Patient reports ‘gray spot’ in the middle of his vision

Issue: March 2012

ByMichael E. Feeser, OD, FAAO

A 42-year-old white male reported to the eye clinic with complaints of a gray spot in the center of his vision in his left eye for the last 2 days. Additionally, the patient reported pain in his “eye socket” in his left eye when looking to the extreme left and the extreme right. No other physical complaints were noted.

He said he took one tablet of ezetimibe/simvastatin 10/40 mg for hypercholesterolemia and 81 mg of aspirin for preventive heart health and used ketoconazole 2% topical shampoo for dandruff. All medications had been prescribed for at least 2 years. Additionally, he reported being an avid deer hunter; he said he was out in the field hunting several times over the last few months. He did not recall being bitten by a tick nor had he noticed any sort of “bulls-eye” lesions anywhere on his body.

The patient’s best corrected visual acuity was 20/20 in the right eye and no light perception centrally in the left eye.

Extraocular muscles in both eyes exhibited a full range of motion, with discomfort in the “back of left eye” noted when looking to the extreme right and left. Confrontation fields were full to finger counting in both eyes. Pupils were equal, round and reactive to light with no detectable afferent pupillary defect. IOP was 14 mm Hg in each eye. Slit lamp examination of the anterior segment was unremarkable in both eyes.

A dilated fundus exam was performed, which revealed that the optic nerve in the left eye had a swollen appearance with indistinct borders noted on the nasal aspect. The right optic nerve was normal in appearance. A spontaneous venous pulsation was observed in both eyes.

I ordered a 30-2 SITA FAST visual field test of both eyes. The right visual field showed an overall mild depression of visual sensitivity, while the left eye showed significant visual field defects, especially in the central vision area.

I ordered an optical coherence tomography scan of the optic nerves of both eyes, which further demonstrated significant thickening of the neuroretinal rim in the left eye. Average neuroretinal rim thickness of the optic nerve in the left eye was 800 µm while the neuroretinal rim thickness in the right eye was 400 µm. Significant thickening of the nerve fiber layer in the left eye was noted in the superior and nasal quadrant.

What is your diagnosis?

Gray spot

Differential diagnoses include: ischemic optic neuropathy, acute papilledema, severe systemic hypertension, orbital tumor compressing the optic nerve, intracranial mass compressing afferent visual pathway, Leber’s hereditary optic neuropathy and toxic optic neuropathy. Based on clinical signs and symptoms and current findings, I diagnosed the patient with optic neuritis.

Inflammation, demyelination

Most patients who present with demyelinating optic neuritis are between 20 and 45 years of age. The presumed pathology of optic neuritis is inflammation and demyelination of the optic nerve. Activated peripheral T cells migrate across the blood-brain barrier and release inflammatory mediators, which leads to neuronal death and axonal degeneration.

Optic neuritis can be subclassified into four categories based on the site of involvement: retrobulbar optic neuritis in which the optic nerve has a normal appearance; papillitis, in which the optic disc is swollen; perineuritis, which involves the optic nerve sheath rather than the optic nerve parenchyma; and neuroretinitis, which includes the classic “star” figure of macular exudates alongside optic nerve edema.

Retrobulbar neuritis and papillitis are most often associated with multiple sclerosis, whereas perineuritis and neuroretinitis are more often associated with an infectious or inflammatory etiology. The incidence of optic neuritis is highest in those populations located at the higher latitudes (e.g., northern United States and Southern Australia), which suggests that there may be a connection to lower levels of sun exposure and an associated vitamin D deficiency. Whites of northern European descent are eight times more likely to develop optic neuritis than are blacks and Asians.

Treatment

In the Optic Neuritis Treatment Trial, treatment with intravenous methylprednisolone resulted in a more rapid rate of visual recovery, which can be important for monocular patients, patients with significant bilateral loss and those with occupations requiring high levels of binocular acuity. However, the visual outcome is the same at 6 months for patients treated with IV methylprednisolone as compared to those who are not treated.

