Merrick Moseley - Academia.edu (original) (raw)

Papers by Merrick Moseley

Research paper thumbnail of Effectiveness of occlusion therapy in ametropic amblyopia

The British Journal of Ophthalmology, Jul 1, 1998

To examine the relative contributions of non-specific (for example, spectacle correction) and spe... more To examine the relative contributions of non-specific (for example, spectacle correction) and specific (that is, occlusion therapy) treatment effects on children with ametropic amblyopia. To assess the importance and practicality of objectively confirming the prescribed occlusion dose. Subjects were entered into a two phase trial. In the first ('pretreatment') subjects were provided with spectacle correction and underwent repeat visual acuity (VA) and contrast sensitivity (CS) testing until acuity in their amblyopic eye had stabilised. Subjects then progressed to the second phase ('treatment') in which they underwent direct, unilateral occlusion for 1 hour per day for 4 weeks. Patching was objectively monitored using an occlusion dose monitor. Eight subjects completed the trial, all but one of whom achieved > 80% concordance with the occlusion regimen. Within the pretreatment phase, mean amblyopic eye VA improved by 0.19 log units (p = 0.008) while mean CS gained 0.09 log units (p = 0.01). An identical improvement in mean VA was recorded in the fellow eyes (p = 0.03) while mean CS gained 0.11 log units (p = 0.02). Within the treatment phase, mean VA further improved (0.12 log units, p = 0.009) although this gain had halved by the end of treatment and was no longer statistically significant (p = 0.09). Visual performance improved significantly during pretreatment whereas further gains seen during occlusion were not sustained. Evaluation of occlusion regimens must take into consideration the potentially confounding influence of 'pretreatment effects' and the necessity to confirm objectively the occlusion dose a child receives.

Research paper thumbnail of Whole-body vibration and visual performance: an examination of spatial filtering and time-dependency

Ergonomics, May 1, 1987

Two experiments have examined the effects of whole-body vibration on visual performance. The firs... more Two experiments have examined the effects of whole-body vibration on visual performance. The first experiment concerned alphanumeric reading performance and contrast thresholds for gratings subtending 7-5, 10 and 12-5 cycles per degree (c deg). Seated subjects were exposed to vertical sinusoidal whole-body vibration (4 Hz, 2-5 ms r.m.s.). Greatest reading errors occurred with characters exhibiting a high spatial complexity in

Research paper thumbnail of Ophthalmic surgical training

Journal of the Royal Society of Medicine, Jun 1, 2004

Research paper thumbnail of Sinusoidal and random whole-body vibration: comparative effects on visual performance

Aviation Space and Environmental Medicine

An experimental comparison of the effect of whole-body sinusoidal and one-third octave-band rando... more An experimental comparison of the effect of whole-body sinusoidal and one-third octave-band random vibration on the performance of a display reading task is described. The findings indicate that one-third octave-band random vibration has significantly less effect on performance. Subsequent measurements of rotational head motion demonstrated that this finding may be due to differences in the velocity probability density distributions produced by the different motions. Subjects also performed the visual task during exposure to several broad-band random motions. Predicted error values were obtained by averaging the frequency weighted time histories of these motions. It was found that both R.M.S. and R.M.Q. averaging procedures applied to the broad-band frequency weighted time histories gave accurate error predictions when compared with the measured error scores. Practical implications of the experimental findings and recommendations for future research are discussed.

Research paper thumbnail of Sleep Disturbances among Persons Who Are Visually Impaired: Survey of Dog Guide Users

Journal of visual impairment & blindness

ABSTRACT

Research paper thumbnail of Delayed visual maturation: pupillary responses implicate subcortical and cortical visual systems

Developmental Medicine & Child Neurology

Vision in very early infancy is probably subserved by subcortical pathways, with many cortical pr... more Vision in very early infancy is probably subserved by subcortical pathways, with many cortical processes only fully emerging by 3 months of age. The improvement of vision in delayed visual maturation (DVM) occurs around this time, and this has given rise to the suggestion that the condition may have a subcortical basis that resolves with the appearance of cortical function. To explore further the role of cortical and subcortical visual systems in DVM we studied the visual development in identical twins, one of whom had type 1b DVM. Two non-invasive methods of investigating visual pathway function were employed: the acuity card procedure (a behavioural response) and luminance and grating pupillometry. While the former reflects both subcortical and cortical function and can be detected at birth, pupil responses to gratings reflect cortical activity alone and normally become measurable at 1 month of age. Development of both behavioural and pupillary responses was delayed in DVM, indica...

