Corneal Nerves Altered by Orthokeratology Wear
Long-term wear of orthokeratology lenses is associated with a reduction in central corneal sensitivity and nerve fiber density, reports a study published online in the journal Eye & Contact Lens.1However, the results from the study are unclear with regards to whether patients are at risk for issues with their tear films.

Researchers from the University of New South Wales, Sydney, Australia conducted a cross-sectional study with 54 patients grouped into one of three categories, either non-lens-wearing, soft lens-wearing, or orthokeratology lens wearing. Each patient attended the clinic for a single visit during which corneal sensitivity measurements and in vivo corneal confocal microscopy were conducted on each individual’s right eye, with corneal sensitivity measured at the corneal apex and 2.5mm temporal to the apex using a Cochet-Bonnet esthesiometer. Corneal nerve morphology, in contrast, was assessed via sampling of a 1mm2 area of the corneal sub-basal nerve plexus using the Heidelberg Retinal Tomography with Rostock Corneal Module at the corneal apex and 2.5mm temporal to the apex, and nerve fiber density was calculated via measurement of nerve fiber length per square millimeter. 

Ultimately, results indicated a significant difference in corneal sensitivity between each group, with central threshold being significantly higher in the orthokeratology group than the non-wearer group and central nerve fiber density being significantly less in the orthokeratology group than in either the non-wearer or soft lens-wearer groups. Interestingly, mid-peripheral nerve fiber density was similar between all three groups, suggesting the presence of regional variations in corneal sensitivity following orthokeratology lens wear.

“Normal corneal sensitivity is essential for the health of the ocular surface,” the researchers note. “Any reduction in sensitivity can lessen the ability of the cornea to detect foreign bodies that could damage the ocular surface. The desensitization of the cornea might also compromise the lacrimal functional unit, leading to a reduction in aqueous tear film secretion and subsequently to dry eye.” As such, further research is necessary to determine whether alterations to corneal nerve morphology might “impact the stability of the precorneal tear film and integrity of the functional lacrimal unit in an [orthokeratology] lens-wearing population.”   

1. Lum E, Golebiowski B, Swarbrick HA. Reduced corneal sensitivity and sub-basal nerve density in long-term orthokeratology lens wear. Eye Contact Lens. 2016. [Epub ahead of print.] 

Gender and Transplants
Patient gender may play a role in corneal graft rejection rates.1 A study involving 18,000 British patients found that female transplant receipients were more likely to have a successful transplant if they received a woman’s cornea while there was no gender difference in failure rates for men receiving corneal tissue from either a man or a woman. Further research is necessary, to determine whether this discovery is significant; however, it falls in line with other research indicating that gender mismatches have higher rates of immunological rejection in vascularized organ transplants.

1. Hopkinson CL, Romano V, Kaye RA, et al. The Influence of donor and recipient gender incompatibility on corneal transplantation rejection and failure. Am J Transplant. 2016 July. [Epub ahead of print.] 

Contact Lens Washout Period May Not Impact Tear Film
A washout period may not be as necessary as initially believed when evaluating tear cytokines following contact lens wear or lens care product use, reports a study from the July 2016 issue of Eye & Contact Lens.1 Certain cytokines are responsible for promoting the inflammatory response on the ocular surface and are found in cases of dry eye, ocular allergy, bacterial keratitis and both soft and rigid contact lens wear.2-4

Researchers at the State University of New York and the University of New South Wales in Sydney, Australia investigated the tear makeup of 10 subjects immediately following contact lens wear and then after one, two, three, four and seven days without contact lens wear, looking for changes in the concentration levels of IL-1ß, IL-1Ra, IL-6, IL-10, IL-12 (p70) and TNF-α. Approximately 20μL to 30μL of pooled basal tears were collected bilaterally from each subject at each visit, and two custom multiplex assays were used to quantify the concentration of tear cytokines. Repeatability and reproducibility of multiple assays using tears has previously been reported.5,6 

Slit lamp findings at baseline and seven days after contact lens removal were not significantly different, though several subjects displayed epithelial microcysts, corneal neovascularization and significant lid flakes at different points during the experiment. Average corneal staining was mild at baseline (4.9±4.3) and day seven (2.9±2.5). Overall, there was no significant change in tear cytokine concentrations, with alterations over the seven-day time period as follows: 4.6±2.8 for IL-1ß, 4.6±2.8 for IL-1Ra, 14.6±11.2 for IL-6, 7.9±11.2 for IL-10, 39.8±16.8 for IL-12 and 24.9±46.3 for TNF-α.

