Biomedical subjects

Merrick J Moseley

Publications and source records attributed to Merrick J Moseley.

11 recordsLinked to original sources

PubMed2006

Factors affecting the stability of visual function following cessation of occlusion therapy for amblyopia.

AIM: To identify factors that predict which children with amblyopia are at greatest risk of regression of visual acuity (VA) following the cessation of occlusion therapy. METHOD: A retrospective analysis was performed of 182 children (mean age at cessation of treatment; 5.9+/-1.6 years) who had undergone occlusion therapy for unilateral amblyopia, and had been followed up at least once within 15 months of cessation. Statistical analysis was used to identify whether change in VA following treatment cessation had any association with various factors, including the child's age, type of amblyopia, degree of anisometropia, initial severity of amblyopia, binocular vision status, length and dose of occlusion therapy, and VA response to treatment. RESULTS: At 1 year, follow-up from treatment cessation, children with "mixed" amblyopia (both anisometropia and strabismus) demonstrated significantly (p=0.03) greater deterioration in VA (0.11+/-0.11 log units) than children with only anisometropia (0.02+/-0.08 log units) or only strabismus (0.05+/-0.10 log units). However, none of the other factors investigated were found to be significant predictors. CONCLUSION: This study supports previous research that it is possible to identify those children most at risk of deterioration in VA following cessation of occlusion therapy. The presence of mixed amblyopia was the only risk factor identified in this study. Management of amblyopia should take this into account, with a more intensive follow-up recommended for those with both anisometropia and strabismus (mixed) amblyopia.

Amblyopia↗

PubMed2006

Intermediate spatial frequency letter contrast sensitivity: its relation to visual resolution before and during amblyopia treatment.

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 = -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 = -0.72, 95% CI: -0.83 to -0.53). LCS in those children with a > or =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.

Adaptation, Physiological↗

PubMed2006

Comparison of logMAR ETDRS chart and a new computerised staircased procedure for assessment of the visual acuity of children.

The validity and repeatability of visual acuity measures are particularly important in the detection and monitoring of childhood visual anomalies such as amblyopia. The repeatability and sensitivity of a new computerised visual acuity test, 'Staircased Procedure' is compared with the now gold standard visual acuity test, the early treatment of diabetic retinopathy study (ETDRS). Twenty-seven visually normal children (mean age: 6.7 +/- 1.1 years) and 27 children with amblyopia (mean age: 6.1 +/- 0.7 years) were tested with the ETDRS and Staircased Procedure. A retest was administered 4-5 weeks later and 30 min later for the visually normal and the amblyopic children, respectively. The staircased procedure produced significantly better visual acuity than the ETDRS for visually normal and amblyopic children. Repeatability was similar for both tests (ETDRS: 0.11 log units; staircased procedure: 0.13 log units). In conclusion, the Staircased Procedure was an acceptable test with high repeatability and validity.

Amblyopia↗

PubMed2006

Optic disk size and optic disk-to-fovea distance in preterm and full-term infants.

PURPOSE: Few studies have assessed optic disk and retinal morphology in infants. Here the optic disk and optic disk-to-fovea distance were measured in preterm and full-term infants in vivo. METHODS: Optic disk (OD) dimensions and the center-to-center distance between the OD and the macula were measured using digital imaging in infants undergoing routine ophthalmic examinations. Postmenstrual age of the mother at the time of examination ranged from 32 to 50 weeks. From each image, the OD-to-fovea distance (ODF) and the OD height (ODH) and OD width (ODW) were measured. RESULTS: In 51 retinal images from 51 infants, mean +/- SD values obtained were 4.4 +/- 0.4 mm (ODF), 1.41 +/- 0.1 9 mm (ODH), and 1.05 +/- 0.13 mm (ODW). These dimensions did not change significantly over the age range studied. The mean value for the ratio between ODF and mean OD diameter (ODF/DD) was 3.76. CONCLUSIONS: Results of this in vivo study suggest that though the optic nerve head diameter increases by more than 50%, only limited growth occurs at the highly organized area of the posterior pole from birth to adulthood. This study discusses the finding of a large-angle kappa in infants and the use of a disk macula/disk diameter ratio in the diagnosis of optic nerve hypoplasia.

Birth Weight↗

PubMed2005

Treatment of unilateral amblyopia: factors influencing visual outcome.

