**2. Medical therapy options**

Greeks who coined the term, using the roots *myein* (to close) and *ops* (eye) to characterize those individuals who narrow their eyelids to improve distance visual acuity, the pinhole effect. The focus of distant parallel rays of light falls anterior to the retinal plane and produces a blurred image in myopia. This situation can arise because either the primary refractive components are too powerful or the globe is too long. Thus, myopia can be due to increased corneal or lenticular curvature, or an increase in the lens index of refraction, as occurs with the develop‐ ment of nuclear sclerosis. More commonly, myopia is the result of axial elongation of the

Myopia is categorized into two groups : (1) low-to-moderate myopia (≤ 6.0 D myoptic spherical equivalent (SE) with or without astigmatism) and (2) high myopia (≥ 6.0 D of myopic SE with

Low-to-moderate myopia, known as physiologic myopia, is generally defined as that state in which the eye is rendered myopic by a combination of its components of refraction. In this situation, the refractive power of the eye (corneal power plus lens power slightly modified by anterior chamber depth (ACD)) and the axial length are such that its posterior focal plane lies anterior to the retina. Each component has a value within its normal curve of distribution. These eyes demonstrate normal anatomy and physiology. Whether the absence of correlation among the elements of refraction occurs by chance or is a heritable trait is unknown at present. Low-to-moderate myopia is also considered as low-to-moderate refractive errors defined as

High myopia, also known pathologic, degenerative or malignant myopia, is related to an eye with an axial length exceeding 25.5 or 26 mm, a refractive error of at least -5.0 D and charac‐

Posterior pole abnormalities typical of high myopia include tessellated fundus, lacquer cracks, diffuse atrophy, patchy atrophy, choroidal neovascularization (CNV), macular atrophy, posterior staphyloma but also straightened and stretched vessels, temporal peripapillary atrophic crescent, hemorrhages, and tilting of the optic disk [48, 52]. Recently, high myopia has been defined as a SE refractive error of at least −6 D associated with characteristic degen‐

As elongation of the globe is a key feature of pathological myopia, an axial length of ≥26.5 mm has been adopted as a biometric definition in clinical trials [122], with recent studies reporting a mean of 29 mm (range 26.8–31.5 mm) [129, 130]. Limit of 25.5 mm of myopic eye has been arbitrary fixed as 25, 25.5, or 26.5 mm [74] with an inferior limit of −6 to −10 D of refractive error, providing a cornea of +43.5 D as average refractive power, in the absence of spherophakia

Of greater interest is the determination of the best cutoff for high myopia. Criteria for high myopia that have been used in previous studies include −5.0, −6.0, −10.0, and −12.0 D and there is no universal definition for high myopia [85, 132]. It is thought that at this level, the risks of secondary complications, such as retinal detachment and glaucoma may increase [103, 117, 132]. There may also be further deteriorations in visual field, central visual acuity, increased

erative changes which are more seen in eyes with myopic SE exceeding 8 D.

risks of irregular astigmatism, keratoconus, and peripheral visual field defects.

posterior segment of the eye.

214 Advances in Eye Surgery

myopia less than 6.0 diopters (D).

or without astigmatism (www.medpagetoday.com).

teristic degenerative changes (eachers%20stangov.uk).

or nuclear cataract (eachers%20stangov.uk).

Medical therapy options include eyeglasses (spectacles), contact lenses, and observation. Individuals with asymptomatic myopia may not need eyeglass correction except for activities such as driving or school work. Eyeglasses are the simplest and safest means of correcting myopia; therefore, eyeglasses should be considered before contact lenses or refractive surgery [12]. Contact lenses are used for many reasons. Contact lenses provide better, large field of vision, a greater comfort, and an improved quality of vision. Only contact lenses can give optimal visual function in some conditions such as high myopia, symptomatic anisometropia, aniseikonia, irregular corneal surface, or shape. Further, contact lenses are beneficial in managing unilateral myopia, and some special occupational needs (www.rutzeneye.com).

Spectacles and contact lenses are conservative optical methods. They each have functional limitations such as the problems encountered in wearing spectacles when showering or playing sports, such as individuals involved in certain sports and hazardous activities in which there is risk of eye trauma. Carrying contact lenses solutions and storage solutions can be inconvenient, and wearing contact lenses can increase the risk of corneal infection [106].
