Comparison of the optical behaviour of five different multifocal diffractive intraocular lenses in a model eye.

The purpose of this study was to investigate and compare the optical performance of five trifocal intraocular lenses (IOLs) following the ISO 11979-2 standards, analysing the impact of tilt and decentration. Five different diffractive trifocal IOLs were evaluated in this experimental study: Acriva Trinova (VSY-Biotechnology) (AT), FineVision HP (PhysIOL) (FVHP), AT LISA tri 839 MP (Zeiss) (ATLT), PanOptix TFNT00 IOL (Alcon) (PO), and Tecnis Synergy (J&J Vision) (TS). In-vitro optical quality analysis of them was performed with the Lambda PMTF system that has an aberration neutral cornea model (Lambda-X Ophthalmics). Measurements were performed on-axis, with 5º of IOL tilt and with 0.5 mm of IOL decentration using 543-nm monochromatic light. Finally, IOL dimensions and diffractive disk profile inspection was performed using the VisIOLA system (Rotlex). On-axis measurements showed a far through-focus MTF > 0.3 at 3 mm aperture, except for TS. FVHP and PO showed better far MTFs for larger apertures (3.75 mm and 4.5 mm) while AT showed good intermediate and near vision for such apertures. With 5º of IOL tilt, the better optical performance at all distances was found with AT for medium-sized pupils (3 mm) and an important reduction of MTF was found for ATLT and PO, especially in the intermediate focus. The induction of 0.5 mm of IOL decentration especially affected the intermediate focus of ATLT and TS and the far focus of FVHP and PO. IOL dimensions and diffractive profile were consistent with those described by the manufacturer. In conclusion, there are differences in the optical performance according to the pupil aperture of the five trifocal IOLs evaluated and this should be considered in clinical practice when selecting the most appropriate implant in each specific case. IOL tilt and decentration can affect significantly in most of the designs evaluated the performance of the IOL at intermediate vision range. It should be noted that measurements were made with an aberration-free cornea, being necessary future studies analysing the impact of different levels of corneal aberrations.

Effect of Heat Level and Expose Time on Denaturation of Collagen Tissues.

INTRODUCTION: The applied heat level and expose time are main issues in certain operations/applications, such as a laser assisted tissue welding, preparation of collagen-based biomaterials (films, implants). Therefore, the precise investigation of these parameters is crucial. The results can serve as a guideline to assess potential effects while maintaining the functionality of the collagen structures. METHODS: Collagen tissues from rat-tail tendon, calfskin, and bones are soaked in buffer solutions, then examined by microscope at different temperature levels. RESULTS: Increase in temperature reduced the microscopically observed collagen crimp contrast for calfskin and rat-tail tendons but not for bone tissues. The contrast level for rat tail tendon decreased down to 80% of its initial value at 37, 157, and 266 s for 70, 65, and 60 °C, respectively. The decrease in the crimp contrast was about only 25% and 2% at 55 and 50 °C after 2 h, respectively. 50% drop in contrast level was occurred for the skin samples at 16, 90, 110 and 1900 s for 70, 65, and 60 °C, respectively. The bone samples, did not show any significant differences in contrast levels. CONCLUSION: The observed denaturation behaviours are in line with Arrhenius Law. This study could be expanded on to other types of tissues at wider temperature ranges to make a guideline for biological/medical processes that radiate heat in order to assess their side effects on collagen and other proteins.