Year : 1983 | Volume
: 31 | Issue : 7 | Page : 807--812
Amblyopia in myopia
Dr Rajendra Prasad Centre for Ophthalmic Sciences, A.I.I.MS., New Delhi, India
Dr. Rajendra Prasad Centre for Ophthalmic Sciences, A.I.I.M.S., New Delhi
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Prakash P. Amblyopia in myopia.Indian J Ophthalmol 1983;31:807-812
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Prakash P. Amblyopia in myopia. Indian J Ophthalmol [serial online] 1983 [cited 2020 Oct 28 ];31:807-812
Available from: https://www.ijo.in/text.asp?1983/31/7/807/29673
Amblyopia due to anisometropia is a well recognised condition. Anisohypermetropia is for more common causing anisometropic amblyopia than anisomyopia. It is to be noted that amblyopic eyes are oftner (95.6%) hypermetrophic and only 4.4% are myopic (Prakash et al 1976). Unlateral high myopia with amblyopia has not been studied widely. Priestly et al (1963) reported favourable results with pleoptic therapy. Rosenthal and von Noorden (1971), Pollard and Manley (1974) and Mets and Price (1981) have also reported favourable therapeutic results in amblyopic myopia. In this study cases of myopia with amblyopia have been analysed and therapeutic results of conventional occlusion have been evaluated.
MATERIAL AND METHODS
60 cases of unilateral high myopia were taken from ocular motility clinic of Dr. R.P. Centre for Ophthalmic Sciences. Unilateral high myopia with at least spherical equivalent of 5.0 dioptres in the myopic eye and a difference of at least five diopters between the two eyes was required of each patient in the study. patients varied from the ages of 3 years to 26 years. (average age about 10 years). Full myopic correction was given after appropriate cycloplegic refraction and total occlusion of the normal eye was prescribed.
Complete ophthalmic check up including thorough funduscopy was undertaken to rule out any organic pathology.
26 cases out of these 60 cases who underwent amblyopia therapy with follow up have been evaluated with regards to therapeutic results. The duration of treatment lasted from 3 months to15 months with an average of 68 months. The patients who continued improvement were given occlusion for longer periods. The cases who showed no improvement at all in 3 months time were dropped. Strabismus surgery, prisms or contact lenses were prescribed when needed.
Out of 60 patients, 35 were male and 25 were females.
Right eye was seen to be affected in 37 cases (61.6%) and left eye was seen in 23 cases (38.3%). 4 cases (6.6%) were esotropic and 27 cases (45.0%) were exotropic. 29 cases (48.3%) were having no manifest strabismus. Most of the patients seen complained of defective vision and rest of them had obvious manifest squint.
Maximum numbers of cases were seen above the age of 15 years (26 cases 43.3%) where as the rest of the cases were almost equidistributed amongst groups of upto 5, 510 and 10-15 years age group [Table 1]. It is further, noted that myopia more than 10 dioptres was seen in 20 cases (33.3%) and in rest of the 40 cases (66.6%) it was between 5 to 10 dioptres.
[Table 2] shows the refractive error of follow eye. It is seen that 23 eyes (38.3%) were emetropic and 9 eyes (15.0%) had hypermetropia upto 3 dioptres. 28 eyes (46.6%) were myopic mostly within 3 dioptres.
[Table 3] depicts visual acuity in relation to amount of myopia. It is noted that there is some relationship between depth of amblyopia and amount of myopia of effected eyes. Myopia of 5 to 6 D had 32.9% cases with a vision of 6/18 compared to 10'„ cases of myopia of more than 10 dioptres. However with increasing depth of amblyopia, though similar trend is noted but disparity becomes less & less.
[Table 4] shows the visual acuity in relation to associated deviation it is observed that 7075% cases had 6/60 or less vision when associated with eso or exodeviation compared to 27/5% cases with no manifest deviation.
However no specific relationship could be found between the depth of amblyopia and the age of the patients [Table 5].
[Table 6] shows the results of amblyopia therapy in relation to initial vision. It is very obvious to note that vision of 6/18 gives the best results and with progressive increase in depth of amblyopia, the results are progressively poorer.
[Table 7] shows the relationship of degree of myopia in amblyopic eye with the visual improvement.
No co-relationship could be made out.
