PEARL is an acronym for PrEsbyopic Allogenic Refractive Lenticule. This technique was described by Soosan Jacob as a treatment for presbyopia. The PEARL inlay utilizes the principle of a shape-changing inlay in order to improve near vision.
Corneal inlays can be classified as pinhole aperture inlays (Kamra, AcuFocus), shape-changing inlays (Raindrop, ReVision Optics; PEARL inlay) and refractive optic inlays (Flexivue Microlens, Presbia; Icolens, Neoptics). They can also be classified as synthetic inlays, including most inlays currently available on the market, and allogenic inlays, such as the PEARL inlay.
The PEARL inlay has the advantage of utilizing allogenic tissue for implantation. Synthetic material within the cornea can lead to an inflammatory response, potential interference with glucose, ionic diffusion into the anterior stroma above the implant, and peri-inlay deposits. Allogenic tissue, on the other hand, allows good integration into the cornea and avoids problems related to insertion of synthetic material into the cornea. It allows unhindered passage of oxygen and nutrients, thus ensuring stable corneal conditions and decreasing the risk for corneal necrosis and melt. As with synthetic corneal inlays, it has the advantages of reversibility and adjustability.
The lenticule from a healthy screened individual undergoing femtosecond laser-assisted small incision lenticule extraction refractive surgery for myopic correction is stored in corneal storage medium for later use. An average central lenticular thickness between 65 µm and 70 µm is suitable. The PEARL technique then utilizes the femtosecond laser to create a 120 µm deep pocket in the presbyopic patient’s eye. The stored SMILE lenticule is spread out, dried with a surgical sponge and punched centrally to create a 1-mm disc of allogenic tissue. This PEARL inlay is implanted into the femtosecond-created pocket under the first Purkinje reflex marked previously on the slit lamp with the patient fixating coaxially. Implantation can be done with forceps and is easy. Centration can be verified through the surgical microscope as well as immediately postoperatively with an Orbscan (Bausch + Lomb) (https://www.youtube.com/watch?v=8H4Ns1b8L3M).
Corneal inlays are additive technologies and thereby preserve future options for further treatment. Thus, they have an advantage over monovision LASIK and presbyLASIK. The PEARL inlay has the further advantage of utilizing allogenic tissue. It increases the central radius of curvature, resulting in a hyperprolate corneal shape, and thereby improves depth of focus. In our studies, there was an improvement in near vision between three and five lines and an improvement in reading speed. Similar to other inlays, the PEARL inlay gave good uncorrected near and intermediate vision in the operated eye with a slight decrease in distance vision. However, being only 1 mm in size, the effect on distance vision was low. Night vision symptoms were minimal and generally not significant enough to interfere with driving. However, all patients should be warned of these possibilities in the preoperative period, and the inlay should be implanted in the nondominant eye, similar to other corneal inlays. The PEARL inlay has the advantage of being invisible to the naked eye. This is an advantage in light-colored eyes over current pinhole aperture inlays. The PEARL inlay also creates no interference with fundus evaluation or autoperimetry. For patients with coexisting refractive error, simultaneous LASIK or SMILE may be done followed by implantation of the PEARL lenticule. Similarly, in pseudophakic patients, refractive surgery for any existing refractive error may be followed by a PEARL inlay under the flap.
A potential disadvantage of this technique is the risk for stromal rejection from donor tissue. However, this was not seen by us. The use of low-dose postoperative steroids for about 4 months, together with the minute antigenic load of pure corneal stroma (without the more antigenic epithelium or endothelium) that may be too small to provoke a reaction in the immunologically privileged cornea, as well as the more rapid repopulation of the PEARL inlay from all sides by the patient’s own keratocytes all possibly play a part in further decreasing immunogenicity.
SMILE lenticule reimplantation has been done previously in both animal models as well as in patients with hypermetropia, aphakia and keratoconus with a favorable efficacy and safety profile. In the future, complete femtosecond preparation of prescreened allogenic lenticules together with cryopreservation for long-term storage will allow this technique to be more applicable universally even in centers without the facility for SMILE refractive surgery.
- Jacob S, et al. J Refract Surg. 2017;doi:10.3928/1081597X-20170111-03.
- 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: firstname.lastname@example.org; website: www.dragarwal.com.
- Soosan Jacob, MS, FRCS, DNB, is director and chief of Dr. Agarwal’s Refractive and Cornea Foundation at Dr. Agarwal’s Eye Hospital, Chennai, India. She can be reached at email: email@example.com.
Disclosures: Agarwal and Jacob report no relevant financial disclosures.