Modern artificial cataract lenses, called intraocular lenses or IOLs, are made primarily from synthetic polymers. The three main material families are hydrophobic acrylic, hydrophilic acrylic, and silicone, with an older rigid plastic called polymethyl methacrylate (PMMA) still in limited use. Hydrophobic acrylic has become the most widely implanted material worldwide, though each option brings distinct trade-offs in flexibility, optical clarity, and long-term behavior inside the eye.
How a Wartime Accident Led to the First Lens Material
The story of IOL materials begins during World War II. British ophthalmologist Harold Ridley noticed that when shards of cockpit canopy lodged in pilots’ eyes, the fragments sat there without triggering the severe inflammatory response that other foreign materials caused. The canopy material was Perspex, a form of PMMA. Drawing on that observation, Ridley performed the first successful IOL implantation in 1949, using a lens crafted from Perspex CQ.1PubMed Central. Sir Harold Ridley as the Pioneer of Intraocular Lenses: His Inspiration Drawn From World War II Pilots PMMA turned out to be remarkably stable inside the eye, and it remained the standard IOL material for decades.
PMMA’s physical properties help explain its longevity as a lens material. It behaves somewhat like glass at body temperature, with a glass transition temperature well above 100°C and a narrow range of surface properties that make it optically predictable.2Ophthalmologica. Material Properties of Various Intraocular Lenses in an Experimental Study The drawback is rigidity. A PMMA lens cannot be folded, so surgeons need to make a larger incision to place it in the eye. That bigger wound means more surgically induced astigmatism and slower healing. Once foldable materials arrived in the 1980s and 1990s, PMMA lenses gradually fell out of favor in high-resource settings, though they remain common in parts of the world where cost matters most.
The Three Foldable Material Families
Nearly all IOLs implanted today can be folded or rolled, allowing surgeons to slide them through an incision as small as about 2 millimeters. These foldable lenses belong to one of three material families, and the differences between them matter for how the lens performs over the decades it will spend inside your eye.
Hydrophobic Acrylic
Hydrophobic acrylic lenses repel water. They absorb less than about 5 percent of their weight in moisture, which gives them a relatively high refractive index and lets manufacturers make a thinner optic for the same focusing power.3Journal of the Mechanical Behavior of Biomedical Materials. Mechanical characterisation of hydrophobic and hydrophilic acrylates used in intraocular lenses through depth sensing indentation Their glass transition temperature sits near body temperature, which means the material is relatively stiff at room temperature but softens and becomes flexible once inside the warm eye.4PubMed Central. Physicochemical and surface properties of acrylic intraocular lenses and their clinical significance That property makes them unfold slowly and predictably after injection into the eye. Hydrophobic acrylics now account for the majority of IOL implantations in most countries.
Hydrophilic Acrylic
Hydrophilic acrylic lenses take the opposite approach, absorbing a substantial amount of water, typically between 18 and 34 percent of their weight. The base polymer often incorporates hydroxyethyl methacrylate (HEMA), the same material used in many soft contact lenses. The manufactured lens starts out dry and opaque; once placed in fluid, it hydrates, becomes soft, and turns optically clear. This high water content gives hydrophilic lenses good biocompatibility and tends to produce less glare. The trade-off is a lower refractive index, roughly 1.40 to 1.43 compared with about 1.55 for hydrophobic acrylics. That lower index means the lens optic must be thicker to achieve the same power, which can require a slightly wider incision.
Silicone
Silicone elastomer lenses were the first widely used foldable IOLs. They are highly flexible, unfold quickly after insertion, and have good optical clarity. Compared with acrylic IOLs, silicone lenses provoke a somewhat different immune response on their surface. One early randomized comparison found that silicone IOLs attracted significantly more small inflammatory cells than either PMMA or acrylic lenses, while the acrylic lens drew fewer giant cells than the other two.5PubMed. Biocompatibility of poly(methyl methacrylate), silicone, and AcrySof intraocular lenses: randomized comparison of the cellular reaction on the anterior lens surface Silicone IOLs are still implanted, but their market share has shrunk considerably because of a specific complication discussed below.
The Silicone Oil Problem
One issue unique to silicone lenses involves patients who need retinal surgery. Surgeons sometimes inject silicone oil into the back of the eye to hold a detached retina in place while it heals. If a silicone IOL is already there, the oil and the lens surface share a similar chemical structure, causing oil droplets to cling tenaciously to the lens.6PubMed. Irreversible silicone oil adhesion to silicone intraocular lenses. A clinicopathologic analysis Those droplets scatter light and obscure the surgeon’s view of the retina, potentially compromising both treatment and the patient’s long-term vision.
