Vector analysis of astigmatism changes by flattening, steepening, and torque

Abstract

When treatment is applied off one of the four primary axes, the treating vector can be resolved into its component parts of flattening, steepening, and torque. Analyzing changes in this way provides a uniform means of assessing astigmatic changes for all types of cataract and refractive surgery and quantifies the flattening effect when treatment is applied off the intended meridian.

JRS Standard for Reporting Astigmatism Outcomes of Refractive Surgery

“…In 2006, an attempt to address the question of a minimum standard format for reporting astigmatic outcomes was proposed by the Astigmatism Reporting Astigmatism Outcomes/Reinstein et al Project Group of the American National Standards Institute (ANSI), and their report was published in this Journal, 15 albeit without peer-review on the basis that the article was a completed formal document from ANSI and that the content was the final report from the project's group. 16 The majority of the astigmatism analysis methods included in the ANSI article were directly adapted from the methods developed and originally published by Alpins in 1993, 9,17,18 in many instances with simple renaming of the original terminology. Although this was highlighted at the time in correspondence to the Editor, 19 the altered terminology has been used subsequently in many publications reporting astigmatism.…”

“…20 Our position at the Journal is that all future reports of astigmatism should adhere to the original terminology as described by Alpins. 9,17,18 There are three reasons for this, and the guiding principle is clarity in communication above all else. The Alpins terminology has been in use for more than 20 years and had been in use for 13 years prior to the ANSI article, 15 and so had already become widely used in the field within hundreds of publications.…”

“…It is an easy mistake to make; we have been guilty of doing exactly this, for example when we cited the ANSI article 15 in our editorial on updating the Standard Graphs in 2009. 4 Finally, and most important, our analysis finds the terminology in the original Alpins articles 9,17,18 to be superior by taking into account the strict mathematical and semantic context for the specific task of describing astigmatic vector changes in the ophthalmological domain. For clarity and reference, we have set out in Table 1 the original Alpins Method terms alongside the ANSI altered terms together with the reasoning behind the preference of adhering to the original terminology.…”

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

“…(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);…”

Surgically Induced Astigmatism Assessment

“…The flattening is the parameter that reduces the astigmatism; the torque "is the ineffective component of the SIA vector that does not reduce the astigmatism at the surgical meridian but changes the orientation of the astigmatism." 3,4 The torque component of the SIA should take no part in the calculation of the toric power calculation of an intraocular lens, leaving the flattening effect as the relevant parameter for incisional effect.…”