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Mathematical model to compare the relative tensile strength of the cornea after PRK, LASIK and small incision lenticule extraction (SMILE)

Session Details

Session Title: Corneal biomechanics

Session Date/Time: Tuesday 08/10/2013 | 08:00-10:30

Paper Time: 09:14

Venue: Elicium 1 (First Floor)

First Author: : D.Reinstein UK

Co Author(s): :    T. Archer   B. Randleman           

Abstract Details

Purpose:

Develop a mathematical model to estimate the relative differences in post-operative stromal tensile strength following PRK, LASIK and Small Incision Lenticule Extraction (SMILE).

Setting:

London Vision Clinic, London, UK

Methods:

Using previously published data where in-vitro corneal stromal tensile strength was determined as a function of depth, a mathematical model was built to calculate the relative remaining tensile strength by fitting the data with a fourth order polynomial function yielding a very high correlation coefficient (R2=0.930). Calculating the area under this function provided a measure of total stromal tensile strength (TTS), based only on the residual stromal layer for PRK or LASIK and the residual stromal layers above and below the lenticule interface for SMILE.

Results:

Postoperative TTS was greatest after SMILE, followed by PRK, then LASIK; for example, in a 550-?m cornea after 100-?m tissue removal, postoperative TTS was 75% for SMILE (130-?m cap), 68% for PRK, and 54% for LASIK (110-?m flap). The postoperative TTS decreased for thinner corneal pachymetry for all treatment types. In LASIK, the postoperative TTS decreased with increasing flap thickness by 0.22%/?m, but increased by 0.08%/?m for greater cap thickness in SMILE. The model predicted that SMILE lenticule thickness could be ~100 ?m greater than the LASIK ablation depth and still have equivalent corneal strength (equivalent to about 7.75 D).

Conclusions:

This mathematical model predicts that the postoperative TTS is considerably higher after SMILE than both PRK and LASIK, as expected given that the strongest anterior lamellae remain intact. Consequently, SMILE should be able to correct higher levels of myopia.

Financial Interest:

... receives consulting fees, retainer, or contract payments from a company producing, developing or supplying the product or procedure presented