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Infrared (IR) thermographic assessment of ocular surface temperature (OST) is gaining interest as an adjuvant method to evaluate the ocular surface. It is a quick, non-invasive test that causes minimal, if any, discomfort to patients. The purpose of this article was to summarize research on how OST relates to tear film parameters and dry eye disease (DED). PubMed, Google Scholar, and Scopus searches for specific terms were carried out and eligible articles reviewed. OST of the central cornea is ~34-35°C when measured as a single time-point (typically right after a blink). Dynamically, OST values decrease over time at a rate of ~ −0.01 °C/s in healthy eyes. Single time-point OST values are impacted by temperature, with positive correlations noted with both ambient (1°C↓ results in ~0.16°C↓ in OST) and body (1°C↑ results in ~0.98°C↑ in OST) temperature. Single time-point OST values are also impacted by tear parameters, with negative correlations noted with tear break-up time (TBUT; r=−0.61) and positive correlations with lipid layer thickness (~r=0.50). Dynamically, the rate of OST cooling over the interblink period correlates with various tear parameters including Schirmer’s test scores (r=−0.39), tear meniscus height (r=−0.52) and the rate of tear film break-up (r=−0.74). These data imply that OST decreases more rapidly in individuals with greater tear production, larger tear volumes, and shorter tear break-up times (faster rates of tear film break-up). There are discrepancies in relationships between OST and DED across studies, which is not surprising given that DED encompasses a number of different phenotypic presentations. However, most studies found that OST decreases at a more rapid rate in DED vs. control groups. As such, cooling rate may have utility as a screening tool in DED in combination with established point-of-care tests.

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.

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=0.41) between the two groups (p≥0.22). The OSDI score and subscores poorly to fairly correlated with the surface asymmetry index (SAI) and surface regularity index (SRI;r > 0.174,p<0.005), but did not correlate with the central corneal OST (r r ≥ −0.086).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.

Aim of study: To assess the potential of using infrared ocular thermography (IROT) as a tool to predict beef quality at the slaughterhouse.Area of study: The study was carried out in the Salteras’s slaughterhouse (Seville, Spain).Material and methods: Ocular temperature images were captured from 175 lean young bulls prior to slaughter. Carcasses were classified into three groups according to weight: ˂250 kg, 250-310 kg and ˃310 kg. IROT was measured just before slaughter and pH was measured 24 h later. Colour parameters (CIELAB space) were evaluated 48 h post-slaughter. Water holding capacity was evaluated at seven days after slaughter.Main results: IROT mean values were higher in heavier bulls (p

Imaging has become indispensable in the diagnosis and management of diseases in the posterior part of the eye. In recent years, imaging techniques for the anterior segment are also gaining importance and are nowadays routinely used in clinical practice. Ocular surface disease is often synonymous with dry eye disease, but also refers to other conditions of the ocular surface, such as Meibomian gland dysfunction or keratitis and conjunctivitis with different underlying causes, i.e., allergies or infections. Therefore, correct differential diagnosis and treatment of ocular surface diseases is crucial, for which imaging can be a helpful tool. A variety of imaging techniques have been introduced to study the ocular surface, such as anterior segment optical coherence tomography, in vivo confocal microscopy, or non-contact meibography. The present review provides an overview on how these techniques can be used in the diagnosis and management of ocular surface disease and compares them to clinical standard methods such as slit lamp examination or staining of the cornea or conjunctiva. Although being more cost-intensive in the short term, in the long term, the use of ocular imaging can lead to more individualized diagnoses and treatment decisions, which in turn are beneficial for affected patients as well as for the healthcare system. In addition, imaging is more objective and provides good documentation, leading to an improvement in patient follow-up and education. Published version This research was funded by the Medical Scientific Fund of the Mayor of the City of Vienna, Project No. 17059.

