ISNT Rule Research Articles

Use of brimonidine tartrate eye drops after nonarteritic anterior ischemic optic neuropathy event: Case series

Abstract Purpose: The purpose of the study was to evaluate the response of retinal nerve fiber layer thickness to brimonidine tartrate (0.15%) eye drops after a nonarteritic anterior ischemic optic neuropathy (AION) event. Methods: Series of cases with retrospective data collection of medical records and optical coherence tomography (OCT) examinations to evaluate retinal nerve fiber layer from 63 eyes of 36 patients with nonarteritic AION. The patients were collected according to the clinical criteria from the ophthalmology service of a major hospital. Healthy subjects were recruited from the general clinic and hospital staff. Patients were randomized into three groups: Group 1: patients using brimonidine tartrate (0.15%) eye drops, Group 2: patients without using eye drops, and Group 3: control group. Results: The group without medication had a statistically significant loss of lower nerve fiber layer (P = 0.025) and in the mean OCT (P = 0.035); however, in the other quadrants, the thickness reduction was not statistically significant. They showed a pattern of greater loss in the upper portion (P = 0.065), followed by the lower (P = 0.025), temporal (P = 0.051), and nasal (P = 0.07) portions, but the ISNT rule was preserved. Conclusion: The present study demonstrated that the nonuse of brimonidine tartrate led to a statistically significant loss of the lower nerve fibers layer and in the mean OCT.

Comparison of different measuring methods in the assessment of the ISNT rule and its variants in a normal population: A cross-sectional study.

The aim of this study was to compare five different neuroretinal rim (NRR) measurement methods, based on quadrants and NRR widths, in the assessment of the ISNT (inferior (I) > superior (S) > nasal (N) > temporal (T)) rule, and its variants IST (inferior (I) > superior (S) > temporal (S)) rule, IS (inferior (I) > superior (S)) rule and T (temporal is the thinnest) rule in a normal population. Factors influencing compliance with this rule and its variants were also evaluated. Stereoscopic fundus images were analysed through a dichoptic viewing system. Two graders labelled the optic disc and cup, as well as the fovea. Custom-made software automatically determined the limits of the optic disc and cup and examined the ISNT rule and its variants using several NRR measurement methods. Sixty-nine subjects with normal eyes were enrolled. For the various NRR measuring methods, the percentage of eyes following the rules, that is, validity ranges were 0.0%-15.9% for the ISNT rule, 31.9%-59.4% for the IST rule, 46.4%-59.4% for the IS rule and 50.7%-100.0% for the T rule. Significant intra-measurement agreement ranges were IST (κ = 0.50-0.85), IS (κ = 0.68-1.00) and T (κ = 0.24-0.77). Only the IST and IS rules achieved significant inter-measurement agreement (κ = 0.47-1.00). After multivariate and receiver operating characteristic (ROC) curve analyses, the vertical cup position cupy (area under the ROC curve (AUROC) = 0.60-0.96; cut-off = |0.005|) was the most important predictor for virtually all NRR measurement agreements for the ISNT, IST and IS rules. The horizontal cup position (AUROC = 0.50-0.92; cut-off = -0.028 to 0.05) was the most important predictive factor for the majority of the NRR measurement agreements for the T rule. Only the IST and IS rules are valid for the same normal subjects. The most important factor affecting the validity of the ISNT rule and its variants was the anatomical cup position. NRR measurement agreements based on NRR quadrants exhibited larger validity and better agreement. The IST and IS rules can be combined with the alternative SIT (superior (S) > inferior (I) > temporal (T)) and SI (superior (S) > inferior (I)) rules to detect almost all normal subjects.

