Oral antioxidant therapy for marginal dry eye.

OBJECTIVE: To assess the efficacy of an orally administered antioxidant dietary supplement for managing marginal dry eye. DESIGN: A prospective, randomised, placebo controlled trial with cross-over. SETTING: Eye Clinic, Department of Vision Sciences, Glasgow Caledonian University. SUBJECTS: Forty marginal dry eye sufferers composed of 30 females and 10 males (median age 53 y; range 38-69 y). INTERVENTIONS: Baseline assessments were made of tear volume sufficiency (thread test), tear quality (stability), ocular surface status (conjunctival impression cytology) and dry eye symptoms (questionnaire). Each subject was administered courses of active treatment, placebo and no treatment, in random order for 1 month each and results compared to baseline. RESULTS: Tear stability and ocular surface status were significantly improved following active treatment (P<0.05). No changes from baseline were detected following administration of placebo and no treatment (P>0.05). Absolute increase in tear stability correlated with absolute change in goblet cell population density. Tear volume was not improved following any treatment period and dry eye symptom responses were subject to placebo effect. CONCLUSIONS: Oral antioxidants improved both tear stability and conjunctival health, although it is not yet understood whether increased ocular surface health mediates increased tear stability or vice versa. SPONSORS: This study was supported by a PhD scholarship funded by the Department of Vision Sciences, Glasgow Caledonian University, Scotland. Antioxidant supplements and placebos were kindly donated by Vitabiotics.

What does the phenol red thread test actually measure?

PURPOSE: This study attempts to resolve whether the phenol red thread test (PRT) is a test of tear volume or tear production through comparisons with other techniques. METHODS: Twenty asymptomatic subjects (10 men and 10 women; average age 30.6 +/- 10.8 years) had PRT (Zone Quick, Menicon) results compared with tear turnover rate (by fluorophotometry; Fluorotron Master, OcuMetrics) and tear volumes (from tear meniscus height and back extrapolation from fluorometric data). RESULTS: PRT wetting was not correlated with either tear turnover or volume (by fluorophotometry or tear meniscus height) on a Pearson product moment correlation test (p > 0.05). CONCLUSIONS: No clear experimental evidence in favor of the PRT being a measure of tear production or volume was found. It is probable that the PRT measures uptake of a (small) amount of fluid residing in the eye, stimulates a low degree of reflex tearing, and reflects the absorption characteristics of the thread dependent on the biophysics or composition of tears.

Comparison of grading schemes to quantitative assessments of nucleus-to-cytoplasmic ratios for human bulbar conjunctival cells collected by impression cytology.

PURPOSE: To quantitatively assess the measured nucleus-to-cytoplasm (N/C) ratios for sets of bulbar conjunctival cells categorised by a subjective grading scheme (0-3). METHODS: Impression cytology samples were taken from the nasal bulbar conjunctiva of 37 individuals (aged 22 to 74 years) without any significant eye disease. The sheets of cells were generally stained with Giemsa, photographed and 35 mm slides prepared. The images were graded 0 to 3 according to the scheme of Nelson [Cornea 7, 71-81 (1988)] and approximately 35 contiguous cells from each image measured by planimetry from an overlay. RESULTS: Analysis of 1097 cells revealed that the N/C ratios ranged from 1.395 to 0.056 and correlated well with the grading. The average N/C ratio (range for +/- 1.96 SD) for each grade was 0.607 (0.983 to 0.531) for grade 0, 0.533 (0.759 to 0. 333) for grade 1, 0.291 (0.427 to 0.155) for grade 2, and 0.154 (0. 228 to 0.080) for grade 3. CONCLUSIONS: N/C ratios can be assessed from conjunctival impression cytology samples and appear to be sufficiently consistent to allow for a designated range of cell N/C ratios to be specified for each grade.

Tear thinning time and topical anesthesia as assessed using the HIRCAL grid and the NCCA.

