Search

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.

Background The aims of this study were to evaluate the intra- and inter-observer repeatability of intraocular pressure (IOP) estimates obtained using an iCare rebound tonometer and to investigate the variation in IOP measurements due to positional differences in probe placement on the cornea. Methods The IOP estimates were obtained by two observers, twice on one eye, of 114 subjects using an iCare tonometer on the central cornea. Additionally, IOP and corneal thickness were measured in 38 subjects at three locations, namely, central, at 1.5 mm nasally and at 1.5 mm temporally from the central cornea. Agreement among measurements was assessed using Bland and Altman plots and the difference in measurements obtained by the observers was compared using paired t-test. Values obtained from central, nasal and temporal regions were compared using one-way analysis of variance. Results The mean IOP measurements obtained by observer 1 on two attempts were 16.2 and 16.0 mmHg (p > 0.05) were significantly different from the IOP values obtained by observer 2 on two occasions (16.3 and 15.7 mmHg; p

Accurate and repeatable measurement of the central cornea thickness (CCT) is important in terms of follow-up of glaucoma patients. The aim of this study was to compare CCT measurements made with an ultrasonic pachymeter (USP) and with the Spectralis Anterior Segment Module optical coherence tomography (OCT) device. The study included 52 eyes of 26 primary open-angle glaucoma patients. CCT measurements were taken with the USP device and then with the OCT by imaging cornea slices. The mean CCT was measured as 555.71 ± 47.76 μm with USP and 569.46 ± 49.5 μm with OCT. Despite the differences between the measurements of the two methods, a very strong degree of consistency was seen between the CCT measurement with USP and OCT (ICC = 0.93, p < 0.001).

To compare central corneal thickness (CCT) measurements with a rotating Scheimpflug camera (RSC), noncontact specular microscopy (SM), optical low-coherence reflectometry (OLCR), and ultrasonic pachymetry (UP) in keratoconus (KC) patients.In this prospective study, four CCT measurements taken with an RSC, SM, OLCR, and UP were compared in 81 eyes of 44 consecutive KC patients. The KC patients were divided into four subgroups according to Amsler-Krumeich's KC classification.The RSC and UP measurements of the CCT were not statistically significant in all the groups. Comparison of the SM vs. the OLCR measurements yielded statistically significant differences in all the KC patients and in all KC stages. In all the KC patients, RSC and OLCR showed a high correlation coefficient factor (r = 0.87, p = 0.000).CCT measurements with RSC are comparable to those achieved with UP. Compared with the other devices, according to SM measurements, the central cornea is thicker in all keratoconic eyes and in all KC grades, and it is thinner according to OLCR. RSC, UP, SM, and OLCR should not be used interchangeably in keratoconic eyes.

A double-pass imaging polarimeter has been used to compute the central corneal birefringence axis and retardation in a group of 22 eyes of different ages. Sets of four retinal images corresponding to independent polarisation states in the analyser unit were recorded. From the intensities at the image central area the corneal polarimetric parameters were computed using the Stokes–Mueller formalism. Although the (slow) axis of the central cornea presented individual differences, it was mostly lying along the nasal-downward direction. Corneal retardation also presented a broad distribution. Neither the axis nor the retardation was correlated with age. There was a significant correlation between age and the intensity at the central area of the images. This technique might be a useful tool when combined with clinical instruments oriented to glaucoma detection, which include corneal compensation for polarimetric retinal imaging.

To investigate the influence of positional deviations on the rebound tonometer measurement.Ten white rabbits were used. A bottle of balanced salt solution was connected to the anterior chamber, and the IOP was altered by changing the height of the bottle. A pressure transducer was also connected to the anterior chamber. The IOP was measured by the rebound tonometer (RBT), the Tonopen XL, and the Perkins handheld applanation tonometer at optimal conditions and compared each tonometer. Then, the effect of placing the RBT probe at different distances, different lateral positions, and different angles to the cornea on the IOP was determined.The RBT had the lowest variance in all three tonometers. The IOP measured with the RBT was not significantly altered when the distance from the cornea was 4 to 8 mm, or when the probe was displaced 2 mm to the central cornea, or when the probe was placed at an angle of 20° from the central axis.The low variance of the RBT measurements and the non-significant changes in the IOP when the probe of the RBT was not on the central axis indicate that the RBT is useful for animal models of glaucoma. Further studies examining its use (repeatability and reliability) in human infants whose eyes and head are usually moving are required.

