Delayed tear clearance in contact lens associated papillary conjunctivitis

Impact of acute conjunctivitis on ocular surface homeostasis in dogs

OBJECTIVE

To investigate the effects of acute conjunctivitis on tear film characteristics and corneal sensitivity in dogs.

ANIMALS STUDIED

Eight female spayed Beagle dogs (1.5-2 years old, 7.5-10 kg).

PROCEDURES

On two consecutive days, one randomly selected eye in each dog received 1 or 375 mg/mL histamine solution to induce mild or severe conjunctivitis, while the contralateral eye served as control. Diagnostic tests were performed in the following order: fluorescein instillation and repeated tear collection over 20 minutes (to determine tear volume [TV] and turnover rate [TTR] by fluorophotometry), Schirmer tear test-1 (STT-1), tear ferning, corneal esthesiometry, and tear film breakup time (TFBUT).

RESULTS

Results are presented as median values for severe conjunctivitis, mild conjunctivitis, and control eyes. Eyes with severe conjunctivitis had significantly higher STT-1 (24, 19.5, 17.5 mm/min; P = .002) and significantly lower TFBUT (10.5, 13.5, 15.5 s; P = .002), but no changes were noted in corneal tactile sensation (2, 2.5, 2.5 cm) or tear ferning (grades 2, 2, 2.5). Severe conjunctivitis significantly increased TV by nearly 10-fold (631, 97, 65 µL) initially (reflex tearing), although basal TV returned rapidly (<5 minutes) in all eyes (46, 58, 48 µL). Finally, there was a nonsignificant trend for higher reflex TTR in the conjunctivitis vs control eyes (68, 58, 43%/min).

CONCLUSIONS

Experimentally induced conjunctivitis increases tear quantity and decreases tear quality in dogs, but has no impact on corneal sensitivity. Changes in tear film dynamics could affect ocular pharmacology (eg, precorneal retention time), although homeostasis of lacrimal volume and drainage is rapidly restored.

S, Akshara MR, N. K, Zaidi ZS, Iqbal SF, Misra SK. Advances in chemistry and composition of soft materials for drug releasing contact lenses

Ocular drug delivery has always been a challenging feat to achieve in the field of medical sciences. One of the existing methods of non-invasive ocular drug delivery is the use of eye drops. However, drugs administered through these formulations have low bioavailability in the ocular system. This limitation can been overcome by using contact lenses as drug delivery vehicles. According to USA FDA definitions they can be categorized into two main categories-hard and soft contact lenses. Based on the material properties, hard contact lenses are mostly produced from polymers of acrylate monomers such as MMA (methyl methacrylate). These have the least water retention capacity, thereby, having minimal ability to diffuse oxygen into the corneal layer and are not ideal for long term use. Soft material contact lenses are flexible and are mainly hydrogel based. They have higher water retention capacities as compared to rigid contact lenses, which gives them the ability to transmit oxygen to the corneal layer. These hydrogel based soft materials are mainly produced from polymers of acrylate monomers such as HEMA (hydroxyethyl methacrylate) and found to be better for drug delivery contact lenses. These polymer-based soft materials have been efficiently modified in terms of their chemistry to achieve diverse physicochemical properties to produce efficient ocular drug delivery systems. However, complications such as drug leaching during storage and distribution, sterilisation, preservation of integrity of the lens and the possibility of surface roughness due to the incorporated drug molecules still need to be optimised. This review highlights the chemistries of various polymeric molecules through which physicochemical properties can be modified to achieve optimum drug loading and sustained release of the drug for application in the ocular system.

Contact lens as controllable route for ocular drug delivery.

Dry Eye Management: Targeting the Ocular Surface Microenvironment

Dry eye can damage the ocular surface and result in mild corneal epithelial defect to blinding corneal pannus formation and squamous metaplasia. Significant progress in the treatment of dry eye has been made in the last two decades; progressing from lubricating and hydrating the ocular surface with artificial tear to stimulating tear secretion; anti-inflammation and immune regulation. With the increase in knowledge regarding the pathophysiology of dry eye, we propose in this review the concept of ocular surface microenvironment. Various components of the microenvironment contribute to the homeostasis of ocular surface. Compromise in one or more components can result in homeostasis disruption of ocular surface leading to dry eye disease. Complete evaluation of the microenvironment component changes in dry eye patients will not only lead to appropriate diagnosis, but also guide in timely and effective clinical management. Successful treatment of dry eye should be aimed to restore the homeostasis of the ocular surface microenvironment.

Immunopathogenesis of ocular allergy: a schematic approach to different clinical entities

PURPOSE OF REVIEW

The immunopathogenesis of ocular allergic disorders is generally related to the specific immunoglobulin E-mediated mast cell activation and the following cascade of inflammatory mediators. Seasonal and perennial allergic conjunctivitis, however, are the only ocular diseases to involve solely type I hypersensitivity. The other main forms, vernal and atopic keratoconjunctivitis, have a more complex immunological basis and a chronic inflammatory component. Involvement of inflammatory cells, particularly eosinophils and T cells, cytokines and proteases can lead to more serious corneal damage with vision-threatening potential.

