| Myopia is an ocular disease of high incidence in the world, particularly in our country. In the diseases that resulted in blindness and low vision, degenerative myopia and its complications is the fourth to seventh cause of blindness. Degenerative myopia is a disease of continuous prolongation of the anteroposterior diameter (sagittal diameter) of the eyeball and expansion the posterior sclera, with subsequent posterior polar retina and choroid pathologic changes. And the visual function would be seriously harmed irreversibly. More and more scientists pay attention to the prevention and treatment of this disease. Posterior scleral reinforcement surgery is an effective surgery for degenerative myopia since it can eliminat the causes, prevent degenerative myopia progression and inhibit its complications. It has been widely recognized. After constant research and improvement have been done by domestic and foreign scientists, the clinical application of posterior scleral reinforcement surgery has achieved satisfactory results. This procedure prevents the development of myopia by increasing the thickness to enhance the resistance of the sclera. It can also improve the visual function by increasing local supply of blood and nutrients because of the mechanical and antigen stimulation.There was no definite conclusion about the mechanism of the improvement of visual quality in degenerative myopia after posterior scleral reinforcement. We are trying by means of observing the preoperative and postoperative uncorrected visual acuity, the preoperative and postoperative corrected visual acuity, anteroposterior diameter, refractive state, ocular A/B ultrasound, optical coherence tomography (OCT), visual field, visual sensitivity and eye electrophysiology. A discussion of the mechanism of improvement of the visual quality was proposed.Materials and methodsTotally 51 eyes of 45 patients of degenerative myopia had undergone posterior scleral reinforcement from August 2008 to July 2010. The number of right eye was 31, that of left eye were 20. Twenty-one males and 24 females. The range of age was 3 years to 72 years. The preoperative visual acuity was hand movement(HM)/20cm to 0.1, averagely 0.046±0.038. The refraction error was -7.00--27.00D (calculated by spherical equivalent), meanly (-16.71±4.28)D. The corrected visual acuity was 0.01 to 0.8, the average was 0.296±0.282. The anteroposterior diameter was 25.7-36.05 mm, meanly (30.03±3.11)mm. Allogeneic sclera was chosen for reinforcement materials. The surgical technique was single band posterior scleral reinforcement under local anesthesia or general anesthesia.Statistical analysis:The preoperative and postoperative ones data, and the data of 2 months and 24 months after the surgery. were measured analyzed by paired t test, including visual acuity, refraction, anteroposterior diameter, light sensitivity of central visual field, visual electrophysiology data such as volatility and time. The incidence of posterior polar lesion was analyzed by chi-square test.Results1. Postoperative visual acuity:the postoperative uncorrected visual acuity was counting fingers(CF)/30cm-0.15, the average was 0.059±0.047, it increased significantly compared with preoperative visual acuity(t=2.56, P<0.05); the visual acuity after 2 to 24 months was CF/30cm-0.15, meanly 0.064±0.043. It increased significantly compared with the preoperative visual acuity (t=2.728,P <0.01);The corrected visual acuity was 0.01-1.0 postoperatively, meanly 0.318±0.264, it increased significantly compared with the preoperative visual acuity (t =2.192,P<0.05);the corrected visual acuity 2 to 24 months after surgery was 0.01-1.0, meanly 0.387±0.258, the difference was statistically significant compared with preoperative visual acuity (t=2.967, P<0.01).2. Postoperative refraction:-7.75--26.00 D, an average of (-16.25±4.16)D, the difference was not statistically significant compared with preoperative reduced, but (t= 0.9945,P> 0.05); The refraction 2 to 24 months after surgery was-7.75--26.00D, an average of (-16.39±4.32) D. There was no significant difference compared with preoperative one (t=0.902,P>0.05).3. The anteroposterior diameter 2 to 24 months after the surgery was 26.03-35.8 mm, meanly (29.96±3.02) mm. And the preoperative one was 25.7-36.05 mm, meanly (30.03±3.11) mm. There was no statistical significance (t=0.276, P>0.05).4. Thirty-one eyes had been compared about the preoperative and postoperative physiological blind spot expansion, the central relative scotoma, paracentral scotoma and the morphological changes of universality lesions. There were significant improvement after the surgery; Compare with the average preoperative and postoperative photosensitive defect sensitivity value(MD) and the total pattern deviation(PSD) in the 31 eyes, the preoperative MD was -5.14--20.13dB, the average (-11.61±3.98) dB, the PSD was 1.93～12.7 dB, average (5.46±2.86) dB; after 2 to 24 months, the MD was -3.98～-17.94 dB, average (-8.32±3.46) dB, the PSD was 1.56～9.49 dB, average (4.46±2.75) dB, there was statistically significant difference (t=2.324 and 2.103, P<0.01).5. In 24 eyes of 31 eyes which were undergone preoperative optical coherence tomography, found various complications were found.The complications chorioretinal atrophy scar in 11 eyes, choroidal neovascularization (CNV) in 4 eyes, macular epiretinal membrane in 2 eyes, macular splitting in 6 eyes, macular hole (full thickness and lamellar) in 7 eyes, retinal detachment in 7 eyes. Atrophic scar have improved in 2 eye after surgery, CNV in 2 eyes extincted; macular membrane in 2 eyes had not changed but the traction on retina had relieved.; macular splitting in four eyes disappeared or almost disappeared; One macular hole disappeared in the three lamellar macular holes; The macular hole disappeared after surgery in 3 eyes of the 4 eyes macular hole complicated with retinal detachment. There were 3 eyes of retinal detachment without macular hole, the retina reattached well after surgery; in the 4 eyes of retina detachment with macular holes, the retinal reattached after surgery. Retinal detachment recurrence occurred in 1 eye 5 months after surgery, but there was no macular hole. The difference between preoperative manifestation of posterior polar lesions and postoperative one was statistically significant(χ2=6.637,P<0.01)Conclusion1. Scleral reinforcement is a method aimed at the cause of degenerative myopia, it is a method of preventing progression and reducing the complications of degenerative myopia. The surgery is safe and reliable.2. The uncorrected and corrected visual acuity after scleral reinforcement were stable; part of the eyes had better postoperative vision compared with preoperative one; the central visual field defects improved, and the average value of light sensitivity defect (MD) and total pattern deviation (PSD) decreased.3. The postoperative refraction and anteroposterior diameter were steady after scleral reinforcement.4. The mechanism of improvement of visual function in degenerative myopia after the surgery of scleral reinforcement might be the follow points:Scleral reinforcement reinforces of the wall of the posterior staphyloma; relaxes the traction; cures or alleviates the degenerative myopic macular atrophy and concurrent scar, choroidal neovascularization, macular splitting, macular epiretinal membrane, macular hole and macular retinal detachment, thus resulting in improved visual function and visual quality. |
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