Research paper thumbnail of Semiautomated computer analysis of vessel growth in preterm infants without and with ROP

British Journal of Ophthalmology

To measure characteristics of the retinal blood vessels close to the optic disc in full term and ... more To measure characteristics of the retinal blood vessels close to the optic disc in full term and preterm infants, with and without retinopathy of prematurity (ROP), using digital imaging. To determine whether these measures are indicative of the presence or severity of ROP in the retinal periphery. 52 digital fundus images from 42 babies were analysed with a semiautomated analysis program developed at Imperial College London. Analysis was limited to the principal temporal vessels close to the optic disc: recording venular diameter and arteriolar diameter and tortuosity. Each result was categorised by the gestational age of the infant ("very premature" 24-27 weeks, "moderately premature" 28-31 weeks, and "near term" > or =32 weeks) and by the highest stage of ROP present ("no ROP," "mild ROP" stage 1 or 2, and "severe ROP" stage 3). Arteriolar tortuosity was found to vary significantly (Kruskal-Wallis p=0.002) with ROP se...

Research paper thumbnail of Ch 55. The applied physiology of the eye and visual system

Research paper thumbnail of Personalized versus standardized dosing strategies for the treatment of childhood amblyopia: study protocol for a randomized controlled trial

Trials, Jan 25, 2015

Amblyopia is the commonest visual disorder of childhood in Western societies, affecting, predomin... more Amblyopia is the commonest visual disorder of childhood in Western societies, affecting, predominantly, spatial visual function. Treatment typically requires a period of refractive correction ('optical treatment') followed by occlusion: covering the nonamblyopic eye with a fabric patch for varying daily durations. Recent studies have provided insight into the optimal amount of patching ('dose'), leading to the adoption of standardized dosing strategies, which, though an advance on previous ad-hoc regimens, take little account of individual patient characteristics. This trial compares the effectiveness of a standardized dosing strategy (that is, a fixed daily occlusion dose based on disease severity) with a personalized dosing strategy (derived from known treatment dose-response functions), in which an initially prescribed occlusion dose is modulated, in a systematic manner, dependent on treatment compliance. A total of 120 children aged between 3 and 8 years of age d...

Research paper thumbnail of Future directions in the treatment of amblyopia

Research paper thumbnail of Compliance monitoring in amblyopia therapy

Lancet, Jan 26, 1994

SiR-Amblyopia is the commonest visual defect of childhood and early identification is vital if tr... more SiR-Amblyopia is the commonest visual defect of childhood and early identification is vital if treatment is to be successful. Consequently, by the age of 5 or 6 most of the 500 000 or so annual UK school entrants have been screened for this defect at least twice.' Occlusion therapy of the better eye has been the mainstay of treatment for 250 years, with regimens ranging from a few minutes a day to all waking hours. So far compliance has defied accurate monitoring without which there can be no rigorous treatment evaluation.2 The efficacy of occlusion therapy therefore remains uncertain with reported success rates of 30-92%,3 as does its dose-effect relation. We report preliminary data of objective compliance monitoring with a recently developed occlusion dose monitor (ODM) in amblyopia therapy.

Research paper thumbnail of Sleep disturbance and blindness

Research paper thumbnail of Intermediate spatial frequency letter contrast sensitivity: its relation to visual resolution before and during amblyopia treatment

Ophthalmic and Physiological Optics, 2006

We examined the loss of letter contrast sensitivity (LCS) measured using the Pelli-Robson chart, ... more We examined the loss of letter contrast sensitivity (LCS) measured using the Pelli-Robson chart, and the extent to which any such loss was modulated by spectacle wear and occlusion therapy in children participating in an amblyopia treatment trial. Their initial mean interocular difference in logMAR acuity was approximately three times that of their LCS (0.45 vs 0.14 log units). Log LCS was weakly though significantly correlated with logMAR visual acuity (VA) for all VAs better than 0.90 (r ¼ )0.19, 95% CI: )0.28 to )0.10) whereas for all VAs of 0.90 or poorer, log LCS was markedly and significantly correlated with VA (r ¼ )0.72, 95% CI: )0.83 to )0.53). LCS in those children with a ‡0.1 log unit interocular difference on this test improved commensurately with VA during treatment. We conjecture that the spatial visual loss in all but the most severe amblyopes occurs in an area of resolution and contrast space that lies beyond that sampled by the Pelli-Robson chart.

