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Biomedical subjects

G N Dutton

Publications and source records attributed to G N Dutton.

At least 19 recordsLinked to original sources
PubMed1996

Cognitive visual dysfunction in a child with cerebral damage.

Visual impairment as a sequel to cortical damage can be associated with complex disorders in cognitive visual function. Such dysfunction can be difficult to diagnose with certainty, particularly in children, owing to the child's problems of awareness and communication. The authors describe the case of a 13-year-old girl whose cerebral damage is apparently accompanied by complex cognitive visual disorders. Though she has a good binocular visual acuity, she cannot see rapidly moving objects. She has difficulties with orientation, recognising faces and cognitive depth perception. Despite an absence of detailed psychometric testing, a clinical diagnostic approach such as that used in this case, based on a CT scan and careful history-taking and observation, may be helpful in planning educational strategies.

Adolescent↗
PubMed1995

A comparison of colour Doppler imaging of orbital vessels and other methods of blood flow assessment.

BACKGROUND: Comparison of the haemodynamic measurements obtained by colour Doppler imaging and other methods of ocular blood flow measurements was desired. METHODS: The blood velocity findings from colour Doppler imaging of patients with central retinal vein occlusion were compared to the results of fluorescein video-angiography, continuous tonography and ophthalmodynamometry. RESULTS: Patients with low or undetectable blood velocities in the central retinal vein had longer retinal dye transit times on fluorescein video-angiography. Tonography showed a positive correlation with the velocities in the ophthalmic artery, but ophthalmodynamometry showed a negative correlation with these velocities. CONCLUSION: The relationships between the blood velocities in orbital vessels and other blood flow measurements emphasise that there is a complex interaction of the blood flow parameters. Care must therefore be taken when interpreting the results of studies.

Aged↗
PubMed1995

Quantitative assessment of the blue-light hazard during indirect ophthalmoscopy and the increase in the "safe" operating period achieved using a yellow lens.

PURPOSE: The indirect ophthalmoscope presents a blue-light hazard with the potential for causing photochemical injury to the retina. In this study, this hazard was assessed with respect to the threshold limit values (TLVs) recently adopted by the American Conference of Governmental Industrial Hygienists. METHOD: Spectral radiometric measurements were made from a standard indirect ophthalmoscope headset used in conjunction with either a clear or a yellow lens. The results were weighted spectrally with the published blue-light hazard function. RESULTS: When the clear lens was used, the TLV was exceeded after approximately 2.5 minutes. The yellow lens filtered out the more hazardous blue wavelengths of light and this increased the "safe" operating period by a factor of approximately 20. CONCLUSION: In clinical practice, with a clear lens, the TLV could be exceeded easily if the patient is subjected to prolonged or repeated examination because the blue-light hazard is additive in a linear manner for periods as long as 3 hours with a potential for a cumulative effect over longer periods. Furthermore, some ophthalmic patients, such as those with aphakia, are less tolerant of blue-light than healthy subjects. In the interests of patient safety, it is recommended that yellow lenses are considered for use for routine indirect ophthalmoscopy.

Equipment Safety↗
PubMed1995

Comparison of visual assessment tests in multiply handicapped children.

The aims of this study were to compare acuity estimates achieved with visual evoked potential (VEP) and acuity card techniques and to examine the success rates of each test in a group of multiply handicapped children. Subjects were 52 children (3-183 months) with multiple handicaps associated with prematurity (n = 17), congenital anomalies (n = 16), hypoxic insult (n = 10) and other disorders (n = 9). Success rates for completing the tests were: VEP 88% and acuity cards 85% (Keeler or Cardiff). The acuity card tests were less likely to be successfully completed in the severely disabled (p < 0.05) and in those children with nystagmus (p < 0.05). When both acuity cards were successful, results agreed to within +/- 1.75 octaves. Acuity card thresholds were significantly correlated with VEP thresholds (p < 0.02), but thresholds achieved with VEPs were better in children with poor vision.

Adolescent↗
PubMed1995

Assessment of an inner city visual screening programme for preschool children.

AIMS: The efficiency of preschool visual screening programmes to detect amblyopia is questionable. In this study such a programme in an inner city was assessed to determine its effectiveness. METHODS: The results of screening and hospital treatment of 712 patients who were considered to require referral were entered into a database for analysis. Default rates were assessed and the efficacy of treatment determined. RESULTS: The only effective screening test for the detection of amblyopia was visual acuity. A large proportion of referred patients had refractive problems only. High default rates, particularly in geographical areas of lower socioeconomic grading, severely handicapped any attempt to reduce the incidence of amblyopia. CONCLUSION: A fresh approach to the detection and care of amblyopia in the inner city community is required, perhaps by performing screening of children in their first year of attendance at school to reduce default rates. Cycloplegic refraction of children who are found to have reduced visual acuity before their referral to hospital is also recommended.

Amblyopia↗
PubMed1994

The simultaneous interocular brightness sense test. A test of optic nerve function.

OBJECTIVE: To describe and establish control data from controls for a simultaneous interocular brightness sense test in which the apparent brightness of two independently viewed light patches was compared. DESIGN: Dichoptic viewing was achieved by dissociation of right and left eyes using a septum and cross-polarization. Brightness matches were obtained by using adjustments to the illumination of the left retina while the illumination of the right retina was kept constant. OBSERVERS: Ninety-one control observers (age range, 20 to 91 years) participated in the study to provide normal brightness-matching data. RESULTS: Effects from ocular dominance, age, and long- and short-term adaptation were negligible, but the test was sensitive to anisocoria. Just noticeable differences in dichoptic brightness matching were proportional to retinal illuminance; this finding was consistent with the Weber-Fechner law. CONCLUSION: The test is quick and simple to complete and appears to offer considerable scope for the assessment of visual function when differences in the functional integrity of the optic nerves of the right and left eyes are suspected.

