| Objective and significanceOcular perforation injuries are common clinically and result in corneal astigmatism as corneal scars forming, which affects visual function severely. Sometimes the astigmatism is difficult to correct by spectacles or excimer laser. Oculists have strived to explore and improve operation methods to correct corneal astigmatism for a century. These operations are effective in astimagtism treatment ,but there are also many defects and restricts in practice. Especially, correcting traumatic corneal astimagtism by operation hasn't been reported up to now. The research to investigate the categories ,features and correction effect of the traumatic corneal astigmatism, with the expectation to explore the regularity of the traumatic corneal astigmatism, to seek a safe and practical therapy method to the curing of corneal astigmatism by easy facility from the point of view of clinical application.The research was divided into two parts .The first part explored the relationship and regularity between traumatic corneal scars and astimagtism .The second part systematically elucidated the operation methods and provided theory foundation for astigmatism correction operation. Part 1 The regularity study of traumatic corneal astigmatism1. Methods30 cases(30 eyes) of suffering from corneal perforation injuries which consist with screening standard were collected in the study. (excepting the cases with irregular scars , the cases whose scars are in the central region of cornea and the cases with other diseases and operations in eyes ).30 cases (30eyes) accepted examinations of corneal topography,computer and retinoscopy optometry(<35y applying for cycloplegica)and took photographs under slitlamp. The following items were precisely surveied :the shape , length and location of corneal scars,the astigmatism degree and axial direction. In order to explore the relationships between the length of corneal scars and the power of corneal astigmatism , the datas were entered into the table and analyzed statistically them with linear regression equation,then the relatioinships were analyzed,which of the corneal scars of different shapes, length and location and the type of astigmatism and the degree of astigmatism.2.Results(1)The correlation coefficient between the length of corneal scars and the degree of astigmatism is 0.563(p<0.01), which identified that there is correlation between the scars length and astigmatism. The regression equation is the following: Y=1.703+0.478X. the result of correlation test is the fowllowing: F=13.023, P=0.001 ,which identified the relationship of them is positive correlation(2) The relations of the shape,length,and location of corneal scars and the type of astigmatism and the degree of astigmatism are the following :①the scars parallelling to the corneal limbus resulted in myopic astigmastism as the suture made the meridian perpendicular to the scar steep②the scars perpendicular to the corneal limbus resulted in hypermetropic astigmastism as the suture made the meridian perpendicular to the scar flat. Part 2 The study of correcting corneal astigmatism by operation1,Methods1.1 The preoperative examinations : 22 patients(22 eyes) of traumatic corneal astigmism were collected randomly who were 3 months after the corneal suture operation and whose types of astigmatism are variant. the astigmatism power of all the cases exceeded 2.5D ,the length of corneal scars exceeded 4mm. the preoperative examination are the following:(1) Slitlamp examination, fundus examination, IOP measurement, taking photographs under slitlamp or microscope, measuring the scars precisely,recording the shape and position of scars.(2) computer and retinoscopy optometry:recording naked vision,corrected vision ,the power and axial direction of astigmatism.(3) Corneal topography examination(TMS,AMO OBSCANⅡ):recording the power and axial direction of astigmatism and analysing corneal steep and flat meridian.(4) Examinations of contrast sensitivity, stereoscopic vision and wavefront diffrence.1.2 The design and principle of operation(1)the shape and location of incision : to remain tuansparent cornea utmostly ,the incisions were designed to locate in flat meridian behind corneal limbus 0.5-1.0mm,which are a pair of symmetrical bracket-shaped incisions parallelling to corneal limbus. the length of incisions are 90°radian and the depth is 3/4 sclera's thickness. Then we wedge excised little tissue of sclera and sutured the incision. the flat meridian became steep after the operation ,meanwhile the steep meridian became flat due to "the couple effect", so the myopic astigmatism was corrected .