ISNT Rule in Normal Population

October 8, 2022 updated by: Amr Mohamed Sayed, Assiut University

Is the ISNT Rule Still a Rule : a Study to Determine Prevalence of the ISNT Rule and Its Variants in the Normal Population

This study sought to determine the percentage of normal eyes that followed the ISNT rule by retinal nerve fiber layer (RNFL) and neuroretinal rim thickness measurements using optical coherence tomography (OCT) , and secondarily, whether alternative rules may be more applicable or easily generalized.

Study Overview

Status

Not yet recruiting

Conditions

Intervention / Treatment

Detailed Description

Glaucoma is a disease of the optic nerve, which results in structural optic nerve head (ONH) damage and functional visual field (VF) loss. It has increased as a cause of global blindness from 4.4% in 1990 to 6.3% in 2010. Its global prevalence is also increasing from 3.54% or 64.3 million people in 2013 to a projected 111.8 million people by 2040. Detection of structural ONH damage is critical for early diagnosis, because ONH changes usually precede VF loss. Two cornerstone elements of the ONH and peripapillary examination are stereo disc photography and optical coherence tomography (OCT) retinal nerve fiber layer (RNFL) thickness measurements. By analyzing the neuroretinal rim in disc photos of normal subjects, Jonas et al found that the rim width typically exhibited a specific pattern of the inferior (I) rim being the widest, followed by the superior (S) rim, then the nasal (N) rim, and then the temporal (T) rim being the thinnest. This specific neuroretinal rim pattern was later coined by Elliot Werner as the "ISNT rule." Because neuroretinal rim loss is a hallmark feature of glaucoma, patients who deviate from the ISNT rule may need to be watched more closely for glaucoma. The RNFL, on the other hand, has also been shown in histological studies in normal, non-glaucomatous eyes to exhibit a similar pattern of the inferior quadrant being the thickest, followed by the superior, nasal, then temporal quadrant. Since RNFL thinning, particularly in the superior and inferior quadrants, is also a characteristic structural change in glaucoma, deviation from the ISNT rule for RNFL thickness may also be an early indicator of glaucomatous structural change. Therefore, many investigators have sought to determine whether the ISNT rule, either applied to the neuroretinal rim disc photos or to RNFL thickness measurements, is useful in the diagnosis of glaucoma or not. However, the optic disc photo ISNT rule studies are conflicting, with some finding the ISNT rule and its variants clinically useful, while others have not. In contrast, RNFL ISNT rule studies based on OCT findings are in uniform agreement, stating that the ISNT rule and its variants were not helpful in the diagnosis of glaucoma. Some have hypothesized that the ISNT rule is not easily generalizable to the individual, because the initial studies were derived from mean values. Therefore, some of the limitations of the ISNT rule may stem from the fact that it is unclear what percentage of individual normal eyes follow the ISNT rule. Other limitations may arise from the fact that perhaps other rules may be more common in the normal population.

Study Type

Observational

Enrollment (Anticipated)

116

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

16 years to 78 years (Adult, Older Adult)

Accepts Healthy Volunteers

N/A

Genders Eligible for Study

All

Sampling Method

Non-Probability Sample

Study Population

Normal population

Description

Inclusion Criteria:

  • a normal eye examination without ocular diseases except for cataracts
  • best corrected vision of > 6/12
  • a normal VF test result defined by a pattern standard deviation value of > 5% compared to age matched controls in the perimeter's normative database and a glaucoma hemifield test within normal limits
  • a spherical equivalent of between -5 and +5 diopters.

Exclusion Criteria:

  • unreliable VF testing with > 33% fixation losses, > 20% false positives, or > 20% false negatives.
  • any history of ocular hypertension or intraocular pressures > 21mmHg at the time of the visit;
  • inter-eye cup-to-disc ratio (CDR) asymmetry of > 0.2;CDR of > 0.4
  • history of a neurologic disease or systemic medication that could produce VF defects.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Observational Models: Cohort
  • Time Perspectives: Cross-Sectional

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
ISNT rule prevalence in normal population
Time Frame: Baseline
the percentage of normal eyes that followed the ISNT rule by retinal nerve fiber layer and neuroretinal rim thickness measurements using (OCT)
Baseline

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
variants of ISNT rule
Time Frame: Baseline
whether alternative rules may be more applicable or easily generalized than the ISNT rule like IS,IST, TSINT rule .
Baseline

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Assiut University

Investigators

  • Study Director: Abd-Elnasser A Mohamed, PhD, Assiut University

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Anticipated)

December 1, 2022

Primary Completion (Anticipated)

December 30, 2023

Study Completion (Anticipated)

December 30, 2023

Study Registration Dates

First Submitted

October 9, 2021

First Submitted That Met QC Criteria

October 8, 2022

First Posted (Actual)

October 12, 2022

Study Record Updates

Last Update Posted (Actual)

October 12, 2022

Last Update Submitted That Met QC Criteria

October 8, 2022

Last Verified

October 1, 2022

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • ISNT rule

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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