Research paper thumbnail of Remediation of refractive amblyopia by optical correction alone

Ophthalmic and Physiological Optics, 2002

Amblyopia--the commonest vision abnormality of childhood--is characterized by a loss of visual ac... more Amblyopia--the commonest vision abnormality of childhood--is characterized by a loss of visual acuity usually of one eye only. Treatment aims to promote function of the amblyopic eye and does this by restricting, usually through occlusion, the competitive advantage of the fellow eye. Recent experimental evidence demonstrates that the recovery of vision following early deprivation is facilitated by increasing visually evoked activity. An analogous approach in humans is to minimise image blur by correcting refractive error prior to treatment--a practice which may account for the poorly quantified improvements in visual acuity sometimes attributed to 'spectacle adaptation'. Here we describe clinically significant gains in visual acuity obtained over a period of 4-24 weeks in a group of amblyopic children arising solely in response to the correction of refractive error. Consequences for the clinical management of refractive amblyopia are discussed.

Research paper thumbnail of Reliability of the Cambridge Low Contrast Gratings

Ophthalmic and Physiological Optics, 1994

examined the reliability of the Cambridge Low Contrast Gratings over four sessions at intervals o... more examined the reliability of the Cambridge Low Contrast Gratings over four sessions at intervals of 1 hour, 1 day and 1 week. The 95% ranges of difference scores were found to be ± 10.3 and ± 10.5 test units for left and right eyes respectively. These reliability estimates span almost one-quarter of the test's dynamic range and one-third of the subjects' performance range. Practice effects were not found to be significant. Though previous reports have emphasized the usefulness of the Cambridge Gratings in screening for eye disease, caution is advised when interpreting changes that occur over time. \

Research paper thumbnail of Measurements of Pupillary Responses to Light in Term and Preterm Infants

Neuro-Ophthalmology, 2005

ABSTRACT Dynamic pupillometry of very young subjects presents a significant practical and technol... more ABSTRACT Dynamic pupillometry of very young subjects presents a significant practical and technological challenge. In consequence, there have been limited reports on the dynamics of the pupil light reflex (PLR) in infants and none on those born prematurely. The purpose of this study was to develop an infrared (IR) pupillometer specifically for use in situ (i.e., within cot or isolette) and to quantify the latency and amplitude of infants' pupillary responses to light as a function of postmenstrual age. Recordings of 2.5-s duration began 500 ms before the presentation of a 500-ms step luminance change (18–39 cd · m− 2) of an LCD display positioned 30 cm in front of a supine infant. Pupillary responses were obtained from 10 infants: five were born within 20 days of their expected due date and recordings were undertaken within three days of birth. The remaining five infants had been born preterm and their postmenstrual age (PMA) was still less than 280 days (full term) at the time of the recording. Pre-response pupil diameter increased monotonically with infant PMA. PLR amplitude and latency decreased with increasing PMA. Conventional dynamic IR video-pupillometry, albeit with a number of situation-specific adaptations, permits the measurement of pupillary responses to light in newborn term and preterm infants within a clinical setting. The characteristics of the early maturation of the pupillometer system can be quantified in this manner.

Research paper thumbnail of Ophthalmic surgical training

JRSM, 2004

Richard Motley's response assumes that, like supply, the demand for surgery is finite. This is cl... more Richard Motley's response assumes that, like supply, the demand for surgery is finite. This is clearly not the case. Despite a large increase in the number of surgeons, and a commensurate increase in the number of operations carried out in England over the past three decades, waiting lists have altered little. The phenomenon of the amount of supply being a key determinant of the level of demand can also be seen in comparisons with the US, where much higher provision of services results in surgical rates approximately twice those in the UK. This is why current 309

