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Most patients undergoing Eye Laser Surgery in the past were very happy with their daytime vision but were aware of lesser quality vision at night or at dawn or dusk. The reason is that all lasers had less effect in the peripheral parts of the cornea and an oblate shape was created that increased glare at night. The Wavelight Allegretto laser can compensates for this by increasing the number of shots in the periphery in order to create a prolate shape. This leads to increased quality night vision.

The diagram demonstrates how a perfect sphere has spherical aberration. For this reason, the human cornea is not perfectly spherical, but rather aspheric. It is steeper in the centre and flatter in the periphery. The Allegretto laser attempts to maintain this relationship between central steepness and peripheral flatness.

EFFECTS OF CORNEAL CURVATURE ON ABLATION PROFILE

The Allegretto Wave compensates for the reduced energy absorption in the periphery with more spots.

Result: True, large optical zone and ability to create a prolate cornea shape

The problem:

A Perfect Sphere

Even a perfect sphere has spherical aberration with the peripheral rays being refracted more than the central ray.

The normal corneal curvature is asperical i.e. steeper at the apex and less steep (flatter) at the periphery.

After regular laser surgery.

This treatment has increased the spherical abberation with the peripheral rays being refracted even more than before

After wavefront-optimised laser surgery (Allegretto Standard treatment)

This treatment has reduced the spherical aberration with the peripheral rays being refracted less than before and all the rays intersecting at the same point.

The Treatment

Wavefront-Guided Treatments

Wavefront-Guided (Customised) treatments are designed to correct higher order errors or aberrations.

This treatment has reduced the spherical aberration with the peripheral rays being refracted less than before and all the rays intersecting at the same point

Wavelight Wavefront Analyser

The Wavelight Wavefront Analyser uses visible light to map the wavefront aberrations. An image is projected into the eye through a dilated pupil (after getting drops) and then the image at the back of the eye is photographed through the central, aberration-free part of the cornea. This photograph is then compared to the image that was projected by software and a digital map is produced of the wavefront. The data is then transferred to the laser to do a customised treatment.

The Technology

This technology can only work if the resolution of the laser is very good. The success of the procedure relies on good diagnostic data (the wavefront map) and the ability to transfer that treatment profile to the cornea (the laser).

Spot size

– one of the smallest spot sizes available (0.95mm)

– Increases resolution (accuracy/smoothness)

– This is one of the smallest spot size currently available.

The smaller the spot size the higher the resolution (like drawing with a crayon as opposed to using a fine pencil).

The smaller spot size however needs a faster repetition rate to allow the same treatment to be done in the same time. The Allegretto is so fast, that despite having one of the smallest spot size, it is still one of the fastest laser available. It treats one diopter every five seconds.

 DO YOU HAVE AN UNANSWERED QUESTION? CALL US ON 011 346 5025 MONDAY – FRIDAY 8AM- 5:30PM. Safesight Cataract and Eye Laser Centre, Waverley, Johannesburg. 

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Contact Information

  • Address:159 Rivonia Road Morningside Sandton
  • Phone:011 346 5025
  • Phone:011 346 5088
  • Mobile+27815455385
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