Science: Accommodation: The role of the external muscles of the eye: A consideration of refractive errors in relation to extraocular malfunction
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Entering edit mode
8 months ago
david 3.9k
@david_fe

This is, in my opinion, a poorly written article. However, now that I have read it and, without being able to help myself, entirely re-written the abstract, I feel obligated to share it. What follows bears little resemblance to the original. On one hand I apologize to the author, and on the other hand I thank him for taking the initiative to publish on this important topic.


The need to better understand the cause of myopia (nearsightedness), hyperopia (farsightedness) and similar refractive errors has led to dissatisfaction with the mainstream theory (proposed by Hermann von Helmholtz in 1867 and unchallenged for more than 100 years) which states that the lens is the sole agent in visual accommodation. Researchers are now (finally) making a serious effort to examine the possibility that other parts of the eye are also conjointly involved in accommodation.

Around half-a-century ago, Robert Brooks Simpkins suggested that the mechanical features of the human eye were precisely such as to allow for a lengthening of the globe when the eye accommodated. In fact, William H. Bates, MD, proposed the same idea more than 100 years ago.

This theory is both imaginative and comprehensive and deserves serious consideration. It is submitted here that accommodation is in fact a multi-fold process, and that although involving the lens, is achieved primarily by means of a give - and - take interplay between adducting and abducting external muscles, whereby an elongation of the eyeball is brought about by a stretching of the delicate elastic fibres immediately behind the cornea.

The three muscles responsible for convergence (superior, internal and inferior recti) all pull from in front backwards, while of the three abductors (external rectus and the two obliques) the obliques pull from behind forwards, allowing for an easy elongation as the eye turns inwards and a return to its original length as the abducting muscles regain their former tension, returning the eye to distance vision.

In refractive errors, the altered length of the eyeball disturbs the harmonious give - and - take relationship between adductors and abductors. Such stresses are likely to be perpetuated and the error exacerbated. Speculation is not directed towards a search for a possible cause of the muscular imbalance, since none is suspected. Muscles not used rapidly lose tone, as evidenced after removal of a limb from plaster. Early attention to the need for restorative exercise is essential and results usually impressive.

Equally important is the recognition that psychological stress can lead to chronic tension in these extraocular muscles, and that by the same mechanism described above, this tension leads to persistent errors of refraction.

We propose that flexibility, proper balance and lack of chronic tension in the external muscles of the eyes is essential for maintaining good eyesight. If this theory is correct, it also means presbyopia can be avoided and with it the supposed necessity of glasses in middle and later life.

Early attention to the development of good habits (such as relaxing the eyes, frequent change of focus, etc.) is believed to support ocular well-being and obviate the reliance on glasses.

SOURCE:
Accommodation: The role of the external muscles of the eye: A consideration of refractive errors in relation to extraocular malfunction - PubMed

presbyopia myopia:near-sighted • 149 views
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