Association between dryness sensation and ocular surface temperature and conjunctival blood flow in soft contact lens wearers

PURPOSE

To investigate the association between dryness, ocular surface temperature (OST), and conjunctival blood flow (CBF) in soft contact lens (SCL) wearers after airflow stimulation.

METHODS

After recruiting 21 SCL wearers (mean age, 25.3 ± 4.2 years), subjects used two different daily disposable silicone hydrogel SCLs (narafilcon A and delefilcon A lenses). On three of four measurement days, excluding the first, OST, CBF, tear meniscus height (TMH), and non-invasive tear break-up time (NIBUT) were measured after airflow stimulation at a rate of 3 m/s for 10 min. The measurements were conducted without SCLs on the first and second days, and with different SCLs on the third and fourth days. Dryness was evaluated using the visual analogue scale (VAS). These parameters were compared between the two types of SCLs, and their association with the dryness sensation was then investigated.

RESULTS

Dryness was significantly weakly correlated with OST (r = -0.375, p < 0.05) and CBF (r = 0.339, p < 0.05). TMH, NIBUT, and VAS scores for dryness with the delefilcon A lens (0.15 ± 0.05 mm, 3.7 ± 01.7 s and 29.4 ± 16.9) were significantly higher, longer, and lower, respectively, than those with the narafilcon A lens (0.12 ± 0.05 mm, 2.3 ± 1.7 s and 35.9 ± 17.0; p < 0.05, p < 0.01 and p < 0.01). The changes in the OST and CBF between with and without the delefilcon A lens (-0.36 ± 0.35 °C and 0.99 ± 0.19) were significantly small compared to the narafilcon A lens (-0.60 ± 0.42 °C and 1.11 ± 0.21; p < 0.01 for both comparisons).

CONCLUSION

Dryness was correlated with OST and CBF, which indicates that when dryness was high, OST was low and CBF was high. These results suggest that OST and CBF assessments are effective for evaluating dryness sensation.

Comparing the ocular surface temperature and dry eye condition of keratoconus with normal eyes using infrared thermal imaging

PURPOSE

This study was conducted to compare the ocular surface temperature in keratoconus eyes with that in normal eyes.

METHODS

A total of 27 participants were enrolled, with 10 and 17 participants in the keratoconus and control groups, respectively. Participants in the control group underwent an ophthalmic slit lamp examination and ocular thermography, while an additional corneal tomography was performed for those in the keratoconus group.

RESULTS

For patients with keratoconus, the mean upper eyelid temperature (UET) was 32.36 ± 1.02 °C, inner canthus temperature (ICT) was 34.25 ± 0.83 °C, outer canthus temperature (OCT) was 33.62 ± 0.96 °C, initial central corneal temperature (initial CCT) was 33.04 ± 1.03 °C, sixth-second CCT (6 s-CCT) was 32.67 ± 1.19 °C, and the mean change in CCT measured within 6 s (change in CCT within 6 s) was 0.36 ± 0.26 °C. For controls, the values for UET, ICT, OCT, initial CCT, 6 s-CCT, and change in CCT within 6 s were 32.35 ± 1.13 °C, 34.14 ± 0.91 °C, 33.51 ± 1.02 °C, 33.22 ± 1.01 °C, 32.99 ± 1.01 °C, and 0.22 ± 0.17 °C, respectively. Except for the change in CCT within 6 s (p = 0.022), no significant differences were observed in UET (p = 0.973), ICT (p = 0.659), OCT (p = 0.697), initial CCT (p = 0.556) or 6 s-CCT (p = 0.310) between the two groups.

CONCLUSION

The keratoconus eyes showed faster changes in CCT and evaporation of tear film after opening the eyes. Therefore, the keratoconus eyes had a higher incidence of dry eye conditions.

Nonlinear effects of humidex on risk of outpatient visit for allergic conjunctivitis among children and adolescents in Shanghai, China: A time series analysis

Background

Various epidemiological studies have focused on the adverse health outcomes of meteorological factors. However, there has been little research on the impact of humidex on allergic conjunctivitis, especially in child and adolescent populations. We aimed to explore the impact of humidex, a comprehensive index of relative humidity and temperature, on child and adolescent allergic conjunctivitis admissions.

Methods

Outpatient visit data for allergic conjunctivitis, meteorological factors and air pollutants in Shanghai for the 2017-2022 period were retrieved. For the purpose of analysing the nonlinear connection and lag impact between humidex and admissions for paediatric and adolescent allergic conjunctivitis, the distributed lag nonlinear model (DLNM) was fitted.

