The neonatal tear film

Safety and tolerability of ozonated-oils in liposome eyedrop in preterm eye examination

BACKGROUND

Eye examinations for ROP screening in preterm newborns are characterized by two main problems: infection control and poor tear secretion. Therefore, in order to reduce the risk of ocular infection and to protect the ocular surface, netilmicin eye drops are usually used after the exams. The purpose of our study was to evaluate the safety and tolerability of ozonated-oils eyedrops during the eye examination of preterm babies in the screening for ROP, sparing the use of antibiotics eyedrops.

METHODS

All newborn infants that needed to be screened for ROP were divided into two groups: in group A we used topical netilmicin eye drops and in group B ozonated-oils eyedrops. We looked for any sign of conjunctival injection and chemosis, infectious conjunctivitis, blepharoconjunctivitis, erythema, and edema of the eyelids.

RESULTS

A total of 162 adverse effects out of 3546 examinations (4,5%) were reported acutely: in group A (1778 examinations), they consisted of 47 reactive conjunctivitis, 3 cases of blepharoconjunctivitis, 30 of eyelids swelling, and 3 infectious conjunctivitis, compared to 39 cases of conjunctival injection, 3 blepharoconjunctivitis, 33 eyelids swelling and 4 infectious conjunctivitis in group B (1768 examinations). No significant differences were found in the comparison of the two groups.

CONCLUSIONS

Ozonated-oils eyedrops should be considered a valid and safe alternative for the lubrification of the ocular surface and an adjuvant strategy to further minimize the risk of microbial contamination during screening for ROP.

Adjusting ADJUST: Optimizing the ADJUST algorithm for pediatric data using geodesic nets

A major challenge for electroencephalograph (EEG) studies on pediatric populations is that large amounts of data are lost due to artifacts (e.g., movement and blinks). Independent component analysis (ICA) can separate artifactual and neural activity, allowing researchers to remove such artifactual activity and retain a greater percentage of EEG data for analyses. However, manual identification of artifactual components is time-consuming and requires subjective judgment. Automated algorithms, like ADJUST and ICLabel, have been validated on adults, but to our knowledge, no such algorithms have been optimized for pediatric data. Therefore, in an attempt to automate artifact selection for pediatric data collected with geodesic nets, we modified ADJUST's algorithm. Our "adjusted-ADJUST" algorithm was compared to the "original-ADJUST" algorithm and ICLabel in adults, children, and infants on three different performance measures: respective classification agreement with expert coders, the number of trials retained following artifact removal, and the reliability of the EEG signal after preprocessing with each algorithm. Overall, the adjusted-ADJUST algorithm performed better than the original-ADJUST algorithm and no ICA correction with adult and pediatric data. Moreover, in some measures, it performed better than ICLabel for pediatric data. These results indicate that optimizing existing algorithms improves artifact classification and retains more trials, potentially facilitating EEG studies with pediatric populations. Adjusted-ADJUST is freely available under the terms of the GNU General Public License at: https://github.com/ChildDevLab/MADE-EEG-preprocessing-pipeline/tree/master/adjusted_adjust_scripts.

The ocular surface in children: A review of current knowledge and meta-analysis of tear film stability and tear secretion in children

PURPOSE

A review of ocular surface and meta-analysis of tear stability (tear break up time, TBUT) and tear secretion (Schirmer test) values in healthy children was conducted.

METHODS

Articles published between 1996 and 2017 indexed on MEDLINE, PubMed, Embase, Scopus and Google Scholar were retrieved using defined search terms. Statistical analysis (including sensitivity analysis and meta-regression) was performed.

RESULTS

23 studies were summarised (5,291 participants; neonates (0-29 days), infants (1 month - 1 year) or children (1-18 years) and a meta-analysis conducted using 15 eligible studies (1,077 participants). The combined mean TBUT in children was 14.64 seconds (s) (95% CI, 11.64, 17.64) and 21.76 s (95% CI, 20.43, 23.09) for sodium fluorescein TBUT and non-invasive TBUT respectively (NIBUT). The combined mean NIBUT was 32.5 s (95% CI, 31.78-33.22) in neonates. The combined mean Schirmer I with and without anesthesia were 16.26 mm/5 min (95% CI, 13.17, 19.36) and 29.30 mm/5 min (95% CI, 27.65, 30.96) in children and 9.36 mm/5 min (95% CI, 6.54, 12.18) and 17.63 mm/5 min (95% CI, 12.03, 23.23) in neonates. Meta-regression showed a significantly lower TBUT in children from studies conducted in Asia (p = 0.004).

CONCLUSION

There is paucity of data on ocular surface variables in healthy children, making it difficult to draw valid comparisons with adult values.

