Basrah Journal of Surgery (Dec 2014)
COMPARISON BETWEEN PHOTOREFRACTIVE KERATECTOMY (PRK) AND LASER IN SITU KERATOMILEUSIS (LASIK) OUTCOME AFTER SIX MONTHS IN TREATMENT OF MYOPIC ASTIGMATISM
Abstract
Astigmatism is corrected by either by toric lenses or surgical intervention including laser refractive surgery. Photorefractive keratectomy (PRK) is performed with the excimer laser which can accurately ablate corneal tissue to an exact depth with minimal disruption of surrounding tissue, it is done by removing the epithelial layer up to Bowman layer which then ablate with anterior stroma. Laser in situ keratomileusis (LASIK) is also performed with the excimer laser, but with creation a flap involving the stroma. This study aimed to compare the differences in visual outcome after 6 months between PRK and LASIK in treatment of astigmatism. It is a retrospective study in which 222 eyes of 115 patients (some of them had only astigmatism in one eye) who underwent laser refractive correction in Al-Hakeem General Hospital in Annajaf city to correct their astigmatismic refractive error were included in the study, 152 of astigmtismic eyes were corrected by LASIK (82 of female eyes and 70 of male eyes), 67 of astigmatismic eyes were corrected by PRK ( 35 of female eyes and 32 of male eyes). Patients were grouped into six groups according to their refractive error: G1: less than 1.0 dioptre, G2: 1.0-1.9 dioptres, G3: 2.0-2.9dioptres, G4: 3.0-3.9 dioptres, G5: 4.0-4.9dioptres and G6: 5.0-14.0 dioptres. The outcome of visual acuity was followed-up by autorefraction six months postoperatively and were grouped into five groups according to their visual outcome: a:emmetropia, b:no correction, c:undercorrection, d: increase the refractive error, e: overcorrection. The results shows that in those with astigmatism between 0.25-0.9 dioptre, no statistically significant association was found between outcome and type of operation (P=0.66). In those with astigmatism between 1.0-1.9 dioptres, statistically significant association was found between outcome and type of operation (p=0.023). In those with astigmatism between 2.0-2.9 dioptres, statistically significant association was found between outcome and type of operation (P=0.0009). In those with astigmatism between 3.0-3.9 dioptres, statistically significant association was found between outcome and type of operation (P=0.001). In those with astigmatism between 4.0-4.9 dioptres, no statistically significant association was found between outcome and type of operation (P=0.113). In those with astigmatism between 5.0-14.0 dioptres, no statistically significant association was found between outcome and type of operation (P=0.92). In conclusion, there is no statistical significant difference after 6 months of correction of astigmatism wither by LASIK or PRK at different levels of refractive error.
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