Corneal transplant rejection is one of the most frequent complications, with a reported incidence of 16–30%. In our current research, we investigated the use of infrared thermography to detect ocular surface temperature. We also looked at a case of corneal transplant rejection and this case had an elevated ocular surface temperature when compared to the contralateral eye and other eyes without corneal transplant rejection. Twenty-three eyes of twelve patients would serve as control to one eye with clinically evident corneal transplant graft rejection. A Flir T400 320 × 240 pixel, digital thermal camera was used to take a digital photograph and an infrared photograph of each eye. The images were analyzed with the Flir web viewer. We present here a case of corneal transplant rejection documented with both slit lamp photos as well as infrared and corneal surface photos. The studied patient’s unaffected eye, and the control group’s trends did indeed bring the expected results and proved thermal imagery in this particular field a viable examination method. We feel that ocular thermography is a useful adjunctive diagnostic tool and that it may be useful to monitor routine corneal transplant patients. Further research into the temperature changes of corneal transplant patients is needed and may allow for earlier intervention for graft rejection.

Purpose To evaluate the efficacy of infrared (IR) ocular thermography in screening for dry eye disease (DED). Methods IR ocular thermography was performed on 62 dry eye and 63 age- and sex-matched control subjects. Marking of ocular surface and temperature acquisition was done using a novel ‘diamond’ demarcation method. 30 static- and 30 dynamic-metrics were studied and receiver operating characteristic curves were plotted. Efficacy of the temperature metrics in detecting DED were evaluated singly and in combination in terms of their area under the curve (AUC), Youden’s index and discrimination power (DP). Results Absolute temperature of the extreme nasal conjunctiva 5 s and 10 s after eye opening were best detectors for DED. With threshold value for the first metric set at 34.7 °C, sensitivity and specificity was 87.1% (95% CI: 76.2–94.3%) and 50.8% (95% CI: 37.9–63.6%) respectively. With threshold value for the second metric set at 34.5 °C, sensitivity and specificity was 77.6% (95% CI: 64.7–87.5%) and 61.9% (95% CI: 48.8–73.9%) respectively. The two metrics had moderate accuracy and limited performances with AUC of 72% (95% CI: 63–81%) and 73% (95% CI: 64–82%); Youden index of about 0.4 and DP of 1.07 and 1.05 respectively. None of the dynamic metrics was good detector for DED. Combining metrics was not able to increase the AUC. Conclusions This work suggests some utility for the application of IR ocular thermography for evaluation of dry eye patients.

Purpose To investigate the inter-image, inter-occasion and inter-examiner repeatability of NEC infrared thermo-tracer TH 9260 in assessing healthy and dry eyes. Methods Ocular surface temperature (OST) was recorded using NEC infrared thermo-tracer TH 9260 on 21 healthy and 15 dry eyes. Data from the right eyes were analyzed. Marking of the ocular surface and OST acquisition was performed using a new ‘diamond’ demarcation method. Twelve OST indices were obtained at three different time points following a blink: 0 s, 5 s and 10 s. Inter-image, inter-occasion and inter-examiner repeatability of the infrared ocular thermography was evaluated by calculating coefficients of repeatability (COR). Results Ten out of the twelve tested OST indices had good repeatability with small inter-image variability (%COR: 0.2–0.9), inter-occasion variability (%COR: 2.1–3.7) and inter-examiner variability (%COR: 1.5–3.7) for the three studied time points. Two of the OST indices (temperature standard deviation of the region of interest and radial temperature difference) had poor repeatability with much larger inter-image variability (%COR: 8.9–140.7), inter-occasion variability (%COR: 47.5–153.5) and inter-examiner variability (%COR: 54.7–142.0) for the three studied time points. Conclusions Most of the metrics adopted in this assessment can be considered to be highly repeatable.

OBJECTIVE It is understood that the ability to measure ocular temperature accurately will increase understanding of ocular physiology and should be a support in decision-making in classical diagnostic procedures. The use of ocular thermography offers great opportunities for monitoring the temperature of the anterior eye and analyzing the effects of certain pathologies on ocular surface temperature (OST). The aim of the present work is to measure the OST of 220 healthy normal subjects, stratified according to gender and age, in order to obtain a normal temperature distribution to be used as reference values when comparing healthy versus pathological conditions. APPROACH The OST is measured from five regions, located over the whole area of the anterior eye, which correspond to particular anatomic structures, through a semi-automated procedure to post-process the infrared images. The relationship between OST and independent variables (forehead skin temperature, age, gender, level of physical activity, cardiovascular risk factors including sedentary lifestyle and smoking, laboratory temperature, and laboratory humidity) was investigated through linear regression models. MAIN RESULTS The OSTs measured from the five different ocular regions are statistically different (p -value

