A relatively dry eye during sleep

Pilot evaluation of the circadian rhythm of tear production in a population of healthy adult cats

OBJECTIVES

The purpose of this study was to determine if a circadian rhythm exists in Schirmer's tear test (STT-1) values in a group of healthy adult cats.

ANIMALS STUDIED

Twenty adult neutered Domestic Short-haired cats (DSH) were used in the study.

PROCEDURES

Tear production was measured with the Schirmer tear test (STT-1) at 12 different time points over a 48-hour period.

RESULTS

A significant difference (approximately 4.3 mm/min) was noted between STT-1 values measured between 4 pm (lowest) and 12 am (highest) on both day 1 (P = 0.02) and day 2 (P = 0.01), and substantial variation in STT-1 values was observed at different times during the 48-hour period.

CONCLUSIONS

Significant variation in mean STT-1 values demonstrates that there is a circadian rhythm in tear production in cats and thus shows the importance of taking the time of day into account when measuring STT-1 in cats.

Tear exchange and contact lenses: a review

Tear exchange beneath a contact lens facilitates ongoing fluid replenishment between the ocular surface and the lens. This exchange is considerably lower during the wear of soft lenses compared with rigid lenses. As a result, the accumulation of tear film debris and metabolic by-products between the cornea and a soft contact lens increases, potentially leading to complications. Lens design innovations have been proposed, but no substantial improvement in soft lens tear exchange has been reported. Researchers have determined post-lens tear exchange using several methods, notably fluorophotometry. However, due to technological limitations, little remains known about tear hydrodynamics around the lens and, to-date, true tear exchange with contact lenses has not been shown. Further knowledge regarding tear exchange could be vital in aiding better contact lens design, with the prospect of alleviating certain adverse ocular responses. This article reviews the literature to-date on the significance, implications and measurement of tear exchange with contact lenses.

Sleep position and the ocular surface in a high airflow environment

Purpose

To study the relationship between sleep position and ocular surface symptoms and signs in an high air flow environment.

Methods

Prospective observational study of new patients attending the dry eye clinic was performed. Patients with pre-existing ocular history, relevant systemic history (e.g. Sjogren’s syndrome) or who were using topical or systemic therapy for dry eye were not included. Data were collected from the patient to document their dry eye symptoms; preferred dependent sleeping side and their bedroom airflow. All patients were examined by a clinician blind to the patient’s responses where Schirmer’s test and slit lamp examination were performed looking for the presence of lagophthalmos and corneal epitheliopathy.

Results

48 patients enrolled into the study of which 23 were males and 25 were females with a normal and comparable age distribution. The study found a strong association between patients’ preferred sleeping side and the incidence of corneal epitheliopathy in the contralateral eye particularly in patients with evidence of lagophthalmos. Dry eye symptoms were found to be worse and tear production lower on the contralateral side to the preferred sleeping side particularly in patients who sleep in a high airflow environment.

Conclusion

In patients sleeping in a high airflow environment with nocturnal lagophthalmos, this study observed an association between preferred dependent sleep position and increased dry eye symptoms, lower Schirmer’s scores and increased corneal epitheliopathy in the contralateral eye.

Conjunctival goblet cells density and preservative-free tafluprost therapy for glaucoma: an in vivo confocal microscopy and impression cytology study

PURPOSE

To evaluate the density of conjunctival goblet cells (GCs) in glaucomatous patients treated with preservative-free (PF) tafluprost, using laser scanning confocal microscopy (LSCM) and impression cytology (IC).

METHODS

Thirty glaucomatous patients (30 eyes) naive for therapy and thirty healthy subjects (30 eyes) were enrolled. Conjunctiva was examined by means of Heidelberg Retina Tomography/Rostock cornea module. Afterwards, the specimens for IC were obtained. Patients were randomized to PF-tafluprost (Group 1) or preserved latanoprost (Group 2) and controls to the vehicle of latanoprost (Group 3) or physiological buffered saline solution (Group 4). Both LSCM and IC were performed at baseline, and after the 1st and 6th months of therapy, GC density (GCD) (cells/mm(2) ) was the main outcome measurement.

RESULTS

  Baseline. Mean GCD was 240.69 ± 25.43 and 232.65 ± 23.52, for LSCM, and 162.10 ± 23.44 and 164.71 ± 21.03 for IC in Group 1 and 2, respectively. GC density values were not significantly different in Group 3 and 4 (p > 0.05%). Month one. Mean GCD increased to 284.16 ± 43.88 and 230.62 ± 48.32 in Group 1 (p < 0.001) and to 297.86 ± 26.87 and 221.78 ± 43.02 in Group 2 (p < 0.05), measured with LSCM and IC, respectively. In Group 3, GCD decreased to 205.88 ± 25.04 and 139.54 ± 17.37 measured with LSCM and IC, respectively (p < 0.05). Month six. Mean GCD did not change in Group 1 (p > 0.05) whereas it decreased in Group 2 (p < 0.05), compared to month 1. In Group 3, GCD further decreased to 166.32 ± 22.31 and 120.76 ± 11.66, measured with LSCM and IC, respectively (p < 0.05); in Group 4, mean GCD did not change during the study period (p > 0.05).

