Refractive Surgery in Pediatric Anisometropia

Transcription

1 Refractive Surgery in Pediatric Anisometropia Fttbz! Submitted For Fulfillment of the M.Sc. Degree In Ophthalmology Cz! Emad Aly Ahmed M.B.B.ch Voefs!Tvqfswjtjpo Tvqfswjtjpo! Prof. Dr. Golzamin Mohamed Ragheb El-Hawary P rofessor of O phthalm ology F aculty of M edicine A in Sham s U niversity Dr. Waleed Mohamed Abdel Raouf El-Zawahry L ecturer of O phthalm ology F aculty of M edicine A in Sham s U niversity Faculty F of M edicine A in Sham s U niversity 2012

2 Bdlopxmfehfnfou First of all, I would like to express my prayerful thanks to Allah. I would like to express may deepest appreciation and respect to Qspg/! Es/!! Hpm{bnjo! Npibnfe! Fm.Ibxbsz Ibxbsz- Professor of ophthalmology, Faculty of Medicine, Ain Shams University, for her encouragement, continuous help, unlimited support, valuable guidance, important advice and kind supervision throughout the course of this work. No words can express my thanks, respect and gratitude to Dr. Waleed Mohamed El-Zawahry, lecturer of ophthalmology, Faculty of Medicine, Ain Shams University, for his precious advise, generous assistance and excellent guidance for every step of this work, and for his meticulous supervision which enriched the work by his outstanding knowledge. Thanks for his kind advice throughout this work.i am truly grateful for him; being always generous with his precious time. Finally, I would like to express my sincere thanks to all those who helped me directly or indirectly during the preparation of this work.

3 Mjtu!pg!Dpoufout!! Subject Page List of Abbreviations I List of Tables... III List of Figures IV Introduction 1 Aim of the Work 4 Review of Literature Dibqufs!)2*; Introduction to Refractive Surgery in 5 Children.. Dibqufs!)3*; Photorefractive Keratectomy in 22 Children (PRK).. Dibqufs!)4*; Laser Assisted in Situ Keratomileusis 40 (LASIK).. Dibqufs!)5*; Phakic Intra Ocular Lens Implantation 73 in Children (Phakic IOL) Dibqufs!)6*; Clear Lens Extraction or Exchange in 100 Children Summary References Arabic Summary

4 Mjtu!pg!Bccsfwjbujpot List of Abbreviations AC-PIOL AK AK ALK BCVA CK CLE D FDA ICL ICRS IOP LASEK LASIK LTK OKN PC-PIOL PDS PIOLs PL PRK Anterior chamber Phakic Intraocular Lenses. Astigmatic keratotomy. Astigmatic keratotomy. Automated lamellar keratoplasty. Best corrected visual acuity. Conductive keratoplasty. Clear lens extraction. Diopter. Food Drug Administration. Implantable contact lens. Intrastromal Corneal Ring Segments. Intraocular pressure. Laser subepithelial keratomileusis. Laser in situ keratomileusis. Laser thermal keratoplasty. Optokinetic nystagmus. Posterior chamber Phakic Intraocular Lens. Pigmentary dispersion syndrome. Phakic Intraocular Lenses. Preferential looking. Photorefractive keratotomy. I

5 Mjtu!pg!Bccsfwjbujpot pvep RK SCVA TACs UCVA VA VEP WHO Pattern-reversal visually evoked potential. Radial keratotomy. Surgically corrected visual acuity. Teller Acuity Cards. Uncorrected visual acuity. Visual acuity. Visually evoked potential. World Health Organization. II

6 Mjtu!pg!Ubcmft! List of Tables Table No. Title Page Table (1) Types of angle supported PIOLs 75 Table (2) Types of Iris Supported PIOLs 78 Table (3) Types of PC PIOLs 79 III

7 Mjtu!pg!Gjhvsft! List of Figures Figure No. Title Page Figure (1) Steps of PRK 23 Figure (2) Haze after PRK 31 Figure (3) Steps of LASIK 41 Figure (4) Surgical technique of LASIK 45 Figure (5) Stromal scarring in an incomplete flap after 54 an aborted LASIK Figure (6) Buttonhole 55 Figure (7) Displacement of a corneal flap 58 Figure (8) Epithelial ingrowth 59 Figure (9) Diffuse lamellar keratitis 64 Figure (10) Phakic 6H2 lens 76 Figure (11) GBR/Vivarte implant 76 Figure (12) Schematic drawing of the ZSAL-4 anglesupported 76 phakic IOL Figure (13) Kelman Duet lens - Separate haptic and 76 optic Figure (14) I-CARE phakic IOL features 76 Figure (15) 5-mm optic Artisan lens 78 Figure (16) 6-mm optic Artisan lens 78 Figure (17) Artiflex phakic intraocular lens 79 Figure (18) Implantation iris supported AC-PIOL 85 Figure (19) Introduction of angle supported AC-PIOL. 87 IV

8 Mjtu!pg!Gjhvsft! Figure No. Title Page Figure (20) Implantation of the ICL. 89 Figure (21) Endophthalmitis after AC phakic IOL 92 implantation. Figure (22) Cataract formation after implantation of PC 93 phakic IOL. Figure (23) Pupil ovalization 95 V

