Non-contact Lens Wearers Research Articles

In vivo confocal microscopy: corneal changes of hydrogel contact lens wearers

To evaluate the corneal findings in hydrogel contact lens wearers by in vivo confocal scanning microscopy. One hundred and forty-two eyes of 71 myopic contact lens wearers (group 1) and 142 eyes of 71 non-contact lens wearers (group 2), whose age, gender and refractive error matched, were enrolled in order to detect the corneal changes by in vivo confocal microscopy through the central cornea. The average age was 25.5±5.7 (16-52) and 25.6±5.6 (17-49) in groups 1 and 2, respectively. The mean duration of contact lens wear was 43.9±15.3 (6-240) months. Anterior keratocyte density was 667.5±128.3 cells/mm(2) in group 1 and 821.4±136.7 cells/mm(2) in group 2 (P=0.001). Posterior keratocyte densities of groups 1 and 2 were 540.2±87.6 cells/mm(2) and 628.2±72.4 cells/mm(2), respectively (P<0.001). Endothelial cellular density was 2611.2±298.4 cells/mm(2) in group 1 and 2643±218.2 cells/mm(2) in group 2 (P=0.52). Ratio of polymegethism was 44.6±8.8% in group 1 and 31.3±4.7% in group 2 (P<0.001). Epithelial cellular enlargement was observed in eyes wearing contact lenses with a mean Dk/t ratio of 26.5×10(-9)±5.9 (8.9-32×10(-9)). Stromal microdots occurred with contact lenses with a mean Dk/t ratio of 13.2×10(-9)±17.5×10(-9) (8.9-20×10(-9)). In vivo examination of the cornea with confocal microscopy revealed a number of changes. These changes can be attributed both to the mechanical and the hypoxic effects of soft contact lenses. In soft contact lenses with a high Dk/t ratio, these changes would be less frequent.

Corneal erosions in contact lens wear

Contact lens wear continues to be the highest single risk factor for microbial keratitis, particularly when worn in the extended wear modality. For microbial keratitis to occur, the presence of at least a bacterial load as well as a break in the corneal surface is required. One such break occurs in the case of a corneal erosion. These well-circumscribed areas of full thickness epithelial loss can occur both with and without contact lens wear, however the risk of infection is greater in the presence of a lens due to its capacity to provide a vector for the entry of bacterial pathogens. While erosions in non-contact lens wearers are thought to result from defective epithelial basement membrane anchoring, the underlying causes during contact lens wear are yet unknown. This article sets out to review corneal erosions associated with contact lens wear, their associated risk factors such as extended wear, the mechanisms that may be responsible for their formation and the factors that differentiate them from other contact lens related adverse events. Appropriate diagnosis and understanding of the relevant pathophysiology is important to the effective treatment and an understanding of the aetiological factors responsible for erosions is critical to the development of preventative strategies and effective clinical care.

Epidemiology of lid-wiper epitheliopathy in contact lens wearers and non-contact lens wearers

Epidemiology of lid-wiper epitheliopathy in contact lens wearers and non-contact lens wearers

External Ocular Surface and Lens Microbiota in Contact Lens Wearers With Corneal Infiltrates During Extended Wear of Hydrogel Lenses

To determine whether carriage of microbes on the contact lens or ocular surfaces during extended wear (EW) with soft hydroxyethyl methacrylate (HEMA)-based contact lenses predisposes the wearer to adverse events. Participants (non-contact lens wearers) were enrolled in a clinical study involving wear of HEMA-based hydrogel lenses on a six night EW basis with weekly replacement. Type and number of bacteria colonizing the lower lid margins, upper bulbar conjunctiva, and contact lenses during EW after one night, 1 week, 1 month, and thereafter every 3 months for 3.5 years were determined. The association of bacteria with adverse responses was compared between carriers (defined as having significant microbes cultured from two or more samples with 1 year) and noncarriers, and the strength of the association was estimated using multivariate logistic regression. Carriers of gram-positive bacteria on lenses (particularly coagulase negative staphylococci or Corynebacterium spp.) were approximately three and eight times more likely to develop contact lens-induced peripheral ulcers (CLPUs) and asymptomatic infiltrates (AIs), respectively. Staphylococcus aureus was most frequently isolated from lenses during CLPU. Carriers of gram-negative bacteria on lenses were five times more likely to develop contact lens-induced acute red eye (CLARE). Haemophilus influenzae was isolated most frequently from lenses during CLARE and AI events. Bacterial carriage on contact lenses during EW predisposes the wearer to the development of corneal inflammatory events including CLARE, CLPU, and AI.

