Đang chuẩn bị liên kết để tải về tài liệu:
Cataract and Refractive Surgery - part 10

Các kết quả của số lượng hạn chế của nghiên cứu này không được khuyến khích. Năm 1992, Werblin, Peiffer, và đồng tác giả [36] là người đầu tiên báo cáo 5 đôi mắt rất thiển cận cấy ghép với các mô cấy hydrogel | 12.3 Intracorneal Ring Segments 161 in humans for high myopia hyperopia and aphakia correction. The results of this limited number of studies have not been encouraging. In 1992 Werblin Peiffer and co-authors 36 were the first to report 5 highly myopic eyes implanted with hydrogel implants and followed them up for 18 months followed by Barraquer and Gomez 8 in 1997 who reported on 5 highly myopic eyes for 72 months. Both studies showed good corneal tolerance to hydrogel implants. However predictability and refraction stability were not achieved 8 37 . In aphakia hydrogel implants produced unpredictable but stable results at 72 months 8 . In cases of hyperopia in addition to unpredictability 2 4 as in high myopia and aphakia a marked increase in corneal higher order aberrations especially in mesopic conditions 6-mm pupil diameter after implantation of hydrogel corneal implants was reported by Alió Shabayek and co authors Fig. 12.1 4 . 12.2.7 Complications In spite of the limited number of studies and the limited number of human eyes that were implanted with hydrogel lenses clinical complications such as membrane formation around the lens Fig. 12.2 2 8 epithelial cyst and complete regression 8 and an increase in corneal higher order aberrations 4 were reported in addition to lack of predictability and stability. Summary for the Clinician The development of intracorneal hydrogel lenses with regard to their design better power calculation and with more specific depth of implantation could render them a good refractive alternative in cases of high hypermetropia and myopia. Correction of aphakia by intracorneal hydrogel lenses is limited when intraocular lens implantation is contraindicated. 12.3 Intracorneal Ring Segments 12.3.1 Introduction In late 1978 Fleming and Reynolds first proposed intrastromal rings as synthetic intracorneal implants for the correction of various degrees of myopia 15 . The initial implant was a complete ring Fig. 12.3 inserted through a .