Transactions 29th European Strabismological Association Meeting – de Faber (ed) © 2005 European Strabismological Association, ISBN 04 1537 211 9

Long-term binocular functional outcome after strabismus surgery in a case of cyclic esotropia

B. Venkateshwar Rao & Prashant Sahare

Department of Pediatric Ophthalmology and Strabismus, Jasti V Ramanamma, Children’s Eye Care Centre, Hyderabad, India

ABSTRACT:

Introduction: Cyclic esotropia is a rare form of strabismus and poorly understood disorder of ocular motility which is characterized by a regular cycle of squinting and non squinting days. It is typically an acquired form of concomitant non-accomodative strabismus and usually lasts for 48 hours.

Purpose: To report long-term binocular vision outcome after strabismus surgery in a case of cyclic esotropia with 24-hour cyclic pattern.

Methods: Interventional case report.

Results: A healthy 4-year-old female child with alternative day esotropia with 24-hour cyclic pattern that persisted for one year, underwent bimedial rectus recession of 11.0 mm from the limbus through fornix approach. After the surgery the cyclic pattern was abolished with straight eyes at 5 years follow up with normal binocular function as exemplified by fusion on worth 4 dot test and stereopsis of 30 secs of arc with Randot stereotest.

Conclusion: This case highlights the importance of awareness of this rare ocular motility disorder, with need for repeated examinations, to confirm the diagnosis and treat early with surgical intervention, thereby re-establishing the normal binocular vision.

1INTRODUCTION

Cyclic esotropia is a rare form of strabismus and poorly understood disorder of ocular motility which is characterized by a regular cycle of squinting and non squinting days.1 It is typically an acquired form of concomitant non-accomodative strabismus and usually lasts for 48 hours, however there are known cases with cycles that range from 24 to 96 hours in length.1–2 It has been estimated that cyclic strabismus has an incidence of 1 in every 3000 to 5000 cases of strabismus.2 In cyclic esotropia on “straight days” no anomalies of binocular vision are observed, though heterophoria may be present, whereas on strabismic days a large-angle esotropia will appear and sensory anomalies are often found. The mechanism of cyclic strabismus is still unknown, however most cases require strabismus surgery. Surgery based on amount of heterotropia as it occurs on the squinting days has been successful in curing this condition and reestablishing normal binocular function.3 We herein report a case of cyclic esotropia with 24-hour cyclic pattern that persisted for one year. Following a successful bimedial rectus recession, eyes have remained straight with normal binocular vision and the cyclic pattern has been abolished for 5 years follow-up now.

2METHODS

Case report: A healthy 4-year-old female child presented with her parents on 17/07/98 with chief complaints of squinting of her right eye since one year duration every alternate day. There was no previous history of diplopia surgery or any associated trauma. The family history was negative for strabismus. The mother stated that the pregnancy and delivery were normal with no history

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of any use of forceps or birth trauma. The visual acuity at the time of presentation was fixing and following light with central, steady and maintained fixation with each eye. The child was not co-operative for visual assessment with allen pictures. Cycloplegic refraction revealed a hypermetropia of 1.75 Ds in both eyes. Slit lamp biomicroscopy, pupillary reaction and fundoscopic examination were normal in both eyes. Ocular motility examination revealed orthotropia for near and distance (Figure 1) with normal ductions and versions. Patient was not cooperative for stereopsis testing with titmus fly stereotest. Since the parents gave a history of alternate day squinting they were asked to bring the child for examination on the day of crossing.

Patient was reexamined on 18/07/98 and was noted to have 45 prism diopters baseout comitant alternate esotropia, with no fixation preference. (Figure 2) The ductions and versions were normal and there was no associated A or V pattern. A repeat cycloplegic refraction on squinting day revealed hypermetropia of 1.75Ds in both eyes. Based on the above clinical findings a

Figure 1. Cyclic ET. No deviation (Non-squinting day).

Figure 2. Cyclic ET. Large angle constant esotropia (Squinting day).

