Concluding Remarks on Meridional Accommodation & Astigmatism.
The questions that were raised above regarding the major problem areas in the correction of astigmatism could not even be contemplated, let alone answered, if there is no awareness of the physiological mechanism of Meridional Accommodation (MA). It is well over 100 years since the theory of MA was strongly advocated by eminent eyecare practitioners and some physiologists in both Europe and the USA. From their observations, these practitioners were forced to conclude that the human visual system must have a physiological means (mechanism) that can accommodate for the astigmatism of the eye (mainly due to the cornea).
The concept of MA was first proposed around the mid eighteen hundreds. Towards the turn of the century, it appears from the literature that clinicians and physiologists alike took serious interest in the subject of MA. However, it is unfortunate that almost a hundred years later, we now have no mention of this important subject in our textbooks for eyecare professionals. The study of MA is the missing link in many misunderstandings that lead to patient-practitioner conflict. I believe the main reason for the marked loss of interest in the study of MA is the intervention of the two world wars. The threads of half a century of work have been lost for a very long time now. Very few reports on the complex subject of MA have been made in the literature in the latter half of the twentieth century.
The anatomical structures involved in the mechanism responsible for meridional accommodation are minute and intricately concealed by those structures that are involved in the normal type of focusing (spherical accommodation). This has made it difficult to prove the existence of MA anatomically. The actions of MA are also quite subtle, making its proof difficult in the clinical setting. Thus those who are responsible for the teaching of refraction could not be convinced of the reality of MA. As the subject of MA is quite complex, the eyecare practitioner as an individual cannot be expected to find his/her own way to an understanding of the subject. How then will the patient, who has a problem with the correction of his/her astigmatism, find a satisfactory solution, if the practitioner has not even been alerted to the presence of MA?
As an eyecare practitioner involved in the correction of refractive errors, I had often been disappointed in my earlier years of practicing as I could not find an explanation for patient complaints that related to the correction of their astigmatism. These complaints would surface despite my honest thinking that I had practiced according to the principles that I was taught and that I had performed to the best of my abilities. My awareness and subsequent studies on the subject of MA have since given me the explanation for my initial failures that I was desperate to find. I now find that even if a complaint does occur, I understand why it has come about and find myself in a much better position to find an appropriate solution.
I believe that the important problems regarding the correction
of astigmatism that I initially encountered in my own practice are
presently being encountered to a variable degree, all over the world.
For this reason, I have delivered a scientific paper at an international
optometry conference held by the Asia Pacific Optometry Congress
(APOC) in Korea in 1997. I was fortunate that the papers-coordinator
had given me the opportunity to speak despite having no prior experience
of lecturing to optometrists. As there are no publications that
I know of that analyse the subject of MA, I have made a modified
paper on the Physiology (Part
I) and Clinical Implications (Part
II) of MA freely available on the Internet. Practitioners can
be referred to these papers for a condensed analysis of these topics.
It is hoped that in time, there will be strong worldwide revival
of the teaching of the subject of MA to the benefit of patients
and practitioners alike.