Navegando por Palavras-chave "refractive surgery"
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- ItemSomente MetadadadosAnalysis of variability of corneal topographies among healthy patients in seven different devices(Universidade Federal de São Paulo (UNIFESP), 2014-11-29) Oliveira, Ramon Antunes de [UNIFESP]; Benicio, Claudia Maria Francesconi Benicio [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)Purpose: To compare corneal measurements of healthy patients among seven different topographies: IOL Master Zeiss Biometer, Wavelight Allegro Topolyzer, Allegro Oculyzer, Haag-streit Lenstar, CSO Corneal Topographer, Oculus Pentacam and Atlas Corneal Topography. Methods: Each subject was examined in all devices at a single visit. We compared the variability of corneal topographies (difference between the flat and the steep curvatures, and the comparison between the medium curvature among the devices). Agreement was assessed by Bland-Altmann statistics. Results: Keratometry of 31 eyes among all different devices were not significantly different (K1, K2 or Sim K). Besides that, corneal curvatures were slightly flatter in Lenstar than other devices (Fig 1). The devices were compared in pairs, and displayed in a 95% interval of confidence. Atlas and CSO had a variation of 0.20D ± 0.57 (Fig 2). IOL Master and Lenstar demonstrated a variation of 0.80D ± 0.23 (Fig 3). The difference was bigger as higher the curvature became. Atlas and Pentacam showed strong correlation 0.00D ± 0.50 (Fig 4). IOL Master and Atlas had a difference of 0.17D ± 0.36 (Fig 5). IOL Master and Pentacam showed good correlation of 0.17D ± 0.28 (Fig 6). Lenstar and CSO were the two devices with higher difference among all of them: 0.84D ± 0.59 (Fig 7). Conclusion: The accuracy of keratometry measurements among all devices had a strong correlation (< 1D) for optical biometers, placido disk or scheimpflug-based devices. The keratometry obtained with Lenstar tended to hypoestimate the sim K in 0.85 D. Although these results were not statiscally different, it could be clinically significant.
- ItemSomente MetadadadosApplication of corneal tomography before keratorefractive procedure for laser vision correction(Wiley-V C H Verlag Gmbh, 2016) Luz, Allan [UNIFESP]; Lopes, Bernardo [UNIFESP]; Salomao, Marcela; Ambrosio, Renato [UNIFESP]Ectasia after refractive surgery represents a major concern among refractive surgeons. Corneal abnormalities and preexisting corneal ectasia are the most important risk factors. Corneal topography and central corneal thickness are the factors traditionally screening for in refractive surgery candidates. Study of the anterior surface by Placido topography allows for identification of keratoconus before biomicroscopy. However, this is insufficient for the evaluation of pre-operative refractive surgery. There are cases of ectasia after laser in situ keratomilusis (LASIK) without identifiable risk factors such that there is a need to go beyond the corneal surface. A key requirement is quantifying susceptibility to corneal biomechanical instability and progression to ectasia. Tomographic indices derived from elevation maps and pachymetry spatial variation produce a Belin Ambrosio display final D index (BAD-D index), which has shown better results compared to surface curvature indices for detecting very mild forms of ectasia. A logistic regression formula, integrating age, residual stromal bed, and BAD-D (Ectasia Susceptibility Score, ESS) resulted in a significant improvement in accuracy, leading to 100% sensitivity and 94% specificity for detecting susceptible cases. A comprehensive corneal structural analysis based on corneal segmental tomography can detect susceptible corneas, which increases safety for refractive surgery patients. [GRAPHICS] .