Screening fundus photography predicts and reveals risk factors for glaucoma conversion in eyes with large optic disc cupping

This study aimed to investigate the risk factors for glaucoma conversion and progression in eyes with large optic disc cupping without retinal nerve fiber layer defect (RNFLD). Five hundred forty-two eyes of 271 subjects who had a vertical cup-to-disc ratio (CDR) ≥ 0.6 without RNFLD were enrolled. Characteristics for optic disc configuration (including CDR, vertical cupping, ISNT rule, disc ovality, peripapillary atrophy [PPA]-to-disc area [DA] ratio, and lamina cribrosa pore visibility) and blood vessels (including central retinal vessel trunk [CRVT] nasalization, bayoneting of vessels, baring of circumlinear vessels, history of disc hemorrhage [DH] and vessel narrowing/sclerotic change) were evaluated. From a median follow-up of 11.3 years, 26.6% of eyes (n = 144) developed RNFLD within a median of 5.1 years. Baseline factors, including vertical CDR ≥ 0.7 (hazard ratio [HR] = 2.12), vertical cupping (HR = 1.93), ISNT rule violation (HR = 2.84), disc ovality ≥ 1.2 (HR = 1.61), PPA-to-DA ratio ≥ 0.4 (HR = 1.77), CRVT nasalization ≥ 60% (HR = 1.77), vessel narrowing/sclerotic change (HR = 2.13), DH history (HR = 5.60), and baseline intraocular pressure ≥ 14 mmHg (HR = 1.70) were significantly associated with glaucoma conversion (all Ps < 0.05). An HR-matched scoring system based on initial fundus photography predicted glaucoma conversion with specificity of 90.4%. Careful examination of the optic nerve head and vascular structures can help to predict the risk of glaucoma conversion in eyes with large optic disc cupping.

SD-OCT guided analysis of retinal nerve fibre layer in ammetropes in central India

The retinal nerve fibre layer is a most crucial indicator of optic nerve damage in glaucoma as it advances visual field loss. Thickness of the RNFL can be measured using high resolution OCT. We conducted this study to evaluate the alterations in retinal nerve fibre layer thickness measured by SD- OCT in ametropes and to find various factors affecting RNFL thickness.: Study of retinal nerve fibre layer thickness (RNFL) by Optical Coherence Tomography (OCT) in ametropes in tertiary care hospital of central India.Hospital based prospective observational study included 300 eyes of 150 participants. Visiting ophthalmology outpatient department Gandhi medical college and fulfilling the inclusion and exclusion criteria.: Patients were divided into five groups of 60 eyes each on the basis of refractive status of eyes into emetropia, low hypermetropia, moderate hypermetropia, low mypopia and moderate mypopia. Subjects were subjected to OCT scan and RNFL thickness was measured. All groups were evaluated and observations were noted and results were analysed. To find the association between degree of ametropia and RNFL thickness one way ANOVA test was used. Correlation between axial length and RNFL was assesed by pearson correlation coefficient. p value &amp;#60;0.05 was considered as significant.: RNFL thickness in different groups followed ISNT rule with inferior quadrant showing the greatest thickness followed by the superior, nasal and temporal quadrants. The average RNFL thickness in emmetropics, Low hyperopic, Moderate hyperopic, Low myopic, Moderate myopic was 111.90μm, 110.58 μm, 114.59 μm, 103.33 μm, 93.33 μm respectively, wheras average axial length was 23.85mm, 22.36mm, 21.33mm, 24.72mm, 25.63mm.: With the help of OCT, we can differentiate the changes in RNFL thickness in various refractive errors. So, the refractive status of the eye should be kept in mind before making any ocular diagnosis in which the RNFL is a diagnostic criteria.

Use of the ISNT rule for optic disc evaluation in 40 to 79 year old patients seen in optometric practice

The purpose this study was to investigate the association between intraocular pressure (IOP) and the outcome of ISNT rule assessment of the optic disc in healthy patients seen in mainstream optometric practice. Consecutive patients over the age of 40 years and with no known general- or ocular pathology were enrolled from 4 optometric practices in Norway and Sweden during a period of 9 months. The sample was stratified by age group (40-49, 50-59, 60-69 and 70-79 years) and ISNT rule outcome (obeyed or broken). Subjects underwent a full optometric examination including stereoscopic assessment of the optic disc with the use of the ISNT rule, followed by measurements of intraocular pressure (IOP), central corneal thickness (CCT) and vertical size of the optic disc. Odds ratio (OR) was used to assess the association between IOP and the outcome measure. Stratified and multivariable analyses were employed to investigate the effect of age, gender, CCT, refractive error and disc size on the association. IOP was dichotomized at a cut-off corresponding to the 75th percentile (18 mmHg), whereas numeric covariables were categorized at cut-offs corresponding to the 33rd (ONH 1.6 mm, CCT 545 μm) and 66th percentile (ONH 1.8 mm, CCT 571 μm), respectively. A total of 177 patients (F: 57%, age range 40-79 years) were included. IOP was significantly higher in patients with broken ISNT rule (16.6 vs. 15.5 mmHg, p = 0.046), corresponding to a crude OR of 2.0 (CI 0.95-4.24). In stratified and multivariable analyses the association between IOP and outcome of the ISNT rule was strengthened in males (OR 4.8) and in subjects with small discs (OR 2.2), however only the effect modification by gender reached significance. Further research is necessary to understand the possible implications of these findings on the assessment of optic discs with the use of the ISNT rule.