Research paper thumbnail of The effect of amblyopia treatment on stereoacuity

Journal of American Association for Pediatric Ophthalmology and Strabismus, 2013

To explore how stereoacuity changes in patients while they are being treated for amblyopia. The M... more To explore how stereoacuity changes in patients while they are being treated for amblyopia. The Monitored Occlusion Treatment for Amblyopia Study (MOTAS) comprised 3 distinct phases. In the first phase, baseline, assessments of visual function were made to confirm the initial visual and binocular visual deficit. The second phase, refractive adaptation, now commonly termed "optical treatment," was an 18-week period of spectacle wear with measurements of logMAR visual acuity and stereoacuity with the Frisby test at weeks 0, 6, 12, and 18. In the third phase, occlusion, participants were prescribed 6 hours of patching per day. A total of 85 children were enrolled (mean age, 5.1 ± 1.5 years). In 21 children amblyopia was associated with anisometropia; in 29, with strabismus; and in 35, with both. At study entry, poor stereoacuity was associated with poor visual acuity (P < 0.001) in the amblyopic eye and greater angle of strabismus (P < 0.001). Of 66 participants, 25 (38%) who received refractive adaptation and 19 (29%) who received occlusion improved by at least one octave in stereoacuity, exceeding test-retest variability. Overall, 38 (45%) improved one or more octaves across both treatment phases. Unmeasureable stereoacuity was observed in 56 participants (66%) at study entry and in 37 (43%) at study exit. Stereoacuity improved for almost one half of the study participants. Improvement was observed in both treatment phases. Factors associated with poor or nil stereoacuity at study entry and exit were poor visual acuity of the amblyopic eye and large-angle strabismus.

Research paper thumbnail of Compliance With Occlusion Therapy for Childhood Amblyopia

Investigative Ophthalmology & Visual Science, 2013

Explore compliance with occlusion treatment of amblyopia in the Monitored and Randomized Occlusio... more Explore compliance with occlusion treatment of amblyopia in the Monitored and Randomized Occlusion Treatment of Amblyopia Studies (MOTAS and ROTAS), using objective monitoring. Both studies had a three-phase protocol: initial assessment, refractive adaptation, and occlusion. In the occlusion phase, participants were instructed to dose for 6 hours/day (MOTAS) or randomized to 6 or 12 hour/day (ROTAS). Dose was monitored continuously using an occlusion dose monitor (ODM). One hundred and fifty-two patients (71 male, 81 female; 122 Caucasian, 30 non-Caucasian) of mean ± SD age 68 ± 18 months participated. Amblyopia was defined as an interocular acuity difference of at least 0.1 logMAR and was associated with anisometropia in 50, strabismus in 44, and both (mixed) in 58. Median duration of occlusion was 99 days (interquartile range 72 days). Mean compliance was 44%, mean proportion of days with no patch worn was 42%. Compliance was lower (39%) on weekends compared with weekdays (46%, P = 0.04), as was the likelihood of dosing at all (52% vs. 60%, P = 0.028). Compliance was lower when attendance was less frequent (P < 0.001) and with prolonged treatment duration (P < 0.001). Age, sex, amblyopia type, and severity were not associated with compliance. Mixture modeling suggested three subpopulations of patch day doses: less than 30 minutes; doses that achieve 30% to 80% compliance; and doses that achieve around 100% compliance. This study shows that compliance with patching treatment averages less than 50% and is influenced by several factors. A greater understanding of these influences should improve treatment outcome. (ClinicalTrials.gov number, NCT00274664).

Research paper thumbnail of Modeling Dose-Response in Amblyopia: Toward a Child-Specific Treatment Plan

Investigative Ophthalmology & Visual Science, 2007

This article describes an empirically derived mathematical model of the treatment dose-response o... more This article describes an empirically derived mathematical model of the treatment dose-response of occlusion therapy for amblyopia based on outcome data obtained from the Monitored Occlusion Treatment for Amblyopia Study (MOTAS). The MOTAS protocol comprised three discrete phases: baseline, refractive adaptation, and occlusion. Only data from the occlusion phase were used in this dose-response model. Seventy-two participants, 3 to 8 years of age, mean +/- SD age 5.2 +/- 1.4 years (anisometropia [n = 18]); strabismus [n = 22]); both anisometropia and strabismus [n = 32]) completed the occlusion phase. All participants were prescribed 6-h/d patching, which was objectively monitored by an occlusion dose monitor (ODM). Simple normal linear regression modeling of the data on an interval-by-interval basis (interval between clinic visits) indicates that increasing cumulative dose within interval (hours) yields an increase in visual acuity (R2 = 0.918; 684 data points). Most of the children achieved their best visual acuity with 150 to 250 hours' cumulative dose. Specific patient characteristics (especially age) modify the steepness of this function. For example, a 0.20-logMAR (2-line logarithm of the minimum angle of resolution) gain in visual acuity requires a cumulative dose of 170 hours for children at age 48 months and 236 hours at age 72 months. Mathematical modeling of amblyopia therapy is a novel approach that elucidates the kinetics of the therapeutic response in humans. This response is age-influenced so that older children require a greater dose to achieve the same outcome--evidence of altered plasticity of the visual system. Fine-tuning the dose-response in amblyopia therapy will facilitate the development of child-specific, evidence-based treatment plans.