Objective In recent decades infrared thermography (IRT) has facilitated accurate quantitative measurements of the ocular surface temperature (OST), applying a non-invasive procedure. The objective of this work was to develop a procedure based on IRT, which allows characterizing of the cooling of the ocular surface of patients suffering from dry eye syndrome, and distinguishing among patients suffering from aqueous deficient dry eye (ADDE) and evaporative dry eyes (EDE). Approach All patients examined (34 females and 4 males, 23-84 years) were divided into two groups according to their Schirmer I result (⩽ 7 mm for ADDE and > 7 mm for EDE), and the OST was recorded for 7 s at 30 Hz. For each acquisition, the temperatures of the central cornea (CC) as well as those of both temporal and nasal canthi were investigated. Main results Findings showed that the maximum temperature variation (up to 0.75 ± 0.29 °C) was at the CC for both groups. Furthermore, patients suffering from EDE tended to have a higher initial OST than those with ADDE, explained by the greater quantity of the tear film, evenly distributed over the entire ocular surface, keeping the OST higher initially. Results also showed that EDE patients had an average cooling rate higher than those suffering from ADDE, confirming the excessive evaporation of the tear film. Significance Ocular thermography paves the way to become an effective tool for differentiating between the two different etiologies of dry eye syndrome.

Ocular thermography is an important, emerging modality in the diagnosis and management of diseases related to eye. It is a non-invasive procedure to evaluate the presence of eye diseases and monitor the response to treatments. In this paper, we propose and evaluate a system designed using infrared thermal image processing that detects glaucoma. Euclidean distance based segmentation technique is used to threshold the IR image to obtain the region of interest, where the manifestation of glaucoma is predominant. Features are extracted using statistical moments from the temperature mapped IR image and Gray Level Co-Occurrence Matrix of the IR image. Two significant attributes, namely the homogeneity and area of region of interest are the inputs to a Support Vector Machine classifier to classify a given input ocular thermal image as a normal or diseased image. In our simulation study, one hundred ocular thermal images with even number of normal and diseased subjects were analysed. The classifier has achieved a maximum accuracy of 96% when homogeneity and area of region of interest are used as attributes, indicating the potential use of proposed method for screening patients even at early stages of glaucoma.

The focus of this research is the investigation of the Ocular Surface Temperature (OST) in both healthy and pathological (e.g. age-related macular degeneration, eye dry syndrome and choroidal lesions) eyes by using Infrared Thermography (IR). Specifically, the temperature of different anatomical areas (or points) of the eye is measured by applying image processing procedures on the infrared images recorded. It is known that the pathogenesis of some ocular pathology is related to the variation of ocular blood perfusion, and thus to the temperatures of the anterior segment of the eye. Results demonstrated that thermography can provide quantitative documentation of these temperature measurements. Furthermore, thermography is a non-invasive, cheap, harmless and portable technique. The challenge is to make ocular thermography part of the daily diagnostic procedure by providing more and more reliable experimental data.

Obstructive meibomian gland dysfunction (MGD) frequently induces a chronic complaint with various symptoms related to dry eye and discomfort. Previous research indicates a pivotal role for heat therapy for melting the meibum as part of any successful management plan, but delivery of constant temperature during treatment is vital. This study evaluated the performance of a novel device designed to deliver controlled, latent, moist heat to the eyelids and surrounding area.The signs, symptoms and ocular temperature of 25 normal subjects (M8, F17; age 29.2±5.7 years) were recorded before and after a 10min application of the Blephasteam(®) device. Ocular temperature (non-invasive ocular thermography; A40 Flir, UK), tear film stability (NIBUT), intra-ocular pressure (IOP), and ocular surface staining and hyperaemia were recorded. Results were checked for normality and compared using paired t-tests.Temperatures in both eyelids were significantly greater after device application (upper +1.7±0.9°C; lower +2.1±0.7°C, p0.0005). Bulbar conjunctival hyperaemia significantly decreased after treatment (p0.005), but limbal and palpebral hyperaemia remained similar (p=0.33 and p=0.11, respectively). Ocular surface staining (p=0.74) and tear film stability (p=0.12) were unchanged in this normal cohort, and there was no significant change in IOP (13.8±2.0mmHg vs 12.9±2.2mmHg; p=0.092).The Blephasteam(®) device provides effective levels of warming that would be sufficient to melt meibum, and no adverse ocular responses were recorded in this cohort, indicating that this is a safe device. Interestingly, even in this normal cohort, ocular surface redness appears less after treatment.

