ABSTRACT
Intraocular lenses (IOLs) are commonly implanted after surgical removal of a cataractous lens. A variety of IOL materials are currently available, including collamer, hydrophobic acrylic, hydrophilic acrylic, PHEMA copolymer, polymethylmethacrylate (PMMA), and silicone. High-quality polymers with distinct physical and optical properties for IOL manufacturing and in line with the highest quality standards on the market have evolved to encompass medical needs. Each of them and their packaging show unique advantages and disadvantages. Here, we highlight the evolution of polymeric materials and mainly the current state of the art of the unique properties of some polymeric systems used for IOL design, identifying current limitations for future improvements. We investigate the characteristics of the next generation of IOL materials, which must satisfy biocompatibility requirements and have tuneable refractive index to create patient-specific eye power, preventing formation of posterior capsular opacification.
ABSTRACT
Adaptive optics (AO) is employed for the continuous measurement and correction of ocular aberrations. Human eye refractive errors (lower-order aberrations such as myopia and astigmatism) are corrected with contact lenses and excimer laser surgery. Under twilight vision conditions, when the pupil of the human eye dilates to 5-7 mm in diameter, higher-order aberrations affect the visual acuity. The combined use of wavefront (WF) technology and AO systems allows the pre-operative evaluation of refractive surgical procedures to compensate for the higher-order optical aberrations of the human eye, guiding the surgeon in choosing the procedure parameters. Here, we report a brief history of AO, starting from the description of the Shack-Hartmann method, which allowed the first in vivo measurement of the eye's wave aberration, the wavefront sensing technologies (WSTs), and their principles. Then, the limitations of the ocular wavefront ascribed to the IOL polymeric materials and design, as well as future perspectives on improving patient vision quality and meeting clinical requests, are described.
ABSTRACT
Dry eye disease (DED), a multifactorial disease of the tears and ocular system, causes loss of tear film homeostasis with damage to the ocular surface. This study aimed to assess whether a peculiar matrix based on sodium hyaluronate (HA), xanthan gum (XNT), glycine (GLY) and betaine (BET) as osmoprotectants, could be involved in biological responses. Wound healing assay on human corneal epithelial (HCE) cells in monolayer showed a synergistic effect of the combination of HA + XNT (**p ≤ 0.01) together with an efficient extracellular matrix remodeling of the formulation in SkinEthic™ HCE 3D-model sought by integrin beta-1 (ITGß1) expression and morphological analysis by hematoxylin and eosin (H&E), compared to a reference marketed product. The synergistic effect of HA + XNT + GLY + BET showed an antioxidant effect on HCE cells (***p ≤ 0.001). Real-time PCR analysis showed that the combination of GLY + BET seemed to ameliorate the effect exhibited by the single osmoprotectants in reducing tumor necrosis factor-alpha (TNFα, #p ≤ 0.05), interleukin-1 beta (IL1ß, ####p ≤ 0.0001) and cyclooxygenases-2 (COX2, ####p ≤ 0.0001) genes in SIRC cells under hyperosmotic stress. Furthermore, pretreatment with XNT, alone and in combination (##p ≤ 0.01), reduced COX2 expression in human non-small cell lung cancer cells (A549). Finally, the formulation was well-tolerated following q.i.d. ocular administration in rabbits during a 28-day study. Due to the synergistic effect of its components, the matrix proved able to repair the ocular surface restoring cell homeostasis and to protect the ocular surface from pro-inflammatory pathways activation and oxidative damage, thus behaving as a reactive oxygen species (ROS) scavenger.
