Pattern visual evoked potential in hypothyroid patients
To investigate the functional integrity of visual pathway in hypothyroid patients by pattern visual evoked potential (PVEP).
We enrolled 36 female patients with history of hypothyroidism (18 overt and 18 subclinical) aged 20 to 60 years and 36 healthy women of similar age (control group). All subjects had a complete ophthalmic examination. For VEP testing, subjects were exposed to checks subtending a visual angle of 15 and 60 min of arc.
For the 15 min of arc check size, the mean P100 latency was significantly delayed (113 milliseconds (ms)) and amplitude significantly reduced (9.2 microvolts (µv)) in the hypothyroidism group compared with controls (109.6 ms and 11.6 µv, respectively). For this 15′ check size, the group differences were related to significantly increased latency and reduced amplitude of responses in the group with overt hypothyroidism compared with controls. There was no difference between the groups (hypothyroid vs control) with 60 min of arc check size. There was a significant correlation between severity of the disease and PVEP component.
In conclusion, low levels of circulating hypothyroid hormone are associated with delay in the pattern VEP to small check sizes. This CNS involvement worsens in patients with greater severity and duration of hypothyroidism.
KeywordsHypothyroidism Visual evoked potential Central nervous system Visual pathway
We thank the research vice-chancellor of Mashhad University of Medical Sciences for supporting this study. The results described in this paper were of a MSc Optometry thesis.
No funding was received for this research
Compliance with ethical standards
Conflict of interest
All authors certify that they have no affiliations with or involvement in any organization or entity with any financial interest (such as honoraria; educational grants; participation in speakers’ bureaus; membership, employment, consultancies, stock ownership or other equity interest; and expert testimony or patent licensing arrangements) or non-financial interest (such as personal or professional relationships, affiliations, knowledge or beliefs) in the subject matter or materials discussed in this manuscript.
Statement of human rights
This study was approved (code 89956 and number 511/1142) by Research Council and Ethics Committee at Mashhad University of Medical Science and the research was carried out in agreement with the principle of the Declaration of Helsinki. This study was conducted after getting written informed consent from all participants.
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.
Informed consent was obtained from all individual participants included in the study.
Statement on the welfare of animals
This article does not contain any studies with animals performed by any of the authors.
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