John P. Berdahl, MD

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

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’d 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; in response, he gave me the best advice I’ve ever received: “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.”

I think I am so passionate about ophthalmology 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 about cataract and glaucoma that appealed to you?

Berdahl: What appeals 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, surgical steps are clear. 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 IOP and cerebrospinal fluid (CSF) pressure.

BMC: What was ophthalmology training like for you?

Berdahl: Medical school was hard work, and I wouldn’t say I was that great at it. Ophthalmology training was challenging, but it felt like what I was meant to be doing. I loved residency. I had fantastic teachers and mentors, and Duke University was a place where they combined scientific rigor with intellectual curiosity and pragmatism.

BMC: Who were some of those mentors you worked with in training?

Berdahl: I had many influential mentors in training. The three who stand out from residency are the late David L. Epstein, MD; R. Rand Allingham, MD; and Terry Kim, MD. In fellowship, Richard L. Lindstrom, MD; David Hardten, MD, FACS; Thomas W. Samuelson, MD; and Sherman W. Reeves, MD, MPH.

BMC: When finishing up fellowship, did you know what type of practice setting you wanted to enter, or did you take time to explore?

Berdahl: During fellowship, I didn’t know for sure what would come next. I have academic intellectual curiosities, but I knew I didn’t want a purely academic appointment. The reason why is because the first paper we submitted on CSF pressure was rejected, and it was devastating to me. I believed we were right, that we did the necessary work, and that our findings were important. The idea that anonymous reviewers could reject it was hard on me and showed me that I didn’t have the fortitude and intellectual stamina possessed by many academics. I knew I couldn’t base that much of my self-worth on the opinions of paper or grant reviewers. I also knew, however, that I wanted to continue to pursue my ideas and didn’t want to simply punch in and punch out. I wanted to help set the standard of care, not just follow it.

At Vance Thompson Vision, I found a place where the patient experience and the employee experience come first. There is a heavy emphasis on research, so I knew I could participate not only in clinical trials but also in my own internally generated organic research. Plus, I could take care of a lot of patients. If I was given a blank piece of paper and told to write my story, I wouldn’t have had the courage to write it as good as it has turned out.

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

Berdahl: When I was a first-year resident, 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 Dr. Allingham 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’ve published a number of papers, one of which showed that CSF pressure begins to decrease with age, starting around 55 years.1

BMC: With any idea, there will be skeptics and naysayers. Have you come up against that?

Berdahl: Yeah! I’ve kept a list of great quotes from some of the rejections I’ve received. A couple of my favorites are:

  • “This is not science but simple armchair philosophy”;
  • “Rabbits won’t wear goggles”;
  • “It would be unethical to proceed with this study due to the complete lack of valid scientific data it’d produce”;
  • “The innovation would be great if not based on a flawed concept”; and
  • “How did this applicant not realize IOP is the result of an equilibrium?”

It’s hard when people whom you admire and respect think your ideas are crazy or wrong. I’m not putting ours there yet, but the history of ideas is littered with challenges. That’s not to say that we shouldn’t be challenged—we should be, but it should be authentic.

BMC: What other challenges in ophthalmology make you lose sleep?

Berdahl: There is incredible distance between an idea and a product and 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. So, 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: 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 Dr. Lindstrom and Malik Y. Kahook, MD. (Editor’s Note: The Chief Medical Editors of CollaborativeEYE have selected Dr. Thompson as one of its creative minds and the Chief Medical Editors of MillennialEYE have selected Dr. Kahook. For those interviews, see pgs 41 and 29, respectively.) n

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, Glaucoma Today Editorial Board
Financial disclosure: Consultant (Alcon, Allergan, Aurea Medical, Avedro, Bausch + Lomb, Clarvista, CorneaGen, Dakota Lions Eye Bank, DigiSight, Envisia, Equinox, Glaukos, Imprimis, Iantech, Johnson & Johnson Vision, New World Medical, Ocular Therapeutix, Omega Ophthalmics, Ocular Surgical Data, RxSight, Vitamed, Veracity); Equity owner (CorneaGen, DigiSight, Equinox, Omega Ophthalmics, Ocular Surgical Data, Veracity); Lecture fees (Alcon, Allergan, Glaukos, Iantech); Patent/Royalty (Imprimis)


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