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Biomedical subjects

R A Hitchings

Publications and source records attributed to R A Hitchings.

At least 19 recordsLinked to original sources
PubMed2001

The ability of the GDx nerve fibre analyser neural network to diagnose glaucoma.

PURPOSE: To evaluate the neural network used by the GDx in a group of normal subjects, patients with ocular hypertension (OHT) and patients with normal-pressure glaucoma (NPG). METHODS: The GDx neural network produces a "number" that indicates the likelihood that glaucoma is present. This number was compared in three groups representing different stages of health and disease, namely, normal controls (n = 101), OHT (n = 102) and NPG (105). The GDx number's ability to differentiate between normal and glaucoma individuals was then investigated. We also studied the relationship between the GDx number and retinal nerve fibre layer (RNFL) average thickness and visual field status to examine how well the GDx number reflects disease severity. RESULTS: The GDx number was significantly different among the groups (P < 0.01); it was highest in NPG and lowest in normal controls. The GDx number differentiated between glaucoma and normal with sensitivity of 92.3% and specificity of 96%. When combined with the parameter of RNFL average thickness, sensitivity and specificity were 88.5% and 100% respectively. In NPG a significant correlation was found between the GDx number and RNFL average thickness(rho = -0.88, P < 0.001) and visual field mean deviation (rho = -0.64, P < 0.001). CONCLUSION: The GDx number is able to differentiate between groups of normal, OHT and NPG subjects. Its close relationship with RNFL average thickness and visual field status in glaucoma indicates that it is able to reflect disease severity. Furthermore, its measured ability to distinguish between normal individuals and those with glaucoma demonstrates potential for use in glaucoma diagnosis.

Adult↗
PubMed2001

Glaucoma surgery with or without adjunctive antiproliferatives in normal tension glaucoma: 2 Visual field progression.

BACKGROUND: Reduction of intraocular pressure by 20-30% with glaucoma drainage surgery slows disease progression in normal tension glaucoma (NTG). It is not clear whether adjunctive antiproliferative agents are necessary or safe in eyes at low risk for scarring. METHOD: 61 eyes of 61 white patients with NTG who had undergone a primary guarded fistulising procedure were reviewed. 20 eyes had no antiproliferatives (nil), 29 had peroperative 5-fluorouracil (5-FU), and 12 had peroperative mitomycin C (MMC). Pointwise linear regression analysis (PROGRESSOR for Windows software) was applied to their visual field series starting with the first visual field following surgery and adding subsequent visual fields one at a time. Progression of visual field loss was defined as the appearance of a regression slope 1 dB per year or more with a significance of p<0.01 at one or more visual field locations which remained consistent with the addition of two of three successive visual fields. Time updated covariate analysis was used to determine the relation between variables that changed with time, such as IOP, and the risk of progression. RESULTS: The median percentage IOP reduction was 24.4 for the nil group, 38.0 for the 5-FU group, and 47.5 for the MMC group (p=0.001). There was a statistically significant relation between percentage change in IOP and risk of visual field progression in the subsequent 6 month period for all patients analysed as one group, hazard ratio = -0.021 (p=0.002). There was a statistically significantly increase in the risk of visual field progression for the MMC group compared with the 5-FU group, hazard ratio = 1.51 (p=0.02). CONCLUSION: In NTG patients, the IOP reduction produced by drainage surgery reduces the risk that visual field progression may be reduced after drainage surgery; this is related to the level of IOP reduction. The percentage drop in IOP during a given time is related to the risk of subsequent visual field progression. However, the use of MMC is associated with a greater risk of visual field progression despite a greater fall in IOP. This visual field deterioration may be related to the functional loss produced by late postoperative complications which have been reported at a higher rate in this group. The use of adjunctive perioperative 5-FU should maintain a suitable target IOP with preservation of visual function without the additional complications and associated visual deterioration seen with adjunctive MMC.

Aged↗
PubMed2001

Optic disc changes following trabeculectomy: longitudinal and localisation of change.

