Clinical Observation Of Visual Quality After Optimized Refractive Keratectomy (ORK )and Analysis Of Influencing Factors In Treatment Of Myopia

Purpose:Investigate and analyse the clinical curative effect of Optimized Refractive Keratectomy(ORK) in the treatment of myopia, comparing to Laser in Situ Keratomileusis( LASIK) in visual quality postoperatively from the objective and subjective aspects. Also try to search for the releated reasons .Method : Between 2009 to 2010 ,we randomly selected 203 patients ,willing to do surgery. Patients were randomly divided into two groups: ORK operation group, LASIK surgery group. The two groups are divided into low and moderate myopia group (not more than -6.00D) and high myopia (more than -6.00D) by spherical equivalent degree. ORKL (ORK low ~ moderate myopia group) ; ORKH (ORK high myopia group) . LASIKL (ORK low to moderate myopia group) ; LASIKH (LASIK high myopia group) . The Follow-up is up to six months. We make a record about visual acuity, residual refractive error, corneal surface of the spherical aberration, coma, higher order aberrations RMS, Q-value, corneal thickness and contrast sensitivity at 1 week, 3 months and 6 months postoperatively. Besides the objective examination, the patients fillde the visual quality table at 6 months after the surgeries . Patients with the complaint after the tests are categorized as research groups, patients without the complaint after the test are categorized as control group. Logistic regression analysis was used to screen the risk factors related to unsatisfying night vision. SPSS17.0 software is applied for statistical analysis. Reasult :1. ORK groups and LASIK groups have none statistically significant differences in the best uncorrected visual acuity and residual refractive error. While ORK Group presented better safety index and efficacy index than the LASIK group.2. ORK groups and LASIK groups the total higher order RMS values ,coma RMS,spherical aberration RMS, have a significantly change, comparing postoperatively 1 week,3 months and 6 months to preoperative . LASIK groups have more obvious changes in high myopia groups .3. Increase of Q-values in hight myopia groups has statistically significant difference ,the lower myopia groups have no significant statistical difference,at 3 months and 6 months after surgeries with pre-operation ; SimK-values showed no significant changes in the two groups for patients with low to moderate myopia and high myopia .4. ORK group need more corneal thickness than LASIK group for the same spherical equivalent degree, which has statistically significant difference.5. subjective questions results showed that: preoperative and postoperative patients who complained of discomfort at night are mostly high myopia. The time which patients complained of discomfort after the operation were at night, and complains increase in high myopia group. The risks affect visual quality: cutting zone by the difference between pupil diameter, pre-correction of preoperative refraction, surgical, Q value, age, corneal thickness and so on.Conclusion:1. patients in both ORK groups and LASIK groups gain good and stable visual ability and visual quality, so ORK is a safe and effective technique of individualized ablation.2. The RMS of higher order aberration, spherical aberration in ORK groups and LASIK groups have significant statistics difference ,after 1 month, 3 months, high myopia in ORK groups are obviously smaller than the LASIK groups post-operation, so ORK can lower the aberration increasing.3. Q-value post-operation increased significantly than pre-operation . And the corneal surface morphology has stabilized in the two groups three months after operation ,ORK can maintain asphericity of corneal better . 4. Gutting the same degree ORK groups use more corneal stroma tissue than in the LASIK groups,but residual corneal thickness is still within the safe range Postoperatively .5. Preoperation , the visual quality of the low and medium myopia groups are better than high myopia group. Compared with the preoperative ,the light and dark conditionsvisual quality has decreased in the two groups after surgery, which is more significantly decreased in high myopia groups. Decline in the quality of night vision is affected by many factors, the difference in cutting zone pupil diameter is the multiple factor, preoperative refractive spherical error the second factor , surgical methods the third factor.