Purpose: To explore the relationship between lens power and refractive error in older adults following age-related hyperopic shifts.Methods: From the Shahroud eye Cohort Study, subjects aged 55‑64 years without clinically significant cataracts (with nuclear opacity of grade 0 to 1) were included to maximize the proportion of subjects with age‑related hyperopic shifts that normally occur between 40 to 60 years of age, before interference from the myopic shift due to nuclear cataracts. Mean axial length (AL) values, corneal power, anterior chamber depth, lens thickness, and lens power were analyzed and compared among three refractive groups (myopes, emmetropes, and hyperopes).Results: A total of 1, 006 subjects including 496 (49.63%) male subjects were studied. Corneal power was similar in all refractive groups. Hyperopes had+1.69 diopters higher mean spherical equivalent refractive error and - 0.50 mm shorter AL than emmetropes. Myopes had 0.67 mm longer AL than emmetropes.Hyperopes had significantly increased lens thickness as compared to emmetropes (4.42 vs.4.39 mm respectively). In this adult sample, the hyperopic group had lower lens power (+22.29 diopters vs.+22.54 diopters in emmetropes, P=0.132). Myopes had similar lens power as emmetropes.Conclusion: Axial length is the principal determinant of refractive errors. lens power may have importance in determining hyperopia in adults free of cataract.

Gap junctions are responsible for the direct coupling of cells that enables intercellular exchange of ions, small metabolites and second messengers. lens epithelial cells are well coupled (Fig.1a) by connexin (Cx) channels that constitute the structural subunits of gap junctions.Surprisingly, epithelial cell proliferation during the early postnatal period (Fig.1b) was found to be profoundly influenced by the type of connexin subunit present in the gap junction channels between cells. The loss, or functional replacement, of Cx50 caused a significant decrease in the number of dividing cells during the first postnatal week, suggesting that Cx50-mediated communication was essential for peak mitosis to occur.

Background: Calibration of Thermo Luminescent Dosimetry (TLD) in eye lens dosimeter requires a standard phantom. The use of anthropomorphic phantoms in calibration needs evaluation. Objective: This study aimed to analyze the angular response of the TLD on the fabricated 3D anthropomorphic head phantom and Computerized Imaging Reference Systems (CIRS)-Computed Tomography (CT) dose phantom as a standard phantom irradiated with Cs-137 and to compare the absorbed dose and linear attenuation for both phantoms. Hp(3) analysis, conversion coefficient (hpK(3)), and calibration factor (CF) are also investigated. Material and Methods: In this experimental study, the fabricated 3D printed anthropomorphic head phantom was analyzed using polylactic acid (PLA) with the skull and then filled with the artificial brain and cerebrospinal fluid (CSF) as a test phantom. TLD-700H and TLD Reader Harshaw 6600 plus were used to analyze the angular response of Cs-137 radiation and to determine the absorbed dose and linear attenuation coefficient of test and standard phantoms. Results: The effect of the angle of radiation source towards TLD reading at the anthropomorphic head phantom has a similar value to the standard phantom with a calibration factor ranging from 0. 82 to 1. The absorbed dose measurement and the linear attenuation coefficient of the anthropomorphic head phantom with the standard phantom have different values of 2. 52 and 3. 78%, respectively. Conclusion: The fabricated 3D printed anthropomorphic head phantom has good potential as an alternative to standard phantoms for TLD calibration in eye lens dosimeter.

Background: Estimation of eye lens dose is important in head computed tomography (CT) examination since the eye lens is a sensitive organ to ionizing radiation. Objective: The purpose of this study is to compare estimations of eye lens dose in head CT examinations using local size-specific dose estimate (SSDE) based on size-conversion factors of the American Association of Physicists in Medicine (AAPM) Report No. 293 with those based on size-conversion factors of the AAPM Report No. 220. Material and Methods: This experimental study is conducted on a group of patients who had undergone nasopharyngeal CT examination. Due to the longitudinal (z-axis) dose fluctuation, the average global SSDE and average local SSDE (i. e. particular slices where the eyes are located) were investigated. All estimates were compared to the measurement results using thermo-luminescent dosimeters (TLDs). The estimated and measured doses were implemented for 14 patients undergoing nasopharyngeal CT examination. Results: It was found that the percentage differences of the volume CT dose index (CTDIvol), average global SSDE based on AAPM No. 220 (SSDEo, g), average local SSDE based on AAPM No. 220 (SSDEo, l), average global SSDE based on AAPM No. 293 (SSDEn, g) and average local SSDE based on AAPM No. 293 (SSDEn, l) against the measured TLD doses were 22. 5, 21. 7, 15. 0, 9. 3, and 2. 1%, respectively. All comparisons between dose estimates and TLD measurements gave p-values less than 0. 001, except for SSDEn, l (p-value = 0. 566). Conclusion: SSDE based on AAPM Report No. 293 can be used to accurately estimate eye lens radiation doses by performing the calculations on a number of specific slices containing the eyes.