To investigate the influence of benzalkonium chloride (BAC) on corneal Langerhans cells (LCs) and on the development of dry eye.A randomized double-blind clinical trial was performed in 20 healthy volunteers. One eye of each subject was treated with a 0.01% BAC solution (and the fellow eye with a placebo solution) three times daily for 12 weeks. The distribution and density of LCs in the central and peripheral corneal epithelium were evaluated by in-vivo confocal laser-scanning microscopy (CLSM). The subjects were monitored for dry eye (subjective discomfort, slit-lamp biomicroscopy, tear film break-up time, Schirmer's test).In the BAC group, compared with placebo, a marked increase in LC density was found in the central cornea at Week 6 and in the central and peripheral cornea at Week 12. LC density then decreased again in both zones after the end of treatment, falling toward (or even below) baseline levels. Significant changes in the LC count relative to baseline were found at Week 12 in the central and peripheral cornea in the BAC group as well as in the peripheral cornea in the placebo group. LC density in the BAC group increased more rapidly in the central than in the peripheral cornea. During therapy the BAC group showed no signs of dry eye.12-week application of a 0.01% BAC solution in healthy volunteers induces a significant increase in LCs in the central cornea at Week 12 without dry-eye changes. The return of LC counts toward (or even below) baseline levels just four weeks after the end of BAC administration demonstrates the rapid normalization of the inflammatory environment.

Purpose. To investigate inter- and intra-system variations and the effect of corneal drying using a recently developed pDEM. Methods. pDEM was used to simulate “normal” and “dry eye” conditions using two “lacrimation-blink” intervals (20 s and 60 s). Corneas were examined/graded with sodium fluorescein before and after the experiment. At the end of each experiment, corneas were assessed by trypan blue exclusion technique. Two duplicated pDEM systems were set up and tested to investigate reproducibility. Results. There was no significant difference in the results produced by the two pDEM systems. In the eyes under “normal” condition, there was no significant increase in the fluorescein grading. However, in eyes under “dry eye” condition, fluorescein staining increased and the number of non-viable cells in the central cornea increased. Conclusions. This novel pDEM system provides a useful assessment tool for the study of causative factors and new treatment strategies for dry eye syndrome.

Desiccation of the ocular surface in dry environments is one of the factors contributing to discomfort in dry eye patients. An in vivo desiccation model was used to test efficacy of artificial tear products for prevention of ocular surface damage during extended desiccating exposure. One drop of an artificial tear or a lens rewetting solution was placed on the eye of an anesthetized rabbit and the eye was held open with a speculum for 2 hr. Desiccated eyes were held open for 2 hr without application of a tear solution. Eyes were stained with 1% methylene blue in BSS. Naive control eyes were stained with methylene blue without prior desiccation. The percentage of corneal area stained was scored and a 8-mm button of central cornea was extracted in acetone:saturated sodium sulfate (7:3). Absorbance of extracts was measured at 660 nm. Extract analysis showed that four of the five tear products tested offered complete protection from desiccation (not different from naive control), while one solution, which was...

We previously reported that extracellular matrix (ECM) accumulation in human capsular opacification included collagen types I, III, IV, V, and VI. To further characterize the ECM in capsular opacification we performed immunohistochemistry to localize collagen types XII and XIV (fibril-associated collagens with interrupted triple helices, or FACITs) in specimens of human capsular opacification and in cultures of bovine lens epithelial cells (LECs).Cryosections and paraffin sections of human capsular opacification specimens or uninjured lens capsules, as well as cultured bovine LECs, were processed for immunohistochemistry using antibodies against collagen types I to VI, XII, and XIV. A rat crystalline lens was punctured through the central cornea and the eye was processed for immunohistochemistry for FACITs after healing intervals.In the absence of injury human LECs were unstained for FACITs, but as early as 10 days after operation, LECs in healing capsules were immunoreactive. Collagen types I, III, IV, V, and VI were also detected. ECM deposited in confluent LEC cultures stained for FACITs. Normal rat LECs were not stained for FACITs, but ECM accumulated in injured lens stained for them.LECs up-regulate FACITs during post-opera-tive healing. FACITs, as well as other collagen types, are deposited in ECM in healing injured rat lens, in human capsular opacification and in LEC cultures. ECM components may regulate LEC behavior during postoperative healing.

We examined the morphology of the corneal surface epithelial cells in 13 eyes of 13 subjects using specular microscopy. We determined cell area, perimeter, and shape comparing the central cornea with the inferior and superior periphery. We found surface epithelial cells are significantly smaller in the central cornea. The cells measured 560 +/- 93 square microns in the central cornea, 850 +/- 135 square microns in the superior cornea and 777 +/- 176 square microns in the inferior cornea (p less than .005). Newly emerged surface cells are smaller and are thought to enlarge with time. We postulate that lid shearing forces are greater in the central cornea and contribute to epithelial cell exfoliation. We further postulate that preferential shearing of central corneal surface cells is an important factor driving the centripetal movement of corneal epithelial cells.

Three members of a Sicilian family, in three successive generations, were affected by central cornea guttata. The youngest of these three subjects had also a Fuchs' endo-epithelial dystrophy in the left eye. Moreover, one of her daughters (fourth generation), a 13-year-old girl, showed an endothelial microcystic degeneration of the cornea. The relationship between the three corneal anomalies is discussed.