|Year : 1969 | Volume
| Issue : 6 | Page : 245-249
The incidence of eccentric fixation
S.R.K Malik, DK Sen, VK Grover, S Choudhry
Department of Ophthalmology, Maulana Azad Medical College, New Delhi, India
|Date of Web Publication||11-Jan-2008|
Department of Ophthalmology, Maulana Azad Medical College, New Delhi
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Malik S, Sen D K, Grover V K, Choudhry S. The incidence of eccentric fixation. Indian J Ophthalmol 1969;17:245-9
Eccentric fixation may be defined as a monocular phenomenon in which the eye utilises a portion of the retina other than the fovea for fixation.
Eccentric fixation was once considered to be a rare complication of longstanding strabismus. Improvement of our diagnostic armamentorium permitting direct observation of the area of fundus taking up fixation has revealed that amblyopic eye often fixates with an extrafoveal area. This has attained lot of importance in recent times, because it is realised that management procedure adopted in such cases should be based on the pattern of fixation.
Reviewing the literature we found gross disparity in the incidence of eccentric fixation reported from time to time. The purpose of this paper is to bring into light the possible reasons for this difference in the results reported by different workers and to suggest a standardised procedure for the diagnosis and assessment of the cases of eccentric fixation. The incidence of eccentric fixation found at Irwin Hospital as calculated by the suggested procedure is being presented.
| Methods and Materials|| |
1600 cases of squint and amblyopia were examined at our clinic. A detailed history regarding the onset of squint and amblyopia, any precipitating cause-systemic or ocular was taken. Ophthalmic examination was carried out in every case to exclude any pathology which could explain the presence of amblyopia. Pupils were dilated and eccentric fixation determined by using Linkz star attached to the projectoscope. The patient was instructed to look into the centre of the star and the relation of normal fovea with the star was noted and type of eccentric fixation determined according to the classification suggested by Malik, Gupta and Choudhry (1968) [Figure - 1].
i. Normal or foveal fixation: The star is focussed on the fovea.
ii. Unsteady foveal: As the name implies, the fixation is foveal but there are very fine movements of the fovea in the central clear area of the Linkz star. It may be under the star but never goes outside it.
iii. Erratic: Unsteady parafoveal fixation in which the fovea comes to the centre of the star momentarily and goes out again but remains within 3 degrees.
iv. Parafoveal: Star focussed on retina at a point outside fovea but within 3 degrees from it,
v. Paramacular : Star focussed on a retinal point 3-6 degrees from fovea.
vi. Centrocaecal: Star focussed on a retinal point between disc and 6 degrees away from fovea.
vii. Paracoecal: Star focussed on a retinal point around or over the disc.
viii. Divergent: Star focussed by a retinal point more than 6 degrees away on temporal side of fovea.
ix. Non-Fixation : When no definite point is used for fixation. The star is seen to move all over the retina.
Care was taken to exclude cases of eccentric viewing by stressing upon the patient whether he is subjectively getting the feeling of looking at the star or not. Cases having amlyopia not explainable by existing ocular pathology were also included in the series.
| Observations|| |
Out of 1600 cases of squint and amblyopia examined 468 cases (29.25%) had eccentric fixation. Out of these cases of eccentric fixation 332 cases (70.9%) had unilateral eccentric fixation while the rest had bilateral eccentric fixation. In the unilateral group, parafoveal fixation (1-3 degrees) and in the bilateral group erratic fixation (within 3 degrees) in both the eyes were of commonest occurrence. In cases of bilateral eccentric fixation the better eye either had erratic or parafoveal fixation in majority of the cases [Table - 1],[Table - 2].
| Discussion|| |
In our series of 1600 cases of squint and amblyopia, 468 cases (29.25%) were found to have eccentric fixation. This is in close agreement with the findings of Cuppers (1958) and Pasino (1962), but is considerably different as compared with that of Brock and Givner (1952), Von-Noorden (1960) and Fitton (1962). Sternberg and Bohar (1961) have given a strikingly low incidence of 5%. Worth as far back as 1903 found the incidence of eccentric fixation as 30% by observing the position of the corneal reflex. Using this crude method of diagnosis, small degrees of eccentric fixation must have been missed by him. This high incidence reported by him could be due to persistent neglect and ignorance regarding the treatment of squint at that time [Table - 3]. From the table it is apparent that there is a marked disparity in the incidence of eccentric fixation reported by different workers. The disparity in results could be due to various factors.
