PRESBYOPIA STARTS for most people in their early to mid 40s, is associated with reduced quality of life (McDonnell et al, 2003), and seems to impact women more than men (Pointer, 1995). The primary reason for this gradual loss of accommodation is an age-related stiffening of the lens, leading to ineffective ciliary muscle contraction, which was used to cause a release in zonular tension at the lens equator to mold the elastic capsule (Glasser and Campbell, 1999).

Regaining lost accommodation is not an easy task. For context, for the crystalline lens to accommodate 5D in power, it would need to change its shape significantly—by more than 300µm in thickness and diameter (Glasser, 2008).

There are three main areas of research focusing on improving or regaining the ability to dynamically change focus between different distances: surgical procedures, pharmacological treatments, and accommodative contact lenses. While some of these are in early trial phases, others have been tested in clinical studies and show varying levels of success.

Surgical options have ranged from the exploration of lasers to make micro excisions in the sclera that increase the plasticity of the scleral tissue to other treatments targeting the crystalline lens itself (Swartz et al, 2014). However, of all the surgical approaches to restoring accommodation, the most widely used are accommodative intraocular lens (IOL) implants, including single-optic IOLs designed to undergo forward and backward translation, dual-optic IOLs that allow modifiable separation distance of the two optics, and IOLs that increase in curvature to produce an optical change in power (Glasser, 2008).

Pharmacological treatments are considered noninvasive, and one approach uses miotic agents to create a pinhole effect to increase the depth of focus, in addition to contraction of the ciliary muscle and thickening of the lens (Grzybowski et al, 2020). The stimulation of the uveal tract, however, can cause side effects such as chronic inflammation, posterior synechiae, and spasmodic contractions of the iris, as well as a myopic shift, and often requires nonsteroidal anti-inflammatory drugs to be used alongside miotic agents (Haghpanah and Alany, 2022).

Other pharmacological approaches have investigated crystalline lens softeners to increase lens elasticity and responsiveness to ciliary body contraction, but results from these investigations are still inconclusive (Grzybowski et al, 2020).

The allure of accommodating contact lenses is obvious. They could offer the convenience of use only when needed, modifiable to the changing needs of patients as presbyopia progresses. Researchers have developed liquid crystal contact lenses, with laboratory studies testing various prototypes applying electric power to switch the focus from distance to near in scleral-type lenses (Bailey et al, 2018; Bailey et al, 2022; Banerjee et al, 2023).

A patented device that is currently under investigation uses the eyelids to reshape or move a contact lens by either squeezing or lifting on the eye to increase the tear reservoir behind the lens by creating additional dioptric power (Win-Hall, 2011). While this invention uses a rigid GP material, another patent has investigated accommodative soft lenses (Waite et al, 2024). Multiple chambers within this contact lens theoretically would respond to eyelid pressure by transmitting fluid through channels into the optical chamber, which would increase in power to support near vision.

Considering the inevitability of presbyopia later in life, there is a lot of interest in cost-effective and safe solutions to restore seamless vision at all distances. It has yet to be determined which of these approaches will move forward to become the standard of care. In the meantime, single-vision and multifocal solutions with spectacles and contact lenses remain the most popular choice.

REFERENCES

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3. Glasser A, Campbell MC. Biometric, optical and physical changes in the isolated human crystalline lens with age in relation to presbyopia. Vision Res. 1999 Jun;39:1991-2015.

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8. Banerjee A, Ghosh C, Karkhanis MU, et al. Refractive-type varifocal liquid-crystal Fresnel lenses for smart contacts. Opt Express. 2023May 8;31:17027-17049.

9. Win-Hall DM. Accommodating or focusable contact lens. 2011; US7866815B2. Available at patents.google.com/patent/US7866815B2/en. Accessed 2024 May 21.

10. Waite SB, Gupta A, Schnell U. Accommodating soft contact lens. 2024; US11874531B2. Available at patents.google.com/patent/US11874531B2/en. Accessed 2024 May 21.