Refractive surgery beyond 2020

Abstract

Refractive surgery refers to any procedure that corrects or minimizes refractive errors. Today, refractive surgery has evolved beyond the traditional laser refractive surgery, embodied by the popular laser in situ keratomileusis or 'LASIK'. New keratorefractive techniques such as small incision lenticule extraction (SMILE) avoids corneal flap creation and uses a single laser device, while advances in surface ablation techniques have seen a resurgence in its popularity. Presbyopic treatment options have also expanded to include new ablation profiles, intracorneal implants, and phakic intraocular implants. With the improved safety and efficacy of refractive lens exchange, a wider variety of intraocular lens implants with advanced optics provide more options for refractive correction in carefully selected patients. In this review, we also discuss possible developments in refractive surgery beyond 2020, such as preoperative evaluation of refractive patients using machine learning and artificial intelligence, potential use of stromal lenticules harvested from SMILE for presbyopic treatments, and various advances in intraocular lens implants that may provide a closer to 'physiological correction' of refractive errors.

Fig. 1. High-resolution swept-source optical coherence tomography imaging of the anterior segment of a pseudophakic eye.

High-resolution swept-source OCT imaging of the anterior segment of a pseudophakic eye in which after piggy-back implantation of a sulcus lens to fix a refractive surprise after uneventful cataract surgery (ANTERION, Heidelberg Engineering GmbH, Heidelberg, Germany).

Fig. 2. Precision high-frequency ultrasound device (50 MHz) imaging of the cornea.

Ultrasound imaging can accurately image behind the iris allowing for improved ICL sizing. In addition to measurements of the anatomic structures comprising the anterior of the eye such as anterior chamber, the instrument can delineate the corneal epithelial layer thickness (ArcScan Insight 100, ArcScan Inc, Golden, USA).

Fig. 3. Average lens density (ALD) quantification with swept-source optical coherence tomography (SS-OCT).

Six radial B-scans including the lens were acquired three times at each meridian (0, 30, 60, 90, 120, and 150 degrees). An algorithm measured the density of the region of interest on a scale of 0–255 pixel intensity units. In a recent study, an SS-OCT ALD measurement of 73.8 pixel units or greater strongly suggested the presence of cataract, with a sensitivity of 96.2% and a specificity of 91.3%.

Fig. 4. Central flap thickness reproducibility comparing microkeratome and femtosecond laser.

Graph showing the central flap thickness reproducibility for all studies published between 1998 and 2014, grouped by mechanical microkeratome (blue) and femtosecond laser (red).

Fig. 5. Series of diagrams showing the femtosecond cutting sequence for a SMILE procedure.

(1) lenticule interface from out-to-in, (2) lenticule side cut, (3) cap interface from in-to-out, and (4) the small incision(s). Reprinted with permission from Reinstein et al. [117].

Fig. 6. Series of images showing the standard surgical technique for SMILE.

Reprinted with permission from Reinstein et al. [117].

Fig. 7. Corneal stroma enhancement with a decellularized corneal stroma lenticule in a patient with advanced keratoconus.

Slit-lamp pictures 1 week (top-left) and 3 months after surgery (top-right; note the complete transparency recovery). Corneal OCT image (down): the implanted lenticule is easily identified 6 months after surgery (white arrows).

Fig. 8. Slit-lamp photograph of an eye with intracorneal implants.

Intracorneal ring implanted in a patient with keratoconus.

Fig. 9. Raindrop inlay.

Slit lamp (left; white arrows point the edges of the inlay) and anterior segment optical coherence tomography (OCT) pictures (right). Observe how the thin inlay is seen in the OCT image and it appears surrounded by a mild stromal haze (yellow dashed line).

Fig. 10. Kamra inlay.

Slit-lamp pictures 3 months (left; observe the peripheral microperforations to allow corneal nutrition) and 3 years after implantation (middle). Note the progressive moderate haze associated with visual loss that justified inlay explantation, remaining a donut-shape central corneal scar still visible 4 years after inlay removal (right).

Fig. 11. Anterior chamber iris-claw intraocular lenses.

Left: rigid polymethyl-methacrylate (PMMA) lens. Right: foldable lens made of polysiloxane. Both from Ophtec BV, the Netherlands and J&J, USA.

Fig. 12. Example of implantable collamer lens (ICL) in situ.

The central port allows aqueous flow from the posterior chamber to the anterior chamber in order to maintain the normal physiology of the anterior segment of the eye. The EVO+ Visian ICL (STAAR Surgical, USA) introduced in 2016 now was an extended optical zone.

Fig. 13. Example of multifocal intraocular lens implants recently available.

Left: trifocal intraocular lens implant. Right: hybrid design extended depth of focus (EDOF) intraocular lens implant.

Fig. 14. Photographs of a small aperture intraocular lens implant before and after implantation in situ.

Example of small aperture intraocular lens implant, which utilizes the pinhole principle to increase the depth of focus to about 3D.