Single-pass four-throw pupilloplasty has advantages in various clinical settings

Cases involving Urrets-Zavalia syndrome and pinhole pupilloplasty may benefit from this technique.

Issue: December 10, 2020

ByPriya Narang, MS

ByAmar Agarwal, MS, FRCS, FRCOphth

Pupil size usually plays a significant role in the quality of vision.

When the pupil is dilated and fixed, it can compromise the quality of vision. Such an altered pupil can add unwanted symptoms including glare, photophobia and visual distortions, especially when combined with an irregular cornea, and these symptoms may interfere with the patient’s daily activities, including driving a car, reading and more.

Additionally, if the pupillary and iris defect is more extensive, this causes the iris diaphragm to be floppy and less rigid and can lead to anterior and/or posterior synechiae, which can cause additional issues including secondary rise in IOP, especially when the aqueous outflow path at the anterior chamber angle is compromised. In these situations in which the iris may be damaged and the patient is symptomatic, surgical correction may be required. A simplified, reproducible surgical technique with sutures that the surgeon is familiar with makes such surgical correction easier to perform.

In this column, Drs. Narang and Agarwal describe their current method of single-pass four-throw pupilloplasty.

Thomas “TJ” John, MD
OSN Surgical Maneuvers Editor

Single-pass four-throw pupilloplasty (SFT) is a technique for performing pupil reconstruction that we described in 2018 (Figures 1 and 2). The surgical procedure of SFT has been documented to have various advantages in the clinical setting. The main advantage with performing SFT is that it is easy to perform, and the surgeon can easily duplicate it in the OR. This technique has a self-locking mechanism wherein only the approximation loop is taken and the second pass of positioning a securing loop is absent.

Figure 1. Figure showing SFT pupilloplasty (part 1). Pupil dilated in a pseudophakic eye (a). SFT pupilloplasty being performed. The long arm of the needle attached to a 10-0 polypropylene suture is threaded into the barrel of a 30-gauge needle (b). The loop is withdrawn from the anterior chamber (c). The suture end is passed through the loop four times (d).

*Source: Priya Narang, MS, and Amar Agarwal, MS, FRCS, FRCOphth*

Figure 2. Animation showing SFT pupilloplasty (part 2). A helical knot is formed (a). Suture ends being cut with microscissors (b).

This technique derives its name as only a single pass is involved in the surgical procedure followed by four throws that are taken in the same direction through the loop (Figures 3 to 5). Experimental analysis was done wherein additional throws were taken to analyze the amount of throws essential to create a self-locking knot. Four throws were found to have optimal locking mechanism; more than four throws also secured the loop, but they were not essential and just added to the burden of the loop inside the anterior chamber.

Figure 5. Surgical steps showing SFT pupilloplasty (part 3). Microscissors are used to cut the ends of the knot (a). Pupilloplasty complete (b).

Surgical technique

A 10-0 polypropylene suture attached to the long arm of the needle is passed from the limbal cornea engaging the proximal iris tissue that needs to be approximated. A paracentesis incision is made, and a 30-gauge needle is passed through the paracentesis incision. The 10-0 suture needle now engages the distal part of the iris tissue and is then threaded into the barrel of the 30-gauge needle, which is then withdrawn from the paracentesis incision. This pulls the suture along with the needle outside the anterior chamber. A loop is withdrawn with the help of a Sinskey hook, and the suture end is passed through the loop four times, taking care to pass it in the same direction. Both the suture ends are then pulled, and this leads to sliding of the loop inside the anterior chamber, creating a self-locking loop that engages the iris defect. The suture is then cut with microscissors. The procedure can be repeated until all of the iris defects are closed.

Precautions

The surgeon should be careful not to engage the corneal tissue while passing the 10-0 suture needle. Failure to address this aspect can lead to non-sliding of the loop inside the anterior chamber, which leads to failure of the surgical procedure. The suture then needs to be cut, and the procedure needs to be redone.