Results

A total of 147 090 cases were included in our cohort. We found a significantly nonlinear effect on humidex and allergic conjunctivitis. In the single-day lag pattern, the relative risks (RR) of allergic conjunctivitis were significant at lag 0 (RR = 1.08, 95% confidence interval (CI) = 1.05-1.11) to lag 2 (RR = 1.01, 95% CI = 1.00-1.01), lag 5 (RR = 1.01, 95% CI = 1.00-1.01) to lag 9 (RR = 1.01, 95% CI = 1.00-1.01), and lag 14 (RR = 1.02, 95% CI: 1.01-1.03). In the cumulative-lag day pattern, the RR of allergic conjunctivitis were significant at lag 0-0 (RR = 1.08, 95% CI = 1.05-1.11) to lag 0-14 (RR = 1.21, 95% CI = 1.13-1.28). We found that boys, children aged 7-17 years, and children in the warm season were more vulnerable to humidex. In addition, the highest attributable fraction (AF) and attributable number (AN) of humidex are at lag 0-14 (AF = 0.17, AN = 25 026).

Conclusions

Humidex exposure markedly increased the risk of allergic conjunctivitis, especially in highly high humidex. Appropriate public health management is needed for disease management and early intervention.

Applications of Infrared Thermography in Ophthalmology

Body temperature is one of the key vital signs for determining a disease’s severity, as it reflects the thermal energy generated by an individual’s metabolism. Since the first study on the relationship between body temperature and diseases by Carl Reinhold August Wunderlich at the end of the 19th century, various forms of thermometers have been developed to measure body temperature. Traditionally, methods for measuring temperature can be invasive, semi-invasive, and non-invasive. In recent years, great technological advances have reduced the cost of thermographic cameras, which allowed extending their use. Thermal cameras capture the infrared radiation of the electromagnetic spectrum and process the images to represent the temperature of the object under study through a range of colors, where each color and its hue indicate a previously established temperature. Currently, cameras have a sensitivity that allows them to detect changes in temperature as small as 0.01 °C. Along with its use in other areas of medicine, thermography has been used at the ocular level for more than 50 years. In healthy subjects, the literature reports that the average corneal temperature ranges from 32.9 to 36 °C. One of the possible sources of variability in normal values is age, and other possible sources of variation are gender and external temperature. In addition to the evaluation of healthy subjects, thermography has been used to evaluate its usefulness in various eye diseases, such as Graves’ orbitopathy, and tear duct obstruction for orbital diseases. The ocular surface is the most studied area. Ocular surface temperature is influenced by multiple conditions, one of the most studied being dry eye; other diseases studied include allergic conjunctivitis and pterygium as well as systemic diseases such as carotid artery stenosis. Among the corneal diseases studied are keratoconus, infectious keratitis, corneal graft rejection, the use of scleral or soft contact lenses, and the response to refractive or cataract surgery. Other diseases where thermographic features have been reported are glaucoma, diabetic retinopathy, age-related macular degeneration, retinal vascular occlusions, intraocular tumors as well as scleritis, and other inflammatory eye diseases.

Association between mask-associated dry eye (MADE) and corneal sensations

To determine the risk of mask-associated dry eye (MADE), we investigated the fluorescein tear break-up time (FBUT), ocular surface temperature and blood flow, along with corneal sensitivity, in mask wearers. We enrolled 60 mask wearers (mean age, 27.1 ± 5.2 years) and then measured FBUT, corneal temperature and conjunctival blood flow without wearing masks (no mask), with masks, and with taped masks. We defined MADE as the condition in which dry eye symptoms appeared and the FBUT with mask was less than 5 s. The FBUT with a mask was significantly shorter compared to the no mask and taped mask groups (P < 0.01 and P < 0.05). The corneal temperature difference and conjunctival blood flow difference were significantly higher after wearing a mask than after wearing a taped mask (P < 0.01). Of the 60 subjects, 13 were diagnosed with MADE. Pain sensitivity and the Ocular Surface Disease Index (P < 0.05 and P < 0.01) were significantly higher in the MADE group, with the FBUT without masks (P < 0.05) significantly shorter than in the non-MADE group. MADE may be associated with corneal hypersensitivity. Wearing masks decreased FBUT and increased ocular surface temperature and blood flow. Taping the top edge of masks prevented these changes. Fitting masks properly may reduce MADE risk.

