J.ophthalmol.(Ukraine).2021;3:23-27.
http://doi.org/10.31288/oftalmolzh202132327
Received: 09 February 2021; Published on-line: 29 June 2021
Stereopsis before and after surgical treatment for constant versus intermittent exotropia
I. M. Boichuk, Alui Tarak
SI "The Filatov Institute of Eye Diseases and Tissue Therapy of the NAMS of Ukraine"; Odesa (Ukraine)
E-mail: iryna.ods@gmail.com
TO CITE THIS ARTICLE:Boichuk IM, Alui Tarak. Stereopsis before and after surgical treatment for constant versus intermittent exotropia. J.ophthalmol.(Ukraine).2021;3:23-27. http://doi.org/10.31288/oftalmolzh202132327
Background: Exophoria may be caused by congenital or acquired anomalies in orbital structure, ocular structure, extraocular muscle attachment and/or extraocular muscle location. Some researchers believe that the presence of stereopsis after treatment for strabismus indicates that a stable treatment outcome has been achieved and binocular vision regained. The state of stereopsis is believed to be an efficacy endpoint in the evaluation of strabismus surgery.
Purpose: To assess stereopsis before and after surgery for constant versus intermittent exotropia.
Material and Methods: Fifty-nine patients with constant or intermittent exotropia, aged 10 to 21 years, were included in the study. Of these, 33 (group 1) had constant exotropia and 26 (group 2), intermittent exotropia. They underwent surgery on one or both eyes. Visual acuity assessment, refractometry, and biomicroscopy were performed, near and distance angles of deviation were measured by Hirschberg's test and prism cover test, the color test was used to determine the type of binocular vision, and synoptophore, to examine fusion both before and after treatment. Stereoacuity thresholds were assessed with Lang-Stereotest II and Titmus Stereo Fly (circles and animals) tests at daylight at a viewing distance of 30 cm and a Huvitz CCP3100 Chart Projector was used to assess whether stereopsis was present at a 5-m distance.
Results: After treatment, the magnitude of exotropia decreased in all patients, and the mean angle of deviation at near was 3.5±1.4 degrees, and at distance, 3.9±1.9 degrees. In addition, 70% of patients regained binocular vision. At baseline, neither patient in group 1 and only three patients in group 2 exhibited distance stereopsis. After treatment for strabismus, 11 patients in group 1 exhibited near stereopsis, and stereoacuity threshold as assessed by the Titmus Stereo Fly (circles and animals) test was 200-400 arc sec in 24.4% of patients of this group. In addition, in 80.8% of patients of group 2, the stereoacuity threshold was 1500 arc sec, and the stereoacuity normalized and was 200 arc sec as assessed by the circles subtest. That is, after surgery, stereoacuity thresholds decreased substantially, especially in group 2.
Conclusion: After surgery, in 70-80% of cases, stereoacuity increased (stereoacuity thresholds decreased), indicating that the surgical treatment was effective and binocular functions were regained. Our preliminary results suppose that a preoperative near stereoacuity of 200 arc sec will be a favorable factor for improvement in binocular functions and stable orthotropia after surgery for intermittent exotropia.
Ключові слова: розбіжна косоокість постійна, періодична, стан стереозору для далекої і близької відстані, хірургічне лікування
Conflict of Interest Statement: The authors declare no conflict of interest which could influence their opinions on the subject or the materials presented in the manuscript.
References
1.Von Noorden GK, Campos E. Binocular Vision and Ocular motility. Theory and Management of Strabismus. Mosby: St. Louis; 2002. p. 5-18.
2.Awaya S, Nozaki H, Itoh T, Hanada K. Studies of suppression in alternating constant exotropia and intermittent exotropia with reference to fusional background. In: Moore S, Mein J, Stockbridge L, eds. Orthoptics: Past, Present, Future. Miami, FIa: Symposia Specialists, 1976:531.
