Practical astigmatism analysis for refractive outcomes in cataract and refractive surgery

Alpins, Noel; Goggin, Michael

doi:10.1016/j.survophthal.2003.10.010

Cited by 164 publications

(106 citation statements)

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“…(1,2,3,4) Tais artigos forneceram informações sobre os motivos da análise vetorial (1,2,7,8,9,11,13,14) ou ressaltaram a sua importância clínica. (3,4,6,10,12) DISCUSSÃO O método proposto por Thibos e colaboradores aborda o astigmatismo ceratométrico, incluindo qualquer eventual componente esférico presente, na forma vetorial retangular, como a seguir: (3,13,14) • Média da leitura ceratométrica (M);…”

Section: Resultsunclassified

“…(11) As várias relações entre esses vetores fornecem parâmetros objetivos para avaliar se o tratamento está no eixo ou fora dele, se o tratamento foi demasiado ou insuficiente e se os ajustes necessários foram feitos, caso a correção de astigmatismo tenha sido repetida. (1,7,11) Entre esses parâmetros, alguns dos mais amplamente utilizados estão listados abaixo: (1,11) • Índice de Correção (IC): Calculado determinando-se a relação do SIA com o TIA (o que a cirurgia realmente induz versus o que a cirurgia pretendia induzir). Essa relação é calculada dividindo-se o SIA (efeito real) pelo TIA (efeito-alvo).…”

Section: Resultsunclassified

“…O astigmatismo, definido por uma força cilíndrica e um eixo (refrativo), ou por uma magnitude e um meridiano (corneano), encaixa-se nesta descrição. (1) Tanto o astigmatismo quanto os vetores astigmáticos empregam as mesmas unidades de medida: dioptrias e graus; porém, o astigmatismo é uma entidade mensurável, enquanto vetores só podem ser calculados (2) Uma análise precisa e completa do astigmatismo deve levar em conta o seu caráter vetorial (3) por isto, a análise baseada em vetores tem sido amplamente utilizada na literatura. (2,4,5) O objetivo do presente estudo foi fazer uma revisão sistemática da literatura sobre a justificativa da análise vetorial do astigmatismo.…”

Section: Introductionunclassified

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Vector analysis of astigmatism according to the methods of Alpins and Thibos: a systematic review

2016

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RESUMOObjetivo: Apesar de a análise vetorial ser amplamente utilizada na literatura, tanto para a descrição de características, como na análise de mudanças no astigmatismo, poucos são os artigos que apresentam a racionalidade do método. Em nossa revisão, apresentamos os pontos mais importantes dos métodos propostos por Alpins e por Thibos. Métodos: O Pubmed foi pesquisado, em 29 de junho de 2016, para artigos em inglês, com resumo, empregando-se os termos (astigmatism) AND (vector analysis) AND (Alpins) OR (Thibos), independentemente da data ou tipo de publicação. Resultados: Treze artigos, de 228 referências, foram incluídos em nossa revisão. Conclusões: O método proposto por Thibos é o mais apropriado para descrições objetivas do astigmatismo. O método de Alpins, por outro lado, é o mais indicado para análises referentes a mudanças no astigmatismo. ABSTRACTAim: Although much has been published on vector-based analysis of astigmatism, the reason why vectors precisely describe astigmatism features, or even changes in its characteristics, has been discussed only on a few articles. Our review intends to highlight the essential features of both methods proposed by Alpins and Thibos. Methods: Pubmed was searched for papers in English, containing abstracts, on June 29th 2016 for (astigmatism) AND (vector analysis) AND (Alpins) OR (Thibos), regardless of the date of publication or the study design. Results: Thirteen papers, out of 228 references, were included in our review. Conclusions: The method proposed by Thibos is suitable whenever an objective description of astigmatism is aimed. However, the method proposed by Alpins may provide detailed information on the assessment of changes in astigmatism. RESUMENObjetivo: A pesar del análisis vectorial ser ampliamente utilizado en la literatura, tanto para la descripción de características como en el análisis de cambios en el astigmatismo, son escasos los artículos que presentan la racionalidad del método. En nuestra revisión, presentamos los puntos más importantes de los métodos propuestos por Alpins y por Thibos. Métodos: Se ha revisado Pubmed el 29 de junio de 2016 para artículos en inglés, con resumen, empleándose los términos (astigmatism) AND (vector analysis) AND (Alpins) OR (Thibos), independientemente de la fecha o tipo de publicación. Resultados: Se incluyeron trece artículos de 228 referencias en nuestra revisión. Conclusiones: El método propuesto por Thibos es el más apropiado para descripciones objetivas del astigmatismo. El método de Alpins, por otro lado, es el más indicado para análisis concernientes a cambios en el astigmatismo.Como citar: Freitas GO, Ambrósio Jr R, Alves MR. Vector analysis of astigmatism according to the methods of alpins and thibos: a systematic review. e-Oftalmo.CBO: Rev Dig Oftalmol. 2016;2(3):1-6. http://dx

