Search results for "ACCOMMODATION"

Implantable collamer lens and femtosecond laser for myopia: comparison using an adaptive optics visual simulator.

2014

Purpose: To compare optical and visual quality of implantable collamer lens (ICL) implantation and femtosecond laser in situ keratomileusis (F-LASIK) for myopia. Methods: The CRX1 adaptive optics visual simulator (Imagine Eyes, Orsay, France) was used to simulate the wavefront aberration pattern after the two surgical procedures for -3-diopter (D) and -6-D myopia. Visual acuity at different contrasts and contrast sensitivities at 10, 20, and 25 cycles/degree (cpd) were measured for 3-mm and 5-mm pupils. The modulation transfer function (MTF) and point spread function (PSF) were calculated for 5-mm pupils. Results: F-LASIK MTF was worse than ICL MTF, which was close to diffraction-limited MT…

Measuring Seasonality: Performance of Accommodation Establishments in Sicily through the analysis of Occupancy Rates

2011

Tourism, more than other fields, needs to be managed. As such, the provision of reliable information and adequate tools is one of the major challenges to monitor and to manage tourism destinations. Sicily (Italy) seems to have a great potential coming from its tourism resources, and most of the recent development programs have been focused on tourism. In line with the world’s trend, tourism in Sicily faced a growth in terms of overnight stays, from about 9 millions in 1994, to more than 14 millions in 2007. The regional expenditure in tourism from 1996 to 2006 was of euro 785 millions (Federalberghi, 2007), which ranks Sicily as the second region in Italy for tourism expenditure, in the yea…

Smartphone viewing distance during active or passive tasks and relation to heterophoria

2019

Our aim was to analyze viewing distance for smartphone users (aged 18-45 y.) in terms of passive or active task, relation to heterophoria, type of refractive error and smartphone font size. Participants were asked to read out loud text message (passive task) and afterwards rewrite the same text and send back (active task). For the text message we used sentence consisting of 23 words and 200 characters (with spaces). Participants used their own smartphones (font size monitored). For both passive and active task we measured task time and viewing distance at the end of the task. We found significantly shorter viewing distance for digital active task compared to passive task (29.3 ± 4.7 and 32.…

The effect of fractal contact lenses on peripheral refraction in myopic model eyes.

2014

Purpose: To test multizone contact lenses in model eyes: Fractal Contact Lenses (FCLs), designed to induce myopic peripheral refractive error (PRE). Methods: Zemax ray-tracing software was employed to simulate myopic and accommodation-dependent model eyes fitted with FCLs. PRE, defined in terms of mean sphere M and 90–180 astigmatism J180, was computed at different peripheral positions, ranging from 0 to 35 in steps of 5, and for different pupil diameters (PDs). Simulated visual performance and changes in the PRE were also analyzed for contact lens decentration and model eye accommodation. For comparison purposes, the same simulations were performed with another commercially available conta…

The stenopaeic slit: an analytical expression to quantify its optical effects in front of an astigmatic eye.

2001

The stenopaeic slit is a trial case accessory used in subjective refraction, especially when high astigmatism is present. In spite of its simplicity, the effect of the slit when it is not oriented along one of the principal meridians of the examined eye is difficult to predict, even in terms of classical geometrical optics. In this paper, the optical principles of the slit are considered with full details in the theoretical framework of the dioptric power space. An analytical expression to obtain the residual refractive error when a stenopaeic slit is placed in front of an astigmatic eye at any orientation is deduced. In the light of these results, some aspects of the clinical procedure are…

The overall classification of residential buildings: Possible role of tourist EU Ecolabel award scheme

2012

Abstract The debate on the environmental performance of buildings and their classification is continuously rising and deeply involves all actors of the sector, from researchers to technicians and from owners to real estate managers. In the field, the EU has created a panel that is currently working on defining the criteria for attributing an Ecolabel award to a building. However, despite the enormous efforts made by administrative and academic institutions, a suitable and widely available scheme for operators to assess the environmental performance of a building is far from being established. To help provide a solution to the problem, the possibility of adopting the EU Ecolabel scheme estab…

Seasonal pattern and amplitude: a logical framework to analyse seasonality in tourism. An application to bed occupancy in Sicilian hotels

2011

Many studies have investigated seasonality in tourism in terms of its causes and impacts, from both theoretical and applied perspectives. However, the definition of seasonality and, most of all, its application and measurement have not received the same degree of attention. In recognizing that seasonality has two main facets – pattern and amplitude – this paper critically examines the main seasonality measures proposed in the tourism literature, classifying them according to their properties and their most appropriate use. The framework then proposed is used to analyse a standard and comparable efficiency measure, such as the bed occupancy rate of Sicilian accommodation establishments, pla…

Unobserved tourism

2015

Having more reliable statistics is essential for policy-makers to be able to make effective decisions. Nevertheless, measuring the number of tourists in a given destination is not an easy task. After reviewing the main problems affecting official statistics on tourism, this paper proposes a general framework by formalizing a theoretical model in which tourism nights and trips in a given destination are broken down into observed and unobserved components, according to the European system of tourism statistics. The main approaches related to the measurement of unobserved tourism are discussed, and some empirical findings in Sicily (Italy) are presented in order to highlight the actual magnitu…

Unobserved Tourism and Observable On-line Tourism Accommodation Supply

2013

Influencia de los diferentes tipos de astigmatismo en la agudeza visual

2017

[EN] Purpose To investigate the change in visual acuity (VA) produced by different types of astigmatism (on the basis of the refractive power and position of the principal meridians) on normal accommodating eyes. Methods The lens induced method was employed to simulate a set of 28 astigmatic blur conditions on different healthy emmetropic eyes. Additionally, 24 values of spherical defocus were also simulated on the same eyes for comparison. VA was measured in each case and the results, expressed in logMAR units, were represented against of the modulus of the dioptric power vector (blur strength). Results LogMAR VA varies in a linear fashion with increasing astigmatic blur, being the slope o…