D. Papakostopoulos

The Farnsworth-Munsell 100 hue test in the first episode of demyelinating optic neuritis.

The Farnsworth-Munsell 100 hue test (F-M 100) was used to examine 30 patients with their first episode of unilateral demyelinating optic neuritis (DON) at presentation, after 6 weeks and after 6 months. Twelve patients satisfactorily completed the test with the affected eye at presentation. This number had increased to 23 by 6 weeks and to 27 by 6 months. No patient with a visual acuity of LogMAR 0.86 (Snellen equivalent approx 6/43) or worse, could complete the test. The mean total error score of affected eyes showed significant improvement at each subsequent examination but was always worse than the non-affected eyes. There was a significant correlation between total error scores and visual acuities of affected eyes at presentation and after 6 months. Fourteen patients recovered a visual acuity of LogMAR 0.0 (Snellen equivalent 6/6) or better but the total error scores of the affected eyes were significantly worse than the non-affected eyes (p = 0.017), indicating that defective colour vision is an indicator of a previous episode of DON despite the recovery of normal visual acuity. DON is reported to produce a red-green (Type II) axis of colour defect but individual F-M 100 polar diagrams were usually generally abnormal and did not show any predominance of recognisable axis of colour defect at any examination. Group averaging of the F-M 100 data from such a well-defined group of patients with acute DON revealed a significant bipolar abnormality in the tritan (blue-yellow) axis at presentation which was not demonstrated at the subsequent examinations or at any examination of the non-affected eyes.

Comprehensive standardized ophthalmic telemedicine

The Electrodiagnostic Neurophysiological Automated Analysis (ENAA) telematic system was developed in the EU EUREKA project. To validate the system 2500 electrodiagnostic tests were administered in a standardized manner during a three-year period. The tests were performed on 70 normal subjects and 500 patients in five laboratories in three European countries. The data were transmitted to the Bristol Telematic Electrodiagnostic Centre in the Bristol Eye Hospital. Data from normal subjects were not significantly different between laboratories. Data from patients were reported upon and the conclusions transmitted to the place of origin. The system provided the remote consultant with multimedia data, including medical images such as colour fundus photography and angiography, video and sound.

Clinical and infrared pupillometry in central retinal vein occlusion.

Measurements of pupillary reactivity and size were recorded using neutral density filters and infrared pupillometry (IRP) in a prospective masked study of acute central retinal vein occlusion (CRVO) to quantify the two methods of measurement and to compare their value in the prediction of rubeosis. Thirty two patients were examined within 45 days of disease onset. The mean relative afferent pupillary defect (RAPD) with filters was significantly greater in patients who developed rubeosis than in those who did not (0.9 vs 0.3 log units; p = 0.012). Using IRP, the pupillary diameters in the dark (maximum) and in the light (minimum) were significantly greater, the rate of pupillary constriction was significantly lower, and the latency of constriction was significantly greater in affected eyes than in unaffected eyes. The differences between affected and unaffected eyes in the IRP parameters of latency, rate, maximum, and minimum pupillary diameters were significantly greater in patients who developed rubeosis than in those who did not. Discriminant analysis of the IRP parameters correctly and statistically significantly identified rubeotic patients with 83% sensitivity and 95% specificity. An RAPD of > or = 0.6 log units was 83% sensitive and 70% specific in this regard. It is concluded that pupillary reactions are abnormal in many patients with acute CRVO, as measured by both pupillometric methods. The degree of these abnormalities has a relationship to the development of rubeosis, and might prove useful in planning the follow up of these patients or in deciding whether to apply panretinal photocoagulation. The neutral density filter test is readily available but subjective. IRP is more specific, objective, and suited to further development, but requires sophisticated equipment.

The electro-oculogram in central retinal vein occlusion.

As part of a prospective masked study, the electro-oculogram (EOG) was recorded from 28 patients within 48 days of developing central retinal vein occlusion (CRVO). The EOG light peak/dark trough ratio (Lp/Dt) x 100 was significantly lower in the affected than in the unaffected eyes of patients (p < 0.001), and abnormally low in absolute terms in 20 patients (71%). All unaffected fellow eyes had a normal EOG ratio. The mean Lp amplitude of affected eyes was significantly smaller than that of unaffected eyes (p < 0.001), whereas the differences in mean Dt amplitudes between affected and unaffected eyes were not statistically significant. The Lp amplitude in the affected eye was 48% or less of that in the unaffected eye in the eight patients (29%) who developed rubeosis iridis during the 9 month follow-up, and in six others. No patient whose Lp amplitude in the affected eye was greater than 48% of that in the unaffected eye, developed rubeosis. It is concluded that the Lp amplitude is abnormal in patients with acute CRVO. The degree of this abnormality bears a relation to the development of rubeosis, which might prove a useful indicator of whether to institute or withhold panretinal photocoagulation.

Evaluation of the first international teleconference in ophthalmology.

