The ISNT Rule: How Often Does It Apply to Disc Photographs and Retinal Nerve Fiber Layer Measurements in the Normal Population?

Linda Yi Chieh Poon, David Solá-Del Valle, Angela V. Turalba, Iryna A. Falkenstein, Michael Horsley, Julie H. Kim, Brian J. Song, Hana Takusagawa, Kaidi Wang, Teresa C. Chen

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

Purpose To determine what percentage of normal eyes follow the ISNT rule, and whether ISNT rule variants may be more generalizable to the normal population. Design Cross-sectional study. Methods SETTING: Institutional setting. STUDY POPULATION: Total of 110 normal subjects. OBSERVATION PROCEDURES: Neuroretinal rim assessments from disc photographs and retinal nerve fiber layer (RNFL) thickness measurements from spectral-domain optical coherence tomography. MAIN OUTCOME MEASURES: The percentages of subjects that obeyed the ISNT rule and its variants. Results The ISNT rule is only valid for 37.0% of disc photograph rim assessments and 43.8% of RNFL measurements. Deviation of the nasal sector from the expected ISNT pattern was a major cause for the ISNT rule not being obeyed for both rim and RNFL assessments. Specifically, 10.9% of subjects had wider nasal rims than the inferior rims, 29.4% had wider nasal rims than the superior rims, 14.7% had narrower nasal rims than the temporal rims, and 42.9% had thinner nasal RNFLs compared to the temporal quadrant. Exclusion of the nasal quadrant from the ISNT rule significantly increased the validity of ISNT variant rules, with 70.9% and 76.4% of disc photographs following the IST rule and the IS rule, respectively. Similarly, for RNFL thickness, 70.9% and 71.8% of patients followed the IST and IS rule, respectively. Conclusions The ISNT rule is only valid for about a third of disc photographs and less than half of RNFL measurements in normal patients. ISNT rule variants, such as the IST and IS rule, may be considered, as they are valid in more than 70% of patients.

Original languageEnglish (US)
Pages (from-to)19-27
Number of pages9
JournalAmerican Journal of Ophthalmology
Volume184
DOIs
StatePublished - Dec 1 2017
Externally publishedYes

Fingerprint

Nerve Fibers
Nose
Population
Optical Coherence Tomography
Cross-Sectional Studies
Observation

ASJC Scopus subject areas

  • Ophthalmology

Cite this

Poon, L. Y. C., Solá-Del Valle, D., Turalba, A. V., Falkenstein, I. A., Horsley, M., Kim, J. H., ... Chen, T. C. (2017). The ISNT Rule: How Often Does It Apply to Disc Photographs and Retinal Nerve Fiber Layer Measurements in the Normal Population? American Journal of Ophthalmology, 184, 19-27. https://doi.org/10.1016/j.ajo.2017.09.018

The ISNT Rule : How Often Does It Apply to Disc Photographs and Retinal Nerve Fiber Layer Measurements in the Normal Population? / Poon, Linda Yi Chieh; Solá-Del Valle, David; Turalba, Angela V.; Falkenstein, Iryna A.; Horsley, Michael; Kim, Julie H.; Song, Brian J.; Takusagawa, Hana; Wang, Kaidi; Chen, Teresa C.

In: American Journal of Ophthalmology, Vol. 184, 01.12.2017, p. 19-27.

Research output: Contribution to journalArticle

Poon, LYC, Solá-Del Valle, D, Turalba, AV, Falkenstein, IA, Horsley, M, Kim, JH, Song, BJ, Takusagawa, H, Wang, K & Chen, TC 2017, 'The ISNT Rule: How Often Does It Apply to Disc Photographs and Retinal Nerve Fiber Layer Measurements in the Normal Population?', American Journal of Ophthalmology, vol. 184, pp. 19-27. https://doi.org/10.1016/j.ajo.2017.09.018
Poon, Linda Yi Chieh ; Solá-Del Valle, David ; Turalba, Angela V. ; Falkenstein, Iryna A. ; Horsley, Michael ; Kim, Julie H. ; Song, Brian J. ; Takusagawa, Hana ; Wang, Kaidi ; Chen, Teresa C. / The ISNT Rule : How Often Does It Apply to Disc Photographs and Retinal Nerve Fiber Layer Measurements in the Normal Population?. In: American Journal of Ophthalmology. 2017 ; Vol. 184. pp. 19-27.
@article{227dc49439f64595ae2faa7676954943,
title = "The ISNT Rule: How Often Does It Apply to Disc Photographs and Retinal Nerve Fiber Layer Measurements in the Normal Population?",
abstract = "Purpose To determine what percentage of normal eyes follow the ISNT rule, and whether ISNT rule variants may be more generalizable to the normal population. Design Cross-sectional study. Methods SETTING: Institutional setting. STUDY POPULATION: Total of 110 normal subjects. OBSERVATION PROCEDURES: Neuroretinal rim assessments from disc photographs and retinal nerve fiber layer (RNFL) thickness measurements from spectral-domain optical coherence tomography. MAIN OUTCOME MEASURES: The percentages of subjects that obeyed the ISNT rule and its variants. Results The ISNT rule is only valid for 37.0{\%} of disc photograph rim assessments and 43.8{\%} of RNFL measurements. Deviation of the nasal sector from the expected ISNT pattern was a major cause for the ISNT rule not being obeyed for both rim and RNFL assessments. Specifically, 10.9{\%} of subjects had wider nasal rims than the inferior rims, 29.4{\%} had wider nasal rims than the superior rims, 14.7{\%} had narrower nasal rims than the temporal rims, and 42.9{\%} had thinner nasal RNFLs compared to the temporal quadrant. Exclusion of the nasal quadrant from the ISNT rule significantly increased the validity of ISNT variant rules, with 70.9{\%} and 76.4{\%} of disc photographs following the IST rule and the IS rule, respectively. Similarly, for RNFL thickness, 70.9{\%} and 71.8{\%} of patients followed the IST and IS rule, respectively. Conclusions The ISNT rule is only valid for about a third of disc photographs and less than half of RNFL measurements in normal patients. ISNT rule variants, such as the IST and IS rule, may be considered, as they are valid in more than 70{\%} of patients.",
author = "Poon, {Linda Yi Chieh} and {Sol{\'a}-Del Valle}, David and Turalba, {Angela V.} and Falkenstein, {Iryna A.} and Michael Horsley and Kim, {Julie H.} and Song, {Brian J.} and Hana Takusagawa and Kaidi Wang and Chen, {Teresa C.}",
year = "2017",
month = "12",
day = "1",
doi = "10.1016/j.ajo.2017.09.018",
language = "English (US)",
volume = "184",
pages = "19--27",
journal = "American Journal of Ophthalmology",
issn = "0002-9394",
publisher = "Elsevier USA",

