Toward New Engagement Paradigms For Intraocular Lenses: Light-Initiated Bonding of Capsular Bag to Lens Materials

Abstract

PURPOSE. Successful intraocular lens procedures, that is, implantation of accommodating intraocular lenses (A-IOL), require firm engagement of the IOL haptics to the capsular bag. We evaluated the use of photochemical bonding to engage IOL materials to the capsular bag.METHODS. Freshly enucleated eyes of New Zealand rabbits were used in two types of photobonding experiments using Rose Bengal (RB) photoinitiation and green light (532-nm) irradiation. First, RB-stained capsular bag strips were photobonded ex vivo to IOL polymer [poly(2-hydroxyethyl methacrylate) pHEMA] strips in an atmosphere of air and of nitrogen. Second, IOLs were implanted intracapsularly and photobonded intraocularly. Irradiation times were between 30 and 180 seconds, and laser irradiance was between 0.25 and 0.65 W/cm 2 . The strength of the bonding was tested using a custom-developed uniaxial extensiometry system and the breakage load (the load that caused breakage per bonded area) was calculated.RESULTS. The breakage load of ex vivo capsule-pHEMA bonds increased exponentially with irradiation time, using 0.45 W/cm 2 . In air, the average breakage load across all conditions was 1 g/mm 2 and 1.6 times lower than that in a nitrogen atmosphere. Intraocularly, RB-stained IOLs were strongly photobonded to the capsule bag with breakage loads > 0.8 g/mm 2 .CONCLUSIONS. Breakage of the photobonded linkage between IOL material and capsular bag required loads substantially greater than the maximum force of ciliary muscle, suggesting that this technology may introduce a new paradigm for engagement of A-IOLs. The bonding produced in air was stronger than that in nitrogen atmosphere, suggesting that oxygen is involved in the chemical mechanism for photobonding.

Biomechanical Changes After In Vivo Collagen Cross-Linking With Rose Bengal–Green Light and Riboflavin-UVA

“…11,12 The photochemical process initiated by RGX had previously been used to create covalent bonds between collagen molecules on two different surfaces for attaching a bandage to the corneal surface, 13 to sealing skin wounds, 14 and photobonding an intraocular lens to the interior of the lens capsule. 15 The effect of RGX on the corneal biomechanics has been demonstrated by strip extensiometry, 11,12 by Brillouin microscopy 16 and in whole-eye globes by air puff deformation measurements and inverse mechanical modeling. 6 The corneal stiffening produced by RGX occurs closer to the anterior surface than stiffening by UVX because penetration of RB into the stroma is limited by its strong association with collagen.…”

Corneal Biomechanical Response Following Collagen Cross-Linking With Rose Bengal–Green Light and Riboflavin-UVA

“…A photochemical procedure using rose bengal and green light has also been used to replace sutures, 10 for photobonding amniotic membrane to the corneal surface as a form of photoactivated bandage, 11 and more recently for photobonding capsular bag tissue to polymers in intraocular lens implant applications. 12 Similar to these applications that involve intercollagen covalent bond formation across two different tissues, the rose bengal (RB)-green light CXL creates bonds in the stromal collagen fibrils, therefore stiffening the cornea, as shown for standard riboflavin UVA CXL. Both tensile uniaxial extensiometry and Brillouin microscopy revealed stiffening of corneal tissue in rabbit eyes treated ex vivo.…”

Intraocular Photobonding to Enable Accommodating Intraocular Lens Function

“…Our study of pHEMA-capsular bag bonding ex situ showed that bonding forces persist unchanged for at least 2 years (duration of the experiment) in immersion long term. 8 …”

“…The illumination source was a pumped all-solid-state device with 532 nm central wavelength (CNI Tech, Co., LTD, China), which was part of an illumination setup used in earlier studies for cross-linking and ex-situ photobonding. 8 , 9 The collimating system was bypassed and the fiber tip connected to a 1 mm diameter fiberoptic poly(methyl methacrylate) (PMMA) probe, suitable for insertion through a corneal incision. The experiments were performed at 0.8 and 1.6 W/cm 2 irradiance for 2.5 and 7 minutes.…”

“…In a previous study we demonstrated RB/green light mediated photobonding (RBPh) of IOL polymer to the crystalline lens capsular bag tissue ex situ. 8 In the former study, strips of New Zealand rabbits were bonded to strips of poly(2-hydroxyethyl methacrylate; pHEMA), using green (532 nm) laser irradiances between 0.25 and 0.65 W/cm 2 . The strength of the bonding was tested using uniaxial extensiometry.…”