Assessing Changes in Corneal Densitometry in Patients After Small Incision Lenticule Extraction (SMILE)

The aim is to assess for any lasting changes in corneal densitometry (CD) in patients who underwent small incision lenticule extraction (SMILE) and developed early transient postoperative corneal haze.

This retrospective chart review analyzed 98 eyes from 49 patients who underwent SMILE at the Hoopes Vision Clinic and had one-year postoperative Pentacam CD (Oculus Optikgeräte GmbH, Wetzlar, Germany). These were compared to 78 eyes from 42 unoperated myopic control patients with documented CD measurements. The preoperative CD, measured in grayscale units (GSU), was compared between SMILE patients who developed early transient haze ("transient haze group"), SMILE patients who did not build haze ("non-haze group"), and patients who did not undergo any refractive surgery ("controls"). The postoperative CD was compared between the transient haze and non-haze groups. Then, the postoperative CD was compared to the preoperative CD for the non-haze group and transient haze group, respectively.

The only significant difference in preoperative CD was in the central layer of the cornea at the 6-10 mm annulus between the non-haze group and controls (17.31 ±3.77 vs. 16.18 ±3.92 GSU; p=0.04). Postoperatively, there were no differences in CD between the non-haze group and the transient haze group (p<0.05). Comparing postoperative CD to preoperative CD, the non-haze group had increased CD in the 2-6 mm annulus of the anterior (1.54 ±0.45 GSU; p=0.001), posterior (0.65 ±2.28 GSU; p=0.032), and full thickness (0.72 ±0.29 GSU; p=0.006) layers of the cornea in addition to an increased CD in the 6-10 mm annulus of the posterior corneal layer (1.19 ±0.55 GSU; p=0.049). The transient haze group had an increased CD in the 2-6 mm annulus of the anterior (2.61 ±1.09 GSU; p=0.021) and full thickness (1.44 ±0.68 GSU; p=0.039) layers of the cornea.

There is no lasting difference in CD between patients who develop postoperative transient haze and those who do not after undergoing SMILE.