|Year : 2019 | Volume
| Issue : 2 | Page : 94-96
Superior Segmental Optic Nerve Hypoplasia Presenting With Exotropia and Nystagmus – Case Report
Sowmya Raveendra Murthy MS, FMRF, FAICO, Consultant 1, Khushboo Gupta2, Nivedhitha Nikhil2
1 Department of Pediatric Ophthalmology and Strabismus, Bengaluru, Karnataka, India
2 Sankara Eye Hospital, Bengaluru, Karnataka, India
|Date of Submission||03-Jul-2018|
|Date of Decision||10-Oct-2018|
|Date of Acceptance||11-Oct-2018|
|Date of Web Publication||07-Feb-2020|
Dr. Sowmya Raveendra Murthy
Pediatric Ophthalmology and Strabismus, Sankara Eye Hospital, Varthur Main Road, Kundlahalli Gate, Bengaluru, 560035, Karnataka
Source of Support: None, Conflict of Interest: None
Superior segmental optic nerve hypoplasia (SSONH) is a developmental disorder of the disc with unclear pathogenesis causing inferior altitudinal field loss. Dissociated vertical deviation (DVD) usually occurs with unequal visual input owing to early strabismus like infantile esotropia. Occurrence of DVD in a case of SSONH as a presenting complaint has never been reported earlier. We report a case of a young boy with SSONH presenting with exotropia and DVD. Our case shows the occurrence of dissociated strabismus like DVD in child with inferior altitudinal field loss owing to SSONH which is noted as a rare association
Keywords: Altitudinal field loss, dissociated vertical deviation, nystagmus, superior segmental optic nerve hypoplasia
|How to cite this article:|
Murthy SR, Gupta K, Nikhil N. Superior Segmental Optic Nerve Hypoplasia Presenting With Exotropia and Nystagmus – Case Report. Niger J Ophthalmol 2019;27:94-6
| Introduction|| |
SSONH is a congenital optic nerve anomaly characterized by localized inferior visual field defects, superior nerve fiber layer defects, and good visual acuity. Relative superior entrance of the central retinal artery, pallor of the superior optic disc, superior peripapillary scleral halo, and thinning of the superior retinal nerve fiber layer are characteristics of SSONH.,, Strong association with maternal diabetes is established. The proposed etiology is a selective defect in the development of the superior retinal ganglion cells or axons early in gestation due to unknown mechanisms.
DVD is an enigmatic strabismic condition consisting of an upward excursion, excyclotorsion, and outward deviation of the nonfixing eye. DVD usually affects both the eyes, but can also occur unilaterally or asymmetrically. Most commonly, it occurs with latent or manifest-latent nystagmus and infantile esotropia. Exotropias and vertical deviations may also be associated with it.
Association of DVD with early-onset strabismus has been reported; its association with congenital optic nerve hypoplasia has rarely been reported.
| Case History|| |
A 14-year-old boy presented with history of squinting since early childhood. Best corrected Visual acuity in both eyes of 6/9, N6 with presence of latent nystagmus was noted. Alternate prism cover tests showed exophoria with DVD (dissociated vertical deviation) of 16 prism diopters (pd) in right eye and 9 pd (left eye) for distance and near [Figure 1]. Ocular movements showed inferior oblique over action +1 in right eye. Fundus examination showed minimal superior shift of vessels with slight temporal pallor of disc in both the eyes. Optical coherence tomography (3D OCT maestro machine from Topcon manufacturer) showed optic nerve hypoplasia with thinning of neuroretinal rim in superior, inferior, and temporal quadrants in right eye and superior and temporal quadrants in left eye [Figure 2]. Visual fields with Humphrey visual field analyzer showed inferior altitudinal defect in both the eyes [Figure 3] confirming diagnosis of SSONH. There was no history of maternal diabetes.
|Figure 1 Case photographs showing primary gaze orthotropia (upper figure), dissociated vertical deviation in the right eye (middle figure), and left eye (lower figure).|
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|Figure 2 Spectral OCT of optic nerve head showing thinning of NFL superiorly, inferiorly, and temporally in right eye along with thinning of NFL superiorly and temporally in left eye. NFL, nerve fiber layer; OCT, optical coherence tomography.|
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|Figure 3 Visual fields (Humphrey 30-2 program) showing inferior visual field defects in both the eyes.|
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The prisms were used to expand the visual fields but the patient did not find it beneficial.
| Discussion|| |
Isolated SSONH with an inferior visual field defect is a form of segmental optic nerve hypoplasia. Segmental hypoplasia is placed under group 2 of Skarf and Hoyt classification of optic nerve hypoplasia., The inferior visual field loss with relative pallor of superior disc and good vision are characteristics of SSONH. The occurrence of maternal gestational diabetes is established but reports of SSONH even in its absence also exist. There are few reported cases of SSONH, of which none have documented any association other than gestational diabetes and corresponding OCT and field changes.
Oculomotor adaptations from visual field loss, such as hemianopia, have been described. Exotropia may occur in presence of homonymous or heteronymous visual field loss probably as a compensatory phenomenon.,, Presence of exotropia in the direction of visual field defect enlarges the visual field in homonymous hemianopia cases, whereas heteronymous field loss like bitemporal hemianopia disrupt binocularity and failure to generate corrective vergence saccades and thus may promote decompensation of vertical phoria.
Our case showed DVD in presence of inferior field loss − a rare occurrence.
Brodsky proposed DVD to be a dorsal light reflex that occurs when early-onset strabismus precludes the development of normal binocular vision. So, the pathology for DVD is the disruption of binocular vision as in infantile esotropia. Latent nystagmus in infantile esotropia is also attributed to same pathology of unequal visual input disrupting binocular visual development. We propose DVD to have possibly occurred as compensation to inferior field loss − a causal association. Inferior visual field loss leading to unequal visual inputs disrupting binocular vision and thus causing DVD is proposed.
Inferior altitudinal field loss disrupts binocularity and loss of vertical vergence saccades leading to decompensation ofvertical phorias, and thus leading to DVD is suggested. This may be akin to heteronymous hemianopias causing decompensation of heterophorias. Unequal visual input as in strabismus cases causing DVD has been an accepted mechanism, but our case goes on to suggest occurrence of DVD due to inferior altitudinal field loss as in our patient.
Further the occurrence of latent nystagmus in our case also supports this hypothesis of early binocular disruption by visual field loss as causal factor for DVD. Our case also showed latent nystagmus with DVD but in the presence of SSONH and corresponding visual field loss.
Latent nystagmus and DVD are signs of disruption of vision in early life, often noted with infantile esotropia and other causes.
In conclusion, DVD with latent nystagmus and exotropia warrant detailed evaluation with visual fields to find causes of disruption of vision in early life.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]