Impact of environmental adaptation on tear film assessments

PURPOSE

The purpose of this study was to investigate the effect of ocular environmental adaptation on clinical tear film assessment.

METHOD

Thirty subjects (male, mean age 23±2.5) participated in this study. A number of clinical tear film tests were applied, including: fluorescein tear break-up time (FTBUT), Schirmer test and tear prism height test (TPH). The tear physiology of each subject was evaluated twice, once immediately when they arrived from the external environment, and then after 30minutes adaptation in the exam room environment.

RESULTS

The mean values were: Schirmer test A (22.1±2.99), Schirmer test B (24.2±2.63), FTBUT A (8.00±1.94), FTBUT B (9.13±2.04), TPH A (0.179±0.026) and TPH B* (0.187±0.023). Statistical testing using Wilcoxon-signed rank test showed a significant difference between the Schirmer test results measured at the different times (P=0.008). Also, the FTBUT and tear prism height test results showed significant differences between the two evaluation times, (P=0.001, 0.011, respectively) (A: tear assessed when the subject comes from the outside environment, B: tear film assessed after 30min adaptation in the clinical environment).

CONCLUSION

This study showed a significant difference between the tear film test results evaluated when the subjects were assessed immediately from the outside environment and after an adaptation time in the clinic environment. Practitioners must consider the effect of differences between external and clinical environment adaptation on clinical tear film physiology.

Tear film stability: a review

Tear film stability can be assessed via a number of tools designed for clinical as well as research purposes. These techniques can give us insights into the tear film, and allow assessment of conditions that can lead to dry eye symptoms, and in severe cases, to significant ocular surface damage and deterioration of vision. Understanding what drives tear film instability and its assessment is also crucial for evaluating existing and new therapies. This review examines various techniques that are used to assess tear film instability: evaluation of tear break-up time and non-invasive break-time; topographic and interferometric techniques; confocal microscopic methods; aberrometry; and visual function tests. It also describes possible contributions of different tear film components; namely meibomian lipids, ocular mucins and proteins, and factors such as age, contact lens wear, ocular surgery and environmental stimuli, that may influence tear film instability.

Meibomian gland morphology in Japanese infants, children, and adults observed using a mobile pen-shaped infrared meibography device

PURPOSE

To compare meibomian gland morphology between children and adults.

DESIGN

Cross-sectional, observational case series.

METHODS

In an institutional setting, healthy pediatric (n = 78, 30 boys, 48 girls; mean age ± standard deviation, 4.1 ± 3.4 years; range 1 month - 12 years) and adult (n = 25, 11 men, 14 women; 31.3 ± 4.8 years; range 24-39 years) volunteers participated in the study. A noninvasive mobile pen-shaped infrared meibography device was used to observe the meibomian glands. Lost meibomian gland area (meiboscore) was scored from grade 0 (no meibomian gland loss) through grade 3 (>two-thirds of the total area lost). The number of meibomian glands in each eyelid was counted by reviewing the video. Eyelid width was measured using a ruler. Meibomian gland density was calculated as the number of meibomian glands divided by the eyelid width.

RESULTS

The numbers of meibomian glands in the upper/lower eyelids were 26.9 ± 3.9 / 22.0 ± 2.2 in the pediatric group and 28.1 ± 2.7 / 24.4 ± 2.6 in the adult group (P = .22, P < .0001). Eyelid width was 24.4 ± 2.4 mm in the pediatric group and 27.9 ± 1.57 mm in the adult group (P < .0001). Meibomian gland densities in the upper/lower eyelids were 1.09 ± 0.17 / 0.91 ± 0.11 in the pediatric group and 1.01 ± 0.12 / 0.88 ± 0.10 in the adult group (P = .03, P = .45).

CONCLUSIONS

The mobile pen-shaped infrared meibography device is useful for obtaining information on the meibomian gland structure, not only in adults but also in children, including infants. The morphology of the meibomian glands in children was the same as that in adults, distributing across the whole tarsal plates in both the upper and lower eyelids.

Spontaneous eyeblink activity

Spontaneous blinking is essential for maintaining a healthy ocular surface and clarity of vision. The spontaneous blink rate (SBR) is believed to reflect a complex interaction between peripheral influences mediated by the eye surface and the central dopaminergic activity. The SBR is thus extremely variable and dependent on a variety of psychological and medical conditions. Many different methods have been employed to measure the SBR and the upper eyelid kinematics during a blink movement. Each has its own merits and drawbacks, and the choice of a specific method should be tailored to the specific needs of the investigation. Although the sequence of muscle events that leads to a blink has been fully described, knowledge about the neural control of spontaneous blinking activity is not complete. The tear film is dynamically modified between blinks, and abnormalities of the blink rate have an obvious influence on the ocular surface.

