John P. Berdahl, MD


Dr. Berdahl is a clinician and researcher at Vance Thompson Vision in Sioux Falls, South Dakota, where he specializes in advanced cataract, cornea, and glaucoma surgery. In this interview, he shares how a thought-provoking idea was conceived 30 feet underwater, what he considers intellectual candy, and what he enjoys the most in his career.

Interviewed by Callan Navitsky, MillennialEYE and Glaucoma Today Editor-in-Chief

Nominated by the Chief Medical Editors of MillenialEYE

BMC: Who or what drew you to ophthalmology?

John P. Berdahl, MD: I won a science scholarship for college, so I was required to have a science major. Initially, I planned on becoming an engineer, but then I realized I wanted to work more closely with people and started to consider optometry. Upon hearing this, my family optometrist said, “I think you would be happier as an ophthalmologist because of your curiosity. You wouldn’t want artificial legal limits imposed on your practice.” I told him I wasn’t sure I had what it takes to be an ophthalmologist, and, in response, he gave me the single best piece of advice I have ever received. He said, “A few years on the front end of your life to do what you’re meant to do for the rest of your life is always time well spent.”

Ultimately, I applied to medical school with the hopes of going into ophthalmology, and I caught a couple of breaks with some important mentors along the way. Since then, it’s been like a hand in a glove, and I love what I do every day. I think the reason why I am so passionate about ophthalmology is because we have fixable problems. There is a lot of physics-related and mathematical problem-solving in our specialty compared with others, and that allows us to go all the way to basic physics principles to think through how we can solve a patient’s problems. That is intellectual candy to me.

BMC: What was it specifically about cataract surgery and glaucoma that appealed to you?

Berdahl: What appealed to me about cataract surgery is that there is a defined point when the procedure is complete. I remember running a bowel as a medical student and looking for a perforation. We did this for 25 minutes and then said, “Let’s do it one more time.” We were never sure when we were done. With cataract surgery, the surgical steps are clear. Further, this procedure can make such a remarkable difference. We get hugs from patients every day because they value their vision so much. These are the same qualities I found attractive in corneal surgery as well.

Glaucoma, on the other hand, is more of an intellectual and philosophical endeavor. I love thinking about the disease itself and whether it is a balance between intraocular pressure (IOP) and cerebrospinal fluid (CSF) pressure. I often find myself asking, “What are we missing in the big picture of this disease?” and “How can we think through the disease to fundamentally understand it better and develop better treatments?”

BMC: Can you tell us about your idea that glaucoma may be a two-pressure disease? How was this concept conceived?

Berdahl: When I was a first-year resident at Duke, I was scuba diving with my wife in the Caribbean on the one vacation we get during residency. I was down 30 feet, and I thought, wait a second, there is all this weight of the water pushing on my eye—760 mm Hg of pressure from the water—and I drill a hole in a patient’s eye for 50 mm Hg … why doesn’t this add up? Instead of enjoying my vacation and a Corona, I couldn’t get this idea out of my head. I came to believe that it is not the absolute pressure inside the eye but a balance between eye pressure and brain pressure. Those pressures move together in lockstep while you are diving or when you go to a higher elevation. That is why scuba divers aren’t at higher risk for glaucoma.

I came back from vacation excited to tell R. Rand Allingham, MD, about my idea. He said, “That’s interesting. I’m not sure you’re right, but go study it.” So, we studied it at the Mayo Clinic. We looked at more than 55,000 electronic records to find patients who had glaucoma and who had undergone spinal taps. We identified the patients who had both and compared them. We found that, indeed, CSF pressure was lower in patients with glaucoma and even lower in patients with normal-tension glaucoma, explaining why so many people who have normal eye pressures still develop glaucoma. CSF pressure was higher in patients who had ocular hypertension, high eye pressure but no glaucoma, which explains that, too. This concept fills an enormous gap in our understanding of glaucoma. Since then, we have published a number of papers, one of which showed that CSF pressure begins to decrease with age, starting around 55 years.1 Other investigators have looked at this, and nearly every study has confirmed there is a balance between IOP and CSF pressure that is part of the pathogenesis of glaucoma.

BMC: Are there any other challenges in ophthalmology making you lose sleep?

Berdahl: There is an incredible distance between an idea and a product, and there is an incredible distance between a product and a business. Coming up with the idea is the most fun, and it is just 1% of the process. The rest is real work. If people invest in your idea and you employ people based on that, it becomes a huge responsibility to deliver on the trust that investors, employees, and ultimately patients put in you to try to develop something that can improve patient care and advance our profession. The idea phase is the most fun. Boy, if we could just sit around and spit out ideas all day, it’d be great.

BMC: So far, in your career, what would you say is your greatest accomplishment?

Berdahl: My greatest accomplish-ment is being a trustworthy partner, employer, and doctor. The most enjoyable thing that I do is train our fellows—that’s my favorite part.

BMC: If you had to nominate one creative mind in ophthalmology, whom would it be and why?

Berdahl: It would be my partner, Vance Thompson, MD, FACS. He is far more creative than I, and I have learned so much from him. When everybody is looking at a slide with one thing on it and they’re focused on that one thing, Vance is looking at something completely different. He sees the world through a different lens, and he identifies opportunities that other people can’t see. If you gave me two more votes, I’d pick Richard L. Lindstrom, MD, and Malik Y. Kahook, MD. (Editor’s Note: The Chief Medical Editors of CollaborativeEYE have selected Dr. Thompson as a creative mind and the Chief Medical Editors of MillennialEYE have selected Dr. Kahook.)

1. Fleischmann D, Berdahl JP, Zaydlarova J, Stinnett S, Fautsch MP, Allingham RR. Cerebrospinal fluid pressure decreases with older age. PLoS One. 2012:e0052664.

John P. BerdaHl, MD
• Clinician and Researcher, Vance Thompson Vision, Sioux Falls, South Dakota
• Member, CRST Editorial Advisory Board
• Financial disclosure: Consultant (Alcon, Allergan, Aurea Medical, Avedro, Bausch + Lomb, Clarvista, Dakota Lions Eye Bank, DigiSight, Envisia, Equinox, Glaukos, Imprimis, Iantech, Johnson & Johnson Vision, New World Medical, Ocular Therapeutix, Omega Ophthalmics, Ocular Surgical Data, Sightlife Surgical, RxSight, Vitamed, Veracity); Equity owner (DigiSight, Equinox, Omega Ophthalmics, Ocular Surgical Data, Sightlife Surgical, Veracity); Lecture fees (Alcon, Allergan, Glaukos, Iantech); Patent/Royalty (Imprimis)


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About Retina Today

Retina Today is a publication that delivers the latest research and clinical developments from areas such as medical retina, retinal surgery, vitreous, diabetes, retinal imaging, posterior segment oncology and ocular trauma. Each issue provides insight from well-respected specialists on cutting-edge therapies and surgical techniques that are currently in use and on the horizon.