Singapore Optometric Association

IMI – Defining and Classifying Myopia: A Proposed Set of Standards for Clinical and Epidemiologic Studies

PURPOSE. We provide a standardized set of terminology, definitions, and thresholds of myopia
and its main ocular complications.
METHODS. Critical review of current terminology and choice of myopia thresholds was done to
ensure that the proposed standards are appropriate for clinical research purposes, relevant to
the underlying biology of myopia, acceptable to researchers in the field, and useful for
developing health policy.
RESULTS. We recommend that the many descriptive terms of myopia be consolidated into the
following descriptive categories: myopia, secondary myopia, axial myopia, and refractive
myopia. To provide a framework for research into myopia prevention, the condition of ‘‘premyopia’’
is defined. As a quantitative trait, we recommend that myopia be divided into myopia
(i.e., all myopia), low myopia, and high myopia. The current consensus threshold value for
myopia is a spherical equivalent refractive error -0.50 diopters (D), but this carries
significant risks of classification bias. The current consensus threshold value for high myopia
is a spherical equivalent refractive error -6.00 D. ‘‘Pathologic myopia’’ is proposed as the
categorical term for the adverse, structural complications of myopia. A clinical classification is
proposed to encompass the scope of such structural complications.
CONCLUSIONS. Standardized definitions and consistent choice of thresholds are essential
elements of evidence-based medicine. It is hoped that these proposals, or derivations from
them, will facilitate rigorous, evidence-based approaches to the study and management of
myopia.

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