Optic disc morphology in preterm children. Influence of gestational age and birth weight

The characteristics of the optic disc and the development of the optic nerve can affect visual function in children. The purpose of our study was to assess optic disc morphology in preterm infants and to determine whether it is influenced by gestational age, birth weight and the presence of a retinopathy of prematurity. In a retrospective study, RetCam fundus images of 109 premature newborns admitted to our tertiary-level neonatal intensive care unit were reviewed. We evaluated the cup to disc ratio (C/D), optic disc diameter, cup diameter, shape of the optic disc, adherence to the ISNT rule, and presence of a peripapillary atrophy. Of 218 photos, we found the following results: mean±SD gestational age 28.5±2.7 weeks, mean±SD birth weight 1122±394g, mean C/D 0.32. There was no significant correlation between C/D and gestational age or birth weight. Vertical disc diameter was greater than horizontal disc diameter, with a mean ratio (horizontal/vertical) of 4/5, lending an oval shape to the optic disc. Nineteen infants had retinopathy of prematurity in both eyes; ninety-three percent had peripapillary atrophy. In our study, optic disc morphology in premature newborns was not influenced by gestational age, birth weight or presence of premature retinopathy.

Automatic glaucoma screening using optic nerve head measurements and random forest classifier on fundus images.

Glaucoma is an optic neuropathy that gradually steals the patient's sight by damaging the optic nerve head (which is responsible for transferring images from the eye to the brain). Causing an estimated 12.3% of global blindness, glaucoma is considered as the first leading cause of irreversible blindness in the world. This paper presents a novel eye fundus image analysis algorithm for the automatic measurement of fundus related glaucoma indicators; Cup to Disc Ratio (CDR), verification of the ISNT rule, Disc Damage Likelihood Scale (DDLS), and the classification of the input fundus into glaucoma or non-glaucoma case using a random forest model. The proposed method is applied on the public image database 'HRF', and a local database containing both, normal and glaucoma cases, and resulted sensitivity, specificity, and accuracy of 1, 0.93 and 0.97 respectively. This technique presented the highest classification accuracy compared to previous works studied in the state of the art; hence, it can be used as a computer aided glaucoma diagnosis system by ophthalmologists to assist in their screening routine.

Normative data for optical coherence tomography in children: a systematic review.

The purpose of this study is to systematically review the reported data of normal optical coherence tomography (OCT) results in the paediatric population. A systematic literature search was performed using the PubMed, Embase, and Web of Science databases, using the keywords "optical coherence tomography"; "normative data" or "healthy eyes"; "children" or "paediatric population". Studies with at least 50 participants were included, irrespective of the OCT equipment employed. We excluded the OCT angiography studies or the studies investigating the choroidal thickness. Seventy-four studies were included in the final analysis and information on study design, number of participants, demographic characteristics, type of OCT equipment, OCT parameters and results was collected. Due to the high variability of OCT instruments and parameters used, a meta-analysis was not feasible. We report the normative values for the peripapillary retinal nerve fibre layer thickness and the macular retinal thickness for each ETDRS quadrant, as provided by the studies included in the present analysis. We also report the influence of ethnicity, age, gender, eye laterality, ISNT rule, spherical equivalent, and axial length on OCT results.

