Australian and New Zealand Journal of Ophthalmology 1988; 16: 45-48

SINGLE-EYED INFANTILE ESOTROPIA-ABDUCTIONAL NYSTAGMUS SYNDROME (UNILATERAL CONVERGENT SQUINT FOLLOWING ENUCLEATION)

ARVIND KUMAR DUBEY YS, WMS

SAVlTA YADAV ms Eye Surgeon, Bhopal (M P j

Lecturer in Ophthalmology and Consultant Eye Surgeon. Government Medrcal College and Hosprlal, Jabalpur (M P J

~ ~~ ~~ ~~ ~

Abstract Three infants underwent enucleation of one eye for different indications. This was followed by the develop ment of esotropia of varying degree within one to four months in a// the three cases, and was associated with a coarse nystagmus present in abduction, but absent in the primary and adducted positions of gaze. There was a face turn to the side of remaining eye. This appears to be a separate clinical entify and nor early onset esotrapia. Possible mechanisms and medicolegal implications are discussed.

Key words: lnfantile esotropia. abductional nystagmus, enucleation.

Three cases are reported in which one eye was removed during infancy. In all three cases an internal deviation of the remaining sound eye developed within one to four months after enucleation. Nystagmus developed in all cases, either with the onset of esotropia or a little later. Nystagmus appeared only in abduction and was absent in the primary and adducted positions of gaze. Helveston reported a similar series.’ Monocular esotropia with abductional nystagmus appears to be a definite clinical entity separate from congenital esotropia. Possible mechanisms and medico-legal significance are discussed.

CASE 1 A 5%-month-old boy was brought to us for “an abnormally large” right eye. A diagnosis of congenital glaucoma was established. The eye was blind, the cornea was insensitive and hazy,

and there was a staphyloma including the ciliary region.

The child was born at 8% months’ gestation, following a normal pregnancy and delivery. He was the couple’s first child. There were no other congenital abnormalities.

Consent for removal of the child’s right eye was obtained and the eye was enucleated under general anaesthesia. A cosmetic shell was provided to keep the fornices open and to avoid socket contracture.

Forty-five days after enucleation the left eye was found to be adducted by 12 to 15 degrees. On detailed examination of anterior and posterior segments, the left eye was found to be normal in all respects. There was no limitation of ocular movements; face turn and nystagmus were not present at this stage. Refraction of the left eye was normal for the age of child.

Reprint requests: Dr A. K. Dubey, Lecturer, Eye Department, Medical College, Jabalpur (M.P.), India.

SINGLE-EYED INFANTILE ESOTROPIA-ABDUCTIONAL NYSTAGMUS SYNDROME 45

Within the following month the deviation increased to about 25 degrees. Ocular movements were unrestricted but coarse nystagmus appeared on abduction, and there was a face turn to the left. Nystagmus was absent in the adducted and primary positions of gaze, the fast component being to the left.

When last seen the child was 18 months old and squint surgery was refused by the parents.

CASE 2 A 3!4-month-old girl was brought to us with a perforating injury of the left eye. The left eye was collapsed, had a large corneal laceration, expulsion of lens and vitreous and bleeding from weal tissue. Enucleation was performed under general anaesthesia. The right eye was found to be normal.

Four months later, the right eye was esotropic and there was a face turn to the right. Nystagmus appeared on abduction and was absent in the primary and adducted positions of gaze.

CASE 3 A 7-month-old child was sent to us from a peripheral clinic with a ‘white pupillary reflex’ in his right eye. On external examination the right eye appeared blind. A fundus examination was conducted under general anaesthesia. The retina was found to be completely detached with a hazy vitreous. New vessels could be seen on the detached retina. The left eye showed no abnor- mality on detailed examination of anterior and posterior segments. The right eye was removed and a diagnosis of retinoblastoma was confirmed by histopathological examination.

By the age of 11 months the left eye became convergent by about 18 degrees. Head posture was normal and no nystagmus was found at this stage. Detailed examination of the fundus and anterior segment revealed no abnormality. Ocular movements were unrestricted.

The child was regularly followed up and a detailed examination was performed on each occasion to rule out any signs of retinoblastoma. At 13 months of age the deviation increased to about 30 degrees with a face turn to the left. Nystagmus appeared on attempted or induced

abduction. The child is now 18 months old and the deviation has progressed no further.

