Morphology changes of ocular anterior segment and its influencing factors following LASIK

Background

Laser in situ keratomileusis (LASIK) is widely applicated to correct the refractive error in ophthalmology nowadays.However, the morphology and structure changes of anterior eye segment caused by the ablation of corneal stroma and suction of negative pressure during surgery should be concerned.

Objective

This study was to assess the changes of the anterior eye segment parameters and the factors influencing these parameters after LASIK.

Methods

The clinical data of 59 eyes of 31 patients who received LASIK in Chongqing Medal Eye Institute during May 2012 to July 2013 were retrospectively analyzed.The mean age of the patients was (24.52±8.41) years and the spherical equivalent was (-5.96±3.75) D. The central anterior chamber angle (ACA), anterior chamber volume(ACV), anterior chamber depth(ACD) were measured with Sirius Scheimpflug tomography, and lens thickness (LT) was measured by A-scan before operation and 1, 3, 6 months after operation.The anterior chamber was divided into anterior and posterior parts by the plane of cornea 4 mm radius area.The ACD of cornea 4 mm radius area sagittal height section(Sag_4mmACD) (the height from posterior corneal vertex to corneal radius of 4 mm plane) and residual ACD (RACD) (the height from corneal radius of 4 mm plane to the anterior lens surface) were computed.The association between ACD and RACD or LT were assessed by Pearson correlation analysis.

Results

The ACA, ACV, ACD, RACD and LT were significantly different among various time points before and after LASIK (F=8.319, P<0.05; F=11.596, P<0.05; F=24.045, P<0.01; F=16.087, P<0.05; F=15.333, P<0.01), and the ACA, ACV, ACD and RACD were significantly decreased 1-6 months after LASIK than those before LASIK (all at P<0.05). There were no significant differences in the Sag_{4 mm} ACD between pre- and post-LASIK (all at P>0.05). The LT was significantly increased after surgery in comparison with that before surgery (P<0.01). The positive correlations were found between RACD and ACD before LASIK and in 1, 3, 6 months after LASIK (r=0.976, 0.824, 0.724, 0.938, all at P<0.05) and negative correlation between LT and ACD in 3 and 6 months after LASIK (r=-0.344, P<0.01; r=-0.363, P<0.01).

Conclusions

The ACD decrease following LASIK mainly in the sector from the plane of cornea 4 mm radius area to lens surface.The change of ACD might be associated with forward shifting of anterior lens surface caused by enhanced accommodation.

Keratomileusis, laser in situ; Anterior eye segment; Diagnostic techniques, ophthalmological; Anterior chamber; Sirius