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At least 55 records · Page 3Linked to original sources
PubMed2002

Imaging of the optic disc and retinal nerve fiber layer: the effects of age, optic disc area, refractive error, and gender.

We cross-sectionally examined the relationship between age, optic disc area, refraction, and gender and optic disc topography and retinal nerve fiber layer (RNFL) measurements, using optical imaging techniques. One eye from each of 155 Caucasian subjects (age range 23.0-80.8 y) without ocular pathology was included. Measurements were obtained by using the Heidelberg Retina Tomography (HRT), the GDx Nerve Fiber Analyzer, and the Optical Coherence Tomograph (OCT). The effects of age were small (R2 < 17%) and were limited to specific HRT, GDx, and OCT parameters. Disc area was significantly associated with most HRT parameters and isolated GDx and OCT parameters. Refraction and gender were not significantly associated with any optic disc or RNFL parameters. Although effects of age on the optic disc and RNFL are small, they should be considered in monitoring ocular disease. Optic disc area should be considered when cross-sectionally evaluating disc topography and, to a lesser extent, RNFL thickness.

Adult↗
PubMed1993

An improved MTT assay.

The MTT assay for cell viability and cell proliferation has been modified to improve its reproducibility and accuracy. The modified test is performed on MultiScreen filtration plates, which permits the removal of the culture medium prior to formazan solubilisation, without loss of cells or formazan crystals. A 1:1 mix of DMSO and ethanol is used as the solvent, since this has the same optical refraction index as the filters, making it possible to measure the optical densities directly on the MultiScreen plate. Data obtained in the assay method using the MultiScreen plate were compared with data from studies employing the normal flat-bottomed plate, by using cells which grow in suspension. Two cell lines were used in the study. CTLL-2, which are IL-2 dependent cells of murine T cell origin, and Jurkat E.6.1 which are IL-2 producing cells of human lymphoma origin. CTLL-2 cells and the modified MTT assay were also used for evaluating the effects of different IL-2 concentrations on cell proliferation.

Animals↗
PubMed2000

Incision sizes with 5.5 mm total optic, 3-piece foldable intraocular lenses.

PURPOSE: To determine incision sizes for 5.5 mm total optic, foldable intraocular lenses (IOLs) made of silicone or hydrophobic acrylic. SETTING: Johann Wolfgang Goethe-University, Department of Ophthalmology, Frankfurt am Main, Germany. METHODS: In a prospective randomized clinical study including 40 cataract procedures with a temporal limbal tunnel approach, incision sizes for 5.5 mm optic, 3-piece foldable IOLs were measured before and after phacoemulsification and before and after IOL implantation using calipers. Three 5.5 mm optic, 3-piece foldable IOLs were used: 2 silicone (Pharmacia CeeOn 912, Allergan SI-55NB) and 1 hydrophobic acrylic (Alcon AcrySof MA30BA). Ten lenses of each model were implanted with a forceps, and 10 SI-55NB IOLs were implanted with the AMO Unfolder injector. Measurements of the tunnel incisions at various times were statistically evaluated using an analysis of variance and the Tukey-Kramer multiple comparison test. RESULTS: Mean tunnel width before and after implantation, respectively, was 3.32 mm+/- 0.06 (SD) and 3.42+/- 0.06 mm for the CeeOn 912 using a Nichamin implantation forceps, 3.28+/- 0.09 mm and 3.42+/- 0.09 mm for the AcrySof MA30BA using a Buratto implantation forceps, 3.00+/- 0.07 mm and 3.10+/- 0.05 mm for the SI-55NB using a Fine Universal II Folder, and 2.66+/- 0.08 mm and 2.81+/- 0.11 mm for the SI-55NB using the AMO Unfolder. Incision sizes before and after implantation were statistically different between 2 IOLs (CeeOn 912 and MA30BA) and the SI-55NB groups. Implantation of the SI-55NB with the Unfolder was associated with significantly smaller incision sizes before and after implantation than implantation with the Fine folder. CONCLUSIONS: Incisions sizes of 2.8 to 3.4 mm were associated with 5.5 mm total optic, 3-piece foldable IOLs. The Allergan SI-55NB high-refractive-index silicone IOL implanted with the AMO Unfolder system provided the smallest postimplantation incision; however, the refractive optic of this IOL is 5.0 mm versus 5.5 mm for of the CeeOn 912 and AcrySof MA30BA.