AIMS: To determine whether there were any changes in the optic disc at 2 years after trabeculectomy. To determine the factors that most influenced change and whether change was localised to any region of the optic disc. METHODS: 95 patients undergoing routine trabeculectomy as part of the ongoing Moorfields/MRC 5-fluorouracil trial were recruited into the study. Eyes were imaged preoperatively (4 (SD 3) weeks) with the Heidelberg retina tomograph (HRT, Heidelberg Engineering), and at 3 months (SD 2 weeks), 1 year (SD 1 month), and 2 years (SD 1 month) after surgery. Parameters investigated for change were rim area, rim volume, and maximum cup depth. The predefined segment analysis available on the HRT analysis software was used to determine segmental change. RESULTS: The images of 70 patients were analysed. Intraocular pressure reduced from 22.25 (SD 3.76) mm Hg, at the time of preoperative imaging to 15.27 (SD 4.96) mm Hg at 3 months, 14.38 (SD 3.89) mm Hg at 1 year, and 13.80 (SD 3.54) mm Hg at 2 years after trabeculectomy. An increase in rim area and rim volume was present at all time points after surgery, but was only found to be statistically significant at 2 years after surgery. Maximum depth of cup reduced by month 3 and month 12, but showed a slight increase at 2 years after surgery, although this was still lower than the preoperative measure. Segmental analysis found a significant change in rim volume in the nasal, inferonasal, superonasal, and superotemporal regions at 2 years after surgery. No significant regional localisation for change was found at any other time point or in any other parameter investigated. CONCLUSIONS: Reversal of disc cupping is present at 2 years after trabeculectomy. The factor most influencing change is reduction of intraocular pressure. Segmental analysis showed that change in rim volume was greatest in the nasal, inferonasal, superonasal and superotemporal regions at 2 years.

Aged↗
PubMed2000

Chromosomal duplication involving the forkhead transcription factor gene FOXC1 causes iris hypoplasia and glaucoma.

The forkhead transcription factor gene FOXC1 (formerly FKHL7) is responsible for a number of glaucoma phenotypes in families in which the disease maps to 6p25, although mutations have not been found in all families in which the disease maps to this region. In a large pedigree with iris hypoplasia and glaucoma mapping to 6p25 (peak LOD score 6.20 [recombination fraction 0] at D6S967), no FOXC1 mutations were detected by direct sequencing. However, genotyping with microsatellite repeat markers suggested the presence of a chromosomal duplication that segregated with the disease phenotype. The duplication was confirmed in affected individuals by FISH with markers encompassing FOXC1. These results provide evidence of gene duplication causing developmental disease in humans, with increased gene dosage of either FOXC1 or other, as yet unknown genes within the duplicated segment being the probable mechanism responsible for the phenotype.

Chromosomes, Human, Pair 6↗
PubMed2000

Longitudinal nerve fibre layer thickness change in normal-pressure glaucoma.

PURPOSE: To investigate longitudinal retinal nerve fibre layer (RNFL) thickness change in patients with normal-pressure glaucoma (NPG) and to assess how this may be related to visual fields. METHODS: NPG patients and normal subjects who had had serial GDx nerve fibre layer Analyzer II imaging and Humphrey visual fields performed at least 18 months apart were selected for study. These measurements were compared between groups at baseline and at subsequent follow-up, for change over time. RESULTS: Seventy-five NPG patients and 35 normal subjects were studied. Significant differences in RNFL thickness were found between NPG patients and normal controls at baseline (P < or = 0.001). Over the same time, there was greater RNFL thinning in NPG patients than in normal subjects (P < or = 0.0001). RNFL thinning in NPG was negatively correlated with visual field log MD at baseline (P < 0.001) and change in MD over time (P < 0.001). CONCLUSION: Reduction of RNFL thickness over time was significantly greater in NPG patients than in normal subjects, indicating that NPG patients' RNFL had thinned at a faster rate. NPG patients with initially better visual fields had a greater reduction in RNFL thickness than did those with initially more advanced visual field defects, suggesting that more RNFL change may be observed when glaucoma is at an earlier stage. There was a direct relationship between RNFL thinning and visual field deterioration.

Aged↗
PubMed2000

Mapping the visual field to the optic disc in normal tension glaucoma eyes.

