Presentation on theme: "Dr. Habes Batta Pediatric Ophthalmic Consultant and Strabismologist."— Presentation transcript:
Dr. Habes Batta Pediatric Ophthalmic Consultant and Strabismologist
The correction of aphakia differs between children and adults Myopic shift. Immature visual systems - risk of developing amblyopia More postoperative inflammatory response after the Sx.
ANATOMY During early childhood, the refractive elements of the eye undergo radical changes. At birth the cornea has refractive power ~ 52D in preterm infants and ~ 48.0 D in term infants. At age 18 months, the cornea has refractive power ~ 43.5D. From this age on the curvature of the cornea remains about the same. The crystalline lens undergoes a reduction in its power during early childhood until age of 6 yrs.
ANATOMY The most important change - axial elongation. At birth the mean AxL = 17.0 mm. The first phase 0-2 years of life, AxL increasing ~ 4.4 mm. The second phase 2-6 years, AxL increasing ~ 1.5 mm. The last phase 6-13 yrs, AxL increasing ~ 1.0 mm.
AMBLYOPIA Animal experiments have shown that visual deprivation during a “sensitive period” results in anatomic changes in the visual cortex. These changes result in amblyopia. The sensitive period in humans extends up to 7 years of age. Because of the visual inattention of infants during early infancy, visual deprivation during the first 6 weeks of life appears to have no lasting consequences. However, after this 6-week “grace period,” even short intervals of visual deprivation can have profound effects on the development of the central visual pathways.
AMBLYOPIA Earlier visual deprivation - more severe amblyopia. Unequal stimulation of the two eyes - damaging the development of the central visual pathways. Unilateral cataract or unilateral uncorrected aphakia - profound effects on the visual development of the deprived eye. The need to provide equal visual stimulation - important considerations when trying to decide how best to correct a child's eye optically.
INTRAOCULAR LENSES Numerous studies have shown improved visual outcomes in age- matched children corrected with IOLs versus contact lenses. Ben Ezra and coworkers reported that 65% of children with unilateral cataracts were able to see 20/40 or better after cataract surgery and IOL implantation, compared with only 35% of eyes corrected with contact lenses. Similarly, Greenwald and Glaser reported 20/40 or better visual acuity in 75% of children 2 years of age or older after cataract surgery and IOL implantation, compared with 48% of eyes corrected with contact lenses.
The improved visual outcome associated with IOLs - related to the constancy of the optical correction. Pseudophakic children have been reported to have superior binocularity and a lower incidence of subsequent strabismus than children corrected with contact lenses.
Convenience of IOLs. Contact lenses require amount of care. IOLs also provide a constant correction, whereas even the most compliant child will have periods of time when the contact lens cannot be worn because of an ocular infection or a lost or damaged lens. IOL provides an immediate optical correction after implantation, whereas a delay of several days or even weeks often occurs before contact lenses or glasses are dispensed. IOLs, unlike contact lenses, are not associated with ongoing expenses.
There is a controversy regarding the optimal technique for IOL implantation in a child's eye. A child's eye differs in several significant ways from an adult eye. Opacification of the posterior lens capsule after cataract surgery. PCO can occur a few weeks after cataract surgery or years later. In older children, the posterior capsule is frequently left intact at the time of cataract surgery and opened with a Nd:YAG laser when opacification occurs. Alternatively, a primary posterior capsulotomy will be created with anterior vitrectomy.
The type of IOL implanted may also affect the incidence of posterior capsule opacification. IOLs that create a symmetric radial stretch of the posterior capsule may increase the contact between the convex IOL surface and the posterior capsule, thereby creating a barrier to the central migration of epithelial cells. Acrylic lenses may be associated with both a lower incidence and a delayed onset of posterior capsular opacification. Possible reasons for the lower incidence of posterior capsular opacification with acrylic lenses include the square edge of the lens, greater biocompatibility, and increased capsular adherence. Finally, heparin-surfaced modified PMMA lenses have been reported to reduce the cellular deposits on IOLs in a child's eye.
Children are more likely to traumatize their eye after cataract surgery. Superior incision has the advantage over a temporal incision of allowing the brow to protect the incision site. A sutureless incision is inappropriate in children.
POWER OF THE IO L If an IOL --- < 6 years of age, the ongoing axial elongation in the presence of a relative stable corneal curvature means that a myopic shift will occur.
POWER OF THE IOL A variety of approaches have been used to compensate for the myopic shift that occurs in pediatric eyes after IOL implantation. IOL power is chosen that initially undercorrects a child's eye --------- Because genetic factors also influence axial elongation, they should also be factored into the decision as to what IOL power to implant.
CONTRAINDICATIONS TO IOL IMPLANTATION Active uveitis is an absolute contraindication. Microphthalmia.
CONTRAINDICATIONS TO IOL IMPLANTATION Anterior chamber IOLs may result in corneal endothelial decompensation or chronic inflammatory changes of the uveal tract over time. Scleral fixation IOLs! The sutures may in time erode either through the conjunctiva, resulting in endophthalmitis, or through the sclera, resulting in subluxation of the IOL.
CONTACT LENSES The treatment of choice in infants with bilateral aphakia and in children of all ages with active uveitis or inadequate capsular support. PediaBausch & Lomb SilSoft contact lenstric
Contact lenses have several distinct advantages over IOLs as a means of correcting aphakia in children. The power of the contact lens can easily be adjusted as a child's eye elongates – particularly during the first 2 years of life. To treat infants with a contact lens immediately after cataract surgery and then to implant an IOL after age of 2 yrs.
In recent years, rigid gas-permeable contact lenses have become increasingly popular as a means of correcting aphakia in children because of 1. Their lower cost, 2. Their availability in a greater range of powers, 3. Their ease of insertion and removal. Bausch & Lomb SilSoft contact lens ------. Keratometry readings can be taken during surgery to facilitate the fitting of these lenses.
Contact lenses can be associated with a good visual outcome even in children with unilateral aphakia. Unfortunately, many children with unilateral aphakia have a poor visual outcome when corrected with contact lenses because of the time and constancy required for their use.
GLASSES Rarely used to correct aphakia in children. For children with bilateral aphakia who are intolerant of contact lenses. For the microphthalmic eyes - magnifying the apparent size of the eyes. Although compliance is generally better with glasses than contact lenses, some children who are developmentally delayed may object to their use.
Glasses are still commonly used even in pseudophakic or contact lens-corrected children to provide a near correction. The IOL or contact lens is used to provide the distance correction and the bifocal segment for the near correction. Bifocals are typically prescribed when children are 18 months to 3 years of age. Multifocal IOLs may reduce the future need for glasses for pseudophakic children. However, the factor limiting their use in children is again the axial elongation that occurs, which would make it difficult to make these children free of spectacles.
CONCLUSIONS During the last decades, the optical correction of aphakia in children has changed radically from contact lenses to IOLs. Superior visual outcomes have been achieved with IOLs so that many aphakic children can now live nearly normal lives. However, implanting an IOL in a child's eye differs from implanting an IOL in an adult's eye. Further studies will be necessary to determine whether multifocal IOLs should be used to correct aphakia in infants and children.
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