Infrared thermography was used to measure temperature differences of the corneal surface between nasal and temporal limbus regions and central cornea of normal dogs and dogs with keratoconjunctivitis sicca (KCS), in order to establish temperature values in normal canine eyes and in patients with decreased Schirmer tear tests (STT) values. Dogs investigated were all either patients seen at the Veterinary Teaching Hospital of Federal University of Parana or normal dogs that belonged to the same institution. STT were performed in all eyes. A total of 40 control eyes (STT ≥15 mm/min) and 20 eyes with low STT values (STT ≤14 mm/min) were examined. The mean STT value for eyes with normal STT values was 22.9 ± 3.9 mm/min (mean ± standard deviation), and the mean STT value for eyes with low STT value was 7.2 ± 4.8 mm/min. The mean corneal temperature was significantly lower in eyes with low STT values than in control eyes (P < 0.0001). The following significant correlations were found: (i) Schirmer and breakup time (BUT) (P = 0.0001, r = 0.5); (ii) STT values and corneal surface temperature (P = 0.001, r = 0.256); (iii) STT values and age (P = 0.0001, r = -0.448); (iv) age and corneal surface temperature (P = 0.0001, r = -0.281); and (v) BUT and corneal surface temperature (P = 0.0001, r = 0.36). Thermography is a method that can differentiate between eyes with normal and abnormal STT values. In the future, thermography might be incorporated as part of the ophthalmic examination and perhaps become a popular ancillary test for the diagnoses of ocular surface disorders.

In this paper we propose a methodology for early detection and recognition of Glaucoma in ocular thermographs. Ocular thermography is an efficient tool not only to capture temperatures of corneal surface, but also to detect and visualize any changes on the Ocular surface temperature. The proposed method uses a linear transformation for pre-processing. Logistic Regression based classifier with the features collected from GLCM is used to classify the given ocular IR thermal image into Glaucoma from the normal eye. The efficacy of the proposed technique is proved over a number of ocular thermal image samples.

Purpose To investigate the accuracy and sensitivity of the Thermo-Tracer TH9100MV, NEC San-ei in monitoring the temperature of the anterior eye surface and to establish an inter-subjects ocular surface temperature (OST) norm in Chinese young adults. Methods A blackbody with fixed temperature was used to study accuracy and sensitivity of the thermal camera used (Thermo-Tracer TH9100MV, NEC San-ei). Sixty healthy Chinese young adults aged 17–21 (mean age 19) were recruited from the Singapore Polytechnic Optometry Centre. A room with standard room temperature and humidity was used. Subjects were adapted to the room conditions for 20 min before measurement. OST was then measured within 4–5 s after a blink and with their upper lid lifted by a cotton bud, using infrared thermo-camera, in a non-invasive manner. Results All future Thermo-Tracer readings could be converted to ‘true’ temperature via the regression equation derived y = 1.0884x − 3.4026 (r2 = 0.9985), where y is the ‘true’ temperature and x is reading by Thermo-Tracer. Sensitivity of the machine for all 16 temperatures studied was found to be 91.3%. Mean OST for the population studied was 34.70 ± 0.50 °C. Mean OST at geometrical centre cornea (GCC) was 34.39 ± 0.47 °C and inter-ocular temperature difference was ∼0.20 ± 0.15 °C. Both the horizontal and vertical OST profile was established. No significant differences between right/left eyes and between genders were found at 95% CI. Conclusions Findings on the accuracy can be used as a reference by researchers who are using the same infrared thermal camera. It is proven that the machine has high sensitivity in determining the temperature of anterior ocular surface. Methodology used in this study can also be applied to the determination of the accuracy and sensitivity of the dynamic range for other infrared thermal cameras. Inter-subjects OST norm in Chinese young adults aged 17–21 was established.

