Therapeutic wavefront LASIK was used to correct night vision problems after conventional LASIK performed elsewhere in a patient with very large pupils. In my last blog, I talked about how large pupils are not necessarily a problem for night vision and LASIK. Unfortunately, the myth that large pupils cause night vision problems after LASIK still persists.
In this blog, I want to tell you about an example of the relationship between large pupils and night vision after LASIK.
Around the time that Customized Wavefront laser eye surgery was first approved by the FDA, I had a patient from Ventura come to see me who had previously had LASIK done elsewhere using conventional LASIK. He had a very poor outcome. This patient had 20/20 vision in bright lights, but under dim lights or night conditions, he had terrible vision with a washout of contrast. He had a great deal of trouble function after his LASIK surgery in low or dim light and could not drive at night. This patient also had a very large pupil. He had tried wearing night driving glasses and even using drops to constrict his large pupil when driving at night, but none of this worked very well for him.
When this patient first came to see me, he was convinced his large pupil was the culprit as he did get some small egree of improvement when using drops to constrict his pupil for night driving. I did customized wavefront measurements on his eyes and found that his previous conventional LASIK had induced a great deal of distortion in his corneas called “spherical aberration.” Interestingly, the patient did not have any residual nearsightedness, farsightedness, or astigmatism — he just had this spherical aberration in both eyes from his previous non-wavefront laser eye surgery. I also did confirm that he had a very large pupil.
Because the wavefront measurements had identified the spherical aberration in his cornea, this gave me a target to treat. I performed Customized Wavefront LASIK on both of his eyes to try to help him with his night vision. In this case, of course, I was not treating his “prescription” to help him get out of glasses as we normally do — I was treating his night vision symptoms. The treatment was very successful and the patient had perfect night and low light level vision afterwards. This is called “therapeutic wavefront laser eye surgery” because visual degredation — and not just the patient’s prescription — was being treateed. I published this case in the scientific literature and many others have subsequently benefited from therapeutic wavefront laser eye surgery since that time.
The moral of this story is that the patient’s night vision problems were solved by using therapeutic wavefront surgery to remove the distortions in his cornea which had been placed there by his previous conventional surgery. Obviously, his pupil size — which was quite large — stayed the same, yet his night vision dramatically improved. This interesting case serves as evidence that large pupils per se do not cause poor night vision. Rather, distortions of optics cause night vision problems. Once the distortions are present, then it is true that their impact is made worse in the presence of a large pupil, but the root cause is the distortions — not the pupil size. This is why using the wavefront excimer laser to reduce his distortions worked so much better than using drops to constrict his pupils.
See Also
Functional Vision and Corneal Changes After LASIK
This paper looks at the role of spherical aberration and night vision problems after LASIK
Pupil Size and Quality of Vision After LASIK
This study looks at the role of pupil size in conventional, non-wavefront LASIK
Effect of Pupil Size on Visual Function After LASIK
This study looks at the role of pupil size after conventional, non-wavefront LASIK in one eye versus using both eyes together
Effect of Pupil Size on Quality of Vision after Wavefront Guided LASIK
This study from Stanford University found that, at one year after LASIK, there was no increase incidence of night vision problems in patients with large pupils.