Several small studies have demonstrated that simvastatin can provide positive therapeutic effects for patients diagnosed with optic neuritis, as well as potential therapeutic uses for multiple sclerosis.

Risk of multiple sclerosis

In the absence of any lesions on a baseline brain MRI, patients with optic neuritis have a 25% chance of developing multiple sclerosis (MS) within 15 years. With the presence of one lesion, that probability jumps to 60%. Vitamin D levels less than 30 ng/mL have also been shown to positively correlate with an increased risk of developing multiple sclerosis. In one study dealing with a white population, the risk of developing MS was 51% higher for individuals with 25-hydroxy vitamin D levels less than 30 ng/mL as compared to individuals with levels greater than 40 ng/mL.

Effect on the nerve fiber layer

OCT provides an objective means to quantify the amount of axonal loss in the nerve fiber layer as a result of optic neuritis. In one study, 74% of patients with acute optic neuritis demonstrated thinning in the nerve fiber layer within 3 months of the initial event.

Patient management

I diagnosed the patient with papillitis in the left eye and discussed the option of IV steroid treatment. The patient opted not to pursue that treatment. I ordered an MRI of the brain and orbit without and with contrast, which revealed focal central enhancement involving insertion of the left optic nerve in the left eye, but no white matter lesions of the brain or intracranial masses.

I also ordered 25-hydroxy vitamin D levels and lab tests to screen for antibodies to Borrelia burgdorferi, Anaplasma phagocytophilium and Ehrlichia chaffeensis, all potential sources of Lyme disease. The Lyme antibody tests came back negative. However, his vitamin D level was 9.5 ng/mL, indicating a significant vitamin D deficiency.

I started him on OTC vitamin D, 5,000 IU tablets daily, and in conjunction with his primary care provider I began 50,000 IU D2 (ergocalcife) caps weekly. I referred him to his primary care manager for a complete physical. The patient was followed weekly with optic nerve OCT scans and visual fields, and I ordered repeat vitamin D blood tests in 3 months.

References:

Arnold A. Evolving management of optic neuritis. Am J Ophthalmol. 2005;139(6):1101-1108.

Costello F. Evaluating the use of optical coherence tomography in optic neuritis. Multiple Sclerosis International. March 22, 2011, doi:10.1155/2011/148394.

Germann CA, Baumann MR, Hamzavi S. Ophthalmic diagnoses in the ED: Optic neuritis. Am J Emerg Med. 2007;25:834-837.

Johnston MV. Demyelinating disorders of the CNS. In: Kliegman RM, Behrman RE, Jenson HB, Stanton BF, eds. Nelson Textbook of Pediatrics, 18th ed. Philadelphia: Saunders Elsevier; 2007.

Munger KI. Serum 25-hydroxyvitamin D levels and risk of multiple sclerosis. J Am Med Assoc. 2006;296:2832-2838.

Pau D, Zubidi NA, Yalamanchili S, Plant GT, Lee AG. Optic neuritis. Eye. 2011;25:833-842.

Phillips PH, Newman NJ, Lynn MJ. Optic neuritis in African Americans. Arch Neurol. 1998;55:186-192.

Soderstrom M, Link H, Sun JB, Fredrikson S, et al. Autoimmune T cell repertoire in optic neuritis and multiple sclerosis. J Neurol Neurosurg Psychiatry. 1994;57:544-551.

Michael E. Feeser, OD, FAAO, is an active duty naval officer serving as the head of the Optometry Department at the Naval Health Clinic in Patuxent River, Md. In this position, he has served as the chair of the medical staff for 43 multispecialty providers in four Navy medical branch clinics. Dr. Feeser can be reached at Huntingtown Vision Center, 28 Cox Road, Huntingtown, MD 20639; (410) 414-9456; fax: (443) 550-3508; drfeeser@huntingtownvisioncenter.com.

Edited by Leo P. Semes, OD, a professor of optometry, University of Alabama at Birmingham and a member of the Primary Care Optometry News Editorial Board. He may be contacted at 1716 University Blvd., Birmingham, AL 35294-0010; (205) 934-6773; fax: (205) 934-6758; lsemes@uab.edu.