In Brief
Pterygium size may impact the rate at which patients recover corneal sensitivity (CS) following excision surgery, notes a study published online in the journal Cornea.1 Researchers in Spain examined 32 eyes of patients with primary nasal pterygium, recording differences in corneal sensitivity, pterygium corneal area (PCA), tear osmolarity, tear break-up time, Schirmer’s test results and ocular symptoms before and one month after lesion excision. Ultimately, the researchers concluded, the only determinant was PCA. “Measures of CS did not show a relationship, evidencing an external factor such as the surgical injury as a determinant of the CS recovery process. Therefore, it may be advisable to operate when the lesion is still relatively small because the CS recovery seems to be faster.”  

1. Julio G, Campos P, Pujol P, et al. Determining factors for fast corneal sensitivity recovery after pterygium excision. Cornea. 2016. [Epub ahead of print.]

Bausch + Lomb recently announced the offering of a same-day dispensing program for eye care practitioners designed to offer patients rebate savings of up to $150 on Bausch + Lomb Ultra and Biotrue ONEday contact lenses. Biotrue multipurpose and PeroxiClear hydrogen peroxide solutions will also be featured in several major retailer in-store promotions as part of the back-to-school sales period.

Re-esterified omega-3 fatty acids are an effective treatment for dry eye disease, according to a new study.1 One hundred and five subjects (54 in the treatment group, 51 in control group) completed the study, which assessed oral nutrition as the primary therapy—specifically with regard to the effect of oral re-esterified omega-3 fatty acids on tear osmolarity, MMP-9, ocular durface disease index, tear break-up time, Schirmer’s score, corneal staining and omega Index. The study claims statistically significant improvement of tear osmolarity in its primary and secondary endpoints of six and 12 weeks. 

1. Epitropoulos AT, Donnenfeld ED, Zubin SA, et al. Effect of Oral Re-esterified Omega-3 Nutritional Supplementation on Dry Eyes. Cornea. 2016;35(9):1185-91.

A recent study involving patients with meibomian gland dysfunction (MGD) and dry eye demonstrates that a single LipiFlow (TearScience) treatment provides sustained mean improvement in gland function and symptoms.1 The trial monitored the effects of a single Lipiflow treatment through a 12-month period, during which researchers claim 86% of subjects required no further prescription therapy for dry eye symptoms.

1. Blackie CA, Coleman CA, Holland EJ. The sustained effect (12 months) of a single-dose vectored thermal pulsation procedure for meibomian gland dysfunction and evaporative dry eye. Clin Ophthal. 2016;10:1385-96.

“This study has confirmed that the selected tear cytokine concentrations did not change significantly within one week after discontinuation of contact lens wear. This indicates that a seven-day washout period may not significantly affect the ocular surface inflammatory state observed with contact lens use, although a longer period may be required to return to the levels to pre-contact lens wear level,” the researchers noted. Also, “although the between-kit repeatability was poor, this study also showed that a well-trained operator can provide repeatable and reliable findings using custom multiplex assays.”  

1. Chao C, Golebiowski B, Stapleton F, Richdale K. Changes in tear cytokine concentrations following discontinuation of soft contact lenses—a pilot study. Eye Contact Lens. 2016 Jul;42(4):237-43
2. Enriquez-de-Salamanca A, Castellanos E, Stern ME, et al. Tear cytokine and chemokine analysis and clinical correlations in evaporative-type dry eye disease. Mol Vis. 2010;16:862-73.
3. Yamaguchi T, Calvacanti BM, Cruzat A, et al. Correlation between human tear cytokine levels and cellular corneal changes in patients with bacterial keratitis by in vivo confocal microscopy. Invest Ophthalmol Vis Sci. 2014;55:7457-66.
4. Thakur A, Willcox MD. Contact lens wear alters the production of certain inflammatory mediators in tears. Exp Eye Res. 2000;70:255-9.
5. LaFrance MW, Kehinde LE, Fullard RJ. Multiple cytokine analysis in human tears: an optimized procedure for cytometric bead-based assay. Curr Eye Res. 2008;33:525-44.
6. Benito MJ, Gonzalez-Garcia MJ, Teson M, et al. Intra- and inter-day variation of cytokines and chemokines in tears of healthy subjects. Exp Eye Res. 2014;120:43-9.