Effect Of Different Incisions On Preexisting Corneal Astigmatism During Phacoemulsification

Cataract is one of the most reasons which cause blindness in the world, especially in China, it ranks first. At present,to the cataract patients,the main therapy method for recovering vision relies on operation. Cataract phacoemulsification (phaco) and foldable intraocular lens(IOL) implantation is the main surgery method. It have some advantages,such as small surgery incision, short operation time and good uncorrected visual acuity(UCVA) postoperation.In recent years, with the development of ophthalmologic micrurgy and the improvement in micro instrument, the cure methods of cataract is gradually turning from recovering vision operation to refractive operation. The most important factor that influence UCVA is astigmatism of preoperation and surgically induced astigmatism(SIA). Therefore, we can make different incisions on preexisting corneal astigmatism during phaco to induce astigmatism and raise the visual quality.ObjectiveAccording to the outcome of corneal topography, we select different sites and diverse surgical moduses during phaco. The prospective study will aim to investigate the effect on corneal astigmatism. We wish that it will establish a rationale of choosing the best operation incision site in clinical cataract cure.MethodsFrom September 2008 to August 2009, 63 age-related patients(77 eyes)for surgery in our hospital were divided into 3 groups according to the preexisting corneal astigmatism, different incisions for cataract surgery were made for each group. Group A(22 eyes), the preexisting corneal astigmatism less than 1.0D, received superior(11:00) clear corneal incision(CCI);GroupB(35 eyes), the preexisting corneal astigmatism was between 1.0D to 2.0D, which were divided into 2 groups.Group B1(18 eyes), CCI was made on the steepest meridian, the helping incisions and the major incisions had a included angle about 120 degree. Group B2(17 eyes), CCI was the same as Group A; Group C(20 eyes):the preexisting corneal astigmatism more than 2.0D,which were divided into 2 groups, Group C1(10 eyes), besides the superior(11:00) CCI, for surgery on the steepest meridian, an additional couple of"T"incisions were made to release the preexisting corneal astigmatism, Group C2(10 eyes), CCI was the same as Group A. The operation eyes were all implanted Rayner foldable posterior chamber intraocular lens. The UCVA, corneal astigmatism, SIA and astigmatism axis were observed at 1 week, 1 month and 3 months after operation, comparing all the data based on statistical analysis.Results1.The UCVA of postoperation in each groupThe UCVA in each group after surgery was all better than that of preoperation, difference being statistically significant (P<0.01). At 1 week, the difference between Group B1 and Group B2 was not significant (P>0.05); At 1 month and 3 months, the difference between Group B1 and Group B2 was significant (P<0.05), the UCVA of Group B1 excel that of Group B2. At 1 week, the difference between Group C1 and Group C2 was not significant (P>0.05); At 1 month and 3 months,the difference between Group C1 and Group C2 was significant (P<0.05), the UCVA of Group C1 excel that of Group C2.2. Corneal astigmatism after operationIn Group A, there were no significant difference on the corneal astigmatism before and after operation (p>0.05). The corneal astigmatism in group B1 after surgery were lower than that of preopertion, difference being statistically significant (P<0.05,P<0.01,P<0.01), At 1 week, the difference between Group B1 and Group B2 was not significant (P>0.05), between Group B1 and Group B2, there have difference being statistically significant at 1 month and 3 months (P<0.01), Group B1 astigmatism was lower than Group B2.The corneal astigmatism in Group C1 after surgery were lower than that of preopertion, difference being statistically significant (P<0.01), at 1 week,1 month and 3 months, difference being statistically significant between Group C1 and Group C2 (P<0.01), Group C1 astigmatism was lower than Group C2.3. SIA in each groupAfter surgery,each group had some SIA and the SIA was less and less, there were no significant difference on the SIA at 1 week, 1 month and 3 months (p>0.05). At 1 week,1 month and 3 months, there were no significant difference on the SIA between Group B1 and Group B2 (P>0.05), and there were no significant difference on the SIA between Group C1 and Group C2 (P>0.05).4. Astigmatism axis after operation in each groupAll the astigmatism axis showed with-the-rule astigmatism (WRA) changes at 1 week, whereas against-the-rule astigmatism (ARA) was seen at 1 month. In each group,there were no significant difference at 1 week, 1 month and 3 months (p>0.05). At 1 week,1 month and 3 months, there were no significant difference between Group B1 and Group B2 (P>0.05), and there were no significant difference between Group C1 and Group C2 (P>0.05).Conclusion1. The corneal astgmatism did not change after 3.0mm CCI phaco.2. The incisions on the steepest meridian can reduce corneal astigmatism when the preexisting corneal astigmatism was between 1.0D to 2.0D.3. The couple of"T"incisions on the steepest corneal meridian can correct the corneal astigmatism when the preexisting corneal astigmatism was more than 2.0D.