Stuart Parks

Secondary retinal changes associated with choroidal naevi and melanomas documented by optical coherence tomography

Aims: To establish the characteristics of secondary retinal changes associated with the presence of choroidal melanomas and choroidal naevi as documented by optical coherence tomography (OCT). Methods: Twenty patients with untreated choroidal melanoma and 40 patients with presumed choroidal naevi managed by regular observation were included in the study. OCT scans across the surface of the tumour and surrounding tissue were acquired for all participants. The appearance of retinal tissue on the OCT scans was considered to be abnormal if it did not display the well defined band structure characteristic of normal tissue on OCT scans. Results: Serous retinal detachments were observed in all patients with choroidal melanoma and 18 out of 20 also had abnormal retinal structure or intra-retinal splitting in the tissue overlying the tumour. Out of the 40 patients with presumed choroidal naevi, 12 had serous detachments and three had either abnormal retinal structure or intra-retinal splitting overlying the lesion. Conclusions: Secondary retinal changes associated with choroidal lesions can be documented by OCT. These changes were observed in most patients with choroidal melanoma included in the study group but were far less prevalent in the patients with presumed choroidal naevi. OCT is also able to identify the presence of small serous detachments before they become clinically visible. Follow up of these patients is required to determine whether the OCT results may be of use in the differential diagnosis of small choroidal lesions.

Functional imaging of the retina using the multifocal electroretinograph: a control study.

BACKGROUND: A new technique exists that enables functional mapping of the retina. A control population was examined to obtain normative values and to assess the reproducibility of this new test. METHODS: Twenty healthy volunteers were tested using a 61 hexagonal array stimulus with a 14 minute recording period. Median 5th and 95th percentiles were determined for implicit times and amplitude measures for the 61 test areas. Repeat measurements were performed on 10 individuals. Wilcoxon and Bland and Altman techniques were used to quantify reproducibility of the test. RESULTS: The implicit time of the wave-form components was not found to vary over the retina (peak or b-wave component, 35.52 (1.4) ms; trough or a-wave component, 17.76 (0.8) ms). Reproducibility was found to decrease with eccentricity (coefficient of repeatability 17.4% for the central area increasing to 30.3% for the peripheral ring). CONCLUSIONS: The findings suggest that reproducibility, although variable with eccentricity, is comparable with conventional electrophysiology. These limits of variation were used to assign confidence intervals to individual retinal areas and will be used (future work) in the examination of diseased states.

Optical coherence tomography and multifocal electroretinography of X-linked juvenile retinoschisis.

Optical coherence tomography and multifocal electroretinography of X-linked juvenile retinoschisis

Optical coherence tomography in the diagnosis of subclinical serous detachment of the macula secondary to a choroidal nevus

We present a case in which optical coherence tomography (OCT) aided in the diagnosis of subretinal fluid (SRF) secondary to a choroidal nevus. A patient with a raised lesion above the left optic disc and distorted central vision was referred to our unit because of suspected choroidal melanoma. Fundus fluorescein angiography and slit-lamp investigation did not indicate any areas of SRF; however, OCT showed serous detachment in the macular area. The lesion was treated with laser photocoagulation and, when reviewed at four weeks post-treatment, repeat OCT scans showed that the area of SRF had cleared. In this case OCT was able to detect a subclinical serous detachment in the macula. This may have important implications in the monitoring of patients with small suspicious lesions.

The wide field multifocal electroretinogram reveals retinal dysfunction in early retinitis pigmentosa

The diagnosis of retinitis pigmentosa (RP) is made on the basis of characteristic retinal pigmentation changes, visual field defects, and reduction in amplitude or loss of rod scotopic standard electroretinography (ERG) responses, with a possible history of night blindness and a positive family history of RP.1 Multifocal electrophysiology (mfERG), is a new technique that constructs a topographical map reflecting retinal function.2 Reports have suggested that the spatial resolution of mfERG is sufficient to detect focal changes in retinal function as RP progresses.3–5nnWe describe a case of early RP in which the amplitude and implicit times of the patients standard ERG rod and maximal responses were normal in the right eye and equivocal in the left eye. However, the peripheral retinal mfERG amplitude and implicit times were reduced and delayed. These abnormalities were obtained using a custom built wide field mfERG,6 which facilitates assessment of a 90 degree retinal field.nnA 29 year old woman was …