In vitro studies have confirmed that the adhesion occurs regardless of how long the lens was exposed, what type of silicone oil was used, or which specific silicone IOL model was tested.7Ophthalmic Surgery, Lasers and Imaging Retina. Interaction Between Silicone Oil and Silicone Intraocular Lenses: An In Vitro Study In some cases, the silicone oil can even slowly diffuse into the lens material itself.8PubMed Central. Removal of silicone oil droplets adhering to the posterior surface of an intraocular lens For this reason, patients considered at high risk for future retinal problems are typically steered toward an acrylic IOL instead. This consideration alone has been a major factor in the shift away from silicone as the default IOL material.
What the Support Arms Are Made Of
An IOL is not just an optic disc. It also has thin, springy arms called haptics that hold the lens centered inside the eye’s capsular bag. The haptic material matters because it determines how well the lens keeps its position over time. Common haptic materials include polypropylene, polyvinylidene fluoride (PVDF), and extruded PMMA. Testing has shown that PVDF haptics recover their original shape better than polypropylene or PMMA haptics after being compressed for weeks or months, which means they are less likely to let the lens drift off-center.9PubMed. Comparison of shape recovery ratios in various intraocular lens haptics
In some one-piece designs, the haptics are made from the same acrylic polymer as the optic, cut or molded as a single unit. In three-piece designs, the haptics are separate strands of a different polymer attached to the optic. When an IOL needs to be sutured or otherwise fixed to the wall of the eye rather than sitting inside the natural capsule, the haptic material and fixation technique become especially important. A recent ex-vivo comparison found that expanded polytetrafluoroethylene (ePTFE) sutures resisted dislocation forces far better than either flanged polypropylene or flanged PVDF haptic techniques.10Scientific Reports. Biomechanical performance of expanded polytetrafluorethylene sutures, flanged polyvinylidene fluoride and polypropylene in scleral IOL fixation
Surface Coatings and Light Filters
The bulk material is only part of the story. Manufacturers also modify the surface chemistry of IOLs to improve how the lens interacts with the eye’s tissues. Techniques include plasma treatment, ion beam bombardment, and the application of thin molecular layers like heparin or polyethylene glycol. These coatings can make a hydrophobic lens slightly more hydrophilic on its front surface while keeping the back surface water-repellent, or they can reduce protein and cell adhesion. Laboratory and animal studies have shown improved biocompatibility with these surface modifications.11PubMed Central. Surface Modification of Intraocular Lenses
Many modern IOLs also contain chromophores, chemical additives that filter specific wavelengths of light. All IOLs block ultraviolet light, but some also filter blue light in the short-wavelength visible range. The rationale is that high-energy blue light may contribute to retinal phototoxicity and possibly the progression of age-related macular degeneration. These blue-light-filtering IOLs have become increasingly popular, though systematic reviews of the evidence have found the case for protection against macular degeneration is still mostly theoretical.12Seminars in Ophthalmology. Blue light filtering ophthalmic lenses: A systematic review Some patients report a slight yellow tint with blue-filtering lenses, and critics argue that filtering blue light could subtly impair color perception or affect circadian rhythms.
Material-Specific Complications
No IOL material is free of long-term quirks. Two complications in particular are closely tied to material chemistry.
Glistenings in Hydrophobic Acrylic
Glistenings are tiny, fluid-filled microvacuoles that form within the body of a hydrophobic acrylic lens. They appear as sparkly points when a clinician shines a slit lamp through the optic. Laboratory studies can reproduce them by cycling the lens through temperature changes in water, which causes tiny pockets of aqueous fluid to become trapped inside the polymer matrix.13PubMed Central. Evaluation of in vitro glistening formation in hydrophobic acrylic intraocular lenses In most patients, glistenings are detectable on close examination but do not meaningfully affect vision. In a small number of cases, dense glistenings can scatter enough light to reduce contrast sensitivity. Manufacturers have reformulated their acrylic polymers over the years to reduce glistening rates, and newer-generation hydrophobic lenses show fewer of them than earlier models.
