The study of visual evoked potentials in patients with thyroid-associated ophthalmopathy identifies asymptomatic optic nerve involvement

Evaluation of visual evoked potentials in dysthyroid optic neuropathy

PURPOSE

To evaluate the findings of visual evoked potentials (VEP) in patients with dysthyroid optic neuropathy (DON).

METHODS

In this observational, cross-sectional study 40 eyes (22 patients) with a diagnosis of DON were included.

RESULTS

We discovered that in 16 out of 37 eyes with pattern-VEP (p-VEP), the latency of P100 wave was normal in spite of having a diagnosis of DON. The same pattern was also observed in the measurement of the amplitude of P100 wave: in 28 out of 37 eyes with p-VEP the amplitudes were observed as normal. In 3 eyes of 3 patients p-VEP showed no response, therefore a flash-VEP (f-VEP) was performed. Flash-VEPs of those patients indicated a prolonged P100 latency with a reduced amplitude. The sensitivity of abnormal P100 latency was 56.8% (95%CI 39.5-72.9%); and that of reduced P100 amplitude was 24.3% (95%CI 11.8-41.2%). Also, in 40 eyes color vision test by Arden was performed. In 36 eyes (20 patients) the tritan value was pathological (based on a threshold of ≥8%).

CONCLUSION

According our data, VEP seems to have a limited potential especially in patients with a good best-corrected visual acuity (BCVA ≤0.2 LogMAR) for identifying the optic nerve involvement. The fact that P100 latency and amplitude were normal even in cases with an optic nerve swelling makes us question the usefulness of the VEP for diagnosing cases of DON in daily clinical life.

Optical coherence tomography and electrophysiological analysis of proptotic eyes due to thyroid-associated ophthalmopathy

Purpose

To study the degree of morphological and functional changes in thyroid-associated ophthalmology (TAO) patients using optical coherence tomography and electrophysiological studies and investigate their clinical correlation.

Methods

A cross-sectional study including 40 patients with TAO and a control group with age- and sex-matched healthy subjects. All subjects underwent a complete ophthalmological examination, proptosis evaluation, spectral domain optical coherence tomography, and electrophysiological tests (pattern and multifocal electroretinograms, and visual evoked potentials).

Results

On multiple regression analysis, the degree of proptosis and P50 amplitude were the most important predictors of central foveal thickness (CFT) (β =  −  0.56 and 0.39 and p = 0.03 and 0.01, respectively); while duration of the disease, and clinical activity score (CAS) were the most important predictors of average RNFL thickness (β = 0.67 and  − 0.81 and p = 0.004 and  <  0.001, respectively).

Conclusion

In the absence of fundus changes, macular thinning along with functional alterations noticed by pattern and multifocal electroretinogram could indicate presence of subclinical retinopathy in TAO cases.

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.

Retinal nerve fiber layer thickness measured by optical coherence tomography predicts visual recovery after orbital decompression for dysthyroid optic neuropathy

PURPOSE

To determine the prognostic value of optical coherence tomography (OCT) measurement of the peripapillary retinal nerve fiber layer (RNFL) thickness in visual recovery after orbital decompression of patients with dysthyroid optic neuropathy (DON).

METHODS

A total of 52 eyes of 37 patients who underwent orbital decompression for DON between 2013 and 2019 were retrospectively reviewed. We examined peripapillary RNFL thickness, best-corrected visual acuity (BCVA), visual field (VF) for mean deviation (MD) and pattern standard deviation (PSD), and pattern-reversed visual evoked potential (PVEP) for P100 latency and amplitude before and after surgery. Black and white checkerboard square sizes of PVEP were 15 and 60 arcmin (arcminute and minute of angle). Changes in RNFL overall thickness and by quadrant and interocular differences were evaluated and studied regarding changes in BCVA, VF and PVEP.

RESULTS

There was a significant improvement in BCVA, VF, and PVEP, whereas a dramatic reduction in RNFL thickness of all DON patients in global average, temporal, superior, and inferior quadrants (P = 0.005, P = 0.024, P = 0.016, and P = 0.001, respectively) after decompression surgery, except for nasal quadrant (P = 0.057). The preoperative RNFL thickness in each quadrant was negatively correlated with postoperative changes of BCVA and PSD and positively correlated with changes of MD and P100 amplitude at 60 arcmin (all P < 0.05). Except for temporal quadrant (P = 0.125), the preoperative RNFL thickness in other quadrants was positively correlated with postoperative changes of P100 amplitude at 15 arcmin (all P < 0.05). The nasal RNFL thickness was an excellent predictor for improvement in BCVA by 20/25 or better and in MD by 10 dB or more after surgery, whose cutoff value was 73.50 μm, while the inferior and superior RNFL thickness could act as a predictor for improvement in P100 amplitude by 5 μV or more at 60 arcmin and at 15 arcmin, respectively, whose cutoff value was, respectively, 143.00 μm and 130.50 μm (all P < 0.05).

CONCLUSION

RNFL thickness measured by OCT was correlated with visual function recovery after decompression surgery in patients with DON, which could also act as a predictor for better visual prognosis.

