|Year : 1972 | Volume
| Issue : 1 | Page : 4-10
Pathogenesis and management of bilateral eccentric fixation
S.R.K Malik, DK Sen, S Choudhry
Department of Ophtalmology, Maulana Azad Medical College, New Delhi, India
Department of Ophtalmology, Maulana Azad Medical College, New Delhi
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Malik S, Sen D K, Choudhry S. Pathogenesis and management of bilateral eccentric fixation. Indian J Ophthalmol 1972;20:4-10
Amblyopia with eccentric fixation was previously acknowledged to be a unilateral phenomenon, but recently it has been shown to exist bilaterely in several isolated case reports (Dalgleish and Naylor  Von Noorden  ). and Mackonsen  In most of these cases macula was found to be damaged on both the sides. However, Von Noorden  described two cases of bilateral eccentric fixation in strabismic amblyopia where no organic macular damage existed in either eye. Hermann and Priestley  evaluated and presented 20 such cases. Malik, Ganguli, Sood, and Singh' reported 71 cases of bilateral eccentric fixation and discussed the management of the condition.
The present study has been undertaken to evaluate further the result of the treatment and to discuss the possible etiopathological factors responsible for bilateral eccentric fixation.
| Method and Materials|| |
Cases of squint and amblyopia attending orthoptic and pleoptic clinic of Maulana Azad Medical College and Associated Hospitals, New Delhi are included for this study. Complete orthoptic and pleoptic work-up was done in all cases. Fixation was determined under full mydriasis with projectoscope by using Linksz star graticule which was preferred to the visuscope as even fine movements in the foveal area can be appreciated due to the clear area in the Linksz star. The cases were classified according to Malik Sood, and Choudhry's  classification. The fixation pattern of both amblyopic and non-amblyopic eyes was subjected to much closer scrutiny and doubtful cases were rejected from the study. Responses to after images and Haidinger Brushes were nated in all cases. Fundus was carefully studied to exclude all those cases having detectable macular pathology. The better eye was given glasses while the worse eye was given Doyne's occulder for 2 weeks before starting the pleoptic exercises. When the squint was more than 15° it was corrected by surgery first. When the fixation was close to the fovea (erratic or parafoveal) the patient was put straight on Haidenger Brushes. When the fixation was away from the fovea the patient was given after image exercises with the propectoscope and when the fixation shifted to within 3° of fovea patients were asked to attend the exercises in the Haidenger's Brushes. The pleoptic exercises were given to the worse eye once daily. Follow up was done once a week.
| Observations|| |
Twelve hundred cases of squint and amblyopia have been investigated in this clinic over a period of three and a half years. Out of -these 360 cases (comprising 30%) had eccentric fixation, 242 unilateral and 118 bilateral. Of the bilateral cases 28 continued to have the pleoptic therapy for a sufficient length of time for the evaluation of the results. Rest of the cases either did not report for the treatment or discontinued the treatment before any conclusion regarding the efficacy of the therapy could be reached. [Table - 1] shows the age and sex distribution of the cases.The age of the patients ranged from 5-45 years but maximum cases were in the first two decades. Female attendance was more as compared to males (65:53).
Analysis of type of fixation has been given in [Table - 2]. Fixation was erratic (ERR) in both the eyes in 46 cases. In rest of the cases the eccentricity of fixation was of smaller degree in one eye.
Out of a total member of 118 cases of squint, 67 were of the convergent type and 25 of divergent type.
[Table - 3] shows the relationship with type of refractive error. It is evident that in most of the cases the eye was hypermetropic (92 out of 118). Only in 4 cases the eye was emmetropic. Anisometropia was seen in 86 cases. Out of 28 cases who continued to take pleoptic exercises for sufficient length of time improvement in fixation and/or vision was noted in 19 cases (67.8%)
[Figure - 1],[Figure - 2] display graphically the changes in fixation and visual acuity with pleoptic therapy. It is evident that lesser degrees of eccentric fixation showed better response to treatment as compared to those where the eccentric point lay further away. It also reveals that cases having lesser degrees of amblyopia responded better to pleoptic treatment as compared to those having denser amblyopia. It is interesting to note that in most of the cases showing improvement the better eye also showed some concomitant improvement.
| Discussion and Comment|| |
In our study we continue to find a high incidence of this condition (9.8%) in cases of squint and amblyopia. This agrees well with the observation of Hermann Priestley  who commented that in a large series of emblyopes about 10% would show manifest bilateral eccentric fixation and amblyopia which was apparently neither organic nor hysterical. We, therefore, advocate a careful scrutiny of the fixation pattern in both the eyes particularly in the better eye before passing this off as normal. The fact that bilateral eccentric fixation has been found to be more common in convergent squint (56.7% of cases) is related to the greater frequency of occurrence of convergent squint, since approximately 75% of all squint patients have esotropia.