Objective evaluation of allergic conjunctival disease (with a focus on the application of artificial intelligence technology)

We have summarized the past efforts and results of objective measurement methods for conjunctival hyperemia classification. Severity classification using conjunctival blood vessel occupancy rate, ocular surface temperature analysis, and artificial intelligence have been reported to be clinically useful, as they have been found to correlate with the severity of conjunctival hyperemia by doctors. The AI method using slit lamp microscope images, whose main purpose is to be widely used in daily clinical practice, can be spread all over the world. As a result, it may lay the foundation for clinical research using large amounts of clinical data collected on the same basis without human bias.

Correlation between Blood Flow and Temperature of the Ocular Anterior Segment in Normal Subjects

Purpose: To determine a correlation between temperature and blood flow in the ocular anterior segment, and their effects on corneal temperature. Methods: In experiment 1, we recruited 40 eyes and measured the temperature and blood flow in the ocular anterior-segment (upper/lower eyelid skin, palpebral and bulbar conjunctiva, and cornea) before and after application of warm compresses. In experiment 2, we recruited 20 eyes and measured the same tissues before and during stimulation using water and capsaicin solution in the oral cavity. Results: In experiment 1, the temperatures of the upper/lower eyelid skin and cornea increased significantly until 15 min after the application of the warm compress; the temperatures of the palpebral and bulbar conjunctiva increased significantly until 10 min. The blood flow in the upper/lower eyelid skin and bulbar conjunctiva increased significantly until 10 min, and that of the palpebral conjunctiva increased significantly until 15 min. In experiment 2, the temperatures were correlated significantly with the blood flow in the upper and lower eyelid skin and palpebral and bulbar conjunctiva. The temperature of all locations and palpebral conjunctival blood flow contributed independently to the corneal temperature. Conclusions: In the ocular anterior segment, the temperature and blood flow were correlated significantly, and contributed to the corneal temperature.

Correlation between Corneal Endothelial Cell Density and Central Ocular Surface Temperature in Normal and Keratoconus Eyes

PURPOSE

In keratoconus (KC), an increase of the corneal back surface area may result in endothelial cell density (ECD) decrease and an increase of the corneal front surface area in ocular surface temperature (OST) decrease due to increased heat dissipation. Along with these hypotheses, we aimed to analyse the correlation between ECD and central corneal OST in patients with KC and healthy controls.

PATIENTS AND METHODS

A total of 154 eyes with KC (mean age 36.1 ± 12.5 years) and 92 healthy eyes (mean age 36.4 ± 12.8 years) were examined. Corneal front and back surface area at the central 5 mm corneal diameter (FSA and BSA) were calculated based on Pentacam measurement data:FSA or BSA = 2×3.14×R(R-√R²-D/2)²,where R referred to corneal front or back surface radius of curvature and D to the corneal front or back surface diameter (5 mm for the present study), respectively.ECD was determined by specular microscopy (EM-3000) and central corneal OST by thermography (TG-1000).

RESULTS

ECD was significantly lower in KC (2498 ± 356/mm²) patients than in controls (2638 ± 294/mm²; p < .001). FSA (20.35 ± 0.26 mm² vs. 20.17 ± 0.03 mm²) and BSA (20.84 ± 0.58 mm² vs. 20.45 ± 0.08 mm²) were significantly higher in KC patients than in controls (p = .001; p < .001), but the average central corneal OST did not differ significantly between both groups (34.2 ± 0.6°C vs.34.3 ± 0.7°C; p = .62). OST at the corneal centre correlated weakly, positively with ECD (r = 0.2; p < .05), but OST did not correlate with FSA (r = 0.045) or BSA (r = 0.064).

CONCLUSIONS

Endothelial cell density seems to have a mild impact on central ocular surface temperature in keratoconus and normal subjects. This effect is not correlated to the corneal front or back surface area.

Ocular Surface Disease Index and Ocular Thermography in Keratoconus Patients

Purpose

Keratoconus (KC) has been defined as a “noninflammatory” corneal disease, but recent studies have noted a potential inflammatory origin. We analysed the Ocular Surface Disease Index (OSDI) and ocular surface temperature (OST) in KC patients compared to controls. Patients and Methods. A total of 179 eyes in 90 patients with KC (topographic keratoconus classification 0-1 to 4, age 36.1 ± 12.5 years, 65.9% males) and 82 eyes in 41 controls (age 36.4 ± 12.8 years, 47.6% males) were examined. The participants completed the OSDI questionnaire and underwent corneal topography, tomography, and thermography. Additional outcome measures were vision- and discomfort-related OSDI subscores and mean OST  at the corneal centre during 10 seconds of sustained eye opening after blinking.