Hyperosmolarity-mediated mitochondrial dysfunction requires Transglutaminase-2 in human corneal epithelial cells

Hyperosmolar-induced ocular surface cell death is a key mitochondria-mediated event in inflammatory eye diseases. Transglutaminase (TGM)-2, a cross-linking enzyme, is purported to mediate cell death, but its link to mitochondria is unclear. In the cornea, the integrity of the epithelial cells is important for maintaining transparency of the cornea and therefore functional vision. We evaluated the role of TGM-2 and its involvement in hyperosmolarity-stimulated mitochondrial cell death in human corneal epithelial (HCE-T) cells. HCE-T cell lines stably expressing either shRNA targeting TGM-2 (shTG) or scrambled shRNA (shRNA) were constructed. Hyperosmolar conditions reduced viability and increased mitochondrial depolarization in shRNA cells. However, hyperosmolarity failed to induce mitochondrial depolarization to the same extent in shTG cells. Transient overexpression of TGM-2 resulted in very high levels of TGM-2 expression in shTG and shRNA cells. In the case of shTG cells after overexpression of TGM-2, hyperosmolarity induced the same extent of mitochondrial depolarization as similarly treated shRNA cells. Overexpression of TGM-2 also elevated transamidase activity and reduced viability. It also induced mitochondrial depolarization, increased caspase-3/7 and -9 activity, and these increases were partially suppressed by pan-caspase inhibitor Z-VAD-FMK. Corneal epithelial apoptosis via mitochondrial dysfunction after hyperosmolar stimulation is partially dependent on TGM-2. This TGM-2-dependent mechanism occurs in part via caspase-3/7 and -9. Protection against mitochondrial stress in the ocular surface targeting TGM-2 may have important implications in the survival of cells in hyperosmolar stress.

Eye blink in newborn and preschool-age children

PURPOSE

To investigate the dynamics of ocular eyelid movements in newborn infants and preschool-age children.

METHODS

Fifty newborn infants and 200 preschool children aged 4-6 years were examined. Images of each child, with his or her eyes in the primary eye position looking at an object placed at the child's height, were recorded with a digital videocamera for 3 mins. Complete and incomplete blink rates, opening, closing and complete blink times were calculated.

RESULTS

Newborn infants presented a lower number of incomplete movements than preschool children. The complete blink rate was lower in newborn infants (6.2 blinks/min) than in preschool children (8.0 blinks/minute). Eyelid closing, opening and compete blink times were longer in newborn infants than in preschool children at all observation times.

CONCLUSIONS

Newborn infants had a different pattern of eyelid movement compared with preschool children. Specific characteristics that are found in this group of children particularly, such as immaturity of the neural system and more resistant tear film, may explain these findings in part.

MUC5AC overexpression in tear film of neonates

BACKGROUND

Full-term neonates produce tears normally, but neonatal tear film is modified to resist evaporation with a thick lipid layer that allows lower spontaneous blink rates. This adaptation presumably prevents drying of the ocular surface during long inter-blink periods. However, tear-film stability is not only based on the integrity of the lipid layer, but also reflects properties of the underlying mucus layer. Characteristics of the neonatal mucus tear-film layer have not yet been described.

MATERIALS AND METHODS

Tear samples were obtained from eight full-term healthy neonates (four males, four females, mean age 1.7 +/- 0.5 days) and eight healthy adult controls (four males, four females, mean age 26.3 +/- 2.5 years). Characterization of tear samples' total proteins was obtained by spectrophotometry. Western blot for major secretory mucin MUC5AC was performed on the samples. Blink rate in the neonates and adults enrolled in the study was also observed and recorded.

RESULTS

Using the same procedure, the amount of tears collected was significantly greater in adults than in neonates (p < .01). Western Blot performed on neonatal tear samples showed a significant 76.8% increase in the expression of major secretory mucin MUC5AC as compared to healthy adult controls (p < .001). Mean blink rate recorded in neonates was significantly lower than in adults (p < .001), with a mean 1.6 +/- 0.5 blinks per minute and a mean interblink time of 33 +/- 9 seconds.

DISCUSSION

As far as we are aware this is the first description of the mucus tear-film layer in neonates. The greater tear-film stability in neonates has been so far attributed to a thicker lipid layer. In our study, we show that a concomitant increase in MUC5AC protein expression in tears is present and may contribute to this greater stability; therefore, both mucus and lipid layer should be considered while evaluating tear film stability in neonates.