In the past few years, accommodating IOLs (AccIOLs) have progressed through design, validation, and human trials with variable results. Ophthalmologists worldwide are eagerly awaiting regulatory approval of an AccIOL that provides substantial amplitude and range of accommodation. As surgeons, we must reexamine the fundamentals of visual accommodation to better distinguish scientific fact from marketing hype. There are 3 fundamental factors that allow for a functional change in lens power in a pre-presbyopic lens: 

1. The gradient elastic index of the capsule vs the nucleus;
2. The insertion of zonular fibers anterior to the lens equator; and 
3. The nonlinear dioptric power change of the lens surface.

Let’s take a closer look at each of these factors.

Gradient Elastic Index

In the pediatric lens, the capsule is 2,000 times stiffer (ie, a greater Young’s modulus of elasticity) than the cortex and the nucleus.¹ The compression of the capsule against the soft nucleus results in the lens forming a spheroid. With the reduction of zonular tension during ciliary body contraction, the pediatric lens naturally moves to a more spherical shape, increasing the dioptric power. Indeed, the natural state of the pediatric lens is to be accommodated. The lens is pulled into disaccommodation by tension on the zonules increasing with ciliary body relaxation and expansion. With aging, the lens nucleus becomes progressively stiffer, and the difference in the elastic modulus between the capsule and the nucleus is reduced. As a result, the effect of zonular tension on the lens capsule becomes less effective in changing the shape of the lens. 

Selective Zonular Force

Anatomic studies have clearly demonstrated that a substantial proportion of zonular fibers insert on the anterior lens capsule (Figure 1) and that the anterior zonular fibers selectively alter the shape of the anterior lens.² There is a relative paucity of zonules inserting onto the lens capsule at the equator. The change in curvature of the anterior surface is where dioptric power change in the lens occurs during accommodation.³ 

Nonlinear Dioptric Power Change

The anterior capsule of the lens in the disaccommodated state is relatively flat. When a flat lens surface is steepened even a small amount, a relatively large dioptric power change is created. This change in anterior lens shape is accomplished via a very small increase or decrease in the diameter based on zonular tension. In a relatively steeply curved lens, a significantly greater amount of steepening is required to obtain the same dioptric change compared to a lens with a flatter initial curvature. The human anterior lens capsule is relatively flat, allowing for significant accommodation with minimal shape change. The posterior curvature of the lens is relatively steep, accounting for the majority of the nonchanging overall lens power. 

Producing Accommodation

If we apply the above 3 principles to an AccIOL design, we see that the new IOL should have a flexible anterior accommodating optic that is relatively flat. Insertion of haptic actuators anterior to the equator can cause several diopters of power change if the external structure of the IOL is stiffer than the center of the IOL. The majority of the fixed IOL power should reside in a posterior optic surface.

How much accommodation should an AccIOL produce to provide a full range of functional vision? Current diffractive multifocal IOLs have a fixed 2-3 D of power in the reading segment of the IOL. The visual system of a child typically holds one-half of the available accommodative amplitude in reserve for prolonged near vision tasks.⁴ Thus, for an AccIOL to produce 3 D of prolonged reading ability, it is very likely that there must be the potential to produce a peak accommodation of 6 D. Most children have a small hyperopic refractive error that is generally absorbed by a subtle amount of resting accommodative tension (latent hyperopia). Therefore, we should add an additional 1 D of accommodative power potential to an AccIOL to mimic the pediatric lens. A full 7 D of accommodative range cannot be created by mobile optics within the human lens capsule. Instead, the principles described above must be applied to AccIOL design. 

Development of the JelliSee IOL

The JelliSee AccIOL (Figure 2) was developed by Forrest “Jim” Ellis, MD, a pediatric ophthalmologist. Dr. Ellis completed his pediatric and strabismus fellowship with David Guyton, MD, and David Hunter, MD, PhD, resulting in a career-long interest in applied optics. He observed the principles of accommodation in the pediatric lens and designed an IOL that would closely mimic the action and principles of the youthful pediatric lens. The JelliSee IOL features a silicone capsule filled with silicone oil. The chemical structure of the capsule and oil have been modified to create a stable and optically clear IOL. The anterior component of the IOL is a relatively flat, but flexible, lens. Eight haptic actuators are arranged circumferentially around the lens and insert anteriorly to the equator, creating surface power changes of the anterior optic surface during accommodation. The overall power of the IOL is determined by the posterior optic. A full range of IOL power, including toric correction, can be placed in the posterior optic.