DISCUSSION The mechanism of this uniocular esotropia with abductional nystagmus remains open to specu- lation. Among the various causes of early on% esotropia, ‘Nystagmus blockage syndrome’ has been discussed prominently in the 1iterature.I In classical ‘nystagmus blockage syndrome’ nystagmus appears on attempted abduction of either eye, and there is a head turn in the direct- ion of the uncovered eye when the fellow eye is occluded. The diagnosis of nystagmus blockage syndrome is based on the appearance of nystagmus on attempted abduction, of either eye, on head turn in the direction of the uncovered eye when the fellow eye is occluded, on straightening of the eyes under surgical levels of general anaesthesia, and on the appearance of nystagmus during the induction phase. In this syndrome convergence and optimal visual acuity for near sight help to steady fixation, because visual acuity is best in the position of adduction and falls as nystagmus develops in the abducting eye. The patients reported here are all uniocular, and did not show all the features of this syndrome.

Duane’s retraction syndrome with esotropia was considered as another possibility, but other features of this condition were absent, and there was no other ocular lesion or systemic malform- ation in any of the case^.^-^ Sixth nerve palsy could not be the explanation as the ocular move- ments were un re~ t r i c t ed .~ Retinoscopic estimation was normal for the age, and ‘accom- modative esotropia’ was ruled

Worth8 championed the idea that “the essen- tial cause of squint is a defect in fusion faculty and indeed a congenital total absence of the fusion faculty”. One must admit that this concept of “total absence of fusion faculty” is not convincing. However, interference with fusion may precipitate a tropia. This interference may be central or peripheral, may be motor or sensory. In the cases reported here there is total loss of input from one eye which could be an explanation for esotropia, but the characteristic

46 AUSTRALIAN AND NEW ZEALAND JOURNAL OF OPHTHALMOLOGY

abductional nystagmus remains unexplained. Other patients of a similar age who have retained the blind eye beyond 2 to 3 years of age never show a nystagmus of this kind. It is logical that some other mechanism besides a fusion deficit could be involved.

Chavasse9 considered fusion as an overt motor response of the eyes based on conditioned reflexes acquired by usage. A central or peripheral obstacle in the development of binocular reflexes causes a perversion expressed in deviation of the visual axes. The patients reported herein definitely represent gross inter- ference with the fusion mechanism, but this does not explain the nystagmus absent in adduction and present in abduction.

Keiner’” in agreement with Zeeman” stated that optomotor reflexes determine the relative position of the eyes in the course of postnatal development. They indicated a monocular duction reflex grafted upon proprioceptive reflexes, a binocular reflex for version grafted upon vestibular pathway and a convergence pathway also grafted upon a proprioceptive reflex pathway. They give primacy to the opto- motor rather than to the sensory system in normal and abnormal evolution of binocular CO-

ordination. Asymmetric optokinetic nystagmus and abnormal vestibulo-ocular reflexes are known to result from interference with opto- motor reflexes, which in turn may induce an early esotropia in the interest of ocular stability and optimal near point visual

In the cases reported herein esotropia, rather than nystagmus, was the primary event. The cases were monocular, and nystagmus had a characteristic appearance and accentuation on abduction. However, that the loss of one eye in very early childhood could give rise to visual nerve fibre defects is tenable. Thus, early onset esotropia can be explained by any of the above proposals, but the abductional nystagmus cannot.

If this was latent nystagmus,I4 it should have been present at the very first presentation, because latent nystagmus appears immediately on occlusion of one eye. Esotropia and nystagmus appeared in our cases weeks to

months after enucleation, either simultaneously or one following the other.

Helveston’ speculated that the presence of a blind eye will have a stabiIising effect on the neuro-muscular apparatus of the sound eye; that is, the normal eye is neurologically ‘yoked’ to a muscle in the enucleated orbit, which has assumed an abnormal relationship to the orbital contents which lack a globe. These views are based on the observation that removal of a microphthalmic eye even at an age earlier than four months has not resulted in esotropia with nystagmus, because a normal “yoke muscle” relationship was never present. It has been our observation that removal of a blind eye in children aged two years or older has not resulted in such “esotropia-nystagmus” even if the eye was blind from birth or from very early infancy, ruling out any possibility of sensory fusion. One tends to agree that the mere presence of an intact neuromuscular apparatus of an otherwise blind eye has a steadying effect on the neuromuscular apparatus of the fellow seeing eye in some way, probably by the influence of this “paired rela- tionship” on development and differentiation of vergence-version centres.