PURPOSE: To establish the anatomical relationship between visual field test points in the Humphrey 24-2 test pattern and regions of the optic nerve head (ONH) DESIGN: Cross-sectional study. PARTICIPANTS: Glaucoma patients and suspects from the Normal Tension Glaucoma Clinic at Moorfields Eye Hospital. METHODS: Sixty-nine retinal nerve fiber layer (RNFL) photographs with well-defined RNFL defects and/or prominent bundles were digitized. An appropriately scaled Humphrey 24-2 visual field grid and an ONH reference circle, divided into 30 degrees sectors, were generated digitally. These were superimposed onto the RNFL images. The relationship of visual field test points to the circumference of the ONH was estimated by noting the proximity of test points to RNFL defects and/or prominent bundles. The position of the ONH in relation to the fovea was also noted. MAIN OUTCOME MEASURES: The sector at the ONH corresponding to each visual field test point, the position of the ONH in relation to the fovea, and the effect of the latter on the former. RESULTS: A median 22 (range, 4-58), of a possible 69, ONH positions were assigned to each visual field test point. The standard deviation of estimations was 7.2 degrees. The position of the ONH was 15.5 degrees (standard deviation 0.9 degrees ) nasal and 1.9 degrees (standard deviation 1.0 degrees ) above the fovea. The location of the ONH had a significant effect on the corresponding position at the ONH for 28 of 52 visual field test points. CONCLUSIONS: A clinically useful map that relates visual field test points to regions of the ONH has been produced. The map will aid clinical evaluation of glaucoma patients and suspects, as well as form the basis for investigations of the relationship between retinal light sensitivity and ONH structure.

Cross-Sectional Studies↗
PubMed2000

Glaucomatous optic disc changes in the contralateral eye of unilateral normal pressure glaucoma patients.

OBJECTIVE: To evaluate the optic disc for structural abnormalities in the contralateral eye of unilateral normal pressure glaucoma patients. DESIGN: Cross-sectional study. PARTICIPANTS: Fifty-three unilateral normal pressure glaucoma patients. TESTING: Optic disc imaging with the Heidelberg Retina Tomograph (HRT). MAIN OUTCOME MEASURES: Optic disc structural parameters. RESULTS: Of the contralateral (normal visual field) eyes, 79.2% were found to have an abnormal optic disc by HRT analysis. Of the glaucomatous (abnormal visual field) eyes, 94.3% were found to have an abnormal disc. The patterns of disc abnormality were defined as marked or moderate diffuse thinning of the neuroretinal rim (NRR) or broad or narrow focal thinning of the NRR. The most common pattern in the contralateral eyes was moderate diffuse thinning of the NRR (45.2%). The most frequently abnormal segments were the nasal superior (73. 8%) followed by the nasal inferior and the global NRR parameter (both 54.8%). CONCLUSIONS: A high frequency of NRR thinning was found in the contralateral (normal visual field) eyes of unilateral normal pressure glaucoma patients by HRT analysis. Knowing whether these abnormalities predict future progression to the development of visual field abnormality must wait until longitudinal studies are completed. If a disc abnormality is shown to predict future field loss, then early identification will allow early treatment.

Aged↗
PubMed2000

Identifying early glaucomatous changes. Comparison between expert clinical assessment of optic disc photographs and confocal scanning ophthalmoscopy.

OBJECTIVE: To compare the ability of expert clinicians, using qualitative assessment of stereoscopic optic disc photographs, and confocal scanning laser ophthalmoscope imaging to discriminate between healthy persons and patients with early glaucoma. DESIGN: Comparative instrument validation study. PARTICIPANTS: Seventy-two healthy persons and 51 patients with early glaucoma (average visual field mean deviation, -3.6 dB). Early glaucoma was defined as a history of ocular hypertension and a reproducible visual field defect scoring 5 or less in the Advanced Glaucoma Intervention Study classification, regardless of optic disc appearance. INTERVENTION: Stereoscopic optic nerve head (ONH) photography and Heidelberg Retina Tomograph (HRT) imaging, (Heidelberg Engineering GmbH, Dossenheim, Germany). MAIN OUTCOME MEASURES: Ability of clinical assessment of stereoscopic ONH photographs and analysis of HRT parameters, taking into account the optic disc size, to detect early glaucomatous optic disc changes. RESULTS: The specificity of the majority opinion of five observers to detect early glaucomatous optic disc changes was 94.4%, with a sensitivity of 70.6%. Using the HRT analysis, the specificity was 95.8% and the sensitivity was 84. 3%. CONCLUSIONS: Heidelberg Retina Tomograph image analysis that takes into account the optic disc size is more sensitive than clinical assessment of stereoscopic optic disc photographs in distinguishing between healthy persons and patients with early glaucoma.

