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H Bagga, DS Greenfield, RW Knighton; Scanning Laser Polarimetry With Variable Corneal Compensation In Eyes With Macular Pathology . Invest. Ophthalmol. Vis. Sci. 2002;43(13):250.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Scanning laser polarimetry with variable corneal compensation uses the macula as an intraocular polarimeter to calculate and neutralize corneal birefringence based upon an intact Henle's layer. The purpose of this investigation was to validate this strategy in eyes with macular structural pathology. Methods: The GDx Nerve Fiber Analyzer was modified to enable the measurement of corneal polarization axis and magnitude so that compensation for corneal birefringence is eye specific. Normal subjects and patients with a variety of macular pathologies underwent complete ocular examination, scanning laser polarimetry with variable corneal compensation (SLP-VCC), and direct measurement of the corneal polarization axis (CPA) using a slit lamp-mounted corneal polarimeter. Results: 47 eyes (20 normal, 27 maculopathy) of 47 patients (mean age 59.5 ± 19.2 years, range 24-88) were enrolled. The correlation between CPA measured with corneal polarimetry and SLP-VCC was less in eyes with macular pathology (R2 = 0.24, P = 0.009) compared with normal eyes (R2 = 0.72, P< 0.0001). A difference ≥ 10º was observed between CPA measured using corneal polarimetry and CPA derived using SLP-VCC in 4/20 (20%) normal eyes and 12/27 (44.4%) eyes with various macular pathologies (5 AMD, 3 ERM, 2 CSR, 1 CME, 1 pattern dystrophy). Although no relationship was observed between CPA and 12 retardation parameters obtained with SLP-VCC in normal eyes (P≷0.05), eyes with macular pathology showed a significant association between CPA and average thickness (R2 = 0.27, P = 0.005), ellipse average (R2 = 0.24, P = 0.008), superior average (R2 = 0.24, P = 0.009), inferior average (R2 = 0.28, P = 0.004), and superior integral (R2 = 0.37, P = 0.008) suggesting incomplete corneal compensation. Conclusions: Macular strategies for neutralization of corneal birefringence using SLP-VCC can fail if Henle's layer is disrupted by macular pathology.
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