CLINICAL CHALLENGES
The Red Herring
Sometimes you have to go beyond the obvious to find what's important.
By Eric Schmidt, O.D.

Many cases arise in which a patient presents with a symptom that has nothing to do with his actual problem; or worse yet, with a symptom that actually masks a more serious condition. The following is one of those cases where the "squeaky wheel" doesn't necessarily need the oil.

Learning about the patient

At the end of another typically hectic day, I grabbed the chart of my last patient, C.F. (another "emergency" work-in), and read about her complaints. Not surprisingly, once I read the first sentence, I realized that C.F. probably could've waited for a scheduled appointment.

The chief complaint read "For about six weeks, the patient sees "designs" to her left." I chuckled at the apparent nonemergent situation and continued reading. C.F.'s history stated that she saw the designs with each eye and that they were consistently situated on her left side. The designs began as gray, but over the past two days, they had a yellowish and pinkish hue to them.

C.F. also told my assistant that she doesn't notice these things all the time, but that for the past few days they appeared much more frequently. I checked her visual acuity (VA) and realized that my skepticism regarding this "emergency" may have been groundless. My assistant measured C.F.'s VA as 20/30 OD and 20/40-2 OS. The OD didn't improve with pinhole occlusion and the OS improved to only 20/30 with the pinhole occluder.

Amsler grid for both eyes. The shaded area represents the relative scotoma that the patient was seeing.

Meeting C.F.

I entered the exam room and asked C.F. some more specific questions in hopes of pinpointing the etiology of her complaints. I asked her if she felt she was seeing as well as she normally did. She replied that it seemed that her vision had gotten worse, especially over the last two weeks. She denied any pain or discomfort and, when I asked her specifically, said that the designs seemed to move.

I also asked her about her history of migraines, which she had noted in her information sheet. She said she hadn't had a migraine in about 10 years and that this didn't seem anything at all like her previous episodes. She once again denied any head or ocular pain and noted no dizziness or paresthesia. C.F. had just turned 65 and appeared quite vital and healthy. She took only fexofenadine with pseudoephedrine p.r.n. for allergies and rofecoxib for arthritis.

Searching for a clue

C.F.'s pupils were round, 6 mm in size and reactive to light OU. I noted no afferent pupil defect. Extraocular muscle testing showed no restriction in any direction of gaze with no pain on movement. Confrontation visual field testing wasn't completely normal, however.

When I asked C.F. if she could see all the parts of my face with her left eye covered, she noted a dark area starting at my right cheekbone and extending out toward my right ear. When I presented fingers in the quadrants, she could see them completely, but when I moved my finger from her inferior nasal quadrant superiorly, the finger disappeared when I approached the horizontal midline of her field. Similarly, when she covered her OD and looked at my nose with her left eye, she noted a black area extending from my right eye to inferior to my right cheekbone. Also on confrontation with my fingers, C.F. consistently missed my finger when I presented it to her left superior quadrant. I mapped out these scotomas using an Amsler grid OU (see figures on page 28) and I also made a note in my chart about a possible left hemianopsia.

Next, I wanted to attempt to improve C.F.'s VA. More plus power and some against-the-rule cylinder in both eyes improved her VA to 20/20-2 OD and 20/25+2 OS. Slit lamp exam revealed healthy anterior segments OU. Particularly, no anterior chamber reaction and no cataracts OU were evident. IOPs were 13 mmHg OD and OS. Before I dilated C.F., I performed a red cap test, which was negative for any desaturation OU.

Finding a PVD

I examined C.F.'s retina with a direct ophthalmoscope and with 78D and 20D lenses. Other than a small posterior vitreous detachment (PVD), the retinal grounds were normal OD. When I examined the OS, I saw a nebulous PVD eight to 10 disk diameters in size directly over the macula and optic nerve head. I didn't notice any macular edema. I looked carefully for any associated retinal tears, holes or detachment but found none. I noted an area of tufted retina in the inferior periphery, but again no tear or hole. No retinal or vitreous hemorrhage was evident.

C.F. had a large PVD, which in most cases a patient would notice and would report symptoms. My first thought was to blame her symptoms on this PVD based mainly on the sheer magnitude of the detachment. But something didn't make sense.

C.F. specifically said that the visual phenomena she sees is in both eyes, yet she only had a small, clinically insignificant PVD OD. Also, the confrontation visual fields and Amsler grid tests showed bilateral relative scotomas. A unilateral PVD, no matter what its size, wouldn't cause bilateral symptoms.

Automated visual field results on C.F. depicting left homonymous hemianopsia. The defect is mild and incongruous, but repeatable and valid.

Still searching for a cause

Even though I wasn't sure what was causing C.F.'s symptoms, I felt confident that an acute underlying process wasn't the culprit. The symptoms had been present for six weeks (although they seemed to be worsening) and her vision was improvable OU. The visual field cuts bothered me more than the PVD, and so I scheduled her for a formal automated visual field analysis in two days. C.F. reliably performed a 120-point, 60-degree suprathreshold field test, which tests out to 60 degrees and is efficient for identifying pattern-type defects. The VF results showed a cluster of depressed points beginning at fixation OD and moving nasally out to 40 degrees.

The OS revealed a similar but smaller defect beginning centrally and moving temporally out to 20 degrees (see figures above). Central, 24-degree threshold testing confirmed this left homonymous hemianopsia, which involved the left field of each eye and respected the vertical meridian. Posterior fossa lesions cause homonymous hemianopsias and these lesions affect axoplasmic flow anywhere from the post-chiasm to the occipital lobe.

Finding a resolution

I asked C.F. if she felt bad or weak and whether she had headaches or any neurologic symptoms. She denied any other problems, stating that only her eye was bothering her. Concerned that she might be harboring a brain tumor based on the hemianopsia and relative lack of any other symptoms, I ordered magnetic resonance imaging (MRI) of the brain with and without contrast.

The MRI revealed a subacute, enhancing infarct of the right occipital lobe, which is consistent with her VF results. I discussed the results with C.F. and referred her to her internist for a stroke workup. The internist found her to have hypercholestero-lemia, but she was otherwise relatively healthy. Her VA has improved to 20/20 OU with new glasses. C.F.'s "designs" that she noted months ago are attribut-able to the cerebrovascular accident and those have become much less apparent to her.

Contributing Editor Dr. Schmidt is director of the Bladen Eye Center in Elizabethtown, N.C. E-mail him at schmidtyvision@bellsouth.net.