Search

Purpose: Contact lens wearers aged 15-25 years are at higher risk of corneal inflammation, yet little is known about corneal inflammatory state in this group. Previous investigations show density of corneal epithelial dendritic cells (CEDC) may increase with contact lens wear. However, it is not known how corneal distribution or morphology of CEDC alters with lens wear or whether these markers are affected by age. This study characterised CEDC in adolescent and young adult contact lens wearers to determine effects of contact lens wear and age on CEDC density, distribution and morphology., Method: Forty participants (20 contact lens wearers, 20 healthy non-wearers; age 16-36 years; 16M:24F) completed this pilot study. Corneal images were captured using in vivo confocal microscopy (HRTII, Rostock). CEDC were manually counted in a 1 mm 2 area of the central and mid-peripheral cornea, and ratio of central to midperipheral density was calculated. CEDC morphology and dendrite length were graded. Differences between groups and between regions, and associations with age were examined. Significance was determined at P < 0.05., Results: A lower ratio of central to mid-peripheral CEDC density was found with younger age (ρ = 0.42, P = 0.01). CEDC morphology was not associated with age or contact lens wear. CEDC density in the mid-peripheral cornea was higher in soft lens wearers than non-wearers (P = 0.04), but central density did not differ. CEDC density and morphology were not significantly different between centre (median density 11 cells/mm 2 , range 0-120) and mid-periphery (10 cells/mm 2 , 0-58)., Conclusion: Density, distribution and morphology of CEDC do not differ in established contact lens wearers. A relatively lower density of CEDC in the central cornea of younger patients may allude to a more naive immune status in this group and warrants further study. Decreased central CEDC density identified in orthokeratology lens wear requires confirmation in a larger group., (Copyright © 2019. Published by Elsevier Ltd.)

Significance: Contemporary soft contact lenses do not affect mechanical sensitivity of the cornea, whereas conjunctival sensitivity is increased compared with nonwearers. Orthokeratology lens wear, however, reduces corneal sensitivity. The effects of contact lenses on lid margin sensitivity are unclear, and the link between ocular surface sensitivity and discomfort requires further exploration.Although up to 50% of contact lens wearers experience discomfort with varying severity, impact, and frequency, the relationship between ocular surface sensitivity and ocular surface discomfort experienced during contact lens wear is unclear. The purpose of this review is to examine and summarize the current evidence for the impact of both historical and contemporary contact lens wear on ocular surface sensitivity, the etiology of changes in ocular surface sensitivity, contact lens wear-related factors associated with changes in ocular surface sensitivity, and the relationship between sensitivity and discomfort. Despite minimal effects on mechanical corneal sensitivity with contemporary soft contact lens wear, orthokeratology reduces corneal sensitivity through pressure-related effects. This review addresses the relevance of conjunctival and potentially lid margin sensitivity in tolerance and discomfort with contemporary lens wear and the impact of instrument and stimulus characteristics. Less invasive techniques particularly for lid margin sensitivity measurements are required. Given the potential interactions between a contact lens and the varied types of ocular surface nociceptors, instruments that allow for exploration of cold and chemical sensitivity particularly may better allow the effects of lens wear to be elucidated compared with those that explore high-threshold mechanical sensitivity alone. A better understanding of the relationships between lens wear and ocular surface sensitivity may result in improved management of contact lens discomfort.