Implantation

Implantation of the JelliSee IOL is substantially similar to modern cataract surgery. The injector is designed to fit through a 3.0-mm to 3.2-mm corneal incision. The JelliSee IOL is injected into the capsule much like a standard IOL via an approximately 5.25-mm anterior capsulotomy. The haptic actuators reside within the equatorial region of the capsule. As the ciliary body contracts, the zonular tension is relaxed, and the JelliSee IOL automatically assumes an accommodated configuration. As the ciliary body relaxes and expands, zonular tension increases, and the JelliSee IOL is pulled into disaccommodation for good distance vision. The total required diameter change of the IOL (measuring from the peripheral edges of opposing actuators) is only 114 μm, which achieves 7 D of power change. There is minimal anterior-posterior translation of the 2 optics. The primary driver of dioptric power change is an increase in the anterior optic curvature from relatively flat to slightly steeper. Because the zonules must translate their tension to the haptic actuators, scarring of the capsule into the haptic actuators is a desired process. Although previous AccIOL designs have eventually been foiled by capsular scarring and contraction, the JelliSee IOL benefits from this natural process after cataract surgery. YAG-laser capsulotomy is possible with a standard technique for the JelliSee IOL. 

 Function

The JelliSee AccIOL was shown to function well with Zemax optical modeling, and the IOL was confirmed to function as designed with optical bench testing. The human ciliary body is known to produce 0.08 N of force well into the seventh or eighth decade of life.^5-7 With 0.08 N of radial force applied to the JelliSee, 7 D of lens power change was observed in optical bench testing. In a monkey model, the JelliSee IOL demonstrated 7 D of power change induced by pharmacologic accommodation up to 15 months after JelliSee implantation. Ten subjects in the first-in-human monocular trials received a JelliSee AccIOL, with the first case implanted in October 2022 (Figure 3). Follow-up at 6 and 12 months showed a strong accommodation signal, with many patients easily reading at ultranear distances of 20 cm through their full distance correction in trial frames. In the monocular defocus curve, we show the results of one of the first-in-human subjects, demonstrating a defocus curve mimicking that of a 10-year-old child (Figure 4). 

A more extensive human trial with some bilateral implantations is scheduled to begin in the first quarter of 2025 for the JelliSee AccIOL. If this study replicates the computer modeling, bench studies, animal studies, and first-in-human trial, then definitive studies aimed at FDA approval will be pursued. There have been many false starts in the past 2 decades with promising AccIOL designs. Now, this elusive technology may nearly be within our grasp. 

Yuri McKee, MD, is a board-certified ophthalmic surgeon with fellowship training in corneal and refractive surgery. He completed fellowship training in corneal disease, complex anterior-segment surgery, and refractive surgery at the Emory Eye Center in Atlanta. He practices cornea, cataract, and refractive surgery at East Valley Ophthalmology in Mesa, AZ.

References

1.Danysh BP, Duncan MK. The lens capsule. Exp Eye Res. 2009;88(2):151-164.

2. Nankivil D, Maceo Heilman B, Durkee H, et al. The zonules selectively alter the shape of the lens during accommodation based on the location of their anchorage points. Invest Ophthalmol Vis Sci. 2015;56(3):1751-1760.

3. Dubbelman M, Van der Heijde GL, Weeber HA. Change in shape of the aging human crystalline lens with accommodation. Vision Res. 2005;45(1):117-132.

4. Millodot M, Millodot S. Presbyopia correction and the accommodation in reserve. Ophthalmic Physiol Opt. 1989;9(2):126-132.

5. Hermans EA, Dubbelman M, van der Heijde GL, Heethaar RM. Change in the accommodative force on the lens of the human eye with age. Vision Res. 2008;48(1):119-126.

6. Hermans EA, Dubbelman M, van der Heijde GL, Heethaar RM. Estimating the external force acting on the human eye lens during accommodation by finite element modelling. Vision Res. 2006;46(21):3642-3650.

7. Fisher RF. The ciliary body in accommodation. Trans Ophthalmol Soc U K (1962). 1986;105(Pt 2):208-219.

Disclosure and Acknowledgements

Dr. McKee is chief science advisor for JelliSee Ophthalmics. He would like to recognize the excellent efforts of the core members of the JelliSee team. Dr. Jim Ellis is the inventor and founder of JelliSee. Dr. Ellis has worked tirelessly with the chief engineer, Nestor Farmiga, in the design and manufacture of the lens. Human trials were conducted at Clinica Quesada in San Salvador, El Salvador, under the supervision of Gabriel Quesada, MD, and Rodrigo Quesada, MD. Kevin Waltz, MD, and John Vukich, MD, are the medical directors for JelliSee. Dr. Vukich was the primary surgeon for the first-in-human trials. New to the team is co-chief science advisor, Julie Schallhorn, MD.