1: Refractive Lens Exchange

This procedure is recommended to correct the spectacle power in people over the age of 40 years. After the age of 40 years the natural lens of eye becomes had and non flexible and therefore looses its ability to change focus from distance to reading.

An eye is like a camera with a lens focusing light on the retina. Glasses are required if image is out of focus. In RLE the natural lens is replaced by an artificial lens of a suitable power to bring the image to focus on the retina without the need of glasses.

A simple way to understand is that the natural lens of the eye has a power of +21 Diopters. If a person has a spectacle power of -8 Diopters, then by exchanging the natural lens with an artificial lens of a power of +13, the spectacle power of -8 Diopters would stand corrected. However, practically calculations are not this simple, ultrasound, biometry or special costly optical biometers like the Lenstar have to be used to accurately determine power of lens which is to be implanted in eye.

There are 2 types of lenses that can be used for this correction

This is the lens which has a single power and the most popular lens used in this category at our centeris the Acrysof IQ Lens from Alcon (USA).

This lens would enable the person to see clearly without glasses. Since this lens is a hard, non flexible artificial lens, it would not change its power to focus for near, therefore for reading purposes, a spectacle power of approx. +2.5 is required.

Since an average persons activity involves 95% of distant viewing and only 5% of near viewing, a person tends to be very comfortable from this new formed freedom of glasses and he does not mind using glasses occasionally for reading.

For people desirous of having good functional vision for distance and reading, the multifocal lens provides one such option. The most popular lens in this category used at our center is Acrisof Restor Multifocal lens from Alcon(USA)

The lens has rings of fresnyl prisms which divide the incoming light into two bundles, one focused for distance and one focused for near, thereby giving the person the advantage of seeing both for distance and near without glasses. However multi-focal lenses can sometimes be associated with halos and glare around light and slight loss of contrast. Most of the people have the capacity to adapt to these problems over a period of time without losing out on the advantage of spectacle free distance and near vision.

The Restor Multi-Focal lens comes in three models:

  1. Model 1 comes with a near vision addition of +4 which is equivalent to +2.5 of near vision glasses.
  2. Model 2 comes with an addition of +3 which is equivalent to +1.75 of the near vision glasses.
  3. Model 3 comes with an addition of +2.5 which is equivalent to +1.25 of the near vision glasses.

The Patient may be offered these different combinations depending upon his nature of work or personal requirements.

A +4 lens giving a spectacle equivalent of +2.5 is ideal for distance and reading but gives a poor quality of vision at an in between distance which is also referred to as the computer screen distance from the eye.

The Model with a +2.5 addition equivalent to a spectacle power of +1.25 gives an excellent intermediary vision for computer work but fails if the person has high expectancy on reading without glasses.

The model 2 with a +3 addition is a compromise between the two lenses.

The model with +2.5 addition gives least amount of halos and glares around lights and is ideal for people who want to be spectacle free for routine indoor and outdoor activities and computer work and are willing to use a little spectacle correction for fine tuning.

2: Vision Correction In Elderly

Presbyopia or decrease in near vision with age. In a young individual the natural lens of eye is soft and flexible and works like a auto-focus lens. By contraction of the internal eye muscles it can change its power from distance to near.

Around the age of 45, the natural lens within the eye undergoes age changes and tends to become hard and non flexible. Even with contraction of internal eye muscles it is unable to change its power from distance to near therefore additional spectacle power is required for reading purposes.

Mono-vision

In the elderly the eye requires a distance and a near spectacle power. The laser can correct any one power either for distance or for near. In mono-vision, one eye is corrected fully to focus it for distance, and other partially for near. Thus with both eyes open, the person can do most of his distance and near routine activities without glasses and only for very fine work does a person need glasses.

RLE with Multifocal Lens

For people desirous of having good functional vision for distance and reading, the multifocal lens provides one such option. The most popular lens in this category used at our center is Acrisof Restor Multifocal lens from Alcon(USA)

The lens has rings of fresnyl prisms which divide the incoming light into two bundles, one focused for distance and one focused for near, thereby giving the person the advantage of seeing both for distance and near without glasses. However multi-focal lenses can sometimes be associated with halos and glare around light and slight loss of contrast. Most of the people have the capacity to adapt to these problems over a period of time without losing out on the advantage of spectacle free distance and near vision.

The Restor Multi-Focal lens comes in three models:

  • Model 1 comes with a near vision addition of +4 which is equivalent to +2.5 of near vision glasses.
  • Model 2 comes with an addition of +3 which is equivalent to +1.75 of the near vision glasses.
  • Model 3 comes with an addition of +2.5 which is equivalent to +1.25 of the near vision glasses.

The Patient may be offered these different combinations depending upon his nature of work or personal requirements.

A +4 lens giving a spectacle equivalent of +2.5 is ideal for distance and reading but gives a poor quality of vision at an in between distance which is also referred to as the computer screen distance from the eye.

The Model with a +2.5 addition equivalent to a spectacle power of +1.25 gives an excellent intermediary vision for computer work but fails if the person has high expectancy on reading without glasses.

The model 2 with a +3 addition is a compromise between the two lenses.

The model with +2.5 addition gives least amount of halos and glares around lights and is ideal for people who want to be spectacle free for routine indoor and outdoor activities and computer work and are willing to use a little spectacle correction for fine tuning.

Corneal Inlays

A lot of research and innovations are in progress to overcome this near vision handicap. One of the recent innovations is in the form of corneal inlays.

By placing inlays in the cornea, the near vision is enhanced, without losing the advantage of distance vision without glasses.

There are 2 popular models of corneal inlays:

  1. Raindrop Inlays
  2. Kamra Inlays

Raindrop Inlays

Principle – raindrop corneal inlay is a 2mm implant which is just 30 microns thick in center. It is made of a hydrogel material which is highly bio compatible material. It is implanted within the deeper layers of cornea in the center of the line of sight. By making the central 2mm of the cornea steep it enhances the capability of a person to see near vision objects without any significant loss of distant vision. The lens is implanted only in one eye which is called the non -dominant eye. This is usually the left eye in right handed people. Thus with both eyes open the person can now have comfortable vision for distance and near without glasses.

A femto second laser like the FS200 is a must to create the plane in the cornea to implant this inlay.

Kamra Inlays

Principle – The principle of Kamra inlay is it increases the depth of field using the principle of small-aperture optics  (an extension of pin hole) to restore near and intermediate visual acuity without significantly affecting distance vision.

A small 5 micron thick button of 3.8mm diameter with a central hole of 1.6 mm is placed in the center of the cornea in one eye, usually the left eye which is the non – dominating eye. The 1.6 mm pin hole gives an additional advantage of near vision.

In all of the above treatment, technology and surgeon skills unite to give you the best desired result. However, mild variations can always be expected.

3: Intacs

Intacs is face of modern technology for Refractive Correction. It is useful in low myopia -1.0D to -3.0D and in case of keratoconus how ever in low myopia the choice of refractive correction is Lasik.

In keratoconus Intacs have troven value by centering the cone, reducing the cylinder power and improving the quality of vision (by reducing aberration at the level of cornea).

Patient of keratoconus can under-go Intacs with or without C3R procedure but it is preferable to do both the procedure at the same sitting. There may or may not be small amount of residual power after intacs which can be corrected by wearing specs or contact lenses. Higher residual powers may be corrected by ICL. To quality of vision for keratoconus patient after Intacs is much better ever after wearing specs.


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