Purpose: To determine tear neuropeptide levels in contact lens wearers and non-wearers, and to examine relationships with indices of corneal innervation, tear function, and ocular discomfort., Methods: A cross-sectional, single-visit, investigator-masked pilot study. Assessments included Ocular Comfort Index (OCI), central and mid-peripheral corneal nerve density and morphology (HRT-Rostock), corneal sensitivity (Cochet-Bonnet aesthesiometer), tear Substance P and calcitonin gene-related peptide (CGRP) concentration (ELISA), in situ tear osmolarity (TearLab), tear secretion (Phenol Red Thread), and noninvasive tear break-up time (NITBUT; Keeler Tearscope). Groups were compared using independent t-test or Mann-Whitney U test, and regional differences assessed using paired t-tests. Associations were analyzed using Pearson or Spearman correlation. Significance was determined at P < .05., Results: Twenty contact lens wearers (7M:13F, 32 ± 5 years) and 20 non-wearers (7M:13F, 31 ± 5 years) completed the study. OCI score was numerically higher in lens wearers (32.27 ± 5.33) than non-wearers (27.66 ± 9.94). Tear osmolarity was higher [298.0 (IQR 291.0-309.8) vs. 288.5 (282.3-298.3) mOsmol/L; P = .01] whereas NITBUT was lower (9.8 ± 3.4 vs. 13.8 ± 5.6 s; P = .01) in lens wearers compared with non-wearers. Tear neuropeptide concentrations were not different between groups [Substance P 4.29 ng/ml (IQR 1.57-6.05), CGRP 14.89 ng/ml (5.08-59.26)], and there were no differences in nerve morphology or ocular surface sensitivity. Higher nerve density, interconnections, and tortuosity were observed in the central cornea than mid-peripherally (P < .05). OCI score was moderately associated with nerve tortuosity (r = 0.42, P = .01). CGRP was associated with central nerve density (ρ = 0.38, P = .02), as was tear secretion (r = -0.37, P = .02). Nerve interconnections were strongly associated with corneal sensitivity (ρ = 0.64, P < .001)., Conclusions: Relationships were demonstrated between nerve density, tear CGRP, and corneal sensitivity. Markers of corneal neurobiology and sensory function do not appear to be altered in contact lens wear despite worse tear function (osmolarity and stability) in lens wearers. This suggests that mechanisms other than overt changes in corneal innervation regulate tear function during lens wear. The relationship between nerve tortuosity and ocular discomfort requires elucidation.

This report characterizes the neurobiology of the ocular surface and highlights relevant mechanisms that may underpin contact lens-related discomfort. While there is limited evidence for the mechanisms involved in contact lens-related discomfort, neurobiological mechanisms in dry eye disease, the inflammatory pathway, the effect of hyperosmolarity on ocular surface nociceptors, and subsequent sensory processing of ocular pain and discomfort have been at least partly elucidated and are presented herein to provide insight in this new arena. The stimulus to the ocular surface from a contact lens is likely to be complex and multifactorial, including components of osmolarity, solution effects, desiccation, thermal effects, inflammation, friction, and mechanical stimulation. Sensory input will arise from stimulation of the lid margin, palpebral and bulbar conjunctiva, and the cornea.

Purpose: To examine the changes in corneal sensitivity after overnight wear of contact lenses with different mechanical properties., Methods: Twenty young-adult subjects wore a silicone hydrogel, rigid gas-permeable, or orthokeratology (OK) contact lens in randomized order for a single night of wear in the right eye only. All lenses were matched in Dk/t (∼46 ISO Fatt). Changes in corneal apical radius r(o), asphericity Q, and corneal refractive power (Medmont E300) were measured. Changes in central corneal sensitivity were also measured by a masked investigator using two instruments: Cochet-Bonnet (COBO) aesthesiometer and Non-Contact Corneal Aesthesiometer (NCCA)., Results: There were significant differences in corneal topographic change from baseline between the lens types for r(o), Q, and corneal refractive power. There were also significant differences in the change from baseline (mean ± SD) in corneal sensitivity between lens types using the COBO (silicone hydrogel, 0.02 ± 0.17 g/mm(2); rigid gas-permeable, 0.03 ± 0.20 g/mm; OK, 0.22 ± 0.33 g/mm(2)). A significant increase in threshold from baseline was only seen in the OK lenses (p = 0.006). There was no change in sensitivity thresholds from baseline for any lens type using the NCCA (p > 0.05)., Conclusions: Central corneal sensitivity is reduced after a single overnight wear of OK lenses, as measured using the COBO aesthesiometer. This suggests that the mechanical force exerted by contact lenses may influence corneal sensitivity.

