Effect of phototherapy on spontaneous eye blink rate in subjects with seasonal affective disorder

Effect of distance vision and refractive error on the spontaneous eye blink activity in human subjects in primary eye gaze

PURPOSE

To evaluate whether visual target character and visibility affects spontaneous eye blink rate (SEBR) in primary eye gaze and silence.

METHODS

Video recordings were made of young healthy adults who were either emmetropic (n=32) or who wore spectacles for refractive error (range -4.75D and +4.50D (n=31). Emmetropes had 5min recordings made whilst seated and looking towards a distant whiteboard. For spectacle wearers, recordings were made whilst looking towards the whiteboard with a 35mm sized cross, and repeated after spectacle removal. The average number of eye blinks over 5min was assessed, and its intra-subject variability as the coefficient of variation (COV).

RESULTS

Over 5min without a distance target, an average SEBR of 10.4blinks/min was observed in emmetropes with a of COV=38.1%, and a significant increase in SEBR over the 5th minute to 13.6blinks/min. Hyperopes being asked to look towards a distant target showed the essentially same blinking rate of 11.1/min with or without spectacle wear with the intra-subject variability (COV) being 21.3%. Myopic subjects showed a slightly higher SEBR if looking towards a target without their spectacles (12.4 vs. 11.0blinks/min), with the COV being 18.8%.

CONCLUSIONS

The studies indicate that some form of visual target could be useful to promote constancy of spontaneous eye blink activity over time, but that a distance visual target (when provided) does not need to be seen clearly.

Light therapy: is it safe for the eyes?

OBJECTIVE

Light therapy has become an increasingly popular treatment for depression and a range of other neuropsychiatric conditions. Yet, concerns have been raised about the ocular safety of light therapy.

METHOD

We conducted the first systematic review into the ocular safety of light therapy. A PubMed search on January 4, 2017, identified 6708 articles, of which 161 were full-text reviewed. In total, 43 articles reporting on ocular complaints and ocular examinations were included in the analyses.

RESULTS

Ocular complaints, including ocular discomfort and vision problems, were reported in about 0% to 45% of the participants of studies involving light therapy. Based on individual studies, no evident relationship between the occurrence of complaints and light therapy dose was found. There was no evidence for ocular damage due to light therapy, with the exception of one case report that documented the development of a maculopathy in a person treated with the photosensitizing antidepressant clomipramine.

CONCLUSION

Results suggest that light therapy is safe for the eyes in physically healthy, unmedicated persons. The ocular safety of light therapy in persons with preexisting ocular abnormalities or increased photosensitivity warrants further study. However, theoretical considerations do not substantiate stringent ocular safety-related contraindications for light therapy.

Spontaneous eye blink rate as predictor of dopamine-related cognitive function-A review

An extensive body of research suggests the spontaneous eye blink rate (EBR) is a non-invasive indirect marker of central dopamine (DA) function, with higher EBR predicting higher DA function. In the present review we provide a comprehensive overview of this literature. We broadly divide the available research in studies that aim to disentangle the dopaminergic underpinnings of EBR, investigate its utility in diagnosis of DA-related disorders and responsivity to drug treatment, and, lastly, investigate EBR as predictor of individual differences in DA-related cognitive performance. We conclude (i) EBR can reflect both DA receptor subtype D1 and D2 activity, although baseline EBR might be most strongly related to the latter, (ii) EBR can predict hypo- and hyperdopaminergic activity as well as normalization of this activity following treatment, and (iii) EBR can reliably predict individual differences in performance on many cognitive tasks, in particular those related to reward-driven behavior and cognitive flexibility. In sum, this review establishes EBR as a useful predictor of DA in a wide variety of contexts.

Atypical pattern of rod electroretinogram modulation by recent light history: a possible biomarker of seasonal affective disorder

Our goal was to challenge both normal controls and patients with seasonal affective disorders (SAD) to various light histories and then measure their retinal response modulation using the electroretinogram (ERG) in both winter and summer. In winter and summer, 11 normal controls and 12 SAD patients were exposed to three different light conditions for 1 h (10,000, 100 and 5 lux) followed by an ERG. Groups showed similar ERG amplitudes in the 100 lux condition. Compared with the 100-lux condition, in controls, the ERG response was significantly increased in the 5-lux condition; in SAD, it was significantly decreased in the 10,000-lux condition. This pattern was present in both seasons. This is the first time a retinal response modulation anomaly has been observed in SAD patients in both the depressed and euthymic states. Retinal response modulation may represent an interesting biomarker of the disease for future research.

