RETINA Throwback + Interview: Harry Flynn’s Cannulated Extrusion Needle

Eric Nudleman, UCSD
Yoshihiro Yonekawa, MEEI/Boston Children’s
Harry Flynn, Bascom Palmer

30 years ago in 1988, some things about the journal RETINA were the same, and some things were different. Differences with 2018: The journal was in its 8th year, and producing 4 issues a year. Fewer P values in papers also. Now after more than 7,000 publications that have moved the field forward in so many ways, RETINA is a monthly journal with 12 issues a year with frequent supplemental issues. Similarities with 2018: RETINA was the dominant subspecialty journal in ophthalmology, and Dr. Harry Flynn was in every issue.

Dr. Flynn is the Donald M. Gass Professor of Ophthalmology at Bascom Palmer Eye Institute of the University of Miami, and has taught us so much about vitreoretinal surgery. Discussing all of his accomplishments would take about 100+ blog entries, but today, we wanted to focus on one of his (many) papers in RETINA from exactly 30 years ago.


In 1988, Volume 8, Issue 1, Harry Flynn, Janet Davis, Jean Parel and William Lee published a paper where they describe the clinical applications of a new instrument that they had developed to improve vitreoretinal surgery. At the time, there were no soft tip cannulas, no small gauge platforms, and no wideangle viewing systems. Avoiding retinal incarceration of the drainage site was more challenging to avoid, and complete flattening of the retina was more difficult. Dr. Flynn and his co-investigators first described the cannulated subretinal fluid aspirator in 1987 (Am J Ophthalmol 1987;103:106-107), and in 1988 described a series of patient surgeries in RETINA (Retina 1987;8:42-49).


We had the opportunity to speak with Dr. Flynn about his clever device. Please enjoy our transcribed conversation:

Where did the idea for this instrument begin?

Flynn: In the mid 1980s, vitreoretinal surgeons recognized that we can drain through an existing break, but we had trouble removing all of the subretinal fluid. At the time, some surgeons were starting to make posterior draining retinotomies, but not many. There was wide concern about making another hole in the retina. Early on, following drainage through retinotomy, secondary choroidal neovascular membrane was an issue. In addition, PVR extending from the posterior draining retinotomy was a concern.

Nowadays, we know how to do it with a soft tip cannula. But at the time the complications were high. So the idea for this instrument was to remove all the subretinal fluid by getting into the subretinal space with an elongated soft tubing. With a concurrent air-fluid exchange, I could tamponade the break and simply take my finger off the flute and allow the pressure of air to push the fluid out.

Flynn Cannula

How did you go about making a prototype and testing it?

Mark Blumenkranz and I started working together on this in 1986. We worked in the biophysics lab at Bascom Palmer with Jean-Marie Parel (who was the original designer and builder of the VISC [vitreous infusion suction cutter] with Robert Machemer). There were already fluted needles – Steve Charles had designed and used them since 1980). We wanted to go one step further by being able to cannulate the break in order to get posterior subretinal fluid.

The criteria for a soft tip tube were: it had to be flexible, soft, yet rigid enough to maintain its direction. We looked at many tubes for their stiffness in the biophysics lab. Small silicone tubes were commercially available in many sizes, bores, and calibers. We used them until we found one that met our needs.

Was the handpiece also manufactured in the biophysics lab?

Yes. I told them that I liked to use it like a pencil, and I wanted it to rest in my hand so that my index finger was used to engage the flute and to extend the tubing. That was different from the VISC handpiece. We made about ten of them, and I gave them to some friends. Nowadays, it is difficult to go through the regulatory requirements to make an instrument. At that time, there was no such thing as IRBs.

Were there any early problems?

The original instrument was like a fishing reel. The assistant would reel it into the subretinal space. The problem was, we didn’t know how far it was extended. We did not have widefield viewing, so we were looking at the anterior break. Meanwhile, the tube was being thread into the subretinal space and it could go way too far without us realizing it.

I said, “I don’t need a mile, I need an inch!” So we changed the design to put the tubing on a slide apparatus for 1 inch, so that was the maximum amount it could be extended. That was about the right length so that it would not go further than the posterior pole.

We also noticed that following the procedure all patients had a pigment trail in the area where the tubing was. There was some concern that this would result in a functional problem. Then we had a case where the trail went right through the fovea, but the vision returned to 20/20! That helped to alleviate any concern.

Retina Reattached

How was your experience like with the first patient?

Well, first we played with it in the lab on animal eyes. Then, around 1986-87, we used it on the first human patient. She had a total retinal detachment with a large inferior break. We did the surgery by placing the tube into the break, turned on the air pump, and the retina completely flattened.

I said, “YAHOO!” Everyone was extremely happy. Janet Davis was my fellow and was with me in the OR, and was there for all the hooting and hollering. The first patient is still alive and is about 90 years old. Her vision in that eye is about 20/60. Her fellow eye developed wet AMD and has poor vision. Interestingly, the total retinal detachment eye never developed AMD. She knows that she was the first patient, and it is great to have 30 years of followup.

After that patient, we used it more and more. But this time also coincided with the start of perfluorocarbon liquids in retinal surgery, in the late 1980s. Therefore, the same goals could be accomplished with heavy liquids. There was a lot of discussion at the time of which was better? Certainly for giant retinal tears, PFO was better. But the issues of retained PFO, or subretinal PFO, were avoided with the cannulated extrusion needle.

Is it still being manufactured?

Before I joined Bascom Palmer, I spent 2 years at Brooke Army Medical Center in San Antonio. While I was there, we did lensectomies using the Shock Phacofragmentor. It was a 20-gauge instrument, and had a 45-degree angle to it. It allowed you to frag and aspirate the lens pieces. It was designed by John Shock, who was at Letterman hospital in San Francisco. I met John when I was a fellow in San Francisco, and he introduced me to the instrument. Then, he was transferred to Brooke Army Medical Center, so when I was there, he was my chief.

We had a shared interest in vitreoretinal surgery. John tried to patent the Shock Phacofragmentor. He spent years trying to get this done, and when it was finally accomplished, other instruments were also available. It was a total headache, so John said,

“Never again try to patent an instrument”.

So when this extrusion needle came out, I gave it to Alcon to avoid having to patent it. Alcon took it over, and manufactured and distributed the instrument. Alcon doesn’t currently make it, but Vitreq does and DORC does. It is available in 23 and 25-gauge, and extends up to 8 mm.

Thank you Dr. Flynn for always being a trailblazer in our field, and for the very educational behind-the-scenes stories for the Flynn cannulated extrusion needle.