Journal of Ophthalmology (Jun 2016)
Topography of inferior oblique muscle’s insertion to the sclera
Abstract
Background. Object’s localization on the surface of the eyeball is traditionally performed by measuring the distance to other objects. These measurements are made in linear values straight on the eyeball surface. However, the size of the eyeball in every individual is different depending on the age and refraction. When using only linear measurements, it is impossible to localize correctly any given object on the eyeball surface without regard to the eye’s size. As a rule, all distances are given for an average size eye of an adult, 12 mm in radius. Since the sizes of eyeballs of patients, especially of children, are varied depending on the age and refraction, corresponding tables of distances should be done for different eyeball sizes when localizing the zones of insertion of extraocular muscles. The purpose of the present paper was to specify the localization of inferior oblique muscle’s insertion to the sclera using spherical coordinate system. Materials and Methods. 20 eyes of 18 patients were examined. Radius of the eyeballs ranged from 9.5 to 12.5 mm. The examinations were performed during strabismus surgeries. To transform the linear values into spherical coordinates, Computed Software for Calculating the Coordinates of Objects on the Surface of the Eyeball Model was used. To map out anatomical formations on the eyeball surface, we created a map of the eyeball surface in rectangular cylindrical projection of ophthalmographical spherical coordinate system (OSCC). Results. Inferior oblique muscles insertion sites are localized between 80° and 120° longitude and between 25° and -90° latitude. However, the major area of inferior muscle insertion is between 80° and 115° longitude and between -10° and -85° latitude. Herewith, the anterior border of insertion area is mainly located within the range between 100° and 115° longitude and posterior borders are located between 80° and 100° longitude. As for latitude, it is mainly in the area between -10° and -30° for anterior borders and -55° and -85°for posterior borders. The relative longitude of the insertion site is also widely ranged, from minimal (No 5, 14, 20) to maximal (No 8, 16, 17) values. Conclusions. The use of ophthalmographic spherical coordinate system enables to standardize the localization of inferior oblique muscle insertion sites without regard to the size of the eyeball. The possible localization of the inferior oblique muscle insertion to the sclera was admeasured within the range mainly between 80° and 115° longitude and -10° and -85° latitude.
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