To ensure correct centration of LRIs, two approaches may be used: (1) When available, the meridional location of prominent landmarks on the conjunctiva or limbus can be noted and drawn relative to the 6 o'clock and 12 o'clock positions.
LIMBO RELAXING INCISION PLUS
Incisions are centered around the plus axis of the cylinder of the manifest refraction. The length and number of LRI are chosen based on age and refractive astigmatism. Corneal disease that might interfere with corneal wound healing should be ruled out. It is applicable for a refractive cylinder = 0.75 D stable within ☐.50 D on manifest refraction (MR) at least 2 weeks apart, and a mean spherical equivalent cycloplegic refraction within ☐.75 D of emmetropia. 16–18 Based on a corneal diameter of 11.5 mm, a chord length of 45° equals 4.5 mm and a chord length of 60° equals 6.0 mm. Table 23-1 shows the current nomogram of Wang et al. Nevertheless, taking a pachymeter measurement at the site of the cut is recommended to prevent accidental perforation into the anterior chamber. Although corneal thickness varies by patient, the most preferred incision depth is 600 μm. In the light of the limitations of alternative approaches, LRI seem to be a viable option in selected cases.ĭifferent nomograms for LRIs exist. Thus, complications associated with reablating eyes that have had surface ablation and with lifting or recutting of a laser in situ keratomileusis (LASIK) flap are avoided. However, if astigmatism has been induced by cataract or corneal surgery, the incisions can be made months after the initial surgery to improve uncorrected visual acuity (UCVA) to acceptable values. LRI can be performed with cataract surgery if an astigmatic error was pre-existing, allowing the simultaneous correction of a patient's astigmatism. This is because the LRI are made in the 10.5 mm periphery and most patients’ pupils will not dilate that wide, eliminating night glare. A major advantage of LRI is that night vision problems which may be associated with incisions in the corneal midperiphery are avoided. LRI can be considered safe and effective for correcting astigmatism of up to 2.5 D.
These cuts are also called peripheral corneal relaxing incisions (PCRI).
Limbal relaxing incisions (LRI) are a type of arcuate incisions made at the limbus to correct low degrees of astigmatism. Nordan, in Refractive Surgery (Second Edition), 2007 LIMBAL RELAXING INCISIONS
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