Comparative analysis of Nasal Step Threshold versus 24-2 Humphrey Field Analyser field testing in diagnosis of glaucoma among glaucoma suspects

TITLE Comparative analysis of Nasal Step Threshold versus 242 Humphrey Field Analyser field testing in diagnosis of glaucoma among glaucoma suspects INTRODUCTION     Glaucoma is a leading cause of irreversible blindness and is projected to affect 278 million individuals in Asia by 2040 with India bearing a disproportionate burden Despite its prevalence over 75 percent of cases remain undiagnosed due to the insidious nature of progression of visual field loss Early detection of glaucomatous damage is thus critical for preventing blindness but the current goldstandard of glaucoma field testing 242 Humphrey Field Analyzer HFA testing could potentially be overlooking some aspects of glaucomatous field defects including some central defects better seen in 102 testing and potentially early nasal step defects a hallmark of glaucoma due to the tests 6degree grid spacing This could be creating a diagnostic gap and thus delaying treatment initiation allowing preventable vision loss to occur     The Nasal Step Threshold Test NSTT is a test setting present on offers targeted evaluation of the nasal field where early glaucomatous defects frequently manifest While 242 HFA provides broad visual field assessment its spatial resolution may miss localized defects detectable through focused threshold testing Recent studies demonstrate that alternative protocols like 102 testing uncover central defects missed by 242 patterns suggesting similar potential for NSTT in nasal field evaluation However no rigorous comparative studies exist to validate NSTTs diagnostic utility against standard protocols     This prospective crosssectional study addresses this critical knowledge gap by comparing NSTT and 242 HFA in 86 glaucoma suspects from a highvolume tertiary center Participants will undergo both tests in randomized order with sensitivityspecificity analysis defect quantification and timeefficiency comparisons serving as primary outcomes The protocol incorporates rigorous quality controls including standardized diagnostic criteria and randomization to mitigate testingorder bias     By establishing NSTTs diagnostic performance characteristics this research could potentially bring to the forefront a testing sequence till now underexplored and in doing so allow earlier glaucoma diagnoses and create a rapid focused testing protocol particularly valuable in resourceconstrained settings where glaucomas iceberg phenomenon remains most pronounced The studys findings may directly inform clinical guidelines potentially reducing preventable blindness through timely intervention  OBJECTIVES     To determine the sensitivity and specificity of Nasal Step Threshold Test in the detection of glaucoma compared to 242 Humphrey Field Analyser HFA testing     To use or formulate parameters to assess and grade the visual field defects picked up by Nasal Step Threshold Test     To compare the relative time taken for both Nasal Step Threshold Test versus 242 HFA testing  METHODOLOGY     This prospective crosssectional study employs a comparative design to evaluate the diagnostic efficacy of Nasal Step Threshold Testing NSTT against the 242 Humphrey Field Analyzer HFA in glaucoma suspects Below is the detailed methodology     Study Design and Rationale The study adopts a prospective crosssectional design to directly compare NSTT and 242 HFA outcomes within the same patient cohort minimizing intersubject variability This design aligns with diagnostic accuracy studies requiring simultaneous evaluation of multiple tests15 Study Population Inclusion Criteria             Age more than 18 years both genders             Glaucoma suspects defined by             Intraocular pressure more than 21 mmHg             Optic disc cupping or neuroretinal rim thinning             Family history of glaucoma  Exclusion Criteria             Unreliable visual field tests more than 33 percent fixation loss more than 15 percent false positives             Ocular comorbidities eg diabetic retinopathy optic neuropathies             History of intraocular surgery except uncomplicated cataract or glaucoma surgery      Sample Size and Selection Sample size was calculated to be 86 participants with a 10 percent dropout rate Data Collection Procedures Testing Protocol The study is set in the Ophthalmology department of Kasturba Hospital KMC Manipal         Participants are recruited from the available patient population at Ophthalmology department of Kasturba Hospital KMC Manipal after obtaining their informed consent          Patients who are diagnosed to be glaucoma suspects by an ophthalmologist would be advised to undergo standard of care comprehensive eye evaluation and glaucoma testing which includes Visual Field Testing Pachymetry and Fundus photography          Those willing to be part of study will be recruited          Informed consent will be taken          As per the standard of care participants will undergo Visual Field Testing via the Humphrey Field Analyser HFA using 242 HFA testing then in the same sitting and on the same machine an additional parameter the Nasal Step Threshold Test NSST will be calculated          BOTH 242 and NSST are settings on the HFA machine for Visual Field Testing They differ in the area of visual field tested The mechanism and procedure of both tests is otherwise similar          The order of testing will be randomised with all even enrolment numbers undergoing 242 HFA testing first while all odd enrolment numbers would give the Nasal Step Threshold Test first          Participants will ONLY have to pay for routine standard of care testing ie total testing cost for a participant of the study will be the EXACT SAME as that of any glaucoma suspect undergoing routine standard of care glaucoma evaluation The additional parameter will NOT be charged to the patient Patients are NOT being called only for the purpose of the study willing patients will be recruited as seen in the OPD          ALL PARTICIPANTS in the study will receive the intervention ie will undergo the additional test          Once the participant has undergone comprehensive eye evaluation and their glaucoma workup is complete as per the standard of care with an additional Nasal Step Threshold Parameter also calculated the results of the testing will be interpreted by the glaucoma consultant  Variables Collected         Sensitivity specificity of NSTT vs 242 HFA         Defect quantification location depth         Test duration minutes  Quality Control             Standardization             All tests conducted by trained technicians using the same HFA device             Exclusion of unreliable tests based on fixation loss falsepositive thresholds  Bias Mitigation         Data Management and Confidentiality         Patient identifiers replaced with anonymized codes         Data stored in passwordprotected databases with restricted access  Statistical Analysis Primary Outcomes         Sensitivity specificity analysis using contingency tables         Agreement between tests assessed via Cohens   Secondary Outcomes         Mean test duration compared via paired ttests         Defect severity analyzed using linear regression  Ethical Considerations     Informed Consent Written consent obtained after explaining risks benefits     Compensation Participants receive fruit juice water to mitigate fatiguerelated attrition     Approvals Institutional Ethics Committee approval secured Justification of Approach     Crosssectional Design Optimal for comparing diagnostic tools without prolonged followup     Randomization Reduces ordereffect bias enhancing internal validity     Power Calculation Ensures adequate sample size to detect clinically meaningful differences     This methodology combines rigorous design standardized protocols and robust statistical planning to address gaps in glaucoma diagnostic practices aligning with funder priorities for translational impact  IMPLICATIONS This studys findings hold significant theoretical and practical implications for glaucoma diagnosis and public health Theoretically validating the Nasal Step Threshold Test NSTT against the 242 HFA will address critical gaps in understanding early glaucomatous nasal field defects refining pathophysiological models of glaucoma progression By quantifying NSTTs sensitivity specificity the results will clarify its role in detecting localized defects missed by broader protocols advancing perimetry research and diagnostic criteria Practically confirming NSTTs efficacy could transform clinical protocols enabling earlier glaucoma detection in highburden regions like India where delayed diagnosis drives preventable blindness A rapid focused testing method would optimize resource utilization in tertiary centers and rural clinics alike addressing the iceberg phenomenon of undiagnosed cases The timeefficiency data may streamline workflows reducing patient fatigue and improving compliance during screenings For policymakers validated NSTT protocols could inform national screening guidelines while device manufacturers might integrate targeted testing algorithms into existing HFA systems By bridging diagnostic disparities this research aligns with global priorities to reduce vision loss offering a scalable model for lowresource settings grappling with glaucomas rising prevalence