Applicability of ISNT Rule Using Bruch&amp;apos;s Membrane Opening-based Optic Nerve Head Parameters

ëª©ì  ì •ìƒì•ˆê³¼ ë ¹ë‚´ìž¥ì•ˆì„ 구별하기 위해 브루크막 개방(Bruch’s membrane opening, BMO) 기반 ì‹œì‹ ê²½ìœ ë‘ 지표들을 이용한 ISNT 규칙의 ì ìš©ì„±ì„ ì•Œì•„ë³´ê³ ìž 한다. 대상과 방법 ì •ìƒì•ˆ 41안과 ê°œë°©ê°ë ¹ë‚´ìž¥ 62안의 의무기록을 í›„í–¥ì ìœ¼ë¡œ 분석하였다. ì‹œì‹ ê²½ 사진에서 ì¸¡ì •í•œ ì‹œì‹ ê²½í Œë‘ê»˜, Bruch’s membrane opening-minimum rim width (BMO-MRW), BMO-MRW average, Bruch’s membrane opening-minimum rim area (BMO-MRA)의 4가지 지표에서 ì‹œì‹ ê²½ì˜ 상측, 하측, 비측, 이측에 해당하는 값을 분석하였다. ì •ìƒì•ˆê³¼ ë ¹ë‚´ìž¥ì•ˆì—ì„œ 각각의 지표를 이용한 ISNT 규칙의 부합 여부를 ì¡°ì‚¬í•˜ê³ ë¯¼ê°ë„ì™€ 특이도를 비교하였다. ê²°ê³¼ ì •ìƒì•ˆê³¼ ë ¹ë‚´ìž¥ì•ˆì—ì„œ 각각 ì‹œì‹ ê²½ 사진에서 ì¸¡ì •í•œ ì‹œì‹ ê²½í Œë‘ê»˜, BMO-MRW, BMO-MRW average를 비교하였을 때 상측, 하측, 이측, 비측 모두 ì‹œì‹ ê²½ 사진에서 ì¸¡ì •í•œ ì‹œì‹ ê²½í Œë‘ê»˜ê°€ 가장 컸다(p<0.001). 네 가지 지표를 이용한 ISNT 규칙의 부합 여부를 비교한 ê²°ê³¼ 민감도는 ì‹œì‹ ê²½ 사진보다 BMO-MRW average와 BMO-MRA가 ìœ ì˜í•˜ê²Œ 높았다(각각 82.3% vs. 98.4%, p<0.05; 82.3% vs. 95.2%, p<0.05). 특이도는 4가지 지표 사이에 ìœ ì˜í•œ 차이가 없었다. ê²°ë¡ ê¸°ì¡´ì˜ ì‹œì‹ ê²½ 사진을 이용한 ISNT 규칙에 비해 BMO 기반 ì‹œì‹ ê²½ìœ ë‘ 지표들을 이용한 ISNT 규칙은 ì •ìƒì•ˆê³¼ ë ¹ë‚´ìž¥ì•ˆ 감별에 더 높은 ì§„ë‹¨ë ¥ì„ 보였다. Keywords: Bruch’s membrane opening-minimum rim area, Diagnostic ability, ISNT rule, Glaucoma optic disc

Agreement in retinal nerve fiber layer values and comparison in children using two optical coherence tomography devices

Abstract Objective To assess absolute agreement and differences in peripapillary retinal nerve fiber layer (pRNFL) values according to sex, age, laterality, origin and optical coherence tomography (OCT) type in normal pediatric patients undergoing OCT scans using both Cirrus and Spectralis. Material and methods Prospective, cross-sectional, and comparative study. We used Spectralis OCT and Cirrus OCT to measure optic disc values of both eyes in one hundred pediatric patients (age 5–15 years), with no previous ocular pathology or systemic disease that could affect the eye. Due to the similarity between eyes, only right eyes were considered (n = 100). Results The average peripapillary retinal nerve fiber layer (pRNFL) values were 99.6 μm with Cirrus and 106.7 μm with the Spectralis system. The four quadrants followed the ISNT rule (inferior-superior-nasal-temporal). The average pRNFL measures correlated negatively with the AL (P 0.05) and there were also no statistical differences in the pRNFL according to age or laterality (P > 0.05). All RNFL values were significantly different between both types of OCTs (P Conclusions We suggest that the respective peripapillary RNFL values obtained using these two OCTs should not be considered interchangeable in pediatric patients.

