Intraocular Lens Power Calculation

Intraocular lens power calculation

The aim of an accurate intraocular lens power calculation is to provide an intraocular lens (IOL) that fits the specific needs and desires of the individual patient. The development of better instrumentation for measuring the eye's axial length (AL) and the use of more precise mathematical formulas to perform the appropriate calculations have significantly improved the accuracy with which the surgeon determines the IOL power. In order to determine the power of intraocular lens several values need to be known: Eye's axial length (AL) Corneal power (K) Postoperative IOL position within the eye known as estimated lens position (ELP) The anterior chamber constant: A-constant or another lens related constantOf these parameters the first two are measured before the implantation, the third parameter, the ELP, need to be estimated mathematically before the implantation and the last parameter is provided by the manufacturer of the intraocular lens.

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Pancake lens

A pancake lens is colloquial term for a flat, thin lens (short barrel), generally a normal or slightly wide prime lens for a camera

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Lens Aboudou

Lens Aboudou (born February 9, 1990) is a French basketball player who currently plays for JDA Dijon Basket of the LNB Pro A.

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Aline Réveillaud de Lens

Aline Rveillaud de Lens (born March 2, 1881 in Paris, died February 10, 1925 in Fez), was a French novelist and painter who lived and worked in Tunisia and Morocco. She signed her works A. R. de Lens, A.-R. de Lens and Aline de Lens

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Will this lens fit on my canon rebel eos? What lens mount do I need?

I assume that you bought the lens thinking that it would fit your camera and thinking it was a great deal. It may very well be a nice lens but it wo not fit your camera without an adapter. And it is usually not worth bothering with. You could keep the lens and use it with an adapter or even buy a Canon camera that you can use it on. You could resell the lens since it wo not fit your camera. Just explain that you did not know that it would not fit your camera and if it is not too much of an inconvenience you would like to cancel the purchase. If they agree to cancel the purchase, the seller could offer the lens in a second chance to the other bidder or just relist it altogether. They may say no, in which case you keep it or resell it. In the future, check before you buy something to see if it will work with your camera.

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Media Lens

Media Lens is a British media analysis website established in 2001 by David Cromwell and David Edwards. Cromwell and Edwards are the site's editors and only regular contributors. Their aim is to scrutinise and question the mainstream media's coverage of significant events and issues and to draw attention to what they consider "the systemic failure of the corporate media to report the world honestly and accurately". The editors, whose site is financed by donations from website visitors, issue regular "Media Alerts" concentrating on those mainstream media outlets legally obliged to be impartial (the BBC and Channel 4 News) or usually considered liberal like The Guardian and The Independent. The site's editors frequently draw attention to what they see as the limits within which the liberal media operates, and provide "a riveting expose of the myth of liberal media based on a variety of empirical case studies", according to Graham Murdock and Michael Pickering. Media Lens is admired by John Pilger, who has called the website "remarkable" and described the writers as "the cyber guardians of honest journalism". Other journalists, in particular Peter Oborne, have also made positive comments about the group, although it has come into conflict with other journalists. The Observer's foreign editor Peter Beaumont asserted that the group operated a "campaign" against John Sloboda and the Iraq Body Count (accusing the latter of underestimating the number of casualties). George Monbiot has also criticised Media Lens for their defence of Edward S. Herman against charges of "belittling the acts of genocide".

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Is it dangerous to do a lens change with power on?

It really depends on the camera being used and how it is designed. There are certain things that the camera should do before a lens is removed such as ensuring the mirror is down to protect the sensor and potentially disengaging mechanical links to drive aperture and focus (though these are generally designed to be self-disengaging when you remove the lens.)Many cameras, however, can tell when you push the lens removal button and can do this process by the time you actually unscrew and remove the lens. The best advice is follow the manual, if it cautions against doing it, then you are best off to listen to the manufacturer that designed your camera. If they do not object to it, you should be fine.Personally, I use a Canon 5D Mark iii and have no problems with removing the lens on the fly and reattaching a new one. I've even done this in relatively dusty environments without a problem yet (over the course of a year). The only thing it specifies is that if you are going to use a teleconverter, you should attach it to the lens first so that the correct information is available when you attach the lens assembly to the camera.As far as damage that could occur, the most likely issue would be that something could happen to the sensor or mirror as the mirror moves to try and cover the sensor as you are removing the lens or if the mirror does not move at all, leaving the sensor directly exposed to outside contaminants (such as dust). There could be other issues specific to your camera body though and depending on lens design, it could be possible (however unlikely), for example for the mirror to collide with part of the lens. This would do substantially more damage and possibly break the mirror, rendering the camera effectively useless until repairs can be made.While I can not prove it, if the sensor having a charge actually could draw in dust, then why on earth would not camera makers cut the power to it when the lens is removed. If they can do it when the camera is powered off, they can do it when the lens is removed too and it would be bad design not to (either that or it simply is an old wives tail that it's a problem).One final thought, it may actually be worse to power off for a change. While there is not any evidence of dust attracting being an issue, powering off and powering on does potentially result in extra self-cleaning cycles as well as other power off and power on activities. These activities have a much higher chance of causing wear and tear on the camera and resulting in eventual damage than the remote possibility that it might attract dust (which could simply be cleaned off). I doubt that either of these is even a measurable contributor, but if I had to gamble, I would gamble that turning off for every lens change is actually more harmful (by an insignificantly small amount.)

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