The First International Teleconference in Ophthalmology was held during March 1998 between five sites in the UK, USA, Greece and Malaysia. ISDN transmission at 128 kbit/s was used to reduce costs while maintaining the clarity of the presented material. Specialized lecture theatres were not available at all sites and conventional halls had to be adapted for videoconferencing. For this reason initial point-to-point testing was carried with Bristol to simplify problem solving. Thereafter, a multipoint bridge was used to connect all sites together. During the conference a number of individual presentations were given, all followed by extensive discussion periods. Special instructions were given before hand on the production of slide material, with particular reference to fount sizes and colour combinations. Full use was made of various presentation media, including slides, videos and live demonstrations. The conference was attended by over 500 delegates, all of whom were specialists in ophthalmology. The technology employed was ideal for teaching purposes. However, if used in a clinical field, it should be kept in mind that the choice of transmission rate makes certain features not easily apparent in images but they become clearer when pointed out by the presenter.

Telematic electrodiagnosis from six laboratories in three European countries and one Asian country

The results of an electrodiagnostic test, the electro-oculogram, recorded under standardized conditions, were compared. Recordings were obtained from 70 normal subjects in three European countries and 28 subjects in an Asian country. All subjects were 18–34 years old. Equal numbers of male and female patients were tested in each of six laboratories. There were no significant differences between the results of the European laboratories. There were, however, significant differences between the results of the European and the Asian laboratories, and between the results from the male and female subjects in all laboratories. This suggests the need for considering the possibility of male/female as well as local variations in normal control values when telemedicine is applied on a global scale.

Electrodiagnostic evaluation of the visual system: the role of the clinician

Visual electrodiagnosis is a new discipline with a long history. The foundations include the disciplines of psychophysics, neurophysiology, electronics, computer science, statistics and medicine. However, with such a complex heritage, visual electrodiagnosis has taken a considerable time to evolve to its present form. Today visual electrodiagnostic assessment is relevant, not only for conditions primarily affecting the visual system, but also in more generalised pathological states in which eye changes may be a manifestation. Pressures for more refined and accurate diagnoses stem both from a continuing improvement in knowledge of disease processes by the medical profession and greater expectations on the part of patients seeking advice. Specialised investigative services such as electrodiagnosis, if these are appropriately funded and maintained, provide data to clinicians which is repeatable and objective, without resorting to invasive technology.

Standardized visual evoked potentials for telematic electrodiagnosis from five laboratories in three European countries.

The pattern-reversal visual evoked potential PR VEP is an electrodiagnostic test which uses an alternating checkerboard pattern as the visual stimulus. To validate the performance of an automated testing system, the equipment was installed in five locations in three countries the UK, Greece and Cyprus . PR VEPs require accurate control of stimulus size, luminance, contrast, timing, multichannel recordings and various modes of signal processing. Recordings were obtained from 70 subjects, 18-34 years old seven male and seven female in each laboratory . The data were transmitted by telephone line to the central station in Bristol. Only in Bristol were the operators experienced. There were no significant differences between laboratories in latency or amplitude of the N70 and P100 components. There were no significant differences between eyes. There were significant differences between the sexes but this was related to head size. Decreased square size used in stimulation produced an increased latency in both components. The amplitude of the N70 component increased while that of the P100 decreased with reduced square size. The results confirmed the ability of the automated system to produce standardized PR VEP recordings comparable to those obtainable in advanced laboratories. The system performed well in different locations using inexperienced operators. The system is suitable for multicentre research studies and telemedicine.

Visual evoked potentials in diabetics without retinopathy.

There may, however, be a subtle distinction between the needs of a patient who has become hypothyroid spontaneously or as a result of treatment directed towards thyrotoxicosis and the needs of a patient who has thyroid cancer. In the first instance thyroxine could be regarded as replacement treatment. In patients with differentiated thyroid cancer, however, it is generally considered advisable to give a dose of thyroxine which completely suppresses TSH. The figure shows values for serum T3 and T4 in a series of 20 patients who had undergone total thyroidectomy by a combination of surgery and iodine-131 treatment. Most of these patients were taking a maintenance dose of 200 ig of thyroxine daily, but a few were taking 250 [tg and one was taking 350 tg and had been doing so for many years. All patients had raised serum T4 values whereas all but one had normal serum T3 values. Most patients with thyroid cancer are in fact maintained on 200 Ftg of thyroxine daily. On this dose serum T4 values will be raised, serum T3 will be normal, and serum TSH will be suppressed. This can if necessary be confirmed by doing a thyrotrophin releasing hormone test, which in my experience always gives a flat response in these circumstances. I would suggest that patients with differentiated thyroid carcinoma should be maintained on a suppressive dose of thyroxine and that in these patients a raised serum T4 is not an indication for reducing the dose. AW G GOOLDEN Department of Radiotherapy and Oncology, Hammersmith Hospital, London W12 OHS