Acrylic Resins↗
PubMed2004

Nondestructive measurement of an optical fiber refractive-index profile by a transmitted-light differential interference contact microscope.

A novel transmitted-light differential interference contrast (DIC) system is used for nondestructive measurement of the refractive-index profile (RIP) of an optical fiber. By means of this system the phase of a measured light beam can be modulated with an analyzer, and the phase distribution of a fiber is obtained by calculation of the various interference patterns. The measurement theory and structure and some typical applications of this system are demonstrated. The results of measuring RIPs in graded-index fiber are presented. Both the experimental results and theoretical analysis show that the system takes the advantage of high index resolution and of sufficient measurement accuracy for measuring the refractive index of the optical fiber. The system has strong ability to overcome environmental disturbance because of its common-path design. Moreover, one can use the system to measure the RIP along the fiber axis and acquire an image of the three-dimensional RIP of the fiber.

Journal Article↗
PubMed2004

Control of laser-beam propagation and absorption in a nanoplasma gas by programming of a transient complex refractive index with a prepulse.

By utilizing the intensity- and duration-dependent heating and expansion rate of nanoplasma to generate a transient transverse gradient of the refractive index, prepulse controlled laser-beam propagation is demonstrated. The dynamical response of the macroscopic optical refractive index is traced back to the microscopic polarizability of nanoplasmas experimentally, in accordance with hydrodynamic nanoplasma models. In particular, the delay between the prepulse and the main pulse for maximum Rayleigh scattering is found to be longer than that for maximum x-ray emission, supporting the more refined one-dimensional self-consistent hydrodynamic nanoplasma model.

Journal Article↗
PubMed2000

The influence of age, gender, refractive error, and optic disc size on the optic disc configuration in Japanese normal eyes.

PURPOSE: To investigate the influence of age, gender, refractive error, and optic disc size on optic disc configuration in Japanese normal eyes. METHODS: Ninety-two eyes from 92 visually normal Japanese subjects (mean refractive error+/-SD: -1.26+/-2.25 D, range -8 D to +3 D) were examined using a confocal scanning laser tomograph, TopSS. The following disc parameters were investigated: disc size, total or quadrant C/D area ratio and neuroretinal rim area, half-depth area, volume below, and average cup depth. RESULTS: The disc diameter ( mean+/-SD: 1.84+/-0.16 mm) and disc size showed highly significant correlations with the C/D ratio (p<0.001) and the neuroretinal rim area (p<0.001). No other correlation was observed. CONCLUSION: These results indicate that the optic disc diameter and disc size have higher correlations with the optic disc configuration than age, gender, and refractive error in Japanese. These results are similar to those data reported for eyes of Caucasians or Afro Americans, and should be considered when optic discs are evaluated.

Adult↗
PubMed2006

[Effects of experimentally induced hyperopic optical defocus on refractive status of adolescent monkeys].

OBJECTIVE: To determine if chronic optical defocus alters refractive development in monkeys at ages corresponding to the typically developed age of myopia in human children. METHODS: A hyperopic anisometropia was produced in 7 adolescent rhesus monkeys by photorefractive keratectomy (PRK). The laser procedures were performed when the monkeys were 2.0 to 2.5 years old, which corresponded to approximately 8-10 years old in human being. The ocular effects of the induced anisometropia were assessed periodically by corneal topography, retinoscopy and A-scan ultrasonography. RESULTS: By about 30 days post-PRK, the experimentally induced refractive errors was stabilized and the treated eyes were between +0.75 and +2.25 D more hyperopic than their fellow eyes. Subsequently, 7 monkeys showed systematic reductions in the degree of anisometropia. Although some regression in corneal power occurred, the compensating refractive changes were primarily due to the differences in vitreous chamber growth (r = 0.74, P = 0.046). CONCLUSIONS: Vision-dependent mechanisms that are sensitive to refractive error are still active in adolescent primates and probably play a role in maintaining stable refractive errors in the two eyes. Consequently, conditions that result in consistent hyperopic defocus could potentially contribute to the development of juvenile onset myopia in children.