Infrared thermography (IRT) body temperature readings were taken in the ocular region of 258 pigs immediately before slaughter. Levels of lactate were measured in blood taken in the restrainer. Meat quality was assessed in the longissimus dorsi (LD), semimembranosus (SM), and adductor muscles. Ocular IRT (IROT) temperature was correlated with blood lactate levels ( r = 0.20; P = 0.001), with pH taken 1 hour postmortem (pH1: r = − 0.18; P = 0.03) and drip loss ( r = 0.20; P = 0.02) in the LD muscle, and with pH1 in the SM muscle ( r = − 0.20; P = 0.02). Potentially, IROT may be a useful tool to assess the physiological conditions of pigs at slaughter and predict the variation of important meat quality traits. However, the magnitude of the correlations is rather low, so a further development of image capture technique and further studies under more variable preslaughter conditions ensuring a larger pork quality variation are needed.

Purpose To investigate the routine use and applicability of a new ocular thermography device (TG 1000; Tomey Corp, Nagoya, Japan) in healthy individuals. Methods Sixty eyes of 30 healthy subjects were included in this prospective study. Intraobserver reproducibility was tested with an ocular surface-oriented infrared radiation thermographic device in a non-contact manner. Using a standard examination protocol, the ocular surface temperature was assessed by dynamic thermal imaging over a time period of 10 s. The procedure was repeated three times during a single session by one examiner. Intraclass correlation coefficients (ICC) were calculated. Results Ocular surface temperature measurements were highly reproducible. The mean ocular surface temperature was 34.02°C ± 0.22. The ICC was 0.947%, 0.949%, and 0.955% for minimum, maximum, and mean temperatures, respectively. Conclusion Ocular surface temperature measurements made using the Tomey TG 1000 in healthy subjects showed excellent intraobserver reproducibility. This novel non-invasive technique offers new options for increased understanding of the physiology of the ocular surface.

This review summarizes basic research in orbital and oculoplastic surgery during the past year. Innovative and exciting projects have been undertaken elucidating microscopic anatomy of the orbital septum, orbital lymphatics, and levator elastic fiber network. Eyelid anatomy as assessed by magnetic resonance imaging has been beautifully demonstrated. In the realm of orbital disease, several studies have provided potential alternative therapeutic modalities in the management of the anophthalmic socket. These particular studies range from the use of demineralized bone in the rabbit anophthalmic socket, to the use of bone graft to reconstruct the monkey orbital floor. Further elegant studies outline the velocity of ophthalmic artery flow, and potential applications of ocular thermography.

Thermography is an investigative technique which allows rapid color-coded display of the temperature across a wide surface by means of infrared detection. We describe an ocular thermographic study of a normal population and present case studies describing the application of this technique for patients with ocular disease. We found that 95% of the normal population have an interocular temperature difference (temperature of center of right cornea minus temperature of center of left cornea) of 0.60 degrees or less. There appears to be a greater difference in temperature between the limbus and the center of the cornea in patients with dry eyes. This technique has potential for evaluating tear film disorders and inflammatory conditions, for monitoring the progress of such conditions, and for evaluating the efficacy of various treatments.

Purpose Heat therapy is the standard treatment regime for obstructive meibomian gland dysfunction (MGD). Research has shown the melting point of the meibum is raised to 35C in MGD compared to 32C in normal subjects, and sustained heat delivery is essential in effective treatments. This study was designed to evaluate the changes in ocular surface signs and temperature efficacy of a novel device which delivers latent moist heat to the eye lids and surrounding area for 10 minutes. Methods A prospective, controlled, single intervention trial recruited 25 normal subjects (M8, F17; age 29.2±5.7yrs). Ocular temperature, tear film stability, ocular hyperaemia and surface staining were measured, using non-invasive ocular thermography and Efron grading respectively,, before and after device application. Results were checked for normality and compared using paired t-testing. Results Temperature significantly increased to effective levels in both the upper (37.7±0.58C; p

