Equine Health Update Issue 1 Volume 16 - Page 19

semi-rigid rubber quarter sphere with a flattened outer lip on one edge, which facilitated attachment to the mask. The lip was sewn onto a semi-rigid half ring of leather, which was then sewn to the rim of the eye opening of the mask. The inner surface of the cup was covered with reflective aluminium foil tape. The LED was positioned inside the cup at the centre point, where the lip met the rim of the eye opening. The legs of the LED pierced the eye cup and were soldered to the electrical wires outside the eye cup within the neoprene sleeve. The LED was positioned to shine up onto the reflective foil surface, diffusing light onto the horse’s cornea. This provided uniform, diffuse light and minimised distraction to the horse, permitting maintenance of normal behaviour. A 3 cm diameter hole was cut through the cup 1 cm below the LED to permit peripheral vision on the right side. The LED used was a Kingbright 7.6 °— 7.6 mm Super Flux LED Lamp L-7676CQBC-D Blued. It has a luminous intensity of 1300 millicandelas when powered by a current of 70 mA. The peak wavelength was 468 nm, which is within the desired range for optimum suppression of melatonin in mammals. The spectral line half width was 25 nm, providing a broad margin for error in terms of the efficacy of the wavelength. The beam angle of the LED was 70° allowing for some degree of movement between the LED and the horse’s eye. Each mask was individually calibrated using different levels of resistance to provide 50 Lux of diffuse light to the horse’s eye. The Lux levels (illuminances) for each individual mask were adjusted and measured using a Lux meter (LX-1010 B Digital Lux Meter). Each mask used 4 Duracell Pro-cell AA sized 1.5 V batteries (replaced at 2-week interval) and powered a circuit containing an Arduinoe board, a switch (on/ off), a clock and a set of resistors. The Arduino board was programmed to turn the LED on at 16.30 h each day and switch it off at 23.00 h every night. A resistor was connected in series with the LED to determine the current flowthat produced illuminance of 50 Lux. In order to save power and prolong the battery lifetime, much of the Arduino functionality was put in a sleep mode. The circuit also included a real time clock module that kept time so that the Arduino could power the LED for specific intervals. The real time clock had its own small, independent battery so that it did not lose time when the switch for the main circuit was turned off. Experimental protocol Beginning on 1 December, Group 1 received light therapy via artificial lighting indoors in individual stalls. The lights, which provided 250 Lux of light to each mare at eye level, were switched on at 16.30 h every day and remained on until 23.00 h each night. Also beginning on 1 December, Group 2 received individual light therapy from head worn masks that provided 50 Lux of blue light to the right eye of each mare. The mask light turned on automatically at 16.30 h each day and turned off at 23.00 h every night. Group 3 served as a control group and received no artificial light therapy, but was exposed to the natural environmental light/dark cycles for the duration of the experiment. Beginning on 20 November and continuing at 2-week intervals throughout the experiment the mares underwent transrectal ultrasound examination and jugular venipuncture. Ovarian activity in terms of follicle number and size, presence or absence of corpora lutea, cervical tone and presence or absence of uterine oedema were recorded for each mare at every ultrasound examination and the blood samples were assayed to establish circulating progesterone concentrations. Oestrous cyclicity was defined as the presence of follicles >20 mm and the confirmation of an ovulation determined by the presence of a previously unrecorded corpus luteum or corpus haemorrhagica on an ovary in conjunction with progesterone levels >1 ng/ml. Transitional phase was defined as follicles >20 mm and associated physiological characteristics typical of oestrous activity but in the absence of progesterone levels indicative of ovulation. Fig 1: A horse wearing the light mask that provided 50 lux blue light to the right eye. The light mask consists of a leather headpiece with a semi-rigid rubber cup containing a single blue-light emitting diode fitted on the inside of the rubber eye cup. The inner surface of the cup is covered with reflective aluminium foil to reflect li