PURPOSE: To identify factors that influence the outcome of treatment for unilateral amblyopia, as a part of the Monitored Occlusion Treatment of Amblyopia Study (MOTAS). METHODS: This was an intervention study consisting of three nonoverlapping phases: "Baseline", "refractive adaptation" (18 weeks of full-time spectacle wear), and "occlusion" (6 hours of patching per day, objectively monitored). Condition factors: type of amblyopia, age of participant, initial severity of amblyopia, fixation, and binocular vision status; treatment factors: refractive adaptation and occlusion (total dose [hours] and dose rate [hours per day]) were assessed for their influence on visual outcome. Visual outcome was expressed in three ways: logMAR (logarithm of the minimum angle of resolution) change, residual amblyopia, and proportion of the deficit corrected. RESULTS: The study included 85 participants (mean age, 5.1 +/- 1.4 years) with amblyopia associated with strabismus (n = 32) or anisometropia (n = 20) or associated with both anisometropia and strabismus (n = 33). Treatment factors: cumulative occlusion dose exceeding 50 hours, and dose rates > or =1 hour per day resulted in (P < or = 0.01) lower residual amblyopia and a greater proportion of the deficit corrected. Condition factors associated with poor outcome (high residual amblyopia) were presence of eccentric fixation, severe initial amblyopia, and no binocular vision. CONCLUSIONS: Factors influencing outcome with treatment for amblyopia are occlusion dose (the rate of delivery and cumulative dose worn), the initial severity of the amblyopia, binocular vision status, fixation of the amblyopic eye, and the age of the subject at the start of treatment.

Age Factors↗

PubMed2004

Cost-effectiveness of digital photographic screening for retinopathy of prematurity in the United Kingdom.

OBJECTIVES: To compare the cost-effectiveness of alternative methods of screening for retinopathy of prematurity (ROP) in the United Kingdom, including the existing method of indirect ophthalmoscopy by ophthalmologists and digital photographic screening by nurses. METHODS: A decision tree model was used to compare five screening modalities for the UK population of preterm babies, using a health service perspective. Data were taken from published sources, observation at a neonatal intensive care unit (NICU), and expert judgment. RESULTS: We estimated that use of standard digital cameras by nurses in NICUs would cost more than current methods (pound 371 compared with pound 321 per baby screened). However, a specialist nurse visiting units with a portable camera would be cheaper (pound 172 per baby). These estimates rely on nurses capturing and interpreting the images, with suitable training and supervision. Alternatively, nurses could capture the images then transmit them to a central unit for interpretation by ophthalmologists, although we estimate that this would be rather more expensive (pound 390 and pound 201, respectively, for NICU and visiting nurses). Sensitivity analysis was used to examine the robustness of estimates. CONCLUSIONS: It is likely that there is an opportunity to improve the efficiency of the ROP screening program. We estimate that screening by specialist nurses trained in image capture and interpretation using portable digital cameras is a cost-effective alternative to the current program of direct visualization by ophthalmologists. This option would require the development of a suitable portable machine. Direct comparative research is strongly needed to establish the accuracy of the various screening options.

Cohort Studies↗

PubMed2004

Use of pupil size and reaction to detect orbital trauma during and after surgery.

We describe how pupillary reactions, used as an index of optic nerve function, can be elicited using only one working pupil. This is to challenge the conclusion of a study that did not appreciate this physiological phenomenon and thus gave rise to erroneous conclusions that might otherwise limit the scope of pupil measurements during and after surgery. For suitable cases, non-opioid anaesthesia and further clinical development of pupillometry are suggested by us as measures to monitor optic nerve function.

Endoscopy↗

PubMed2004

Treatment dose-response in amblyopia therapy: the Monitored Occlusion Treatment of Amblyopia Study (MOTAS).

