Physiologic Changes of Lens Transparency during Ageing: A Scheimpflug Photography Study

2015 ◽  
pp. 72-74 ◽  
Author(s):  
U. Eckerskorn ◽  
K. Kokkas ◽  
O. Hockwin ◽  
H. Laser ◽  
M. Janke
Keyword(s):  
Scheimpflug Photography ◽  
Lens Transparency

scholarly journals Evaluation of Pachymetric Measurements with Scheimpflug Photography-Based System and Optical Coherence Tomography Pachymetry at Different Stages of Keratoconus

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Betül İlkay Sezgin Akçay ◽  
Engin Bilge Özgürhan ◽  
Ercüment Bozkurt ◽  
Tuğba Kurt ◽  
Yusuf Yıldırım ◽  
...  
Keyword(s):  
Optical Coherence Tomography ◽  
Optical Coherence ◽  
Scheimpflug Photography

The aim of this study was to compare the central and peripheral pachymetric measurements determined with Sirius system and Visante OCT and evaluate the agreement between them at different stages of keratoconus. Measurements were not significantly different in all patients and subgroups and showed high correlation for the corneal thicknesses of the entire cornea in different stages of keratoconus.

scholarly journals Association between a Tetranucleotide Repeat Polymorphism of SPAG16 Gene and Cataract in Male Children

2013 ◽  
Vol 2013 ◽  
pp. 1-8
Author(s):  
Shipra Mehra ◽  
Suman Kapur ◽  
Suma Ganesh
Keyword(s):  
Gender Bias ◽  
Microsatellite Repeat ◽  
Tetranucleotide Repeat ◽  
Pediatric Cataract ◽  
Stem Loop ◽  
Stem Loop Structure ◽  
Lens Transparency ◽  
Secondary Structure Models ◽  
Disease Haplotype ◽  
Childhood Cataract

Purpose. Studies involving genotyping of STR markers at 2q34 have repeatedly found the region to host the disease haplotype for pediatric cataract. Present study investigated the association of D2S2944 marker, in sperm associated antigen 16 (SPAG16) gene and rs2289917 polymorphism, in γ-crystallin B gene, with childhood cataract. Methods. 97 pediatric cataract cases and 110 children with no ocular defects were examined for tetranucleotide repeat marker/SNP using PCR-SSLP/RFLP techniques. Polymorphisms were assessed for association using contingency tables and linkage disequilibrium among alleles of the markers was estimated. Energy-optimization program predicted the secondary structure models of repeats of D2S2944. Results. Seven alleles of D2S2944, with 9–15 “GATA” repeats, were observed. Frequency of the longer allele of D2S2944, ≥(GATA)13 repeats, was 0.73 in cases and 0.56 in controls (P=0.0123). Male children bearing ≥(GATA)13 repeats showed >3-fold higher risk for cataract (CI95% = 1.43–7.00, P=0.0043, Pc=0.0086) as compared to female children (OR=1.19, CI95% = 0.49–2.92, P=0.70). Cases with haplotype—≥(GATA)13 of D2S2944 and “C” allele rs2289917—have a higher risk for pediatric cataract (OR=2.952, CI95% = 1.595~5.463, P=0.000453). >(GATA)13 repeats formed energetically more favorable stem-loop structure. Conclusion. Intragenic microsatellite repeat expansion in SPAG16 gene increases predisposition to pediatric cataract by probably interfering posttranscriptional events and affecting the expression of adjacent lens transparency gene/s in a gender bias manner.

scholarly journals Biological glass: structural determinants of eye lens transparency

2011 ◽  
Vol 366 (1568) ◽  
pp. 1250-1264 ◽  
Author(s):  
Steven Bassnett ◽  
Yanrong Shi ◽  
Gijs F. J. M. Vrensen
Keyword(s):  
Refractive Index ◽  
Cellular Level ◽  
Structural Determinants ◽  
Lens Transparency ◽  
Index Matching ◽  
Lens Fibre ◽  
Refractive Index Matching ◽  
Lens Membranes ◽  
Adhesive Proteins ◽  
Structural Adaptations

The purpose of the lens is to project a sharply focused, undistorted image of the visual surround onto the neural retina. The first pre-requisite, therefore, is that the tissue should be transparent. Despite the presence of remarkably high levels of protein, the lens cytosol remains transparent as a result of short-range-order interactions between the proteins. At a cellular level, the programmed elimination of nuclei and other light-scattering organelles from cells located within the pupillary space contributes directly to tissue transparency. Scattering at the cell borders is minimized by the close apposition of lens fibre cells facilitated by a plethora of adhesive proteins, some expressed only in the lens. Similarly, refractive index matching between lens membranes and cytosol is believed to minimize scatter. Refractive index matching between the cytoplasm of adjacent cells is achieved through the formation of cellular fusions that allow the intermingling of proteins. Together, these structural adaptations serve to minimize light scatter and enable this living, cellular structure to function as ‘biological glass’.

scholarly journals Ultraviolet-sensitive vision in long-lived birds

2010 ◽  
Vol 278 (1702) ◽  
pp. 107-114 ◽  
Author(s):  
Livia S. Carvalho ◽  
Ben Knott ◽  
Mathew L. Berg ◽  
Andrew T. D. Bennett ◽  
David M. Hunt
Keyword(s):  
Uv Light ◽  
Bird Species ◽  
Visual Sensitivity ◽  
Opsin Gene ◽  
Uv Sensitivity ◽  
Long Period ◽  
Lens Transparency ◽  
Avian Order

Long-term exposure to ultraviolet (UV) light generates substantial damage, and in mammals, visual sensitivity to UV is restricted to short-lived diurnal rodents and certain marsupials. In humans, the cornea and lens absorb all UV-A and most of the terrestrial UV-B radiation, preventing the reactive and damaging shorter wavelengths from reaching the retina. This is not the case in certain species of long-lived diurnal birds, which possess UV-sensitive (UVS) visual pigments, maximally sensitive below 400 nm. The Order Psittaciformes contains some of the longest lived bird species, and the two species examined so far have been shown to possess UVS pigments. The objective of this study was to investigate the prevalence of UVS pigments across long-lived parrots, macaws and cockatoos, and therefore assess whether they need to cope with the accumulated effects of exposure to UV-A and UV-B over a long period of time. Sequences from the SWS1 opsin gene revealed that all 14 species investigated possess a key substitution that has been shown to determine a UVS pigment. Furthermore, in vitro regeneration data, and lens transparency, corroborate the molecular findings of UV sensitivity. Our findings thus support the claim that the Psittaciformes are the only avian Order in which UVS pigments are ubiquitous, and indicate that these long-lived birds have UV sensitivity, despite the risks of photodamage.

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