Clinical application

Urrets-Zavalia syndrome (UZS): UZS syndrome is often associated with persistent pupillary dilation along with raised IOP. The persistently dilated pupil falls back of the iris tissue on the anterior chamber angle structures, which leads to formation of peripheral anterior synechiae (PAS) and raised IOP (Figure 6). Performing SFT in these cases leads to narrowing down of the pupil and prevents creeping of the anterior chamber angle structures. SFT has also been documented to break the PAS, thereby controlling the rise in IOP.

Figure 6. SFT pupilloplasty for treating closed-angle glaucoma. Pseudophakic eye with high IOP (a). Anterior segment OCT denoting narrow angle structures (b). Postoperative image after SFT pupilloplasty (c). Anterior segment OCT denoting open angles in the postoperative period (d).

Pinhole pupilloplasty (PPP): SFT has been successfully applied to perform PPP in cases with higher-order corneal aberrations. The pinhole pupil achieved with PPP bars the distorted peripheral rays arising from the irregular corneal structure, and it also channelizes the ray of light through the center of the pupil. This imparts pinhole optics and provides the patient with enhanced depth of focus for distance, intermediate and near vision. The defocus curve after PPP has been shown to impart extended depth from a range of –2.5 D to +1.5 D. The patient experiences dramatic improvement in visual quality due to pinhole optics. A detailed analysis of cases that underwent PPP has demonstrated statistically significant improvement in vision under photopic and mesopic light conditions. A dramatic improvement in low contrast visual acuity was also documented. The advantage of using SFT for PPP is that due to the minimal pass involved, PPP can be easily performed to achieve a pinhole pupil with three to four attempts with SFT (Figures 7 and 8).

Figure 7. Pinhole pupilloplasty in a post-RK eye (part 1). Patient has high astigmatism in a post-RK eye. SFT pupilloplasty performed to make the pupil 1.5 mm (a to f).

Figure 8. Pinhole pupilloplasty in a post-RK eye (part 2). Pinhole pupil created with the SFT pupilloplasty technique and a vitrector to achieve a 1.5 mm pupil. Intraoperative image depicting a well-centered PPP with the P1 reflex engulfed by the pupillary margin should be the target (a to f).

Advantages

As a single pass is involved in SFT, iris repair can be done with minimal intervention in the anterior chamber. This automatically translates into less intraoperative manipulation and thereby leads to less inflammation in the postoperative period.

It is easier to perform PPP with SFT due to minimal interventions involved in the surgical procedure.

SFT has also been documented to be effective in cases with silicone oil-induced secondary glaucoma. Intraoperative gonioscopy has demonstrated breakage of PAS after SFT.

Posterior segment evaluation after PPP can be performed, and significant dilation of the pupil can be achieved after the instillation of mydriatic drops. Nevertheless, for any posterior segment intervention in the future, the suture loops can be ablated with YAG laser. Additionally, if a surgical intervention is essential, the loop can be easily opened up intraoperatively.

References:
Kumar DA, et al. J Cataract Refract Surg. 2017;doi:10.1016/j.jcrs.2017.07.027.
Narang P, et al. Eur J Ophthalmol. 2017;doi:10.5301/ejo.5000922.
Narang P, et al. Eur J Ophthalmol. 2018;doi:10.1177/1120672117747038.
Narang P, et al. J Cataract Refract Surg. 2019;doi:10.1016/j.jcrs.2018.12.007.
Narang P, et al. J Cataract Refract Surg. 2019;doi:10.1016/j.jcrs.2019.02.037.
Narang P, et al. J Cataract Refract Surg. 2020;doi:10.1097/j.jcrs.0000000000000421.

For more information:
Amar Agarwal, MS, FRCS, FRCOphth, can be reached at Dr. Agarwal’s Eye Hospital and Eye Research Centre, 19 Cathedral Road, Chennai 600 086, India; email: aehl19c@gmail.com.
Priya Narang, MS, can be reached at Narang Eye Care & Laser Centre, Ahmedabad, India; email: narangpriya19@gmail.com.
Edited by Thomas “TJ” John, MD, a clinical associate professor at Loyola University at Chicago, and in private practice in Oak Brook, Tinley Park and Oak Lawn, Illinois. He can be reached at email: tjconference@gmail.com.

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Sources/Disclosures

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Disclosures: Agarwal, Narang and John report no relevant financial disclosures.

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