Research paper thumbnail of Effectiveness of occlusion therapy in ametropic amblyopia

The British Journal of Ophthalmology, Jul 1, 1998

To examine the relative contributions of non-specific (for example, spectacle correction) and spe... more To examine the relative contributions of non-specific (for example, spectacle correction) and specific (that is, occlusion therapy) treatment effects on children with ametropic amblyopia. To assess the importance and practicality of objectively confirming the prescribed occlusion dose. Subjects were entered into a two phase trial. In the first ('pretreatment') subjects were provided with spectacle correction and underwent repeat visual acuity (VA) and contrast sensitivity (CS) testing until acuity in their amblyopic eye had stabilised. Subjects then progressed to the second phase ('treatment') in which they underwent direct, unilateral occlusion for 1 hour per day for 4 weeks. Patching was objectively monitored using an occlusion dose monitor. Eight subjects completed the trial, all but one of whom achieved > 80% concordance with the occlusion regimen. Within the pretreatment phase, mean amblyopic eye VA improved by 0.19 log units (p = 0.008) while mean CS gained 0.09 log units (p = 0.01). An identical improvement in mean VA was recorded in the fellow eyes (p = 0.03) while mean CS gained 0.11 log units (p = 0.02). Within the treatment phase, mean VA further improved (0.12 log units, p = 0.009) although this gain had halved by the end of treatment and was no longer statistically significant (p = 0.09). Visual performance improved significantly during pretreatment whereas further gains seen during occlusion were not sustained. Evaluation of occlusion regimens must take into consideration the potentially confounding influence of 'pretreatment effects' and the necessity to confirm objectively the occlusion dose a child receives.

Research paper thumbnail of Whole-body vibration and visual performance: an examination of spatial filtering and time-dependency

Ergonomics, May 1, 1987

Two experiments have examined the effects of whole-body vibration on visual performance. The firs... more Two experiments have examined the effects of whole-body vibration on visual performance. The first experiment concerned alphanumeric reading performance and contrast thresholds for gratings subtending 7-5, 10 and 12-5 cycles per degree (c deg). Seated subjects were exposed to vertical sinusoidal whole-body vibration (4 Hz, 2-5 ms r.m.s.). Greatest reading errors occurred with characters exhibiting a high spatial complexity in

Research paper thumbnail of Ophthalmic surgical training

Journal of the Royal Society of Medicine, Jun 1, 2004

Research paper thumbnail of Sinusoidal and random whole-body vibration: comparative effects on visual performance

Aviation Space and Environmental Medicine

An experimental comparison of the effect of whole-body sinusoidal and one-third octave-band rando... more An experimental comparison of the effect of whole-body sinusoidal and one-third octave-band random vibration on the performance of a display reading task is described. The findings indicate that one-third octave-band random vibration has significantly less effect on performance. Subsequent measurements of rotational head motion demonstrated that this finding may be due to differences in the velocity probability density distributions produced by the different motions. Subjects also performed the visual task during exposure to several broad-band random motions. Predicted error values were obtained by averaging the frequency weighted time histories of these motions. It was found that both R.M.S. and R.M.Q. averaging procedures applied to the broad-band frequency weighted time histories gave accurate error predictions when compared with the measured error scores. Practical implications of the experimental findings and recommendations for future research are discussed.

Research paper thumbnail of Sleep Disturbances among Persons Who Are Visually Impaired: Survey of Dog Guide Users

Journal of visual impairment & blindness

ABSTRACT

Research paper thumbnail of Delayed visual maturation: pupillary responses implicate subcortical and cortical visual systems

Developmental Medicine & Child Neurology

Vision in very early infancy is probably subserved by subcortical pathways, with many cortical pr... more Vision in very early infancy is probably subserved by subcortical pathways, with many cortical processes only fully emerging by 3 months of age. The improvement of vision in delayed visual maturation (DVM) occurs around this time, and this has given rise to the suggestion that the condition may have a subcortical basis that resolves with the appearance of cortical function. To explore further the role of cortical and subcortical visual systems in DVM we studied the visual development in identical twins, one of whom had type 1b DVM. Two non-invasive methods of investigating visual pathway function were employed: the acuity card procedure (a behavioural response) and luminance and grating pupillometry. While the former reflects both subcortical and cortical function and can be detected at birth, pupil responses to gratings reflect cortical activity alone and normally become measurable at 1 month of age. Development of both behavioural and pupillary responses was delayed in DVM, indica...

