RESUMO
Keratoconus is a progressive corneal disease characterized by bilateral yet usually asymmetric thinning of the cornea with an onset typically in teenage years. While it often presents as an isolated condition, keratoconus may also be associated with many systemic and/or ocular diseases, such as connective tissue and chromosomal disorders. Its association with nystagmus has been described in Leber's congenital amaurosis, where patients also exhibit abnormal pupillary responses, early-onset retinal dystrophy, mental developmental delays, and eventual blindness. The case described here, however, was a high-functioning teenager with keratoconus and infantile nystagmus, and oscillopsia on left gaze and a compensatory head turn to the patient's left. The initial distance visual acuities of 20/60 and 20/150 in the right and left eye, respectively improved to 20/25 and 20/40 by the use of corneal rigid gas permeable contact lenses. In addition, the patient's neck strain and overall gait were eased by yoked prism spectacles.
RESUMO
This study investigated in-vivo changes of peripheral refraction with commercially available single vision and multifocal soft contact lenses, utilizing different designs and various corrective power values. Starting at the fovea, wave-front aberrations were measured up to 30o nasal retinal eccentricity, in 10o increments, using a commercially available Shack-Hartmann aberrometer. Three different types of contact lenses were fitted in an adult subject's right eye: Acuvue Oasys Single Vision (ASV), Proclear Multifocal D with 2.50 diopters (D) add power (PMD), and ArtMost SoftOK (SOK). Each lens type was fitted in corrective power values of -2.00 D, -4.00 D, and -6.00 D. Refractive errors were computed in power vector notation: The spherical equivalent (M), the Cartesian Jackson-Cross-Cylinder (J0), and the oblique Jackson Cross Cylinder (J45) from measured second order Zernike terms. Acuvue Oasys Single Vision lenses produced a slight myopic shift at 30o retinal periphery (-0.32 D ± 0.05) without significant differences between the various lens power values. Proclear Multifocal D lenses did not create clinically significant myopic shifts of at least -0.25 D. All SOK lenses produced clinically significant relative myopic shifts at both 20o (-0.61 D ± 0.08) and 30o (-1.42 D ± 0.15) without significant differences between the various lens power values. For all lens types and power values, off-axis astigmatism J0 was increased peripherally and reached clinical significance beyond 20o retinal eccentricity. The increased amount of off-axis astigmatism J0 did not show a significant difference for the same type of lenses with different dioptric power. However, at 30o retinal eccentricity, SOK lenses produced significantly higher amounts of off-axis astigmatism J0, compared with ASV and PMD lenses (SOK versus ASV versus PMD: -1.67 D ± 0.09, -0.81 D ± 0.07, and -0.72 D ± 0.15). Both ASV and SOK lenses showed no clinically significant differences in the amount of introduced astigmatic retinal image blur, with various lens power values. Proclear Multifocal D lenses showed a systematic increase of astigmatic retinal image blur with an increase of add power. At 30o retinal eccentricity, -6.00 D SOK lenses introduced 0.73 D astigmatic retinal image blur, while PMD and ASV lenses introduced 0.54 D and 0.37 D, respectively. In conclusion, relative peripheral refractions, measured in-vivo, were independent of the contact lenses central corrective power. The SOK contact lenses demonstrated a stronger capability in rendering relative peripheral myopic defocus into far periphery, compared to the other lens designs used in this study. This was accompanied by higher amounts of introduced astigmatic retinal image blur.