Validation of the Flush Method as an Alternative to Basal or Reflex Tear Collection

Purpose: To validate the more easily applicable “flush” tear collection technique as a viable alternative to basal and reflex tear collection.Materials and Methods: Total protein content (TPC) and immunoglobulin A (IgA) concentrations were determined in the basal, reflex, and flush tears of 16 healthy non-contact lens wearers. The overall protein profile was established using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and mass spectrometry (MS).Results: Collection-rates were 4.6 ± 6.7 μl/min, 13.9 ± 11.1 μl/min, and 25.7 ± 12.4 μl/min for the basal, reflex, and flush tears, respectively. TPC was 7.14 ± 2.22 mg/mL, 6.01 ± 2.11 mg/mL, and 3.79 ± 1.51mg/ mL for basal, reflex, and flush tears, respectively, with flush tears being significantly less concentrated than basal (p = 0.001) and reflex (p = 0.008). IgA concentration was 1.04 ± 0.29 mg/ mL, 0.64 ± 0.26 mg/mL, and 0.65 ± 0.23 mg/mL for basal, reflex, and flush tears, respectively, with basal tears being significantly more concentrated (p < 0.001). As a percentage of TPC, IgA represented 19.8 ± 14.9%, 11.4 ± 3.9%, and 19.8 ± 8.7% for basal, reflex, and flush, respectively. The flush was not significantly different to basal (p = 1.00) but significantly greater than reflex (p = 0.02). SDS-PAGE showed the same tear profiles for basal and flush tears. MS identified the most abundant proteins in all tear types.Conclusions: The flush method allows much faster collection than basal secretion sampling but returns essentially the same spectrum of proteins in similar proportions. This behavior is confirmation that the flush technique has utility as a more convenient alternative to basal tear sampling in studies involving composition analysis.

The relationship between clinical signs and dry eye symptoms.

To evaluate (i) the relationship between traditional and new clinical tests (lid-wiper epitheliopathy (LWE), lid-parallel conjunctival folds (LIPCOF)) and dry eye symptoms in non-contact lens wearers, and (ii) that a combination of these tests can improve predictive ability for the development of dry eye symptoms. Tear meniscus height (TMH), non-invasive break-up time (NIBUT), ocular hyperaemia, LIPCOF, phenol red thread test (PRTT), corneal and conjunctival staining, and LWE grades were observed in a cohort of 47 healthy, non-lens wearers (male=17, female=30, median age=35 years, range=19-70). Symptoms were assessed using the Ocular Surface Disease Index (OSDI). LWE was significantly correlated to both temporal and nasal LIPCOF (0.537<r<0.607, P<0.05). LIPCOF and LWE were significantly correlated to NIBUT and PRTT (r > -0.248, P < 0.001). Significant correlations were found between NIBUT and TMH (r=0.461, P=0.001) and PRTT (r = 0.640, P < 0.001). OSDI scores were significant correlated to NIBUT, TMH, PRTT, LIPCOF, and LWE (r>∣0.31∣; P<0.05). Significant discriminators of OSDI+/- were NIBUT (area under the receiver operative characteristic curve (AUC)=0.895), TMH (0.715), PRTT (0.781), LIPCOF (temporal/nasal/Sum 0.748/0.828/0.816), and LWE (0.749). Best predictive ability was achieved by combining NIBUT with nasal LIPCOF (AUC=0.944). The individual tests NIBUT, TMH, PRTT, LIPCOF, and LWE were significantly, but moderately, related to OSDI scores. The strongest relationship appeared by combining NIBUT with nasal LIPCOF.

