Over 15 million people around the world are affected by cataract blindness. The intraocular lens market now exceeds $2.5 billion, with more than ten million cataract surgeries performed annually. According to Dr. Adrian Raiche, humanitarian requirements and economic pressures provide the enormous potential for products that establish market segments.

One in five people over 65 who suffer from cataract-related vision loss in some way. The US Census Bureau predicts that between the years 2000 and 2030, the proportion of people 65 and older will rise from 13% to 20% in the United States alone.

Presbyopia Drugs Development Market, or age-related loss of near vision, and emmetropia, or loss of the inherent ability to focus light, are two additional types of vision deterioration that occur far more frequently but are less severe in scope. Presbyopia is currently a natural part of getting older. Loss begins around the age of 30 and decreases to less than two dioptres for adults over 60 from an initial accommodation ability of 18 dioptres.

The general classification of specific disease states is ametropia, which is the most prevalent disease: hyperopia and nearsightedness, also known as myopia, A little more than 35% of people have myopia.
Ametropia and cataracts can be treated with excellent treatments. For surgical replacement of the cataractous lens, artificial intraocular lenses (IOLs) made of silicones and acrylics have been in use for decades and have excellent safety records. Multi-focal contact lenses or prescription glasses are the most recent and cutting-edge treatments for presbyopia. Optics, contact lenses, radial keratotomy, laser assisted in situ keratomileusis (LASIK), anterior chamber implantable lenses, and, more recently, orthokeratology are all excellent options for vision correction.

The new product profile is a single therapeutic device that easily restores the ability to focus close and far, corrects ametropia, and replaces the cataractous lens. A truly innovative product, such as a variable-power IOL, has the potential to establish an elective market for non-cataract patients given the certainty of presbyopia and the high prevalence of myopia.

ANATOMY, PHYSIOLOGY, AND ETIOLOGY The human eye is a remarkable organ that focuses light onto the retina, or more specifically the macula, using two primary elements—the cornea and lens—for precise vision. 75% of the eye's total 60 diopter focusing power is provided by the convex outer surface of the cornea, the first focusing element, and the large difference in refractive index between air (1.0) and corneal tissue (1.4).

The second component of the human crystalline lens is a structure that is bi-convex and is housed in a membraneous capsular bag. It is suspended by ligamentous zonules that are attached to an annular ciliary muscle. Even though the lens only accounts for 25% of the focusing power, its primary function is to provide variable power, making it possible to focus divergent light that is reflected from objects close by. An invagination of the ectoderm yields the crystalline lens, which is made up of three distinct structures.

The lens's nucleus is formed inside the posterior part of the invagination by the inner cell layer, and lamellar structures surround the nucleus are formed inside the anterior cell layer. Crystallins are three types of proteins that are produced by the cells that make up the lamellar structure.

People spend a lot more time looking at distant objects than near ones. It is detrimental to energy to require near-constant muscle action to maintain focused vision. The passive action of the zonular fibers pulling on the lens edge and stretching it flatter is the driving force behind the decrease in power or lens flattening. The zonules relax, the distance between the muscle and the lens decreases, and the lens expands to a more curved shape when the ciliary muscle contracts.

Denaturation of crystalline proteins or delamination of the lamella from the nucleus are the causes of cataract and can be attributed to: a deficiency in hydration, proliferative disorder, electromagnetic radiation, including visible and ultraviolet light, and infectious and genetic diseases.

Lamellar lens cell proliferation continues to be the cause of presbyopia. The lens will become larger, denser, and less flexible as a result. The increased diameter of the lens reduces the capacity of zonules of constant length to tighten and flatten the lens because the more rigid lens does not contribute its spring force.

MATERIAL CONSIDERATIONS Variable-power intraocular lenses (IOLs) share some of the same material properties as conventional IOLs. The refractive index ranks highest among these. Historically, lens replacement surgery has been traumatic. However, the diseased lens can now be removed using a 25-gauge, 0.5-millimeter-diameter cannula thanks to recent advancements in instruments like the TSV-25 system from Bausch & Lomb. Sutures are not necessary because this hole is sufficiently small.

Even though lens removal can be done with a very small incision, current IOL implantation requires a cut of 2–3 millimeters. The total volume of the IOL and the volume of the IOL required to provide focusing are both related to the material's refractive index.

Materials with a higher refractive index can be used to make IOLs with smaller volumes that are more convergent. The material's refractive index is also a property of its components that adds up. Water's compatibility with the natural environment enhances the effectiveness of materials with a higher refractive index because they contain more water.

The optical element and haptics of an IOL can range in diameter from 4.5 mm to 9 mm. IOLs come in a variety of shapes and sizes. The lens is folded or compressed and pushed through a tiny hole to squeeze the IOL through a 2–3 mm incision.
To withstand general forces greater than 600 g and significantly greater local shear forces, materials must have some flexibility and toughness. IOLs that change shape must also withstand more than 100,000 cycles of repeated bending.

