Background: Polymer materials based on hydrogel and silicone-hydrogel materials are commonly used in ophthalmology. It is important to research the structure of these materials, mainly the prevalence of free volumes.
Objectives: The study has been conducted in order to determine the presence of free volume gaps in the structure of polymer hydrogel and silicone-hydrogel contact lenses. In addition, to demonstrate differences in the occurrence of free volumes between types of represented contact lenses.
Material And Methods: Three different hydrogel and three different silicone-hydrogel polymer contact lenses were used as research material. The study was done by means of positron annihilation lifetime spectroscopy (PALS).
Results: As a result of the performed measurements, a graphical curve resulted which describes the relationship between the number of the annihilation acts in the time function. The study revealed the existence of three τ1, τ2 and τ3 components. Significant changes were observed in the ortho-positronium long life component τ3 and their intensities between the examined polymer contact lenses.
Conclusions: The conducted study using the Tao-Eldrup model indicates the presence of free volume holes in all research materials. The results lead to the following connection: contact lenses of higher oxygen permeability coefficient (silicone-hydrogel contact lenses) have more and larger free volumes than contact lenses of less oxygen permeability coefficient (hydrogel contact lenses).
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Ophthalmic Physiol Opt
January 2025
Elite School of Optometry, Medical Research Foundation, Chennai, India.
Purpose: To investigate changes in fluid reservoir turbidity parameters over time and its influence on visual performance in eyes with ocular surface disorders (OSD) wearing scleral contact lenses (SL).
Methods: Thirteen eyes with OSD were assessed for corrected distance visual acuity, contrast sensitivity (CS) and fluid reservoir turbidity using anterior segment optical coherence tomography at baseline, after 5 min and 0.5, 1, 2, 3 and 4 h of SL wear on day 1 and after 1 month.
Retina
October 2024
Department of Ophthalmology, the First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan, China.
Purpose: The research investigates the efficacy of hydroxypropyl methylcellulose (HPMC) treatment in facilitating the development of compact water droplets on the rear surface of synthetic lenses with capsule imperfections during the process of fluid-air exchange.
Method: This study examined four patients with intraocular lens (IOL) implants and posterior capsule defects who experienced the formation of dense water droplets on the posterior surface following fluid-air exchange. When this occurrence obstructs fundus visualization during surgery, it is recommended to suspend the surgical procedure.
Curr Drug Deliv
January 2025
Department of Pharmaceutics, Y. B. Chavan College of Pharmacy, Aurangabad, India.
Pharmaceutical giants (e.g., Ashland, Bausch & Lomb, Johnson & Johnson, Medtronic, Neurelis, etc.
View Article and Find Full Text PDFCureus
January 2025
Trauma and Orthopaedics, Oxford University Hospitals NHS Foundation Trust, Oxford, GBR.
This systematic review evaluates the long-term effectiveness of scleral lenses in improving visual outcomes, patient satisfaction, and safety in patients with keratoconus. A systematic search of six databases (PubMed, Embase, Web of Science, Scopus, Cochrane Library, and MEDLINE) was performed following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The inclusion criteria included studies with more than or equal to three months of follow-up, included a minimum of 20 keratoconus patients, published after year 2020 and outcomes reporting visual acuity, comfort or quality of life.
View Article and Find Full Text PDFInt Ophthalmol
January 2025
Discipline of Optometry, School of Health Sciences, University of KwaZulu-Natal, Durban, South Africa.
Purpose: To determine the prevalence and demographic profile of keratoconus (KC) among high school students in Nairobi County, Kenya.
Methods: In this population-based, prospective, cross-sectional study, multistage cluster sampling was used to select the participants. All students underwent visual acuity measurement, auto-refraction, retinoscopy and corneal topography.
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