Factors Affecting ISNT Rule Satisfaction in Normal and Glaucomatous Eyes

Central retinal vessel trunk exit location: An important factor while evaluating the neuroretinal rim

PURPOSE

Optic nerve head (ONH) evaluation plays a key role in differentiating normal from glaucomatous disk. Thinning of the inferior neuroretinal rim (NRR) has been noted in early glaucoma. However, NRR thickness in different quadrants appears to depend on various factors including central retinal vessel trunk exit (CRVT) position. We evaluated ocular parameters that determined the NRR thickness in the different quadrants of normal eyes.

METHODS

Retrospective review of demographic and ocular data from 773 eyes of 388 subjects with normal ONH over one year was undertaken.

RESULTS

Nearly 54% were males, and the mean age was 43.2 years. The CRVT exit was central in 50% (773). The common site for noncentral CRVT was superotemporal (ST) [37%, 141/384] followed by inferotemporal (IT) [35%, 135/384]. With noncentral CRVT, the probability that the inferior, superior, nasal and temporal (ISNT) rule was not followed was 1.42 times ( P < 0.001). The thinnest rim quadrant (TRQ) was mostly ST (69%) irrespective of CRVT location. The TRQ was IT in 40% when CRVT was noncentral and 82% with IT CRVT exit. With noncentral CRVT, round disks favored noncompliance [132 (54.1%), odds ratio (OR) 2.56] with the ISNT rule. The OR of noncompliance with the ISNT rule increases 1.89 times with inferonasal CRVT and 1.22 times with a unit increase in the axial length.

CONCLUSION

TRQ was IT in IT CRVT, and noncompliance with the ISNT rule was observed with large disks, longer axial length, and noncentral CRVT. This implies that despite the ISNT rule being violated these eyes do not have optic nerve pathology and should not be subjected to unnecessary diagnostic tests.

Radial peripapillary capillary density as a predictive factor for glaucoma in eyes with ocular hypertension. An observational, comparative, single-centred study

Background: Ocular hypertension (OH) is a condition characterized by elevated intraocular pressure (IOP) exceeding the normal range, without any evident damage to the optic nerve or visual field defects characteristic of glaucoma. It constitutes a significant precursor to the development of glaucoma, a leading cause of irreversible vision loss worldwide. Emerging evidence has shown that microcirculation alterations in eyes with OH could serve as predicting factors to identify eyes at high risk for progression to glaucoma. In view of the above, the purpose of our study is to investigate microcirculation alterations of the radial peripapillary capillary plexus using optical coherence tomography angiography (OCT-A) in patients with ocular hypertension (OH). Methods: A total of 192 eyes were included in this observational, comparative, single-centre study and were divided in two groups: OH eyes and healthy controls. OCT-A was performed to analyze microcirculation characteristics at the peripapillary area. Radial peripapillary capillary density was measured at the total area of the optic disc and at each separate region (superior, inferior, inside). The parameters of age, medical treatment for ocular hypertension, sex and retinal fiber layer thickness were evaluated. Results: Total radial peripapillary capillary density was significantly lower in patients with OH than in healthy controls Concerning the microcirculation characteristics at each separate region of the peripapillary area, the results were as follows: inferior radial peripapillary capillary density was significantly decreased in individuals with OH than in controls, while measurements in the superior peripapillary area and internal optic disc were similar in both groups. Conclusions: Our study indicates decreased radial peripapillary capillary density in eyes with OH. Microcirculation alterations in the inferior peripapillary area could potentially comprise biomarkers for OH progression to glaucoma.