Grado de concordancia y diferencias entre los valores de capa de fibras nerviosas de la retina peripapilar en niños mediante dos tipos de tomografía de coherencia óptica espectral

ObjectiveTo assess absolute agreement and differences in peripapillary retinal nerve fiber layer (pRNFL) values according to sex, age, laterality, origin and optical coherence tomography (OCT) type in normal pediatric patients undergoing OCT scans using both Cirrus and Spectralis. Material and methodsProspective, cross-sectional, and comparative study. We used Spectralis OCT and Cirrus OCT to measure optic disc values of both eyes in one hundred pediatric patients (age 5 to 15years), with no previous ocular pathology or systemic disease that could affect the eye. Due to the similarity between eyes, only right eyes were considered (n=100). ResultsThe average peripapillary retinal nerve fiber layer (pRNFL) values were 99.6μm with Cirrus and 106.7μm with the Spectralis system. The four quadrants followed the ISNT rule (inferior-superior-nasal-temporal). The average pRNFL measures correlated negatively with the AL (P<.01) in both OCTs, and the degree of agreement between OCTs for pRNFL and inferior RNFL was moderate (CCI: 0.67 and 0.61, respectively), and low in the rest of the sectors. The average pRNFL values of both OCTs were higher in women than in men (P>.05) and there were also no statistical differences in the pRNFL according to age or laterality (P>.05). All RNFL values were significantly different between both types of OCTs (P<.05) and average pRNFL values were significantly thicker (P<.05) in Latin American than in European children in both eyes. ConclusionsWe suggest that the respective peripapillary RNFL values obtained using these two OCTs should not be considered interchangeable in pediatric patients.

Accuracy of the ISNT rule and its variants for differentiating glaucomatous from normal eyes in a population-based study

AimsTo evaluate the accuracy of the ISNT rule (I=inferior, S=superior, N=nasal, T=temporal) and its variants with neuroretinal rim width and retinal nerve fibre layer (RNFL) thickness measurements differentiating normal from...

Geometry of the Retinal Nerve Fibers From Emmetropia Through to High Myopia at Both the Temporal Raphe and Optic Nerve.

The geometry of retinal nerve fibers may be altered with myopia, a known risk factor for glaucoma. Recent developments in high resolution imaging have enabled direct visualization of nerve fiber bundles at the temporal raphe with clinical hardware, providing evidence that this area is sensitive to glaucomatous damage. Here, we test the hypothesis that nerve fiber geometry is altered by myopia, both at the temporal raphe and surrounding the optic nerve head. Seventy-eight healthy individuals participated, with refractive errors distributed between emmetropia and high myopia (+0 to -13 DS). Custom high-density OCT scans were used to visualize RFNL bundle trajectory at the temporal raphe. A standard clinical OCT protocol was used to assess papillary minimum rim width (MRW) and peripapillary retinal nerve fiber layer (RNFL) thickness. Measures of raphe shape-including position, orientation, and width-did not depend significantly on axial length. In 7.5% of subjects, the raphe was rotated sufficiently that inversion of structure-function mapping to visual field space is predicted in the nasal step region. Low concordance to ISNT and related rules was observed in myopia (e.g., for RNFL, 8% of high axial myopes compared with 67% of emmetropes). Greater robustness to refractive error was observed for the IT rule. High density OCT scans enabled visualization of marked interindividual variation in temporal raphe geometry; however, these variations were not well predicted by degree of myopia as represented by axial length. That said, degree of myopia was associated with abnormal thickness profiles for the papillary and peripapillary nerve fiber layer.

ISNT rule satisfaction in Korean non-glaucomatous subjects.

To evaluate the efficacy of the ISNT rule in normal eyes of Koreans. We retrospectively reviewed medical records of 890 subjects with fundus photographs and evaluated the presence of the cup and ISNT rule satisfaction. If the ISNT rule was violated, the quadrants in which the neuroretinal rim was thinnest and thickest, respectively, were evaluated. Among 890 eyes, 84.7% showed the cup. The subjects without the cup were significantly younger and more hyperopic. Among 754 eyes with the cup, 53.5% showed ISNT rule satisfaction. In 351 eyes violating the ISNT rule, the most common quadrant showing the thickest neuroretinal rim was the inferior (65.5%), and the thinnest, the temporal (98.3%). The cup was absent in 15% of the assessed eyes. Only about half of eyes with the cup showed ISNT rule satisfaction. Even in eyes violating ISNT rule, the inferior was the most common quadrant with the thickest neuroretinal rim and the temporal, the thinnest.