[Table 8] depicts the relationship of associated deviation with improvement of vision. It is observed that the vision 6/9 or better could be obtained in 60% cases with no associated manifest deviation compared to 40% of exodeviation. Similarly 6/18-6/12 vision could be obtained in 26/6% cases in former compred to 20.0% cases in later group.
Esodeviation is not worth commented upon as there was only I case which did improve to 6/9.
Shows relationship of age with improvement of vision. No corelationship could be established. [Table 10] shows that binocularity was present in 30.8% cases before any therapy, but finally after treatment it was seen in 57.7% cases.
Problem of amblyopia in myopia is not widely evaluated. Usually occurrence of amblyopia in myopia is not common because these patient even when not corrected have the opportunity of having adequate stimulus for development of vision from near objects unless myopia is of high order resulting in blurred visioneven for near objects giving rise to ametropic amblyopia. Secondly the element of anisometropia when the affected eye is more myopic than the other or when the other eye is emmetropic or uncommonly even hypermetropic. Amblyopia in myopia has been noted to be in 5% cases of amblyopia put of which 1/3% show bilateral amblyopia. (Prakash et. al 1976). In this series maximum amount of myopia noted was 13.5 dioptres, which had no organic pathology. It is common to have high myopes with loss of vision with organic changes although these case may also be having some element of amblyopia. Such cases were not included in this study to evaluate therapetic results in myopic amblyopia. There is a direct relationship between the degree of myopia and depth of amblyopia and our observations supports those of Rosenthal and Von Noorden (1971). There is another factor which aggravates amblyopia in such cases i.e. manifest ocular deviation. Most of the cases had exodeviation with definite increase in depth of amblyopia.
[Table 4] This observation is contrary to those of Rosenthal & Von Noorden (1971) who found no such corelationship. It was most rewarding to get good results in cases who had initial vision of 6/18 where all the cases could get a vision of 6/9 or better compared to 50% cases who attained similar vision with an initial vision of 6/36. This observation is in agreement with that of Pollard and Manley (1974).
No corelationship between degree of myopia with therapeutic results could be made. It is also noted that presence of associated manifest strabismus in these cases was not favourable to get good results which indicates that strabismus not only accentuates the depth of amblyopia but also affects the final therapeutic results. This observation is also contrary to the observation of Rosenthal and Von Noorden (1971)
The age factor which is so important in the therapeutic result does not bear much importance in this study. Even two cases of the age group of 23 and 20 years could get a vision of 6/6 from 6/18. Another patient aged 22 years could improve from 6/60 to 6/18. The fourth case aged 22 years could improve from 6/60-6/24. These examples illustrate that visual prognosis in these cases is quite good and it is contrary to the observations of Rosenthal and von Noorden (1971) who have reported poor results in age above 6 years but in the agreement with Pollard and the Manley (1974) who have also noted good- results even after 6 years.
It has already been noted that anisomyopia or unilateral myopia also demonstrates heavy eye phenomenon (Bagshaw-1967, Hart-1967 Prakash-1976). Those cases which have binocular vision after amblyopia therapy do not necessarily need contact lenses as anisomyopia of axial origin can easily maintain good binocular vision even with ordinary spectacles. As a matter of fact ordinary spectacles often prove beneficial in neutralising associated vertical deviations of heavy eye phenomenon. In other cases prismatic correction or vertical squint maybe required.
As a whole, it may be concluded that the results of conventional occlusion in amblyopia of myopic origin are quite encouraging and even chances of improving binocularity are fair.
|1||Rosenthal A.R. and Von Noorden G.K., 1971, Amer. J. Ophthalmol 71: 873.|
|2||Pollard, Z.F. and Manley. D., 1974, Amer Ophthalmol 78: 397.|
|3||Prakash, P, Singha J.N. Khosla P.K., 1976, East Arch. Ophthalmod, 4: 218.|
|4||Prakash, P., 1976, Proceedings 6th Afro Asian Congress Ophthalmology, Madras, p. 468.|
|5||Bagshaw, J., 1967, First International Congress of Orthoptics p. 277 Honry Kimpton London.|
|6||Hart, C.T., 1967, First International Cong. of Orthoptics p. 72. Henry Kimpton London.|
|7||Mets. M. and Price R.L.,1981, AmerJ. Ophthamol, 91: 481.|