scholarly journals Changes of Corneal Biomechanical Properties upon Exclusive Ytt-/Sr-90 Irradiation of Pterygium

Sensors ◽  
2021 ◽  
Vol 21 (3) ◽  
pp. 975
Author(s):  
Fritz Rigendinger ◽  
Daniel M. Aebersold ◽  
Zeljka Cvejic ◽  
Bojan Pajic
Keyword(s):  
Visual Quality ◽  
Biomechanical Properties ◽  
First Year ◽  
Wavefront Aberration ◽  
Human Cornea ◽  
Corneal Aberrations ◽  
Horizontal Length ◽  
Quality Of Vision ◽  
Pterygium Excision

Background: It is known that pterygia above a certain size cause astigmatism and other aberrations of the human cornea and thus impair the quality of vision. Exclusive Sr-/Ytt-90 beta irradiation is a highly effective treatment for primary pterygia. The aim of this retrospective study is to determine the extent to which higher order corneal aberrations are affected by this treatment. Methods: Evaluation of corneal topographies and wavefront aberration data of 20 primary pterygia patients generated before and at different points in time in the first year after irradiation. Additionally, the size of the pterygium was measured. Results: The study showed a significant increase in coma and triple leaf aberrations in pterygia with a horizontal length of 2 mm and more. It was also found that a pterygium size greater than 2 mm significantly induces astigmatism. Both phenomena reduce visual quality. In none of the patients could a pterygium recurrence be detected after irradiation. Conclusions: If the pterygium size is less than 2 mm, early exclusive Sr/Ytt-90 beta irradiation can be recommended. If the size is more than 2 mm, a pterygium excision 6 months after beta irradiation can be discussed.

scholarly journals On the Relationship between Corneal Biomechanics, Macrostructure and Optical Properties

2021 ◽  
Author(s):  
Francisco J. Ávila ◽  
Laura Remón ◽  
Maria Concepción Marcellán
Keyword(s):  
Optical Properties ◽  
Biomechanical Properties ◽  
Optical Quality ◽  
Optical Transparency ◽  
Optical Aberrations ◽  
Corneal Aberrations ◽  
Scheimpflug Imaging ◽  
The Hierarchical Structure ◽  
The Relationship

Optical properties of the cornea are responsible for correct vision, ultrastructure allows optical transparency and biomechanical properties governs the shape, elasticity or stiffness of the cor-nea affecting ocular integrity and intraocular pressure. Therefore, optical aberrations, corneal transparency, structure and biomechanics play a fundamental role in the optical quality of hu-man vision, ocular health and refractive surgery outcomes. However, the convergence of those properties is not yet reported at macroscopic scale within the hierarchical structure of the cornea. This work explores the relationships between biomechanics, structure and optical properties (corneal aberrations and optical density) at macrostructural level of the cornea through dual Placido-Scheimpflug imaging and air-puff tonometry systems in a healthy young adult popula-tion. Results showed convergence between optical transparency, corneal macrostructure and biomechanics.

“OKVision® SMARTFIT™” Customizable Mini-Scleral Lenses Fitting Guide

The Eye ◽  
2021 ◽  
Vol 23 (1) ◽  
pp. 41-51
Author(s):  
N. A. Bakalova
Keyword(s):  
Basic Skills ◽  
Professional Knowledge ◽  
Visual Quality ◽  
High Quality ◽  
Basic Principles ◽  
Daily Care ◽  
Quality Of Vision ◽  
Parameters Calculation ◽  
Clinical Cases

As of today, scleral lenses are the only optical rehabilitation method that provides high visual quality of vision for patients with irregular cornea. This fitting guide is aimed at helping ophthalmologists acquire professional knowledge in the field of fitting scleral lenses and suggest tactics for managing patients with irregular corneas.The workshop outlines indications for prescribing scleral lenses, describes the basic principles of lens parameters calculation and fitting, taking into account the patientspecific parameters of the eyes. In addition, guidelines for acquiring skills in assessing and changing the position of scleral lenses on the patient’s eye, using customization options, daily care, manipulations for inserting on and removing lenses, and further dispensary observation are given.Mastering the basic skills of calculation and fitting customized scleral lenses helps practitioners expand their areas of practice, enhance professional competitiveness and provide patients with high quality vision, even in the most difficult clinical cases.

scholarly journals The corneal biomechanical changes after SMILE and LASIK refractive surgery were compared based on finite element analysis