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Section: Resultsunclassified

Section: Introductionunclassified

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Vector analysis of astigmatism according to the methods of Alpins and Thibos: a systematic review

2016

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“…The average position of the dots is indicated by the centroid, which is analogous to the summated vector mean. 22 As Alpins and Goggin 22 point out, the summated vector mean can be used to identify a trend in aggregate data. The closer the summated vector mean or centroid is to zero, the more likely it is that the individual vectors indicate random events.…”

Section: Repeatabilitymentioning

confidence: 99%

Evaluation of Keratometry With a Novel Color-LED Corneal Topographer

Klijn¹,

Reus²,

Sicam³

2015

J Refract Surg

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good refractive outcome in cataract and refractive surgery relies on accurate and precise keratometry, particularly in procedures to correct astigmatism. Erroneous keratometric measurements may be a source of intraocular lens (IOL) power calculation errors, 1,2 which lead to postoperative refractive surprises. In addition, appropriate measurement of cylinder axis is important in toric IOL implantation because every degree of misalignment reduces the corrective effect. 3,4The manual Javal-Schiøtz keratometer, invented in the late 19th century, has largely given way to a variety of automated keratometers. These devices employ different techniques to provide automated analogues of traditional, manual keratometry readings. Commonly used keratometers are based on reflections of Placido rings, reflections of monochromatic lightemitting diodes (LEDs), Scheimpflug images, or a combination of these. Although of proven clinical value, topography based on Placido rings holds the disadvantage of neglecting skew rays, 5 which may lead to inaccuracies in measuring features of the cornea that are not rotationally symmetric (eg, corneal cylinder). [6][7][8] This may be solved by using a corneal reflection source that allows for point-to-point reconstruction.9,10 Simulations have shown that such a technique might be more accurate and precise than topography based on Placido rings. METHODS: Sixty-three eyes of 63 patients with virgin corneas underwent keratometry with color-LED corneal topography (Cassini; i-Optics, The Hague, The Netherlands) and with devices based on Placido ring reflections (Keratron; Optikon, Rome, Italy), monochromatic LED reflections (Lenstar; Haag-Streit, Koeniz, Switzerland), and Scheimpflug imaging (Pentacam; Oculus Optikgeräte, Wetzlar, Germany). Three repeated measurements were performed with each device. Comparability and repeatability of corneal power and cylinder measurements were assessed. The Bonferroni-corrected α-threshold for statistical significance was 0.016. RESULTS:Corneal power measurements with the Cassini topographer were not statistically significantly different from those with the Pentacam (P = .64). They were statistically significantly lower than those with the Keratron and Lenstar (P < .01), but the differences were of negligible clinical relevance. Cylinder measurements with the Cassini topographer were not statistically significantly different from those with any other device (P = .46). Repeatability of Cassini corneal power measurements was not statistically significantly different from that of the Keratron (P = .02), but was statistically significantly lower than that of the Lenstar and Pentacam (P < .001). Repeatability of Cassini cylinder measurements was statistically significantly higher than that of the Pentacam and Keratron (P < .001), but was not statistically significantly different from that of the Lenstar (P > .05). CONCLUSIONS:Corneal power and cylinder measurements with color-LED corneal topography yielded values that were comparable to those of other commonly used d...

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“…Alpins and coworkers (16)(17)(18)(19) use vector analysis to generate various indices to more fully describe astigmatic outcomes. Many of these indices, such as difference vector, index of success and coefficient of adjustment, provide remarkably useful and intuitive means of understanding the effects of the surgery.…”

Section: Astigmatism Analysismentioning

confidence: 99%

Astigmatism treatment during phacoemulsification: a review of current surgical strategies and their rationale

Freitas¹,

Boteon²,

Carvalho³

et al. 2013

Rev. bras.oftalmol.

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Practical astigmatism analysis for refractive outcomes in cataract and refractive surgery

Cited by 164 publications

References 40 publications

Vector analysis of astigmatism according to the methods of Alpins and Thibos: a systematic review

Vector analysis of astigmatism according to the methods of Alpins and Thibos: a systematic review

Evaluation of Keratometry With a Novel Color-LED Corneal Topographer

Astigmatism treatment during phacoemulsification: a review of current surgical strategies and their rationale

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