Pattern visual evoked potentials in hyperthyroidism

Clinical electrophysiology of the optic nerve and retinal ganglion cells

Clinical electrophysiological assessment of optic nerve and retinal ganglion cell function can be performed using the Pattern Electroretinogram (PERG), Visual Evoked Potential (VEP) and the Photopic Negative Response (PhNR) amongst other more specialised techniques. In this review, we describe these electrophysiological techniques and their application in diseases affecting the optic nerve and retinal ganglion cells with the exception of glaucoma. The disease groups discussed include hereditary, compressive, toxic/nutritional, traumatic, vascular, inflammatory and intracranial causes for optic nerve or retinal ganglion cell dysfunction. The benefits of objective, electrophysiological measurement of the retinal ganglion cells and optic nerve are discussed, as are their applications in clinical diagnosis of disease, determining prognosis, monitoring progression and response to novel therapies.

Controversies in the clinical evaluation of active thyroid-associated orbitopathy: use of a detailed protocol with comparative photographs for objective assessment

Despite many learned publications over recent decades, the assessment of active thyroid-associated orbitopathy (TAO) remains difficult and controversial. There are no biochemical, immunological or imaging investigations which can identify active disease reliably, and clinical assessment is still of paramount importance. We therefore review the strengths and weaknesses of all methods of clinical assessment. A new atlas for clinical assessment of soft tissue signs has been developed, and its reproducibility assessed. It details a suggested protocol that could help standardize descriptions of TAO and allow more objective assessment of its activity and severity. This is relevant to general endocrinologists, who have a crucial role in the identification of patients who require ophthalmological assessment. Certain aspects are more relevant to ophthalmologists and endocrinologists who have a special clinical and research interest in TAO. Unless a reproducible system of assessment is devised and widely adopted, it will remain difficult to interpret research meaningfully, particularly if results appear to contradict.

Early detection of P-VEP and PERG changes in ophthalmic Graves' disease

BACKGROUND

In Graves' disease the optic neuropathy (ON) is due to direct compression of the nerve and/or of its blood supply. The aim of the present study was to detect early changes in the visual functions of patients affected by ophthalmic Graves' disease (OGD) by using electrophysiological tests (P-VEP and PERG).

METHODS

We studied 50 OGD patients who were in a range between class 2 and class 5 according to the Donaldson-American Thyroid Association classification, i.e. had no evident ON and normal visual acuity. We recorded transient reversal PERG and P-VEP in response to the stimulation of one eye at three spatial frequencies (2.2, 1.1 and 0.5 c/d).

RESULTS

Our results showed a statistically significant reduction in PERG amplitude in class 5, while the P-VEP amplitude was already reduced in class 2.

CONCLUSION

The electrofunctional tests were useful to detect small changes in the visual function of patients affected by initial stages of OGD. Therefore, P-VEP and PERG recordings appear to be a useful tool for early diagnosis of the optic nerve involvement in Graves' disease.