(2) The width calculation of wedge excision: According to Gullstrand's schematic eye,a calculating formula was deduced: D_V represents the corrected power of astigmatism . x represents the width of wedge excision. Such as, when x is 0.1mm, the D_V is 0.73. Due to the "coupling effect",the actual corrected power of astigmatism is: 0.73×(1 +1/2 ) = 1.1D, which is similar with Troutman's test value. .However ,when x is 0.2mm,the actual corrected power of astigmatism is 1.4D,and when x is 0.3mm the corrected value is 1.7D. similarily we can calculate the the width of wedge excision according to the preoperative astigmatism power(3)The calculation of corrected astigmatism power: the corrected astigmatism power must be considered preoperatively according to "the laws of cornea flexible hemisphere" and "the couple effect". According to the Troutman's theories, for example,when wedge excision and stretching suture were done on the flat 90°meridian,the meridian will become steep,meanwhile the 180°meridian will become flat. The proportion of refractive power change is 2:1.1.3 The method of operationWe designed to Symmetrically make a pair of incisions on the corneal flat meridian behind corneal limbus 0.5-lmm.The length of incisions is 90°radian and the depth is 2/3 sclera's thickness. The width of incision is the calculation according to the formula that had been deduced,then we sutured the incisions with 10-0 polypropylene stitch and adjusted the tensity with the Placidou ophthalmometer and buried the knot.1.4 The disposal of resultMake comparison,evaluation and analysis to the surgery following-up reviews on the functional movememt of the result by patients' uncorrected visual acuity,corrected visual acuity and diopter,and compare the result of eye pressure, anterior chamber'depth, KAPPA angle, corneal endothelium numbers, ObscanⅡcorneal topograph's examination.2.Results(1)The postoperatative vision The preoperative power of corneal astigmatism was averagely 5.13±1.85D and the average uncorrected vision of preoperation was:0.23±0.12. The postoperative power of corneal astigmatism is reduced to 1.42±0.97D, correspondingly the postoperative vision improved to 0.61±0.25. The distinctions had statistical significance(P<0.01) .(2)The dioptric state of postoperation①To the simple or compound hypermetropic astigmatism of +2.50D～+4.00D, the patients had satisfactory uncorrected postoperative vision. when the power of hypermetropic astigmatism exceed +5.00D,the uncorrected vision was not very well,but the patients had a satisfactory corrected vision.②To the simple or compound myopic astigmatism which be lower than -3.00D,the patients had satisfactory uncorrected or corrected postoperative vision.To the myopic or compound astigmatism exceeding -3.00D,the patients had a higher postoperative myopia and were unsatisfactory with the uncorrected vision.③To the mixing astigmatism which was lower than 4.00D,the patients had satisfied uncorrected and corrected postoperative vision. To the higher mixing astigmatism,the patients had satisfied corrected vision.(3) 3 mpnths after operation, recheck the corneal topography examination , the simulated keratoscope reading become into43.75±1.98D from preoperative 45.03±2.16D,it's intimate with normal 43.05±1.20D, but the results of IOP,ACD,KAPPA angle, corneal endothelium numbers have no distinction. The corneal tonographic map had distinguished improve.(4) CS test of postoperation: There are no significant difference between preoperation and postoperation of 1 month, except for 6cpd in daytime, 3cpd under day glare conditions, and 6cpd in night glare illumination.(P<0.05). The comparisons of CS between preoperation and postoperation of 3 months showed significant difference (P<0.01); and it is the same as the comparisons between one month and three months postoperation. In this investigation, nobody can identify 18cpd under night glare conditions, who are excluded statistically.(5) Postoperative stereoacuity: comparing to 17(77.3%) patients included in the 400″～200″group preoperatively, 13(59.1%) patients were remained in this group one month post operation, and only 8(36.4%) patients were remained three months postoperation. Data showed that more than 60% of the patients had the stereoacuity within 100″three months postoperation.(6) The postoperative complication:The undercorrection and the dioptric transformation is the frequent complication.Conclusions1. Among the patients of traumatic corneal astigmatism,the scars parallelling to corneal limbus formed myopic astigmatism, and the scars perpendicular to corneal limbus formed hypermetropia astigmatism.2. On the paracentral, peripheral and limbal zone of cornea,the length of linear scars and the astigmatism power have positive correlation,the linear regression equation is : Y=0.481+0.724X.3. Paired wedge shape excision combined stretching suture behind limbus is a safe and effective surgical operation for correcting astigmatism. It can correct the simple or compound hypermetropic astigmatism between +2.50D～+4.00D and the myopia astigmatism which lower than—2.00D.4. According to Gullstrand's schematic eye,a calculating formula was deduced. It'sBy the formula and the "coupling effect",the width of the wedge shape excision can be calaculated considering the refractive power would be corrected. But the accurate details and the applied perspective need more investigation and verification.
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