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Dive into the research topics where Sarah L. Hosking is active.

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Featured researches published by Sarah L. Hosking.


British Journal of Ophthalmology | 2004

Ocular haemodynamic responses to induced hypercapnia and hyperoxia in glaucoma

Sarah L. Hosking; A Harris; Hak Sung Chung; C. Jonescu-Cuypers; L. Kagemann; E J Roff Hilton; Hanna J. Garzozi

Aim: To determine the ocular haemodynamic response to gas perturbations in glaucoma. Methods: Intraocular pressure (IOP), systemic systolic and diastolic blood pressure (SBP and DBP), and retrobulbar blood flow velocities, measured by colour Doppler imaging (CDI), were recorded at two visits. CDI was used to measure peak systolic and end diastolic velocities (PSV and EDV) and resistance index (RI) in the ophthalmic artery (OA), central retinal artery (CRA), and short posterior ciliary arteries (SPCAs). At the first visit, measurements were taken at baseline (B1: breathing room air) and during isoxic hypercapnia (end tidal PCO2 increased 15% above baseline) in 16 normal subjects and 12 patients with glaucoma. On another day, measurements were repeated at a second baseline (B2) and during hyperoxia (100% oxygen breathing) for 15 normal subjects and 13 glaucoma patients. Baseline systemic data were compared using paired t tests; REANOVA was performed to compare group differences at baseline and to determine the vessel response to each condition. Fisher’s LSD was used for post hoc comparison. Results: Baseline OA PSV was lower for the glaucoma than for the normal group (p = 0.047); the groups were otherwise similar at baseline. IOP demonstrated no response to hypercapnia, but reduced during hyperoxia for both the normal subjects (p<0.0001) and glaucoma patients (p = 0.04). During hypercapnia, SBP increased in normal subjects (p = 0.03) and glaucoma patients (p = 0.01); DBP increased in normal subjects (p = 0.021). There was a corresponding increase in ocular perfusion pressure (OPP) for normal subjects (p = 0.01) and glaucoma subjects (p = 0.028), and as a result OPP was included as a covariate in the REANCOVA model. Hypercapnia resulted in increased PSV in the CRA of normal subjects (p = 0.035) and increased PSV and EDV in the SPCAs of glaucoma patients (p = 0.041 and p = 0.030 respectively). Hyperoxia resulted in reduced PSV and EDV in the ophthalmic arteries of normal subjects only (p = 0.001 and 0.031 respectively). Conclusions: These findings suggest the presence of relative vasoconstriction in glaucoma patients, which is at least partially reversed by hypercapnia.


Journal of Cataract and Refractive Surgery | 2004

Corneal pachymetry in normal and keratoconic eyes: Orbscan II versus ultrasound

Doina Gherghel; Sarah L. Hosking; Sanjay Mantry; S Banerjee; Shehzad A. Naroo; Sunil Shah

Purpose: To compare corneal thickness measurements using Orbscan II (OII) and ultrasonic (US) pachymetry in normal and in keratoconic eyes. Setting: Eye Department, Heartlands and Solihull NHS Trust, Birmingham, United Kingdom. Methods: Central corneal thickness (CCT) was measured by means of OII and US pachymetry in 1 eye of 72 normal subjects and 36 keratoconus patients. The apical corneal thickness (ACT) in keratoconus patients was also evaluated using each method. The mean of the difference, standard deviation (SD), and 95% limits of agreement (LoA = mean ± 2 SD), with and without applying the default linear correction factor (LCF), were determined for each sample. The Student t test was used to identify significant differences between methods, and the correlation between methods was determined using the Pearson bivariate correlation. Bland‐Altman analysis was performed to confirm that the results of the 2 instruments were clinically comparable. Results: In normal eyes, the mean difference (± 95% LoA) in CCT was 1.04 &mgr;m ± 68.52 (SD) (P>.05; r = 0.71) when the LCF was used and 46.73 ± 75.40 &mgr;m (P = .0001; r = 0.71) without the LCF. In keratoconus patients, the mean difference (± 95% LoA) in CCT between methods was 42.46 ± 66.56 &mgr;m (P<.0001: r = 0.85) with the LCF, and 2.51 ± 73.00 &mgr;m (P>.05: r = 0.85) without the LCF. The mean difference (± 95% LoA) in ACT for this group was 49.24 ± 60.88 &mgr;m (P<.0001: r = 0.89) with the LCF and 12.71 ± 68.14 &mgr;m (P = .0077; r = 0.89) when the LCF was not used. Conclusions: This study suggests that OII and US pachymetry provide similar readings for CCT in normal subjects when an LCF is used. In keratoconus patients, OII provides a valid clinical tool for the noninvasive assessment of CCT when the LCF is not applied.