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presumptive diagnosis of cyclic esotropia was made. The patient was also seen in consultation by a neurologist and found to be neurologically normal. Contrast enhanced computed tomography (CECT) of head and orbits was done and reported as normal. Patient was prescribed glasses and asked to follow up after 4 weeks. Four weeks later when patient presented on 13/08/98 she was orthotropic for near and distance with glasses (Figure 3) and no deviation could be elicited with accomodative target and after repeated alternate cover test. Binocular function testing with titmus fly stereotest revealed presence of gross stereopsis. The following day on 14/08/98 the patient was again re-examined and noted to have 45 prism diopters of esotropia with glasses (Figure 4) both for near and distance which was freely alternating and with normal ductions in both eyes. Stereopsis was absent on testing with titmus fly stereotest. The diagnosis of cyclic esotropia was confirmed and patient was advised eye muscle surgery. A bimedial rectus recession of 11.0 mm from the limbus was done through fornix approach on 07/10/98 which happened to be the nonsquinting day. On the first post operative day, patient was orthotropic for near and distance(Figure 5), with normal versions, and which infact should have been the squinting day according to her cyclic

Figure 3. Cyclic ET. No deviation with glasses (Non-squinting day).

Figure 4. Cyclic ET. Alternating constant esotropia with glasses (Squinting day).

Figure 5. Cyclic ET. First postoperative day showing orthotropia.

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Figure 6a. Cyclic ET. Five year follow-up photograph showing Orthotropia with normal versions.

Figure 6b. Cyclic ET. Five year follow-up photograph showing Orthotropia for distance and near with accommodative target.

nature. Patient is now followed up regularly for nearly more than 5 years and when last seen on 15/12/03 was having unaided visual acuity of 20/20 in both eyes. Ocular motility showed orthotropia for near and distance (Figure 6 a & b) Ductions and versions were normal in both eyes with fusion on worth 4 dot test. Stereopsis was 30 secs of arc on testing with Randot stereotest.

3DISCUSSION

Cyclic strabismus was first mentioned at the strabismus ophthalmic symposium II4 in 1958 and was first described in a publication by Costenbader and Mousel in 1964.2

The onset of this extremely unusual and rare form of esotropia usually occurs at 3 to 4 years of age5, which appears and disappears in a regular cycle. The duration of cycle may be as short as two weeks6 in which case the diagnosis can be missed, or it may persist for several years before becoming a constant deviation7. Our case had a relatively long cyclic phase of approximately one year. Patients with cyclic strabismus usually have a family history of strabismus. There is no sex predilection or relationship to refractive error or visual acuity. The fact that most cases occur in the mid-preschool years may explain the frequency of mild hyperopic error. The effectiveness of correction of hyperopia is unpredictable as well, but it may be reasonable to correct the refractive error and observe the deviation before resorting to surgery. Refractive error in our patient was mildly significant and therefore optical correction was given before surgical correction. Cyclic strabismus must be differentiated from intermittent strabismus, which is more irregular and is often precipitated when the binocular vision is compromised with disruption of fusion.6 Accidental or surgical trauma has been associated with cyclic strabismus in few cases.7,8 Two cases of cyclic esotropia with associated central nervous system lesions has been reported from India.9 Three

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cases of Cyclic esotropia with over-elevation in adduction and V-pattern have been described and treated successfully with bi-medial rectus recession and inferior oblique weakening in one case. 10 Surgical correction of total esotropia with either a bimedial rectus recession or a unilateral medial rectus recession and lateral rectus resection has been the most effective mode of therapy.3 Repeated surgery may be necessary in rare instances.3,11 The cyclic nature is probably the result of many interacting factors. It may be related to a change in cellular metabolism in muscle and/or nervous tissue. One cannot say whether any biological clock mechanism is located in the extraocular muscle and possibly regulated or influenced by the central nervous system or whether there is an irritable focus in the oculomotor nucleus which then transmits cyclic stimuli to extraocular

muscle.12

4CONCLUSION

This case highlights the importance of awareness of this rare ocular motility disorder, with need for repeated examinations, to confirm the diagnosis and treat early with surgical intervention, thereby re-establishing the normal binocular function.

REFERENCES

1.Windsor CE, Berg EF. Circadian heterotropia. Am J Ophthalmol 1969; 67: 565.

2.Costenbader FD, Mousel DK: Cyclic esotropia. Arch Ophthalmol 1964; 71: 180.

3.Helveston EM. Surgical treatment of cyclic esotropia Am Orthopt J 1976; 26: 87–88.

4.Burian HM: Round table discussion in Allen JH (ed) Strabismus Ophthalmic Symposium II. St.Louis Mosby Co.1958, p 488.