Melatonin in psychiatric disorders: a review on the melatonin involvement in psychiatry

In normal subjects, the secretion of melatonin, the pineal hormone that regulates the rhythm of many functions, exhibits a circadian pattern synchronized with the day-night cycle. An alteration of this secretory pattern has been found in various psychiatric disorders (seasonal affective disorder, bipolar disorder, unipolar depression, bulimia, anorexia, schizophrenia, panic disorder, obsessive compulsive disorder). At present, it is not known if such alterations have an etiological role or are secondary to the dysfunctions underlying the different disorders. In addition, we do not know if the involvement of melatonin in several disorders has the same significance in the pathophysiology of each disorder. An understanding of the role of the pineal hormone and of its alterations in psychiatric diseases could help to identify the biological mechanisms underlying such disorders.

Heat-loss response to a thermal challenge in seasonal affective disorder

This study extends earlier findings of poorly facilitated postexercise heat loss during the winter in seasonal affective disorder (SAD). While depressed in the winter, 19 SAD subjects exhibited a significantly impaired postexercise heat loss relative to 10 control subjects. During the summer while euthymic, SAD subjects did not significantly differ from control subjects in postexercise heat loss. Since thermoregulatory heat loss is a highly dopamine-dependent process, these results support earlier findings of poorly facilitated dopamine availability in SAD during the winter and suggest a centrally mediated effect of light in SAD.

Effects of phototherapy on electrooculographic ratio in winter seasonal affective disorder

Low electrooculographic (EOG) ratios have been reported in patients with seasonal affective disorder (SAD). This study was undertaken to replicate these results and to consider the effects of light therapy on the EOG in SAD patients. Sixteen outpatients with SAD and 16 age-, sex-, and medication-matched control subjects had EOG testing before and after 1 week of light therapy during the winter. The EOG ratios in the SAD patients were only marginally lower than those in the normal control subjects. These differences persisted after light therapy. Although the slightly decreased EOG ratios in SAD patients might have resulted from an artifact of test variability, drowsiness, or other confounding factors, the difference between patients and control subjects raises the possibility of retinal abnormality in SAD.

Seasonal variation in behavioral responses to m-CPP in patients with seasonal affective disorder and controls

This paper reports the behavioral responses to m-chlorophenylpiperazine (m-CPP), a serotonin agonist, in patients with seasonal affective disorder (SAD) and controls during the summer. Results are compared with the responses of SAD patients and controls given m-CPP in the winter. Results of the winter study were reported earlier by our group. Baseline Hamilton depression ratings in SAD patients were significantly lower in the summer than in winter (p < 0.05). Additionally, in both SAD patients and controls, there were seasonal differences on the National Institute of Mental Health (NIMH) self-rating scale items: "depressed affect," "dysphoria," and "functional deficit" at baseline. The behavioral responses to m-CPP across seasons differentiated patients from normals only in the "activation/euphoria" item, on which a far greater response was seen in patients than in controls during the winter. This behavioral response may be a state marker for winter depression, as it was significantly reduced after light treatment of these patients in the winter, and in the summer. SAD patients responded differently from controls on "altered self-awareness" and "dysphoria" independently of seasons, and these responses may be considered as possible trait markers for this condition. These results provide further evidence of a possible deficiency in serotonergic transmission in seasonal affective disorder.