British Journal of Ophthalmology | 2008

Performance of the compensation comparison method for retinal straylight measurement: effect of patient’s age on repeatability

Alejandro Cerviño; Robert Montés-Micó; Sarah L. Hosking

Aim: The assessment of repeatability and reproducibility of retinal straylight measurements with the C-Quant straylight meter (Oculus AG, Germany) and the effect of patient’s age on the instrument performance are tested with a series of experiments. Methods: First, 20 eyes from 20 subjects (mean age 26.9 (SD 2.7) years, mean refractive error −1.34 (2.72) D) were examined with the C-Quant straylightmeter, taking 10 consecutive readings. Five subjects were also examined on five consecutive days to assess reproducibility. Additionally, repeated measures of straylight from 84 subjects of ages ranging from 19 to 86 years (mean (SD): 42.4 (24.0) years) were retrospectively analysed to assess the effect of patient’s age on repeatability. Results: The results failed to show significant differences between the readings taken within the same session (mean (0.07), p>0.05) or between sessions (mean (0.05), p>0.05). Variability of intrasession measurements was not significant for subjects of different age (p = 0.094). Conclusion: It may be concluded that the C-Quant straylightmeter is repeatable and reliable for the assessment of retinal straylight in human eyes. Age of the patient does not decrease repeatability, even though they feel more insecure about their ability to perform the test.


Seizure-european Journal of Epilepsy | 2004

The effect of antiepileptic drugs on visual performance

Emma J. Roff Hilton; Sarah L. Hosking; Tim Betts

Visual disturbances are a common side-effect of many antiepileptic drugs. Non-specific retino- and neurotoxic visual abnormalities, that are often reported with over-dosage and prolonged AED use, include diplopia, blurred vision and nystagmus. Some anticonvulsants are associated with specific visual problems that may be related to the mechanistic properties of the drug, and occur even when the drugs are administered within the recommended daily dose. Vigabatrin, a GABA-transaminase inhibitor, has been associated with bilateral concentric visual field loss, electrophysiological changes, central visual function deficits including reduced contrast sensitivity and abnormal colour perception, and morphological alterations of the fundus and retina. Topiramate, a drug that enhances GABAergic transmission, has been associated with cases of acute closed angle glaucoma, while tiagabine, a GABA uptake inhibitor, has been investigated for a potential GABAergic effect on the visual field. Only mild neurotoxic effects have been identified for patients treated with gabapentin, a drug designed as a cyclic analogue of GABA but exhibiting an unknown mechanism while carbamazepine, an inhibitor of voltage-dependent sodium channels, has been linked with abnormal colour perception and reduced contrast sensitivity. The following review outlines the visual disturbances associated with some of the most commonly prescribed anticonvulsants. For each drug, the ocular site of potential damage and the likely mechanism responsible for the adverse visual effects is described.


Graefes Archive for Clinical and Experimental Ophthalmology | 1999

Comprehensive assessment of retinal, choroidal and retrobulbar haemodynamics during blood gas perturbation

Emma J. Roff; Alon Harris; Hak Sung Chung; Sarah L. Hosking; Alexandra M. Morrison; Paul J. Halter; Larry Kagemann

Abstract · Background: A study was performed to evaluate the effect of isoxic hypercapnia on ocular haemodynamics using colour Doppler imaging (CDI), scanning laser Doppler flowmetry (SLDF) and ocular blood flow (OBF) tonography. · Methods: Measurements were taken for one eye of each of 14 healthy subjects (mean age 27±6 years) during breathing of room air and then during isoxic hypercapnia (breathing CO2 and room air). Using CDI, blood flow velocities and resistance indices were determined for the ophthalmic artery (OA), central retinal artery (CRA) and short posterior ciliary arteries (SPCAs). Using SLDF, a 10×10 pixel frame was used to measure blood flow, volume and velocity in each quadrant of the peripapillary retina. Pulsatile ocular blood flow (POBF) was measured using the OBF tonograph. · Results: Using CDI, peak systolic and end diastolic velocities increased and resistance index decreased significantly in the SPCAs during hypercapnia. Using SLDF, blood flow, volume and velocity increased significantly during hypercapnia in the superior temporal quadrant of the peripapillary retina. No significant difference was observed between baseline and hypercapnia for POBF. · Conclusions: Isoxic hypercapnia resulted in an increase in peripapillary retinal and SPCA blood flow parameters as determined by SLDF and CDI respectively. This implies the presence of autoregulatory activity in these vasculatures. These findings may be of significance in the pathogenesis of ocular disease such as glaucoma where autoregulation is thought to be compromised.


