Peripheral light-focusing

Measurement reliability and correlations with ocular dimensions

John D Twelker, Shauna C. Harbison, Ian L. Bailey

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

Purpose. When a beam of light is directed toward the temporal limbus from an angle of about 120° temporal to the primary line of sight, an illuminated patch appears on the sclera at the nasal limbus. An optical apparatus was developed for measuring the angular range of this optical phenomenon, often called the temporal catchment angle. It is possible that the temporal catchment angle or its correlates could serve as a key risk factor for the development of pterygia or cortical cataract. Methods. We built an apparatus that allows variation in the angle of a beam directed toward the temporal limbus. Two examiners measured the angular catchment range over which peripheral light focusing occurred for the right eyes of 30 subjects. Other anterior segment dimensions, including palpebral aperture height, refractive error, central and peripheral corneal power, anterior chamber depth, and corneal diameter, were measured. Results. There was no statistically or clinically significant difference between the repeated measures of the examiners. The mean temporal catchment angle was 17.1° (SD, 6.5). The intraobserver and interobserver 95% limits of agreement were 6.2 and 9.7°, respectively. The mean posterior limit was 121.0° (SD, 5.5), and the mean anterior limit was 104.1° (SD, 6.5) from the primary line of sight. The temporal catchment angle was positively correlated with central corneal power (R2 = 0.18; p = 0.02), peripheral corneal power (R2 = 0.18; p = 0.01), anterior chamber depth (R2 = 0.29; p = 0.002), and corneal diameter (R2 = 0.37; p = 0.002). Using multivariate linear regression analysis, we determined that central corneal power in the horizontal meridian and corneal diameter, in combination, best predicted the magnitude of the temporal catchment angle (R2 = 0.37; p = 0.0001). Conclusions. We have developed a reliable method of measuring the temporal catchment angle using a new head-mounted instrument. The temporal catchment angle was highly correlated with central corneal power and corneal diameter, in combination. The temporal catchment angle or its correlated ocular dimensions could be used to investigate risk factors for pterygia and cortical cataract.

Original languageEnglish (US)
Pages (from-to)94-100
Number of pages7
JournalOptometry and Vision Science
Volume82
Issue number2
DOIs
StatePublished - Feb 2005

Fingerprint

Light
Pterygium
Anterior Chamber
Cataract
Optical Phenomena
Meridians
Sclera
Refractive Errors
Eyelids
Nose
Linear Models
Head
Regression Analysis

Keywords

  • Cornea
  • Peripheral light-focusing
  • Pterygium
  • Temporal catchment angle
  • Ultraviolet radiation

ASJC Scopus subject areas

  • Ophthalmology

Cite this

Peripheral light-focusing : Measurement reliability and correlations with ocular dimensions. / Twelker, John D; Harbison, Shauna C.; Bailey, Ian L.

In: Optometry and Vision Science, Vol. 82, No. 2, 02.2005, p. 94-100.

Research output: Contribution to journalArticle

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abstract = "Purpose. When a beam of light is directed toward the temporal limbus from an angle of about 120° temporal to the primary line of sight, an illuminated patch appears on the sclera at the nasal limbus. An optical apparatus was developed for measuring the angular range of this optical phenomenon, often called the temporal catchment angle. It is possible that the temporal catchment angle or its correlates could serve as a key risk factor for the development of pterygia or cortical cataract. Methods. We built an apparatus that allows variation in the angle of a beam directed toward the temporal limbus. Two examiners measured the angular catchment range over which peripheral light focusing occurred for the right eyes of 30 subjects. Other anterior segment dimensions, including palpebral aperture height, refractive error, central and peripheral corneal power, anterior chamber depth, and corneal diameter, were measured. Results. There was no statistically or clinically significant difference between the repeated measures of the examiners. The mean temporal catchment angle was 17.1° (SD, 6.5). The intraobserver and interobserver 95{\%} limits of agreement were 6.2 and 9.7°, respectively. The mean posterior limit was 121.0° (SD, 5.5), and the mean anterior limit was 104.1° (SD, 6.5) from the primary line of sight. The temporal catchment angle was positively correlated with central corneal power (R2 = 0.18; p = 0.02), peripheral corneal power (R2 = 0.18; p = 0.01), anterior chamber depth (R2 = 0.29; p = 0.002), and corneal diameter (R2 = 0.37; p = 0.002). Using multivariate linear regression analysis, we determined that central corneal power in the horizontal meridian and corneal diameter, in combination, best predicted the magnitude of the temporal catchment angle (R2 = 0.37; p = 0.0001). Conclusions. We have developed a reliable method of measuring the temporal catchment angle using a new head-mounted instrument. The temporal catchment angle was highly correlated with central corneal power and corneal diameter, in combination. The temporal catchment angle or its correlated ocular dimensions could be used to investigate risk factors for pterygia and cortical cataract.",
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N2 - Purpose. When a beam of light is directed toward the temporal limbus from an angle of about 120° temporal to the primary line of sight, an illuminated patch appears on the sclera at the nasal limbus. An optical apparatus was developed for measuring the angular range of this optical phenomenon, often called the temporal catchment angle. It is possible that the temporal catchment angle or its correlates could serve as a key risk factor for the development of pterygia or cortical cataract. Methods. We built an apparatus that allows variation in the angle of a beam directed toward the temporal limbus. Two examiners measured the angular catchment range over which peripheral light focusing occurred for the right eyes of 30 subjects. Other anterior segment dimensions, including palpebral aperture height, refractive error, central and peripheral corneal power, anterior chamber depth, and corneal diameter, were measured. Results. There was no statistically or clinically significant difference between the repeated measures of the examiners. The mean temporal catchment angle was 17.1° (SD, 6.5). The intraobserver and interobserver 95% limits of agreement were 6.2 and 9.7°, respectively. The mean posterior limit was 121.0° (SD, 5.5), and the mean anterior limit was 104.1° (SD, 6.5) from the primary line of sight. The temporal catchment angle was positively correlated with central corneal power (R2 = 0.18; p = 0.02), peripheral corneal power (R2 = 0.18; p = 0.01), anterior chamber depth (R2 = 0.29; p = 0.002), and corneal diameter (R2 = 0.37; p = 0.002). Using multivariate linear regression analysis, we determined that central corneal power in the horizontal meridian and corneal diameter, in combination, best predicted the magnitude of the temporal catchment angle (R2 = 0.37; p = 0.0001). Conclusions. We have developed a reliable method of measuring the temporal catchment angle using a new head-mounted instrument. The temporal catchment angle was highly correlated with central corneal power and corneal diameter, in combination. The temporal catchment angle or its correlated ocular dimensions could be used to investigate risk factors for pterygia and cortical cataract.

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