A 45-year-old black male came into my office complaining of declining, unexplained vision loss for the past two years. His best-corrected visual acuity was 20/25 OD and 20/50 OS. His visual fields looked like glaucoma, but his optic nerves appeared normal. Where do I go from here?

“Take a closer look at the visual fields,” says Dennis Mathews, OD, a neuro-optometrist at Eye Specialty Group, in Memphis.

On first glance, the fields might appear to represent arcuate scotomas from glaucoma. But you can see that, in the right eye at least, the defects somewhat respect the vertical midline. “In glaucoma, we expect there to be no respect to the vertical,” he says. So, that’s one clue that you’re not dealing with glaucoma.

The second clue is that glaucoma usually doesn’t begin with bitemporal field loss, as shown in this patient’s visual fields, Dr. Mathews says. Glaucomatous field loss usually develops nasally and superiorly.

The third clue that this isn’t a straightforward case of glaucoma is that, despite 0.80 cups, the rim tissue is intact 360° and the cupping obeys the ISNT rule. “If these fields were caused by glaucoma, one would expect a notch or other damage consistent with the disease,” Dr. Mathews says.

In short, the appearance of the patient’s optic nerve head doesn’t correlate with the visual field loss. When that happens, it’s time to look deeper.

Because the field defects are temporal and symmetrical, “this should make you very suspicious of a retrobulbar problem, specifically at the chiasm,” Dr. Mathews says. “And the most common tumor is a non-secreting pituitary macroadenoma. Clearly, this patient requires neuro-imaging.”

If you’re comfortable managing such a case, order an MRI of the brain with and without contrast, Dr.
Mathews says. If you’re unable or not prepared to do that, you can refer the patient to a specialist.
In this patient’s case, the MRI came back showing a large suprasellar mass lesion consistent with a pituitary adenoma.

Send this patient to a neuro-surgeon for decompression surgery, Dr. Mathews says. “After decompression, many times you’ll see some improvement in vision, although the vision will never return to normal,” he says.

Unfortunately, this patient has not recovered much of his acuity or visual field after the surgery, but time will tell. This case highlights the importance of always explaining unexplained acuity loss, Dr. Mathews says.

Last but not least, be aware that the tumor can grow back, so monitor the patient with visual fields and a dilated fundus exam every six months, Dr. Mathews says.