RECENT FINDINGS

Experimental allergic conjunctival models and clinical research studies have shown that T helper type 2-related mechanisms are definitely involved in the sensitization phase of ocular allergy, however, both T helper type 1 and type 2 cytokines are overexpressed in the active disease, contributing to the development of ocular inflammation.

SUMMARY

A review of the recent literature allows us to better understand the mechanisms involved in the development of ocular allergy and to guide us toward a more schematic approach, which could possibly be useful in forming a new classification, standardizing clinical phases and individuating new treatment targets.

M cells are involved in pathogenesis of human contact lens-associated giant papillary conjunctivitis

Introduction:

The objective was to study the pathogenesis of contact lens-associated giant papillary conjunctivitis (CL-GPC).

Materials and Methods:

Twenty-one biopsies of conjunctival giant papillae were obtained from soft contact lens wearers. The tissues were fixed in 4% paraformaldehyde and embedded in paraffin. Sections of 5 µm thickness were used for studies of histology and immunohistochemistry of pan-B and pan-T cell distributions.

Results:

Conjunctival epitheliums on the top of conjunctiva-associated lymphoid tissue typically lacked goblet cells. Lymphocytes from underlying lymphoid follicle were pressed into intra-epithelial “pockets” formed through epithelial invagination. Under the follicle-associated epithelium, pan-B cells were mostly gathered in the central folliclar area and intraepithelial pockets, while CD3-positive T cells were predominantly distributed in parafolliclar region, but only a few in the intraepithelial pockets.

Conclusions:

Membranous epithelial cells (M cells) play a key role in the pathogenesis of CL-GPC for the binding and translocation of antigen and pathogen.

[Ocular allergies]

Recent developments indicate that ocular allergy is more than an IgE-mediated allergic conjunctivitis. Ocular allergy is a disease affecting the entire ocular surface including conjunctiva, lids, cornea, lacrimal gland and tear film. Besides an IgE-mediated reaction, a complex chronic inflammation is involved in the pathogenesis of many ocular allergies. According to their pathogenesis and clinical picture, ocular allergies are classified into mild forms, such as seasonal and perennial allergic conjunctivitis as well as giant papillary conjunctivitis, and chronic, potentially blinding forms such as atopic keratoconjunctivitis and vernal keratoconjunctivitis. New therapeutics act on the entire inflammatory process or try to modulate the allergic reaction early and specifically. The association with non-ocular allergic symptoms requires an interdisciplinary approach.

Use of a high molecular weight fluorescein (fluorexon) ophthalmic strip in assessments of tear film break-up time in contact lens wearers and non-contact lens wearers

PURPOSE

To assess whether fluorexon strips could be used in tear stability [tear film break-up time (TBUT)] measures, as compared with fluorescein strips.

METHODS

The pre-ocular tear film stability was assessed in 40 adults (19-29 years of age), half of whom were adapted soft contact lens wearers, using the dye-assisted tear film break-up time (TBUT) method. The measures were carried out between 10.00 and 17.00 hours, with contact lens wearers removing their lenses just before the assessments. For all subjects, fluorescein or fluorexon ophthalmic strips (pre-wetted with preservative-free saline) were used to add dye to the tear film, the TBUT was assessed three times and then the eye lightly irrigated with saline. The measures were repeated 45 min later with the other dye, with half the subjects receiving fluorescein first and the other half receiving fluorexon first.

RESULTS

Overall, the mean TBUT times were 12.2 +/- 5.9 s for fluorescein and 12.6 +/- 5.6 s for fluorexon (p = n.s.), but the non-lens wearers had longer TBUT times (14.6 and 14.5 s for the two dyes) compared with contact lens wearers (9.8 and 10.7 s, p < 0.01). While the inter-subject variability (as S.D.) was larger for non-contact lens wearers, the intra-subject variability [as coefficient of variation (COV)] was greater in the contact lens wearers when fluorescein was used (p < 0.001). When analysed as a function of the time of day that the measures were made, there were clear trends for both the fluorescein and fluorexon. TBUT values to increase in non-contact lens wearers and decrease in contact lens wearers. These trends failed to reach statistical significance, but the results with the contact lens wearers showed less variation than the non-contact lens wearers.

CONCLUSION

The use of a fluorexon dye-impregnated strip (pre-wetted with preservative-free saline) yielded comparable results with a fluorescein strip for assessments of tear film stability based on TBUT. The studies also indicate that further research is needed on changes in TBUT values during the day.

Subjective Symptom of Eye Dryness and Lifestyle Factors With Corneal Neovascularization in Contact Lens Wearers

PURPOSE

To investigate effects of subjective symptom of eye dryness and lifestyle factors on corneal neovascularization (CNV).