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

PURPOSE

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Pupillary response to chromatic light stimuli as a possible biomarker at the early stage of glaucoma: a review

Glaucoma is a multifactorial neurodegenerative disease of the optic nerve currently considered a severe health problem because of its high prevalence, being the primary cause of irreversible blindness worldwide. The most common type corresponds to Primary Open-Angle Glaucoma. Glaucoma produces, among other alterations, a progressive loss of retinal ganglion cells (RGC) and its axons which are the key contributors to generate action potentials that reach the visual cortex to create the visual image. Glaucoma is characterized by Visual Field loss whose main feature is to be painless and therefore makes early detection difficult, causing a late diagnosis and a delayed treatment indication that slows down its progression. Intrinsically photosensitive retinal ganglion cells, which represent a subgroup of RGCs are characterized by their response to short-wave light stimulation close to 480 nm, their non-visual function, and their role in the generation of the pupillary reflex. Currently, the sensitivity of clinical examinations correlates to RGC damage; however, the need for an early damage biomarker is still relevant. It is an urgent task to create new diagnostic approaches to detect an early stage of glaucoma in a prompt, quick, and economical manner. We summarize the pathology of glaucoma and its current clinical detection methods, and we suggest evaluating the pupillary response to chromatic light as a potential biomarker of disease, due to its diagnostic benefit and its cost-effectiveness in clinical practice in order to reduce irreversible damage caused by glaucoma.

The Inferior, Superior, Temporal Rim Width Pattern (IST Rule) Detects Glaucoma in a Japanese Population

PRCIS

The inferior>superior>temporal rim width rate (IST pattern) rather than inferior≥superior≥nasal≥temporal (ISNT) pattern was suited for screening glaucoma in Japanese subjects. Failure of the IST pattern was associated with several important risk factors for glaucoma.

PURPOSE

The purpose of this study was to find a rim width rate pattern to yield the highest positive likelihood ratio (LR+) in detecting glaucoma eyes and to identify risk factors for glaucoma correlating with its failure in a population-based setting.

METHODS

Disc stereophotographs of 2474 eyes of 2474 normal subjects and 237 eyes of 237 glaucoma subjects found in the Kumejima Study were analyzed using computer-assisted planimetry. Among all combinations of the inferior (I), superior (S), nasal (N) and/or temporal (T) rim width rate, a pattern showing the highest LR+ was selected and risk factors for glaucoma correlating with its failure were determined using multiple logistic regression analysis.

RESULTS

The average I, S, N, and T rim widths (SD) were 0.45 (0.10), 0.39 (0.09), 0.47 (0.11), and 0.27 (0.07) mm. Among all combinations, the I>S>T rim width rate pattern (IST pattern) disregarding the N rim width showed the highest LR+ of 2.002 (95% confidence interval, 1.778-2.253). Failure of the IST pattern in normal eyes correlated with a smaller disc area (P<0.001) and disc ovality (P=0.005) and larger β-peripapillary area (P<0.001) and compliance with in glaucoma eyes with a smaller β-PPA area (P=0.027), thicker central corneal thickness (P=0.017), lower intraocular pressure (P=0.019), and higher body mass index (P=0.037).

CONCLUSION

Among all combinations, the I>S>T rim width pattern, the IST pattern, yielded the highest LR+ in detecting glaucoma in Japanese glaucoma eyes and its failure of or compliance with the pattern significantly correlated with several known risk factors for glaucoma.

Correlation Between Central Corneal Thickness and Radial Peripapillary Capillary Density, in Patients With Ocular Hypertension

Purpose

To investigate any possible relationship between the central corneal thickness and the radial peripapillary capillary density detected by optical coherence tomography (OCT) angiography in eyes with ocular hypertension.

Materials and methods

In this observational study, 135 eyes were examined. OCT angiography of the optic disc (4.5 mm) and ultrasound corneal pachymetry were performed in all cases. Age, medical treatment for ocular hypertension, sex, and retinal nerve fiber layer thickness were evaluated. The main indices of blood flow were also examined. Spearman correlation coefficients were used to explore the association between two continuous variables.

Results

A directly proportional significance regarding the correlation between central corneal thickness and radial peripapillary network was indicated in eyes with ocular hypertension (p = .036).

Conclusions

Central corneal thickness and radial peripapillary capillary density constitute two essential screening parameters for patients with ocular hypertension.