Purpose

The purpose of this work was to gather preliminary data in normals and dry eye subjects, using a new, non-invasive imaging platform to measure the thickness of pre-corneal tear film.

Methods

Human subjects were screened for dry eye and classified as dry or normal. Tear film thickness over the inferior paracentral cornea was measured using laser illumination and a complementary metal–oxide–semiconductor (CMOS) camera. A previously developed mathematical model was used to calculate the thickness of the tear film by applying the principle of spatial auto-correlation function (ACF).

Results

Mean tear film thickness values (±SD) were 3.05 μm (0.20) and 2.48 μm (0.32) on the initial visit for normals (n=18) and dry eye subjects (n=22), respectively, and were significantly different (p<0.001, 2-sample t-test). Repeatability was good between visit 1 and 2 for normals (intraclass correlation coefficient [ICC]=0.935) and dry eye subjects (ICC=0.950). Tear film thickness increased above baseline for the dry eye subjects following viscous drop instillation and remained significantly elevated for up to approximately 32 min (n=20; p<0.05 until 32 min; general linear mixed model and Dunnett’s tests).

Conclusions

This technique for imaging the ocular surface appears to provide tear thickness values in agreement with other non-invasive methods. Moreover, the technique can differentiate between normal and dry eye patient types.

Purpose

The purpose of this work was to gather preliminary data in normals and dry eye subjects, using a new, non-invasive imaging platform to measure the thickness of pre-corneal tear film.

Methods

Human subjects were screened for dry eye and classified as dry or normal. Tear film thickness over the inferior paracentral cornea was measured using laser illumination and a complementary metal-oxide-semiconductor (CMOS) camera. A previously developed mathematical model was used to calculate the thickness of the tear film by applying the principle of spatial auto-correlation function (ACF).

Results

Mean tear film thickness values (±SD) were 3.05 μm (0.20) and 2.48 μm (0.32) on the initial visit for normals (n=18) and dry eye subjects (n=22), respectively, and were significantly different (p<0.001, 2-sample t-test). Repeatability was good between visit 1 and 2 for normals (intraclass correlation coefficient [ICC]=0.935) and dry eye subjects (ICC=0.950). Tear film thickness increased above baseline for the dry eye subjects following viscous drop instillation and remained significantly elevated for up to approximately 32 min (n=20; p<0.05 until 32 min; general linear mixed model and Dunnett's tests).

Conclusions

This technique for imaging the ocular surface appears to provide tear thickness values in agreement with other non-invasive methods. Moreover, the technique can differentiate between normal and dry eye patient types.

Purpose

The purpose of this study was to characterize the natural history of meibomian gland morphogenesis in the mouse.

Methods

Embryonic (E) and post natal (P) C57Bl/6 mouse pups were obtained at E18.5, P0, P1, P3, P5, P8, P15, and P60. Eyelids were fixed and processed for en bloc staining with Phalloidin/DAPI to identify gland morphogenesis, or frozen for immunohistochemistry staining with Oil red O (ORO) to identify lipid and antibodies specific against peroxisome proliferator-activated receptor gamma (PPARγ) to identify meibocyte differentiation. Samples were then evaluated using a Zeiss 510 Meta laser scanning confocal microscope or Nikon epi-fluorescent microscope. Tissues from adult mice (2 month-old) were also collected for western blotting.

Results

Meibomian gland morphogenesis was first detected at E18.5 with the formation of an epithelial placode within the fused eyelid margin. Invagination of the epithelium into the eyelid was detected at P0. From P1 to P3 there was continued extension of the epithelium into the eyelid. ORO and PPARγ staining was first detected at P3, localized to the central core of the epithelial cord thus forming the presumptive ductal lumen. Ductal branching was first detected at P5 associated with acinar differentiation identified by ORO and PPARγ staining. Adult meibomian glands were observed by P15. Western blotting of meibomian gland proteins identified a 50 kDa and a 72 kDa band that stained with antibodies specific to PPARγ.

Conclusions

We have demonstrated that meibomian gland development bears distinct similarities to hair development with the formation of an epithelial placode and expression of PPARγ co-incident with lipid synthesis and meibocyte differentiation.

Purpose

This study examined whether hyperspectral stimulated Raman scattering (hsSRS) microscopy can detect differences in meibum lipid to protein composition of normal and evaporative dry eye subjects with meibomian gland dysfunction.

Methods

Subjects were evaluated for tear breakup time (TBUT), staining, meibum expression and gland dropout. Expressed meibum was analyzed using SRS vibrational signatures in the CH stretching region (2800-3050 cm^-1). Vertex component analysis and K-means clustering were used to group the spectral signatures into four fractions containing high lipid (G1) to high protein (G4).

Results

Thirty-three subjects could be statistically analyzed using pooled meibum (13 with stable tear films (TBUTs > 10 s) and 20 with unstable tear films (TBUTs ≤ 10 s). Significant differences in meibum from subjects with unstable vs. stable TBUTs were found for the G1 fraction (medians 0.164 and 0.020, respectively; p = 0.012) and the G2 fraction (medians 0.244 and 0.272, respectively; p = 0.045). No differences were observed for the G3 and G4 fractions. Single orifice samples were not significantly different vs. pooled samples from the fellow eye, and eyelid sector samples (nasal, central and temporal) G2:G3 fractional components were not significantly different (p = 0.449). Spearman analysis suggested a significant inverse correlation between G1 fraction and TBUT (R = -0.351; p = 0.045).

Conclusions

hsSRS microscopy allows compositional analysis of expressed meibum from humans which correlated to changes in TBUT. These findings support the hypothesis that hsSRS may be useful in classifying meibum quality and evaluating the effects of therapy.

Purpose

To examine the effects of volume and method on fluorescein tear breakup time (TBUT) values and to evaluate test efficacy in an independent sample free of selection bias.

Methods

Subjects were assessed using a battery of dry eye tests (DETs). Efficacy study: Subjects were randomized to the DET, standard strip, and liquid NaFl on separate days. A masked examiner measured TBUTs from video recordings. Verification study: Subjects were investigated for efficacy using volumes of 5.0 and 2.0 μL mL of NaFl for TBUT.

Results

Efficacy study: 46 subjects completed the study. Log-transformed TBUTs were significantly different, normal subjects versus dry subjects, for all 3 methods (all P values < 0.001). Area under the curves (AUCs), cut-points, sensitivity, and specificity were 1) DET: 0.873, 4.4 seconds, 0.97, and 0.67, respectively; 2) 2.0 mL: 0.901, 3.22 seconds, 0.90, and 0.87, respectively; and 3) standard strip: 0.912, 3.42 seconds, 0.97, and 0.80, respectively. Verification study: Data splitting analysis for the 2.0 μL data (n = 174 dry subjects and 97 normal subjects) generated an AUC of 0.917 and a cut-point of 6.05 seconds for a sensitivity of 0.87 and a specificity of 0.81. The 5.0 μL sample yielded an AUC of 0.940, with a sensitivity and specificity of 0.92 and 0.83, respectively, at a cut-point of 5.5 seconds.

Conclusions

Little difference in TBUT was found using the 3 clinical methods with video recordings. Analysis using liquid NaFl suggests that the TBUT test has excellent diagnostic accuracy and that a cut-point of 5.3 to 6.0 seconds is the optimum to differentiate normals from persons with dry eye.