Purpose To compare the effect of a rotating microkeratome (M2) and a linear microkeratome (SBK) on the change in the astigmatic component in eyes with preoperative plano refractive cylinder. Setting University Medical Centre Hamburg-Eppendorf, Hamburg, Germany. Design Retrospective case series. Methods An Allegretto excimer laser was used to perform laser ablation in myopic eyes of consecutive patients. The laser in situ keratomileusis (LASIK) procedure included mechanical flap preparation using a microkeratome, either a linear type with a single-use 90 μm head to create a nasal hinge or a rotating type with a single-use 90 μm head to create a superior hinge. The Alpins vector method was applied to describe the effects of LASIK on postoperative refractive cylinder. Results The study evaluated 1045 eyes of 852 patients. Although the mean overall efficacy and safety indices indicate the procedure was highly precise, safe, and efficient, there were statistically significant differences in surgically induced astigmatism (SIA) between the microkeratomes (P = .002). The postoperative refractive cylinder (ie, SIA) was 0.75 diopter (D) or more in 116 eyes (11.1%), 44 (12.8%) of 344 linear cases and 72 (10.3%) of 701 rotating cases. Independent of the type of microkeratome used, the SIA was slightly higher in eyes treated first; the mean magnitude of the induced astigmatism was 0.35 D. Conclusions In approximately 10% of eyes with preoperative plano refractive myopia, the astigmatic component tended to be overcorrected. Nevertheless, independent of the type of microkeratome, the maximum mean magnitude of refractive cylinder documented was 0.35 D. Financial Disclosure No author has a financial or proprietary interest in any material or method mentioned.
Purpose To examine the prevalence and associations of anisometropia with spherical ametropia, cylindrical power, age, and sex. Methods Anisometropia was analyzed for subjective refraction. In total, 134,603 refractive surgery candidates were included in the period from 2010 to 2020 at the CARE Vision Refractive Centers in Germany. Our study was approved by the local ethics committee at the University in Duesseldorf (approval date: February 9, 2021) and conducted according to the tenets of the Declaration of Helsinki and Good Clinical Practices Guidelines. The treatment contract included explicit patient consent to use medical data for scientific purposes. Correlations between anisometropia and explanatory variables were analyzed using the chi-squared test ( χ 2 test), nonparametric Kruskal–Wallis or Mann–Whitney U-tests, and binomial logistic regression. Power vector analysis was applied for further analysis of cylindrical power. Results The median level of anisometropia (A subj ) in the whole population was 0.38 D. The prevalence of A subj was 17.9%. In hyperopes, all explanatory variables (spherical ametropia, cylindrical power, age, sex) were independently associated with anisometropia. A subj decreased with increasing cylindrical ametropia: an increase in cylindrical power by 7.8 D reduced the chance of observing anisometropia by half. It was also associated with male sex. A subj decreased by half with a 16.7 D increase in spherical power and an increase in age by 22.7 years. In myopes, cylindrical power was most strongly associated with anisometropia: an increase in (negative) cylindrical power by 2.15 D doubled the chances of observing anisometropia in myopes. In addition, advancing age (double chance with an increase of 38.3 years), increasing spherical power (double chance with an increase of 8.15 D), and female sex correlated positively with increasing anisometropia in myopes. Conclusions This retrospective analysis gives evidence for the independent association between anisometropia and spherical power, cylindrical power, age, and sex in myopic refractive surgery candidates. The relation of anisometropia with age was positive in myopes but negative in hyperopes. The analysis of sex revealed a positive relation of female sex and anisometropia in myopes and furthermore revealed a positive relation of male sex and anisometropia in hyperopes. Further clinical research into the underlying mechanisms behind our findings is indicated.
This article is concerned with the effects of policies on the Tatar alphabet in the 1920’s on the cultural memory of the Tatars. It begins with a discussion of the concept of cultural memory as developed by the German Egyptologist Jan Assmann. A short chronological introduction to the history of Tatar alphabet policy in the 1920’s follows. This introduction describes the main events that lead to the replacement of the Arab-based alphabet, used by Tatars for centuries, by the Latin script. The article treats several aspects of the relations between the reform in alphabets and cultural memory. Areas examined include cultural and religious memory (i.e., exactly which cultural memories were attacked and who tried to defend which aspects of memory); issues of canon and censorship (how to intentionally change the cultural memory of a given group of people and the instruments of creating cultural memory); and issues of ethnic identity and script, which analyzes the effects of memory politics in the context of the creating of new group identities. This last section specifically deals with the creation of a Tatar nation in place of a pan-Islamic or pan-Turkic identity. As a whole, the article serves two purposes. First, it scrutinizes the reform of the Tatar alphabet in order to criticize superficial judgments of that policy. Second, the paper bases its concept of cultural memory on methodological individualism and thereby demonstrates that cultural memory is not a given recollection, but always object of strategic, intentional action.
Between Economics and History: A Plea for Dialog between Political History and Empirical-Analytical Political Science?. The following essay is intended to con tribute to discussion about new orientations in political history going on in German historiography. Instead of opt ing for either traditional political history or new cultural his tory of the political, it is intended to show that a denser cooperation with political scientists might be a more proper approach to find new ways of talking about politics in his tory. The most successful theory of action in political science, Rational Choice research program, is presented as a powerful theoretical foundation for talking about dis courses, symbols and institutions; moreover, its use would enable historians to integrate insights from new institutional economics and political economy into historical research.
To improve keratoconus (KC) screening with new in vivo biomechanical Scheimpflug analyses.After adjusting for intraocular pressure and corneal thickness, predefined static and new dynamic Scheimpflug curve analyses [Pentacam HR and Corvis ST (CST); Oculus] of 87 normal eyes, 27 subclinical KC eyes, 42 suspected KC, and 65 manifest KC eyes were reviewed retrospectively. A t test (for a normal distribution), Wilcoxon matched-pairs test (if not normally distributed), and receiver operating characteristics were used to test for statistically significant differences between these groups. In addition, new dynamic curve analyses were performed to analyze corneal dynamics throughout the entire response to the CST air puff impulse.Comparing normal and KC-suspect eyes, the parameters A1 length, A2 length, radius of the inward-bended cornea, and deflection length at the highest concavity revealed statistically significant differences. In addition, the newly calculated "applanation length level" and "deflection length level" demonstrated consistently increasing differences with increasing statistical significance between normal eyes and those with advancing KC stages. However, when comparing normal and subclinical KC eyes, none of the analyzed parameters demonstrated statistically significant differences.In vivo biomechanical analyses (CST) at their current state only marginally improve KC screening protocols. Newly generated parameters such as the applanation length level and deflection length level might further improve early KC screening.
