Management of Congenital Nystagmus with and without Strabismus

Abstract

Congenital nystagmus consists of involuntary periodic to-and-fro oscillations of the eye, which are usually horizontal and present within the first 3 months of life. Congenital nystagmus can be idiopathic or occur in association with defects in the afferent visual system such as albinism, congenital retinal dystrophies or congenital retinal dysfunction disorders (such as achromatopsia and congenital stationary night blindness (CSNB)), congenital optic atrophy, optic nerve hypoplasia, and congenital cataracts. Congenital nystagmus need to be differentiated from manifest latent nystagmus (MLN) and congenital periodic alternating nystagmus (PAN) as the management of these conditions differs. Several compensatory mechanisms exist in congenital nystagmus, which tend to decrease the nystagmus and thus improve the visual acuity. These mechanisms need to be analyzed carefully because their understanding is important for the patient's management. Various modes of management are available for patients with congenital nystagmus such as optical, medical, and surgical treatment. A combination of treatment options might be helpful to achieve the best outcome. The incidence of significant refractive errors in patients with congenital nystagmus is around 85%. Hence, correcting refractive errors improves visual acuity and is important at an early age to prevent ambylopia. Optical treatment can involve spectacles, contact lenses (CL), or low visual aids. Recently, medical treatment for congenital nystagmus with memantine and gabapentin has been shown to reduce nystagmus intensity and to increase visual acuity. Baclofen is beneficial in the management of congenital PAN. Surgery in congenital nystagmus is used to correct the anomalous head posture (AHP) and to dampen the nystagmus. For Anderson—Kestenbaum- like procedures various extents of surgery have been proposed by different surgeons. However, if the head turn is significant, only limitation of motility due to a large extent of surgery will correct the head turn. If the patient has a squint, care needs to be taken that Anderson—Kestenbaum-like procedures are performed on the dominant or fixing eye. Strabismus correction is best planned during the same surgical session on the non-fixing eye. Surgery causing artificial divergence (exophoria) is beneficial in patients with binocular vision and damping of nystagmus on convergence. Combination of Anderson—Kestenbaum-like procedures and artificial divergence surgeries have been shown to be beneficial. Recently, tenotomies of extraocular muscles have been advocated for dampening nystagmus and for increasing the null region. However, the exact mechanism is not fully understood and further studies are needed.