}

TY - JOUR

T1 - The ISNT Rule

T2 - How Often Does It Apply to Disc Photographs and Retinal Nerve Fiber Layer Measurements in the Normal Population?

AU - Poon, Linda Yi Chieh

AU - Solá-Del Valle, David

AU - Turalba, Angela V.

AU - Falkenstein, Iryna A.

AU - Horsley, Michael

AU - Kim, Julie H.

AU - Song, Brian J.

AU - Takusagawa, Hana

AU - Wang, Kaidi

AU - Chen, Teresa C.

PY - 2017/12/1

Y1 - 2017/12/1

N2 - Purpose To determine what percentage of normal eyes follow the ISNT rule, and whether ISNT rule variants may be more generalizable to the normal population. Design Cross-sectional study. Methods SETTING: Institutional setting. STUDY POPULATION: Total of 110 normal subjects. OBSERVATION PROCEDURES: Neuroretinal rim assessments from disc photographs and retinal nerve fiber layer (RNFL) thickness measurements from spectral-domain optical coherence tomography. MAIN OUTCOME MEASURES: The percentages of subjects that obeyed the ISNT rule and its variants. Results The ISNT rule is only valid for 37.0% of disc photograph rim assessments and 43.8% of RNFL measurements. Deviation of the nasal sector from the expected ISNT pattern was a major cause for the ISNT rule not being obeyed for both rim and RNFL assessments. Specifically, 10.9% of subjects had wider nasal rims than the inferior rims, 29.4% had wider nasal rims than the superior rims, 14.7% had narrower nasal rims than the temporal rims, and 42.9% had thinner nasal RNFLs compared to the temporal quadrant. Exclusion of the nasal quadrant from the ISNT rule significantly increased the validity of ISNT variant rules, with 70.9% and 76.4% of disc photographs following the IST rule and the IS rule, respectively. Similarly, for RNFL thickness, 70.9% and 71.8% of patients followed the IST and IS rule, respectively. Conclusions The ISNT rule is only valid for about a third of disc photographs and less than half of RNFL measurements in normal patients. ISNT rule variants, such as the IST and IS rule, may be considered, as they are valid in more than 70% of patients.

AB - Purpose To determine what percentage of normal eyes follow the ISNT rule, and whether ISNT rule variants may be more generalizable to the normal population. Design Cross-sectional study. Methods SETTING: Institutional setting. STUDY POPULATION: Total of 110 normal subjects. OBSERVATION PROCEDURES: Neuroretinal rim assessments from disc photographs and retinal nerve fiber layer (RNFL) thickness measurements from spectral-domain optical coherence tomography. MAIN OUTCOME MEASURES: The percentages of subjects that obeyed the ISNT rule and its variants. Results The ISNT rule is only valid for 37.0% of disc photograph rim assessments and 43.8% of RNFL measurements. Deviation of the nasal sector from the expected ISNT pattern was a major cause for the ISNT rule not being obeyed for both rim and RNFL assessments. Specifically, 10.9% of subjects had wider nasal rims than the inferior rims, 29.4% had wider nasal rims than the superior rims, 14.7% had narrower nasal rims than the temporal rims, and 42.9% had thinner nasal RNFLs compared to the temporal quadrant. Exclusion of the nasal quadrant from the ISNT rule significantly increased the validity of ISNT variant rules, with 70.9% and 76.4% of disc photographs following the IST rule and the IS rule, respectively. Similarly, for RNFL thickness, 70.9% and 71.8% of patients followed the IST and IS rule, respectively. Conclusions The ISNT rule is only valid for about a third of disc photographs and less than half of RNFL measurements in normal patients. ISNT rule variants, such as the IST and IS rule, may be considered, as they are valid in more than 70% of patients.

UR - http://www.scopus.com/inward/record.url?scp=85031754622&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85031754622&partnerID=8YFLogxK

U2 - 10.1016/j.ajo.2017.09.018

DO - 10.1016/j.ajo.2017.09.018

M3 - Article

C2 - 28947074

AN - SCOPUS:85031754622

VL - 184

SP - 19

EP - 27

JO - American Journal of Ophthalmology

JF - American Journal of Ophthalmology

SN - 0002-9394

ER -