Animals↗
PubMed2006

Astigmatism control.

Refractive cataract surgery has become a reality for the modern phacosurgeon, and control of astigmatism plays a vital role in this quest for optical refractive outcomes. Fortunately, a number of effective options exist to minimize postoperative cylinder. These include placing the cataract incision on the steep corneal meridians; use of adjunctive corneal or limbal relaxing incisions; or even using advanced technology, such as the excimer laser. Careful attention must be directed to the measurement of pre-existing astigmatism, and a detailed surgical strategy must then be formulated. Finally, one must be able to avail themselves of enhancement techniques to address residual astigmatism.

Astigmatism↗
PubMed1994

Changes in refractive trends and optical components of Hong Kong Chinese aged over 40 years.

The age trends of refractive errors, astigmatism and optical components were studied in 220 Chinese subjects aged over 40 years. Myopia did not dominate in this age group. With increasing age, the prevalence of hyperopia increases from 2% at age 40-45 years to 66% at age > 65 years. Against-the-rule astigmatism was more prevalent than the other types. Significant correlations were found between age and spherical equivalent power, age and vitreous depth and axial length. Sex differences were found among the optical components but not in the refractive error. Myopia appears to be more prevalent among the younger age groups than the older age groups of the Hong Kong Chinese population, and the importance of genetics in determination of refractive error is called into question by these findings.

Adult↗
PubMed2002

Light collimation, imaging, and concentration at the thermodynamic limit.

A new type of optical instrument, the curved hologram, is introduced that allows us the unique opportunity to independently control its spatial phase function and its shape (whereas in reflecting or refracting optical elements the shape uniquely determines the spatial phase function). We show how proper design of the hologram shape (using a simple analytic procedure) yields perfect uniform collimation and also collimation and concentration of diffuse (monochromatic) light at the thermodynamic limit of brightness conservation. The results of our experimental demonstration as well as those of our numerical ray-tracing simulations verify our design.

Journal Article↗
PubMed1991

[Modification of refraction and visual noise perception by suction cup oculocompression].

In 17 ocularly healthy persons the IOP was artificially raised by suction cup oculopression (negative pressure: 65 mmHg [8.67 kPa]) from initially 15.5 +/- 2.2 mmHg (2.07 +/- 0.29 kPa) to 25.2 +/- 4.0 mm Hg (3.36 +/- 0.53 kPa) (mean +/- SD). Continuing the initial refractive correction, visual acuity (Landolt's rings) decreased from initially 1.06 +/- 0.13 to 0.39 +/- 0.22 (P less than 0.001* [*t-test, paired ties each]). A new optical refraction with suction cup in position significantly raised the visual acuity to 0.64 +/- 0.24 (P less than 0.002*). The suction cup itself induced astigmatism of 2.15 +/- 1.46 dpt (Canon Auto-Refractometer RK-1), which significantly differed from the initial astigmatism (0.32 +/- 0.23 dpt) (P less than 0.001*). The minus cylinder axis initially showed no preferential position. During artificial IOP elevation it shifted to 90 degrees...125 degrees (referred to the right eye) and thus ran about perpendicular to the meridian the suction cup was positioned on the eyeball. Effects of such refractive changes on differential light threshold and VEP amplitude are demonstrated. The results presented allow critical interpretation of previous IOP tolerance tests. The influence of suction cup oculopression on the perception of the white-noise field is shown in some glaucoma patients: the speed of the white-noise campimetry allows the increase in field defects during artificial IOP elevation to be followed up directly.

Adult↗
PubMed2006

Temperature-dependent complex indices of refraction for crystalline (NH(4))(2)SO(4).

