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Cataract and Refractive Surgery (part 7)

diện tích rõ ràng. Những triệu chứng này thường biến mất trong 3-6 tháng. Một số nỗ lực đã được thực hiện để điều trị triệu chứng hòn đảo trung tâm [9, 21]. Cắt đốt laser địa hình liên kết hoặc đầu sóng hướng dẫn là một công cụ hữu ích. | 104 Complications of Excimer Laser Surgery blows nitrogen gas during ablation has decreased the occurrence of central islands. Central islands are usually characterized by undercorrection accompanied by monocular diplopia. With topography the central elevated area is clear. These symptoms often disappear in 3 to 6 months. Several attempts have been made to treat symptomatic central islands 9 21 . The topography-linked or wavefront-guided laser ablation is a helpful tool. 8 Fig. 8.2 Retinal images. Top wavefront analysis. The higher order aberration is 1.14 pm. Bottom the retinal image evaluated by wavefront analysis pupil size 3 mm . The blurred image left improved after surgery right 8.3 Intraoperative Complications 105 Fig. 8.3 Orbscan irregular astigmatism . Top kera-tometric map shows irregular astigmatism. The visual acuity is 0.7 1.5 X sphere -0.5 D cylinder -2.0 D axis 153 . The patient complained of monocular dip- lopia during the day and at night. Bottom after wavefront-guided laser ablation the uncorrected visual acuity improved to 1.5 106 Complications of Excimer Laser Surgery 8 Fig. 8.4 Retinal images. Top wavefront analysis. The higher order aberration is 0.66 pm. Bottom the retinal image evaluated by wavefront analysis pupil size 3 mm . The blurred image left improved after surgery right 8.3.4 Undercorrection Undercorrection is the result of incorrect preoperative evaluation of refraction excessive moisture in the stromal bed decentration and problems with laser calibration. If the preoperative refraction is unstable the refraction should .