Research paper thumbnail of Semiautomated computer analysis of vessel growth in preterm infants without and with ROP

British Journal of Ophthalmology

To measure characteristics of the retinal blood vessels close to the optic disc in full term and ... more To measure characteristics of the retinal blood vessels close to the optic disc in full term and preterm infants, with and without retinopathy of prematurity (ROP), using digital imaging. To determine whether these measures are indicative of the presence or severity of ROP in the retinal periphery. 52 digital fundus images from 42 babies were analysed with a semiautomated analysis program developed at Imperial College London. Analysis was limited to the principal temporal vessels close to the optic disc: recording venular diameter and arteriolar diameter and tortuosity. Each result was categorised by the gestational age of the infant ("very premature" 24-27 weeks, "moderately premature" 28-31 weeks, and "near term" > or =32 weeks) and by the highest stage of ROP present ("no ROP," "mild ROP" stage 1 or 2, and "severe ROP" stage 3). Arteriolar tortuosity was found to vary significantly (Kruskal-Wallis p=0.002) with ROP se...

Research paper thumbnail of Ch 55. The applied physiology of the eye and visual system

Research paper thumbnail of Personalized versus standardized dosing strategies for the treatment of childhood amblyopia: study protocol for a randomized controlled trial

Trials, Jan 25, 2015

Amblyopia is the commonest visual disorder of childhood in Western societies, affecting, predomin... more Amblyopia is the commonest visual disorder of childhood in Western societies, affecting, predominantly, spatial visual function. Treatment typically requires a period of refractive correction ('optical treatment') followed by occlusion: covering the nonamblyopic eye with a fabric patch for varying daily durations. Recent studies have provided insight into the optimal amount of patching ('dose'), leading to the adoption of standardized dosing strategies, which, though an advance on previous ad-hoc regimens, take little account of individual patient characteristics. This trial compares the effectiveness of a standardized dosing strategy (that is, a fixed daily occlusion dose based on disease severity) with a personalized dosing strategy (derived from known treatment dose-response functions), in which an initially prescribed occlusion dose is modulated, in a systematic manner, dependent on treatment compliance. A total of 120 children aged between 3 and 8 years of age d...

Research paper thumbnail of Future directions in the treatment of amblyopia

Research paper thumbnail of Compliance monitoring in amblyopia therapy

Lancet, Jan 26, 1994

SiR-Amblyopia is the commonest visual defect of childhood and early identification is vital if tr... more SiR-Amblyopia is the commonest visual defect of childhood and early identification is vital if treatment is to be successful. Consequently, by the age of 5 or 6 most of the 500 000 or so annual UK school entrants have been screened for this defect at least twice.' Occlusion therapy of the better eye has been the mainstay of treatment for 250 years, with regimens ranging from a few minutes a day to all waking hours. So far compliance has defied accurate monitoring without which there can be no rigorous treatment evaluation.2 The efficacy of occlusion therapy therefore remains uncertain with reported success rates of 30-92%,3 as does its dose-effect relation. We report preliminary data of objective compliance monitoring with a recently developed occlusion dose monitor (ODM) in amblyopia therapy.

Research paper thumbnail of Sleep disturbance and blindness

Research paper thumbnail of Intermediate spatial frequency letter contrast sensitivity: its relation to visual resolution before and during amblyopia treatment

Ophthalmic and Physiological Optics, 2006

We examined the loss of letter contrast sensitivity (LCS) measured using the Pelli-Robson chart, ... more We examined the loss of letter contrast sensitivity (LCS) measured using the Pelli-Robson chart, and the extent to which any such loss was modulated by spectacle wear and occlusion therapy in children participating in an amblyopia treatment trial. Their initial mean interocular difference in logMAR acuity was approximately three times that of their LCS (0.45 vs 0.14 log units). Log LCS was weakly though significantly correlated with logMAR visual acuity (VA) for all VAs better than 0.90 (r ¼ )0.19, 95% CI: )0.28 to )0.10) whereas for all VAs of 0.90 or poorer, log LCS was markedly and significantly correlated with VA (r ¼ )0.72, 95% CI: )0.83 to )0.53). LCS in those children with a ‡0.1 log unit interocular difference on this test improved commensurately with VA during treatment. We conjecture that the spatial visual loss in all but the most severe amblyopes occurs in an area of resolution and contrast space that lies beyond that sampled by the Pelli-Robson chart.

