Eye-strain

Eye strain in one form or the other is very common. Errors of refraction, especially that of small amount, anomalies of accommodation and convergence, and a lack of balance between the extrinsic ocular muscles, are the unsuspected causes of much discomfort. As a general rule most distress is caused by errors so slight that they readily escape detection unless they are looked for specifically. It’s not the error itself which causes the trouble so much as the continuous effort called forth automatically in an attempt to correct it. The patient generally protests that his vision is excellent, but examination will show that an unsuspected small error of refraction or a slight degree of muscular imbalance is present, and its correction will frequently result in an equally unexpected and dramatic relief.

The normal eye is adapted to receive on the retina clearly defined images of a distant object without effort or strain, but when attention is turned to objects near at hand, the refractive power is altered by an effort of the ciliary muscle, while at the same time the eyes converge upon the object of attention by the internal recti muscles. These two actions are synkinetic, in that, these are controlled by the same nerve and in normal circumstances they are continuously related to each other in degree. Whenever these ideal conditions are upset in one way or the other, strain tends to result. If, in addition to the longsightedness or shortsightedness, the optical systems of the two eyes are different so that the correcting effort has to be unevenly distributed, the strain will be greater, and if, again, astigmatism co-exists so that the refraction of one or both eyes is irregular, a further complication is introduced. Where the extraocular muscles are incorrectly balanced, so that the eyes at rest are not parallel in direction, the effort to bring them into line in order to obtain binocular vision is another cause of strain.

Pain in eyes unconnected with inflammation is generally due to eye-strain and rarely due to a deep-seated disease. It is usually mild and aching, but may on occasion be severe and acute; it may be situated within the eyes or be located more deeply in orbits, or spreading there from, and is referred as a general headache. Blepharitis or conjunctivitis in children should always suggest an examination of refraction. The commonest symptom associated with eye-strain is headache. It may be localized around the region of the eyes; it may be frontal, temporal, vertical or occipital, or the pain may extend down the neck or even into the arms. It is usually associated with the use of the eyes, and makes itself most evident in the evening after a day’s work. The headache of eye-strain is difficult to diagnose with certainty; the only rational course to adopt is to get your examined as a matter of routine in all cases wherein such an origin might be suspected. It is true that eye-strain may cause much worry and unhappiness, and it is certainly the case that it may considerably lower the general vitality.

In the ocular treatment of these ocular conditions the greatest essential is accuracy. Indeed it happens that a patient with a gross error and suffering no constitutional disability there from but merely complaining of defective vision will be introduced to the headache and annoyances of eye-strain for the first time after he has received his glasses, because his larger error has been almost, but not quite corrected, leaving him in the position of one with a small error. Stress has been laid upon the large part played in the symptomatology of refractive errors by smaller defects, but every small error by no means requires correction. Provision of spectacles to young hypermetropes with small errors, deprives them of the stimulus to accommodate. Similarly, patients with negligible refractive errors, particularly young persons who are commencing studies or clerical work but who are suffering from a muscular deficiency which can be put right by adequate visual hygiene or exercises, may not be prescribed glasses.

“Many symptoms which are apparently caused by refractive errors or muscular anomalies would give no trouble in the ordinary course of events and become apparent only because of ill-health or on attempting to more than the individual is capable of accomplishing with ease; a frequent instance of this is the troubles of which many children complain when commencing the routine of school life. If a rest and general tonic treatment are prescribed, these symptoms frequently disappear without any help in the form of glasses. The ideal treatment, of course, may be to combine the two. The providing of suitable lenses is not sufficient treatment in itself; the eye doctor may look into the activities of the patient – his habits, his exercise, and the manner and amount of his work. The prescription of glasses is therefore not merely a matter of placing lenses in front of a patient and ordering those which give him the highest visual acuity. It is, on the contrary, a complex matter depending on a sound theoretical knowledge of the optical system of the eye and an ability to determine accurately its refractive peculiarities, its accommodative power, and the condition of its associated muscles”, explains ophthalmic surgeon Dr. Maneesh Kumar. more