It appears that poor visual acuity and the dominant convergence of infancy, together with near point optimal visual acuity may be respon- sible for the esotropia, and that there is a perversion of the vergence mechanism-centre due to absence of the fellow eye. Poor develop- ment of the version mechanism-centre is a likely explanation of the abductional nystagmus in the remaining eye: a relatively untrained neuro- muscular system resulting in loss of control of ocular posture in lateral movements of the globe.

It therefore appears logical to take such presentations as a definite clinical entity different in presentation and aetiology from early onset esotropia. We suggest the term “single-eyed infantile esotropia-abductional nystagmus syndrome”. The characteristic features being appearance of esotropia of the remaining eye within one to four months following enucleation (not mere blindness) of one eye during early infancy, an associated nystagmus either appearing simultaneously or later - the

SINGLE-EYED INFANTILE ESOTROPIA-ABDUCTIONAL NYSTAGMUS SYNDROME 47

nystagmus being present only in induced or attempted abduction and being absent in the primary and adducted positions of gaze with a face turn opposite to the direction of squint.

Medicolegal significance Enucleation of one eye at such an early age is not a common event. There are few indications and patients usually present late in our country. As a result limited reports are available. A similar series was reported by Helveston.’ The signs we have described appear to be a definite clinical syndrome. It is therefore suggested that in such a situation parents should be told about the possibility of deviation of the remaining eye before surgery. Because of its rarity, results of surgical correction of this variety of esotropia have not been evaluated on a large scale and over the long term. This should be borne in mind while dealing with such cases.

CONCLUSION The foregoing discussion imples that indications for enucleation in early infancy should be care- fully weighed against the possibility of “single-eyed infantile esotropia-abductional nystagmus syndrome”. Further, from the view- point of medicolegal implications and also because the mechanism is not yet clear and long- term, large-scale results of surgery are not avail-

able in such cases, animal experiments in this direction are needed.

References 1. Helveston EM, Pinchoff B, EUis FD, Miller K. Unilatm

esotropia after enucleation in infancy. Am J Ophthalmd 1985; 100: 97-99.

2. Burian-Von Noorden’s Binocular vision and Ocula motility 2nd ed. St Louis: C.V. Mosby Co, 1980.

3. Crawford JS. Congenital fibrosis syndrome. Can J Ophthalmol 1970; 5: 331.

4. Cross HE, Pfaffenbach DD. Duanes retraction syndrome and associated congenital malformations. Am J Ophthalmol 1972; 73: 442.

5. Gifford H. Congenital defects of abduction and other ocular movements and their relation to birth injuries. Am J Ophthalmol 1926; 9: 3.

6. Costenbander FD. Infantile esotropia. Trans Am Ophthalmol SOC 1%1; 59: 397.

7. Costenbander FD, Ing M, Bair RV, Parks MM. Symposium Infantile esotropia. Am Orthoptic J 1968; 18: 5.

8. Worth C. Squint its causes pathology and treatment. 6th ed. London: Baillier, Tindall & Cox, 1929.

9. Chavasse F. Worth’s squint or the binocular reflexes and the treatment of strabismus. 7th ed. Philadelphia: P. Blakiston’s son & Co. Inc., 1939.

10. Keiner GBJ. New view points on the origin of squint. The Hague: Martinus Nijoff ND, 1951.

11. Zeeman WPC. Conservative treatment of strabismus. Doc Ophthalmol 1954; 718: 527.

12. Van Hof Van Duin J. Early and permanent effects of monocular deprivation pattern discrimination and visuomotor behaviour in cats. Brown Res. 1976, 111: 261.

13. Flynn J. Vestibulo-optokinetic interactions in strabismus. Am Orthoptic J 1982;.32: 36.

14. Forssman B. A study of congenital nystagmus. Acta Otolaryngol 1964; 57: 427.

15. Vander Hoeve J. Nystagmus latent. Ann Ocul 1971; 154: 738.

XXVI INTERNATIONAL CONGRESS OF OPHTHALMOLOGY

The XXVI International Congress of Ophthalmology will be heId in Singapore from 18-24 March 1990. Ophthalmologists and exhibitors may request details by writing to:

The Congress President, Dr Arthur S. M. Lim, C / o Department of Ophthalmology, National University Hospital, Lower Kent Ridge Road, Singapore 05 1 1, Republic of Singapore.

48 AUSTRALIAN AND NEW ZEALAND JOURNAL OF OPHTHALMOLOGY