Relationship between Corneal Temperature and Intraocular Pressure in Healthy Individuals: A Clinical Thermographic Analysis

Abstract

Purpose. To study the geographical distribution of corneal temperature (CT) and its influence on the intraocular pressure (IOP) of healthy human volunteers. Materials and Methods. Fifteen subjects (7 M, 8 F), 33.8 ± 17.4 years old, were enrolled in this pilot, cross-sectional study. Measurements of CT were taken after one hour with closed eyelids (CET) or closed eyelids with a cooling mask (cm-CET) and compared to baseline. Results. If compared to baseline, after CET, average CT significantly increased by 0.56°C in the RE and by 0.48°C in the LE (p < 0.001) and IOP concomitantly significantly increased by 1.13 mmHg and 1.46 mmHg, respectively, in each eye (p < 0.001). After cm-CET, average CT significantly decreased by 0.11°C and 0.20°C, respectively, in the RE and LE (RE p = 0.04; LE p = 0.024), followed by a significant IOP decrease of 2.19 mmHg and 1.54 mmHg, respectively, in each eye (RE p < 0.001; LE p = 0.0019). Conclusion. Significant variations of CT occurred after CET and cm-CET and were directly correlated with significant differences of IOP. It can be speculated that both oxidative stress and sympathetic nerve fiber stimulation by temperature oscillations may affect the regulation of AH vortex flow and turnover, thus influencing IOP values.

Plastic modification of the cornea by pneumatic force corrects myopia: Pneumatic keratology

“…By adjusting ambient temperature from 40 to 80°C, the corneal temperature will vary from 37 to 42°C. 16,17 For a given plastic strain of the collagen fibers in the rabbit sclera, the higher the temperature, the greater the strain. 18 The rabbit sclera at 39.5°C permanently strains 1.5% with a stress pressure of only 100 mm Hg.…”

Constructal approach to bio-engineering: the ocular anterior chamber temperature

“…Indeed, biomechanical analyses of the physical properties of the eyes, in particular the cornea, are too complex to obtain a general mechanical model for linking the tissue morphology to their elastic properties and to the flows between the eye and its external environment 11 . The cornea tissue is characterized by the properties of the soft material, in particular 12 13 14 15 16 17 18 19 20 21 22 23 : Heterogeneity in the central-to-peripheral, and anterior-to-posterior dimensions 12 ; Near incompressibility, due to the large amount of water and collagen fibres, with a consequent Poisson’s ratio of the cornea of about 13 0.5; Non-linear constitutive behaviour in relation to the IOP variation 14 ; Viscoelastic and creep behaviour observed in cyclic tests 15 ; Structural anisotropy generated by the oriented collagen fibrils 16 . …”

Contact lenses for continuous corneal temperature monitoring

“…Corneal temperature values of 34 C and above were reported multiple times in literature, in particular as a target threshold for diagnostic purposes. 1,4,17,27,34 Other studies 1,6,49 reported that temperatures in the range 32.0-33.5 C were found across the corneal area. The hysteresis of the sensor was evaluated by temperature swing in the range 33.0 C to 38.0 C, and from 32.0 C to 33.0 C, with a stabilization time of 10 minutes at each 1.0 C step, showing average variations of z8 nm between advancing and receding measurements.…”

“…Liquid crystals embedded in contact lenses were optically characterized, showing a consistent behavior. The readout principle was shown on an ex vivo porcine eye, where readouts were compared with infrared thermal measurements, resulting in an average difference of 0.3 C. Contact lens temperature sensors may be used to monitor dry eye disease (0.5 C decrease), 26 post-corneal transplant infections (1 C increase), 34 IOP modications (0.5 C variations), 17 as well as to monitor ocular temperature variations in individuals for research purposes, to contribute to trace the connes of healthy/unhealthy ocular temperature values, and external factors inuencing the same. Scleral lenses are an attractive device for point-of-care medicine applications, being them used daily by patients suffering from a variety of diseases where corneal temperature monitoring may be desirable.…”

“…1 Ocular temperature was also studied in animal models to develop novel drug delivery systems. 16 The Intra-Ocular Pressure (IOP), 17 corneal elasticity and related refractive properties of the eye 18 were also demonstrated to be related to the temperature of the ocular anterior chamber. Several ocular conditions were reported to be linked to OST variations, resulting from a change in blood ow to the sclera and conjunctiva.…”