February 2019

NEWS & OPINION

Performing single-pass four-throw pinhole pupilloplasty


by Maxine Lipner EyeWorld Senior Contributing Writer


Preop vision 6/60 after penetrating keratoplasty with more than
20 D of astigmatism

Postop day 1 after pinhole pupilloplasty; vision improved to 6/12



Pinhole pupilloplasty preop and postop; preop vision 6/60, postop 6/12; patient with 8 D of astigmatism
Source: Amar Agarwal, MD

 

New technique for improving acuity in high astigmatism

Imagine being able to treat patients with high irregular astigmatism using a simple, low-cost procedure and offer them excellent vision in turn. This is the promise of pinhole pupilloplasty, according to Amar Agarwal, MD, chairman and medical director, Dr. Agarwal’s Group of Eye Hospitals, Chennai, India, who pioneered the unique procedure.
Dr. Agarwal drew inspiration from a sea creature known as a nautilus, a mollusk with no lens in its eye. “What makes the mollusk see is that nature has given it a pinhole eye,” he said. Dr. Agarwal started thinking about whether it might be possible to use the same phenomenon to improve vision in humans with vexing issues such as high astigmatism.
The theory behind how this pinhole effect could improve vision is a byproduct of what’s known as the Stiles-Crawford effect. The idea is that a ray of light coming straight into the eye offers maximum stimulation of cones, Dr. Agarwal explained, adding that there actually are no rods in the center of the fovea. Meanwhile, if light was coming in from the side, the response of the cones would be less. Dr. Claudio Trindade had initially developed a piggyback pinhole IOL that was a dark lens with a 1.5 mm opening in the center, creating a pinhole effect in an eye that usually had a 5 mm opening. “Those lenses are very good, but the problem is they do not have FDA approval,” Dr. Agarwal said. The problems with the pinhole IOLs are the cost, availability, and FDA approval.

Unique four-throw technique

Dr. Agarwal decided to create the effect in the eye using a technique called single-pass pinhole pupilloplasty, relying on the iris to keep a portion of the light out. “We tried making the pupil small by making it fixed at 1.5 mm,” he said, adding that any light beyond this range will hit the sides of the iris instead of entering the eye.
While any pupilloplasty technique will work, Dr. Agarwal uses what he terms a single-pass four-throw pupilloplasty. With the technique, the practitioner first catches the iris with forceps before passing a straight needle with 10-0 or 9-0 Prolene through it. Then, from the other end, the physician enters the iris through a clear corneal incision and passes a 26-gauge or 30-gauge needle. Using a railroad technique, the suture is passed out and a loop created. Through this loop the surgeon passes four throws, which results in one thread on one end and the other piece on the side of the clear corneal incision. These can be pulled simultaneously as if tightening a shoelace, cinching this part of the iris so that it covers more of the pupil. Then the practitioner can do the same on the other side, resulting in a small pupil, Dr. Agarwal said. The procedure can be repeated until one gets a 1.5 mm pupil. A vitrector can also be used to help achieve this.
Dr. Agarwal has created a 1.5 mm pinhole marker to ensure that the pupil is the correct size. This is placed on the cornea around the pinhole to see that the pupil is exactly 1.5 mm. To make sure the pupil is centered, the practitioner can look for the reflection of the light of the Lumera microscope (Carl Zeiss Meditec, Jena, Germany) to show exactly where the pupil is, Dr. Agarwal explained. This is the Purkinje image. One can make the pupil surrounding the Purkinje images and that would give a 1.5 mm pupil. “Alternately, with the pinhole marker, you can mark on the cornea the center, so you can have a centered pupil,” he said.
“The whole pinhole pupilloplasty procedure doesn’t take more than 10 minutes. The cost is only the amount of one suture,” Dr. Agarwal said. This is something that can be done by any practitioner, he stressed.

Visual boon

With this technique, he reported, patients start instantly seeing better. Those who are well-suited to this tend to have high irregular astigmatism, for instance someone who may have a scar on the cornea, underwent corneal transplantation, or has keratoconus. “In all such cases, you can do a pinhole pupilloplasty,” Dr. Agarwal said.
The results with the technique have gone beyond Dr. Agarwal’s expectations. He recalled one of his patients who received a corneal patch graft resulting in 20 D of astigmatism. Instead of doing a complex keratoplasty on the patient, Dr. Agarwal decided to perform pinhole pupilloplasty. “I said, ‘Let me make this pupil small and see what happens,’ and after that, the man was reading five lines on the board,” he said. “With 20 D of astigmatism, I was in total shock.”
What’s more, he has found that the pinhole could give patients an extended depth of focus, enabling them to see well simultaneously at distance and near. For example, Dr. Agarwal had a patient with a corneal injury because of a glass foreign body, which left him with high astigmatism. “When I did a pinhole pupilloplasty for him, he was so happy because he could see both distance and near,” Dr. Agarwal said.
With the four-throw procedure, it is also still possible to get some limited dilation, he noted. “So fundus examination is possible,” Dr. Agarwal said, adding that if something more extensive is needed, such as for a case of retinal detachment, it is possible to YAG the iris and undo the procedure.
One caveat with the pupilloplasty is that if a patient has a normal crystalline lens, he or she needs to be made pseudophakic before performing the procedure, Dr. Agarwal cautioned. “When you do a pupilloplasty, it may touch the crystalline lens and create a cataract,” he said.
It’s also not possible to do the procedure if the patient doesn’t have any iris present. “But these are very small disadvantages from what I’m seeing because the advantages are huge,” he said.
Determining if someone may be a good candidate for the procedure can be as simple as holding a pinhole in front of their eye. “If the patient improves with a pinhole, they will improve with a pinhole pupilloplasty,” Dr. Agarwal said. “You can tell the patient, ‘You are improving with the pinhole. I will make your pupil smaller to about 1.5 mm and your astigmatism will be neutralized.’” The result will be a patient who only needs to undergo a quick procedure and who will likely be extremely happy, he said.

Editors’ note: Dr. Agarwal has no financial interests related to his comments.

Contact information

Agarwal
: aehl19c@gmail.com

Performing single-pass four-throw pinhole pupilloplasty Performing single-pass four-throw pinhole pupilloplasty
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