Research paper thumbnail of Remediation of refractive amblyopia by optical correction alone

Ophthalmic and Physiological Optics, 2002

Amblyopia--the commonest vision abnormality of childhood--is characterized by a loss of visual ac... more Amblyopia--the commonest vision abnormality of childhood--is characterized by a loss of visual acuity usually of one eye only. Treatment aims to promote function of the amblyopic eye and does this by restricting, usually through occlusion, the competitive advantage of the fellow eye. Recent experimental evidence demonstrates that the recovery of vision following early deprivation is facilitated by increasing visually evoked activity. An analogous approach in humans is to minimise image blur by correcting refractive error prior to treatment--a practice which may account for the poorly quantified improvements in visual acuity sometimes attributed to 'spectacle adaptation'. Here we describe clinically significant gains in visual acuity obtained over a period of 4-24 weeks in a group of amblyopic children arising solely in response to the correction of refractive error. Consequences for the clinical management of refractive amblyopia are discussed.

Research paper thumbnail of Reliability of the Cambridge Low Contrast Gratings

Ophthalmic and Physiological Optics, 1994

examined the reliability of the Cambridge Low Contrast Gratings over four sessions at intervals o... more examined the reliability of the Cambridge Low Contrast Gratings over four sessions at intervals of 1 hour, 1 day and 1 week. The 95% ranges of difference scores were found to be ± 10.3 and ± 10.5 test units for left and right eyes respectively. These reliability estimates span almost one-quarter of the test's dynamic range and one-third of the subjects' performance range. Practice effects were not found to be significant. Though previous reports have emphasized the usefulness of the Cambridge Gratings in screening for eye disease, caution is advised when interpreting changes that occur over time. \

Research paper thumbnail of Measurements of Pupillary Responses to Light in Term and Preterm Infants

Neuro-Ophthalmology, 2005

ABSTRACT Dynamic pupillometry of very young subjects presents a significant practical and technol... more ABSTRACT Dynamic pupillometry of very young subjects presents a significant practical and technological challenge. In consequence, there have been limited reports on the dynamics of the pupil light reflex (PLR) in infants and none on those born prematurely. The purpose of this study was to develop an infrared (IR) pupillometer specifically for use in situ (i.e., within cot or isolette) and to quantify the latency and amplitude of infants' pupillary responses to light as a function of postmenstrual age. Recordings of 2.5-s duration began 500 ms before the presentation of a 500-ms step luminance change (18–39 cd · m− 2) of an LCD display positioned 30 cm in front of a supine infant. Pupillary responses were obtained from 10 infants: five were born within 20 days of their expected due date and recordings were undertaken within three days of birth. The remaining five infants had been born preterm and their postmenstrual age (PMA) was still less than 280 days (full term) at the time of the recording. Pre-response pupil diameter increased monotonically with infant PMA. PLR amplitude and latency decreased with increasing PMA. Conventional dynamic IR video-pupillometry, albeit with a number of situation-specific adaptations, permits the measurement of pupillary responses to light in newborn term and preterm infants within a clinical setting. The characteristics of the early maturation of the pupillometer system can be quantified in this manner.

Research paper thumbnail of Ophthalmic surgical training

JRSM, 2004

Richard Motley's response assumes that, like supply, the demand for surgery is finite. This is cl... more Richard Motley's response assumes that, like supply, the demand for surgery is finite. This is clearly not the case. Despite a large increase in the number of surgeons, and a commensurate increase in the number of operations carried out in England over the past three decades, waiting lists have altered little. The phenomenon of the amount of supply being a key determinant of the level of demand can also be seen in comparisons with the US, where much higher provision of services results in surgical rates approximately twice those in the UK. This is why current 309

