Estimating Total Corneal Astigmatism From Anterior Corneal Data

Conclusions: It was possible to estimate TCA accurately from anterior corneal data with a new formula. However, application of both this model on keratometric data and of direct Pentacam measurements in a group of 40 eyes with TIOLs did not completely eradicate the refractive error in TIOL calculation. More studies comparing Pentacam TCA and refractive astigmatism are required.
Source: Cornea - Category: Opthalmology Tags: Clinical Science Source Type: research

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Conclusions: The phacoemulsification with CCI distances ranging from 0.5 mm to 1.5 mm is an effective and safe therapy to senile cataract. The CCI distance anterior to the limbus that ranges from 0.5 mm to 1.5 mm is recommended for routine phacoemulsification. PMID: 31531233 [PubMed]
Source: Journal of Ophthalmology - Category: Opthalmology Tags: J Ophthalmol Source Type: research
ConclusionsTo the best of our knowledge, this is the first report to describe corneal ectasia in a patient with keratoconus following phacoemulsification surgery. Cataract surgeons should provide extra caution to patients with keratoconus and take into consideration this rare but potentially sight-threatening complication.
Source: Journal of Medical Case Reports - Category: General Medicine Source Type: research
nhao Li A third-order aberration theory has been developed for the Offner imaging spectrometer comprising an extended source; two concave mirrors; a convex diffraction grating; and an image plane. Analytic formulas of the spot diagram are derived for tracing rays through the system based on Fermat’s principle. The proposed theory can be used to discuss in detail individual aberrations of the system such as coma, spherical aberration and astigmatism, and distortion together with the focal conditions. It has been critically evaluated as well in a comparison with exact ray tracing constructed using the commercia...
Source: Sensors - Category: Biotechnology Authors: Tags: Article Source Type: research
ConclusionsIn manifest conditions, the accuracy of the 2Win and plusoptiX A12R refractometers is low in hyperopia and astigmatism, but the devices are well correlated with each other, and both have high specificity and low sensitivity in hyperopia, resulting in the underestimation of hyperopic refractive error. The optional Plusoptix sensitive referral criteria seems to be appropriate for the A12R. The 2Win provided fewer inconclusive results and was preferred for use with younger and developmentally delayed children.
Source: Journal of American Association for Pediatric Ophthalmology and Strabismus - Category: Opthalmology Source Type: research
Abstract Purpose: To measure changes in visual performances and optical quality in myopic children during the first month of wearing orthokeratology lens, and to reveal the association between those two. Methods: Thirty-five myopic children participated in this study. Visual performances were evaluated with visual acuity and shape discrimination threshold (SDT) for radial frequency patterns. Placido disc-based corneal topography for central 4 mm and 6 mm zones was collected and decomposed by Fourier analysis into the spherical, asymmetric, and regular astigmatic components. Root-mean-square of third-order, fourth-...
Source: Current Eye Research - Category: Opthalmology Authors: Tags: Curr Eye Res Source Type: research
Publication date: Available online 12 September 2019Source: Journal of American Association for Pediatric Ophthalmology and StrabismusAuthor(s): Gayathri Srinivasan, Diane Russo, Christopher Taylor, Anthony Guarino, Paulette Tattersall DipPharm, Bruce MooreAbstractPurposeTo evaluate the Spot Vision Screener in detecting targeted vision disorders compared to cycloplegic retinoscopy in children
Source: Journal of American Association for Pediatric Ophthalmology and Strabismus - Category: Opthalmology Source Type: research
AbstractThree-dimensional analyses of optical aberrations of metasurface flat lenses are presented via ray tracing. The ray tracing is performed on the basis of anomalous refraction/reflection law specialized for metasurface instead of conventional Snell law. Relationship between spherical aberration and working distance, feature of chromatic aberration, astigmatism in meridian, and sagittal directions are analyzed numerically to fully reveal the aberration characteristics. Through the curve descriptions of geometric point spread function (PSF) and the modulation transfer function (MTF), the influence of monochrome aberrat...
Source: Plasmonics - Category: Biomedical Science Source Type: research
Conclusion: Over 40% of the patients undergoing cataract surgery enrolled in this study had more than 1.0 D of corneal astigmatism and may benefit from the use of toric intraocular lenses. These data can be useful for planning to make this technology available fo r patients.RESUMO Objetivo: Avaliar a preval ência do astigmatismo corneano antes da cirurgia de catarata em pacientes brasileiros. Métodos: Este estudo transversal de base clínica foi realizado no Hospital Federal de Bonsucesso, Rio de Janeiro, Brasil. Os prontuários de pacientes submetidos à cirurgia de catarata durante um per&i...
Source: Arquivos Brasileiros de Oftalmologia - Category: Opthalmology Source Type: research
Purpose: To evaluate the efficacy, predictability, and safety of combined corneal collagen cross-linking (CXL), intracorneal ring segment (ICRS) implantation, and superficial phototherapeutic keratectomy (PTK) in patients with keratoconus. Methods: Fifty-five eyes received ICRS implantation, followed by CXL and PTK combination treatment. Patients were followed up for 6 months. Primary outcomes included Logarithm of the Minimum Angle of Resolution (LogMAR) uncorrected distance VA (UDVA) and corrected distance VA (CDVA), sphere, cylinder, mean spherical equivalent, index of surface variance, index of vertical asymmetry,...
Source: Cornea - Category: Opthalmology Tags: Clinical Science Source Type: research
Publication date: Available online 4 September 2019Source: Progress in Retinal and Eye ResearchAuthor(s): Andri K. Riau, Yu-Chi Liu, Gary H.F. Yam, Jodhbir S. MehtaAbstractStromal keratophakia was first performed by José Ignacio Barraquer in the 1960s. The refractive lamellar keratoplasty technique was intensely pursued in the 1980s as a method to alter corneal refractive power. However, because sculpting of the donor stromal lenticule and lamellar keratectomy of the recipient's cornea were performed with a mechanical microkeratome, the quality of the cut was inconsistent. Consequently, the refractive outcomes of th...
Source: Progress in Retinal and Eye Research - Category: Opthalmology Source Type: research
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