5.Helveston EM. Cyclic strabismus. Am Orthoptic J 1973; 23: 48–51.

6.Costenbader FD, O’Neil JF. Cyclic strabismus, in Bellows JG (ed) Contemporary ophthalmology Honoring Sir Stewart Duke Elder, Baltimore, Williams & Wilkins Co. 1972, p 422.

7.Uemura Y, Tomila M, Tanaka Y. Consecutive cyclic esotropia. J Pediatr Ophthalmol Strabismus 1977; 14: 278–280.

8.Muchnick RS, Sanfilippo, S, Dunlap EA. Cyclic esotropia developing after strabismus surgery. Arch Ophthalmol 1976; 94: 459–460.

9.Pillai P, Dhand UK. Cyclic esotropia with central nervous system disease: Report of two cases. J Pediatr Ophthalmol Strabismus 1987; 24(5): 237–241.

10.Pott JWR, Godts D, Kerkhof DB, de Faber, JTHN. Cyclic esotropia and the treatment of over-elevation in adduction and V-pattern. Br. J Ophthalmol 2004; 88: 66–68.

11.Cahill M, Walsh J., McAleer, A. J AAPOS 1999; 3: 379–380.

12.Caputo AR, Greenfield PS. Ann Ophthalmol 1978; 10(6): 775–778.

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Transactions 29th European Strabismological Association Meeting – de Faber (ed) © 2005 European Strabismological Association, ISBN 04 1537 211 9

Interrelationship of binocular and monocular functions in anisometropic amblyopia

I.M. Boychuk

Filatov Institute of Eye Diseases, Odessa, Ukraine

ABSTRACT: Quantity and quality of passing signals to both hemispheres from amblyopic and pair eye causes the return reaction of both hemispheres, but different in degree and so form different types of binocular interrelationship. To prove this fact in clinic – functional indices of both eyes, accompanying the presence or absence of binocular vision and, in particular, central and peripheral stereovision in children with anisometropic amblyopia were observed.

84 children with central (I), 28 with eccentric fixation (II) aged 5–8 y. o. were observed. Visual acuity, functional state of retina and optic nerve of both eyes and difference ( ) between them were studied with routine methods. To study binocular functions Worth test, Lang test II and suggested device for central stereovision were applied. Degree of decline of binocular functions depends on ( ) in refraction (6,0 dptr.), light sensitivity between both eyes (1, 3 log unit) and liability of visual nerve of amblyopic eye.

1INTRODUCTION

Anisometropic amblyopia is developing on to the eye with the higher degree of refraction (hypometropic or myopic), some authors link forming of anisometropia with asymmetry of the brain [2]. About 1/3 of amblyopic children are anisometropic. The greater part of patients with anisometropic amblyopia has no visible deviation, however binocular vision is often absent and rare is recovering. One of the causes of given fact there is aniseikonia and impossibility of fusion of both images. However even in case of correction of aniseikonia, improving of binocular vision succeeds only in the 57% cases [4]. Horizontal disparity of retinal images secures information, necessary for the binocular evaluation of depth and stereopsis [1]. Anatomic substrate, due to which the brain recognizes disparity of retinal images, is partial crossing of visual fibers in area of chiasm, and also interaction of halves of visual analyzer through the corpus callousum. Transformation through the corpus callousum is necessary for stereopsis in the case if the images get on the nasal or temporal halves of retina at the same time [3]. A question about interaction of functional indices of retina with the state of binocular co-operation of both eyes was not studied. However interaction between them is obvious, because quantity and quality of passing signals in both hemispheres from stimulating amblyopic or dominant eye causes the return reaction of both hemispheres, but different in the degree, that produces varies on force and type binocular links.

Therefore given work is conducted with the purpose to determine what kind of functional indices of both eyes accompany a presence or absence of binocular vision in children with anisometropic amblyopia.

2MATERIALS AND METHODS

Studies of visual functions in children (112) aged 5–8 y.o. with anisometropic amblyopia was conducted. Children with amblyopia were devided in dependence of monocular fixation into groups: with

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Table 1. Visual functions in the I group of children with anisometropic amblyopia depending on the presence or absence of stereopsis by device for measurements of stereo vision disturbances.

central fixation there were 84 (I group) and with eccentric 28 (II group) children, among them parafoveal had 20 and macular fixation had 8 children. Refraction of amblyopic eyes was hyperopic. Binocular vision by four dot test was in all children of the I group and in the 23,1% (6) of II group; simultaneous vision was in 30,8% (9) and monocular in 46,1% (13) of children of the II group.