Results

The OSDI score (31.4 ± 22.4 vs. 17.5 ± 17.9) and vision- (17.7 ± 14.6 vs. 10.5 ± 13.2) and discomfort-related (14.3 ± 10.7 vs. 9.4 ± 10.5) OSDI subscores were significantly higher in KC patients than in controls (p < 0.001). We found no significant difference in the central corneal OST (34.2 ± 0.6°C vs. 34.2 ± 0.7°C; p < 0.001). We found no significant difference in the central corneal OST (34.2 ± 0.6°C vs. 34.2 ± 0.7°C; p < 0.001). We found no significant difference in the central corneal OST (34.2 ± 0.6°C vs. 34.2 ± 0.7°C; r > 0.174, p < 0.001). We found no significant difference in the central corneal OST (34.2 ± 0.6°C vs. 34.2 ± 0.7°C; r > 0.174, r > 0.174,

Conclusion

KC patients had increased OSDI scores and vision- and discomfort-related OSDI subscores without an increase in the OST compared to a normal population. OSDI score/subscores weakly correlate with SAI and SRI but do not correlate with OST in KC patients or controls. Vision- and discomfort-related symptoms of KC have to be managed in parallel in ophthalmological practice, but the necessity of anti-inflammatory treatment cannot be verified through ocular thermography.

Association among Blink Rate, Changes in Ocular Surface Temperature, Tear Film Stability, and Functional Visual Acuity in Patients after Cataract Surgery

Purpose

To investigate the association among the ocular surface temperature (OST), tear film stability, functional visual acuity (FVA), and blink rate in patients after cataract surgery.

Methods

We recruited 98 eyes of 69 patients (mean age, 73.7 ± 5.2 years) 1 month after phacoemulsification with implantation of acrylic intraocular lenses and assessed slit-lamp microscopy, corrected distance VA, FVA, noninvasive tear breakup time (NIBUT), and OST. We defined the changes in the OST from 0 to 10 seconds after eye opening as the ΔOST. We measured the FVA and blink rate using the FVA measurement system. We divided the patients into two groups based on tear film stability: stable tear film (NIBUT, >5.0 seconds) and unstable tear film (NIBUT, ≤5.0 seconds). We evaluated the differences between the two groups and the association between the blink rate and other clinical parameters.

Results

The unstable tear film group (56 eyes) had significantly (p < 0.0001, unpaired t-test) shorter NIBUTs than the stable tear film group (42 eyes). The ΔOSTs and blink rates were significantly (p < 0.0001) higher in the unstable tear film group than in the stable group. Linear single regression analysis showed that the ΔOST (r = −0.430, p < 0.0001), NIBUT (r = −0.392, p < 0.0001), and gender (r = −0.370, p=0.0002) were correlated significantly with the blink rate. Multiple regression analysis showed that the ΔOST independently contributed to the blink rate.

Conclusions

The frequency of blinks is associated with tear film stability in patients after cataract surgery. The blink rate may be useful for evaluating the tear film stability in clinical practice. The ΔOST should be an important contributing factor to the blink rate. [This trial is registered with UMIN000026970].

Assessment of Phosphate and Osmolarity Levels in Chronically Administered Eye Drops

Objectives

To assess phosphate and osmolarity levels of chronically administered eye drops commercially available in Turkey.

Materials and Methods

A total of 53 topical eye drops including 18 antiglaucoma drugs, 4 nonsteroidal anti-inflammatory drugs (NSAIDs), 10 corticosteroids, 7 antihistaminics, and 14 artificial tears identified using the Vademecum Modern Medications Guideline (2018) were included in the study. Phosphate levels were assessed using Roche Cobas C501 analyzer (Roche Diagnostics GmbH, Mannheim, Germany) and the respective kits. Osmolarity was assessed using Vescor Vapro 5600 vapor pressure osmometer (Sanova Medical Systems, Vienna, Austria). Mean phosphate and osmolarity levels were obtained after averaging three measurements. Eye drops were categorized as isoosmolar, hypoosmolar and hyperosmolar based on physiologic tear osmolarity range (296.5±9.8 mOsm/L).

Results

The highest phosphate concentration was found in the antiglaucoma group (20.3±35.4 mmol/L), followed by antihistaminics (17.3±17.9 mmol/L), corticosteroids (15.2±19.1 mmol/L), artificial tears (0.8±1.0), and NSAIDs (0.04±0.08). Percentage of medications in the hyperosmolar category was highest in the NSAI group (75%), followed by antihistaminics (43%), corticosteroids (20%), and antiglaucoma drugs (19%). Nearly all of the artificial tear formulations were in the hypoosmolar (71%) or isoosmolar (21%) categories.

