Modelling the effects of secondary spherical aberration on refractive error, image quality and depth of focus

2014 ◽  
Vol 35 (1) ◽  
pp. 28-38 ◽  
Author(s):  
Renfeng Xu ◽  
Arthur Bradley ◽  
Norberto López Gil ◽  
Larry N. Thibos
Keyword(s):  
Image Quality ◽  
Refractive Error ◽  
Spherical Aberration ◽  
Depth Of Focus

Modelling of influence of spherical aberration coefficients on depth of focus of optical systems

2017 ◽  
Author(s):  
Petr Pokorný ◽  
Filip Šmejkal ◽  
Pavel Kulmon ◽  
Antonín Mikš ◽  
Jiří Novák ◽  
...  
Keyword(s):  
Spherical Aberration ◽  
Optical Systems ◽  
Depth Of Focus

Relationship between Induced Spherical Aberration and Depth of Focus after Hyperopic LASIK in Presbyopic Patients

Ophthalmology ◽  
2015 ◽  
Vol 122 (2) ◽  
pp. 233-243 ◽  
Author(s):  
Benjamin Leray ◽  
Myriam Cassagne ◽  
Vincent Soler ◽  
Eloy A. Villegas ◽  
Claire Triozon ◽  
...  
Keyword(s):  
Spherical Aberration ◽  
Depth Of Focus

scholarly journals Repeatability of a Dual-Scheimpflug Placido Disc Corneal Tomographer/Topographer in Eyes with Keratoconus

2020 ◽  
Author(s):  
Anne Poulsen ◽  
Diane Jang ◽  
Mahmood Khan ◽  
Zaina Nabil Al-Mohtaseb ◽  
Michael Chen ◽  
...  
Keyword(s):  
Image Quality ◽  
Spherical Aberration ◽  
Correlation Coefficients ◽  
Quality Metrics ◽  
Corneal Surgery ◽  
Image Quality Metrics ◽  
Interclass Correlation ◽  
Intrastromal Corneal Ring ◽  
History Of ◽  
Image Quality Metric

Purpose: To investigate the repeatability of a combined Dual-Scheimpflug placido disc corneal topographer (Zeimer Galilei G4) with respect to keratometric indices used to monitor progression of keratoconus (KCN). Methods: Patients with KCN were prospectively enrolled. For each eye lacking history of corneal surgery, 5 measurements were taken in succession. Eyes in which 3 or more measurements could be obtained (defined by the device's 4 image quality metrics) were included in the analysis. The repeatability limits (RL) and interclass correlation coefficients (ICC) were calculated for various parameters. Results: 32 eyes from 25 patients met all image quality metrics, and 54 eyes from 38 patients met at least 3/4 criteria (all except the placido image quality metric). RLs for key parameters when 4/4 or 3/4 image quality metrics were met included: 0.37 and 0.77 diopters (D) for steep simulated keratometry, 0.79 and 1.65 D for maximum keratometry, 13.80 and 13.88 degrees for astigmatism axis, 0.64 and 0.56 um for vertical coma magnitude, and 3.76 and 3.84 um for thinnest pachymetry, respectively. The ICCs for all parameters were excellent [above 0.87 except for spherical aberration (0.77)]. Conclusions: The dual-Scheimpflug placido disc corneal topographer is highly repeatable in quantifying parameters used in monitoring KCN. Excellent placido images are difficult to capture in eyes with KCN, but when available, increase the reliability of the measurements. The RLs may be especially helpful in detecting progression in mild KCN when interventions such as corneal cross-linking or intrastromal corneal ring segments are most beneficial.

scholarly journals Multimode Trans-Illuminator for the Stereomicroscope

2007 ◽  
Vol 15 (4) ◽  
pp. 40-43
Author(s):  
Ted Clarke
Keyword(s):  
Image Quality ◽  
Lake Water ◽  
Fiber Optic ◽  
Light Guide ◽  
Spherical Aberration ◽  
Main Tool ◽  
Transmitted Light ◽  
Illumination System ◽  
Living Organisms ◽  
Microscopic World

The stereomicroscope was the main tool I once used for metallurgical failure analysis. I have owned a Meiji EMT Greenough-type stereomicroscope since the late 1980's. I had not used transmitted light with the stereomicroscope until about a year ago when I completed a multimode transmitted light illuminator for my Meiji stereomicroscope. I thought this capability would be very useful for introducing the grandkids to the microscopic world, especially with live lake water organisms. My earlier article in Microscopy Today, “Rediscovery of Darkfield Dispersion Staining while Building a Universal Student Microscope,” January/February 2003, demonstrated usefulness of a dual brightfield and darkfield capability in transmitted light for viewing living organisms. I have a ½″ fiber-optic bundle light guide used in the illumination system for my modified Biolam microscope also shown in Microscopy Today, “Effects of Condenser Spherical Aberration on Image Quality,” March 2005.

scholarly journals Changes in forward light scatter parameters as a function of refractive error in young adults

