|Year : 1961 | Volume
| Issue : 2 | Page : 33-35
Mahatma Gandhi Memorial Medical College, Indore, India
|Date of Web Publication||31-Mar-2008|
B K Dhir
Mahatma Gandhi Memorial Medical College, Indore
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Dhir B K. Convergence insufficiency. Indian J Ophthalmol 1961;9:33-5
This paper is based upon the findings of 158 cases of convergence insufficiency- dealt with in 5 years from 1955.
The advent of binocular vision in human beings has been an event of fundamental importance in the phylogenetical order for the purpose of imparting clear vision. The presence of binocular vision presupposes the harmonious working of the two eves, not only in the performance of conjugate movements, but also during the disjunctive movements e.g. Convergence.
We are all aware that several reflexes in the body e.g. postural reflexes, are unconditioned, i.e. they are predetermined. On the contrary, the binocular reflexes, being a later acquisition in phyiogeny, are conditioned i.e. they are developed post-natally. Out of these binocular reflexes also, the disjunctive fixation reflex, which is meant for carrying out the movement of convergence, is the last to be developed. At birth, there is no convergence. It is developed by the age of six months. Convergence is thus very young phylogenetically, and, therefore, very prone to anomalies, the commonest of which is Convergence Insufficiency.
We know that when an emmetropic person accommodates to see a near object, he also converges to a corresponding amount. To see an object at 25 cm, he uses 4 dioptres of accommodation and 4 metre angles of convergence. Each metre angle is roughly equal to 2 degrees. This normal relationship can often be disturbed. If a person concentrates at an object at 25 cm, adducting prisms (with base outwards) can be interposed without producing diplopia. The strongest prism, base out, that can be thus interposed without production of diplopia, can be a measure of the amount of convergence. This demonstrates the presence of Relative Convergence, which is of great importance in allowing the near work to be done with ease.
| Measurement of Convergence|| |
Convergence can be readily measured by drawing a fine line on a piece of paper and bringing it closer and closer to the eyes, till it appears double, at which point: the distance from the eyes is measured. 100 divided by this distance in centimetres gives a rough measure of convergence in metre angles. But to be accurate, this distance should be measured from the centre of rotation of the eves., which is 14 mm behind the apex of the cornea. This is readily done on the Livingstone's Binocular Gauge, which is calibrated for this purpose. Also the amplitude of convergence can be directly measured on the synoptophore.
| Incidence|| |
In a survey of 660 cases which came for eye testing at the Ophthalmic department of the Medical College Hospital, Indore extending over a period of nine months from 20th July, 1955, the following figures have been found:-
Total number of refraction cases 660
Total number of cases who complained of headache and other symptoms ... 319
Total number of heterophoria cases with symptoms ... 34
Total number of cases of Convergence Insufficiency ... 22
This gives an incidence of 3.6%, among the cases who came for eye testing.
| Etiology|| |
In a series of 158 cases of Convergence Insufficiency dealt with in the Orthoptic section of the Ophthalmic department of the Medical College Hospital, Indore, in 5 years from 1955, the following etiological factors were found:[Table - 1]
This survey shows a marked preponderence of cases, who were not suffering from any other ailment and who were thus primarily having Convergence Insufficiency. All the cases were of the 18 to 25 years age group. Females predominated, being go in number as compared to 68 males.
| Symptoms|| |
Headache, especially on near work, was found to be the most marked symptom. Blurring of the print and difficulty of precision work along with ocular fatigue and watering from the eyes were amongst the other symptoms.
| Treatment|| |
All cases were first diagnosed on the Synoptophore, Binocular gauge, Maddox rod and wing. Cases showing well marked Convergence Insufficiency only ,were picked up for treatment, e.g., a case having a poor fusional amplitude of about 10 on Synoptophore, normal Maddox rod reading and normal or slightly exophoric wing reading, is a good case for treatment of this malady. A medical check up (including a blood examination in suitable cases) was done to find out any gross defect. If such a defect was detected, the case was sent for medical treatment and asked to return at least six weeks after discharge from the medical side.
Great difficulty arises in cases with neuroses. It was found that even after full treatment, they would return after a few weeks with the same symptoms.
Any error of refraction was corrected and such a patient was advised to return only after at least twelve weeks, use of glasses. The orthoptic treatment consists of increasing the fusional amplitude on the Synoptophore. Simple home exercises like bringing a thin rod nearer and nearer his eyes without causing diplopia were also prescribed.
The following assessment of the response to treatment is tabulated below:
Uncorrected Myopia cases. Out of 22 cases, 8 became symptom free after application of suitable glasses. 14 were submitted to treatment. Response was excellent in all cases.
General Debility cases. Out of II cases treated after full medical treatment, only two became symptom free, as shown by a follow up for one year.
Neuroses cases. Out of 24 cases all returned with the same complaint. They were again submitted to treatment. 5 remained symptom free in a one year follow up period.
Others. Out of 101 cases, 49 became symptom free in six weeks, 27 became symptom free in 12 weeks. The rest 25 did not show any improvement.
| Summary|| |
A survey of the response to treatment of 158 cases of Convergence Insufficiency in a period of five years is given.
Thanks are due to the Superintendent of the M. Y. Hospital for allowing me to use the records, and to Miss Chanderwarker for helping me in dealing with the cases.
How much difference you find between the calculated intraocular (calculated by two weights schiotr tono meter readings and using 1955 Friendenwalds' monogram correcting ocular-rigidity slope to find out Po) and the I.O.P. reading by applanation tono meter, which you think (as you said) fails to diagnose low tension glaucomas (due to low ocular rigidity) ?
[Table - 1]