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Year : 1973  |  Volume : 21  |  Issue : 3  |  Page : 98-101

Bilateral eccentric fixation in straight amblyopia


Department of Ophthalmology, Postgraduate Institute of Medical Education and Research, Chandigarh, India

Correspondence Address:
S D Gupta
Department of Ophthalmology, Postgraduate Institute of Medical Education and Research, Chandigarh
India
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Source of Support: None, Conflict of Interest: None


PMID: 4500010

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How to cite this article:
Gupta S D, Sood S C, Jain I S. Bilateral eccentric fixation in straight amblyopia. Indian J Ophthalmol 1973;21:98-101

How to cite this URL:
Gupta S D, Sood S C, Jain I S. Bilateral eccentric fixation in straight amblyopia. Indian J Ophthalmol [serial online] 1973 [cited 2021 May 8];21:98-101. Available from: https://www.ijo.in/text.asp?1973/21/3/98/31389

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Eccentric fixation means that some retinal area other than the fovea itself takes up the fixation under monocular conditions.

Bilateral eccentric fixation was first reported by NOORDEN[9] in two cases of squint. DALGLERSH et al [4] had noticed bilateral eccentric fixation in one straight amblyope who had heredomacular degeneration in both the eyes. HERMANN et al [6] reported 20 cases of bilateral eccentric fixation but only one of these did not have any squint, and he had Stargardt's disease. MALIK et al [7] noticed 6 cases of straight eyes out of 71 subjects having bilateral eccentric fixation but five of these 6 had organic lesions at the maculae. In 1972,[8] the same author reported the incidence of bilateral eccentric fixation as 9.8% of all the patients with strabismus and amblyopia.

Seven cases of bilateral eccentric fixation in straight amblyopes are being reported owing to the paucity of literature on the subject.


  Material and Method Top


All the cases of straight amblyopia visiting the squint clinic attached to our department were examined in detail, to rule out any tropia shift on cover test and for ocular motility, binocular vision, fixation and retinal correspondence.

Refraction was done in every case and the best visual acuity with glasses was recorded. Fundus was examined to rule out any pathology in the media or fundii. Fixation was tested with the help of visuoscope. The obser­vations were confirmed by the senior author in every case.

Out of 110 cases of straight amblyopia examined during the last two years, only 7 cases with bilateral eccentric fixation were seen which formed the material for this study.


  Observations Top


Seven cases of straight amblyopia with bilateral eccentric fixation were seen. Four were males and three females. The age of the patients varied from 14 to 28 years. Vision in the eyes ranged from 6/9 to 6/60. Compound hypermetropic astigmatism was the commonest refractive error (78.6%) and only three cases revealed an anisometropia of over 1.5 D. All the 14 eyes had spherical refractive error of more than 3.00 D and 10 of these had, in addition, a cylinder of over 1.00 D.

All the 14 eyes in the 7 cases showed eccentric fixation and all the eyes (except in case No. 1) had fixa­tion nasal to fovea. In case I, the fixation was temporal to fovea in both the eyes. Case No. III had fixation parafoveal nasal and down in both eyes. In five cases (1 to 5), the fixation was identical in the two eyes.

No relationship between the fixation and vision could be established as the number of cases was too small for any evaluation.

Binocular Vision:

All the cases of bilateral eccentric fixation were found to have some binocular vision. Two cases had only grade I while the rest of the five cases had grade I and II. None of the cases had all the three grades of binocular vision.

Retinal Correspondence:

Retinal correspondence was studied by Bagolini's glasses, after-image test and bifoveal correspondence test. Bifoveal correspondence test could not be done in three cases (4, 5 and 6) because of the erratic fixation. Out of the 7 cases, one case was un­cooperative and the test for corres­pondence could not be relied upon. The rest of the six cases showed harmonious abnormal retinal corres­pondence and the eccentric points in the two eyes of each patient corresponded.


  Discussion Top


Incidence of bilateral eccentric fixation as reported is 9.87% in cases of squint and amblyopia[10] but, very few cases of bilateral eccentric fixation in straight amblyopia have been reported. Most of the cases reported so far showed macular pathology in both eyes (4, 8, 9). We found bilateral eccentric fixation in 7 of the 110 straight amblyopes giving an incidence of 6.36%.

