Scleral surgery for the treatment of presbyopia: where are we today?

Abstract

Presbyopia corrections traditionally have been approached with attempts to exchange power, either at the cornea or the lens planes, inducing multifocality, or altering asphericity to impact the optical system. Treatments that affect the visual axis, such as spectacle and contact lens correction, refractive surgeries, corneal onlays and inlays, and intraocular lenses are typically unable to restore true accommodation to the presbyopic eye. Their aim is instead to enhance 'pseudoaccommodation' by facilitating an extended depth-of-focus for which vision is sufficient. There is a true lack of technology that approaches presbyopia from a treatment based or therapy based solution, rather than a 'vision correction' solution that compromises other components of the optical system. Scleral surgical procedures seek to restore true accommodation combined with pseudoaccommodation and have several advantages over other more invasive options to treat presbyopia. While the theoretical justification of scleral surgical procedures remains controversial, there has nevertheless been increasing interest and evidence to support scleral surgical and therapeutic approaches to treat presbyopia. Enormous progress in scleral surgery techniques and understanding of the mechanisms of action have been achieved since the 1970s, and this remains an active area of research. In this article, we discuss the historic scleral surgical procedures, the two scleral procedures currently available, as well as an outlook of the future for the scleral surgical space for treating presbyopia.

Keywords: Accommodation; Presbyopia; Presbyopia treatment; Scleral surgery.

Fig. 1

VisAbility Micro-Insert surgical procedure. a) VisAbility Micro-Insert; b) Sclerotome and docking station creating a partial thickness tunnel in the sclera. (Images courtesy of Refocus Group, Dallas, USA)

Fig. 2

LaserACE surgical procedure. a) The three critical zones of significance as measured from the anatomical limbus; b) Restored mechanical efficiency and improved biomechanical mobility (procedure objectives). Reprinted with permission from [50]

Fig. 3

LaserACE surgical technique. Photo a) Quadrant marker; b) Matrix marker; c) Corneal Shield; d) LaserACE micropore ablation; e) Subconjunctival Collagen f) Completed 4 quadrants. Reprinted with permission from [50]

Fig. 4

Uncorrected (lightly colored) and distance-corrected (darkly colored) visual acuity at a distance 4 m, intermediate (60 cm), and near (40 cm) for a) Monocular and b) Binocular patient eyes. Error bars represent mean ± SD. Reprinted with permission from [50]

Fig. 5

Average participant ratings from the CatQuest 9SF survey. Responses ranged from + 2, indicating no difficulty, to −2, indicating great difficulty. Error bars represent mean ± SE. Reprinted with permission from [50]

Fig. 6

A representative figure of the depth of focus (DoF). Visual Strehl ratio based upon the optical transfer function (VSOTF) is computed as a function of defocus using a through-focus curve

Fig. 7

A representative figure of the effective range of focus (EROF) for a young (32-year-old) eye. Visual Strehl ratio based upon the optical transfer function (VSOTF) is computed as a function of defocus using a through-focus curve. Through-focus curves are shown for distance (green) and near (red)

Fig. 8

A representative figure of the effective range of focus (EROF) for an old (59-year-old) eye. Visual Strehl ratio based upon the optical transfer function (VSOTF) is computed as a function of defocus using a through-focus curve. Through-focus curves are shown for distance (green) and near (red)

Fig. 9

A representative figure of the effective range of focus (EROF) for a patient eye (60-year-old; 103-OD) after LaserACE. Visual Strehl ratio based upon the optical transfer function (VSOTF) is computed as a function of defocus using a through-focus curve. Through-focus curves are shown for distance (green) and near (red). Reprinted with permission from [56]