Optometrist refers woman for changes on Humphrey visual field test

A superior arcuate scotoma was detected in the left eye, and a full visual field was noted in the right eye.

Jeffrey Chang

Vivek Chaturvedi

A 29-year-old African-American woman was referred to the glaucoma service at the New England Eye Center after an optometrist noted changes on a screening Humphrey visual field examination.

The patient did not note any change in her vision and denied photopsias, floaters, pain or discomfort. She denied any history of trauma. Of note, she was evaluated for glaucoma as a child, but had no recollection of the results of the evaluation. Ocular history was significant for myopia and allergic conjunctivitis; she had mild seasonal allergies and took an oral contraceptive pill. There was a questionable family history of glaucoma in her paternal grandmother. Review of systems was unremarkable. She worked as a psychologist and denied smoking or drug use.

Examination

On examination, visual acuity was 20/20 in the right eye and 20/20 in the left eye with a mild myopic correction, –1.00 –0.50 × 110 in the right eye and –1.00 sphere in the left eye. IOPs were 14 mm Hg in the right eye and 13 mm Hg in the left eye by applanation tonometry. Extraocular movements were full. Pupils were equal and reactive with no afferent pupillary defect. Pachymetry measurements were 566 µm in the right eye and 553 µm in the left eye.

Figure 1. The right optic disc was essentially normal (left). The left optic disc was moderately larger than the right, with a sharp border, temporal pigmentary changes and a large atrophic area in the inferior and temporal regions (right).

Figure 2. Humphrey visual field 24-2 SITA standard. Right eye: full visual field. Fixation losses 0/13, false positives 0%, false negatives 0%, duration = 4:48 (left). Left eye: superior arcuate scotoma. Fixation losses 0/17, false positive 0%, false negatives 1%, duration 6:15 (right). Images: Landmann D, Krishnan C

Figure 3. OCT measurements and images of the right and left eyes.

Anterior segment examination was unremarkable. Gonioscopy revealed both angles open to the ciliary body band 360° with only a few iris processes and very light trabecular meshwork pigment. Examination of the macula, vessels and retinal periphery was unremarkable. Color photos of the patient’s optic nerves are shown in Figure 1. The right optic disc was essentially normal. The left optic disc was moderately larger than the right, with a sharp border, temporal pigmentary changes and a large atrophic area in the inferior and temporal regions.

Review of repeat 24-2 SITA standard Humphrey visual field test revealed a superior arcuate scotoma in the left eye and a full visual field in the right eye (Figure 2). Optical coherence tomography of the retinal nerve fiber layer revealed that the average thickness was 121 µm in the right eye and 110 µm in the left eye with good contour in both eyes (Figure 3).

What is your diagnosis?

Humphrey visual field test

The differential diagnosis for such a presentation includes glaucoma and congenital optic nerve coloboma, as well as other congenital nerve anomalies.

Although the patient is African-American, she is particularly young for primary open-angle glaucoma, with normal, symmetric IOPs.

The appearance of a large excavated area of the optic disc with a peripheral rim of normal neural tissue is most consistent with an optic disc coloboma. Congenital pits generally appear as a round or oval pit that is darker than the surrounding disc tissue. Colobomata are often found inferotemporally, and the disc is usually larger than the contralateral disc. Tilted discs are fairly common. On examination, one can see an oblique entrance of the optic nerve into the globe. This is often mistaken for papilledema and has a higher prevalence in patients with high myopia or moderate oblique astigmatism.

Optic nerve hypoplasia may be either unilateral or bilateral. Findings include markedly poor visual acuity, an afferent pupillary defect, various visual field defects and a small disc with a halo of hypopigmentation that is secondary to a chorioretinal pigment epithelial abnormality, known as the “double ring sign.”

Morning glory discs are rare dysplastic colobomas of the optic disc that resemble a morning glory flower. The disc is enlarged and contains persistent hyaloid remnants within the base. Blood vessels can be seen emerging from the rim of the disc in a radial pattern. The disc is surrounded by an elevated annulus of chorioretinal pigment changes.

Findings of a staphyloma are deep fundus excavations surrounding the optic disc, which may be normal or pale.

The findings of normal angle structures and otherwise normal ocular examination with supporting imaging modalities are most consistent with the diagnosis of optic nerve coloboma.

Discussion

Ocular colobomas are the result of an error in embryogenesis. They can affect any layer of the eye. There are a multitude of etiologies, and visual prognosis is related to location, extent and associated features.

The incidence of ocular colobomas varies, depending on the study population, between 0.22 per 1,000 to 0.7 per 10,000. During the fifth to seventh week of fetal development, the choroidal fissure typically closes. Failure to close anywhere along the fissure results in a coloboma. Typical colobomas are found in the inferonasal quadrant because of the orientation of the closing fissure. Conversely, colobomas found anywhere other than the inferonasal quadrant are termed atypical. The fissure begins to close centrally at 5 to 6 weeks of gestation. When the most anterior aspect of the optic stalk fails to close, the result is an optic disc coloboma.

Colobomas of the optic disc present as large bowl-shaped excavations with a peripheral rim of normal neural tissue present superiorly. The visual prognosis is related to the extent of the colobomatous defect, and unlike glaucomatous visual field loss, generally remains stable. Colobomas are also associated with various ocular findings such as microphthalmia, microcornea, nonrhegmatogenous retinal detachment, strabismus and cataract. It is important to remember that colobomatous defects of the optic disc can be associated with congenital forebrain anomalies. In turn, these may present as a mass in the medial portion of the upper lid. Biopsies of these lesions should be avoided.

Management

Ophthalmic management should include a complete ophthalmic examination, which might necessitate general anesthesia in infants. Care should be taken to refract the patient, as high levels of anisometropia may exist and correction of the abnormal hypermetropic eye may alleviate accommodative esotropia. CT or MRI is useful to define associated central nervous system malformations as well as delineate possible microphthalmia. Older patients should be followed with visual field examinations. In the case of unilateral colobomas, monocular precautions should be stressed. While part-time occlusion therapy is unlikely to help, a short trial may be warranted. Low-vision evaluation and aids should be offered when necessary. Much of the care should be geared toward counseling the parents.

Case continued

The patient was counseled on her condition. Because she has a relatively asymptomatic visual field defect but excellent central visual acuity, she was advised to follow up on a yearly basis.

References:

• Dutton GN. Congenital disorders of the optic nerve: excavations and hypoplasia. Eye. 2004;18(11):1038-1048.
• Gregory-Evans CY, Williams MJ, Halford S, Gregory-Evans K. Ocular coloboma: A reassessment in the age of molecular neuroscience. J Med Genet. 2004;41(12):881-891.
• Onwochei BC, Simon JW, Bateman JB, Couture KC, Mir E. Ocular colobomata. Surv Ophthalmol. 2000;45(3):175-194.

• Dan Landmann, MD, and Chandrasekharan Krishnan, MD, can be reached at Tufts Medical Center, 750 Washington St., Box 450, Boston, MA 02111; 617-636-4219; fax: 617-636-4866; Web site: www.neec.com.

• Edited by Jeffrey Chang, MD, and Vivek Chaturvedi, MD. Drs. Chang and Chaturvedi can be reached at New England Eye Center, Tufts University School of Medicine, 750 Washington St., Box 450, Boston, MA 02111; 617-636-4219; fax: 617-636-4866; Web site: www.neec.com.