- ItemSomente MetadadadosPhotorefractive Keratectomy With Mitomycin C After Penetrating and Lamellar Keratoplasty(Lippincott Williams & Wilkins, 2010-10-01) Forseto, Adriana dos Santos; Marques, Junia Cabral; Nose, Walton [UNIFESP]; Eye Clin Day Hosp; Universidade Federal de São Paulo (UNIFESP)Purpose: To assess the safety and efficacy of photorefractive keratectomy with mitomycin C (PRK-MMC) to correct refractive errors after corneal transplantation.Methods: This was a prospective and noncomparative study of 36 eyes that underwent PRK-MMC after penetrating (n = 34) or lamellar (n = 2) keratoplasty. After mechanical epithelial removal and photoablation, a sponge with mitomycin C 0.02% was applied to the stromal bed for 1 minute. the uncorrected and best-corrected visual acuities, refraction, and complications were assessed.Results: the average follow-up was 16.27 +/- 8.38 months (range, 6-30.5 months). the spherical equivalent decreased from -3.95 +/- 4.11 to -1.07 +/- 1.45 diopters (D) postoperatively (P < 0.001). the mean preoperative astigmatism was 4.42 +/- 1.69 D (range, 1.00-7.25 D); however, surgical correction was limited to 6.00 D. Vector analysis of astigmatic correction showed an index of success of 55%. At the last follow-up, 41.7% (n = 15) and 61.1% (n = 22) of the eyes were within +/- 0.50 and +/- 1.00 D of emmetropia, respectively. Nineteen eyes (52.8%) achieved an uncorrected visual acuity of 20/40 or better. the best-corrected visual acuity remained within 1 line of the preoperative values in 26 cases (72.2%), improved in 8 (22.2%), and decreased in 2 (5.6%). Endothelial cell decompensation was observed in 1 eye (2.8%) 11 months postoperatively, and haze developed in 3 cases (8.3%).Conclusions: PRK-MMC may be an option to correct refractive errors after keratoplasty. A low preoperative endothelial cell count and haze may affect the safety outcomes.
- ItemSomente MetadadadosRole of the corneal epithelium measurements in keratorefractive surgery(Lippincott Williams & Wilkins, 2017) Salomao, Marcella Q. [UNIFESP]; Hofling-Lima, Ana Luisa [UNIFESP]; Lopes, Bernardo T. [UNIFESP]; Canedo, Ana Laura C.; Dawson, Daniel G.; Carneiro-Freitas, Rui; Ambrosio, Renato, Jr. [UNIFESP]Purpose of review Refractive surgery has stimulated considerable progress in corneal and anterior segment imaging, and optical characterization of the eye. From front surface corneal topography, we evolved to three-dimensional corneal tomography with limbus to limbus characterization of the front and back corneal surfaces and pachymetric mapping. Corneal anatomical evaluation has further evolved to layered or segmental tomography with the ability to characterize corneal epithelial thickness profile and the elevation of stromal front surface. Further characterization of even more specific structures, such as Bowman's layer and Descement's membrane, has been also demonstrated. The applications of such understanding in keratorefractive surgery are reviewed. Recent findings Understanding the corneal epithelial profile is of interest in many areas of ophthalmology, especially in refractive surgery. The most relevant applications include screening candidates at higher risk for complications (i.e. progressive ectasia and tear dysfunction syndrome), planning primary procedures, enhancements, and therapeutic surgery, and also postoperatively understanding the wound healing and clinical outcomes. Summary Corneal epithelial thickness was first available using digital very-high-frequency ultrasound. Advances in anterior segment optical coherence tomography enabled such fundamental evaluation, which accelerated progress. Such knowledge significantly impacts safety and efficacy of refractive surgery, and also allows for significant improvement for therapeutic procedures.
- ItemSomente MetadadadosScheimpflug imaging for laser refractive surgery(Lippincott Williams & Wilkins, 2013-07-01) Ambrosio, Renato [UNIFESP]; Valbon, Bruno F.; Faria-Correia, Fernando; Ramos, Isaac; Luz, Allan [UNIFESP]; Inst Olhos Renato Ambrosio & Visare RIO; Rio de Janeiro Corneal Tomog & Biomech Study Grp; Universidade Federal de São Paulo (UNIFESP); Universidade de São Paulo (USP); Ctr Hosp Sao Joao; Hosp Santa Luzia; Hosp Olhos SerjipePurpose of reviewTo review the principles and clinical applications of Scheimpflug corneal and anterior segment imaging with special relevance for laser refractive surgery.Recent findingsComputerized Scheimpflug imaging has been used for corneal and anterior segment tomography (CASTm) in different commercially available instruments. Such approach computes the three-dimensional image of the cornea and anterior segment, enabling the characterization of elevation and curvature of the front and back surfaces of the cornea, pachymetric mapping, calculation of the total corneal refractive power and anterior segment biometry. CASTm represents a major evolution for corneal and anterior segment analysis, beyond front surface corneal topography and single point central corneal thickness measurements. This approach enhances the diagnostic abilities for screening ectasia risk as well as for planning, evaluating the results, managing complications of refractive procedures, and selecting intraocular lens power, type, and design. in addition, dynamic Scheimpflug imaging has been recently introduced for in-vivo corneal biomechanical measurements and has also been used for anterior segment imaging of femtocataract surgery.SummaryScheimpflug imaging has an important role for laser refractive surgery with different applications, which continuously improve due to advances in technology.