China
Africa
Explore chapters and articles related to this topic
Answers
Published in Ken Addley, MCQs, MEQs and OSPEs in Occupational Medicine, 2023
The screen height should be lower for users of bifocal lenses as they tend to look at the screen through the bottom half of the lens. Screen height should be between 0 and 30 degrees below eye level for most users. The most important determinant of head posture is the position of the visual target hence the importance of screen height.
Mrs Jones plus three: unpicking homeless children’s and families’ needs
Published in Panos Vostanis, Helping Children and Young People Who Experience Trauma, 2021
And this leads to another common misunderstanding. Adopting a holistic approach is not mutually exclusive with a specific agency role. This is like wearing bifocal lenses to look both afar and at short range at the same time. Child protection and domestic violence come top of the list, followed by risk-taking behaviours such as deliberate self-harm, alcohol and drug use, as these will inevitably cloud the rest. Enquiring about mothers’ and children’s emotional and physical well-being, support networks, developmental capacity and schooling, are all part of the same jigsaw.
Vision
Published in Nicholas Green, Steven Gaydos, Hutchison Ewan, Edward Nicol, Handbook of Aviation and Space Medicine, 2019
Nicholas Green, Steven Gaydos, Hutchison Ewan, Edward Nicol
Corrective flying spectacles: Must be suitably robust and integrate with flight equipment (e.g. helmet and mask).Spare pair should be carried in flight.Bifocal lenses permitted, but progressive power varifocal lens use limited due to edge distortion/blur risks.
Optical and pharmacological strategies of myopia control
Published in Clinical and Experimental Optometry, 2018
There are two categories of optical lens designs: concentric ring or bifocal lens design and progressive power or peripheral add lens design. Both designs impact the central and peripheral retinal images (Figure 2). The concentric ring lens design incorporates alternating distance correction and treatment (plus power) zones to provide two focal planes or simultaneous distance correction and retinal myopic defocus. The rationale behind this design is to provide good visual acuity while myopic defocus is simultaneously induced onto the retina during both distance and near viewing.2011 On the other hand, the progressive power lens design incorporates a gradual change in curvature to provide a central zone of distance correction with a progressive change to include a relative plus add in the periphery. This design aims to provide clear central vision while inducing peripheral myopic defocus during both distance and near viewing. Further details of various investigational lens designs reported in the literature are summarised in Table 1.
Double vision in adults
Published in Journal of Binocular Vision and Ocular Motility, 2018
Management of patients is primarily with prisms. Correction of diplopia in patients with divergence insufficiency begins with correcting full distance ET. Most patients with divergence insufficiency ET can fuse the full distance BO prism at near. However, some patients cannot tolerate BO prism at near without developing a near XT. In those patients, the bifocal can be nasally displaced to induce some BI prism at near, although this displacement is not possible with progressive lenses. Separate reading glasses with less or no prism may be helpful in patients using progressive lenses. A BI Fresnel prism over one bifocal or occlusion of a bifocal lens may be necessary.
Tear film stability over a myopia control contact lens compared to a monofocal design
Published in Clinical and Experimental Optometry, 2022
José Vicente García-Marqués, Rute Macedo-de-Araújo, Daniela Lopes-Ferreira, Alejandro Cerviño, Santiago García-Lázaro, José Manuel González-Méijome
This study has some limitations to consider. First, results were obtained in young adults, while the target population for the dual-focus contact lens is young children and adolescents, or presbyopic patients wearing contact lenses with similar designs (bifocal lenses). Therefore, the present results cannot be directly extrapolated to those populations. Although visual analogue scales have been extensively used, employment of a standardised questionnaire would have also been interesting. Nevertheless, a visual analogue scale was used to differentiate between general, physic, and visual comfort.