Correlation Of Opaque Bubble Layer With Corneal Biomechanics And Densitometry In Eyes Undergoing Smile With Visumax 800 For Myopia Correction

To evaluate the correlation of  Opaque Bubble Layer (OBL) with corneal biomechanics and densitometry in eyes undergoing SMILE with VisuMax 800 for myopia correction. The purpose was to evaluate OBL pattern using an optimized energy setting, produced by the new laser, which fires at a pulse repetition rate of 2 MHz, versus its predecessor VisuMax 500 with a frequency of 500 kHz.

Nethradhama Superspeciality Eye Hospital, Bengaluru, Karnataka, India.

All eligible patients underwent CORVIS ST and Pentacam HR for pre-op evaluation. VisuMax 800 with 2 MHz frequency was used to perform SMILE. OBL pattern was graded from 0-100% by an independent observer from the treatment PDF using a transparent overlay divided into zones assigned different numbers depending upon the density of OBL. Corvis biomechanical index (CBI), Tomographic biomechanical index (TBI), densitometry values and post-operative day 1 Objective Scatter Index( OSI) were correlated with OBL. Pearson correlations were found and their significance was tested.

Eighty eight eyes of 88 patients, with mean age of 26.86 ±4.20 years and spherical equivalent of -4.98±2.63 D were evaluated. The mean OBL grade observed ( in % age) was 57.61±18.88% (15-80%). The mean values of densitometry, CBI, TBI and post-op OSI were 18.28±1.51, 0.41±0.26, 0.23±0.23 and 1.70±0.98 respectively. A significant positive correlation was found between OBL with pre-op densitometry, R- score=0.286, p <0.001 and post-op OSI score, R-score=0.413, p<0.001. With respect to biomechanics, a significant negative correlation of OBL with CBI was observed, R-score= -0.224, p=0.03. With TBI, a negative correlation of OBL was observed, however, the result was not statistically significant, R-score= -0.140, p=0.19.

Occurrence of OBL in SMILE could be influenced by various factors like CBI, TBI  and densitometry. Based on these results, existing nomograms for energy and spot settings may be revised, which may improve  the immediate post-op recovery and wow factor after the procedure.