Epidemiology of Ulcerative Keratitis in Northern California

To determine the incidence and associated risk factors for ulcerative keratitis in northern California. In this large-population, retrospective, cohort study, all medical records with diagnosis coding for corneal ulcers during a consecutive 12-month period were reviewed. Incidence rates were calculated using a dynamic population model. Multivariate relative risk regression was conducted to evaluate potential risk factors for ulcerative keratitis. Within the target population of 1 093 210 patients, 302 developed ulcerative keratitis. The incidence of ulcerative keratitis was 27.6 per 100 000 person-years (95% confidence interval, 24.6-30.9). The incidence of corneal ulceration in contact lens wearers was 130.4 per 100 000 person-years (95% confidence interval, 111.3-151.7), with an adjusted relative risk of 9.31 (7.42-11.7; P < .001) compared with non-contact lens wearers, who had an incidence of ulcerative keratitis of 14.0 per 100 000 person-years (11.7-16.6). Seven of 2944 people known to be infected with human immunodeficiency virus developed ulcerative keratitis, with 5 being contact lens wearers. The incidence of ulcerative keratitis in human immunodeficiency virus-positive patients was 238.1 per 100 000 person-years (95% confidence interval, 95.7-490.5), with an odds ratio of 9.31 (7.42-11.7; P < .001) compared with human immunodeficiency virus-negative patients, who had an incidence of ulcerative keratitis of 27.1 per 100 000 person-years (24.1-30.3). The incidence of ulcerative keratitis in this population is higher than previously reported. This may be owing to the increasing prevalence of contact lens wear.

Effect of contact lenses on the protein composition in tear film: a ProteinChip study

The aim of this study was to analyze and compare the effects of rigid gas permeable and soft contact lenses on the protein composition in the tear film of contact lens wearers. Wearers of soft contact lenses (CL_S, n = 13) and rigid gas permeable contact lenses (CL_H, n = 13) were recruited for this study. Thirteen non-contact lens wearers were also included as the control. Tears were collected using Schirmer strips and frozen until use. The tears were eluted and analyzed on ProteinChips SELDI-TOF (surface-enhanced laser desorption and ionization in time of flight mass spectrometry; Bio-Rad, USA) with different chromatographic surfaces (cationic and anionic exchanger and reversed phase surface). The SELDI spectra were analyzed by multivariate statistical analysis and artificial neural networks in order to find a biomarker panel which differentiates best between the groups. In order to identify protein/peptide peaks from SELDI spectra which showed a significant difference between groups, fractionated tear samples were analyzed using MALDI-TOF MS (matrix-assisted laser desorption/ionization time-of-flight mass spectrometry). For validation of biomarkers, we used an antibody microarray approach. Complex patterns of tear proteins and peptides were detected in the control group and in both contact lens groups. The tear protein composition in both wearers of rigid gas permeable (CL_H) and soft contact lenses (CL_S) differed significantly from protein composition in non-contact lens wearers (p < 0.01). The identification of biomarkers revealed an increase of Protein S100 A8 in the group of wearers of soft contact lenses (CL_S) and a decrease of a main tear protein, lysozyme, in both contact lens groups. The identified biomarker cystatin was upregulated in the group of rigid gas permeable lens wearers (CL_H), whereas the protein intensity of secretoglobin was significantly reduced in this group. Using the microarray approach, detected alterations could be confirmed. Contact lens wear alters the protein profiles in a complex manner. This study demonstrates that significant changes can be found in wearers of soft contact lenses (CL_S) and rigid gas permeable contact lenses (CL_H). Some biomarker intensities are significantly altered only in the group of rigid gas permeable lens wearers (CL_H).

Evaluation of the microstructure of cornea by in vivo confocal microscopy in contact lens wearing and non-contact lens wearing keratoconus patients

