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Corneal power measurements in eyes after small incision lenticule extraction for myopia

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First Author: V.de Rojas SPAIN

Co Author(s):    A. Tobío                    

Abstract Details

Purpose:

To evaluate the accuracy of the measurements of corneal power obtained by ray tracing with a Scheimpflug camera combined with a Placido disc corneal topographer in eyes after small incision lenticule extraction for myopia (SMILE).

Setting:

Victoria de Rojas Instituto Oftalmológico, A Coruña, Spain

Methods:

Retrospective study including 50 eyes of 50 patients who underwent myopic SMILE. Cycloplejic refraction was recorded preoperatively and three months postoperatively. Simulated keratometry (SimK), Mean Pupil Power (MPP) (ray tracing within the diameter of the entrance pupil range 3 to 6 mm), anterior and posterior corneal radius (3 mm zone), and corneal thickness were obtained with a Scheimpflug–Placido topographer, preoperatively and three months postoperatively. True Net Power (TNP), Equivalent Keratometry Readings (EKR), Haigis Equivalent Power Formula (HEPF) were calculated and these measurements, as well as MPP, were compared with the corneal power calculated with the clinical history method (CHM).

Results:

Corneal power measurements calculated with all methods were significantly different from CHM (p<0.001), except for the values of MPP obtained at 5, 5,5 and 6 mm which were not significantly different from the value of CHM (p>0.001). A good direct correlation was found between CHM and HEPF (R2=0.8568), between CHM and EKR (R2=0.9022), and between CHM and MPP at all the diameters of the entrance pupil (3mm R2=0.8816; 3.5 mm R2=0.8844; 4 mm R2=0.8836; 4.5 mm R2=0.8824; 5 mm R2=0.8801; 5.5 mm R2=0.8754; 6 mm R2=0.8656). The best direct correlation was found between CHM and TNP (TCP) (R2=0.9057).

Conclusions:

MPP obtained by ray tracing within diameters of entrance pupil of 5, 5,5 and 6 mm could predict corrected corneal power derived from the CHM in eyes following SMILE surgery. Financial interest: Victoria de Rojas: Zeiss consultant; Adrián Tobío: none

Financial Disclosure:

... receives consulting fees, retainer, or contract payments from a competing company