PURPOSE. To examine the relation between ocular surface temperature (OST) assessed by dynamic thermal imaging and physical parameters of the anterior eye in normal subjects. METHODS. Dynamic ocular thermography (ThermoTracer 7102MX) was used to record body temperature and continuous ocular surface temperature for 8 s after a blink in the right eyes of 25 subjects. Corneal thickness, corneal curvature, and anterior chamber depth (ACD) were assessed using Orbscan II; noninvasive tear break-up time (NIBUT) was assessed using the tearscope; slit lamp photography was used to record tear meniscus height (TMH) and objective bulbar redness. RESULTS. Initial OST after a blink was significantly correlated only with body temperature (r = 0.80, p < 0.0005), NIBUT (r = -0.68, p < 0.005) and corneal curvature (r = -0.40, p = 0.05). A regression model containing all the variables accounted for 70% (p = 0.002) of the variance in OST, of which NIBUT (29%, p = 0.004), and body temperature (18%, p = 0.005) contributed significantly. CONCLUSIONS. The results support previous theoretical models that OST radiation is principally related to the tear film; and demonstrate that it is less related to other characteristics such as corneal thickness, corneal curvature, and anterior chamber depth. © 2007 American Academy of Optometry.

Excision of arteriovenous malformations (AVMs) is known to carry a risk of postoperative hemorrhage, postulated to be the result of normal perfusion pressure breakthrough. It is also possible that AVMs may cause a steal effect, reducing perfusion in nearby vessels. There is currently no simple method of visualizing the presence or absence of steal effect intraoperatively. We hypothesized that the infrared thermographic (heat sensitive) imaging of perilesional brain may be useful for detecting reduced perfusion due to steal. Moreover, we hypothesized that if steal effect was present, it could impact on ocular perfusion and thereby temperature. Our objective was, therefore, to investigate whether perilesional cortical and ocular temperature (OT) may be a marker of steal effect. We intraoperatively acquired conventional and thermal images of the surgical field and eyes bilaterally, pre- and post-excisions of a large left hemisphere AVM. We found OT asymmetry preoperatively, which was absent after the AVM was excised. Intraoperative thermal images showed an increase of perilesional temperature, although this could be confounded by generalized changes in cortical perfusion due to anesthetics or surgery.

Infrared ocular thermograms were recorded for a group of 36 dry eye patients and for 27 age- and sex-matched controls. Mean ocular surface temperature was greater in the dry eye group (32.38 +/- 0.69 degrees C) compared with the control group (31.94 +/- 0.54 degrees C; p < 0.01). In addition, there was a greater variation of temperatures across the ocular surface in the dry eye group, illustrated by the difference in temperature between the limbus and the centre of the cornea (0.64 +/- 0.20 degrees C in dry eye patients compared with 0.41 +/- 0.20 degrees C in the control group; p < 0.001). This parameter was also shown to be greater in dry eye patients who displayed either a fast tear break-up time or a poor Schirmer's test result. Infrared thermography is a non-invasive and objective technique that may prove a useful research tool for study of the tear film, its deficiencies and its various treatment modalities.

PURPOSE: Corneal temperature changes in photorefractive keratectomy (PRK) have been implicated in the aetiology of subepithelial haze. This study was undertaken to quantify the temperature change during this surgical procedure. METHODS: Non-contact, colour-coded ocular thermography was performed by using an infrared detection system during PRK on a group of 12 subjects. RESULTS: Mean (+/-SD) central ocular surface temperature (OST) after epithelial debridement was 29.15 +/- 0.39 degrees C. Mean peak OST during PRK was 37.77 +/- 0.67 degrees C, with most of the temperature increase occurring during the first 15 s. Factors such as ablation depth, optical correction, and procedure duration were not demonstrated to have a significant effect on corneal temperature during the procedure, suggesting a complex relation between-PRK parameters and the change in corneal temperature. CONCLUSIONS: Previous work suggested that corneal collagen denatures at approximately 39 degrees C, and it has been demonstrated that corneal temperature may be elevated to this level during routine PRK. Further research is indicated into the effects of preoperative cooling and pausing in treatment to reduce temperature changes.

Measuring the surface temperature of the cornea by contact thermometry has the disadvantages that anaesthesia and sterility are necessary and that temperature is measured at a point. A method of measuring corneal temperature using a bolometer that does not have these disadvantages is described, together with the results obtained. In addition the theoretical and practical considerations in its use are discussed. A value for the emissivity of the corneal surface of between 0·97 and 1 is derived.