Pinhole pupilloplasty enhances visual acuity, image quality

The procedure is easy to perform and does not require special instrumentation.

Issue: February 10, 2019

ByAmar Agarwal, MS, FRCS, FRCOphth

ByPriya Narang, MS

Pinhole visual acuity assessment is an important form of preoperative examination performed in cases with higher-order refractive error that helps to apprise the surgeon and the patient of the best possible vision that can be achieved after an intraocular surgery.

The pinhole helps to filter stray light from the periphery of the cornea in cases with higher-order corneal irregular astigmatism (Figure 1). The pinhole effect blocks distorted and unfocused light rays emanating from the peripheral cornea and isolates more focused central and paracentral rays through the central aperture, thereby enhancing visual acuity and image quality. The pinhole effect can be achieved with surgical pupilloplasty that reduces the circle of confusion on the retina and results in a sharper image (Figure 2). This is pinhole pupilloplasty, a term suggested by David Chang, or PPP.

**Figure 1.** A case of a fixed dilated pupil with high astigmatism. It needs pinhole pupilloplasty to solve the glare and astigmatism.

Pinhole IOL and PPP — **Figure 2.** Pinhole IOL blocks the peripheral rays of light (a). PPP blocks the peripheral rays of light (b).

Secondly, when the pupil is narrowed down, the entire light spectrum enters the eye through the small central pinhole pupil. According to the Stiles-Crawford effect (Figure 3), light that enters near the center of the pupil produces a greater photoreceptor response as compared with the light that enters through the edges of the peripheral pupillary margin. Therefore, with the pinhole effect, the patient sees the object clearly and well illuminated due to greater photoreceptor sensitivity.

Technique

To mention in brief, single-pass four-throw (SFT) pupilloplasty is performed by passing a 10-0 suture attached to a long arm needle from the proximal iris defect and threading it into the barrel of a 26-gauge needle introduced from the opposite side (Figure 4). A Sinskey hook is introduced inside the anterior chamber, and a loop is withdrawn. The suture end is passed through the loop four times, and both suture ends are pulled. The knot slides inside the eye and is cut with micro-scissors. The procedure of SFT is repeated until adequate PPP size is achieved.

PPP can be done with any surgical technique for pupilloplasty, although we adopted SFT pupilloplasty for achieving PPP.

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**Figure 4.** A case of pre-Descemet’s endothelial keratoplasty with PPP. Vision was 20/20 and J1 without glasses as there is an extended depth of focus created.

Pinhole marker images of the microscope can be used to get a centrally located pupil and the pinhole pupil size — **Figure 5.** Pinhole marker or Purkinje images of the microscope can be used to get a centrally located pupil and the pinhole pupil size to 1.5 mm.

A pinhole marker (Figure 5) sized 1.5 mm is employed for gauging the exact dimension of the PPP that is achieved. Centration of PPP is achieved by the reflection of the microscope light into the center of the pupil.

The principle of achieving a pinhole effect has been employed at the level of the cornea and the lens to enhance depth of focus. We have contemplated achieving pinhole acuity in cases with irregular corneal astigmatism by modifying the pupil size. The major limitation that a surgeon can come across after doing a PPP is the scope of visualizing a fundus. With the procedure of SFT, it has been documented that after mydriasis there is sufficient dilation of the pupil to allow adequate fundus visualization. The advantages of performing a PPP are that it is easy to perform, is cost-effective and does not require any special device to perform.

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.

For more information:
Amar Agarwal, MS, FRCS, FRCOphth, is director of Dr. Agarwal’s Eye Hospital and Eye Research Centre. Agarwal is the author of several books published by SLACK Incorporated, publisher of Ocular Surgery News, including Phaco Nightmares: Conquering Cataract Catastrophes, Bimanual Phaco: Mastering the Phakonit/MICS Technique, Dry Eye: A Practical Guide to Ocular Surface Disorders and Stem Cell Surgery and Presbyopia: A Surgical Textbook. He can be reached at 19 Cathedral Road, Chennai 600 086, India; email: dragarwal@vsnl.com; website: www.dragarwal.com.
Priya Narang, MS, can be reached at Narang Eye Care & Laser Centre, Ahmedabad, India; email: narangpriya19@gmail.com.

Disclosures: Agarwal and Narang report no relevant financial disclosures.