Glasses Either Shrink or Enlarge the Visual Size of an Object Whereas Image Size is Dimensionally Accurate After LASIK Refractive Laser Eye Surgery. Many patients worry that LASIK will somehow alter that “naturalness” of their vision. In fact, wavefront LASIK routinely creates a more natural experience of vision than glasses.
Glasses disturb the experience of vision in several ways. First, from a practical standpoint, they can move around or get scratched and dirty, which degrades the accuracy of their correction. Second, the corrective power of glasses is only optimal in one spot called the “optical center” of the lens. If you look to the side of this “sweet spot” in the glasses lens, then you would be looking through less optimal correction which also has an increased measure of distortion compared to looking through the optical center. Also, glasses obviously do not have correction on their sides, so peripheral vision is compromised with glasses.
Finally, it is a little known fact that glasses alter image size. The stronger the prescription, the more this is the case. Nearsighted corrective lenses minify (the opposite of magnify) the image by a factor of 2% per diopter of correction due to the fact that nearsighted lenses are concave lenses. Therefore, for example, even a moderately nearsighted person with 5 diopters of nearsightedness will have a 10% reduction in the size of the world he or she perceives . Interestingly, this is true for the person looking out through the glasses and also is true when you look in through the glasses at the nearsighted person. Probably you’ve noticed that the sides of a nearsighted person’s face seem to bow inward with their glasses on.
By contrast, glasses for farsightedness magnify the image by 2% per diopter due to the fact that farsighted corrective lenses are convex lenses. Farsighted people see the world larger than it really is. Also, this explains why the eyes of a farsighted person seem much larger with their glasses on — the image is magnified to your view looking at their eyes as well!
The optical reason why nearsighted glasses minify and farsighted glasses magnify is that the lenses of the glasses sit off the plane of the eye. By contrast, both LASIK and contact lenses sit directly on the eye and therefore do not alter image size at all.
See Also
Clinical Optics
A review of spectacle magnification of images — a phenomenon particularly experienced by those wearing thick “Coke bottle” glasses.
Minification Influences Spatial Judgements in Virtual Environments
Image size minification seen with nearsighted glasses influences spatial judgement.
Visual Acuity in Laser In Situ Keratomileusis to Correct High Astigmatism in Adults with Meridional Amblyopia
Visual acuity in LASIK reviewed.
Taking Eyeglasses Seriously
A review of the complexities of glasses as a means of vision correction.
Binocular Space Perception, Aniseikonia
Glasses with different prescriptions on each eye can cause visual problems for those wearing glasses. This is not seen with contact lenses or laser vision correction refractive surgery.
Will 3-D Glasses be Regulated by the FDA?
Three dimensional glasses allow a different viewing experience, but may fall under FDA regulatory authority.
LASIK vs. Glasses
Blog site exploring the pros and cons of LASIK versus glasses as a means of vision correction.
The Real Costs of LASIK vs. Wearing Contacts or Glasses
The actual dollar costs of having LASIK are compared over a long term basis to the ongoing costs of wearing glasses or contact lenses. LASIK can be a more affordable alternative to glasses or contact lenses over the course of a lifetime.
Farsightedness
U.S. National Library of Medicine Website on Farsightedness.
Nearsightedness
U.S. National Library of Medicine Website on Nearsightedness.