9 Jouspevdujpo Introduction Anisometropia refers to any difference in the spherical equivalents between the two eyes. Fortunately, anisometropia in children can usually be corrected fully without symptomatic effects. Although adults may be annoyed by uncorrected anisometropia, they may be totally intolerant of initial spectacle correction. Unequal image size, or aniseikonia, may occur, and the prismatic effect of the glasses will vary in different directions of gaze, inducing anisophoria. Anisophoria is usually more bothersome than aniseikonia for patients with spectaclecorrected anisometropias (Miller et al., 2006). There is no doubt that anisometropia is a cause of amblyopia. Uncorrected anisometropia in children may lead to amblyopia, specially if one eye, is hyperopic. The exact mechanism of anisometropic amblyopia remains unclear, although it has been suggested that there may be active inhibition of the fovea to overcome the interference caused by attempting to superimpose a focused image in one eye and a defocused image in the other (Utine et al., 2008). Refractive surgical procedures performed with the intent to reduce or eliminate refractive errors can generally be categorized as corneal or lenticular. Kerato-refractive procedures include radial keratotomy (RK), astigmatic 1

10 Jouspevdujpo keratotomy (AK), Photorefractive keratotomy (PRK), laser in situ keratomileusis (LASIK), implantation of plastic ring segments (e.g., Intacs), laser thermal keratoplasty (LTK), and radio frequency conductive keratoplasty (CK). Lenticular refractive procedures include cataract and clear lens extraction with intraocular lens implantation, phakic intraocular lens implantation, and piggyback lens implantation (Nepomuceno et al., 2005). Myopia is the most common refractive defect in the world. Excimer laser refractive surgery has been challenging myopia since 1988 when the first Excimer laser PRK for myopia on a sighted human eye was performed by McDonald and coworkers (Drak et al., 2000). Young individuals can accommodate for low amounts of hyperopia and so may be under-represented in the populations of most eye care practitioners. However, high hyperopia can be amblyogenic either because of the inability to maintain retinal focus or because the stimulation for convergence results in a constant eye turn. Studies in adults show that there is a family tendency toward high hyperopia. For this reason, hyperopic patients should be advised that their infant relatives should be examined to roll out amblyopic risk factors (Zadok et al., 2003). 2

11 Jouspevdujpo Treatment of astigmatism has been the second major challenge in the history of Excimer laser refractive surgery. Regression, corneal haze, and functional symptoms secondary to optical aberrations are possible complications of astigmatism correction with Excimer laser either using PRK, LASEK, or LASIK (Epstein et al., 2006). For children with severe anisometropia, refractive surgery can help to head off amblyopia. Refractive surgery is often thought to fall under the exclusive purview of adult patients who simply wish to rid themselves of using contact lenses or glasses. However, for some children refractive surgery can open visual doors in ways that otherwise would not be possible (Nizzola, 2007). 3

12 Bjn!pg!uif!Xpsl Aim of the Work The aim of this essay is to give the light on recent modalities of refractive surgery in pediatric anisometropia. 4

13 Jouspevdujpo!up!sfgsbdujwf!tvshfsz!jo!dijmesfo Introduction to Refractive Surgery in Children Definition: Refractive surgery is a category of treatments designed to induce structural change to the eye with the intent of altering its refractive status. There are two broad categories of refractive surgery: Keratorefractive, during which the physical architecture of the cornea is altered; and intraocular, during which synthetic lenses are placed into the eye, with or without removal of the natural crystalline lens (Harmon, 2008). Indications: Refractive surgery in children is controversial; it is mainly performed when conventional treatment by glasses or contact lenses has failed. The goal is to restore a level of functional vision or to correct amblyopia or to aid binocular function. Whereas adult refractive surgery is often an elective or cosmetic option, the same is not true for pediatric patients. Instead, patients should have a threshold magnitude of refractive error and failure with traditional therapy for their amblyopia or bilateral blur (Tychsen, 2008). Indications for performing refractive surgery in the pediatric setting have been categorized as obligatory, functional 5

14 Jouspevdujpo!up!sfgsbdujwf!tvshfsz!jo!dijmesfo and elective. Obligatory indications included children under the age of 7 years with anisometropic amblyopia who were intolerant of spectacles or contact lenses. Functional indications include performance of LASIK in older children to allow them to participate more fully in sport and other activities of daily living. Elective indications are reserved for older teenagers with adequate corrected vision and include all indications for which refractive surgery is currently performed in adults, including cosmesis (O Keefe and Nolan, 2004). It has been reported that visual acuity and binocular vision outcomes were significantly better in children who received permanent surgical correction of anisometropia than in those who were conventionally treated using contact lenses (Yin et al., 2007). Modalities of refractive surgery in children Keratorefractive Surgery: The most frequently performed procedures for low to moderate myopia utilize the Excimer laser, which was first approved for this purpose by the FDA in A surface ablation technique, photorefractive keratectomy (PRK), was the first procedure performed; subsequently, LASIK has become the most commonly performed keratorefractive surgery. Other keratorefractive procedures to correct low to moderate myopia 6

15 Jouspevdujpo!up!sfgsbdujwf!tvshfsz!jo!dijmesfo include variations of PRK called laser epithelial keratomileusis (LASEK) and epi-lasik, insertion of intrastromal corneal ring segments and radial keratotomy (RK) (Rapuano et al., 2001). An advantage of surface ablation techniques compared with LASIK is that more residual posterior corneal stromal tissue is preserved and there are no stromal flap-related complications. Disadvantages of surface ablation techniques when compared with LASIK include more discomfort and slower recovery of vision due to the longer re-epithelialization time and potential development of subepithelial haze (Shortt et al., 2006). Intraocular refractive surgery: Most refractive surgeons agree that safety and accuracy of keratorefractive surgery declines in eyes having more than 10 D of myopia or 4D of hyperopia. For these patients, intraocular lens surgeries may be an option. Phakic Intraocular Lenses (PIOLs) are available to treat myopic eyes up to 20D. PIOLs are an additive concept procedure in which an artificial lens is placed in the eye in addition to the crystalline lens (Kamiya et al., 2008). Clear lens extraction (CLE) may be an option. The natural crystalline lens is removed using traditional cataract phacoemulsification techniques with an intraocular lens placed in the eye to significantly reduce or eliminate the refractive 7