Spontaneous eye blink rate in winter seasonal affective disorder

We investigated spontaneous eye-blink rates in 19 drug-free patients with winter seasonal affective disorder (SAD) and 18 normal control subjects. At baseline, there were no significant differences between the two groups (mean +/- SD blink rate: 15/minute +/- 8 vs. 15/minute +/- 7). Light therapy (10,000 lux: 1 hour each morning for 1 week) produced no significant change in mean (+/- SD) blink rates either in 10 SAD patients (13/minute +/- 8 vs. 10/minute +/- 7) or in 12 normal control subjects (15/minute +/- 6 vs. 14/minute +/- 6). A post hoc exploratory analysis of the effect of light therapy on premenopausal female subjects (5 patients and 9 control subjects) showed a significant decrease in mean (+/- SD) blink rate in the patients after treatment (17 +/- 6 vs. 12 +/- 8 compared with 15 +/- 7 vs. 16 +/- 5). These results do not support the idea that an elevated blink rate may be a general biological marker in SAD, but they suggest a possible link between light treatment and mechanisms that regulate blink rate in premenopausal SAD patients.

Electroretinography in seasonal affective disorder

Retinal mechanisms have been hypothesized in the pathophysiology of seasonal affective disorder (SAD). Electroretinography (ERG) is a noninvasive electrophysiologic test that provides an objective measure of photoreceptor and retinal function. We conducted dark-adapted ERG examinations with a bright white light stimulus in a group of depressed, drug-free patients with seasonal affective disorder (6 men, 18 women) diagnosed by DSM-III-R criteria, and a group of sex- and age-matched control subjects (6 men, 16 women) during the winter. A significant difference was found between SAD patients and controls, but female SAD patients had lower ERG b-wave amplitudes than female controls, while male SAD patients had higher amplitudes than the matched controls. The ERG b-wave implicit times (times from onset of stimulus to peak of b-wave) were significantly longer in the left eyes of the male control subjects. These data may indicate subtle retinal changes in patients with SAD, but the results must be considered preliminary because of the small number of subjects studied and the large intersubject variability in the ERG procedure.

Dimensional measurement of seasonal variation in mood and behavior

Recent epidemiologic studies have found that the behaviors that characterize seasonal affective disorder (SAD) show seasonal variation in 92%-95% of the general population, suggesting that seasonal variation in behavior and mood is a continuous, dimensional variable extending throughout the general population, defined at the upper extreme by SAD. Research into population seasonality will require a dimensional measure of seasonal variation in mood and behavior that produces a broad, finely graded distribution of seasonality scores sensitive to individual differences throughout the entire range of scores. Accordingly, the Inventory of Seasonal Variation (ISV) was developed as such a measure. This study demonstrated that the ISV has high internal structural validity and is highly sensitive to individual differences in seasonality across its entire range of scores in the normal population. This latter characteristic is not shared by other existing measures of seasonality. Initial external validity of the ISV was supported in that the mean of ISV scores of a SAD sample was found to lie at the 97th percentile of the normal population of scores. Analysis of ISV scores revealed that a winter pattern of seasonality was reported by over 95% of subjects, a pattern that was more pronounced in women than men, while a summer type of seasonality was reported by only 0.6% of the general population.

Retinal melatonin and dopamine in seasonal affective disorder

The author describes how phototherapy may treat seasonal affective disorder (SAD) by stimulating the production of retinal dopamine and suppressing the production of retinal melatonin. This hypothesis offers a framework in which winter-induced retinal dopamine deficiency or retinal melatonin overactivity may cause SAD and by which light reverses this syndrome. This hypothesis is consistent with recent data indicating that phototherapy in SAD acts specifically through the eyes.

Thermoregulatory response to thermal challenge in seasonal affective disorder: a preliminary report

It has recently been proposed that alterations in central dopamine (DA) functional activity may, in part, account for certain behavioral changes observed in seasonal affective disorder (SAD) during the winter. To explore this possibility, a preliminary study of thermoregulatory heat loss to an endogenous heat challenge--a strongly DA-dependent process--was undertaken in groups of four SAD woman and four nonpsychiatric control women across three conditions (winter, after successful phototherapy, and summer). Homeostatic heat loss during recovery from heat challenge in SAD, but not in control, subjects was found to be a significant function of light condition and of clinical state. Thermoregulatory heat loss in SAD subjects was significantly blunted in winter during depression, was similar in efficiency to control subjects after a successful antidepressant response to phototherapy, and tended to be more efficient than controls in summer during a euthymic state. Results raise the possibility that a common effect of phototherapy and summer light conditions is a facilitation of central DA activity in SAD.