Adaptation, Ocular↗
PubMed1994

Simultaneous interocular brightness sense testing in ocular hypertension and glaucoma.

OBJECTIVE: To investigate the performance of the simultaneous interocular brightness sense test in patients with ocular hypertension and primary open angle glaucoma (POAG). DESIGN: Brightness matches were obtained for an age-matched control sample and for patients with ocular hypertension and POAG. In addition, for the patients with POAG, visual field defects were quantified and a risk factor count was established for those with ocular hypertension. PATIENTS: Nineteen patients with ocular hypertension, 20 patients with POAG, and 61 age-matched controls participated in the study. RESULTS: Seven patients with ocular hypertension exhibited brightness perception asymmetry outside normal limits for age-matched controls. Of these, six were at high risk of having glaucoma develop and only one of the remaining 12 was found to be at similar risk. All 20 patients with established POAG had results outside the normal limits for a test sensitivity of 100%. Three control observers had abnormal results, giving a test specificity of 95%. CONCLUSION: The simultaneous interocular brightness sense test is quick and simple to perform and is suitable for a wide age range of patients. It warrants further assessment as a means of screening for ocular hypertension and glaucoma.

Adult↗
PubMed1994

Retrobulbar haemorrhage: can blindness be prevented?

Retrobulbar haemorrhage is a rare complication following orbital trauma or surgery occurring in less than 1 per cent of cases. Early diagnosis and treatment of this complication may save the vision of the affected eye. This paper illustrates cases where diagnosis was not made and blindness resulted. We also present two cases of successful treatment due to early diagnosis.

Adult↗
PubMed1994

Impaired perception of moving objects after minor injuries to the eye and midface: the Pulfrich phenomenon.

Delayed conduction along one optic nerve can result in an incorrect appreciation of moving objects. The temporal mismatch between the two different pathways results in altered perception of the vector of a moving target and is known as 'the Pulfrich phenomenon'. This is a well-recognised handicap in patients with multiple sclerosis, but has not previously been reported as a consequence of injury. All 187 patients who presented during 1991 with reduced visual acuity as a result of midfacial injuries were examined with a pendulum. Six had the defect and five of these had symptoms. In each case the patients were disturbed by car travel, because they perceived oncoming traffic moving in a hyperbolic curve towards them. These patients have been examined in detail and given a tinted lens for the normal eye to eliminate the illusion by delaying the input from the normal side to equal that on the damaged side. We recommend that this phenomenon is sought in all patients with mid-facial injuries or with later evidence of mild traumatic optic neuropathy, particularly if they are disturbed by car travel.

Automobiles↗
PubMed1994

Subclinical operating microscope retinopathy: the use of static perimetry in its detection.

Focal retinal pathology and dysfunction as a sequel to manifest damage due to operating microscope illumination is well recognised. We wished to determine whether retinal dysfunction could be identified in the absence of clinically visible lesions. We therefore have conducted a prospective controlled study on 36 patients undergoing cataract surgery and 27 control subjects. A Wild M690 zoom operating microscope was used for each procedure. No filters were used. The Humphrey visual field equipment was employed to determine threshold retinal sensitivity at predetermined loci above and below fixation in both groups. No clinically visible retinal lesions were seen in any patient. However, post-operative investigation revealed a statistically significant depression in retinal sensitivity at points most exposed to operating microscope illumination (p < 0.05). This was most noticeable following longer total operating times and in patients with the longest time intervals between lens extraction and completion of the procedure. It is concluded that operating microscope position and centration, and the position of the eye, should be adjusted to place the image of the illuminating element away from the foveola. Also retinal illumination should be kept to a minimum, particularly after an intraocular lens has been implanted.

Aged↗
PubMed1994

Argon laser photocoagulation of fluorescein stained retina--an unrecognised hazard?

Sodium fluorescein staining of the retina following fluorescein angiography may affect the absorption characteristics of argon ion laser photocoagulation. This hypothesis was investigated by performing laser photocoagulation on control and fluorescein stained porcine retinas. The resultant damage was viewed by scanning electron microscopy. In both specimens, argon irradiation produced damage to the pigment epithelium and overlying photoreceptor layer. The control sample showed a deep cylindrical burn, indicative of internal heating, in both retina and choroid. The fluorescein stained sample showed damage consistent with thermal interaction from the surface downwards leaving the choroid relatively spared. This preliminary study demonstrates that fluorescein staining of the retina changes the absorption site of argon laser light and this subject clearly merits further investigation.

Animals↗
PubMed1994

Ophthalmic features of fourteen cases of Goodpasture's syndrome.

Juxtapapillary subretinal neovascular membranes developed in both eyes of a patient who had been treated for Goodpasture's syndrome for 4 years. These lesions caused visual impairment but were successfully treated by laser photocoagulation. Subretinal neovascularisation has not been reported before in association with Goodpasture's syndrome, but diverse ocular abnormalities have been described. It is not certain whether these lesions were caused by anti-basement-membrane auto-antibodies. The eyes of 13 other patients with Goodpasture's syndrome were examined, in order to detect other unsuspected ocular pathology. In 1 further patient, both retinae contained a few unexplained superficial retinal haemorrhages. During follow-up, the original patient developed bilateral peripheral retinoschisis. From this short series and from cases previously described, we conclude that sight-threatening ocular abnormalities are rare in Goodpasture's syndrome. It is, however, particularly important to be aware of the possibility of treatable eye disease in Goodpasture's syndrome, since the introduction of effective treatment with immunosuppression and plasmapheresis has made long-term survival likely.

Adolescent↗