2021 ◽  
Vol 271 ◽  
pp. 03045
Author(s):  
Yinyu Song ◽  
Lihua Fang ◽  
Ruirui Du ◽  
Luchao Lin ◽  
Xingming Tao
Keyword(s):  
Finite Element ◽  
Refractive Surgery ◽  
Three Dimensional ◽  
Element Model ◽  
Biomechanical Properties ◽  
Stress And Strain ◽  
Wavefront Aberration ◽  
Human Cornea ◽  
Element Analysis ◽  
Wavefront Aberrations

The three-dimensional (3D) finite element model of human eye was established, and the intraocular pressure (IOP) was loaded to simulate refractive surgery. The biomechanical properties of human cornea after SMILE and LASIK surgery were studied from the stress, strain and induced wavefront aberration. Our results showed that SMILE had less impact on the biomechanics, having less stress and strain changes than LASIK. However, the stress and strain of the cornea increased with the increase of the diopter and were concentrated in the central region. We also investigated the changes in wavefront aberrations of the cornea after surgery, and the results indicated that the defocus and vertical commotion were significantly affected by SMILE and LASIK surgery, while the remaining aberrations were approximately unchanged. In conclusion, both SMILE and LASIK sergury procedures changed the postoperative corneal biomechanics, but SMILE had less impact on the biomechanics of corneal.

scholarly journals One-year effect of wearing orthokeratology lenses on the visual quality of juvenile myopia: a retrospective study

PeerJ ◽  
2019 ◽  
Vol 7 ◽  
pp. e6998 ◽  
Author(s):  
Yewei Yin ◽  
Yang Zhao ◽  
Xiaoying Wu ◽  
Mengyang Jiang ◽  
Xiaobo Xia ◽  
...  
Keyword(s):  
Visual Quality ◽  
Wavefront Aberration ◽  
Corneal Curvature ◽  
Modulation Transfer ◽  
Year Effect ◽  
Significant Difference ◽  
Before And After ◽  
One Year ◽  
The One

Objective To study the one-year effect of wearing orthokeratology (OK) lenses on the visual quality of juvenile myopia. Methods The right eyes of 36 juvenile myopias were retrospectively studied in this work. Q-value, e-value, corneal curvature, strehl ratio (SR), modulation transfer function (MTF) and wavefront aberration (WA) were compared before and at 1, 3 and 12 months after wearing OK lenses. The SR, MTF and WA of cornea, internal optic and ocular were analyzed separately. The spherical and cylinder diopter, vision acuity, compensating factor (CF) and compensative rate (CF%) were compared before and at 12 months after wearing OK lenses. Results (1) The vision of LogMAR increased and the corneal curvature decreased significantly after wearing OK lenses. There was no significant difference for the e-value before and after wearing OK lenses. The Q-value increased at 1 month but decreased at 3 and 12 months remarkably. (2) The ocular and internal optic SR and MTF increased significantly at 1 month and then remained stable. The MTF in different spacial frequencies increased after wearing OK lenses. There was no significant difference for the corneal SR before and after wearing OK lenses, and the corneal MTF decreased significantly after wearing OK lenses. (3) For the ocular, the total higher order aberration (HOA), spherical, coma and trefoil aberrations increased, and the total aberration, total lower order aberration (LOA) and defocus aberration decreased obviously except astigmatism. The corneal aberrations increased significantly after wearing OK lenses except astigmatism. For the internal optic, the total aberration, total LOA and defocus aberration decreased, and the total HOA, coma and trefoil aberration increased significantly except the astigmatism and spherical aberrations. (4) The CF and CF% of total aberration, total LOA, total HOA and coma aberrations increased, and those of astigmatism and spherical decreased at 12 months. Conclusions Orthokeratology is effective in correcting the refractive error and improving the vision quality of juvenile myopia over the one-year follow-up period.

scholarly journals Visual Outcomes and Higher Order Aberrations Following LASIK on Eyes with Low Myopia and Astigmatism

2018 ◽  
Vol 12 (1) ◽  
pp. 84-93 ◽  
Author(s):  
Smita Agarwal ◽  
Erin Thornell ◽  
Chris Hodge ◽  
Gerard Sutton ◽  
Paul Hughes
Keyword(s):  
Visual Acuity ◽  
Contrast Sensitivity ◽  
Spherical Aberration ◽  
Higher Order ◽  
Higher Order Aberrations ◽  
Corneal Aberrations ◽  
Spatial Frequencies ◽  
Quality Of Vision ◽  
Recent Developments