To compare the microstructure of the central keratoconic cornea in contact lens wearing and non-contact lens wearing keratoconus subjects. One hundred and one eyes of 56 keratoconic subjects were compared with control patients who wear contact lenses (22 subjects) and controls who do not wear contact lenses (40 subjects). The keratoconic subjects were assessed in 2 groups: the contact lens wearing keratoconus group (37 patients, 64 eyes, 20 female and 17 male; Group 1) and the keratoconus group comprising subjects who do not wear contact lenses (19 patients, 37 eyes, 9 female, 10 male; Group 2). The mean age was 33 +/- 12 years in the contact lens wearer keratoconus group, 31 +/- 12 years in the non-contact lens wearer keratoconus group, 34 +/- 12 years in the non-contact lens wearing control group and 29 +/- 10 years in the contact lens wearing control group. Mean basal epithelial cell density was significantly lower in the contact lens wearer keratoconus group (p < 0.001) and in the non-contact lens wearer keratoconus group (p < 0.001) in comparison with controls. The anterior, intermediate and posterior keratocyte densities were significantly lower in both contact lens wearer keratoconic subjects (p < 0.001, p < 0.001, p < 0.001) and non-contact lens wearer keratoconic subjects (p < 0.001, p < 0.001, p=0.004) as compared to controls. Endothelial cell density was not altered in keratoconic patients. The decrease in basal epithelial cell density and in keratocyte density may highlight the role of apoptosis in keratoconus. Endothelial cell density does not change in keratoconus, but extensive variability in endothelial cell size and shape may be encountered.

Posterior corneal curvature change and recovery after 6 months of overnight orthokeratology treatment

To investigate the changes in, and recovery of, posterior corneal curvature after 6 months of overnight orthokeratology (ortho-k). Twenty-eight healthy young adults were recruited for a 6-month period of ortho-k treatment and data from their right eyes were analyzed. The mean +/- standard deviation spherical equivalent refraction (SER) at baseline was -2.95 +/- 0.88 D. Posterior simulated keratometry (Sim K) readings were measured with a corneal topographer based on rotating Scheimpflug imaging. The three phases in the study were the 6-month treatment period (Phase I); diurnal changes over a period of 8 h immediately after lens removal at the completion of the treatment period (Phase II); and a 2-month recovery period after cessation of treatment (Phase III). Measurements were taken after lens wear overnight, and after 1 week, and 1, 2, 3 and 6 months of lens wear in Phase I. In Phase II, measurements were taken immediately, and then 2, 4 and 8 h after lens removal. In Phase III, corneal parameters were monitored 1 week, 2 weeks, 1 month and 2 months after cessation of ortho-k treatment. In Phase I, the posterior Sim K readings were significantly steepened after the first overnight lens wear. These significant changes were not found at other visits. In Phase II, the posterior Sim K readings were the steepest immediately after lens removal and significantly flattened 2 h after lens removal. In Phase III, all the posterior Sim K readings were similar to the baseline results. Steepening of the posterior cornea was only observed immediately after lens removal. It returns to its original shape within 2 h after cessation of lens wear. These changes appear to be in line with recent reports of the diurnal variation in the posterior corneal shape in non-contact lens wearers. The reduction in myopia from ortho-k treatment is therefore mainly due to a flattening of the anterior cornea.

Pathogenesis of Acanthamoeba Keratitis

Acanthamoeba keratitis (AK) is a serious infection of the cornea. At present, diagnosis of the disease is not straightforward and treatment is very demanding. While contact lens wear is the leading risk factor for AK, Acanthamoeba parasites are increasingly recognized as an important cause of keratitis in non-contact lens wearers. The first critical step in the pathogenesis of infection is the adhesion of the microbe to the surface of the host tissues. Acanthamoebae express a major virulence protein, the mannose-binding protein (MBP), which mediates the adhesion of amoebae to the surface of the cornea. The MBP is a transmembrane protein with characteristics of a typical cell surface receptor. Subsequent to the MBP-mediated adhesion to host cells, the amoebae produce a contact-dependent metalloproteinase and several contact-independent serine proteinases. These proteinases work in concert to produce a potent cytopathic effect (CPE) involving killing of the host cells, degradation of epithelial basement membrane and underlying stromal matrix, and penetration into the deeper layers of the cornea. In the hamster animal model, oral immunization with the recombinant MBP protects against AK, and this protection is associated with an increased level of anti-MBP IgA in tears of protected animals. Normal human tear fluid contains IgA antibodies against Acanthamoeba MBP that is likely to provide protection by inhibiting the adhesion of parasites to host cells. Indeed, in in vitro CPE assays, even a low concentration of tears (10 μL of undiluted tears per milliliter of media) almost completely inhibited Acanthamoeba-induced CPE. in addition to adherence-inhibiting, IgA-mediated protection, human tears also contain IgA-independent factors that provide protection against Acanthamoeba-induced CPE by inhibiting the activity of cytotoxic proteinases. Characterization of the CPE-inhibitory factors of human tears should lead to a better understanding of the mechanism by which the tissues of the host resist the infection and also help decode circumstances that predispose to Acanthamoeba infections.