Computer-Aided Glaucoma Diagnosis Using Stochastic Watershed Transformation on Single Fundus Images

Glaucoma is a chronic eye disease and one of the major causes of permanent blindness. Since it does not show initial symptoms, early diagnosis is important to limit its progression. This paper presents an automatic optic nerve characterization algorithm for glaucoma diagnosis based only on retinal fundus images. For optic cup segmentation, we used a new method based on the stochastic watershed transformation applied on the YIQ colour space to extract clinical indicators such as the Cup/Disc ratio, the area Cup/Disc ratio and the ISNT rule. Afterwards, an assessment between normal and glaucomatous fundus images is performed. The proposed algorithm was evaluated on 6 different (private and public) databases containing 723 images (377 normal and 346 glaucomatous images) which achieved a specificity and sensitivity of 0.674 and 0.675, respectively. Moreover, an F-score of 0.770 was obtained when evaluating this method on the publicly available database Drishti-GS1. A comparison of the proposed work with other state-of-the-art methods demonstrates the robustness of the proposed algorithm; because it was tested using images from different databases with high variability, which is a common issue in this area. Additional comparisons with existing works for cup segmentation, that use the publicly available database Drishti-GS1, are also presented in this paper.

Predictive Diagnosis of Glaucoma Based on Analysis of Focal Notching along the Neuro-Retinal Rim Using Machine Learning

Automatic evaluation of the retinal fundus image is regarded as one of the most important future tools for early detection and treatment of progressive eye diseases like glaucoma. Glaucoma leads to progressive degeneration of vision which is characterized by shape deformation of the optic cup associated with focal notching, wherein the degeneration of the blood vessels results in the formation of a notch along the neuroretinal rim. In this study, we have developed a methodology for automated prediction of glaucoma based on feature analysis of the focal notching along the neuroretinal rim and cup to disc ratio values. This procedure has three phases: the first phase segments the optic disc and cup by suppressing the blood vessels with dynamic thresholding; the second phase computes the neuroretinal rim width to detect the presence and direction of notching by the conventional ISNT rule apart from calculating the cup-to-disc ratio from the color fundus image (CFI); the third phase uses linear support vector based machine learning algorithm by integrating extracted parameters as features for classification of CFIs into glaucomatous or normal. The algorithm outputs have been evaluated on a freely available database of 101 images, each marked with decision of five glaucoma expert ophthalmologists, thereby returning an accuracy rate of 87.128%.

Pediatric Normative Database of Retinal, Macular and Choroidal Values obtained with Spectral-Domain Optical Coherence Tomography

Purpose: To establish normative values in a Portuguese pediatric population for retinal nerve fiber layer (RNFL), macular, macular ganglion cell-inner plexiform layer (GCIPL) and subfoveal choroidal (SFC) thicknesses Methods: This cross-sectional study enrolled children, 4 to 17 years old, attending the Ophthalmology Department of Hospital de Braga. All subjects underwent comprehensive ophthalmologic examination and were scanned with Cirrus Spectral-Domain Optical Coherence Tomography (SD-OCT). Results: A total of 348 children (9.85±3.49 years) were included. Average RNFL thickness was 97.45±9.78µm and the distribution of RNFL thickness was in agreement with the ISNT rule. Average RNFL thickness showed a positive significant relationship with optic disc (OD) area (p=0.007). A significant positive relationship was also found for OD area (p=0.001 and p=0.04, respectively) and spherical equivalent (SE) (p=0.008 and p=0.004, respectively), in the inferior and nasal quadrants. Average macular thickness was 282.22±11.91µm. Central subfield was the thinnest region, followed by the external ring, while the internal ring was the thickest (p<0.001). Age, SE and gender were the strongest predictors of macular thickness. A negative association was found between the superior external macular thickness and age (p=0.009). A lower thickness in the outer macular region was associated with higher myopic refractive error (p<0.05). Boys had on average a thicker macula (p<0.05). Average GCIPL thickness was 84.97±4.78 µm and average SFC thickness was 374.76±42.51 µm. Conclusion: This study established a SD-OCT normative database for healthy Portuguese children aged 4 to 17 years old, which could improve diagnosis and management of pediatric ophthalmic disorders in children.

