The assessment of acute chorioretinal changes due to intensive physical exercise in young adults.

PURPOSE: There is abundant evidence on the benefits of physical activity on cardiovascular health. However, there are only few data on the acute effects of physical exercise on the retina and choroid. Our aim was the in vivo examination of chorioretinal alterations following short intense physical activity by spectral domain optical coherence tomography (SD-OCT). METHODS: Twenty-one eyes of 21 healthy, young subjects (mean age 22.5 ± 4.1 years, 15 males and 6 females) were recruited. Macular scanning with a SD-OCT was performed before and following a vita maxima-type physical strain exercise on a rowing ergometer until complete fatigue. Follow-up OCT scans were performed 1, 5, 15, 30 and 60 minutes following the exercise. The OCT images were exported and analyzed using our custom-built OCTRIMA 3D software and the thickness of 7 retinal layers was calculated, along with semi-automated measurement of the choroidal thickness. One-way ANOVA analysis was performed followed by Dunnett post hoc test for the thickness change compared to baseline and the correlation between performance and thickness change has also been calculated. The level of significance was set at 0.001. RESULTS: We observed a significant thinning of the total retina 1 minute post-exercise (-7.3 ± 0.6 µm, p < 0.001) which was followed by a significant thickening by 5 and 15 minutes (+3.6 ± 0.6 µm and +4.0 ± 0.6 µm, respectively, both p <0.001). Post-exercise retinal thickness returned to baseline by 30 minutes. This trend was present throughout the most layers of the retina, with significant changes in the ganglion cell-inner plexiform layer complex, (-1.3 ± 0.1 µm, +0.6 ± 0.1 µm and +0.7 ± 0.1 µm, respectively, p <0.001 for all), in the inner nuclear layer at 1 and 5 minutes (-0.8 ± 0.1 µm and +0.8 ± 0.1 µm, respectively, p <0.001 for both), in the outer nuclear layer-photoreceptor inner segment complex at 5 minute (+2.3 ± 0.4 µm, p <0.001 for all) and in the interdigitation zone-retinal pigment epithelium complex at 1 and 15 minutes (-3.3 ± 0.4 µm and +1.8 ± 0.4 µm, respectively, p <0.001 for both). There was no significant change in choroidal thickness; however, we could detect a tendency towards thinning at 1, 15, and 30 minutes following exercise. The observed changes in thickness change did not correlate with performance. Similar trends were observed in both professional and amateur sportsmen (n = 15 and n = 6, respectively). The absolute changes in choroidal thickness did not show any correlation with the thickness changes of the intraretinal layers. CONCLUSIONS: Our study implies that in young adults, intense physical exercise has an acute effect on the granular layers of the retina, resulting in thinning followed by rebound thickening before normalization. We could not identify any clear correlation with either choroidal changes or performance that might explain our observations, and hence the exact mechanism warrants further clarification. We believe that a combination of vascular and mechanic changes is behind the observed trends.

The Predictive Role of Thyroid Hormone Levels for Early Diabetic Retinal Changes in Experimental Rat and Human Diabetes.

Purpose: In diabetic subjects, early visual functional alterations such as color vision deficiencies (CVDs) are known to precede clinically apparent diabetic retinopathy. Prominent photoreceptor outer segment degeneration and an increase in the number of retinal dual cones (co-expressing S- and M-opsins simultaneously) have been described in diabetic rat models, suggesting a connection with the development of CVDs. As cone opsin expression is controlled by thyroid hormones, we investigated the diabetic retina in association with thyroid hormone alterations. Methods: In rat models of type 1 and 2 diabetes, dual cones were labeled by immunohistochemistry, and their numbers were analyzed in relation to free triiodothyronine (fT3) and free thyroxine (fT4) levels. Quantification of dual cones was also performed in human postmortem retinas. Additionally, a cross-sectional case-control study was performed where thyroid hormone levels were measured and color vision was assessed with Lanthony desaturated D15 discs. Results: A higher number of dual cones was detectable in diabetic rats, correlating with fT4 levels. Dual cones were also present in postmortem human retinas, with higher numbers in the three diabetic retinas. As expected, age was strongly associated with CVDs in human patients, and the presence of diabetes also increased the risk. However, the current study failed to detect any effect of thyroid hormones on the development of CVDs. Conclusions: Our results point toward the involvement of thyroid homeostasis in the opsin expression changes in diabetic rats and human samples. The evaluation of the possible clinical consequences warrants further research.

The Effect of Physical Exercise on the Retina and Choroid.

There is only limited information available on the effects of physical exercise on the posterior pole. Retinal circulation is autoregulated similarly to the brain vasculature in order to provide constant flow and thus constant nutrition of the inner retinal structures while the choroid is mostly controlled by the sympathetic nervous system. The available data show that physical exercise may indeed have a positive effect on the retina and visual function. The assessment of retinal structure could serve as a marker in sports medicine, whereas physical activity could exert a positive protective effect against diseases such as diabetic retinopathy or age-related macular degeneration. According to our theory, similar to the term "trained heart" used in cardiology and sports medicine, the term "trained eye" could also be coined. This latter term would help to further emphasize the beneficial effects of physical exercise that works protectively not only for the cardiovascular but for the visual system as well, and thus could further help in the fight against avoidable blindness worldwide.