We present a significantly improved set of complex indices of refraction (optical constants) for crystalline (NH(4))(2)SO(4) at 298 K, determined from extinction spectra measured in an aerosol flow tube (AFT). The improved values provide more accurate reproductions of experimental extinction spectra when used in light scattering calculations (Mie, T-matrix, etc.). Optical constants were also derived from measurements using a cryogenic AFT at 243, 223, and 213 K, temperatures characteristic of the upper troposphere and stratosphere. Only minor changes in the optical constants were observed down to 223 K, the transition temperature to the ferroelectric phase, after which significant changes were observed. Here we report the first complex indices of refraction at reduced temperatures for both phases of crystalline (NH(4))(2)SO(4).

Journal Article↗
PubMed2004

The influence of age, sex, race, refractive error and optic disc parameters on the sensitivity and specificity of scanning laser polarimetry.

PURPOSE: To evaluate the influence of age, sex, race, refractive error and optic disc topography on the sensitivity and specificity of scanning laser polarimetry (SLP) in the diagnosis of glaucoma. METHODS: A total of 88 normal individuals and 95 glaucoma patients were included in this study. Glaucoma was defined on the basis of both optic nerve damage and visual field defects. Scanning laser polarimetry, optic disc topography, automated perimetry and refractometry were performed in all subjects. The sensitivity and specificity of SLP were assessed applying a previously calculated cut-off to a previously described linear discriminant function (LDF). RESULTS: The sensitivity and specificity of SLP in the study population were 82% and 83%, respectively. Sensitivity and specificity were not affected by age, sex, race, average disc diameter or disc area. The sensitivity of SLP tended to be higher in myopes (93%) than in emmetropes (80%) and hyperopes (71%) (p = 0.08). Sensitivities were higher in individuals with cup areas > 0.96 mm(2) (89%), rim areas < or = 1.36 mm(2) (92%), and cup area/disc area ratios > 0.45 (89%) (p < 0.05). Stepwise logistic regression analysis indicated that the presence of a cup area > 0.96 mm(2) and a rim area < 1.36 mm(2) significantly increased the sensitivity of the LDF, whereas a cup area/disc area ratio < or = 0.45 significantly increased the specificity of the LDF. CONCLUSION: The sensitivity and specificity of SLP may be influenced by refractive error and optic disc parameters that are affected by glaucomatous damage (cup area, rim area and cup area/disc area ratio). These parameters must be considered in studies evaluating the sensitivity and specificity of optic nerve/retinal nerve fibre layer imaging technologies.

Age Factors↗
PubMed2006

Self-aligned spatial filtering using laser optical tweezers.

We present an optical spatial filtering device that has been integrated into a microfluidic system and whose motion and alignment is controlled using a laser optical tweezer. The lithographically patterned micro-optical spatial filter device filters out higher frequency additive noise components by automatically aligning itself in three dimensions to the focus of the laser beam. This self-alignment capability is achieved through the attachment of a refractive optical element directly over the circular aperture or pinhole of the spatial filter. A discussion of two different spatial filter designs is presented along with experimental results that demonstrate the effectiveness of the self-aligned micro-optic spatial filter.

Equipment Design↗
PubMed2004

[Third order nonlinear optical properties of three kinds of metal phthalocyanines].

Using YAG laser, the nonlinear optical refractive indexes of three kinds of metal phthalocyanines in DMF, ZnPCS(C6H32N8S4Zn), AlPCS (C56H32AlClN8S4) and AlPCP (C6H32AlClN8O4) were studied with the method of Z-scan. Their third-order susceptibilities chi(3) were also calculated. The result shows that different central ion and different substituents could affect their third-order susceptibilities. The mechanisms of third order optical nonlinearity and energy transfer in the photodynamic therapy were discussed.

Coloring Agents↗
PubMed1986

Optical problems following refractive surgery.

All of the refractive surgical procedures share the common optical complications of glare and photophobia, undercorrection and overcorrection, regular and irregular astigmatism, loss of best corrected acuity, fluctuation in visual acuity, loss of progression of effect, and monocular diplopia. This review presents the different clinical settings under which these various complications can occur. Many of the complications are associated with technical problems at the time of surgery and abnormalities in the resurfacing of the cornea after surgery. Many of these complications can be corrected by glasses, contact lenses, or repeat refractive surgical procedures.

Adult↗