Aged↗
PubMed2000

Use of the GDx to detect differences in retinal nerve fibre layer thickness between normal, ocular hypertensive and early glaucomatous eyes.

PURPOSE: The GDx is a scanning laser polarimeter that has been developed to allow the quantitative analysis of retinal nerve fibre layer (RNFL) thickness. The purpose of this study was to determine whether differences in the RNFL thickness between normal, ocular hypertensive and glaucomatous eyes could be detected using the GDx. METHODS: RNFL analysis was carried out using the GDx on 33 normal, 145 ocular hypertensive (OHT) and 44 glaucomatous (POAG) eyes. The inclusion criteria for entry into the study did not include the clinical appearance of the RNFL or optic disc, thus eliminating an important source of selection bias. The Kruskal-Wallis one-way analysis of variance was used to determine whether any significant differences existed among the groups in mean total and quadrantic RNFL thickness. When significant differences were found, specific inter-group analysis was carried out using the Mann-Whitney U-test. RESULTS: Significant differences in RNFL thickness were found for the mean total, superior and inferior quadrant values between normals and OHT eyes as compared with POAG eyes. No significant differences were found for these values between the normal and OHT eyes. CONCLUSION: Analysis of RNFL thickness using the GDx was able to detect differences between POAG eyes compared with normal and OHT eyes, although there was considerable overlap between groups. Further assessment of the technique is required to determine whether it may be useful in screening for the presence of early glaucomatous damage.

Aged↗
PubMed2000

Response time prolongation for a motion stimulus in patients with glaucoma and its relationship with elevation of the motion threshold.

PURPOSE: To investigate whether response times for a motion stimulus are prolonged in glaucoma and to investigate the relationship between response time prolongation and motion threshold elevation in glaucoma. METHOD: Motion displacement thresholds and response times were measured in 15 patients with glaucoma and 18 age-matched control subjects. RESULTS: Mean test response times were significantly prolonged in the glaucomatous eyes than in the control eyes, with a mean delay of 200 milliseconds. After correcting for threshold elevation, response times at the motion threshold showed no significant difference between the groups. CONCLUSIONS: Response times for motion detection are significantly prolonged in glaucoma and are accounted for by the threshold elevation in patients with glaucoma. The implications of these results are discussed in terms of the use of response time analysis to determine subject reliability.

Adult↗
PubMed2000

Comparison of visual field progression in patients with normal pressure glaucoma between eyes with and without visual field loss that threatens fixation.

AIM: To compare the frequency and site of visual field progression and changes in visual acuity in patients with normal pressure glaucoma (NPG) with and without pre-existing visual field loss. METHOD: Patients with normal tension glaucoma were selected who had at least 10 visual fields over 5 or more years of follow up and no other condition that might influence the visual field or visual acuity. Alternate left and right eyes were selected from patients in random order. These eyes were then subdivided according to visual field defect threatening fixation, visual field defect not threatening fixation, and no visual field defect (fellow eyes). Eyes were defined as showing a threat to fixation according to the presence of a visual field defect involving one of more of four paracentral visual field locations. Pointwise linear regression analysis was applied to each visual field series using PROGRESSOR software. Progression of visual field loss was defined as the appearance of a regression slope 1 dB per year or more with a significance of p<0.01, which remained consistent with the addition of two of three successive visual fields to the series. The number of patients showing progression and the number where progression occurred in one of the four paracentral visual field locations was noted. The number of eyes losing two or more lines of Snellen visual acuity over the follow up period was also noted. RESULTS: 174 eyes of 174 patients were selected. 106 eyes had visual field loss threatening fixation, 46 eyes had visual field loss that did not threaten fixation, and 22 were fellow eyes with normal visual fields. The median follow up was 7.2 years. Eight eyes (36.4%) in the "normal visual fields" group, 31 eyes (67.4%) in the "visual field loss away from fixation" group, and 87 eyes (82.1%) in the "threat to fixation" group showed progression in any part of the visual field. Two eyes (9.1%) in the "normal visual fields" group, nine eyes (19.6%) in the "visual field loss away from fixation" group, and 45 eyes (42.5%) in the "threat to fixation" group showed progression at "threat to fixation". The Cox proportional hazards regression model showed an increased risk of progression at any part of the visual field for female sex and a decreased risk for eyes with normal visual fields. For progression at threat to fixation this model showed an increased risk with pre-existing threat to fixation. Eyes from older patients and those that went on to have progressive visual field loss at fixation were more likely to lose two lines of Snellen visual acuity over the follow up period. CONCLUSION: Since 20-30% of previously field damaged eyes and over 60% without prior field loss fail to demonstrate progressive visual field damage over a long follow up it is recommended that normal pressure glaucoma patients be monitored for progression and that potentially harmful therapy be withheld until progression is demonstrated. Although the presence of visual field loss that threatens fixation does not constitute an increased risk of visual field progression it does indicate an increased risk of further loss of visual field close to fixation which is in turn associated with loss of central acuity. In the light of this finding, patients with visual field loss that threatens fixation should be managed more aggressively.

