Experimental evaluation of ophthalmic devices and solutions using rabbit models

OBJECTIVE: To analyze and compare the geometry of the anterior segment of rabbit and human eyes, with relevance for the evaluation of intraocular lenses, and to review rabbit models used in our laboratory for the evaluation of different ophthalmic devices and solutions. PROCEDURES: Fifteen rabbit and 15 human eyes (10 phakic and 5 pseudophakic/group) obtained postmortem were used. Anterior-posterior length, equatorial diameter, and white-to-white (corneal diameter) were measured with calipers. The eyes were then analyzed with a very high-frequency ultrasound (Artemis, Ultralink) for measurements of the anterior chamber depth, and anterior chamber and ciliary sulcus diameters. The capsular bag diameter was measured with calipers from a posterior view, and the diameter and thickness of the crystalline lenses were measured after their excision from the phakic eyes. RESULTS: Although the size of the rabbit eye is overall smaller than the size of the human eye, the dimensions of the anterior segment of rabbit eyes are generally larger. The differences between rabbit and human eyes were statistically significant (Wilcoxon rank sum test) in terms of anterior-posterior length, equatorial diameter, white-to-white measurements (P < 0.0001), anterior chamber diameter (P = 0.0004), ciliary sulcus diameter (P = 0.0012), and crystalline lens diameter and thickness (P = 0.0003). CONCLUSIONS: Experimental evaluation of design features of new phakic intraocular lenses in rabbit eyes may be inconclusive without adaptation of their size/design, contrary to the evaluation of new pseudophakic lenses by implantation in the capsular bag. The rabbit is a very valuable model for the experimental evaluation of different ophthalmic devices and solutions.     

Vacuum Squeezing of Solids: Macroscopic Quantum States Driven by Light Pulses

Femtosecond laser pulses and coherent two-phonon Raman scattering were used to excite KTaO3 into a squeezed state, nearly periodic in time, in which the variance of the atomic displacements dips below the standard quantum limit for half of a cycle. This nonclassical state involves a continuum of transverse acoustic modes that leads to oscillations in the refractive index associated with the frequency of a van Hove singularity in the phonon density of states.     

Application of Two-Level Full Factorial Design for the Extraction of Fucoxanthin and Antioxidant Activities from Sargassum siliquosum and Sargassum polycystum

Two-level full factorial design was employed to identify the extraction parameters that can improve the derivation of fucoxanthin content (FC), total carotenoid content (TCC), and antioxidant from two brown seaweeds, Sargassum siliquosum (SS) and Sargassum polycystum (SP). These parameters included temperature (A: 4–45°C), time (B: 30–1,440 min), and solvent-to-solid ratio (C: 10–50 ml/g). Antioxidant activities were determined as trolox equivalent antioxidant capacity (TEAC), 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity, and ferric-reducing antioxidant power (FRAP). Results showed that all three factors were significant (p < 0.05) in providing higher FC in both species. These factors were also significant in obtaining higher TCC in SS; whereas in SP, TCC was only affected by solvent-to-solid ratio. Only temperature was found to contribute significantly to a higher TEAC in both species. However, none of the factors improved DPPH for SS, except temperature and time for SP. For SS, only time was significant in obtaining higher FRAP; whereas temperature and time were significant for SP. Hence, results indicate that a simple modification in the extraction temperature, time, and solvent-to-solid ratio will be able to improve the derivation of fucoxanthin, carotenoids, and antioxidant activities.