Ocular Surface Comfort During the Day Assessed by Instant Reporting in Different Types of Contact and Non–Contact Lens Wearers

To compare instant reporting of comfort throughout the day in hydrogel, silicone-hydrogel, gas-permeable, and non-contact lens wearers. More than twenty subjects were recruited per group. Comfort scores were recorded using short message service (text message) in the morning (9:00-11:00 am), afternoon (2:00-4:00 pm), and night (7:00-9:00 pm) using a 0 (causes pain) to 100 (excellent) scale. The pooled comfort scores across all groups and time periods revealed that data are skewed toward high values: 88% of the scores felt between >or=70 and 100, whereas the remaining 12% felt between >or=40 and <70. Comfort changed significantly over time (P=0.003), but no significant differences were found between groups (P=0.66) or in the interaction between time and group (P=0.79). Hydrogel and silicone-hydrogel contact lens-wearing groups showed similar reductions in afternoon (-4.5 +/- 11.8 and -4.5 +/- 8.6, respectively) and night comfort scores (-8.3 +/- 14.1 and -9.1 +/- 8.7, respectively), and these were greater than those found in gas-permeable and non-contact lens wearers both in the afternoon (-1.0 +/- 11.3 and -1.8 +/- 16.3, respectively) and night (-7.3 +/- 9.7 and -4.1 +/- 21.9, respectively). Hydrogel and silicone-hydrogel contact lens wearers' comfort scores are reduced at night compared with morning. The slight comfort reduction at night versus morning found in non-contact lens wearers might be related to ocular or general physical fatigue, which suggest the possibility that reduced end-of-day comfort reported by contact lens wearers might not be solely related to contact lens wear. The results of this study also suggest that interpretation of comfort scores should be carried out with caution.

Recurrence rates of herpes simplex virus keratitis in contact lens and non-contact lens wearers

Recurrence rates of herpes simplex virus keratitis in contact lens and non-contact lens wearers

Application of a Novel Interferometric Method to Investigate the Relation between Lipid Layer Thickness and Tear Film Thinning

The lipid layer of the tear film forms a barrier to evaporation. Evaporation is a major cause of tear thinning between blinks and tear breakup. The purpose of this study was to investigate the relation between tear film thinning and lipid layer thickness before and after instillation of an emulsion eye drop. Fifty non-contact lens wearers were studied. Spectral interferometry was used to measure the thinning rate of the precorneal tear film for up to 19 seconds after a blink. Simultaneously, lipid layer thickness was measured based on an absolute reflectance spectrum. After a 2-minute recovery, the measurement was repeated. A drop of the lipid emulsion was then instilled; 15 minutes later, two interferometry measurements were performed similarly. A histogram of thinning rates was fitted by a bimodal distribution with narrow and broad peaks corresponding to slow and rapid thinning, respectively. The correlation between repeated thinning rate measurements was modest, but repeatability was considerably more significant when analyzed in terms of the slow/rapid dichotomy. Similarly, the correlation between thinning rate and lipid thickness was modest but was more evident when analyzed in terms of the slow/rapid dichotomy. Instillation of an emulsion eye drop significantly increased the thickness of the lipid layer but did not significantly alter the thinning rate. The proposed slow/rapid dichotomy of thinning rates presumably relates to a good/poor barrier to evaporation of the lipid layer. The imperfect correlation between thinning rate and lipid thickness indicates that other factors, such as the composition and structure of the lipid layer, are important (e.g., sufficient polar lipids may be needed to form good interface between nonpolar lipids and the aqueous layer).

