Ocular surface heat effects on ocular hemodynamics detected by real-time measuring device

Abstract

Aim: To investigate the ocular hemodynamic effects of applying a hot compress to the eye.

Methods: The right eyes of five New Zealand white rabbits, both male and female, were hot-compressed for 18min. An independently designed novel ocular contact-type temperature measuring device was used to measure the ocular surface temperature before and after the heating. Relevant retrobulbar hemodynamic parameters such as peak systolic velocity (PSV), end diastolic velocity (EDV), and resistance index (RI) of each of the central retinal artery (CRA), long posterior ciliary artery (LPCA), and ophthalmic artery (OA), as well as the mean velocity (V_m) of the central retinal vein (CRV), were measured using a color Doppler flow imaging (CDFI) technique and expressed as mean values with standard deviation (mean±SD). A statistical analysis was conducted based on a paired t-test and the Wilcoxon signed-rank test.

Results: The employed real-time temperature measuring device was able to accurately measure ocular surface temperature during the hot-compress process. The temperature increased after the hot compress was applied. Analysis showed that the PSV and EDV values of the CRA and LPCA significantly increased after the application of the hot compress, as did the V_m of the CRV. There were no significant changes in the EDV of the OA nor the RI of each artery.

Conclusion: This experiment, which is the first of its kind, confirms that the retrobulbar blood flow velocities can increase upon heating the ocular surface. This simple method may be useful in the future.

Keywords: color Doppler flow imaging; ocular hemodynamics; ocular surface heating; temperature detection device.

Figure 1. Novel ocular contact-type temperature measuring device

A: The device consists of five parts: the temperature probe; temperature transmitter; linear power supply; single chip microcomputer; and computer screen; B: The probe in this device is shaped similarly to a contact lens. The surface is smooth, transparent, soft, and exhibits a good fit on the eye.

Figure 2. Measurement of temperature in rabbit eyes

The probe can sense and measure real-time temperature changes at the ocular surface in a noninvasive manner.

Figure 3. In vitro test with ocular temperature measuring device

The temperature of the constant environment is accurately displayed when the probe is repeatedly placed in a thermostatic environment.

Figure 4. In vivo test with ocular temperature measuring device

Once the probe is placed on the surface of the cornea of the New Zealand white rabbit, it can measure the temperature of the ocular surface and eventually stabilizes. The temperature value represents the temperature of the ocular surface.

Figure 5. Real-time temperature curve for continuous hot and cold compresses

The probe can sense the temperature variations of the ocular surface. Upon application of a hot compress, the temperature gradually increases, and eventually stabilizes when the hot compress is removed. Upon application of a cold compress, the eye temperature gradually decreases, eventually stabilizing when the cold compress is removed.

Figure 6. Real-time temperature of the ocular surface before and after application of hot compress

When the heating is applied, the temperature rapidly increases before reaching the maximum temperature and then slowly decreasing. The ocular surface is maintained at the elevated temperature for the duration of the application, 18min.

Figure 7. Contrast between ultrasound images of retrobulbar blood flow before and after application of hot compress

A-D: Ultrasonographic images of the CRA, LPCA, OA, and CRV, respectively, recorded before the hot compress application; E-H: Ultrasonographic images of the CRA, LPCA, OA, and CRV, respectively, after the hot compress application.