| Objective: Glaucoma is about 12.3% in the eye disease that induce blindness,and its incidence rate is 0.21%. Among the short-sightedness the incidence of glaucoma was significantly higher than normal population,about 2-3 times. In glaucoma diagnosis and treatment intraocular pressure is an important index, But is influenced by many factors,such as: eye-wall hardness, corneal curvature, corneal thickness, etc.The relationship between intraocular pressure and myopia is very close, The increase of intraocular pressure is a department of the factors that can not be ignored in the development of myopia.[1,2] Laser in situ keratomileusis (LASIK) that is cutting corneal thickness by laser to achieve the purpose of the treatment of myopia. Because of corneal changes in the structure so that the measured value of the intraocular pressure changes. This experiment through surveying the related indexes before and after LASIK, aimed at analysis factors that related to intraocular pressure change before and after LASIK and to seek the best formula one can accurately estimate the true intraocular pressure,to avoid misdiagnosis in patients with glaucoma and to develop in line with the objectives of their own IOP value,which provides basis for clinical diagnosis and treatment of glaucoma. Methods:1 Case inclusion criteria: over 18 years of age; corrected visual acuity 1.0; not wear contact lenses for more than two weeks; exclude the impact of corneal healing of systemic diseases; exclude acute and chronic eye diseases; exclude a family history of glaucoma, high intraocular pressure such as; surgery follow-up after more than 3 months.2 Experimental groups: according to the preoperative refraction the study objects are divided into three groups: group of low myopia (<-3D); group of moderate myopia (≥3D, 6D <); group of high myopia (≥6D).3 Observation: preoperative and postoperative more than 3 months were measured refraction, intraocular pressure, corneal curvature (k value) and central corneal thickness (CCT).4 Statistical analysis: The obtained data use the statistical software of SPSS16.0 processing paired t test, ANOVA and correlation analysis.Results:1 Change of IOP: Preoperative: intraocular pressure of low myopia group was 16.17±2.73mmHg (12-22mmHg); moderate myopia group was 16.00±2.86mmHg (11-23mmHg); high myopia group was 17.12±2.37mmHg (13-22mmHg), after: low myopia group descend to 12.33±3.12mmHg (7-16mmHg); moderate myopia group reduced to 10.70±1.88mmHg (8.5-15mmHg); high myopia group dropped to 9.76±3.02mmHg (6-19mmHg), in each group before and after surgery were statistically significant changes in intraocular pressure (P values of three groups are .000)2 Change of central corneal thickness (CCT): Preoperative corneal thickness for the low myopia group was 541.11±12.07μm (522-566μm); moderate myopia group was 543.14±17.26μm (513-572μm); high myopia group was 547.65±28.77 (505-634μm). Postoperative corneal thickness, respectively were, 465.00±37.99μm (402-517μm),459.04±28.29μm (408-522μm),467.68±45.86μm (403-524μm), in each group before and after LASIK corneal thickness change statistical significance (P values of three groups are .000).3 Change of corneal curvature: preoperative corneal curvature low myopiagroup for 42.74±1.08 (41.00-44.70); moderate myopia group was 43.45±1.78 (37.50-45.90); high myopia group was 43.89±1.00 (42.10-46.10). Postoperative corneal curvature were 38.21±1.95,37.91±2.41,37.92±2.06, differences before and after surgery in each group had statistical significance (P values of three groups are .000)4 Change of diopter: preoperative low myopia group was -1.98±0.62 (-1.5 ~ -2.75); moderate myopia group was -4.45±0.85 (-3 ~ -5.75); high myopia group was -7.79±1.34 (-6 ~ -11.25). Postoperative were:-0.43±0.63 (-1.5 ~ 1.0),-0.66±1.10 (-3.00 ~ 1.25),-0.61±0.96 (-3.75 ~ 0.75), each group has statistical significance difference between before and after LASIK (P values of three groups are .000).5 The relationship between corneal thickness and intraocular pressure: preoperative IOP and CCT was positively correlated (r = 0.343, t = 3.269, P = 0.002); postoperative the CCT difference and IOP change was highly positive correlation (r = 0.544, t = 5.793, P <0.001).6 The relationship between corneal curvature and intraocular pressure: preoperative corneal curvature and intraocular pressure was positive correlation (r = 0.223, t = 2.043, P = 0.044); postoperative IOP change and corneal curvature difference was positive correlation too (r = 0.389, t = 3.921, P <0.001).7 The relationship between refraction and IOP: preoperative refraction and the intraocular pressure does not yet exist correlation (r = 0.059, t = 0.524, P = 0.601); postoperative refraction difference with the IOP difference was positively correlated (r = 0.393, t = 3.967, P <0.001).8 The formula of correction of intraocular pressure after LASIK: low myopia group, according to IOP correction formula derived from the value of preoperative intraocular pressure intraocular pressure have statistically significant difference (F = 2.915, P = 0.017,α= 0.05), which formula 1,2,4,5 from IOP values compared with the preoperative IOP was not significant (P = 0.058, P = 0.69, P = 0.61, P = 0.235),IOP values derived from the formula 3 with preoperative IOP compared have statistical significance (P = 0.002); Moderate myopia group, according to IOP correction formula derived from IOP values compared with the preoperative IOP differences were statistically significant (F = 50.716, P <0.001),formula 5 obtained with the preoperative IOP values showed no statistical significance (P = 0.127); High myopia group, according to IOP correction formula derived from preoperative IOP and IOP difference was statistically significant (F = 16.549, P < 0.001), formula 3,5 derived from the preoperative IOP values showed no statistical significance (P = 0.1, P = 0.988,).Conclusion:1 Myopia intraocular pressure and central corneal thickness, corneal curvature was positively correlated with the diopter no correlation.2 Myopia dopter and central corneal thickness had no correlation while with corneal curvature associated.3 After LASIK corneal thinner, corneal curvature decreased, the measured values to reduce intraocular pressure.4 Decline in the value of IOP after LASIK and corneal thickness difference, corneal curvature and refraction had positive linear correlation.5 Correction formula: IOP(real)=NCT+ 0.028×cutting thickness +3.21, is able to more accurate estimates of IOP after LASIK to correct value. |
PDF Full Text Request