The Therapeutic Effect of Combination of Orbital Decompression Surgery and Methylprednisolone Pulse Therapy on Patients with Bilateral Dysthyroid Optic Neuropathy

PURPOSE

To investigate the synergic effect of combination of orbital decompression surgery and methylprednisolone pulse therapy (MPT) and MPT alone on the visual function in patients with bilateral dysthyroid optic neuropathy (DON).

METHODS

For each involved patient with bilateral DON, only one eye was treated with orbital decompression surgery which was conducted by the same doctor, and each of them received MPT after surgery. If the visual function deteriorated despite treatment, patients would switch to the other treatment. All the patients were followed up for 3 months after surgery. Clinical features of patients including best corrected visual acuity (BCVA), intraocular pressure (IOP), proptosis, upper eyelid retraction, and clinical activity score (CAS) before and after surgery were analyzed, respectively. Visual field and visual evoked potential (VEP) tests were also performed. Paired t-test and Wilcoxon matched-pairs signed ranks sum test were used to analyze the data.

RESULT

A prospective cohort of 23 patients with bilateral DON was enrolled in this cohort study. No patients failed to the therapy or switched to another treatment. The quantitative variables were shown as means and standard deviations (SD). After 3 months of combined treatment of orbital decompression surgery and MPT, BCVA (logMAR) improved, proptosis was reduced and the upper eyelid retraction was relieved in both eyes of patients; however, these improvements were more significant in the operated eyes than in the fellow (nonoperated) eyes. IOP decreased significantly in the operated eyes (P=0.002), while having no significant change in the nonoperated eyes (P=0.002), while having no significant change in the nonoperated eyes (P=0.002), while having no significant change in the nonoperated eyes (P=0.002), while having no significant change in the nonoperated eyes (P=0.002), while having no significant change in the nonoperated eyes (P=0.002), while having no significant change in the nonoperated eyes (P=0.002), while having no significant change in the nonoperated eyes (P=0.002), while having no significant change in the nonoperated eyes (P=0.002), while having no significant change in the nonoperated eyes (P=0.002), while having no significant change in the nonoperated eyes (P=0.002), while having no significant change in the nonoperated eyes (P=0.002), while having no significant change in the nonoperated eyes (P=0.002), while having no significant change in the nonoperated eyes (P=0.002), while having no significant change in the nonoperated eyes (.

CONCLUSION

A combination of orbital decompression and MPT can significantly improve visual function in patients with DON, reduce intraocular pressure, and relieve clinical symptoms such as upper eyelid retraction and proptosis, while MPT alone has a limited effect. For DON patients, orbital decompression should be performed promptly to improve the visual function.

Electrophysiological Studies in Thyroid Associated Orbitopathy: A Systematic Review

Dysthyroid optic neuropathy (DON) is the commonest cause of blindness in thyroid associated orbitopathy (TAO). While diagnosis remains clinical, objective tests for eyes with early or equivocal findings are lacking. Various electrophysiological studies (EPS) have been reported, yet the types and parameters useful for DON remain inconclusive. We performed a systematic literature search in MEDLINE, EMBASE and the Cochrane databases via the OVID platform up to August 20, 2017. 437 records were identified for screening and 16 original studies (1327 eyes, 787 patients) were eligible for review. Pattern visual evoked potential (pVEP) was the most frequently studied EPS. Eyes of TAO patients with DON showed delayed P100 latencies, decreased P100 amplitudes or delayed N75 latencies during pVEP, compared to those without or healthy controls. Due to study heterogeneity, no quantitative analysis was possible. This review highlights the most common type (pVEP) and useful parameters (P100 latency and amplitude) of EPS, and supports further research on them using standardized testing conditions.

Severe Ophthalmological Complications of Thyroid Disease are Rare in Ibadan, Southwestern Nigeria: Results of a Pilot Study

BACKGROUND

Ocular manifestations of thyroid dysfunction constitute a wide clinical spectrum ranging from minor ocular discomfort, lid retraction, lid lag and ocular injection, to sight threatening eyeball protusion and optic nerve compression. Thyroid-related eye disorders are most commonly associated with Graves’ disease, and this most frequently occurs in the setting of hyperthyroidism. However, in 10% of cases, typical eye signs have also been reported in euthyroid and hypothyroid states. The severity of thyroid eye disease has been linked to cigarette smoking. There is very little data specifically reporting the ocular manifestations of thyroid disease among black African patients and there is no known report from Nigeria. This pilot study therefore focused on documenting the ocular signs accompanying thyroid dysfunction in a black African population.

AIM

To evaluate the pattern of ocular complications, among patients treated for thyroid disorders, in a major Nigerian teaching hospital.

RESULTS

A total of 75 patients with thyroid dysfunction, were evaluated, comprising 63 females and 12 males. There was a very low prevalence of smoking among patients (<5%). Graves’ disease was the commonest thyroid disorder, representing 70% of cases. Seventy-eight percent of patients were hyperthyroid, 11.8% were euthyroid and only 9.8% of patients were hypothyroid. Commonest systemic symptoms were neck swelling (68.6%), weight loss (63.8%), tremors (60.9%) and palpitations (59.4%). Two-thirds of patients reported ocular symptoms consisting mainly of painless eye swelling (66.7%) and ocular irritation (58%). Conjunctival injection, lid lag and lid retraction were the commonest ocular signs. Chemosis, severe proptosis and ocular motility disorder were very rare. Optic neuropathy was found in 4 patients but was related to pre-existing glaucoma. Majority of patients required only ocular emollients and tear supplements.