Tear Oxygen Under Hydrogel and Silicone Hydrogel Contact Lenses in Humans

To determine the tear oxygen tension under a variety of conventional and silicone hydrogel contact lenses in human subjects. Three hydrogel and five silicone hydrogel lenses (Dk/t = 17 to 329) were coated on the back surface with an oxygen sensitive, bovine serum albumin-Pd meso-tetra (4-carboxyphenyl) porphine complex (BSA-porphine). Each lens type was placed on the right eye of 15 non-contact lens wearers to obtain a steady-state open eye tear oxygen tension using oxygen sensitive phosphorescence decay of BSA-porphine. A closed-eye oxygen tension estimate was obtained by measuring the change in tear oxygen tension after 5 min of eye closure. In separate experiments, a goggle was placed over the lens wearing eye and a gas mixture (PO2 = 51 torr) flowed over the lens to simulate anterior lens oxygen tension during eye closure. Mean open eye oxygen tension ranged from 58 to 133 torr. Closed eye estimates ranged from 11 to 42 torr. Oxygen tension under the goggle ranged from 8 to 48 torr and was higher than the closed eye estimate for six out of the eight lenses, suggesting that the average closed eye anterior lens surface oxygen tension is <51 torr. For Dk/t >30, the measured tear oxygen tension is significantly lower than that predicted from previous studies. The phosphorescence decay methodology is capable of directly measuring the in vivo post lens PO2 of high Dk/t lenses without disturbing the contact lens or cornea. Our data indicate that increasing Dk/t up to and beyond 140 continues to yield increased flux into the central cornea.

The blue-green autofluorescence of the human ocular lens after the wear of PMMA contact lenses.

The green ocular lens autofluorescence was determined in 30 Poly Methyl Meth Acrylate (PMMA) contact lens wearing volunteers and compared to that of 21 healthy non-contact lens wearing controls to determine whether a contact lens, reducing UV-A intensity reaching the eye, might protect the ocular lens against cataract formation. Increased autofluorescence was considered an indicator of increased probability for cataract formation. A multiple regression procedure revealed a significant yearly increase of autofluorescence with age (p < 0.01) which did not differ significantly (p > 0.86) from that in the controls. The regression procedure also revealed a decrease of the autofluorescence as a function of contact lens wear, but this decrease was not significant (p = 0.3). The order of magnitude of the decrease (-25%) corresponded to that of the calculated decrease in UV-A intensity at the ocular lens (-39%). This study could not support the thesis that cataract formation can be prevented by wearing PMMA contact lenses.

An Investigation of the Efficacy of a Novel Ocular Lubricant

To investigate the efficacy of a novel ocular lubricant compared with a commercially marketed ocular lubricant in a group of noncontact lens wearers currently using over-the-counter products for the management of symptoms of moderate to severe dry eye. This was a prospective, double-masked study that randomized 110 subjects in a ratio of 1:1 to receive a novel ocular lubricant (test group) or a marketed ocular lubricant (control group). Subjects were instructed to instill the lubricant eye drops at least three times daily. After enrollment, subjects were evaluated at baseline and at 7 and 30 days. They were also required to complete a series of home-based subjective questionnaires after 15 days. Main outcomes were subjective symptoms and objective clinical assessment at 7 and 30 days. The test group had higher overall comfort ratings than the control group (P = 0.012). Seventy-one percent of the test group and 57% of the control group said the drops used "somewhat" or "definitely" improved ocular comfort; 62% of the test group had greater end-of-day comfort compared with 45% of the control group (P = 0.015). There were no between-group differences in visual acuity, tear quality or quantity, corneal staining, conjunctival staining, or bulbar and limbal conjunctival hyperemia. The novel ocular lubricant offers equivalent or superior comfort compared with a marketed lubricant eye drop. Objective clinical outcomes were not statistically significantly different between the two groups.

