The Progression of Nearwork Myopia

Non-contact tonometry: predicting intraocular pressure using a material-corneal thickness-independent methodology

Introduction: Glaucoma, a leading cause of blindness worldwide, is primarily caused by elevated intraocular pressure (IOP). Accurate and reliable IOP measurements are the key to diagnose the pathology in time and to provide for effective treatment strategies. The currently available methods for measuring IOP include contact and non contact tonometers (NCT), which estimate IOP based on the corneal deformation caused by an external load, that in the case of NCT is an air pulse. The deformation of the cornea during the tonometry is the result of the coupling between the IOP, the mechanical properties of the corneal tissue, the corneal thickness, and the external force applied. Therefore, there is the need to decouple the four contributions to estimate the IOP more reliably. Methods: This paper aims to propose a new methodology to estimate the IOP based on the analysis of the mechanical work performed by the air jet and by the IOP during the NCT test. A numerical eye model is presented, initially deformed by the action of a falling mass to study the energy balance. Subsequently, Fluid-Structure Interaction (FSI) simulations are conducted to simulate the action of Corvis ST. Results and discussion: The new IOP estimation procedure is proposed based on the results of the simulations. The methodology is centred on the analysis of the time of maximum apex velocity rather than the point of first applanation leading to a new IOP estimation not influenced by the geometrical and mechanical corneal factors.

Risk factors and association with severity of keratoconus: the Australian study of Keratoconus

SIGNIFICANCE

Our results show that asthmatic patients tend to have more severe KC and thus close monitoring for disease progression would be advised, and appropriate treatment strategies may be actioned stabilise the condition that may reduce the need for future corneal transplantation.

PURPOSE

To explore a wide range of risk factors associated with the severity of keratoconus (KC).

METHODS

A cross-sectional study of KC patients was undertaken in Melbourne, Australia. A questionnaire addressing age, gender, educational background, ocular and medical history, smoking and alcohol consumption, and physical examination comprising anthropometric measurements was collected; eye examination was undertaken. The associations between a range of risk factors and the severity of KC were determined using univariate and multivariable linear regression analyses.

RESULTS

A total of 260 KC subjects were included in this study. Mean age of subject was 35.5 (SD = 14.8) years and the majority of the subjects were European 171 (68.2%). Initial univariate regression analysis identified the following risk factors at the p < 0.1 level with KC: higher body mass index, smoking cigarettes, diabetes, rheumatoid arthritis and asthma were associated with increased severity of KC, whereas eczema was associated with less severe KC. Following multivariable regression analysis, only asthma remained as a significant risk factor associated with 2.2 diopters (D) steeper average mean keratometry compared to KC subjects having no asthma [p = 0.03; β = 2.18; 95% confidence intervals: 1.22, 4.14].

CONCLUSION

Our study describes the comprehensive assessment of all the known risk factors in a large KC cohort recruited in Australia. Our study has reported asthma as the only risk factor found to be significantly associated with the severity of KC. The results of this study allow us to better understand the aetiology of KC and such knowledge could be useful in instigate systemic management of patients to slow or prevent KC.

REVIEW. +2 to +3 D. Reading Glasses to Prevent Myopia

Basic control theory equations are developed showing classical exponential system response of refraction vs. time R(t), with a characteristic system time constant, in response to a negative (-) step change of near work environmental conditions. Statistical analysis of retrospective data from 226 subjects is presented. It is shown that reasonable significance levels p < 0.001 can be obtained from relatively small sample sizes, over short time intervals. Details from preliminary experimental design using reading glasses at the U.S. Naval Academy at Annapolis are discussed. The conclusion is that positive (+) Add lenses, used as reading glasses during study, can prevent the development of myopia of college students in pilot training.