Aged↗
PubMed2000

Glaucoma surgery with or without adjunctive antiproliferatives in normal tension glaucoma: 1 intraocular pressure control and complications.

BACKGROUND: Reduction of intraocular pressure (IOP) by 20-30% with glaucoma drainage surgery slows disease progression in normal tension glaucoma (NTG). It is not clear whether adjunctive antiproliferative agents are necessary or safe in eyes at low risk for scarring. METHOD: 86 eyes of 73 white NTG patients who had undergone a primary guarded fistulising procedure were reviewed. 25 eyes had no antiproliferatives, 36 had peroperative 5-fluorouracil (5-FU) and 25 had peroperative mitomycin C (MMC). Their postoperative IOPs, complications, and changes in visual acuity were recorded. RESULTS: Eyes that had no adjunctive antiproliferative less commonly maintained a 20-30% reduction in IOP (47.4% at 2 years) compared with either the 5-FU group (69.4%at 2 years, p=0.01) or the MMC group (64.9% at 2 years, p=0.04). Eyes that had adjunctive MMC more often had late hypotony (28%, p=0.02) and late bleb leak (12%, p<0.001). Eyes that had adjunctive MMC also more often had a two lines loss of Snellen visual acuity (39.8% by 2 years) compared with those that had adjunctive 5-FU (14.7% by 2 years), p=0.06. CONCLUSION: For NTG patients at low risk of scarring trabeculectomy with adjunctive peroperative 5-FU should maintain a suitable target IOP without the additional sight threatening complications seen with adjunctive MMC.

Aged↗
PubMed2000

Use of sequential Heidelberg retina tomograph images to identify changes at the optic disc in ocular hypertensive patients at risk of developing glaucoma.

AIM: To determine if global and segmental changes in optic disc parameters of sequential Heidelberg retina tomograph (HRT) images develop in individual ocular hypertensive (OHT) patients without white on white visual field defects. METHODS: Patients and normal controls were recruited from a prospective ocular hypertension treatment trial. The subject groups consisted of 21 OHT patients who had converted to early glaucoma on the basis of visual field criteria (24-2 program on the Humphrey perimeter), 164 OHT subjects with normal visual fields, and 21 normal controls. Sequential HRT images 16-21 months apart were obtained for each subject and segmental optic disc parameters were measured to determine if any change had occurred. From the analysis of sequential HRT images of the 21 normal eyes we established normal limits of interimage variation. Individual discs in each group showing changes above the 95% limit of normal variability were then sought. RESULTS: Several segmental and global optic disc parameters were found to show significant change in the converter group before confirmed visual field change, confirming our previously published results. Individual optic disc analysis using the 95% limit of normal variability data demonstrated glaucomatous change in 13 out of 21 converter eyes. 47 of the 164 OHT eyes with normal visual fields showed change in global and segmental parameters in a "glaucomatous" direction above the level expected for normal variability. The parameters which changed most frequently in the OHT eyes were: global cup volume (6.7% of discs), inferonasal cup volume (11%), inferotemporal cup volume (8.5%), and superotemporal cup area (7.3%). CONCLUSIONS: We have identified change in a subset of ocular hypertensive patients which could predate the development of glaucomatous visual field loss. The HRT could be of value in the sequential follow up of those suspected of having glaucoma by identifying eyes at risk of developing glaucoma. However, further refinement of the technique is required to eliminate some of the inherent variability of the analysis method described, and to increase the ability to detect at risk individuals.

