PRESBYOPIA IS DESCRIBED AS loss of accommodative lens power resulting in poor visual acuity at near distances. It is the most common cause of near visual impairment in adults older than 40. This condition is estimated to affect nearly 2 billion people worldwide, many of whom do not have access to prescription reading glasses.¹ The purpose of this review is to discuss surgical options to address presbyopia, including modern and upcoming technologies.

Literature Review

The authors performed a comprehensive review of the current literature available in the PUBMED and MEDLINE databases. The search criteria included articles discussing surgical treatment options for presbyopia.

Multiple effective surgical therapies exist for treatment of presbyopia. These treatments include procedures that alter the cornea, sclera, and crystalline lens, in addition to several presbyopia correcting intraocular lenses (IOLs). This article focuses on more novel surgical corrections and how they may be incorporated into regular practice.

Surgical correction of presbyopia continues to be an area of interest due to its prevalence within the aging population. Each surgical option discussed has advantages and disadvantages, necessitating careful patient selection for each procedure. The ultimate aim of presbyopia treatment is to restore true accommodative ability without sacrificing near or distance visual performance.

Surgical Treatments

Surgical treatments for presbyopia fall into two categories: pseudoaccommodative and accommodative. Pseudoaccommodative approaches provide enhanced near visual acuity without restoring lenticular focusing ability. The majority of corneal procedures and premium IOLs are categorized as pseudoaccommodative. The accommodative approach attempts to restore the true focusing power of the eye at a range of distances. The accommodative approach is considered the ultimate goal of surgical presbyopia management because it imitates the natural physiological mechanism of focusing used by the young, native crystalline lens.

More recently, efforts have been made to quantify distinct grading criteria to describe the progressive aging of the lens. Dysfunctional lens syndrome (DLS), coined by Waring et al, stages the aging lens using objective measurements.^2,3 This allows physicians to offer personalized surgical correction aimed at treating presbyopia based on quantifiable data, such as light scatter, higher order aberrations (HOAs), contrast sensitivity, and lenticular opacification. The authors have included a discussion of both established and novel surgical approaches for the presbyopic patient.³

Sources included in this review were drawn from peer-reviewed literature obtained via a search of electronic medical databases. The search criteria utilized keywords of surgical presbyopia treatment and DLS. Fewer published data were available for some of the novel surgical techniques reviewed below; therefore, data presented at peer-reviewed surgical conferences were evaluated and included based on the merit of supporting evidence. In addition, the authors have included a brief mention of some of the more traditional approaches to surgical correction of presbyopia.

Traditional Surgical Approaches

Several well-established surgical approaches exist for the treatment of presbyopia. Such options traditionally act as pseudoaccommodative agents via creation of a multifocal cornea. Well-studied modalities include corneal inlays, corneal onlays, and presbyopic ablation profiles (PresbyLASIK) using femtosecond and excimer lasers. These treatments may be limited by their photic side effects, such as glare and halos.^4,5

Intraocular Lenses

Cataract surgery remains the most common procedure for surgical presbyopia correction. Newer IOL technologies have improved quality of near and distance vision. Presbyopia-correcting IOLs use a variety of refractive and diffractive optics to enhance range of vision while attempting to reduce night dysphotopsias. Examples of popular implant designs include diffractive bifocal, trifocal, extended depth of focus, and hybrid IOL designs.^6,7,8,9

Research continues to develop in the field of true accommodative IOLs, which mimic the in vivo focusing power of the native crystalline lens. Accommodative IOLs harness the natural contraction of the ciliary muscle to induce anteroposterior shift of the IOL elements, thus changing the dioptric power of the implant in vivo. The majority of these lenses employ a dual optic design that has an anchoring element within the capsular bag.^10,11 An alternative approach is the placement of a deformable polymer that molds to the capsular bag, mimicking the natural elasticity of the crystalline lens.¹² Such implants offer intriguing new developments; however, current studies have yet to produce consistent, reliable results.

In addition to accommodative IOLs, adjustable IOLs, such as the Light Adjustable Lens (LAL) (RxSight), allow the surgeon to alter, or “fine-tune,” the final refractive outcome. This technology utilizes macromers that are sensitive to light within the ultraviolet spectrum. Upon exposure to a digital light delivery device, the macromers within the lens photopolymerize, inducing a change in refractive index.¹³ Differing application patterns can be used to treat myopic, hyperopic, and astigmatic patients. The light delivery device can also be applied to create positive or negative asphericity, resulting in a multifocal outcome that may be useful for patients desiring adequate uncorrected near and distance vision.^13,14

Other adjustable lens options include Femtosecond Laser Refractive Index Shaping or the Perfect Lens system (Perfect Lens LLC). This technology applies femtosecond laser to the IOL optic, changing the hydrolysis properties of the implant and allowing for significant adjustments of sphere, cylinder, and asphericity. The Perfect Lens system also allows for the application of a multifocal pattern, providing a tailored lens experience to each patient.^15,16

Adjustable lens technology aims to reduce the need for IOL exchange and to provide the patient with more options without risking an additional surgical procedure.

