Pinhole pupilloplasty can play role in post-keratoplasty irregular corneas
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Pinhole pupilloplasty is a method to reduce the size of a pupil to as small as a pinhole.
Pinhole optics have been used for various indications such as highly irregular astigmatism and corneal scar. Single-pass four-throw pupilloplasty has been shown to have good functional and anatomical outcomes for various indications including angle-closure glaucoma, Urrets-Zavalia syndrome (UZS) and post-corneal ectasia-induced aberropia. In this column, we would like to share our experience of post-keratoplasty cases wherein pinhole pupilloplasty has shown good functional outcomes.
Source: Dhivya Ashok Kumar, MD, FRCS, FICO, FAICO, and Amar Agarwal, MS, FRCS, FRCOphth
Keratoplasty and corneal surface
Penetrating keratoplasty involves the transplantation of the entire cornea for optical indications such as bullous keratopathy, corneal decompensation, congenital dystrophy and late-onset Fuchs’ endothelial dystrophy. The surgical scenario involves the placement of 12 to 14 radial sutures, resulting in surgical suture-induced astigmatism. Rarely, irregular corneal graft-host junction can induce topographic changes. Very rarely, recurrence of the primary pathology can add to the surface abnormality in these eyes. The challenges faced by surgeons include graft rejection, suture-induced astigmatism and higher-order aberration-induced visual blur, among others. Optical quality may be altered due to aberrations on the cornea causing poor vision. Eyes that have undergone deep anterior lamellar keratoplasty for conditions such as anterior stromal scar and keratoconus can still have sutures, which can cause irregular topography. The alternative option in these eyes apart from spectacle correction is a contact lens, which may be tedious in all patients. Moreover, a fixed dilated pupil, termed as UZS, is often noted in any type of keratoplasty.
Requirements for pinhole pupilloplasty
Preoperative Scheimpflug imaging or corneal topography is essential to assess the topography of the corneal graft. The corneal higher-order aberrations profile can be obtained from the Holladay report on Pentacam (Oculus) (Figure 1). Higher values of corneal higher-order aberrations are associated with more visual blur. Documentation of preoperative corneal thickness, pupil size and corneal wavefront is necessary to decide for intervention. Anterior segment OCT is needed to assess the depth of the corneal scar and preoperative pupil size. Endothelial cell count analysis helps to assess graft endothelial status and prepare for precautionary intraoperative measures in eyes with a low count.
Preoperatively, uncorrected visual acuity with a handheld pinhole template (Epsilon) was recorded for all eyes (Figure 2). The pinhole template comprises multiple holes that range from a diameter of 0.5 mm to 4 mm with subsequent increments of 0.5 mm. The pinhole size that provided the best visual acuity to the patient in a dimly lit room with an illuminated Snellen distant visual acuity chart through the pinhole template was recorded, and an attempt was made intraoperatively to achieve the same pinhole size. For intraoperative measurement of pupil size, a calibrated reticle was imposed onto the microscope eyepiece. Hence, when the surgeon looks through the microscope, the reticle image is imposed upon the eye of the patient. The surgeons employed a 5-mm reticle with 20 divisions in which each division represented 0.25 mm of distance with magnification set at one time. The surgeon also confirms the position of Purkinje image 1 (P1) intraoperatively to check the position.
Timing of procedure
Pinhole pupilloplasty (PPP) can be performed if improvement is noted in the pinhole template and significant corneal higher-order aberrations are noted. Confirmation of a quiet anterior chamber is needed for pupilloplasty as uveal tissue is manipulated. It can be performed 6 months after keratoplasty, or it can be combined with cataract surgery wherever needed. Steroids may be needed in the immediate postoperative period. Informing the patient about potential complications of operating in an eye with a graft and patient consent are needed.
Pupilloplasty after keratoplasty
The common indications to combine PPP in post-keratoplasty cases include eyes with highly irregular astigmatism, a fixed dilated pupil due to UZS, post-DALK high astigmatism and, rarely, post-traumatic corneal scar with irregular corneal sutures following corneal tear. The surgery is performed under peribulbar anesthesia. Surgical planning of the placement of paracentesis incisions is decided ahead of the procedure by examining the corneal topography. The preferred placement of paracentesis incisions is in the steep corneal axis, and an ophthalmic viscosurgical device is injected inside the anterior chamber to coat the corneal endothelium. A 9-0 polypropylene suture attached to a long needle is introduced without disturbing the corneal layers. The needle is passed through the proximal iris tissue along the pupillary edge and subsequently from the distal iris tissue. A 30-gauge needle is introduced from the opposite quadrant, and the suture needle is threaded into it and withdrawn outside. A Sinskey hook is subsequently passed, and a suture loop is withdrawn. The suture end is passed through the loop four times in the same direction, forming the single-pass four-throw pupilloplasty.
Both suture ends are pulled, leading to sliding of the loop inside the eye, thereby approximating the pupillary edges. Microscissors are introduced, and the suture knot is cut. The procedure is repeated until the optimum pupil size is achieved. The pupil is centered away from the scarred cornea intraoperatively, which is confirmed with corneal P1 reflex that emanates from the coaxial light of the microscope. An intraoperative pupil gauge can also help confirm the size of the pupil (Figure 3). The paracentesis incisions are then hydrated. One can combine a phacoemulsification procedure with PPP in eyes with coexisting cataract. In this scenario, phacoemulsification is initially performed, followed by IOL placement and PPP.
Observations
The postoperative period in these eyes requires topical and oral steroids for 1 month. Tapering of steroids can be performed in subsequent follow-up. In our short series of post-DALK PPP cases, visual acuity improved from 1.46 ± 0.4 logMAR preoperatively to 0.16 ± 0.15 logMAR postoperatively (Figure 4). No significant inflammation was noted, and none of the eyes experienced graft rejection (Figure 5). Corneal clarity was well maintained at 1-year follow-up.
Conclusion
The PPP technique uses the pinhole optics principle to impart good visual acuity and improve optical quality. The pinhole moves off the light emanating from the peripheral cornea and allows the passage of central and paracentral rays. This enhances visual acuity and quality by reducing the aberrations of the optical system as a whole. The use of PPP in post-keratoplasty eyes is highly beneficial by avoiding the discomfort of using contact lens or other alternative options of corneal intervention.
- References:
- Kumar DA, et al. J Cataract Refract Surg. 2017;doi:10.1016/j.jcrs.2017.07.027.
- Kumar DA, et al. J Cataract Refract Surg. 2024;doi:10.1097/j.jcrs.0000000000001353.
- 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.
- Trindade CLC, et al. JCRS Online Case Rep. 2015;doi:10.1016/j.jcro.2014.12.002.
- For more information:
- Amar Agarwal, MS, FRCS, FRCOphth, director of Dr. Agarwal’s Eye Hospital and Eye Research Centre, is the author of several books, 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 aehl19c@gmail.com; website: www.dragarwal.com.
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