Journal of Cataract and Refractive Surgery | 2008

Retinal straylight in patients with monofocal and multifocal intraocular lenses

Alejandro Cerviño; Sarah L. Hosking; Robert Montés-Micó; Jorge L. Alió

PURPOSE: To determine the differences in retinal straylight perceived by patients with monofocal intraocular lenses (IOLs) and patients with multifocal IOLs. SETTING: Vissum‐Instituto de Oftalmológico de Alicante, Alicante, Spain. METHODS: In this prospective study, contrast sensitivity and retinal straylight were measured prospectively 6 months postoperatively in 67 eyes of 40 patients with a monofocal or multifocal IOL. In the monofocal group, a ThinOptX IOL (ThinOptX, Inc.) was implanted in 12 eyes and an Acri.Smart 48 S IOL (Acri.Tec) in 20 eyes. In the multifocal IOL group, a ReZoom IOL (Advanced Medical Optics) was implanted in 13 eyes and a ReSTOR IOL (Alcon Laboratories) in 22 eyes. RESULTS: All measured values were similar between the monofocal and multifocal groups. Contrast sensitivity correlated significantly with the retinal straylight value (r = 0.258; P = .026) and the mean residual spherical equivalent. There was no statistically significant relationship between IOL type and the retinal straylight value (P = .089). Adjusted mean scores suggest that straylight values in the monofocal group were slightly higher than in the multifocal group. In the monofocal group, retinal straylight values were significantly correlated with pupil size (r = −0.377; P = .033). In the multifocal group, a correlation was found between retinal straylight values and contrast sensitivity (r = 0.397; P = .024). After controlling for age differences, there were no significant differences in retinal straylight between IOLs (P = .069). CONCLUSIONS: No significant differences in straylight values were found between multifocal IOLs and monofocal IOLs. Pupil miosis during retinal straylight measurement and neural adaptation after multifocal IOL implantation may overcome differences between IOLs.


British Journal of Ophthalmology | 2003

Contrast sensitivity improves after brimonidine therapy in primary open angle glaucoma: a case for neuroprotection.

David W. Evans; Sarah L. Hosking; D Gherghel; Jimmy D. Bartlett

Aims: To determine the visual outcome following initiation of brimonidine therapy in glaucoma. Methods: 16 newly diagnosed previously untreated glaucoma patients were randomly assigned to either timolol 0.5% or brimonidine 0.2%. Visual acuity, contrast sensitivity (CS), visual fields, intraocular pressure (IOP), blood pressure, and heart rate were evaluated at baseline and after 3 months. Results: IOP reduction was similar for both groups (p<0.05). Brimonidine improved CS; in the right eye at 6 and 12 cpd (p = 0.043, p = 0.017); in the left eye at 3 and 12 cpd (p = 0.044, p = 0.046). Timolol reduced CS at 18 cpd in the right eye (p = 0.041). There was no change in any other measured parameters. Conclusion: Glaucoma patients exhibit improved CS on initiation of brimonidine therapy.


Current Eye Research | 2002

The effect of corneal thickness and corneal curvature on pneumatonometer measurements.

Andrew Morgan; Justine Harper; Sarah L. Hosking; Bernard Gilmartin

Purpose. The purpose of this study was to investigate the influence of corneal topography and thickness on intraocular pressure (IOP) and pulse amplitude (PA) as measured using the Ocular Blood Flow Analyzer (OBFA) pneumatonometer (Paradigm Medical Industries, Utah, USA). Methods. 47 university students volunteered for this crosssectional study: mean age 20.4 yrs, range 18 to 28 yrs; 23 male, 24 female. Only the measurements from the right eye of each participant were used. Central corneal thickness and mean corneal radius were measured using Scheimpflug biometry and corneal topographic imaging respectively. IOP and PA measurements were made with the OBFA pneumatonometer. Axial length was measured using A-scan ultrasound, due to its known correlation with these corneal parameters. Stepwise multiple regression analysis was used to identify those components that contributed significant variance to the independent variables of IOP and PA. Results. The mean IOP and PA measurements were 13.1 (SD 3.3) mmHg and 3.0 (SD 1.2) mmHg respectively. IOP measurements made with the OBFA pneumatonometer correlated significantly with central corneal thickness (r = +0.374, p = 0.010), such that a 10 µm change in CCT was equivalent to a 0.30mmHg change in measured IOP. PA measurements correlated significantly with axial length (part correlate = –0.651, p < 0.001) and mean corneal radius (part correlate = +0.459, p < 0.001) but not corneal thickness. Conclusions. IOP measurements taken with the OBFA pneumatonometer are correlated with corneal thickness, but not axial length or corneal curvature. Conversely, PA measurements are unaffected by corneal thickness, but correlated with axial length and corneal radius. These parameters should be taken into consideration when interpreting IOP and PA measurements made with the OBFA pneumatonometer.


