The history of the postural prism is easy to reconstitute because it spreads out only on one hundred of years and take place only in Europe.
All the therapists who today prescribe postural prisms are the heirs of this history and we are sure that they will have it progress again and again.

     The first author who indicated the possibility of modifying " the balance " (as one said then) of an animal by the wearing of a prism in front of eyes is Ilya Fadeevitch Tsion (Elie de Cyon as he enjoyed being called) a Russian doctor, professor of physiology at the military Academy of Saint-Petersburg (E. de Cyon, 1911).

     The first therapist who used prisms of weak dioptric power to look after patients suffering from dizziness is G.P. Utermöhlen (1947), Dutch ORL. He put the basis of his prisms at 0 ° or 180 °.

     Jean-Bernard Baron, French ophthalmologist, resumed this technique of Utermöhlen (1952) and he enlightened an amazing aspect of the oculomotor system: very small displacement of an eyeball has more postural effects than an important one (1955). Sometimes Baron put the basis of the prism at 55° or 125°.

     Orlando Alves Da Silva in the beginning of the 80s proposes, with Da Cunha (1986), a postural typology allowing to determine, in a short time, an effective position of the basis of the prism according to 5 typological categories, very well explained and presented by .Gabriel Elie (2003).

     Claudie Marucchi, Parisian ophthalmologist, went to the Lisbon school, in about 1985. After her return we worked together and we noticed that the indications of the Portuguese were superior to what proposed Baron, but "that did not always work", doubtless the 5 typological categories do not cover all the cases. That is why we spread our researches to all the preferential action directions of oculomotor muscles, what led us to discover the Law of the Canals (1988) which is only a generalization of the work of Orlando Da Silva and Jean-Bernard Baron. But the technique of the postural clinical examination to find the best position of the prism basis is sharply heavier than the quick way of Lisbon, and especially it requires an adapted installation that, most of the time, does not correspond to a cabinet of ophthalmologist or general practitioner. Practised in the required conditions and by taking enough time, this technique is excellent and gives results, which cannot be less good than those of the other methods because it is the heir of them! Even it justifies the daily practice of a fast postural clinical examination to prescribe the prism because the Law of the Canals shows that there is one chance out two to prescribe a correct position of the prism basis, even if it is not the best. It is so useless to try to justify the practice of the fast exam of Lisbon by other considerations.

     Claudie Marucchi and the orthoptists who worked with her were bothered by the notion of "directional scotoma" which was never revealed by another technique than the examination with the synoptophore. Now this device, it is very well known, was not built for studying visual field but phorias. A prolonged practice searching for the "directional scotoma" with the synoptophore convinced Marucchi and her team that Orlando Da Silva had put the finger on a variation of the oculomotor imbalance in the positions of version. What was confirmed by a series of rigorous studies on "coordimetry of version" (Marucchi, 1987; Calage et al ., 1994; Coupin and Lévy, 2002; Marucchi and Zamfiresco, 2004; Zamfiresco et al ., 1995). We still do not know what is the mysterious "directional scotoma", but we proved that exists a worsening of the oculomotor imbalance in position of version, able to explain the phenomena observed with the synoptophore. So the only real difference between the Parisian team and the team of Lisbon is the forsaking of the synoptophore, which does not concern postural prisms, themselves but only their prescription.

References

Baron J.B. (1955) Muscles moteurs oculaires, attitude et comportement locomoteur des vertébrés. Thèse de Sciences, Paris, 158 pages,.
Baron J.B., Fowler E. (1952) Prismatic lenses for vertigo and some experimental background of the role of the extrinsic ocular muscles in desequilibrium. Trans. Am. Acad. Ophthal. Oto-laryngol., 56, 916-926.
Calage V., Weber B., Marucchi C. (1994) Variabilité de la coordimétrie de version chez l’adulte sain. Rev. d’ONO, 28, 19-20.
Coupin I., Levy M. (2002) La coordimétrie de version objective cliniquement l’inhibition de l’oculomotricité due aux malocclusions. Huitiéme journées de posturologie clinique, Bruxelles, 6-7 décembre 2002,
Cyon E. de (1911) L’oreille organe d’orientation dans le temps et dans l’espace. Alcan (Paris), 298 pages.
Da Cunha Martins H, Alves da Silva O. (1986) Disturbances of binocular function in the postural deficiency syndrome. Agressologie, 27(1):63-7,
Elie G. (2003) Le système proprioceptif, pour mieux le comprendre. [http://pmgagey.club.fr/Lisbonne.htm]
Gagey P.M. (1988) La loi des canaux. Agressologie, 29, 691-692,.
Marucchi C. (1987) Coordimétrie de version, complément du bilan postural. Agressologie, 28, 949-952,
Marucchi C., Zamfiresco F. (2004) Vision et posture. In P.M. Gagey & B. Weber (Eds) Posturologie. Régulation et dérèglements de la station debout. Masson, Paris, 128-134
Utermöhlen G.P. (1947) De prismatherapie getoest aan 160 lijders aan het syndroom van Ménière. Ned. Tijdschr. Geneeskd., 91: 124-126.
Zamfiresco F., Weber B., Marucchi C., Habif M., Coupin I. (1995) Un coordimètre adapté à l’examen posturologique. In PM Gagey & B Weber (Eds) Entrées du système postural fin, Masson, Paris, 25-32.