Understanding telescopic lens implant surgery

The traditional IOL VIP system?
The new IOL VIP Revolution?
The implantable Miniature Telescope (IMT)
Does the system work like a magnifying glass?
Does the telescopic lens correct distance vision without glasses?
Will the telescopic lens be right for you?
What happens if you have already had cataract surgery?
What is the alternative to telescopic lens surgery?

 

What is a telescopic lens?

The term telescopic lens is an implant lens system inserted into the eye following cataract surgery. It has been developed to improve central vision in patients with macular disease.

In standard cataract extraction (known as phaco-emulsification) the opaque natural lens is replaced with a single clear plastic lens. In the IOL VIP procedure two small plastic lenses are inserted into the eye, which together give a telescopic effect.

It is helpful to know a little about the eye and how it works in order to understand the IOL VIP system.

The cornea forms the clear window into the eye. The iris, which is the coloured part of the eye with the black pupil in the middle, lies behind the cornea. The lens lies behind the iris.

Anatomy of a normal eye

The wall of the eye is formed by three layers, the retina, the choroid and the sclera.

The cornea forms the clear window into the eye. The iris, which is the coloured part of the eye with the black pupil in the middle, lies behind the cornea. The lens lies behind the iris.

The retina is the light-sensitive nerve tissue that lines the inner wall of the eye. Rays of light enter the eye, passing through the cornea, pupil and lens before focusing on to the retina. The retina contains photoreceptors which convert light into electrical impulses. In the healthy eye these impulses are sent via the optic nerve to the brain, where sight is interpreted as clear, bright, colourful images. The retina can be likened to photographic film in a camera.

The macula is a small area at the centre of the retina. It is very important as it is responsible for our central vision. It allows us to see fine detail for activities such as reading, recognising faces, watching television and driving. It also enables us to see colour.

The choroid is the underlying vascular (blood vessel) layer of the eye from which the retina receives oxygen and nutrients.

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How does a telescopic lens system work?

There are a number of lens-based telescopic systems on the market. They look rather different, but all work in the same way using two lenses to produce a magnified image. The choice of telescope is guided by the degree of visual loss, those with moderate visual impairment usually doing best with a low-power telescope and those with more severe visual impairment being guided towards a high-power telescope.

The lens behind the iris is a minifying glass (thick at the edges). The lens in front of the iris is a magnifying glass (thick in the middle).

There are two ways in which the implant lenses may be of benefit:

1. The two lenses can operate as a miniature telescope, magnifying the image at the macula.

2. The alignment of the lenses can be rotated to divert the image toward a less damaged area of the macula.

The IOL VIP is designed to produce relatively low-level magnification of around thirty per cent. Macular disease limits vision by producing a blind spot or an area of impaired vision. The effect of the IOL VIP system is to enlarge the image around the blind spot, making the central area of impairment less intrusive.

In some patients the IOL VIP may be more effective when an area just away from the macula is used as the point of visual fixation. In other words, the patient may choose to look just “off centre” to get the best possible picture. If appropriate we will lend you a laptop computer with visual exercises, to help you learn to fixate on a new point and achieve your best visual potential.

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Does the system work like a magnifying glass?

No. A magnifying glass only produces a larger image when an object is held close to the eye. The IOL VIP procedure produces a larger image at distance as well, rather like looking through weak binoculars.

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Does the IOL VIP correct distance vision without glasses, as is often the case for modern cataract surgery?

Standard lenses used in cataract surgery come in a variety of powers such that, after careful measurement of the eye, long or short sightedness can be corrected.  Whilst this is not the case for the IOL VIP we are now able to offer something more than the original “one size fits all”, avoiding the need for extremely thick spectacles.

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Will the IOL VIP be right for you?

Even if you have previously been told that “nothing can be done” for your eye condition, the IOL VIP may help improve your central vision.

Implantation of the IOL VIP will only be performed when your macular degeneration has been assessed as stable and wet disease, if present, has been treated.

In clinic before surgery, a special simulator can be used to test the potential improvement in vision.

Through this the world appears larger and objects come closer. The simulator demonstrates the effect of the IOL VIP, allowing you to experience the potential enhancement before proceeding with surgery.

If the simulator is of benefit when testing in clinic, it is highly likely that the surgical procedure will produce an effect at least as good, if not better. We will help you to decide whether the IOL VIP procedure is right for you.

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What happens if you have already had cataract surgery?

A new system is now available to add to the existing implant lens for patients who have already undergone cataract surgery. As yet results for this technique are unknown.

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What is the alternative to IOL VIP surgery?

For some patients, cataract surgery alone may improve illumination of the retina and help with everyday tasks.

No other telescopic system is currently marketed, although it is highly likely that new implant lenses will become available, giving us a choice of different implants for different degrees of visual loss.

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