Research paper thumbnail of The effect of amblyopia treatment on stereoacuity

Journal of American Association for Pediatric Ophthalmology and Strabismus, 2013

To explore how stereoacuity changes in patients while they are being treated for amblyopia. The M... more To explore how stereoacuity changes in patients while they are being treated for amblyopia. The Monitored Occlusion Treatment for Amblyopia Study (MOTAS) comprised 3 distinct phases. In the first phase, baseline, assessments of visual function were made to confirm the initial visual and binocular visual deficit. The second phase, refractive adaptation, now commonly termed "optical treatment," was an 18-week period of spectacle wear with measurements of logMAR visual acuity and stereoacuity with the Frisby test at weeks 0, 6, 12, and 18. In the third phase, occlusion, participants were prescribed 6 hours of patching per day. A total of 85 children were enrolled (mean age, 5.1 ± 1.5 years). In 21 children amblyopia was associated with anisometropia; in 29, with strabismus; and in 35, with both. At study entry, poor stereoacuity was associated with poor visual acuity (P < 0.001) in the amblyopic eye and greater angle of strabismus (P < 0.001). Of 66 participants, 25 (38%) who received refractive adaptation and 19 (29%) who received occlusion improved by at least one octave in stereoacuity, exceeding test-retest variability. Overall, 38 (45%) improved one or more octaves across both treatment phases. Unmeasureable stereoacuity was observed in 56 participants (66%) at study entry and in 37 (43%) at study exit. Stereoacuity improved for almost one half of the study participants. Improvement was observed in both treatment phases. Factors associated with poor or nil stereoacuity at study entry and exit were poor visual acuity of the amblyopic eye and large-angle strabismus.

Research paper thumbnail of Compliance With Occlusion Therapy for Childhood Amblyopia

Investigative Ophthalmology & Visual Science, 2013

Explore compliance with occlusion treatment of amblyopia in the Monitored and Randomized Occlusio... more Explore compliance with occlusion treatment of amblyopia in the Monitored and Randomized Occlusion Treatment of Amblyopia Studies (MOTAS and ROTAS), using objective monitoring. Both studies had a three-phase protocol: initial assessment, refractive adaptation, and occlusion. In the occlusion phase, participants were instructed to dose for 6 hours/day (MOTAS) or randomized to 6 or 12 hour/day (ROTAS). Dose was monitored continuously using an occlusion dose monitor (ODM). One hundred and fifty-two patients (71 male, 81 female; 122 Caucasian, 30 non-Caucasian) of mean ± SD age 68 ± 18 months participated. Amblyopia was defined as an interocular acuity difference of at least 0.1 logMAR and was associated with anisometropia in 50, strabismus in 44, and both (mixed) in 58. Median duration of occlusion was 99 days (interquartile range 72 days). Mean compliance was 44%, mean proportion of days with no patch worn was 42%. Compliance was lower (39%) on weekends compared with weekdays (46%, P = 0.04), as was the likelihood of dosing at all (52% vs. 60%, P = 0.028). Compliance was lower when attendance was less frequent (P < 0.001) and with prolonged treatment duration (P < 0.001). Age, sex, amblyopia type, and severity were not associated with compliance. Mixture modeling suggested three subpopulations of patch day doses: less than 30 minutes; doses that achieve 30% to 80% compliance; and doses that achieve around 100% compliance. This study shows that compliance with patching treatment averages less than 50% and is influenced by several factors. A greater understanding of these influences should improve treatment outcome. (ClinicalTrials.gov number, NCT00274664).

Research paper thumbnail of Modeling Dose-Response in Amblyopia: Toward a Child-Specific Treatment Plan

Investigative Ophthalmology & Visual Science, 2007

This article describes an empirically derived mathematical model of the treatment dose-response o... more This article describes an empirically derived mathematical model of the treatment dose-response of occlusion therapy for amblyopia based on outcome data obtained from the Monitored Occlusion Treatment for Amblyopia Study (MOTAS). The MOTAS protocol comprised three discrete phases: baseline, refractive adaptation, and occlusion. Only data from the occlusion phase were used in this dose-response model. Seventy-two participants, 3 to 8 years of age, mean +/- SD age 5.2 +/- 1.4 years (anisometropia [n = 18]); strabismus [n = 22]); both anisometropia and strabismus [n = 32]) completed the occlusion phase. All participants were prescribed 6-h/d patching, which was objectively monitored by an occlusion dose monitor (ODM). Simple normal linear regression modeling of the data on an interval-by-interval basis (interval between clinic visits) indicates that increasing cumulative dose within interval (hours) yields an increase in visual acuity (R2 = 0.918; 684 data points). Most of the children achieved their best visual acuity with 150 to 250 hours' cumulative dose. Specific patient characteristics (especially age) modify the steepness of this function. For example, a 0.20-logMAR (2-line logarithm of the minimum angle of resolution) gain in visual acuity requires a cumulative dose of 170 hours for children at age 48 months and 236 hours at age 72 months. Mathematical modeling of amblyopia therapy is a novel approach that elucidates the kinetics of the therapeutic response in humans. This response is age-influenced so that older children require a greater dose to achieve the same outcome--evidence of altered plasticity of the visual system. Fine-tuning the dose-response in amblyopia therapy will facilitate the development of child-specific, evidence-based treatment plans.