3.Awaya S, Sugawara M, Komiyama K, Ikeyama K. Studies on stereoacuity in four constant exotropes with good stereoacuity, with a special reference to the Titmus stereo test and EOG analysis. Nippon Ganka Gakkai Zasshi. 1979 May 10;83(5):425-30. Japanese.
4.Chavasse F. Worth's squint or the binocular reflexes and the treatment of strabismus. 7th ed. London: Bailliere Tindall and Cox; 1939.
5.Jung EH, Kim SJ, Yu YS. Factors associated with surgical success in adult patients with exotropia. J AAPOS. 2016 Dec;20(6):511-514.
6.Kim MK, Kim US, Cho MJ, Baek SH. Hyperopic refractive errors as a prognostic factor in intermittent exotropia surgery. Eye (Lond). 2015 Dec;29(12):1555-60.
7.Lang JI. Ein neuer Stereotest. Klin Mbl Augenheilk. 1983;182:373–5.
8.Kashchenko TP, Pospelov VI, Shapovalov SL. [Problems of oculomotor and binocular pathology] In: [Proceedings of the 8th Congress of Ophthalmologists of Russia]. Moscow, 1-4 Jun 2015. Moscow: MNTK “Eye Microsurgery” Publishing Center; 2005. p.740-1. Russian.
9.Bach-y-Rita P. Neurophysiology of eye movements: Control of Eye Movements. New York: Academic Press; 1971.
10.Ball A, Drummond GT, Pearce WG. Unexpected stereoacuity following surgical correction of long-standing horizontal strabismus. Can J Ophthalmol. 1993 Aug;28(5):217-20.
11.Beneish R, Flanders M. The role of stereopsis and early postoperative alignment in long-term results of intermittent exotropia. Can J Ophthalmol. 1994 Jun;29(3):119-24.
12.Avetisov ES. [Concomitant strabismus]. Moscow: Meditsina; 1977. Russian.
13.Avetisov ES, Tarastsova MM, Khukhrina LP. [Methods and results of studies on binocular vision in preschool children]. Oftalmol Zh. 1977;32(2):86-9. Russian.
14.Carpenter RHS. Movements of the eyes. London: Pion Limited (2nd ed), 1988.
15.Birch EE, Gwiazda J, Held R. The development of vergence does not account for the onset of stereopsis. Perception. 1983;12(3):331-6.
16.Bishop PO, Pettigrew JD. Neural mechanisms of binocular vision. Vision Res. 1986;26(9):1587-600.
17.Berard P. Prisms: their therapeutic use in strabismus. In: Knapp P, ed. International Strabismus Symposium: an evaluation of present status of orthoptics, pleoptics, and related diagnosis and treatment regimes. New York: Karger; 1968. p.339-44.Crossref
18.Goodwin RT, Romano PE. Stereoacuity degradation by experimental and real monocular and binocular amblyopia. Invest Ophthalmol Vis Sci. 1985 Jul;26(7):917-23.
19.Kim HJ, Choi DG. Clinical analysis of childhood intermittent exotropia with surgical success at postoperative 2 years. Acta Ophthalmol. 2016 Mar;94(2):e85-9.
20.Lang J. Strabismus. Thorofare, N J: Slack:1984.
21.Nishikawa N, Ishiko S, Yamaga I, Sato M, Yoshida A . Distance stereotesting using vision test charts for intermittent exotropia. Clin Ophthalmol. 2015 Aug 25;9:1557-62.
22.Na KH, Kim SH. Comparison of clinical features and long-term surgical outcomes in infantile constant and intermittent exotropia. J Pediatr Ophthalmol Strabismus. Mar-Apr 2016;53(2):99-104.
23.Yang M, Chen J, Shen T, Kang Y, Deng D, Lin X, et al. Single stage surgical outcomes for large angle intermittent exotropia. PloS one. 2016;11(2):e0150508.
24.Yang M, Chen J, Shen T, Kang Y, Deng D, Lin X, et al. Clinical characteristics and surgical outcomes in patients with intermittent exotropia: a large sample study in South China. Medicine (Baltimore). 2016 Feb;95(5):e2590.