Content area
Full Text
Introduction
Amblyopia, the most common cause of unilateral visual impairment in children, is defined as a unilateral or bilateral decrease in best-corrected visual acuity without organic cause secondary to either visual deprivation or abnormal binocular interaction. 1-3 The incidence of amblyopia varies between 0.5% and 3.5%. 4 5 The three main subtypes of amblyopia are: strabismic, anisometropic and form-vision deprivation. 6 Functionally, the amblyopic eye is suppressed, resulting in a loss of binocular function at the level of the binocular neurons in the visual cortex. 5 7 8 The histopathological changes in several animal models included cell shrinkage in the layers of the lateral geniculate nucleus that received stimuli from the amblyopic eye with corresponding changes in the visual cortex. 9-11 Similar findings have been found in the lateral geniculate nucleus in human amblyopia. 12 13 Retinal involvement in the amblyopic process is controversial: electroretinograms (ERG) were significantly reduced in one study 14 ; other investigators did not observe this deficit. 15 Lempert identified optic-disc hypolplasia associated with presumed amblyopia. 16
Optical coherence tomography (OCT) is a non-invasive, non-contact technique that visualises the retinal structure in vivo with an axial resolution of 10 μm using near-infrared interferometry. Retinal nerve fibre layer thickness (RNFLT) measured by OCT corresponds to RNFLT measured histologically. 17 Salchow et al obtained high-quality RNFL measurements in children 4 years of age and older. 18 More recently, spectral-domain OCT (SD-OCT) as compared with the time-domain OCT (TD-OCT) scans more data points and involves less interpolation. 19
TD-OCT has been utilised to study RNFL and less commonly macular thickness in amblyopic eyes. To date, the literature has shown conflicting results ( table 1 ). Yoon et al and Yen et al found a thicker RNFL in eyes with anisometropic amblyopia. 4 20 Altintas et al , Repka et al and Kee et al found no difference in the thickness of the macula and RNFL in amblyopic children. 5 7 21 24 More recently, Huynh et al showed a thicker fovea in amblyopic children, 22 while Bui Quoc et al found a thicker RNFL in adults with anisometropic amblyopia ( table 1 ). 23
OCT 2000 | Yen, 2004 20 | 38 | Mixed 26.4 years | Strabismus, anisometropia | Increased * in anisometropic ambylopia | Not studied |
OCT 3000 |