Crossed polarising filters to measure relative afferent pupillary defects : reproducibility, correlation with neutral density filters and use in central retinal vein occlusion

Measurement of a relative afferent pupillary defect (RAPD) can be carried out by attentuation of light received by the normal eye during the swinging flashlight test. Such measurements may be useful in the management of central retinal vein occlusion (CRVO). In this study a method employing cross polarised filters (CPFs) was tested for reproducibility. In addition the pattern of attenuation of light was compared with that by neutral density filters (NDFs). Finally, the method was used to investigate 74 patients with CRVO. The method was reproducible (8.7% variation) and showed exponential attenuation of light (in contrast to linear attenuation by the NDFs). In unilateral CRVO a sensitivity of 71% and specificity of 69% for the risk of iris neovascularisation was determined by the presence of RAPD requiring 20° of rotation of the CPFs. It is concluded that CPFs provide a useful alternative to NDFs for the measurement of RAPD and have some advantages. They can be employed in the clinical management of patients with CRVO.

Simultaneous structural and functional imaging of the macula using combined optical coherence tomography ophthalmoscope and multifocal electroretinogram

Multimodal imaging (MMI) is a new imaging technique that combines an electrophysiological test (multifocal electroretinogram) with an optical coherence tomography ophthalmoscope. MMI allows the two technologies to operate simultaneously yet independently to provide accurate correlation of macular structure and function at multiple sites. Preliminary work with MMI in patients with macular holes showed that functional deficits existed beyond the geographical area of structural alterations and that macular hole size did not always correlate with the severity of functional loss. Functional information may therefore be important when assessing prognosis in these patients. We envisage that MMI may prove a useful new tool in the assessment of many macular pathologies.

Recovery of visual function in a patient with birdshot chorioretinitis

Birdshot chorioretinopathy (BSCR) is a rare inflammatory disease, which generally follows a chronic course of progressive loss of vision to 6/60 or worse.1 However, the vision may stabilise1 or, rarely, improve slightly.2 Commonly prescribed treatment regimens, including oral steroids, and one or two immunosuppressive agents, may stabilise but generally do not cure the condition.3nnWe describe a case of BSCR in which there was a marked improvement in Snellen acuity and retinal function, measured with wide field multifocal electroretinography (WF-mfERG),4,5 in a patient intolerant of conventional treatment, who self medicated with an antioxidant preparation.nnA 53 year old white woman was referred with a 2 year history of decreased vision and floaters affecting both eyes. Snellen acuity was 6/24, N8 in the right eye and 6/12, N8 in the left eye. Moderate vitritis, cystoid macular oedema, swelling of the optic discs, and the presence of scattered, deep, pale creamy white lesions, were compatible with a diagnosis of BSCR, supported by positive HLA-A29 serology.nnA reducing dose of oral prednisolone in conjunction with cyclosporin was commenced. There was no improvement in visual …

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.

Chapter 5 The multifocal electroretinogram

Publisher Summary The multifocal electroretinogram (mfERG) is a relatively new objective technique for mapping retinal function. Although it is applied in a similar manner as the conventional electroretinogram (ERG), it offers advances in the spatial and temporal information it can provide. Unique mathematical sequences are used to provide rapid aperiodic stimulation of the visual system. The composite response is the result of stimulation at multiple frequencies and reflects photoadaptive non-linear processes within the retina. The nature of these mathematical driving sequences allows multiple areas of the visual field to be stimulated simultaneously, but independently. The technique offers potential to provide unique objective information on the integrity and function of the visual system. This chapter covers the basic principles of the technique and common factors that may influence the quality and interpretation of results. The mfERG allows for the simultaneous recording of many focal retinal responses in a relatively brief recording period. The mfERG evokes these electrophysiological responses using a stimulus generally consisting of multiple hexagonal scaled elements, which are independently switched between low or high luminance according to a random sequence that allows the focal retinal responses to be independently obtained and analyzed.