Novel Treatments

Several novel approaches have yielded promising results in the surgical treatment of presbyopia. One theory related to the etiology of presbyopia postulates that loss of accommodative amplitude is related to stiffening of the scleral fibers in conjunction with the aging process. As the scleral fibers undergo a natural crosslinking, the ocular structures overlying the ciliary body become more rigid, leading to decreased excursion of ciliary muscles.¹⁷ Laser scleral microporation attempts to preserve accommodative ability by disrupting the natural crosslinking of scleral fibers in this area. During the procedure, an Er:YAG laser creates small pores within scleral tissue, aiming to improve the elasticity of scleral fibers in relation to the ciliary body. Laser is applied in quadrants of the sclera from 0.5 mm to 7.3 mm at a depth of 80% scleral thickness. A recent study followed 26 patients who underwent bilateral laser scleral microporation. At 24 months postoperatively the study showed a significant improvement in uncorrected near visual acuity (UNVA) and distance-corrected near visual acuity (DCNVA). Additional benefits of the procedure include that the laser treatment may reduce intraocular pressure, although it is unclear whether this result is sustained and whether the result is real versus artifactual.^18-20

An additional scleral procedure that remains under investigation is the use of scleral expansion bands. The mechanism of these bands is based on Schachar’s theory that loss of accommodation is secondary to continued growth of the lens, reducing the distance between the lens equator and the origin of the zonules on the ciliary processes. The goal of the procedure is to expand this distance through insertion of polymethyl methacrylate bands into the sclera, thereby increasing zonular tension.²¹ Scleral expansion bands have thus far been unable to yield consistent improvement in accommodation and have been associated with complications, including anterior-segment ischemia and expulsion of the implant. Studies have reported a variety of results ranging from a 0- to 1.5-D improvement in accommodation.^21-23

The most widely adopted etiology of presbyopia is Helmholtz’s theory that the loss of accommodative power is a result of progressive sclerosis of the natural lens.²⁴ With that mechanism in mind, novel treatments aim to reduce this gradual stiffening and restore the lens’ natural elasticity. Current clinical trials aim to soften the phakic lens utilizing femtosecond laser pulses. Results of in vivo animal studies demonstrate that “lens softening” may yield an additional 2 D of accommodation.²⁵ The exact location and pattern of the femtosecond laser pulses remain under development. The goal of this therapy is to maximize improvement in accommodation while reducing the incidence of HOAs and lens opacification.^25,26

Although prior corneal procedures have been limited by their induction of glare and halos, newer corneal procedures aim to reduce such phenomena. Laser induced refractive index change (LIRIC, Clerio Vision) uses femtosecond laser to alter the structure of corneal stromal fibers. The laser does not create a flap in the cornea (as in the case of LASIK) but instead denatures collagen fibers, resulting in a focal dehydration of the corneal stroma.^27,28 Studies have shown corrections of -3.00 to +1.50 D of sphericity and up to 1.5 D of cylinder are attainable with LIRIC. Such adjustments can be applied in a multifocal diffractive pattern as an additional surgical option for presbyopic patients.²⁹

Conclusions

Presbyopia continues to be an important hurdle in eye care as we face an ever-aging population. Surgical approaches to these patients can be achieved through a variety of true accommodative and pseudoaccommodative approaches. The goal of presbyopic management is to improve quality of near and intermediate vision while maintaining adequate distance vision. New surgical therapies, including advancements in pseudoaccommodative and accommodative IOLs, scleral procedures, laser refractive index shaping, and LIRIC, among others, represent alternative surgical options to address the concerns of the presbyopic patient. ■

References

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Dr. Milliken is a Resident Physician at Storm Eye Institute, Medical University of South Carolina.

Dr. Mercer is a Cornea & Refractive Surgery Fellow at Storm Eye Institute, Medical University of South Carolina.

Dr. Rocha is Director of Cornea & Refractive Surgery, Fellowship Director of Cornea & Refractive Surgery, and Associate Professor of Ophthalmology at Storm Eye Institute, Medical University of South Carolina.

The authors have no relevant disclosures.