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Simulator for twilight and night vision
after LASIK or PRK / LASEK
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LASIK is an excellent procedure for the correction of mild to moderate
nearsightedness and for mild farsightedness. Your vision at dawn, dusk
and at night stays the same as prior to LASIK. However, LASIK is subject
to certain limitations, which result from the severity of the existing
nearsightedness or farsightedness in conjunction with the diameter of
the pupil. When the nearsightedness or farsightedness is very severe
and when the pupil is very dilated, halos (rings of light surrounding
a light source) may occur at dawn, dusk and at night and may result
in decreased vision.
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A halo occurs as a result of an imbalance between the size of the corneal zone treated with Excimer laser ablation and the diameter of the pupil when dilated at night. If the diameter of the dilated pupil exceeds the diameter of the "ablated" corneal zone, a halo may be perceived because part of the rays of light coming into the eye produce a blurry image.
Why not just "ablate" a bigger area of the cornea?
Unfortunately, the thickness of the cornea is only about 0.5 mm and a maximum of 0.15 mm may be "ablated". Therefore, in cases of severe nearsightedness or farsightedness, only a part of the cornea may be "ablated", which results in halos.
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FreeVis would like to demonstrate the sources of these perceived images
and show how they affect your vision. For your convenience, we created
a simulator, which will demonstrate your vision in twilight and at night,
taking into consideration your refractive error and the diameter of
your pupil when dilated in darkness.
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Unfortunately, no simulator can provide a precise image for each individual
patient because human vision is very adaptable and we generally get
used to halos and therefore may not perceive them anymore after a while.
However, the simulator demonstrates that in cases of mild to moderate
nearsightedness or farsightedness, no change in vision is perceived.
It also demonstrates how halos may influence twilight and night vision
for patients with severe nearsightedness.
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The images provided in the simulator are based on statements provided
by our patients several months after LASIK surgery. More noticeable
halos may be perceived within the first days to weeks after treatment.
We suggest that you consult your surgeon prior to treatment to determine
whether you can expect any limitations in twilight and night vision.
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