PURPOSE: Amblyopia is the commonest visual disorder of childhood. Yet the contributions of the two principal treatments (spectacle wear and occlusion) to outcome are unknown. This study was undertaken to investigate the dose-response relationship of amblyopia therapy. METHODS: The study comprised three distinct phases: baseline, in which repeat measures of visual function were undertaken to confirm the initial visual deficit; refractive adaptation: an 18-week period of spectacle wear with six weekly measurements of logarithm of the minimum angle of resolution (logMAR) visual acuity; occlusion: in which participants were prescribed 6 hours of "patching" per day. In the latter phase, occlusion was objectively monitored and logMAR visual acuity recorded at 2-week intervals until any observed gains had ceased. RESULTS: Data were obtained from 94 participants (mean age, 5.1 +/- 1.4 years) with amblyopia associated with strabismus (n = 34), anisometropia (n = 23), and both anisometropia and strabismus (n = 37). Eighty-six underwent refractive adaptation. Average concordance with patching was 48%. The relationship between logMAR visual acuity gain and total occlusion dose was monotonic and linear. Increasing dose rate beyond 2 h/d hastened the response but did not improve outcome. More than 80% of the improvement during occlusion occurred within 6 weeks. Treatment outcome was significantly better for children younger than 4 years (n = 17) than in those older than 6 years (n = 24; P = 0.0014). CONCLUSIONS: Continuous objective monitoring of the amount of patching therapy received has provided insight into the dose-response relationship of occlusion therapy for amblyopia. Patching is most effective within the first few weeks of treatment, even for those in receipt of a relatively small dose. Further studies are needed to elucidate the neural basis for the dose-response functions.

Adaptation, Physiological↗

PubMed2003

Nasotemporal asymmetry of retinopathy of prematurity.

OBJECTIVE: To quantify an apparent nasotemporal asymmetry in the location of retinopathy of prematurity with respect to the optic disc. METHODS: Twenty-four-bit color images were captured using a contact digital fundus camera during routine screening. Semiautomated measurements were undertaken to determine the distance between the optic disc and retinopathy located in the nasal and temporal regions of the retina. RESULTS: Forty-nine image pairs (17 right eye, 32 left eye) were captured from 10 infants during a period of 32 to 40 weeks postmenstrual age. For right eyes, averaged across age, the mean (SD) distance between the optic disc and temporal retinopathy was 426 (26) pixels and that between the optic disc and nasal retinopathy was 330 (26) pixels. Corresponding measurements for the left eye were 428 (30) and 332 (24) pixels. This observed asymmetry was found to be statistically significant in both left and right eyes (Mann-Whitney U test, P<.01). While the distance between the optic disc and retinopathy increased with age by 10 to 17 pixels per week, the extent of the asymmetry did not vary systematically with age. CONCLUSION: The location of retinopathy of prematurity is asymmetric along the horizontal meridian with respect to the optic disc-an observation germane to retinal vascular development, the pathogenesis of retinopathy of prematurity, and current disease classification by circular (symmetric) zones.

Gestational Age↗

PubMed2002

Remediation of refractive amblyopia by optical correction alone.

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.

Amblyopia↗

PubMed2002

Long-term ophthalmic outcome of low birth weight children with and without retinopathy of prematurity.

OBJECTIVE: A prospective study of retinopathy of prematurity (ROP) of 505 infants who weighed <1701 g at birth was undertaken in the mid-1980s. This cohort was traced at 10 to 12 years of age to determine how low birth weight alone and ROP might influence their ophthalmic outcome. METHODS: Outcome measures were 1) visual functions (visual acuity, contrast sensitivity, stereoacuity, perimetry, and color vision), 2) presence of strabismus, and 3), measurements of eye size and the dimensions of its components including refractive state. A total of 169 11-year-olds who were born at term were recruited as control subjects and examined under the same conditions. RESULTS: A total of 448 of the original cohort were traced, and 254 consented to a further examination. Compared with the control group, the follow-up cohort differed significantly with reduced visual functions and increased incidence of both myopia and strabismus. Compared with published data, eye size was smaller in the low birth weight cohort. To summarize the ophthalmic data, we defined ophthalmic morbidity as visual acuity below 0.0 log units or the presence of strabismus, myopia, color vision defect, or visual field defect. The rate of ophthalmic morbidity was 50.8% (n = 129/254) in the study cohort compared with 19.5% (n = 33/169) in the control group. The highest rate of ophthalmic morbidity was associated with severe ROP (stages 3/4), although those with no ROP had a less favorable outcome than the control group. CONCLUSION: This study shows that low birth weight children are at increased risk of visual impairments compared with children who are born at full term. Visual impairments are associated with low birth weight per se and severe ROP. Regressed mild ROP is only a risk factor for strabismus. The functional significance of these deficits is largely unknown.

Case-Control Studies↗