Limbal relaxing incisions (LRI) are a
refractive surgical procedure to correct minor
astigmatism
Astigmatism is a type of refractive error due to rotational asymmetry in the eye's refractive power. The lens and cornea of an eye without astigmatism are nearly spherical, with only a single radius of curvature, and any refractive errors ...
in the eye. Incisions part way through the cornea are made at one side or at opposite edges of the
cornea
The cornea is the transparency (optics), transparent front part of the eyeball which covers the Iris (anatomy), iris, pupil, and Anterior chamber of eyeball, anterior chamber. Along with the anterior chamber and Lens (anatomy), lens, the cornea ...
, following the curve of the
iris, causing a slight flattening of the cornea in that area.
Because the incisions are outside of the field of view, they do not cause glare and other visual effects that result from other corneal surgeries like
radial keratotomy
Radial keratotomy (RK) is a refractive surgery, refractive surgical procedure to correct myopia (nearsightedness). It was developed in 1974 by Svyatoslav Fyodorov, a Russian Ophthalmology, ophthalmologist. It has been largely supplanted by newer, ...
.
LRI have become the most common technique to correct astigmatism as part of
cataract
A cataract is a cloudy area in the lens (anatomy), lens of the eye that leads to a visual impairment, decrease in vision of the eye. Cataracts often develop slowly and can affect one or both eyes. Symptoms may include faded colours, blurry or ...
surgery.
They are simpler and less expensive than laser surgery such as
LASIK
LASIK or Lasik (; "laser-assisted in situ keratomileusis"), commonly referred to as laser eye surgery or laser vision correction, is a type of refractive surgery for the correction of myopia, hyperopia, and astigmatism. LASIK surgery is p ...
or
photorefractive keratectomy and avoid the precise placement requirements of
toric IOLs.
Good results do not require the location and length of the incisions to be highly precise, and the incisions can easily be extended later if the original procedure did not correct all of the astigmatism.
LRIs have a coupling ratio of close to 1:1, meaning that the amount of flattening induced in the incised meridian as balanced by steepening 90° away, so negligible change in sphero-equivalent occurs, and no adjustment of IOL power is required.
Recovery is generally quick and painless, although the patient may experience discomfort.
References
External links
* https://web.archive.org/web/20090201073737/http://www.stlukeseye.com/professionals/lri_nomogram.htm
{{surgery-stub
Refractive surgeries