2020 ◽  
Vol 258 (4) ◽  
pp. 925-930
Author(s):  
Manbir Nagra ◽  
Mansi Patel ◽  
John Barbur
Keyword(s):  
Young Adults ◽  
Angular Distribution ◽  
Image Quality ◽  
Refractive Error ◽  
Retinal Image ◽  
Structural Changes ◽  
Visual Performance ◽  
Refractive Errors ◽  
Light Scatter ◽  
Underlying Causes

Abstract Background/aims Some aspects of visual performance worsen with increasing myopia. Whilst the underlying causes are not always clear, reduction in retinal image quality is often attributed to structural changes in the posterior myopic eye. Forward light scatter, originating principally from the cornea and lens, is known to produce veiling glare which subsequently reduces retinal image contrast. It is therefore of interest to investigate whether forward light scatter varies with refractive error. Methods Thirteen young-adult subjects (18–25 years), with mean spherical errors (MSE ± sd, D) RE, − 1.69 ± 2.02 (range 0.38 to − 4.75); LE, − 1.91 ± 1.94 (range 0.50 to − 4.63) underwent binocular assessment of forward light scatter using the AVOT light scatter test. Five glare annuli, with effective eccentricities ranging from 2 to 10°, were used to estimate parameters, k and n, which define the light scatter function of the eye. These were then used to calculate the area under the light scatter function (k′) and the total volume of light scatter (k″). Results Significant correlation was found between increasing myopia and k′ values (RE, p < 0.05; r = 0.64; LE, p < 0.05, r = 0.66). Neither the ‘volume’ of light scatter (k″), the parameter, n, which controls the angular distribution of light scatter, or the straylight parameter constant, k, were significantly correlated with refractive error (p > 0.05 for both eyes). Axial length was also not correlated with any of the light scatter parameters measured. Conclusion The preliminary data from this study provide evidence that some light scatter parameters may be correlated with refractive error. Further studies are needed to characterize how changes in the anterior media of the eye, and inclusion of a wider range of refractive errors, may affect forward light scatter.

Extended Depth of Focus With Induced Spherical Aberration in Light-Adjustable Intraocular Lenses

2014 ◽  
Vol 157 (1) ◽  
pp. 142-149 ◽  
Author(s):  
Eloy A. Villegas ◽  
Encarna Alcón ◽  
Sandra Mirabet ◽  
Inés Yago ◽  
José María Marín ◽  
...  
Keyword(s):  
Spherical Aberration ◽  
Intraocular Lenses ◽  
Depth Of Focus ◽  
Extended Depth Of Focus

Spherical Aberration and Depth of Focus

Ophthalmology ◽  
2008 ◽  
Vol 115 (9) ◽  
pp. 1641 ◽  
Author(s):  
George Beiko
Keyword(s):  
Spherical Aberration ◽  
Depth Of Focus

scholarly journals Influence of Angle Alpha on Visual Quality after Implantation of Extended Depth of Focus Intraocular Lenses

2021 ◽  
Author(s):  
Miaomiao Qin ◽  
Min Ji ◽  
Tianqiu Zhou ◽  
Yurong Yuan ◽  
Jiawei Luo ◽  
...  
Keyword(s):  
Visual Acuity ◽  
Spherical Aberration ◽  
Visual Quality ◽  
Intraocular Lenses ◽  
Patient Questionnaire ◽  
Modulation Transfer ◽  
Depth Of Focus ◽  
Extended Depth Of Focus ◽  
Postoperative Changes ◽  
Angle Alpha

Abstract Background: To assess postoperative changes in angle alpha, and to evaluate the postoperative visual quality of patients with different angle alpha values after implantation of extended depth of focus (EDOF) intraocular lenses (IOLs).Methods: Seventy-nine eyes of 79 patients who had phacoemulsification with EDOF IOLs implantation were enrolled. A cut-off value of 0.3 mm, 0.4 mm, and 0.5 mm in preoperative angle alpha was chosen to divide eyes into groups. Distance, intermediate, and near visual acuities, modulation transfer function (MTF), and aberrations were recorded during a 6-month follow-up. A patient questionnaire was completed. Results: There were no significant differences in angle alpha postoperatively compared to preoperatively. No significant differences were found in visual acuity and MTF between all groups. With 5mm pupil diameter, there were significant differences of higher-order aberrations and spherical aberration in ocular aberration and internal aberration between angle alpha＜0.4 mm and angle alpha≥ 0.4 mm. Additionally, significant differences of coma were also added in cut-off value of 0.5 mm. When the value of angle alpha is 0.4 mm or higher, there were significant differences in the score of halos and glare.Conclusions: Angle alpha did not affect visual acuity, but the value of 0.4 mm or higher in angle alpha affected the visual quality under scotopic conditions and occurrence of halos and glare. For patients with 0.4 mm or higher in angle alpha, the decision to implant a EDOF IOL should be carefully considered.

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