Effect of corneal polarization axis on assessment of retinal nerve fiber layer thickness by scanning laser polarimetry

David Greenfield, Robert W. Knighton, XiangRun Huang

Research output: Contribution to journalArticle

215 Citations (Scopus)

Abstract

PURPOSE: Scanning laser polarimetry uses an anterior segment compensating device that assumes a fixed axis of corneal birefringence, which we call the corneal polarization axis. The purpose of this investigation was to establish the distribution of corneal polarization axes among a population of normal eyes and to evaluate the relationship between corneal polarization axis and posterior segment retardation. METHODS: We constructed a noninvasive slit lamp-mounted device incorporating two crossed linear polarizers and an optical retarder in order to measure the slow axis of corneal birefringence. Normal subjects underwent corneal polarization axis measurement. A subset of eyes underwent scanning laser polarimetry of the peripapillary retinal nerve fiber layer (n = 32) and macula (n = 29), and retardation measurements were evaluated in each group. RESULTS: One hundred eighteen eyes of 63 normal subjects (35 female, 28 male) underwent corneal polarization axis measurement (mean age, 45.5 ± 17.1 years). Six eyes (5.1%) demonstrated unmeasurable corneal polarization. In the remaining 112 eyes, the mode of the corneal polarization axis distribution was 10 to 20 degrees nasally downward (range, 90 degrees nasally downward to 54 degrees nasally upward). A significant (P < .0001) correlation was observed between fellow eyes (R2 = .52), with a mean difference of 11.2 ± 10.5 degrees (range, 0-52 degrees). Corneal polarization axis was significantly associated (R2 = .52-.84) with retinal nerve fiber layer and macula summary retardation parameters (average thickness, ellipse average, superior and inferior average, superior and total integral; P < .0001 for all groups).CONCLUSIONS: The mean corneal polarization axis among normal corneas is nasally downward; however, considerable intraindividual and interindividual variability exists. The linear relationship between corneal polarization axis and posterior segment retardation parameters is responsible, in part, for the wide distribution of retinal nerve fiber layer thickness data generated by scanning laser polarimetry. Copyright (C) 2000 Elsevier Science Inc.

Original languageEnglish
Pages (from-to)715-722
Number of pages8
JournalAmerican Journal of Ophthalmology
Volume129
Issue number6
DOIs
StatePublished - Jun 1 2000

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Scanning Laser Polarimetry
Nerve Fibers
Birefringence
Equipment and Supplies
Cornea

ASJC Scopus subject areas

  • Ophthalmology

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Effect of corneal polarization axis on assessment of retinal nerve fiber layer thickness by scanning laser polarimetry. / Greenfield, David; Knighton, Robert W.; Huang, XiangRun.

In: American Journal of Ophthalmology, Vol. 129, No. 6, 01.06.2000, p. 715-722.

Research output: Contribution to journalArticle

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abstract = "PURPOSE: Scanning laser polarimetry uses an anterior segment compensating device that assumes a fixed axis of corneal birefringence, which we call the corneal polarization axis. The purpose of this investigation was to establish the distribution of corneal polarization axes among a population of normal eyes and to evaluate the relationship between corneal polarization axis and posterior segment retardation. METHODS: We constructed a noninvasive slit lamp-mounted device incorporating two crossed linear polarizers and an optical retarder in order to measure the slow axis of corneal birefringence. Normal subjects underwent corneal polarization axis measurement. A subset of eyes underwent scanning laser polarimetry of the peripapillary retinal nerve fiber layer (n = 32) and macula (n = 29), and retardation measurements were evaluated in each group. RESULTS: One hundred eighteen eyes of 63 normal subjects (35 female, 28 male) underwent corneal polarization axis measurement (mean age, 45.5 ± 17.1 years). Six eyes (5.1{\%}) demonstrated unmeasurable corneal polarization. In the remaining 112 eyes, the mode of the corneal polarization axis distribution was 10 to 20 degrees nasally downward (range, 90 degrees nasally downward to 54 degrees nasally upward). A significant (P < .0001) correlation was observed between fellow eyes (R2 = .52), with a mean difference of 11.2 ± 10.5 degrees (range, 0-52 degrees). Corneal polarization axis was significantly associated (R2 = .52-.84) with retinal nerve fiber layer and macula summary retardation parameters (average thickness, ellipse average, superior and inferior average, superior and total integral; P < .0001 for all groups).CONCLUSIONS: The mean corneal polarization axis among normal corneas is nasally downward; however, considerable intraindividual and interindividual variability exists. The linear relationship between corneal polarization axis and posterior segment retardation parameters is responsible, in part, for the wide distribution of retinal nerve fiber layer thickness data generated by scanning laser polarimetry. Copyright (C) 2000 Elsevier Science Inc.",
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