Eye Detectives

Dr. Emily Gorski and the Vision Functions Clinic solve diagnostic mysteries

Story By Gordy Slack. Illustration by Paul Blow.

The Vision Functions Clinic (VFC) is no noir, wood-paneled, 12th-floor detective’s suite dotted with overflowing ashtrays. It’s bright and open, modern, and clean. Smoking is verboten. Nonetheless, Emily Gorski, OD, the clinic’s chief, does see her mission as something like that of a private eye, bringing both investigative technologies and her own determination and deductive powers to bear on difficult-to-diagnose cases of faltering vision.

When vision works, it seems so simple: the world is just there for us to see. But when it fails, vision’s complexity becomes acutely apparent. While a general practitioner or optometrist can check many potential explanations for vision problems by simply examining the eye, if the cause isn’t visible, a deeper level of inquiry may be necessary. So Gorski, an assistant clinical professor of optometry, deploys electrophysiology to track down evasive diagnoses at Berkeley’s Vision Functions Clinic. Most of her patients have been referred by primary eye care providers unable to identify the nature of their patients’ blurred vision, night vision problems, or excessive light sensitivity.

Formed nearly three decades ago, the VFC is specially equipped to interrogate the functioning of the retina and the optic nerve, and hence to identify various retinal and visual pathway disorders. The clinic’s two gravitational centers are, first, an electroretinogram (ERG), a machine used to measure the electrical activity of the retina in response to light stimulation, and second, Gorski herself, who took over as clinic chief in 2019. She is trained specifically to use the ERG and the clinic’s other electro-sensitive testing devices, and to interpret their results.

By locating and reading electrical signals emitted from groups of cells firing in the retina, the ERG enables clinicians to evaluate patients for retina-related conditions and to reliably monitor retinal function over time, helping to evaluate the efficacy of—and to fine tune—retinal treatments. “The ERG shows objectively how the retina is functioning so we can figure out what’s really going on at the cellular level in the most puzzling cases,” Gorski says.

Administering the test
First, Gorski uses eye drops to dilate the patient’s pupils and to anesthetize their eyes. She then puts the patient in a dark room so their retina can dark-adapt, before painlessly placing an electrode (embedded in a contact lens) on each of the patient’s corneas.

“The electrodes record the electrical activity generated by the retina in response to various flashes of light,” says Gorski. “We then record responses in a similar manner under light-adapted conditions. From the recordings, we can determine the health of the cones, rods, and other retinal cells.”

The retina’s responses, as measured by the ERG, are expressed as waveforms corresponding to different stages of retinal processing, including the a-waves (primarily generated by photoreceptors), b-waves (largely generated by bipolar cells), and other components that reflect the complex interplay of different retinal cell types.

A roadmap for patients and their doctors
The test results help Gorski zero-in on retinal and visual pathway disorders that would otherwise be invisible. Her clinic patients divide into two main groups: The first is children or teens whose eyes appear to be fine, but who are suffering from reduced central vision, bad night vision, or some other symptom that is affecting their quality of life. Typically, the referring doctor suspects an inherited retinal dystrophy, evidence of which just may not be yet visible.

“The most common inherited retinal dystrophy we see is retinitis pigmentosa,” says Gorski. “And that can affect people at any age, but we see it most commonly in our young patients—a parent brings their child into the clinic after noticing that they don’t see well and are bumping into things at night, for example, even though a visual inspection of their eye looks okay,” she says. “If the ERG reveals dysfunction of the night-vision-sensing rod photoreceptors, then we’d send the patient for genetic testing to zero-in on an etiology.” In other words, and to paraphrase detective fiction writer Raymond Chandler, this helps determine if the streets really are dark with something more than night.

The second type of patient is older but also has visual symptoms with unexplained cause. “A patient may experience a significant decline in their night vision, difficulty with light-dark adaptation, or perhaps central vision loss without any visible cause. Or they may experience other disturbances in their vision, like visual snow” (static-like white dots in the vision), says Gorski.

“Electrodiagnostic testing can help localize the problem and give us a sense of the level of dysfunction occurring in that area. This helps direct what additional tests are needed to reveal the diagnosis, which might include additional labs for systemic diseases, MRIs of the brain, or genetic testing. For example, if an inherited retinal dystrophy is suspected, we will recommend genetic testing, and the ERG will provide context for interpreting the results and giving us a better idea of prognosis.”

Visually Evoked Potential (VEP)
Null results from retinal tests suggests the problem may lie further downstream in the visual system, and Gorski can follow such leads with a Visually Evoked Potential (VEP) test, which assesses the conduction of visual signals from the retina through the optic nerve and to the various visual processing areas of the brain.

The patient taking the VEP has their scalp fitted with electrodes and is presented with visual stimuli, such as patterns or flashing lights, while the electrodes pick up the electrical signals traveling through the optic nerve to the visual cortex in the back of the brain. Gorski analyzes the speed and strength of the signal conduction to glean more valuable clues about the functioning of the optic nerve. If she identifies a problem there, she is likely to refer her patient to a neuro-optometrist or a neuro-ophthalmologist.

Helping patients navigate the best way forward
More often than not, Gorski is delivering tough news to her patients and their doctors. If they have made their way to her clinic without a diagnosis, their conditions are likely to be systemic and degenerative. Retinal dystrophies are the most common conditions her detective work reveals. Cone dystrophies are not uncommon. Stargardt disease is another condition that she too often sees. These diseases may not be curable, but accurate diagnosis is key to ensuring patients can undergo the best available treatments or adopt the best mitigations to maintain their quality of life. What’s more, when a patient experiences a symptom, say very poor night vision, but can’t find an explanation, that can be very demoralizing. “Locating the nature of the problem can validate the patient’s experience,” says Gorski, “even if the condition cannot be fixed.”

“Although many of these retinal issues don’t have treatments or cures, often, we can still help by getting the patients the rehabilitation or just the prognosis that they need,” says Gorski.

Sometimes a clinic visit does reveal information that helps a patient recover lost vision or avoid further harm. For example, Gorski sees cases of retinal inflammation, where early diagnosis helps avoid permanent damage, and treatments such as intravitreal injections or systemic medications may help improve the problem. She also tests patients taking medications for unrelated conditions that may cause retinal damage. “We’re able to monitor these patients closely so that if they develop a toxicity, we can end the medication course before they even have visual symptoms of it. We’re able to save them from a sight-threatening condition. That’s very gratifying!”

In some cases, Dr. Gorski refers patients with intractable retinal or optic nerve conditions to clinical trials, which may help those patients as well as advancing knowledge in the field. She has high hopes that, for example, as emerging gene therapies mature and become available to her patients, many of the inherited retinal dystrophies she now diagnoses will become treatable. “With treatment options for these conditions, early diagnosis with ERG testing will be all the more critical,” she says. And more of the tough and hard-to-crack cases she investigates will have a clearer resolution.

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