The development of monocular eccentric fixation is not well understood but is believed to be due to altered sensorial relationship (Copper  ), clinically undetectable organic lesion in the macula (Smukler  and Sachsenweger ) or high visual centres (Sachsen wager  ). The etiopathogenesis of bilateral eccentric fixation is all the more obscure. It may be that there is no one single factor responsible for all the cases. Some cases may be as a result of bilateral poor visual acuity due to damage to central part of visual apparatus and substitution of the directional value of the anatomical foveas of both eyes by eccentric points as suggested by Von Noorden  or may be due to damage at a higher level in the visual pathways of orientation and integrating centres as suggested by Akimoto  . In none of our cases we could get the history of maternal illness in the antenatal period, nor could we get any history of difficult labour to account for the damage. Though subclinical maternal illness cannot be ruled out, it is not so common as to alone explain such a high incidence of this condition. Hermann and Pristley  postulated inherent bifoveal instability as an entity to explain bilateral amblyopia with eccentric fixation. He observed that in most of the cases of unilateral amblyopia the so called sound eye of the amblyope did not fix in the same way as does the sound of a normal person. They also noted that 20/20 or better vision was rarely reached in the "normal eye" of an unilateral amblyope. Our experience in this field, however, has been different. We had not found any abnormality in the pattern of fixation in the sound eye of an unilateral amblyope. Moreover, the visual acuity was 20/20 or better in the "normal eye" of all the unilateral amblyopic cases.
We, therefore, postulated that most cases of bilateral eccentric fixation result from small haemorrhages in the macular area which get resolved leaving behind no detectable evidence. Reinal heamorrhages are reported in 10 to 35% of all children at brith (Duke elder  ). Such a heamorrhage in the macular area is bound to depress the central vision. During this period some other point on the retina might become a point par excellence and develop eccentric fixation. It is possible that the so developed eccentric point in infancy continues to supress the foveal vision even though the fovea has recovered structurally. When the fovea is stimulated and the eccentric point is depressed it results in elimination of supression of the fovea thereby helping the fixation to become once again centric with recovery of function. We therefore, thought to treating such cases with pleoptic treatment and the effort was quite rewarding. We found noticeable improvement in 19 cases (67.8%). The concomitant improvement in the better eye in most of the cases showing improvement in the worse eye is perhaps because occlusion of the worse eye acted as a conventional occlusion for the better eye which incidentally had only minor degrees of eccentricity Hermann et al  subjected 12 cases to pleoptic therapy and in 67% cases fixation became centric though significant visual improvement was noted in only 33% of the cases.
Such encouraging results with pleoptic therapy support our hypothesis that the original organic lesion recovers structurally but leaves behind only functional defect in quite a good number of cases. This functional loss is recoverable by pleoptic treatment. The cases which did not show any improvement are the ones where structural damage has been permanent, though not detectable with the opthalmoscope.
We propose to study the fundi of infants soon after birth to select cases of macular haemorrhages and follow them up for a sufficiently long time to see in what per centage of cases eccentric fixation develops to establish further the authencity of our hypothesis.
| Summary|| |
One hundred and eighteen cases of bilateral eccentric fixation in the absence of any detectable macular pathology are presented. The incidence has been found to be 9.8% in a series of twelve hundred cases of squint and amblyopia. 28 cases completed the course of pleoptic treatment and of them 19 cases (67.8%) showed improvement in visual acuity or fixation or both.
Encouraging results with pleoptic treatment lends support to our hypothesis that most of the cases of bilateral eccentric fixation result from small haemorrhages in the macular area in infancy.
| References|| |
Akimoto, S : Clin. of Ophth. Shipkawabagh. 18/6, 704 1964.
Coppers, C.: Klin. Mbl., Augenheilk, 18/6, 709. 1956.
Dalgleish, R. and Naylor, E.J.: Bilateral Eccentric fixation with no ocular deviation in a case of Heredo macular degeneration. Brit. J. Ophth.. 47, 11 (1963).
Duke Eider.: W. S. Text book. Opthalmology. Vol. IV P. 3839, London. Henry Kimpton. 1949.
Hermann, S.J. and Priestley B. S.: Bifoveal instability : The relationship to strabismic amblyopia. Amer. J. Ophth. 60, 452, 1965.
Malik, S.R.K. Sood, G.C. Ganguli, and Singh. G.: Bilateral eccentric fixation, Brit. J. Ophth. 52:153, 1968.
Malik, S.R.K.; Sood, G. C.; Gupta. A.K.; Choudhry, S.: Management of amblyopia with eccentric fixation, Orient. Arch. Ophth. 6, 149, 1968.
Noorden. G.K. Von : Bilateral eccentric fixation, A.M.A. Arch. Ophth. 69: 25. 1963.
Noorden, G. K. Von and Mack onsen, G.: Phenomenology of eccentric fixation. Amer. J. Ophth. 53, 642, 1962.
Sachsenweger R.: Klin. Mbl. Agen. Augen. 147/4, 1965.
Smukler, Amer.: Jour. Ophth. 16, 621, 1933.
[Figure - 1], [Figure - 2]
[Table - 1], [Table - 2], [Table - 3]