Comparison of different intraocular pressure measurement techniques in normal eyes and post small incision lenticule extraction

Abstract

PurposeThe purpose of the study was to determine the accuracy of intraocular pressure (IOP) measurement after small incision lenticule extraction (SMILE) using Goldmann applanation tonometry (GAT) and ocular response analyzer (ORA).MethodsThis is a prospective clinical study that was conducted on 30 eyes in the interval between February 2016 and September 2016. The age of the patients ranged between 19 and 40 years. The patients underwent SMILE surgery using the femto laser. IOP was measured preoperatively and 1 month postoperatively by both techniques, the GAT and the ORA.ResultsGAT recorded lower values than ORA values (IOPcc) preoperatively and postoperatively and the difference was statistically significant. Both GAT and ORA IOP measurements decreased after SMILE. There was no statistically significant correlation between the changes in the GAT and ORA readings and the postoperative corneal pachymetry or the lenticule thickness. Both corneal hysteresis and corneal resistance factor showed significant decline after the procedure, which correlated with the lenticule thickness.ConclusionSMILE causes significant reduction in IOP measurement by ORA and GAT. Corneal biomechanics decreases following SMILE and this correlates with lenticule thickness.

<p>A Review on Different Tonometers for Intraocular Pressure Measurement After Photorefractive Keratectomy or Small Incision Lenticule Extraction</p>

“…There were 32 articles investigated in the use of tonometers or biomechanical properties of cornea in post PRK eyes and 11 articles investigated in the use of tonometers or biomechanical properties of cornea in post SMILE eyes. 38,[40][41][42][43][44][45][46][47][48][49] Photorefractive Keratectomy…”

Intraocular pressure changes and corneal biomechanics after hyperopic small-incision lenticule extraction

“…Cornea refractive surgery corrects the refractive error by removing a part of the corneal tissue, and consequently changes both the corneal shape and corneal biomechanics. Previous studies have identified this procedure to change the intraocular pressure (IOP) measurements [1,2].…”

“…It is generally accepted that IOP measurements falsely decrease after corneal myopic refractive surgery. This phenomenon is observed after photorefractive keratectomy (PRK), laser in situ keratomileusis (LASIK), and myopic small incision lenticule extraction (SMILE) [1,4].…”

Intraocular pressure changes and corneal biomechanics after hyperopic small-incision lenticule extraction

“…Previous studies have identified this procedure to change the intraocular pressure (IOP) measurements. [1,2] Among the nearly 10 million refractive procedures performed, it is estimated that more than 200,000 eyes may be at risk of a missed glaucoma diagnosis based on a conservative 2% incidence of glaucoma. [3] It is generally accepted that IOP measurements falsely decrease after corneal myopic refractive surgery.…”

“…This phenomenon is observed after photorefractive keratectomy (PRK), laser in situ keratomileusis (LASIK), and myopic small incision lenticule extraction (SMILE). [1,4] The principle of hyperopic correction, which differs from that of myopic correction, is to make the central cornea steeper. This is achieved with SMILE by creating a concave lenticule that is thinnest in the central area.…”