Automated Framework for Screening of Glaucoma Through Cloud Computing.

In recent times, the use of computer aided diagnosis for detection of Glaucoma from fundus images has been prevalent. In the proposed work, a cloud based system is proposed for automatic and real-time screening of Glaucoma with the use of automatic image processing techniques. The proposed system offers scalability to the developers and easy accessibility to the consumers. The proposed system is device and location independent. The input digital image is analyzed and a comprehensive diagnostic report is generated consisting of detailed analysis of indicative medical parameters like optic-cup-to-disc ratio, optic neuro-retinal rim, ISNT rules making the report informative and clinically significant. With recent advances in the field of communication technologies, the internet facilities are available that make the proposed system an efficient and economical method for initial screening and offer preventive and diagnostic steps in early disease intervention and management. The proposed system can perform an initial screening test in an average time of 6s on high resolution fundus images. The proposed system has been tested on a fundus database and an average sensitivity of 93.7% has been achieved for Glaucoma cases. In places where there is scarcity of trained ophthalmologists and lack of awareness of such diseases, the cloud based system can be used as an effective diagnostic assistive tool.

Applicability of ISNT Rule Using BMO-MRW to Differentiate Between Healthy and Glaucomatous Eyes.

We evaluated the applicability of the ISNT rule using Bruch's membrane opening minimum rim width (BMO-MRW) in healthy eyes and eyes with normal tension glaucoma (NTG). In total, 124 healthy eyes and 136 NTG eyes were analyzed. Using 2-dimensional disc photographs, neuroretinal rim (NRR) thickness was measured at the superior, inferior, nasal, and temporal sides of the optic disc. Using spectral domain-optical coherence tomography, BMO-MRW was measured at the same regions. We compared the applicability of the ISNT rule in healthy and NTG eyes between these 2 methods. If the NRR was not clearly distinguished on disc photographs, the eye was classified into the "indistinguishable NRR" group and we only tested applicability of the ISNT rule using BMO-MRW. The specificity of "violation of the ISNT rule" for the diagnosis of glaucoma was higher when BMO-MRW was used (66.3%) than using disc photographs (42.2%), whereas the sensitivity did not show a significant difference between the 2 methods (91.7% vs. 86.5%). Compared with eyes with distinguishable NRR (179 eyes), eyes with indistinguishable NRR (81 eyes) had higher axial length, more negative refractive error, and higher tilt ratio (P<0.001). The diagnostic ability of "violation of ISNT rule" using BMO-MRW was not significantly different between eyes with indistinguishable NRR and those with distinguishable NRR (P>0.05). Application of the ISNT rule using BMO-MRW shows superiority in distinguishing between healthy and glaucomatous optic discs compared with disc photographs. The ISNT rule can be applied using BMO-MRW even when NRR is indistinguishable on disc photographs, such as in myopic tilted discs.

Factors Affecting ISNT Rule Satisfaction in Normal and Glaucomatous Eyes.

PurposeTo determine the factors that influence the satisfaction of the ‘ISNT rule’ (neural rim width: inferior ≥ superior ≥ nasal ≥ temporal) in normal and glaucomatous eyes.MethodsThe medical records of patients that visited Boramae Medical Center, Seoul, Korea, were reviewed. Each group of normal and glaucomatous eyes was divided into subgroups based on whether or not they satisfied the ISNT rule. ISNT rule assessment was performed by measuring the rim width with stereoscopic optic disc photographs using ImageJ software. Logistic regression analysis was performed to determine the factors that affect ISNT rule satisfaction.ResultsSeventy-seven normal eyes and 97 glaucomatous eyes were included in the study. The ISNT rule was intact in 59 (76.6%) of the normal eyes and was violated in 71 (73.2%) of the glaucomatous eyes. Logistic regression analysis revealed a significant influence of axial length in violation of the ISNT rule in the normal eye group, while the mean deviation value was a significant factor for violation of the ISNT rule in the glaucomatous eye group.ConclusionsThe ISNT rule should be cautiously applied when evaluating normal eyes with long axial lengths. In addition, the ISNT rule might not be as effective for detecting early glaucoma.