Chancellery Research - Research Publications
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ItemThe association between retinal vein pulsation pressure and optic disc haemorrhages in glaucoma(PUBLIC LIBRARY SCIENCE, 2017-07-28)PURPOSE: To explore the potential relationship between optic disc haemorrhage, venous pulsation pressure (VPP), ocular perfusion pressures and visual field change in glaucomatous and glaucoma suspect eyes. MATERIALS AND METHODS: This prospective observational study examined 155 open angle glaucoma or glaucoma suspect eyes from 78 patients over 5 years. Patients were followed with 3 monthly non-mydriatic disc photographs, 6 monthly standard automated perimetry and annual ophthalmodynamometry. The number of disc haemorrhages in each hemidisc was counted across the study period. Visual field rate of change was calculated using linear regression on the sensitivity of each location over time, then averaged for the matching hemifield. VPP and central retinal artery diastolic pressure (CRADP) were calculated from the measured ophthalmodynanometric forces (ODF). The difference between brachial artery diastolic pressure (DiastBP) and CRADP was calculated as an index of possible flow pathology along the carotid and ophthalmic arteries. RESULTS: Mean age of the cohort was 71.9 ± 7.3 Years. 76 out of 155 eyes (49%) followed for a mean period of 64.2 months had at least 1 disc haemorrhage. 62 (81.6%) of these 76 eyes had recurrent haemorrhages, with a mean of 5.94 recurrences over 64.2 months. Using univariate analysis, rate of visual field change (P<0.0001), VPP (P = 0.0069), alternative ocular perfusion pressure (CRADP-VPP, P = 0.0036), carotid resistance index (DiastBP-CRADP, P = 0.0108) and mean brachial blood pressure (P = 0.0203) were significantly associated with the number of disc haemorrhages. Using multivariate analysis, increased baseline visual field sensitivity (P = 0.0243, coefficient = 0.0275) was significantly associated with disc haemorrhage, in conjunction with higher VPP (P = 0.0029, coefficient = 0.0631), higher mean blood pressure (P = 0.0113, coefficient = 0.0190), higher carotid resistance index (P = 0.0172, coefficient = 0.0566), and rate of visual field loss (P<0.0001, coefficient = -2.0695). CONCLUSIONS: Higher VPP was associated with disc haemorrhage and implicates the involvement of venous pathology, but the effect size is small. Additionally, a greater carotid resistance index suggests that flow pathology in the ophthalmic or carotid arteries may be associated with disc haemorrhage.
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ItemOrientation of the Temporal Nerve Fiber Raphe in Healthy and in Glaucomatous Eyes(ASSOC RESEARCH VISION OPHTHALMOLOGY INC, 2017-08)PURPOSE: To determine the normal variation in orientation of the temporal nerve fiber raphe, and the accuracy with which it may be predicted or approximated in lieu of direct measurement. METHODS: We previously described an algorithm for automatic measurement of raphe orientation from optical coherence tomography, using the intensity of vertically oriented macular cubes. Here this method was applied in 49 healthy participants (age 19-81 years) and 51 participants with primary open angle glaucoma (age 51-80 years). RESULTS: Mean fovea-disc-raphe angle was 173.5° ± 3.2° (range = 166°-182°) and 174.2° ± 3.4° (range = 166°-184°) in healthy and glaucoma patients, respectively. Differences between groups were not significant. Fovea-disc-raphe angle was not correlated with age or axial length (P > 0.4), showed some symmetry between eyes in glaucoma (R2 = 0.31, P < 0.001), and little symmetry in the healthy group (P = 0.06). Fovea-disc angle was correlated with fovea-raphe angle (R2 = 0.27, P = 0.0001), but was not a good predictor for raphe orientation (average error = 6.8°). The horizontal axis was a better predictor (average error = 3.2°; maximum error = 9.6°), but still gave approximately twice the error previously reported for direct measurement from macular cubes. CONCLUSIONS: There is substantial natural variation in temporal nerve fiber raphe orientation, which cannot be predicted from age, axial length, relative geometry of the disc and fovea, or the contralateral eye. For applications to which the orientation of the raphe is considered important, it should be measured directly.
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ItemThe Proportion of Individuals Likely to Benefit from Customized Optic Nerve Head Structure-Function Mapping(ELSEVIER SCIENCE INC, 2017-04)PURPOSE: Interindividual variance in optic nerve head (ONH) position, axial length, and location of the temporal raphe suggest that customizing mapping between visual field locations and ONH sectors for individuals may be clinically useful. Herein we quantify the proportion of the population predicted to have structure-function mappings that markedly deviate from "average," and thus would benefit from customized mapping. DESIGN: Database study and case report. PARTICIPANTS: Population database of 2836 eyes from the Beijing Eye Study and a single case report of an individual with primary open-angle glaucoma. METHODS: Using the morphometric fundus data of the Beijing Eye Study for 2836 eyes and applying a recently developed model based on axial length and ONH position relative to the fovea, we determined for each measurement location in the 24-2 Humphrey (Carl Zeiss Meditec, Dublin, CA) visual field the proportion of eyes for which, in the customized approach as compared with the generalized approach, the mapped ONH sector was shifted into a different sector. We determined the proportion of eyes for which the mapped ONH location was shifted by more than 15°, 30°, or 60°. MAIN OUTCOME MEASURES: Mapping correspondence between locations in visual field space to localized sectors on the ONH. RESULTS: The largest interindividual differences in mapping are in the nasal step region, where the same visual field location can map to either the superior or inferior ONH, depending on other anatomic features. For these visual field locations, approximately 12% of eyes showed a mapping opposite to conventional expectations. CONCLUSIONS: Anatomically customized mapping shifts the map markedly in approximately 12% of the general population in the nasal step region, where visual field locations can map to the opposite pole of the ONH than conventionally considered. Early glaucomatous damage commonly affects this region; hence, individually matching structure to function may prove clinically useful for the diagnosis and monitoring of progression within individuals.