(i) Selection of different types of patients by different workers. Some have found the incidence of eccentric fixation in cases of squint (Scully-1961 22.8%; Scully and Naylor-1961 -22.3%: Sternberg and Bohar-1961-5%) while others have also included cases of amblyopia without squint (Agarwal, Khosla and Angra-1964, 23.7%). Agarwal et al (1964) and Malik et al (1967 & 1968) have included the cases having pathology of ocular media in their calculations while other workers have made no such consideration.
(ii) Different methodologies with different standardisations have been followed by different workers. Worth (1903) used the position of monocular corneal reflex as a guide to measure the degree of eccentric fixation. Brock and Givner (1952) used after image transference test for the diagnosis of eccentric fixation. Other workers have used projectoscope visuscope or fixation star incorporated in an ophthalmoscope to measure eccentric fixation. The readings of visuscope and projectoscope fitted with Linkz star do, not correspond with each other (Malik et al-1968).
Hence the incidence- of eccentric fixation differs markedly as found by different workers due to the difference in the selection of cases and methodology in diagnosis. As such these values lose their comparative value. Unless an international code or an understanding at an international level between the various pleoptic workers is made regarding the criteria of labelling a person as having eccentric fixation, these values cannot be compared on authentic and scientific grounds. It is, therefore, suggested that a uniform standard should be laid in selection and method used in diagnosis of these cases.
| Summary|| |
1) 1600 cases of squint and amblyopia were investigated for the presence of eccentric fixation. 468 cases (29.25% had eccentric fixation. 332 cases (70.9%) had unilateral eccentric fixation while the rest (29.1%) had bilateral eccentric fixation.
2) The possible reasons for marked disparity in the incidence of eccentric fixation as reported in literature has been reviewed. A standard procedure for analysis of these cases have been suggested and used to find the incidence of eccentric fixation in cases of squint and amblyopia.
| References|| |
Agarwal, L. P.; Khosla, P. K.; Angra. S. K.: Indian J. Orthoptics & Pleoptics, 1:12, 1964.
Brock, F. W. and Givner, I._ A.M.A. Arch. Ophth., 47:775, 1952.
Cuppers, C.: Orthoptic and Pleoptic problems in Germany. Lectures to North of England Opthalmological Society. June, 12 & 13, 1958.
Fitton, M. H.: Brit. Orthopt. J. 19:35. 1962.
Malik, S. R. K.; Sood, G. C.; Ganguli, G.: Choudhry, S. Tn. All India Ophthalmological Society-1967.
Malik, S. R. K.; Sood, G. C.; Choudhry, S.: Tr. All India Ophthalmological Society--1968.
Malik, S. R. K.; Gupta, S. K.; Choudhry, S.: Brit. J. Ophthal.-1968 (in press).
Pasino, L.: Ophthalmological, 143:431, 1962.
Scully, J. and Naylor, E. J.: Brit. Med. J. 2:81, 1961.
Scully, J. P.: Brit. Med. J. 2:1610, 1961.
STERNBERG, A. R. and BOHAR, H.: Ophthalmologica, 141: 229, 1961.
Von Noorden, G. K.: Am. Orthopt. J. 10:7. 1960.
Worth, C.; Squint, its causes, Pathology and Treatment. Bathers, Tindal and Cox. London (1903).
[Figure - 1]
[Table - 1], [Table - 2], [Table - 3]