CONCLUSIONS

Treatment with PF tafluprost was associated with an increase in conjunctival GCD in glaucomatous eyes naïve for therapy. Further studies are mandatory to verify this finding because its validation may have important consequences in the medical management of glaucoma.

The eye and sleep

BACKGROUND

Sleep-associated disorders of the eye are increasingly recognized. Disordered sleep has also been found in some blind patients.

METHODS

Review of the current state of knowledge of sleep-related eye disorders and blindness-related sleep disorders.

RESULTS

Incomplete eyelid closure during sleep (lagophthalmos) may be physiological but in some patients can cause significant symptoms. Nocturnal lagophthalmos may be a limiting factor in the surgical repair of some eyelid and orbital disorders. Normal eyelid closure has also been linked to the development of a number of ocular surface disorders. Sleep disorders are common, and obstructive sleep apnoea (OSA) the commonest. OSA is associated with a number of serious systemic diseases and also several eye disorders including floppy eyelid syndrome, optic neuropathy, glaucoma, anterior ischaemic optic neuropathy and papilloedema secondary to raised intracranial pressure. Treatment of OSA may help floppy eyelid syndrome, halt progression of associated glaucoma, and reduce intracranial pressure in patients with associated papilloedema. The diagnosis of OSA can only be made with formal sleep studies, but asking a small number of appropriate questions will help screen those patients who should be referred for sleep studies. Some blind patients have disordered sleep patterns due to disruption of the retinal input into the hypothalamic-pineal melatonin secreting apparatus. This can be alleviated by oral administration of melatonin.

CONCLUSIONS

Ophthalmologists should be aware of sleep-associated eye disorders and refer appropriate patients for formal sleep studies. Sleep abnormalities in blind patients should be enquired about and patients offered assessment and treatment by a sleep physician.

Klassifikation der Erkrankungen der Augenoberfl�che

The ocular surface consists of the lid margin, conjunctiva and cornea which together with the tear system represent a functional entity. The diagnosis of ocular surface disease can be very difficult due to the similarity of various disease entities. The classification should be made on the pathological and pathophysiological characteristics of ocular surface disease. The first part of the classification comprises diseases of the lid margin, the tear system as well as diseases of the conjunctiva. Both the clinical presentation as well as the underlying pathophysiological and pathological characteristics of the most important ocular surface diseases are reviewed.

Tear changes in contact lens wearers following overnight eye closure

PURPOSE

Tear protein composition alters during eye closure, by becoming rich in secretory IgA (sIgA) and certain complement proteins. This may reflect altered ocular defense mechanisms during eye closure. Since overnight wear of contact lenses (CLs) is associated with an increased risk of corneal infection and inflammation, this study aimed to quantify tear protein changes with overnight soft CL wear.

METHODS

Non-stimulated tears were collected from 9 CL wearers prior to CL wear (baseline), after daily CL wear, and after 8 h sleep. Lenses were removed following wear and were extracted in 80% urea at 95 degrees C. Secretory IgA, complement C3 and C4, were measured using ELISA and total protein using the Pierce BCA assay. Assays were performed on tear samples and CL extracts.

RESULTS

Baseline tear protein concentrations were: 0 total tear protein (9.37 +/- 2.97 mg/mL), C3 (4.4 +/- 2.1 micrograms/mL), C4 (0.1 +/- 0.1 micrograms/mL), and sIgA (0.84 +/- 0.34 mg/mL). There were no differences in any protein levels between daily CL wear and no CL wear (p > 0.05). Following sleep, protein concentrations were: total tear protein (43.64 +/- 24.30 mg/mL), C3 (72.5 +/- 49.9 micrograms/mL), C4 (6.7 +/- 5.2 micrograms/mL), and sIgA (5.53 +/- 5.15 mg/mL). Total protein extracted from CLs after daily wear was 90 +/- 27 micrograms/CL and, after overnight wear, 152 +/- 24 micrograms/CL. Negligible levels of C3, C4 and sIgA were recovered from CL extracts.

CONCLUSIONS

Uncomplicated daily use of soft CLs does not appear to alter certain tear proteins compared with baseline levels. Uptake of these proteins by the CL does not appear to deplete the tear protein levels. Overnight levels of all tear proteins were increased, compared to daily CL wear.

