting fingers in the right eye and 20/400 in the left. He correctly identified 0/8 color plates with the right eye and 1/8 color plates with the left. Central visual field defects were present in both eyes. The fundus appeared unchanged. A different diagnosis was suspected, and the course of testing and treatment were changed accordingly. The new suspected diagnosis was soon confirmed. The timeframe of the visits described, from start to finish, was approximately 2 months.
Normal fundus appearance in the left eye.
Slight pallor of the optic nerve head temporally in the right eye.
Images: Clark S
A central scotoma manifested in the visual field of the right eye.
The ONH and RNFL analysis returned normal results in both eyes.
The GCC is below average nasally in the right eye, normal in the left.
The patient tested positive for a 11778 mutation, resulting in Leber’s hereditary optic neuropathy (LHON). LHON has a mitochondrial inheritance pattern, with at least 45 mutations. All female carriers will transmit the mutation, and males or females can be affected. It is possible to carry the mutation with no symptoms, thus producing no family history of the condition. Onset of symptoms is typically in the teens or 20s. Males are more likely to suffer vision loss.
Sarah Clark
Loss of vision in LHON patients is due to the degeneration of retinal ganglion cells and their axons. Researchers are uncertain as to whether environmental factors, such as smoking and alcohol use, may play a role. Central vision and color vision are most affected by optic neuropathy. The vision loss is typically severe and irreversible. After one eye begins to decline, the other eye is usually affected within several weeks or months.
There are few visible signs of LHON. When the patient presents acutely, peripapillary retinal telangiectasia is often extant, and the optic nerve may appear swollen. VEP will be abnormal, possibly prior to vision loss, whereas ERG will not be affected.
Idebenone is a drug from the quinone family that appears to have an antioxidant effect. Phase 3 clinical trials have been completed in Europe examining its outcomes in treating LHON. It is also used for Alzheimer’s disease and several neuromuscular conditions. Studies indicate that patients with certain mutations are more likely to respond to idebenone than others.
Hillary Smith
It is important for patients and their families to find strong a support group within the community. This can be a valuable resource, both for information and empathy. Genetic counseling also should be provided to the patient and the patient’s family, so they will understand the ramifications of its inheritance pattern.