Adult↗
PubMed2000

Scaling the hill of vision: the physiological relationship between light sensitivity and ganglion cell numbers.

PURPOSE: Differential light sensitivity (DLS) in white-on-white perimetry is used as a measure of ganglion cell function to estimate the amount of neuronal damage in glaucoma. The physiological relationship between DLS and ganglion cell numbers is poorly understood. Within small retinal areas, brightness information is summated, so that A * L = C, or A = C/L, where A is target area, L is threshold luminance, and C is a constant. In larger illuminated areas, as with a Goldmann size III target in perimetry, summation is incomplete, so that A(k) = C/L, where k is the coefficient of summation, and 0 < k < 1. This study tests the hypothesis that the target area (A) can be represented by the number of underlying ganglion cells (G) to give G(k) = C/L. METHODS: Normative human data for ganglion cell density within 30 degrees of retinal eccentricity were taken from the literature and corrected for lateral displacement of ganglion cells from the fovea to estimate ganglion cell receptive field density (g). The number of ganglion cell receptive fields within a Goldmann size III target (G) was calculated from target area (A) and receptive field density (g) [G = A (g)]. Normative data for DLS in the central 30 degrees (Humphrey 30-2) were taken from the literature. The coefficient summation (k) was measured empirically at each Humphrey 30-2 test point in 8 normal subjects. The relationship between DLS and G was investigated by plotting DLS as decibels (dB) against G and DLS as 1/L (1/Lamberts) against G(k). The physiological relationship was extrapolated to glaucomatous ganglion cell loss by calculating hypothetical cell losses for 3 and 6 dB sensitivity defects at each test point. RESULTS: Spatial summation increased with eccentricity. The relationship between DLS (dB) and G was curvilinear. The relationship between DLS (1/L) and G(k) was linear (r2 = 0.73). The extrapolation to glaucomatous ganglion cell loss indicated that a proportionally greater loss of ganglion cells is required in the central compared with peripheral visual field for equal losses in dB sensitivity. CONCLUSIONS: The number of underlying ganglion cells, adjusted for local spatial summation, is better reflected by the DLS scale of 1/L than by dB. If spatial summation is unchanged in glaucoma, this scale more accurately reflects the amount of neuronal damage.

Adult↗
PubMed2000

Changing views on open-angle glaucoma: definitions and prevalences--The Rotterdam Study.

PURPOSE: To create a quantitative basis for diagnostic criteria for open-angle glaucoma (OAG), to propose an epidemiologic definition for OAG based on these, and to determine the prevalence of OAG in a general white population. METHODS: Of the 7983 subjects 55 years of age or older participating in the population-based Rotterdam Study, 6756 subjects participated in the ophthalmic part of this study (6281 subjects living independently and 475 in nursing homes). The criteria for the diagnosis of OAG were based on ophthalmoscopic and semiautomated Imagenet estimations of the optic disc such as vertical cup-to-disc ratio (VCDR), minimal width of neural rim, or asymmetry in VCDR between both eyes, and visual field testing with kinetic Goldmann perimetry. All criteria for the diagnosis of OAG were assessed in a masked way independently of each other. RESULTS: Mean VCDR on ophthalmoscopy was 0.3 and with Imagenet 0.49, and the 97.5th percentile for both was 0.7. The prevalence of glaucomatous visual field defects was 1.5%. Overall prevalence of definite OAG in the independently living subjects was 0.8% (95% confidence interval [CI] 0.6, 1.0; 50 cases). Prevalence of OAG in men was double that in women (odds ratio 2.1; 95% CI 1.2, 3.6). Different commonly used criteria for diagnosis of OAG resulted in prevalence figures ranging from 0.1% to 1.2%. CONCLUSIONS: The overall prevalence of OAG in the present study was comparable to most population-based studies. However, prevalence figures differed by a factor of 12 when their criteria for OAG were applied to this population. A definition for definite OAG is proposed: a glaucomatous optic neuropathy in eyes with open angles in the absence of history or signs of secondary glaucoma characterized by glaucomatous changes based on the 97.5 percentile for this population together with glaucomatous visual field loss. In the absence of the latter or of a visual field test, it is proposed to speak of probable OAG based on the 99.5th or possible OAG based on the 97.5th percentiles of glaucomatous disc changes for a population under study.

Age Distribution↗