Rayacryl®

Injectable IOL Biomaterial

All Rayner injectable lenses are manufactured from Rayacryl®, Rayner’s own proprietary hydrophilic acrylic co-polymer of 2-hydroxy ethyl methacrylate (HEMA) and methyl methacrylate (MMA) with ethylene glycol dimethacrylate (EGDMA) as cross-linking agent.

Why hydrophilic acrylic?

Currently available foldable or injectable IOL biomaterials include hydrophilic acrylics, hydrophobic acrylics and silicones. The selection criteria for an IOL biomaterial depend upon:

• The effect on the blood aqueous barrier
• The cellular reaction on the anterior surface of the lens
• The effect of the IOL biomaterial on the lens capsule in terms of lenticular epithelial cell (LEC) proliferation and metaplasia leading to anterior and posterior capsular opacification.

Rayacryl®, being a hydrophilic acrylic, consistently outperforms all other biomaterials in terms of the above criteria.

Disadvantages of IOLs manufactured from alternative IOL biomaterials:

Hydrophobic acrylics

• Less biocompatible compared with hydrophilic acrylics
• Tendency to bioadhesiveness – more difficult to perform Nd:YAG capsulotomies
• Greater propensity to Nd:YAG laser damage
• Can be optically impure with vacuoles and “glistenings”
• Higher refractive index leading to higher incidence of dysphotopsia
• Thermolabile.

Silicones

• Less biocompatible compared with acrylic biomaterials
• Greater stimulation of cellular proliferation and Soemmering’s Ring formation
• Increased incidence of PCO
• Prone to anterior cell fibrosis & resultant opacification especially with plate haptics
• Increased risk of capsular phimosis
• Can develop signs of optical translucency
• Slippery when wet
• Uncontrolled unfolding characteristics.

Ultraviolet radiation protection

Unlike some IOL biomaterials, which incorporate an ultra violet absorbing agent with the potential to leach into the eye, Rayacryl® utilises a benzophenone ultra violet absorbing agent (2-hydroxy-4-acryloxyethoxy benzophenone [AEHB]), which is chemically bound within the co-polymer matrix. This agent has the most efficient UV absorbance characteristics between 220nm and 360nm with excellent light transmittance at 410nm and above.

Physical properties of Rayacryl®

• Water Content – 26%
• Young’s Modulus – 46.02 kg/cm²
• Tensile Strength – 56.86 kg/cm²
• Elongation to Break – 279%
• Extractable monomers – 0%
• Density – 1.18g/cm²
• Contact Angle – 29°
• Refractive Index (RI) – 1.46

Major benefits of Rayacryl®

Exceptionally high biocompatibility:

• Low rate of proliferation of anterior lenticular epithelial cells (LECs) contributing to low rates of PCO
• No significant fibrotic proliferation leading to such unwanted complications as cicitrization-induced decentration or capsular phimosis
• Reduced incidence of unwanted inflammatory response, coupled with a low rate of cellular proliferation, make IOLs manufactured from Rayacryl® safe for patients having a co-existing ocular pathology, including uveitic and diabetic patients
• Excellent capsular and uveal biocompatibility making IOLs manufactured from Rayacryl® ideal in combined phaco-trabeculectomies.

Additionally, IOLs manufactured from Rayacryl® have many other benefits

Non bioadhesive:

• Do not adhere to the posterior capsule
• Do not rely on bioadhesion for reduction of PCO.

User friendly:

• Optimum value for Young’s modulus gives easy and controlled unfolding
• Not thermolabile – does not require warming for easy unfolding
• Optimum water content within the co-polymer matrix ensures effective dissipation of heat during laser capsulotomies – high resistance to Nd:YAG damage.

Low affinity for Silicone Oil

In modern ophthalmic practice, when vitreoretinal surgery using Silicone Oil is anticipated, IOLs manufactured from hydrophobic acrylics or silicones, are contra-indicated because Silicone Oil can adhere irreversibly to hydrophobic lens optics (Silicone Oil Induced Opacification). The patient’s vision is affected and there is subsequent impairment to the surgeon’s view of the retina.

An essential feature of the hydrophilic Rayacryl® biomaterial is its very low affinity for Silicone Oil. Such opacification of an IOL is avoided when it is made from Rayacryl®.

Professor David Apple and his group compared various IOL biomaterials in terms of Silicone Oil adherence. Rayacryl® exhibited a lower affinity for Silicone Oil compared with hydrophobic acrylic, PMMA, Heparin Surface Modified PMMA, silicone elastomer and even the natural crystalline lens.

The results can be seen in the chart on the right >>