The following monocular functions of both eyes and the difference ( ) between the values of indexes of both eyes were determined in all children: visual acuity, refraction, threshold by maculotest (Haidinger brushes), threshold of electrical sensitivity by phosphen (mA), critical flicker fusion by phosphen (Hz), light sensitivity of cones (log units), light sensitivity of rods (log units), colour thresholds (red, green, blue), mesopic vision, monocular fixation of amblyopic eye.

Binocular functions also were explored: character of binocular vision by Worth Dot test, sinoptophore (junction, fusion), macular stereovision by Test Lang II, fovea (central) stereovision by suggested device.

Statistical evaluations were conducted by the STATISTICA program for Windows 98, for comparative estimation of indexes a criterion of Newman Keuls Test (Breakdown & one way ANOVA) was applied. Analysis of variance of monocular and binocular functions in groups was done in dependence of presence or absence of binocular vision by Worth Dot test and also threshold of fovea (central) and macular (peripheral) stereovision.

3RESULTS AND DISCUSSION

Threshold of stereopsis by the Lang test II was established positive at 100% of children in the I group, and 23,1% in the II group, among them a threshold within the limits of normal was in 16,7% and higher than normal in 83,3%. A threshold of stereopsis on device for estimation of stereovision was positive in 33,3% and equal to 0 in the 66,7% of children of the I group, and in the II group positive threshold in 15,4% and equal to 0 was established in 84,6% of cases accordingly.

In the I group all children had binocular vision on the four dot test and there was a positive result by the Lang test II, therefore an analysis of visual functions depending on presence or absence of the central stereopsis, by elaborated device for measurements of stereo vision disturbances was conducted. Comparative evaluation of averages of indices of the visual functions, having reliable distinctions (by F criterion) in cases with the positive threshold on the device and equal to 0 is presented in the Table 1.

From the data presented in the Table1 it follows, that absence of central stereopsis in cases with the central fixation of amblyopic eyes is accompanied by the lower thresholds by Haidinger brush phenomenon of the sound eye and by the greater difference between the values of light sensitivity of cones (P 0,05).

Data about the visual functions in children of the II group with amblyopia and eccentric fixation, having binocular and simultaneous vision by the four dot test are presented in the Table 2.

From presented data it follows, that in children with the parafoveal and macular fixation in the group of children who had binocular vision, refraction of amblyopic eyes was lower in values,

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Table 2. Average indices of central functions in the II group of children with anisometropic amblyopia having binocular and simultaneous vision by the four dot test.

visual nerve liability was higher (CFfph), distinction in force of refraction of both eyes was less, threshold of stereopsis by the Lang test II was positive (better), and threshold of depth perception (in mm) from 5 m lower (better) in comparison to group, in which simultaneous vision was established (R 0,05).

The obtained data first allowed revealing broken mechanisms of monocular and binocular vision in anisometropic amblyopia and taking it into consideration during treatment.

4CONCLUSIONS

In anisometropic amblyopia with the central fixation of amblyopic eye binocular vision by four dot test was established in 100% of children, peripheral stereo acuity by the Lang test II in 100%, among them in accordance with normal (200 arc. sec) in 16,7% and higher than normal in 83,3%.

In anisometropic amblyopia with the eccentric fixation of amblyopic eye binocular vision by four dot test was established in the 23, 1% of cases, positive threshold of stereoacuity by the Lang test II was in 15, 4%.

In children with anisometropic amblyopia degree of decline of binocular functions depends on difference in refraction (6, 0 dptr.), light sensitivity between both eyes (1, 3 log unit) and liability of visual nerve of amblyopic eye.

REFERENCES

Adler F.H Physiology of the Eye. St. Louis, Mosby C.V. 1959, p. 145–180. Campos E.C. Invest. Ophthalmologic, 1989: vol. 13, N5, p. 327–330.

Hubel D.H. & Wiesel T.N.: Receptive fields, binocular interaction and functional architecture in the cat’s visual cortex, Physiology (Lond) 160: 106, 1962.

Spiritus M., Xuksel D., Vandelammoitle S. Anisometropia and amblyopia in non strabismic children. Transactions 23rd Meeting, ESA, Nancy, Eolus Press, 1996.

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