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Presbyopia and Progressive Powered Lenses.

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Reflection on the occupational dispense Visual defects are mostly caused by genetic factors or age-related diseases. There are three focusing states of the eye: emmetropia, hypermetropia and myopia. Also, presbyopia is a state of the eye that occurs when the eye is loosing the ability to focus on close up objects and it occurs on people after the age of 40 years due to the gradual and progressive age - related loss of accommodation. Referring to presbyopia, according to A Glasser (2010), presbyopia is the gradual and progressive age-related loss of accommodative amplitude. The progressive loss of accommodation begins early in life and culminates in a complete loss of accommodation by about 55 years of age. The exact mechanism of presbyopia are not known with certainty; the research evidence most strongly supports a loss of elasticity of the crystalline lens, although changes in the lens's curvature from continual growth and loss of power of the muscles that bend and straighten the crystalline lens (known as the ciliary muscles) have also been postulated as its cause. To help them correct their vision they can be advised to have Progressive Powered Lenses. A Progressive Powered Lens is, According to British Standard Institute (2003), " a special type of multifocal lens designed to provide correction for more than one viewing range and in which the power changes continuously rather than discretely". ...read more.


users and specific professions such as musicians, dentists and accountants. The patient is currently wearing this type of varifocal lenses at work and a new pair of spectacles was dispensed because the reading power has increased slightly. As the patient is an accountant and is a VDU user, working on the computer eight hours a day, an Ultra Clear coating was recommended to them. UltraClear coating is a thin colourless layer or multiple layers, applied by a vacuum - coating process. The UltraClear coating reduces the amount of light reflected off each surface of the lens and increases the light transmission. This coating is particularly important with the advent of flat - form aspheric lenses. As the aspheric lenses have quite flat back surfaces, without the UltraClear coating the patient would see reflections of everything behind them, including their own eyes. In conclusion, this coating is very good for the patient in question as they are getting an aspheric design of the lens. The next stage in the process of dispensing is to choose the frames to suit the lenses and also to suit the customer's features. The ophthalmic industry has, in the last twenty years in particular, concentrated on fashionable frames and lenses, and has adopted some of the principles of the fashion industry, particularly from hairdressing. ...read more.


The lenses are to be ordered according to the fitting heights. As mentioned above, the distance between the pupils is to be checked as well. This is to ensure that the patient is looking through the optical centre of the lens and is not having any prismatic effects. The prismatic effect is the deviation of a ray passing through a specified point on a lens. In the optical centre of a lens the light passes through undeviated, therefore there is no prismatic effect. The optical centre is measured with the aid of a pupillometer and by placing it in front of the patient's eye and aligning the lines on the pupillometer with the centre of the customer's pupils. However, people have different measurements for right and left pupil distance as the eyes are not perfectly symmetrical. Finally, a special attention needs to be given to the patients on collection of their spectacles. At the collection the patient's spectacles were checked again to make sure that the lenses were glazed according to the measurements taken. Also, the patient was advised to clean the glasses with a cleaning cloth which was provided and to use and keep the spectacles at work. The patient was advised not to use them for driving, not to put the spectacles on the table and not to put them with the lenses facing the surface as they may scratch. ...read more.

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