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Unstable Vision Prescription and Lasik

Lasik can correct vision, but the refractive error prescription must be stable.

Topographical map of a central island after Lasik  
A changing prescription is generally a contraindication for Lasik.  

Unstable Refractive Error

An appropriate refractive surgery patient needs at least two consecutive years with less than 0.25 diopters of change in eyeglass prescription. The refractive error at the time of surgery can be corrected by surgery, but unstable error will cause vision to degrade and additional surgery may be required. Also, an unstable refractive error in an adult may indicate a disease or malady that could be a contraindication for laser vision correction surgery.

Cause of Refractive Error

The reason for refractive error like myopia (nearsighted, shortsighted) and hyperopia (farsighted, longsighted) is commonly that the eye itself is too long (myopia) or too short (hyperopia). Light entering the eye is focused in front of the retina for a person who is myopic and focused behind the retina for a person who is hyperopic.

Astigmatism commonly means that the cornea is irregular. Instead of being spherical like the top of a ball, the cornea is ellipical like the back of a spoon. Laser assisted refractive surgery can resolve most astigmatism, but progressive astigmatism may be a sign of a serious problem.

Presbyopia is when the muscles around the natural lens within the eye are less able stretch or squeeze the lens to change its focus. This natural change of the lens shape for close vision is called accommodation. Presbyopia is why most people need reading glasses or bifocals after age 40.

How Laser Vision Correction Works

Conventional or custom wavefront Lasik, Bladeless Lasik, PRK, or other laser assisted refractive surgery procedures change the point of focus by changing the shape of the cornea. In a process that removes corneal tissue, the cornea shape is changed so the light entering the eye is focused more closely at the retina, not behind or in front.

Laser vision correction cannot cure presbyopia, however there are workarounds like monovision that can reduce the need for reading glasses.

Unstable Astigmatism

An unstable astigmatism is more critical than unstable myopia or hyperopia. Progressive astigmatism may indicate corneal disease such as keratoconus that would be a contraindication for laser vision correction.

Reading Glasses

The loss of accommodation is a natural part of the aging process usually starting in the fourth decade of life. The need for stronger reading glasses indicates progressive presbyopia and is normally not a concern for Lasik, PRK, LASEK, Epi-Lasik, etc.

Looking For Best Lasik Surgeon?

If you are ready to choose a doctor to be evaluated for conventional or custom wavefront Lasik, Bladeless Lasik, PRK, or any refractive surgery procedure, we recommend you consider a doctor who has been evaluated and certified by the USAEyes nonprofit organization. Locate a USAEyes Evaluated & Certified Lasik Doctor.

Personalized Answers

If this article did not fully answer your questions, use our free Ask Lasik Expert patient forum.

Recent Progressive Refractive Error Medical Journal Articles...

Related Articles

Excessive Corneal Flattening and Thinning After Corneal Cross-linking: Single-Case Report With 5-Year Follow-up.

Cornea. 2015 Jun;34(6):704-6

Authors: Kymionis GD, Tsoulnaras KI, Liakopoulos DA, Paraskevopoulos TA, Kouroupaki AI, Tsilimbaris MK

PURPOSE: To present a case of significant progressive corneal flattening and thinning after corneal cross-linking (CXL), with 5 years of follow-up.
METHODS: Case report.
RESULTS: A 23-year-old woman presented with bilateral progressive keratoconus and received CXL treatment (Dresden protocol) for both eyes in March 2009. The patient has demonstrated gradual significant corneal thinning (from a preoperative value of 464 μm to 243 μm) and progressive flattening (+11.1-diopter change in spherical equivalent) in her right eye, over a 5-year period. The fellow eye remained stable during the same postoperative period.
CONCLUSIONS: This is the first case report of significant progressive corneal flattening and thinning after undergoing CXL treatment for progressive keratoconus.

PMID: 25811728 [PubMed - indexed for MEDLINE]


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