الفهرس | Only 14 pages are availabe for public view |
Abstract SUMMARY Management of unilateral cataract in children is a difficult problem in ophthalmology. The major obstacle is not surgical rather, it is related to the long term problems involving the aphakic correction and occlusion therapy. Amblyopiaz- The critical period in visual development has been one of the central concepts to emerge during the last few years. The recent studies proved irreversible anatomical and physiological changes occuring in lateral geniculate body following visual deprivation with an onset during the first few months of life. From observations on the visual outcome ofpaticnts with congenital or acquired cataract, it was suggested that susceptability to deprivation amblyopia decreased logarithmically with age, and thatthis period lasts approximately Six years in humans. The usual method to treat amblyopia is the occlusion therapy, and occlusion should be started soon after the proper optical correction. Contact lensest- Contact lenses have certain advantages as it reduce retinal image disparities to 4-8 % thus it maintain binocular single vision. It abolishes the prismatic effect caused by aphakic spectacles and 35 the visual field is enlarged. The main advantage is the ability to meet the changing refractive needs of the child. However contact lenses have difficulties and disadvantages:- The high loss rate, the risk of causing trauma, the intolerance. Even in successful contact lens wearers, there are significant amblyopia producing factors such as non-wear periods and induced vertical diplopia caused by decentration of these high-plus, low riding lenses. A proper contact lens fitting can be done by obtaining a keratometric reading for the corneal curvature, selection of the widest lens diameter to minimize loss rate, and the power is determined after retinoscopy with added over correction for near focus in young children. As regards to the type of contact lens soft lenses, extended wear lenses, hard lenses can be used and each has its advantages and disadvantages. Intraocular Lensest- With the use of I.O.L. implantation, a relatively equal retinal size image is obtained, and there is no decentration with induced vertical diplopia experienced with contact lenses. Moreover, there is no chance for contamination, intolerance, difficulities in preservation and handling. 36 The selection of the type ofl.O.L depends upon the condition of anterior segment. Regarding the power of I.O.L, there are different options. Whether to use an I.O.L. power that is suitable for an adult and thus allowing the child to grow towards emmetropia or to implant an I.O.L that produces an immediate emmetropia but this will induce errors of increasing magnitude as the eye grows. Complicationz- There are peculiar complication releated to the I.O.L implantation in children, they can be summarised as follows:- * Operative complications as global collapse, posterior capsular rupture and vitreous loss, hyphema, IfIS complications and poor I.O.L placement. * Post operative complications as striate keratitis, corneal oedema, iridocyclitis, iris complication pupillary fibrin membrane, secondary glaucoma, I.O.L dislocation, endophthalmitis and I.O.L precepitotes. Epikeratophakia:- Epikeratophakia involves the onlying of pre-lathed donor lenticule onto the host cornea which has been denuded of its epithelium. It is extraocular, safe and reversible procedure. The operation IS recommended to be used in infants above one year of age as the 37 highest technical failure rate with the difficulty in predicting the power requirements are much demonstrated in this age group. Complications- Epithelial defects, infection, irregular astigmatism, interface opacities, prolonged lenticular haze and unpredictability. Conclusionz- The acceptable view is to remove the visually significant unilateral cataract as early as possible and to fit the child with a contact lens as primary procedure. If contact lens proves inadequate to prevent amblyopia, I.O.L. implantation or epikeratophakia may be considered. |