Calcification of Hydrophilic Acrylic
Hydrophilic acrylic lenses face a different material vulnerability: calcium phosphate deposits can form on or within the lens surface, turning it cloudy. This calcification can occur after certain secondary eye procedures, such as gas injection into the front or back of the eye. A clinical review identified 15 cases of IOL calcification, all in lenses with hydrophilic acrylic components.14PubMed. Calcification of hydrophilic acrylic intraocular lenses following secondary surgical procedures in the anterior and posterior segments Once calcification becomes visually significant, the only remedy is surgically exchanging the lens. This complication is uncommon, but it has prompted some surgeons to prefer hydrophobic acrylic lenses in patients who might need additional eye procedures down the road.
How Material Affects Clouding of the Capsule
After cataract surgery, cells from the lens capsule that was left in place can grow across the back surface of the IOL, creating a haze called posterior capsule opacification, or PCO. It is sometimes called a “secondary cataract,” though it is not actually a new cataract. Material choice has a substantial effect on how often this happens.
A meta-analysis comparing IOL materials found that acrylic lenses had dramatically lower rates of PCO and follow-up laser treatment than PMMA lenses, with a pooled difference of about 39 percentage points in PCO rates and 24 percentage points in capsulotomy rates favoring acrylic. Silicone lenses fell in between. Hydrogel (hydrophilic acrylic) lenses performed worst, with PCO rates more than 50 percentage points higher than hydrophobic acrylic lenses.15PubMed. Efficacy of different intraocular lens materials and optic edge designs in preventing posterior capsular opacification: a meta-analysis A more recent systematic review confirmed the superiority of hydrophobic acrylic over hydrophilic acrylic, finding nearly seven times the risk of needing laser capsulotomy with hydrophilic material.16The Indonesian Journal of General Medicine. The Comprehensive Systematic Review of Association of Posterior Capsular Opacification (PCO) to IOL Material and Design
Edge design matters too. A sharp posterior optic edge acts like a physical barrier, discouraging cells from migrating across the back of the lens. The same meta-analysis found that sharp-edged lenses outperformed rounded-edge designs across all material types.15PubMed. Efficacy of different intraocular lens materials and optic edge designs in preventing posterior capsular opacification: a meta-analysis So when surgeons choose an IOL today, they are weighing both the bulk material and the geometry of the optic edge, and the combination of hydrophobic acrylic with a sharp edge tends to offer the lowest risk of capsule clouding. However, sharp-edged designs can produce slightly more fibrotic change at the rim of the capsule opening, so the trade-off is not entirely one-sided.17PubMed. Effect of intraocular lens optic edge design and material on fibrotic capsule opacification and capsulorhexis contraction
How IOLs Are Manufactured
For rigid PMMA lenses, the main production methods are lathe cutting with diamond tools, compression molding, and injection molding. PMMA’s glass transition temperature is high enough that the material stays stiff at room temperature, making it straightforward to machine with high precision. After cutting, lenses go through a careful tumbling process that rounds and polishes the edges. Foldable acrylic and silicone lenses are typically cast-molded in precision molds, since their softer nature at room temperature makes traditional machining less practical. Regardless of the material, every lens undergoes rigorous inspection and sterilization before it reaches the operating room.
Lenses That Release Drugs or Change Shape
Researchers are pushing IOL materials beyond their traditional role as passive optical elements. One avenue is drug-eluting lenses. A hydrogel platform based on HEMA and MMA has been developed that can be loaded with both an antibiotic and an anti-inflammatory drug, releasing therapeutic concentrations of each for about three weeks after implantation.18PubMed. Optimization of intraocular lens hydrogels for dual drug release: Experimentation and modelling If this technology matures into clinical use, it could eliminate the need for the regimen of eye drops that patients currently use for weeks after cataract surgery.
Another frontier involves smart polymers and nanotechnology-enhanced biomaterials. Shape-memory polymers that change form in response to temperature or light are being explored for accommodating IOLs, lenses that could shift focus the way the eye’s natural lens does in younger people. Light-adjustable lenses already exist commercially: made from a specialized silicone embedded with photosensitive molecules, they allow surgeons to fine-tune the lens power after implantation by exposing the eye to specific wavelengths of ultraviolet light.19PubMed Central. Light-adjustable lens: development of in vitro nomograms Multifunctional biomaterials with photothermal and drug-release capabilities are also being investigated, particularly for traumatic cataracts where managing infection and inflammation is critical.20PubMed. Biomaterials in Relative Devices for Traumatic Cataract: Recent Advances and Future Perspectives The materials science of cataract lenses, in other words, is nowhere close to settled. The lens your surgeon offers you ten years from now may do things that today’s polymers simply cannot.