Enhancing the approach to selecting eyewear (EASE): A multi-centre, practice-based study into the effect of applying contact lenses prior to spectacle dispensing

To examine the impact of contact lens application in non-contact lens wearers prior to spectacle dispensing. Ninety-one eligible subjects with no previous contact lens experience were randomly assigned into either a test group (52 subjects) or control group (39 subjects). The former group was offered contact lenses before spectacle dispensing. The latter group proceeded to spectacle dispensing in the normal way without being offered contact lenses. The response to the offer of contact lenses, fit success, the impact on the spectacle dispensing process and the longer term purchase of contact lenses were measured and compared for the test and control groups. Of the test group, 46 (88%) agreed to try contact lenses. All subjects were suitable for contact lenses after a slit lamp examination and lenses were successfully fitted to 45 of the 46 subjects (98%). The test group reported a superior subjective spectacle dispensing experience and spent 267+/-143 pounds (mean+/-standard deviation) on their spectacle frames and lenses, 32% more than the control group (202+/-128 pounds). At 3 months post dispensing, 17 test patients (33% of original cohort) had purchased contact lenses compared with five control subjects (13%) (p=0.001). The opportunity to try contact lenses prior to spectacle dispensing was well received by subjects who generally reported a very positive experience. In particular, contact lenses assisted in seeing frame detail and suitability for wear. One third of subjects proceeded to purchase contact lenses. We recommend that practitioners consider offering contact lenses to all suitable patients who are proceeding to spectacle dispensing to optimise the dispensing process and to provide an opportunity to try contact lenses.

Tear ferning in contact lens wearers

Tear ferning (TF) has shown good sensitivity and specificity in the diagnosis of dry eye, but is a relatively uncommon test, especially in contact lens wearers. The aim of this study was to investigate the relationship between TF, ocular comfort and tear film stability amongst contact lens (CL) wearers and non-contact lens (NCL) wearers. Subjects (36 NCL, 24 CL; mean age 23.2 +/- 4.8 years) underwent assessment of non-invasive tear break up time (NIBUT), fluorescein tear break up time (FBUT) and completed the Ocular Comfort Index (OCI) questionnaire. Non-stimulated tears were collected from the inferior tear meniscus with a glass capillary. Samples of 1.5 microL were air dried, observed by light microscopy and the TF pattern quantified according to Rolando's grading scale. Significantly higher grades of TF pattern and discomfort (higher OCI scores) were observed in CL wearers compared to NCL wearers (Mann-Whitney U-test; p < 0.005 and p < 0.05 respectively). Differences in tear film stability were not significant between groups. Even when asymptomatic (low OCI scores) CL and NCL subjects were compared, TF remained significantly different (p < 0.005). In both CL and NCL subjects, TF displayed poor correlation with tear film stability tests and OCI scores. Higher TF grades in CL wearers, even if asymptomatic, indicate an unfavourable ratio of salt to macromolecule concentration within the tear film of such subjects. The lack of significant difference in TF between symptomatic CL and NCL wearers could suggest similar aetiology (tear film hyperosmolarity) in each cohort. The TF technique demonstrates limited sensitivity and specificity for the prediction of ocular surface comfort in both CL and NCL wearers.

The Effect of Soft Contact Lenses During the Measurement of Retinal Nerve Fiber Layer Thickness Using Optical Coherence Tomography

Purpose: To investigate if the measurement of retinal nerve fiber layer (RNFL) thickness using optical coherence tomography (OCT) is affected by soft contact lens wear. Methods: This prospective, observational, cross-sectional clinical study looked at 66 eyes in 66 patients who usually wear soft contact lenses everyday and 36 eyes in 36 patients who did not wear contact lenses during the 6 months prior to the study. No patients had pre-existing retinal or optic nerve pathology or other media opacities that might influence the RNFL thickness. All eyes were scanned using the fast RNFL program of the Stratus OCT with and without soft contact lenses on. Results: The mean RNFL thickness in eyes with and without soft contact lenses was 99.4 ± 9.7 (SD) μ m and 100.8 ± 10.3 μ m, respectively, in contact lens wearers. The mean RNFL thickness in eyes with and without soft contact lenses was 102.8 ± 10.8 μ m and 105.3 ± 9.9 μ m, respectively, in non-contact lens wearers. The mean RNFL thickness in eyes with and without soft contact lenses was significantly different in both groups of patients (p = 0.006, p = 0.001, respectively). The average RNFL thickness without soft contact lenses was statistically significantly increased in non-contact wearers compared with soft contact lens wearers (p = 0.035). Conclusions: Soft contact lenses may affect the measurement of RNFL thickness using OCT. It is recommended that clinicians be careful in measuring RNFL thickness using OCT with myopic patients using soft contact lenses.