BACKGROUND: The literature contains conflicting reports of the effects of topical anesthetics on tear film stability, with some consensus that unpreserved topical anesthetics are less likely to reduce tear film stability than preserved preparations. This experiment investigated the effect of unpreserved 0.4% benoxinate hydrochloride on tear thinning time (TTT), in parallel with "real time" corneal sensitivity assessment. METHODS: Tear film stability was assessed (HIRCAL grid) in parallel with real time assessment of the pharmacological activity (NCCA) of unpreserved 0.4% benoxinate hydrochloride in normal eyes. RESULTS: The anesthetic used did not significantly affect tear film stability. This finding is in agreement with previous investigators. CONCLUSIONS: Unpreserved 0.4% benoxinate hydrochloride could be used to facilitate tear film stability assessment. The experimental protocol used could also be applied to investigate the temporal relationship between anesthesia and tear film stability with preserved topical anesthetics that have been found to decrease tear film stability.

The value of a phenol red impregnated thread for differentiating between the aqueous and non-aqueous deficient dry eye.

To determine the clinical viability of a phenol red impregnated cotton thread in differentiating between normal, aqueous deficient and non-aqueous deficient dry eyes. Subjects were recruited on the basis of subjective symptoms, tear stability, rose bengal staining, Schirmer test, conjunctival hyperaemia, patency and number of meibomian glands, presence of mucin strands, appearance of lower tear meniscus. Based on the outcome of the tests, subjects were categorised as either aqueous deficient dry eyes, non-aqueous dry eyes or normals. Subjects were randomised and a thread was applied by inserting into the lower fornix of the right eye and leaving the thread in place for 120 sec. All data was collected under similar ambient conditions. After gathering all the data, the codes were broken. Mean (+/- S.D.) thread wetting values were, all dry eyes (n = 59) 18.4 mm (5.9). Aqueous deficient dry eyes (n = 35), 15.5 mm (4.6). Non-aqueous deficient dry eyes [n = 24], 22.7 mm (5.0). For the normals (n = 38), 19.4 mm (5.0). Differences between (i) normals and aqueous deficient dry eyes and (ii) aqueous deficient and non-aqueous deficient dry eyes were significant (p = 0.01). Difference between all dry eyes and normals was not significant. For the aqueous deficient and non-aqueous deficient dry eyes only, using a cut-off value of 20 mm the calculated sensitivity and specificity values were 86% and 83% respectively. This cotton thread test can effectively differentiate between aqueous deficient and non-aqueous deficient dry eye.

Effect of 0.4% benoxinate hydrochloride on corneal sensitivity, measured using the non-contact corneal aesthesiometer (NCCA).

The Non-Contact Corneal Aesthesiometer (NCCA) was used to monitor the effect of topical anesthesia on corneal sensitivity loss and recovery. In a single masked randomized study, one drop of nonpreserved 0.4% benoxinate hydrochloride was instilled in either the right, left, or both eyes of 20 subjects on separate days, and measurements were made of the central corneal sensitivity in the right eye over a 60-min period. As controls, 10 subjects were retested, without any anesthetic instillation, over the same time period. No significant differences were found between these two benoxinate treatments, nor between the contralateral treatment and controls. Results indicate that there is no contralateral effect of benoxinate anesthesia, and that full recovery does not occur until 60 min after instillation. No effect on the depth and duration of anesthesia was found for iris color.

The dynamics of tear flow within a phenol red impregnated thread.

A method for the laboratory production of a phenol red impregnated thread is described. Using the thread, tear flow was measured in the right eye of 2 groups of normal subjects: group I, n = 20, average age 26.2 years (+/- 5.6); and group II, n = 20, average age 56.4 years (+/- 13.8). Data were collected by placing a thread over the lower lid margin for a time period of 15 s. A further seven threads were inserted at 5 min intervals for periods increasing by 15 s up to 120 s. A significant difference in mean thread wetting between the two age groups was found for thread insertion times of 30, 60 and 90s. For each eye, the rate of thread wetting was exponentially related to the period of thread insertion. Thread wetting and the constant of the exponential were not found to be gender dependent. Simulating the tears in the lower fornix, using a bath of saline, it was concluded that the exponential constant was a property of thread material and not tear fluid. For practical purposes, the rate of thread wetting reached equilibrium by 120 s where mean total thread wetting was 19.5 mm (+/- 6.5). The typical flow of tears y in mm/s, along the phenol red thread can be described by: y = 0.16 + 0.47e-0.0283t where t is the period of thread insertion.