the more study: manifest vs. online refraction evaluation

Conditions: Refraction Error; Myopia; Astigmatism

Summary: the assessment of the refractive state of the eye is a fundamental and important part of ophthalmic and optometric clinical practice. the development of an unsupervised online subjective refraction method makes a refraction more accessible and can be quite cost-saving. in this study, the investigators want to validate an online refraction method which was recently created in the netherlands. the study comprises two different set of participants: part one contains fifty healthy volunteers, 18-40 years of age, with a refractive error and no other ophthalmic pathology. part two contains fifty patients with an ophthalmic pathology. the online refraction outcomes will be compared to a manifest refraction and automated refraction in a cross-sectional study design.

uncorrected refractive errors cause significant economic implications in both high and low income countries in terms of the loss of potential productivity (williams et al. (2015)). the prevalence of uncorrected refractive errors is, despite of the available clinical services, still huge; visual impairment is in 42 percent of the cases the result of an uncorrected refractive error worldwide (williams et al. (2015)). even in high income countries, this issue remains prevalent. therefore, the access to the available clinical services has to be simplified. the development of an online refraction method will make a refraction more accessible for patients and can be cost-saving. clinicians can easily take an online method to places where it's needed for example in low income countries. there are several methods to measure a refractive error. the 'golden standard' to prescribe spectacles is a manifest refraction (thibos, hong, bradley \& applegate (2004)). this method was already described by f.c. donders in 1864 and is performed with trial lenses and a visual acuity chart to measure the refraction error (donders (1864)). an automated refraction is a quick routine machine based assessment, mainly used as a starting point for a manifest refraction and is based on retinoscopy (nissman et al., (2004)). at the moment, several online refraction methods are available. however, these methods are not scientifically validated, unavailable outside the united states of america (usa) or not designed for customers. one of these online refraction methods is opternative (opternative (2017)). opternative is currently used in the usa and is still developing (opternative (2017)). it's a self-directed online refraction method using a computer-based response to presented stimuli with the use of a smartphone and a computer. another method is eyenetra (eyenetra (2017) \& ohlendorf, leube \& wahl (2016)). the use of this method is limited due to the need of special equipment such as a portable autorefractor, an autolensometer and a phoropter. therefore, eyenetra is mainly designed for optometrists and ophthalmologists for low-income populations. the same applies to svone; this method uses a hartmann-shack wavefront aberrometer which the user can attach to a smartphone (ohlendorf, leube \& wahl (2016)). other online refraction methods are 6over6, but this method has not been released yet (6over6, (2017)), and warby parker (warby parker, (2017)). there are also online visual acuity tests to measure the visual acuity only. the mobile devices to test the visual acuity are peekvision, 6over6, opternative, eyenetra and digisight (ludwig et al., (2016)). currently, digitalization is affecting our way of life. technology can be used to design products to easily determine if someone has a refractive error. this can, in the future, solve a big part of the problem of uncorrected refractive errors and the leading cause of blindness worldwide. the aim of this study is to validate a recently created online refraction method by comparing the outcomes of the online refraction method with the 'golden standard' manifest refraction.

Eligibility criteria:
inclusion criteria: 1. group one: * age: 18-40 years * master the dutch language * capable to perform the tests adequately. 2. group two: * age: 18-40 years * master the dutch language * capable to perform the tests adequately. * diagnosis of keratoconus. exclusion criteria: 1. group one: * no informed consent * diabetes * pregnancy or lactation * high hyperopia/myopia (\>6d) * an ophthalmic history besides ametropia 2. group two: * no informed consent * diabetes * pregnancy or lactation * high hyperopia/myopia (\>6d)

Keywords: myopia astigmatism online assessment refractive error