Once implanted, materials must also coexist harmoniously with the body. Tissue response is difficult because the capsular bag is poorly perfused. The IOL's calcification is the greatest passive obstacle. Endogenous molecules like proteins and phospholipids can be adopted by contaminants or surface chemistries. The IOL can become opaque when free phosphorous from phospholipids forms a complex with calcium and precipitates as calcium phosphate.

Opacity can also result from the proliferation of lens epithelial cells across the IOL's surface after surgery. To stop posterior capsule opacification (PCO), treatments like mechanical boundaries, sharp edges, and collagen coatings have been used.

Compatibility with other surgical techniques is a final consideration. One aspect of ongoing eye disease for many is cataract. Silicone oil is frequently used to reseat the retina in cases of other conditions like retinal detachment. Components of the silicone oil with low molecular weights may adsorb to the IOL's surface, causing an additional issue.

VARIABLE-FOCUSING IOLS Creating a static lens with a variety of focal lengths is one relatively straightforward method for providing both near and far vision. Multi-focal IOLs, like bi-focal contact lenses, converge reflected light from the same object in multiple locations using various components of the same optic. The most focused image is selected by brain processing. Alcon's Acrysof ReSTOR and Advanced Medical Optics (AMO) ReZoom are two examples of such lenses.

ReSTOR is a brand-new lens made of conventional materials that is quickly gaining popularity. Similar to previous IOLs, it is simple to install, which is advantageous. However, contrast is diminished when the light is divided into multiple images, some of which are out of focus. Additionally, this approach is unlikely to result in lens replacement for non-cataract eyes due to other similar multi-focal strategies like multifocal contact lenses, monovision, which uses contact lenses to correct one eye for distance vision and one eye for near vision, and multi-focal LASIK.

The Eyeonics Crystalens is the first accommodating IOL to be approved by the FDA. Instead of the usual thin wire or narrow plate haptics, the Crystalens has two large, hinged, plate-like haptics. The Crystalens moves the lens forward by making use of the pressure difference caused by the ciliary muscle contracting. As is the case with reflections from close objects, this provides a longer path to the retina, allowing for the focusing of light with greater diversity.

The Crystalens were initially touted as having accommodation of up to 1 diopter. However, 0.5 diopters of accommodation are the focus of several reports. Post-market studies also indicate that the lens arching may alter the optic's power, enhancing the clinical outcome.

Human Optics, a German company, has created yet another design for a single lens. There are four large plate-type haptics in the 1CU lens. On the other hand, the purpose of these haptics is to fill the capsular bag. Contraction of the ciliary muscles influences the haptics, propelling the lens forward and facilitating the convergence of near-reflected light. The accommodation target for humans is currently being tested, and it is approximately 2 diopters.
Dr. Mona Sarfarazi was the first to patent a method for generating a change in the power of an optical system when two optics moved in different directions. The idea is similar to that of the telescope and other compound lens systems. The bag is flattened by zonule tension. The IOL is subjected to a force that is perpendicular to the optics.

The two optics are pushed together, reducing power, by an orthogonal force exerted on the capsular bag's anterior and posterior faces. The two lenses separate when the ciliary muscle contracts. Dr. Sarfarazi is working with Bausch & Lomb, and Visiogen is using a similar design. This lens system's target accommodation is 5 diopters. Both are currently undergoing clinical trials or human testing.

The natural lens adjusts by changing its curvature, whereas the two-lens systems are more like the natural lens in that they combine zonule tension and spring action. Several strategies are being evaluated.

Using the empty capsular bag as a form or inserting a flexible bag within the capsular bag to hold various injectable liquids is one strategy. In Australia, Jean-Marie Parel and the CSIRO tested cutting-edge materials. Materials like hydrogels and injectable branched silicones have been discussed. How to seal the injected material in and produce sufficient optics in situ are two issues that have arisen.

Dr. Joshua Ben- Nun came up with a solution that combines fluid-filled bags and displacement-driven IOLs. After surgery, the capsular bag in his design is allowed to collapse, forming a diaphragm. In front of the collapsed capsular bag is the accommodating IOL.

A liquid-filled optic presses against an orifice when ciliary muscle contraction exerts pressure on the lens. The lenticle-shaped arched portion of the fluid optic significantly boosts focusing power. Human trials of this strategy are currently underway as well.

THE NEXT STEP Ophthalmology has made significant progress in understanding the eye's function and disease, given that it was once thought that light came from the eyes. New medical imaging techniques have recently provided definitive proof of the mechanism of accommodation, which adds to this.

It is clear that ametropia, presbyopia, and cataract need to be solved simultaneously. However, it is not clear if current test technologies will be able to reach a tipping point in the adoption and implementation of accommodating IOLs or if these will feed critical learning for a transcendent device.