There is no general agreement as to the cause of bilateral eccentric fixation. NOORDEN[9] mentioned that bilateral poor visual acquity due to damage to central part of the visual apparatus and substitution of the directional value of anatomical foveas of both eyes by eccentric points was responsible for bilateral eccentric fixation. AKIMOTO[1] (1964) is of the view that bilateral eccentric fixation is due to damage at a higher level - in the visual pathways of orientation and integration centres. HERMANN et al[6] blamed the bifoveal instability, which he considered to be an inherited defect, as a cause of bilateral eccentric fixation.

Anisometropia, which is perhaps the most important single factor in the causation of unilateral eccentric fixa­tion in straight amblyopia, is very unlikely to be the cause in bilateral eccentric fixation. MALIK et al [8] blamed minute macular haemorrhages in both eyes at the time of birth as a cause of bilateral eccentric fixation. Unless a prolonged follow-up of the children with macular haemorrhages is carried out, it is not possible to prove or disprove this hypothesis.

Since all our 14 eyes had refractive error more than 3.00 D and 10 of these had, in addition, astigmatism over 1.00 D, bilateral refractive blurring could be the cause of amblyopia and eccentric fixation in these cases. Peripheral part of the retina with a better resolving power than the supressed fovea is forced to take up the fixation resulting in eccentric fixation.

Since none of our cases had squint or any history of previous deviation of the eyes, it is very unlikely that abnormal retinal correspondence developed in response to motor anomaly. Moreover, motor anomaly could only cause eccentric fixation in one eye and also fovea in one eye would correspond to eccentric fixation point in the other. But, the correspon­dence of eccentric fixation points in both eyes of all patients cannot be explained. We, therefore, strongly feel that abnormal retinal correspon­dence in these cases follow the development of eccentric fixation because of dense central scotoma. This supports the view of BANGERTER [2] and we do not agree with CUPPER[3] that eccentric fixation develops on the basis of abnormal retinal correspondence.

The presence of binocular single vision in all the seven straight amblyopes is in agreement with RIVERS [11] who said that good binocular vision is present in straight amblyopes. Eccentric fixation in both eyes has no ill effect on the development of, binocular single vision. Good bino­cular single vision is perhaps due to the development of abnormal retinal correspondence which is an attempt towards the maintenance of binocular single vision.


  Summary Top


Seven cases of bilateral eccentric fixation and abnormal retinal corres­pondence in straight amblyopia have been described. Possible mechanism of the development of bilateral eccentric fixation and abnormal retinal correspondence has been discussed.

 
  References Top

1.
Akimoto, S. (1964): Quoted by Malik et al (1968).  Back to cited text no. 1
    
2.
Bangerter (1955): Quoted by Gunter, K. von Noorden (1966).  Back to cited text no. 2
    
3.
Cuppers, C. (1961): Quoted by Gunter, K. von. Noorden (1966).  Back to cited text no. 3
    
4.
Dalgleish, R. and Naylor, E. J.: "Bilateral eccentric fixation with no ocular deviation in a case of heredomacular degeneration". Brit. J. Ophth. 47: 55. 1963.  Back to cited text no. 4
    
5.
Gupta et al.: "Anisometropia. Its role in sensory anomalies in straight amblyopia". (Paper under preparation).  Back to cited text no. 5
    
6.
Hermann S. J. and Priestley, B. S.: "Bifoveal instability". Amer. J. Ophth. 60: 452, 1965.  Back to cited text no. 6
    
7.
Malik, S. R. K.; Sood, G. C.; Gunguli, G. and Singh, G.: "Bilateral eccentric fixation". Brit. J. Ophth. 52: 153, 1968.  Back to cited text no. 7
    
8.
Malik, S. R. K.; Sen, D. K. and Chowdhary, S.: "Pathogenesis and management of bilateral eccentric fixation". Indian J. Ophth. 20: 4, 1972.  Back to cited text no. 8
    
9.
von Noorden, G. K.: "Bilateral eccentric fixation". Arch. Ophth. (Chicago) 69: 125, 1963.  Back to cited text no. 9
    
10.
von Noorden, G. K.: "Pathogenesis of eccentric fixation". Amer. J. Ophth. 61: 399, 1966.  Back to cited text no. 10
    
11.
Rivers, E.: In correspondence to the editor. Brit. Orth. J. 21: 113, 1964.  Back to cited text no. 11
    



 
 
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