[Immediate effect of a topical beta-blocker on breakup time]

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.

The effects of long-term topical glaucoma medication on conjunctival impression cytology

Long-term use of topical drugs can induce changes in the conjunctiva and ocular surface. To determine the conjunctival changes resulting from topical glaucoma medication, patients with glaucoma were selected and classified into seven groups, according to the medication received: 24 eyes were treated with betaxolol, 20 eyes with levobunolol, 32 eyes with timolol maleate, 22 eyes with pilocarpine, 52 eyes with beta-blocker and pilocarpine, 34 eyes with beta-blocker and dipivefrin, and 32 eyes with maximum therapy. Patients who were under 18 were excluded, as were those with any history of ocular surgery and other interventions, long-term use of any topically administered medication except glaucoma drugs, and any history or slit-lamp examination evidence of ocular surface disorders. The changes in the conjunctiva of 216 eyes were evaluated by means of ocular surface impression cytology. The medication group showed statistically significant degrees of conjunctival metaplasia when compared to the control group (p < 0.01). The cytological grading was not correlated with age, sex, type of medication, duration of topical treatment or the number of drugs (p > 0.05). Duration of treatment exceeding three months was not correlated with cytological grading. Thus, as far as surgical treatment was concerned, it was concluded that intervention within the first three months after the diagnosis would be most beneficial in the management of glaucoma. The fact that the presence of the preservative benzalkonium chloride was the same in all preparations suggests that it may be the major factor in conjunctival metaplasia.

Adverse effects of topical antiglaucomatous medications on the conjunctiva

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Ophthalmic beta-blockers since timolol

In the twenty years since beta-blockers were proposed for treatment of glaucoma, use of topical timolol has increased to account for 70% of all glaucoma medications used. The objective of this article is to review the "newer" beta-blockers, and to address the generalization that "all ophthalmic beta-blockers are the same." The review concentrates on agents that have been studied as topical treatments for patients with elevated intraocular pressure. Sections on pharmacology and design of clinical trials are included to aid the ophthalmologist in evaluating the new drugs and published clinical reports. The major questions to consider in evaluating the therapeutic potential of a new beta-blocker for the treatment of glaucoma involve efficacy and safety: Is the drug as effective as timolol? Does it have a duration of action at least as long as timolol? Does it have ocular toxicity? Is it comfortable? What are its systemic effects?