Pediatric and Teen CL Care
High Myopia in Childhood
By Christine W. Sindt, OD, FAAO
Myopia is often regarded, by both practitioners and parents, as a benign condition that is the destiny of children with myopic parents. Myopia in very early childhood, however, is rare, with only 4 percent to 6 percent of full-term infants and 2 percent to 3 percent of preschool children suffering from nearsightedness (Cook and Glasscock, 1951; Laatikainen and Erkkila, 1980). Of those children, even fewer suffer from high myopia (>6.00D). Yet, high myopia should be of concern because it is associated with systemic diseases and other ocular findings.
Associated Systemic Diseases
In a study by Marr et al (2001), anisometropia (>2.00D) and refractive amblyopia were found in 32 percent of high myopia cases; 17.9 percent of high myopes suffered from strabismus and 12.5 percent from nystagmus. Additional ocular abnormalities found included microphthalmos, aniridia, spherophakia, posterior lenticonus, persistent pupillary membrane, coloboma, morning glory disc, glaucoma or ocular hypertension, retinal detachments, cone dystrophy, congenital stationary night blindness, ocular albinism, and Stargardt disease.
The study noted that 11.7 percent of these children will suffer severe developmental delays.
Marr et al also found that 53.5 percent of early childhood high myopes have associated systemic disease. Stickler syndrome, Down syndrome, and Marfan syndrome are the most common.
Stickler syndrome is a progressive autosomal-dominant connective tissue disorder with many ocular and systemic manifestations. Ocular abnormalities include retinal detachment (60 percent), glaucoma (5 percent), premature cataracts, high myopia, optically empty vitreous cavities, and retinal pigmentary changes. Associated systemic signs include premature osteoarthritis (75 percent), hearing loss (25 percent), and skeletal and facial malformations such as maxillofacial hypoplasia, cleft palate (25 percent), and mitral valve prolapse (45 percent) (Bowling et al, 2000; Liberfarb and Goldblatt, 1986; Couchouron and Masson, 2011).
Stickler syndrome has an incidence of about 1:7500 births, with several subtypes depending on associated findings (Couchouron and Masson, 2011). This condition is autosomal dominant, so it is wise to refer parents to receive genetic counseling.
Correction of Choice
Contact lenses are the vision correction of choice for high myopes. Glasses may cause prismatic effects, minification, image degradation secondary to spherical aberration, and aniseikonia.
The minification amount depends on the refractive error and vertex distance. The stronger the minus lens, the smaller the image projected to the retina. Contact lenses may increase the image size by 20 percent. The prismatic effects and spherical aberration of spectacle correction are eliminated with contact lenses because the optical axis of the lens moves with the visual axis of the eye.
Convergence required for binocular fixation at near is less with minus glasses than with contact lenses; theoretically, this could increase the symptoms of near strain in myopic lens wearers who have convergence insufficiency (Curtin, 1985). Similarly, an increased amount of accommodation is needed when going from spectacles to contact lenses. However, reduced minification and decreased prismatic effect far outweigh the potential of increased accommodative demand and increased convergence at near for high myopes.
Contact lenses are the treatment choice for progressive high myopes. Be sure to make appropriate referrals for work up of potential systemic disease or developmental delays. CLS
For references, please visit www.clspectrum.com/references.asp and click on document #201.
|Dr. Sindt is a clinical associate professor of ophthalmology and director of the contact lens service at the University of Iowa Department of Ophthalmology and Visual Sciences. She is the past chair of the AOA Cornea and Contact Lens Council. She is a consultant or advisor to Alcon Vision Care and Vistakon and has received research funds from Alcon. You can reach her at email@example.com.|