Lenses For Congenital Ocular Conditions
By Melanie Frogozo, OD
Emmetropization is the process by which refractive errors are gradually reduced toward emmetropia or low hyperopia through normal ocular growth during childhood (Troilo, 1992). Degradation of retinal image quality early in life due to ocular disease disrupts emmetropia. Consequently, children who have visual impairment from congenital ocular conditions often have significant refractive errors such as high myopia, astigmatism, and anisometropia (Vincent, 2017). Given the wide range of refractive errors associated with pediatric ocular conditions, contact lens correction in childhood can provide improved visual acuity and an expanded field of view. It also can positively influence self-esteem, self-worth, confidence, and social acceptance (Dias et al, 2013).
Pathological myopia is associated with degenerative posterior segment changes as a result of excessive ocular growth. Such high levels of myopia are typically present at birth or early in life. It may occur in isolation or with other ocular conditions such as albinism, retinopathy of prematurity, and retinitis pigmentosa. Reduced visual acuity in high myopia typically occurs due to excessive axial elongation, which may result in retinal stretching and detachment, photoreceptor reorganization, and chorioretinal atrophy (Saw et al, 2005). Minification of the retinal image due to spectacle correction also may contribute to reduced visual acuity.
The use of contact lenses to correct pathological myopia provides a larger field of view and a greater field of fixation, because contact lenses move with the eye. Visual acuity also may be improved by one to two lines with contact lens correction because of larger retinal images or less spectacle lens minification (Vincent, 2017).
In cases of nystagmus, contact lenses are the preferred optical correction, as the refractive correction moves with the eye (Allen and Davies, 1983). Additionally, contact lens wear reduces the amplitude and frequency of the nystagmus in some patients, potentially by providing some tactile or proprioceptive feedback about eye movements (Taibbi et al, 2008).
Several congenital ocular conditions (e.g., albinism, aniridia, cone dystrophies) cause anatomical anomalies that result in extreme photosensitivity. These conditions are often associated with significant spherical or astigmatic refractive error, which can also be incorporated into a therapeutic tinted contact lens (Vincent, 2017).
For example, one 17-year-old female had a history of retinopathy of prematurity, pathological myopia, and nystagmus. Additionally, she experienced constant light sensitivity. Her manifest refraction was –20.00D in the right eye and –16.00D in the left eye and was corrected to 20/200 and 20/70, respectively, with spectacles. This patient was fitted into high-minus soft contact lenses with an amber tint (Figure 1) that relieved her light sensitivity and also improved her visual acuity to 20/100 and 20/50 in the right and left eyes, respectively. There was also a noted decrease in the frequency of her nystagmus with contact lens correction.
Figure 1. Custom high-powered contact lenses can be designed to help children who have congenital ocular conditions causing pathological myopia and photosensitivity.
Contact lens management of children who have congenital ocular conditions can offer significant improvements in visual acuity, field of vision, and visual comfort. When prescribed as an alternative to a high-prescription spectacle correction, contact lenses can also be of significant psychosocial benefit by enhancing cosmesis and self-confidence.
Contact Lens Spectrum, Volume: 34, Issue: June 2019, page(s): 45
For references, please visit www.clspectrum.com/references and click on document #283.