A classification system has been proposed for myopic maculopathy: grade 0 (no myopic retinal lesions), grade 1 (tessellated fundus), grade 2 (diffuse chorioretinal atrophy (CRA)), grade 3 (patchy CRA), and grade 4 (macular atrophy). Tessellated fundus is defined as the visibility of choroidal vessels around the fovea and arcade vessels due to retinal pigment epithelium hypoplasia of enlarging eyeballs. Contrast sensitivity (CS) detects the difference in light between two adjacent areas or an object against its background. Patients with high myopia may have normal vision but reduced CS. The authors postulate that the association between fundus tessellation and CS is needed to evaluate chorioretinal degeneration and potentially help monitor the progression of pathological myopia. Ninety-eight patients were enrolled in this study, identified from a corneal refractive laser treatment centre. Grade 3 tessellation was the commonest finding in high myopes, whereas grade 0 was commonest in low myopia. The mean degree of myopia showed increased trend across tessellation grades: from -5.06 in grade 0, -5.13 in grade 1, -6.34 in grade 2 and -6.92 in grade 3. The degree of tessellation was significantly associated with preoperative myopia (spherical equivalent) and axial length. There was a decreasing trend of photopic CS from grade 0 (1.67cpd) to grade 3 (1.56cpd). A similar decreasing tendency was also found under mesopic conditions. The hypothetical model is that with increasing myopia, photoreceptors become more widely spaced, leading to post-receptor remodelling resulting in enlarged receptive fields and reduced sensitivity. There may also be a correlation with vascular density. The authors conclude that CS may be a clinical sign for advancing fundus tessellation that is screened for as a means of detecting chorioretinal changes.
Contrast sensitivity in myopic eyes
Reviewed by Kurt Spiteri Cornish
Association between fundus tesselation and contrast sensitivity in myopic eyes.
CONTRIBUTOR
Kurt Spiteri Cornish
Sheffield Teaching Hospitals NHS Trust, London, UK.
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