Pinhole Pupilloplasty

Principle

A pinhole or a small aperture is created, thereby allowing passage of rays of light from the central aperture and blocking the rays emanating from the peripheral irregular cornea, so that the impact of higher order aberrations caused by irregular corneal astigmatism can be minimized. Another mechanism is the Stiles-Crawford effect of the first kind, according to which, an equal intensity of light entering near the centre of the pupil produces a
greater photoreceptor response compared with the light entering the eye near the edge of the pupil. Therefore, when the pupil narrows, more focused light enters the eye through the narrow aperture, producing a greater photoreceptor response.

Procedure

• Under peribulbar anaesthesia ,4 mL lidocaine hydrochloride (Xylocaine 2.0%) and 2 mL bupivacaine hydrochloride 0.5% (Sensorcaine)
• 2 paracenteses are created and a 10-0 polypropylene suture attached to the long arm of the needle is introduced into the anterior chamber.
• The anterior chamber can be maintained with an ophthalmic viscosurgical device or with fluid infusion with the help of an anterior chamber
  maintainer or a trocar anterior chamber maintainer.
• An end-opening forceps is introduced through the paracentesis, and the proximal iris leaflet is held. The suture needle is passed through the
  proximal iris tissue.
• A 26-gauge needle is introduced from the paracentesis from the opposite quadrant and passed through the distal iris leaflet after being held with end-opening forceps. Next, the tip of the 10-0 needle is then passed through the barrel of the 26-gauge needle, which is then pulled out of the paracentesis. The 10-0 needle exits the anterior chamber along with the 26-gauge needle.
• A Sinskey hook is passed through the paracentesis, and a loop of suture is withdrawn from the eye. The suture end is passed through the loop 4 times. Both the suture ends are pulled and the loop slides inside the eye, approximating the iris tissue edges. The suture ends are then cut with micro scissors and the procedure is repeated in the other quadrant to achieve a pupil of desired configuration and to decrease the pupil to pinhole size.

Indications

• Functional or Optical:

  Symptomatic iris defects (Congenital, Acquired, Iatrogenic, Traumatic)

• Oppositional angle closure or PAS:

  To break PAS and angle apposition angle closure glaucoma whether primary, post trauma, plateau iris
  syndrome, Urrets-Zavalia syndrome or long-standing silicone oil in the anterior chamber.

• Cosmesis:

  PPP can be done for cosmetic indication, especially in large colobomas.

• Penetrating Keratoplasty:

  In cases of floppy iris that is expected to adhere to the peripheral edge of graft causing peripheral anterior synechiae,
  pupilloplasty is performed to tighten the iris preventing it from causing synechial adhesions that would increase the risk of angle closure and graft failure.

Advantages

• Faster and easier to perform compared to other pupilloplasty techniques – (Modified Siepser’s and McCanell method which requires more than

  two passes to be made from the anterior chamber, as well as additional manipulation of the iris tissue).

• Reduced postoperative inflammation and faster visual recovery

• Effective in Urrets Zavalia syndrome who present with raised IOP and persistent pupil dilation.

• Prevents secondary angle closure, breaking the formation of peripheral anterior synechia and inhibits mechanical blockage.

• Useful in treating patients with higher order corneal aberrations, improves visual quality and extended depth of focus.

• Effective in selected cases of secondary angle closure, along with silicon oil induced glaucoma.

• Reconstructing the pupil this way prevents patients from glare, photophobia and untoward images formed by reflection of light

Disadvantages

• Limited dilation- to examine the posterior segment – (In cases of retinal detachment, it is possible to YAG the iris and undo procedure if needed).

• Chances of touching crystalline lens during procedure and risk of cataract formation – So preferably done in pseudophakic eyes.

Written by: Dr. Soundari S – Regional Head – Clinical Services, Chennai