Optical Coherence Tomography Imaging of the Posterior Segment in High Myopia.

The prevalence of myopia in East Asia and Singapore in particular is amongst the highest in the world, with estimates ranging from 30-70% of the general population. Up to 30% of these are high myopes. High myopia is associated with degenerative changes in the fundus. It may also be associated with vision-threatening complications such as macular holes. The pathogenesis of macular holes in high myopes is not completely understood but is postulated to include a combination of anterior vitreous traction and posterior staphyloma formation and axial elongation. These forces lead to degenerative changes at the macula, including foveal detachment and retinoschisis that precede the formation of lamellar or full thickness macular holes. These changes are difficult to detect either clinically or by conventional imaging such as ultrasound, making efforts to correct them in the early stages with surgery difficult. High myopia is also associated with a two- to threefold increase in risk of developing glaucoma. However, the diagnosis of glaucoma in high myopes is difficult as many of the pathological changes in the myopic eye mimic those seen in glaucoma. The myopic optic disc in particular is notoriously difficult to differentiate from the glaucomatous disc. Currently, the diagnosis is highly subjective, relying on observations of the clinical appearance of the disc or on disc photos.Optical coherence tomography (OCT) is an evolving technology that relies on time delays of reflected or backscattered light and interferometry to yield cross-sectional images of the retina and optic disc. The Stratus OCT is the latest model and has been demonstrated to be able to yield images with a resolution comparable to that of histology. It is thus potentially useful in assessing degenerative changes occurring in the myopic fundus, in evaluating the early changes preceding macular hole formation, and in providing objective measures of various disc parameters to aid in diagnosing glaucoma in hig