Purpose: This study was designed to map the sub-basal nerve plexus (SBNP) in the cornea of orthokeratology (OK) lens wearers., Methods: Laser scanning confocal microscopy (LSCM) was performed in vivo on three subjects: a non-lens wearer and two OK lens wearers. Scans were performed on the right eye while the left eye fixated a moving target. A total of 575, 430, and 676 contiguous images of the SBNP were taken from the non-lens wearing and the OK lens wearing subjects, respectively, and used to construct maps of the central to mid-peripheral SBNP., Results: In the non-lens wearing eye, nerves radiated towards a whorl-like complex centered nasally and inferiorly in an overall pattern consistent with previously reported studies. In the OK lens wearing eyes, this whorl pattern was absent, replaced by a tortuous network of nerve fibers centrally, and thicker curvilinear fibers mid-peripherally, particularly in the nasal, inferior, and temporal regions., Conclusions: This study maps the corneal SBNP in OK lens wearers and provides compelling evidence that OK lens wear alters the normal SBNP distribution observed in healthy, non-lens wearing eyes.

Purpose: To estimate the just-noticeable difference (JND) in ocular comfort rating by human, contact lens-wearing subjects using 1 to 100 numerical scales., Methods: Ostensibly identical, new contact lenses were worn simultaneously in both eyes by 40 subjects who made individual comfort ratings for each eye using a 100-point numerical ratings scale (NRS). Concurrently, interocular preference was indicated on a five-point Likert scale (1 to 5: strongly prefer right, slightly prefer right, no preference, slightly prefer left, strongly prefer left, respectively). Differences in NRS comfort score (ΔC) between the right and left eyes were determined for each Likert scale preference criteria. The distribution of group ΔC scores was examined relative to alternative definitions of JND as a means of estimating its value., Results: For Likert scores indicating the presence of a slight interocular preference, absolute ΔC ranged from 1 to 30 units with a mean of 7.4 ± 1.3 (95% confidence interval) across all lenses and trials. When there was no Likert scale preference expressed between the eyes, absolute ΔC did not exceed 5 units., Conclusions: For ratings of comfort using a 100-point numerical rating scale, the inter-ocular JND is unlikely to be less than 5 units. The estimate for the average value in the population was approximately 7 to 8 units. These numbers indicate the lowest level at which changes in comfort measured with such scales are likely to be clinically significant.

Aims: To determine the repeatability of ocular surface sensitivity to mechanical stimulation using air stimuli and the effect of contact lens (CL) wear on sensitivity., Methods: Repeatability: 14 subjects (24-39 years) participated. Mechanical sensitivity to warmed (34 degrees C) and ambient (20 degrees C) air was measured for the central cornea (CC), inferior cornea (IC), and inferior conjunctiva (ICON). Measurements were taken on 12 days; six morning and six afternoon measurements. Differences between sites, time of day, and stimulus temperature were evaluated. CL wear: 10 subjects (22-30 years) participated. Measurements were taken at the same time of day, either following no wear, wear of a CL of oxygen permeability [Dk] of 28 x 10(-9) [cm/s][ml O(2)/ml mm Hg] or wear of a CL of Dk 140 x 10(-9) [cm/s][ml O(2)/ml mm Hg]. Differences between sites and wear conditions were evaluated., Results: Repeatability: Sensitivity varied between sites (p<0.01), time of day (p<0.05), and stimulus temperatures (p<0.01). There were no significant differences between days. Mean thresholds for eye temperature stimuli were; CC 64.4 (SD 28.6) ml/min; IC 84.6 (40.0) ml/min; ICON 120.6 (40.4) ml/min and for ambient temperature stimuli were CC 53.9 (16.0) ml/min, IC 59.0 (20.0) ml/min; ICON 72.6 (43.7) ml/min. CL wear: Sensitivity varied between sites and wear conditions (p<0.05). Conjunctival sensitivity was increased after wear of highly oxygen permeable CLs but unaffected by wear of low oxygen permeable CLs., Conclusions: The prototype gas aesthesiometer is able to repeatably measure ocular surface sensitivity and measurements are consistent with previously reported techniques.