Conclusion

Approximately 40% of glaucoma medications and approximately 60% of corticosteroid and antihistaminic medications had a phosphate concentration higher than the physiologic tear phosphate level (1.45 mmol/L).

Airway Resistance in Patients with Obstructive Sleep Apnea Syndrome Following Robotic Prostatectomy

BACKGROUND

Because minimally invasive surgery can improve postoperative recovery, it became the preferred technique for patients with significant comorbidities. However, steep Trendelenburg position and abdominal CO₂-insufflation can lead to a significant increase in upper airway resistance and an alteration of overall lung function. In particular, patients who already suffer from an obstructive airway disease like obstructive sleep apnea syndrome (OSAS) might be at risk for postoperative airway complications. Therefore, we perioperatively performed spirometric tests in patients with OSAS undergoing robotic surgery in steep Trendelenburg position.

METHODS

Twenty patients with OSAS were enrolled in the study. A day before surgery lung function measurements were performed and repeated preoperatively, 40, 120, and 240 minutes and 1 and 5 days postoperatively. We measured vital capacity (VC), forced expiratory volume in 1 second (FEV1), maximal mid expiratory and inspiratory flow (MEF50, MIF50), arterial oxygen saturation, and nasal flow.

RESULTS

The ratio of MEF50 to MIF50, as an indicator of upper airway resistance, was increased significantly postoperatively and normalized within 24 hours (p < 0.0001), while FEV1 and VC were significantly reduced and recovered only partially as much as the fifth postoperative day (p < 0.0001).

CONCLUSION

Airway resistance increased following robotic radical prostatectomy in Trendelenburg position in patients with OSAS. Two separate major effects can be observed. A significant increase of the upper airway resistance, which improved to preoperative conditions within 24 hours, and a reduction in FEV1 and VC, which recovered only partially as much as the fifth postoperative day.

[Use of infrared thermography in ophthalmology]

Thermoregulation disorders are associated with Body temperature fluctuation. Both hyper- and hypothermia are evidence of an ongoing pathological process. Contralateral symmetry in the Body heat spread is considered normal, while asymmetry, if above a certain level, implies an underlying pathology. Infrared thermography (IRT) is employed in many medical fields including ophthalmology. The earliest attempts of eye surface temperature evaluation were made in the 19^th century. Over the last 50 years, different authors have been using this method to assess ocular adnexa, however, the technique remains insufficiently studied. The reported IRT data is often contradictory, which may be due to heterogeneity (in terms of severity) of patient groups and disparities between research parameters.

[Interobserver and intraobserver reliability of corneal surface temperature measurements with the TG-1000 thermograph in normal eyes]

PURPOSE

The aim of this study was to analyze the reliability of temperature measurements with the ocular TG-1000 thermograph in a setup of sequential measurements performed by one observer (intraobserver) and a sequence of measurements performed by different observers (interobserver) in normal subjects without pathologies of the anterior segment of the eye.

PATIENTS AND METHODS

A total of 50 right eyes from 50 individuals (mean age 29.1 ± 7.9 years) without ocular pathologies or history of ocular surgery were enrolled in this prospective monocentric clinical case series. Eyes with signs of dry eye syndrome (based on a positive McMonnies questionnaire) were excluded from the study. Corneal surface temperature measurements were performed by three examiners to assess interobserver reliability. In addition, in a subgroup of 22 individuals, a sequence of 3 measurements were performed by 1 of the examiners to examine intraobserver reliability. Corneal surface temperature was measured within an interval of 10 s (11 frames) on a region of interest of 16 ± 12 mm (320 ± 240 pixels). Central and mid-peripheral local temperatures at 3 mm (3, 6, 9 and 12 o'clock) were extracted and analyzed from the raw data.

RESULTS

The ocular TG-1000 thermograph yielded consistent results for the interobserver as well as intraobserver conditions in measuring corneal surface temperature in the center as well as mid-periphery of the cornea. Cronbach's alpha was 0.9 or higher at all corneal locations, which proves a high consistency of results for the interobserver and intraobserver measurements. The average corneal surface temperature ranged between 34.0 °C and 34.7 °C with a slight decrease from the upper temporal (9 and 12 o'clock) to the lower nasal (3 and 6 o'clock) quadrants.

CONCLUSION

The TG-1000 thermograph yielded consistent results of corneal surface temperature in individuals without anterior segment pathologies or history of ocular surgery. With the option of raw data export (11 frames within 10 s with a lateral resolution of 320 × 240 pixels) the thermograph offers a wide range of new diagnostic options for a spatiotemporal analysis of corneal surface temperature.