CONCLUSION

Severe ocular complications of thyroid disorders were uncommon in this cross-section of Nigerian patients. This may be linked to the very low prevalence of cigarette smoking among Nigerians or genetic and environmental factors linked to their African heritage.

Evaluation of multifocal visual evoked potentials in patients with Graves' orbitopathy and subclinical optic nerve involvement

Dysthyroid optic neuropathy is the most serious, although infrequent (8-10 %) complication in Graves' orbitopathy (GO). It is known that early stages of compressive optic neuropathy may produce reversible visual field defects, suggesting axoplasmic stasis rather than ganglion cell death. This observational, cross-sectional, case-control study assessed 34 consecutive patients (65 eyes) with Graves' hyperthyroidism and longstanding GO and 31 age-matched control subjects. The patients' multifocal visual evoked potentials (mfVEP) were compared to their clinical and psychophysical (standard automated perimetry [SAP]) and structural (optic coherence tomography [OCT]) diagnostic test data. Abnormal cluster defects were found in 12.3 % and 3.1 % of eyes on the interocular and monocular amplitude analysis mfVEP probability plots, respectively. As well, mfVEP latencies delays were found in 13.8 and 20 % of eyes on the interocular and monocular analysis probability plots, respectively. Interestingly, 19 % of patients with GO had ocular hypertension, and a strong correlation between intraocular pressure measured at upgaze and mfVEP latency was found. MfVEP amplitudes and visual acuity were significantly related to each other (P < 0.05), but not with the latencies delays. However, relationships between the interocular or monocular mfVEP amplitudes and latencies analysis and SAP indices or OCT data were not statistically significant. One-third of our patients with GO showed changes in the mfVEP, indicating significant subclinical optic nerve dysfunction. In this sense, the mfVEP may be a useful diagnostic tool in the clinic for early diagnosis and monitoring of optic nerve function abnormalities in patients with GO.

Using frequency-doubling perimetry to detect optic neuropathy in patients with Graves' orbitopathy

PURPOSE

to test the ability of frequency-doubling technology (FDT) perimetry to detect dysthyroid optic neuropathy (DON).

METHODS

Fifteen eyes of 15 patients with DON and 15 healthy control eyes were studied. Eligible eyes had a diagnosis of DON based on visual field abnormalities on standard automated perimetry and had visual acuity better than 20/30. FDT testing was performed using both the C-20-5 screening test and the C-20 full-threshold test. Normal and DON eyes were compared with regard to FDT mean sensitivity.

RESULTS

Sensitivity ranges were 40.0%-86.7% for the screening test, and 53.3%-100.0% (total deviation) and 20.0-93.3 (pattern deviation) for the C-20 threshold test. The corresponding specificity ranges were 86.7-100.0, 33.3-93.3, and 26.7-100.0, respectively. The best sensitivity/specificity ratios were for one abnormal point depressed <5% in the screening test (86.7%/86.7%), one point depressed <1% in the total deviation analysis (80.0%/86.7%), and one point depressed <2% in the pattern deviation analysis (80.0%/86.7%). DON eyes presented significantly lower than normal average sensitivity in the central, pericentral, and peripheral areas.

CONCLUSIONS

FDT perimetry is a useful screening tool for DON in eyes with normal or only slightly reduced visual acuity.

Association of Graves' disease and prevalence of circulating IFN-gamma-producing CD28(-) T cells

BACKGROUND

Peripheral blood CD4(+) and CD8(+) T-cell subsets lacking surface CD28 have been suggested to predispose patients to immune-mediated disorders.

MATERIALS AND METHODS

To determine the role of CD28(-) T-cell subset in Graves' disease (GD), we characterized peripheral blood CD4(+)CD28(-) and CD8(+)CD28(-) T cell from early onset GD patients.

RESULTS AND DISCUSSION

GD patients had significantly higher percentages of CD4(+)CD28(-) and CD8(+)CD28(-) T cells than did healthy donors. Both CD28(-) T cells expressed mostly CD45RO, suggesting that they are activated and/or are memory T cells. GD patient-derived CD4(+)CD28(-) and CD8(+)CD28(-) T cells produced more intracellular IFN-gamma than their counterparts from healthy donors. Furthermore, CD4(+)CD28(-) and CD8(+)CD28(-) T cells from GD patients with Graves' ophthalmopathy (GO) secreted higher level of intracellular IFN-gamma than those CD28(-) T cells from GD patients without GO. Retrospective analysis showed that the increased levels of CD4(+)CD28(-) T cells and their IFN-gamma-producing subgroups were positively correlated to the serum anti-thyrotropin receptor (TSHR) autoantibodies (TRAb). Our observations suggest that increased IFN-gamma-producing CD28(-) T cells in GD patients may play an important role in the pathogenesis of GD.