Background: Laser-Assisted in situ Keratomileusis (LASIK) can induce corneal aberrations that can impact vision and patient satisfaction. Recent developments in laser technologies have helped minimise these aberrations. Objective: To assess the quality of vision and change in Higher-Order Aberrations (HOAs) following wavefront-optimized LASIK in low-myopic astigmatic patients. Methods: LASIK was performed on a total of 76 eyes in patients with myopia <4.0 D and cylinder <2.0 D using the WaveLight® EX500 excimer and FS200 femtosecond laser platform. Visual acuity, contrast sensitivity and HOAs were measured at 1 and 3 months postoperatively and compared to preoperative values. Subjective quality of vision was assessed pre- and postoperatively using a VF14 questionnaire. Results: Mean postoperative Spherical Equivalent (SE) was -0.09 ± 0.26 µm with 95% of patients within ± 0.5 D of attempted SE. Postoperative uncorrected distance visual acuity was 20/20 or better for 96% of patients. Contrast sensitivity increased against horizontal and vertical gratings at all spatial frequencies except for vertical gratings at 18 cycles/degree. Spherical aberration and total HOA increased by 0.085 µm and 0.13 µm respectively. The mean VF14 score increased from 89.2 ± 16.7% to 99 ± 1.4% postoperatively. Conclusion: LASIK performed using the WaveLight® EX500 excimer and WaveLight® FS200 laser platform provided improved contrast sensitivity and visual acuity with minimal introduction of HOAs, making it a suitable platform for low myopic astigmatic patients.

scholarly journals Anatomical and Visual Outcomes after LASIK Performed in Myopic Eyes with the WaveLight® Refractive Suite (Alcon® Laboratories Inc., USA)

2020 ◽  
Vol 2020 ◽  
pp. 1-18
Author(s):  
Imene Salah-Mabed ◽  
Sarah Moran ◽  
Emmanuelle Perez ◽  
Guillaume Debellemanière ◽  
Damien Gatinel
Keyword(s):  
Contrast Sensitivity ◽  
Dry Eye ◽  
High Myopia ◽  
Spherical Aberration ◽  
Case Series ◽  
Corneal Aberrations ◽  
Quality Of Vision ◽  
Eye Symptoms ◽  
Dry Eye Symptoms

Purpose. To evaluate changes in corneal anatomy and quality of vision following LASIK refractive surgery for mild to high myopia using the WaveLight® Refractive Suite (Alcon® Laboratories Inc., USA). Setting. Rothschild Foundation, Paris, France. Design. Prospective interventional case series. Methods. We examined 60 myopic eyes (average SE −4.5 D, from −9.3 to −0.75 D) of 30 patients from 21.3 to 38.7 years old. Pachymetry, keratometry, Q factor, corneal aberrations, visual acuity (VA), contrast sensitivity, dry eye assessment, and quality of vision were measured preoperatively, one day (D1), and 1, 3, and 6 months postoperatively. Results. 6 months postoperatively, keratometry became flatter, and the Q factor became more oblate (from −0.18 ± 0.08 to +0.19 ± 0.06). Pachymetry decreased by 117.9 ± 62.2 µm at D1 and increased by 37.87 ± 32.6 µm between D1 and M6. Refraction was emmetropic at D1 and remained stable thereafter. Six months after surgery, VA was slightly but nonsignificantly improved (<0.05 log MAR), whereas contrast sensitivity remained unchanged. Quality of vision was not affected by surgery and was more related to dry eye symptoms than to corneal HOAs (r2 = 0.49; p<0.001 vs. r2 = 0.03; p<0.001). Conclusions. LASIK surgery for moderate to high myopia, performed with the WaveLight® Refractive Suite, showed good postoperative outcomes, with demonstrated safety, predictability, efficiency, and stability. This is probably due to well-controlled spherical aberration and the use of large optical zones. Besides, we can assume that the patients’ quality of vision depends more on the postoperative dry eye disease generated by the laser than on the induced HOAs.

The visualization and assessment of the anterior surface of the cornea using video keratotopography

The Eye ◽  
2020 ◽  
Vol 22 (130) ◽  
pp. 36-43
Author(s):  
Gulnara Andrienko
Keyword(s):  
Contact Lenses ◽  
Corneal Topography ◽  
Topographic Maps ◽  
Specific Situation ◽  
Main Method ◽  
Pathological Conditions ◽  
Quality Of Vision ◽  
Corneal Shape ◽  
Color Map

Corneal topography is the main method for assessing the regularity of the surface of the cornea. Corneal irregularity leads to a deterioration in its refractive properties and a decrease in the quality of vision. Learning the basics of corneal topography will help determine the choice of a color map for a specific situation, as well as understand and analyze the data associated with these maps. This article describes the main types of topographic maps, various patterns of corneal shape in normal and pathological conditions and how to use the data obtained to design and fit contact lenses. Despite the fact that images may vary depending on topographers used, the information presented in this article is universal.

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