Surgeons describe repositioning, recentration and resizing of pinhole pupilloplasty
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Pinhole pupilloplasty has been documented to improve visual performance in cases with higher-order aberrations. The importance of performing an iris reconstruction and PPP around the Purkinje 1 reflex has been clearly demonstrated.
We came across a case in the postoperative period with an eccentrically positioned pinhole pupilloplasty (PPP) that required repositioning and recentration. We realized that the exact pupil size that achieves the best visual performance is unique to each patient depending on their specific aberrations. A multiple pinhole gauge was developed to find the optimal pinhole for a specific patient. Purkinje 1 (P1) reflex is the target center for PPP, and an optimal patient pinhole size with perfect alignment in the desired location is necessary to achieve the optimal refractive visual output.
A PPP procedure essentially mandates removal of the natural lens due to its propensity to hit the lens with the suture needle. As a result, patients are rendered pseudophakic. We hereby describe the technique to reposition, recenter and resize PPP along with an IOL exchange due to an associated refractive surprise. To the best of our knowledge, repositioning and resizing of PPP have not been performed or reported until now.
Calibrating and gauging the pinhole size
The essential steps to achieve a perfect functional pinhole include appropriate preoperative evaluation of the pinhole size required to optimize visual acuity and intraoperative gauging of the pupil size achieved.
Source: Priya Narang, MS, and Amar Agarwal, MS, FRCS, FRCOphth
To meet the first requirement, a pinhole device has been designed by Dr. Jack Holladay (Figure 1). The device is made up of an octagonal titanium anodized blue material, is 1.6 mm thick, and comprises a set of eight pinholes that range from 0.5 mm to 4 mm in 0.5 mm steps. During preoperative assessment, the patient is asked to select the pinhole size that allows them to read the smallest print on the visual acuity chart, and the optimal pinhole size diameter is recorded. Intraoperatively, an attempt is made to achieve the same pinhole size that helped achieve the best visual acuity for the patient.
For the second step, a calibrated reticle is 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 distance between each segment of the reticle depends upon the magnification used during surgery. The surgeon employed a 5-mm reticle with 20 divisions. Hence, each division of the reticle represents 0.25 mm of distance with magnification set at one time. With two times magnification, each reticle would represent 0.125 mm. Therefore, while calculating the pupil aperture in PPP, the surgeon should take into account the magnification of the surgical microscope, the total number of lines on the reticle and the value of each reticle division. The pinhole gauge is autoclavable, and alternatively, it may be used to match the pupil size during surgery in case of unavailability of the calibrated reticle.
Technique
Two paracentesis incisions were made at the 5 o’clock and 8 o’clock positions, with care being taken to evade the margins of the penetrating keratoplasty graft. The anterior chamber was formed with ophthalmic viscosurgical device. The micro-scissors and forceps were introduced from the paracentesis, and the suture loop of the PPP knot was cut with micro-scissors (Figure 2). The cut suture was removed, and the IOL was dialed out of the capsular bag with a Lester hook and manipulated into the anterior chamber. Conjunctival peritomy was done followed by a scleral tunnel that was made at the 6 o’clock position. The IOL was explanted from the scleral tunnel, and a corrective IOL was implanted into the bag. The scleral tunnel was sutured with a 10-0 nylon suture (Figure 3).
The technique of performing PPP has been described before. In brief, PPP was performed with 10-0 polypropylene suture, and the pupil was centered around the P1 reflex. Next, the image of the reticle was superimposed as it was considered for calculating the diameter and size of the PPP. It was noticed that the previous pupil diameter was 3.5 mm, whereas the patient reported best visual acuity with 1 mm diameter. Therefore, PPP was performed to achieve the desired 1 mm size of the pupil.
Case details
A 42-year-old man with keratoconus presented at our center with apical fibrosis and associated cataract. Therefore, PK was performed with cataract extraction and IOL implantation along with PPP. Post-surgery, a refractive surprise of +6.00 D sphere and –13.3 D cylinder at 107° was encountered, and the visual acuity was recorded to be 20/400. It was also observed that the PPP was decentered, and therefore, recentration was deemed necessary. Using the technique described above, the PPP was repositioned and recentered around the P1 reflex along with an IOL exchange. The visual acuity improved to 20/200, but it was observed that the pupil diameter was 3.5 mm. After resizing the pupil diameter to 1 mm, unaided visual acuity improved to 20/40 (Figure 4).
Discussion
Peer studies have documented satisfactory visual outcomes with PPP in cases with higher-order aberrations. Consequently, in this case, PPP was performed apart from PK and IOL implantation. The two crucial aspects for PPP are size of the pinhole and appropriate centration of the pupillary aperture. A pinhole aperture that is too small can hamper a light wave and cause diffraction with loss of image resolution. A pinhole size that ranges from 0.94 mm to 1.75 mm was concluded to be the most effective in a recent study that evaluated the effect of different sizes of pinhole on visual output. Most of the commercial instruments incorporate 1.2-mm pinhole aperture size.
The desired pupil size can be achieved by using a reticle that can be attached to the eyepiece of the surgical microscope. This helps the surgeon to gauge the size of the pinhole pupil intraoperatively. Holladay’s pinhole device helps to preemptively and subjectively judge the size of the pupil, which can enhance visual potential for the patient, and the reticle helps to achieve the pretargeted size by adding intraoperative precision. In clinical settings, the authors observed varying levels of patient satisfaction and improved visual image quality with different pinhole sizes in cases with higher-order aberrations. There is no one rule that fits all. Therefore, a pinhole device was made with different pinhole aperture sizes to try to customize the pupil size according to the patient’s requirement.
Appropriate centration is vital for all devices that work on the principle of small-aperture optics. Ray tracing for corneal inlays depicted great reduction in image quality with minimal aperture decentrations of 0.5 mm. Variations in the centration of a pinhole sulcus implant and decentration requiring a surgical maneuver have been reported. Although we did not perform any objective method to analyze the effect of aperture decentration after PPP, there was a significant improvement in visual acuity after recentration of PPP. Secondly, for appropriate centration, it is essential to center the PPP around the P1 reflex. We presume that the PPP was initially decentered either due to rotation of the globe after peribulbar block or because of surgical error in locating the P1 reflex due to some alteration induced in the optical pathway due to placement of the full-thickness corneal graft.
PPP was performed with the single-pass four-throw technique. Therefore, the intraocular surgical knot comprises an approximation loop and does not have a securing loop. Hence, logically, the knot can be opened by pulling one end of the 9-0 suture, and the loops can be easily maneuvered and detangled by pulling with end-opening forceps. But this was avoided because in PPP, the stress on the iris tissue was present in all quadrants due to an endeavor to achieve a pinhole pupil. Therefore, the surgeons preferred to cut the suture loop with micro-scissors to avoid traction and undue stress on the iris tissue. The additional benefit of PPP is the wide range of defocus that offsets some amount of residual refractive error in IOL power calculation. But in our case, the error was substantial. Hence, an IOL exchange was performed.
PPP is essentially a refractive procedure for higher-order aberrations. Adequate preoperative subjective evaluation with appropriate intraoperative objective analyses can help optimize visual outcomes, and accurate centration is crucial. Nevertheless, recentration is possible, and the technique outlined and highlighted here helps to achieve satisfactory outcomes.
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- 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 published by SLACK Books, sister company of Healio publisher 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: aehl19c@gmail.com; website: www.dragarwal.com.
- Priya Narang, MS, can be reached at Narang Eye Care & Laser Centre, Ahmedabad, India; email: narangpriya19@gmail.com.
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