Graefes Archive for Clinical and Experimental Ophthalmology | 2010

Ocular blood flow measurements in healthy human myopic eyes

Alexandra Benavente-Perez; Sarah L. Hosking; Nicola S. Logan; D. C. Broadway

BackgroundTo evaluate the haemodynamic features of young healthy myopes and emmetropes, in order to ascertain the perfusion profile of human myopia and its relationship with axial length prior to reaching a degenerative state.MethodsThe retrobulbar, microretinal and pulsatile ocular blood flow (POBF) of one eye of each of twenty-two high myopes (N = 22, mean spherical equivalent (MSE) ≤−5.00D), low myopes (N = 22, MSE−1.00 to−4.50D) and emmetropes (N = 22, MSE ± 0.50D) was analyzed using color Doppler Imaging, Heidelberg retinal flowmetry and ocular blood flow analyser (OBF) respectively. Intraocular pressure, axial length (AL), systemic blood pressure, and body mass index were measured.ResultsWhen compared to the emmetropes and low myopes, the AL was greater in high myopia (p < 0.0001). High myopes showed higher central retinal artery resistance index (CRA RI) (p = 0.004), higher peak systolic to end diastolic velocities ratio (CRA ratio) and lower end diastolic velocity (CRA EDv) compared to low myopes (p = 0.014, p = 0.037). Compared to emmetropes, high myopes showed lower OBFamplitude (OBFa) (p = 0.016). The POBF correlated significantly with the systolic and diastolic blood velocities of the CRA (p = 0.016, p = 0.036). MSE and AL correlated negatively with OBFa (p = 0.03, p = 0.003), OBF volume (p = 0.02, p < 0.001), POBF (p = 0.01, p < 0.001) and positively with CRA RI (p = 0.007, p = 0.05).ConclusionHigh myopes exhibited significantly reduced pulse amplitude and CRA blood velocity, the first of which may be due to an OBF measurement artefact or real decreased ocular blood flow pulsatility. Axial length and refractive error correlated moderately with the ocular pulse and with the resistance index of the CRA, which in turn correlated amongst themselves. It is hypothesized that the compromised pulsatile and CRA haemodynamics observed in young healthy myopes is an early feature of the decrease in ocular blood flow reported in pathological myopia. Such vascular features would increase the susceptibility for vascular and age-related eye diseases.


Journal of Refractive Surgery | 2003

Nidek OPD-scan analysis of normal, keratoconic, and penetrating keratoplasty eyes

Sunil Shah; Shehzad A. Naroo; Sarah L. Hosking; Doina Gherghel; Sanjay Mantry; Somnath Bannerjee; Katie Pedwell; Harkaran S. Bains

PURPOSE To determine by wavefront analysis the difference between eyes considered normal, eyes diagnosed with keratoconus, and eyes that have undergone penetrating keratoplasty METHODS The Nidek OPD-Scan wavefront aberrometer was used to measure ocular aberrations out to the sixth Zernike order. One hundred and thirty eyes that were free of ocular pathology, 41 eyes diagnosed with keratoconus, and 8 eyes that had undergone penetrating keratoplasty were compared for differences in root mean square value. Three and five millimeter root mean square values of the refractive power aberrometry maps of the three classes of eyes were compared. Radially symmetric and irregular higher order aberration values were compared for differences in magnitude. RESULTS Root mean square values were lower in eyes free of ocular pathology compared to eyes with keratoconus and eyes that had undergone penetrating keratoplasty. The aberrations were larger with the 5-mm pupil. Coma and spherical aberration values were lower in normal eyes. CONCLUSION Wavefront aberrometry of normal, pathological, and eyes after surgery may help to explain the visual distortions encountered by patients. The ability to measure highly aberrated eyes allows an objective assessment of the optical consequences of ocular pathology and surgery. The Nidek OPD-Scan can be used in areas other than refractive surgery.

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Alexandra Benavente-Perez

State University of New York College of Optometry

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