METHODS

Subjects were 181 Japanese adults visiting an eye clinic for contact lens (CL) fitting. All completed a self-administered questionnaire related to sex, age, lens material (rigid gas-permeable or hydrogel lens), and subjective eye dryness. Hydrogel lens wearers were restricted to users of either Etafilcon A or Nelfilcon A. The lifestyle factors included weekly working hours on visual display terminal, smoking history, and duration of CL wear. CNV was graded on a 3-point ordinal scale using a slit-lamp and analyzed in logistic regression model: normal appearance (CNV 0), congestion and dilatation or vessel penetration < 1.0 mm (CNV 1), and vessel penetration > or = 1.0 mm (CNV 2).

RESULTS

The prevalence of CNV 2 was 26% (n = 47). Multivariate analysis showed that the following three factors were significantly associated with CNV through the stepwise regression model: a use of a hydrogel lens (odds ratio [OR], 2.55; confidence interval [CI], 1.04-6.25), subjective eye dryness (OR, 2.07; CI, 1.01-4.23), and weekly CL use (OR, 3.08; CI, 1.14-8.00). Additionally, a positive trend was found between the degree of weekly CL use and the severity of CNV (P for trend test = 0.002).

CONCLUSIONS

The prevalence of CNV in the setting of this study seemed to be higher than that in previous studies, indicating that a regular eye checkup is of paramount importance for eye care. Specifically, ocular symptomology of eye dryness with the information of CL use may be carefully explored in future research.

The effect of eye closure on the post-lens tear film thickness during silicone hydrogel contact lens wear

PURPOSE

The purpose of this study was to investigate the effect of eye closure on the thickness on the post-lens tear film (POLTF) during silicone hydrogel contact lens wear.

METHODS

Ten subjects (mean age, 30.2 +/- 8.6 years; seven males) wore balafilcon A silicone hydrogel contact lenses in both eyes during the experimental procedure (power = -2.00 D, base curve = 8.6 mm). Previously described interference techniques, based on oscillations in reflectance spectra, were used to measure the post-lens tear film. Reflectance spectra (562-1030 nm) from the front of the eye wearing a contact lens were measured at normal incidence where the thickness of the POLTF was derived from the "frequency" of the oscillations. Six baseline measures of POLTF thickness were taken, followed by eye closure in the supine position for 30 minutes. Post-lens tear film thickness measures were taken after 5 and 15 minutes of eye closure. After 30 minutes of eye closure, 1 measure of POLTF was taken every minute for an additional 15 minutes.

RESULTS

The average baseline POLTF thickness was 2.00 +/- 0.30 microm (median, 2.00) for the 10 subjects. The average POLTF thickness decreased to 1.58 +/- 0.33 and 1.20 +/- 0.23 microm after 5 and 15 minutes of eye closure, respectively (repeated measures ANOVA, F = 42.18, P < 0.0001). Only 5 of 60 POLTF thickness estimates were obtained for the first 6 minutes following completion of 30 minutes of eye closure, indicating that the POLTF may be too thin (i.e., <1 microm) to measure using this method. However, there was a significant increase in POLTF thickness for 15 minutes after prolonged eye closure (mixed modeling regression, thickness = 0.85 + 0.07 x time after eye opening; P < 0.0001).

CONCLUSIONS

The POLTF thickness is rapidly reduced by eye closure during contact lens wear. After 30 minutes of eye closure, the POLTF thickness may be reduced to values less than 1 microm for the first several minutes after opening the eyes.

Spectrum of ocular allergy

PURPOSE OF REVIEW

To elaborate and review the immunologic spectrum of the five basic types of ocular allergy.

RECENT FINDINGS

Perennial allergic conjunctivitis (PAC) appears to be an extension of seasonal allergic conjunctivitis (SAC) based on the similarity of clinical symptoms and the immune mechanism involved. T helper type 2 (TH2)-type cytokines, increased ratio of TH1/TH2 cytokines and increased statement of adhesion molecules all appear to play an integral role in the inflammatory process of SAC and PAC. Vernal keratoconjunctivitis (VKC), which is a pediatric disease, differs from SAC and PAC by its more severe and chronic nature. Increased numbers of T cells, eosinophils (along with the products of degranulation), chemokines and their receptors may contribute to the more serious symptoms of VKC. Atopic keratoconjunctivitis (AKC) is similar to VKC by the increased concentration of cytokines involved (i.e. interleukin-4 and -5). Despite clinical similarities with VKC, the presence of atopic dermatitis, along with some differences in clinical signs, make AKC a separate entity, which is sometimes referred to as an adult variant of VKC. Giant papillary conjunctivitis has similar cell involvement as VKC and AKC. However, giant papillary conjunctivitis differs from VKC and AKC by the clinical signs present (i.e. the presence of giant papillae) and the necessary concurrent contact lens wear.

SUMMARY

The important differences and similarities observed in these five types of allergic diseases might help to better treat the patients affected with these disorders.