Does transient increase in axial length during accommodation attenuate with age?

Background: The aim was to profile transient accommodative axial length (AXL) changes from early adulthood to advanced presbyopia and to determine whether any differences exist between the responses of myopic and emmetropic individuals. Methods: Ocular biometry was measured by the LenStar biometer (Haag-Streit, Switzerland) in response to 0.00, 3.00 and 4.50 D accommodative stimuli in 35 emmetropes and 37 myopes, aged 18 to 60 years. All results were corrected to reduce errors arising from the increase in crystalline lens thickness with accommodation. Accommodative responses were measured sequentially by the WAM 5500 Auto Ref/Keratometer (Grand Seiko, Japan). Results: AXL increased significantly with accommodation (p<0.001), with a mean corrected AXL elongation of 2 ± 18 µm and 8 ± 16 µm observed at 3.00 D and 4.50 D, respectively. The magnitude of accommodative AXL change was not dependent on refractive error classification (p=0.959), however a significant reduction in the magnitude and variance of AXL change was evident after 43-44 years of age (p<0.002). Conclusion: The negative association between transient AXL elongation and age, in combination with reduced variance of data after age 43-44 years, is consistent with a significant increase in posterior ocular rigidity, which may be influential in the development of presbyopia

Laser Anemometer Measurements of Turbulence in Non‐Newtonian Pipe Flows

The structure of turbulence for pipe flows of dilute polyethylene oxide and polyacrylamide solutions is investigated using a laser anemometer technique. The instrumentation of the optical system and signal processing needed to satisfy the optical requirements and the signal‐to‐noise ratio are presented. The spatial requirement of the beam signal is described with regard to the lens, aperture, wavelength, and the angular alignment of the scattered and reference beams. A gravity‐flow system is used to minimize the degradation of polymer solutions. The measurements of wall pressure drops indicate that the polymer additives used give a consistent delay of transition from laminar flow to turbulence, as compared with Newtonian fluids. The axial turbulence intensities for polymer solutions are found to be substantially reduced, compared with results obtained for water.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70393/2/PFLDAS-15-4-546-1.pd

Grundlagen, Methodik und modulares Geraetesystem fuer die objektive Hoerbahndiagnostik, insbesondere bei Kleinkindern Abschlussbericht

The electric stimulability of the auditory nerve is a basic requirement of function of a cochlear implant (CI). Nevertheless most CI teams dispense with any proof of this stimulability in young children before the implantation operation. Some failures are to be explained by this fact. A cooperation-free test based on electrically evoked auditory potentials is needed being applicable within the preliminary examinations. With this aim theoretical considerations were made and experimental investigations were carried out and resulted in the following findings: 1) In young children electrically evoked amplitude modulation following responses (E-AMFR) may be obtained with stimulation within the outer ear canal (all examinations were carried out in general anaesthesia). 2) In older children and adults promontory stimulation after local anaesthesia is indicated. 3) In more than 70% of all cases also brainstem auditory evoked potentials (E-BAEP) may be obtained by capacitor-discharge stimulation (stimulation site like 1) or 2)). Electrodes suitable for outer ear or promontory stimulation are shown. The technical equipment will be produced by PILOT Blankenfelde GmbH, D-15827 Blankenfelde. (orig.)Available from TIB Hannover: F98B1465 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman