From Spain and 2018.
“Because of the incipient surgical techniques at the time, the question of EOM involvement in myopia was prematurely abandoned in the early 20th century. As a result, the participation of the extra and intraocular muscles in scleral distension has not been appropriately dealt with.”
" The EOMs are able to contract with fiber shortening (isotonic contraction) or without fiber shortening (isometric contraction). By a combination of both types of contraction, the eye rotates around two areas known as space and body centrodes, situated 13.5 mm behind the cornea and nasally displaced from the geometrical center of the globe (9). To accomplish the formidable task of accessing virtually infinite positions, the EOMs are endowed with unusual physiological characteristics that derive from their expression of specific contractile proteins including, myosin heavy chain isoforms, myosin light chains, tropomyosin, and troponin, connected in parallel or in series, and other special features. The EOM myofiber continuum hypothesis combined with the non-linearity of eye muscle contractile properties would explain a total central nervous system (CNS) control of muscle tone and eye position and velocity. In EOM there seems to be a continuum of myofiber types. Each myosin heavy and light chain isoform results in a distinct shortening velocity, which would translate in an increased plasticity in the control of muscle force generation (10)."
"It can be argued that an anterior group of recti muscles acting jointly with isometrical contraction would fix the eye, while the ciliary muscle would pull anteriorly the choroid. At the same time, the joint action of both oblique muscles, acting isotonically, would pull apart the posterior pole, with the result of eye enlargement. The angle formed by the obliques and the ocular axis ranges in the low fifties [51° for inferior oblique (IO) and 54° for SO]. Convergence is the position of the globe in which the elevator and depressor action of the obliques is maximal. This is the near (reading) position with a synergy with accommodation (and miosis). In this position, the four recti can maintain the globe fixed with a tonic grip, while the maximal conjunct action of the obliques pulls the posterior pole apart, causing the elongation of the globe in its post-equatorial half ( Figure 1 ). Scleral pulling would secondarily cause choroidal stretching and rarefaction.
Figure 1 Eye and extraocular muscles relationship in myopia. (A) Position of the insertion of the IO in the posterior pole in relation to the fovea. Measurements in millimetres: (a) Wolf 1954; (b) Massri 1963; © Whitnall 1932. [Inspired by drawings in references (11,12)]; (B) isometric contraction of the anterior muscles (4 recti) maintains the anterior segment fixed, while the metric contraction of the inferior and superior obliques pulls apart the posterior pole, enlarging the globe at expenses of the retro-equatorial half. The ciliary muscle, mainly the longitudinal portion, acts contracting isotonically as a tensor of the choroid; © convergence of the globe is the position of maximal effect of the obliques. These are coincidentally the reading position and general near vision, with the synkinesis accommodation, convergence, and miosis.
A recent study relates severe IO overaction to thinning of the subfoveal choroid (wow!!), attributable to external mechanical effect (13). Myopia and near-work are statistically related in many studies, although also here are appearing divergent results (14,15)."