Important concepts for treating ocular surface and tear disorders

PURPOSE

To outline important concepts for treating ocular surface and tear disorders.

METHOD

A review was conducted of recently published findings.

RESULTS

Five concepts were delineated: ocular surface health is ensured by a close relationship between ocular surface epithelia and the preocular tear film; a stable tear film is inherently maintained by external adnexae; the intact protective mechanism is controlled by effective neuroanatomic integration; corneal epithelial stem cells are located at the corneoscleral limbus; and ocular surface epithelial cell function is supported by stromal fibroblasts and matrix.

CONCLUSIONS

These concepts stress that ocular surface epithelia and the preocular tear film function as a unit and, furthermore, that several corneal and external diseases can be categorized as ocular surface and tear disorders. These concepts also help one formulate unified diagnostic and therapeutic strategies for management of these diseases.

The effect of eye closure on protein and complement deposition on Group IV hydrogel contact lenses: relationship to tear flow dynamics

PURPOSE

This study was designed to determine the effect of overnight eye closure on the rate and composition of protein deposition on high water content ionic matrix soft contact lenses (Group IV SCLs) and to extrapolate from this data information on the probable change in the rate of reflex-type tear secretion associated with eye closure.

METHODS

Group IV SCLs were temporally sampled after equivalent periods of wear under closed eye (C) or open eye (O) conditions. Lenses were rinsed in saline and the majority of the tightly bound protein extracted at 90 degrees C in 40% urea, containing 1% SDS, 1 mM DTT, 100 mM Tris-HCl (pH 8.00). Residual protein was determined by Coomassie staining of the extracted lenses and densitometric analysis. Extracted protein was quantitated and separated by SDS-PAGE. Gels were either stained with Coomassie blue or reversibly stained with imidazole-zinc and blotted. Blots were PAS stained, or lectin and antibody probed for glycoproteins, secretory IgA (sIgA), IgG, lysozyme and complement C3. Laboratory simulated deposition studies were carried out on unworn lenses exposed to HPLC purified lysozyme.

RESULTS

The protein in the saline rinse, to a large degree mirrored the composition of tear fluid in which the lens had been residing (O or C). This would suggest that the saline wash consists of residual tear fluid and loosely adherent protein. In contrast, the urea extracts were highly homogeneous consisting primarily of lysozyme and to lesser extent lysozyme dimer. This supports the contention that the Group IV SCL functions in the eye much as cationic exchange resin selectively absorbing lysozyme. C extracts also proved relatively enriched in trace amounts of sIgA, IgG and complement C3 and its breakdown products. High levels of C3 and C3 breakdown products were specifically recovered only in the C worn lens extracts from a subject experiencing unilateral contact lens associated corneal infiltrates from the affected eye. In all subjects, markedly less protein (lysozyme) was recovered in urea extracts of lenses exposed to 7-8 h of closed eye as compared to open eye wear (0.20 +/- .08 versus 0.79 +/- .15 mg/lens (n = 6)). Temporal studies further revealed that deposition was linearly related to duration of wear during the initial phase of conditioning film formation giving rise to rate constants for lysozyme deposition of 2.2 +/- 0.29 (n = 5) and 0.20 +/- 0.06 microgram/min (n = 4) under open and closed eye conditions respectively. With further wear, deposition eventually reached a steady state. Under laboratory conditions, lysozyme was much rapidly and quantitatively removed from solution in a manner following a hyperbolic plot. This suggests that during the initial phase of deposition the rate of deposition is limited by the capacity of the tear fluid to deliver lysozyme to the lens surface under these two extremes of conditions.

CONCLUSIONS

Eye closure profoundly affects the rate of lysozyme deposition on Group IV hydrogels and the composition of minor biofilm constituents in a manner that could affect biocompatibility. Findings support the contention that eye closure results in a > 90% reduction in the rate of reflex-type tear secretion.

Tear plasmin activity with contact lens wear

Plasmin, a proteolytic enzyme, has been detected in the tears of patients experiencing anterior ocular disease, and during contact lens wear. Using a radial caseinolysis procedure, we examined tear plasmin levels in 66 patients who were wearing soft and rigid lenses for daily and extended wear. Compared to non-contact lens wearers, patients wearing soft and rigid lenses for extended wear were significantly more likely to exhibit tear plasmin activity. Eight hours of open-eye thick HEMA lens wear did not induce tear plasmin activity in a group of 10 subjects. However, significant increases in tear plasmin activity were recorded after short-term (1 hour) eye closure with and without lens wear, and following overnight (8 hours) eye closure without lens wear. Overnight eye closure also resulted in significantly increased numbers of epithelial cells and leucocytes in the tear fluid. Our results suggest that increased tear plasmin activity during extended contact lens wear may be attributable to the effects of eye closure rather than hypoxia or the presence of the contact lens per se.