Adverse effects of topical antiglaucomatous medications on the conjunctiva and the lachrymal (Brit. Engl) response

Intraocular nano-microscale drug delivery systems for glaucoma treatment: design strategies and recent progress

Glaucoma is a leading cause of irreversible visual impairment and blindness, affecting over 76.0 million people worldwide in 2020, with a predicted increase to 111.8 million by 2040. Hypotensive eye drops remain the gold standard for glaucoma treatment, while inadequate patient adherence to medication regimens and poor bioavailability of drugs to target tissues are major obstacles to effective treatment outcomes. Nano/micro-pharmaceuticals, with diverse spectra and abilities, may represent a hope of removing these obstacles. This review describes a set of intraocular nano/micro drug delivery systems involved in glaucoma treatment. Particularly, it investigates the structures, properties, and preclinical evidence supporting the use of these systems in glaucoma, followed by discussing the route of administration, the design of systems, and factors affecting in vivo performance. Finally, it concludes by highlighting the emerging notion as an attractive approach to address the unmet needs for managing glaucoma.

Conjunctiva and Tenon's Capsule Handling in the Port Delivery System with Ranibizumab Implant Insertion Procedure: Surgical Pearls

OBJECTIVES

To describe conjunctiva and Tenon's capsule handling during the Port Delivery System with ranibizumab (PDS) implant insertion procedure including up-front assessments, planning, and instrumentation, with emphasis placed on the peritomy, scleral dissection, and closure steps.

METHODS

Surgical pearls based on experience accumulated in the PDS clinical trial program in patients with retinal diseases.

RESULTS

Preoperative preparation, specific instruments, and meticulous techniques are key to optimizing surgical outcomes. Before surgery, assessment of factors that affect conjunctival integrity and an in-office conjunctiva examination are conducted. Gentle, purposeful conjunctiva and Tenon's capsule handling with nontoothed forceps and suturing with a BV needle are recommended to prevent tissue damage. The peritomy is 6 mm by 6 mm, centered around the planned implant location in the superotemporal quadrant. A complete sub-Tenon's capsule dissection is achieved using a wide, robust lateral and posterior dissection technique to free tissue from the sclera and minimize tension. The globe is stabilized during scleral cutdown by grasping the sclera with fine-toothed forceps away from the incision edge to prevent tissue delamination. When closing the peritomy, both the conjunctiva and Tenon's capsule are completely captured and sutured with scleral anchoring at the apex of the peritomy to help prevent conjunctival retraction and erosion. Mitigation and detection of adverse events is critical to successful surgical outcomes.

CONCLUSIONS

The PDS implant insertion procedure is straightforward, but it requires planned preoperative preparation, specific instruments, and meticulous techniques. The surgical pearls described here offer insights for optimizing outcomes. [Ophthalmic Surg Lasers Imaging Retina. 2022;53:266-273.].

Glaucoma: Management and Future Perspectives for Nanotechnology-Based Treatment Modalities

Glaucoma, being asymptomatic for relatively late stage, is recognized as a worldwide cause of irreversible vision loss. The eye is an impervious organ that exhibits natural anatomical and physiological barriers which renders the design of an efficient ocular delivery system a formidable task and challenge scientists to find alternative formulation approaches. In the field of glaucoma treatment, smart delivery systems for targeting have aroused interest in the topical ocular delivery field owing to its potentiality to oppress many treatment challenges associated with many of glaucoma types. The current momentum of nano-pharmaceuticals, in the development of advanced drug delivery systems, hold promises for much improved therapies for glaucoma to reduce its impact on vision loss. In this review, a brief about glaucoma; its etiology, predisposing factors and different treatment modalities has been reviewed. The diverse ocular drug delivery systems currently available or under investigations have been presented. Additionally, future foreseeing of new drug delivery systems that may represent potential means for more efficient glaucoma management are overviewed. Finally, a gab-analysis for the required investigation to pave the road for commercialization of ocular novel-delivery systems based on the nano-technology are discussed.

Tear neuromediators in eyes on chronic topical antiglaucoma therapy with and without BAK preservatives

PURPOSE

To evaluate tear neuropeptides (NPs) (vasoactive intestinal peptide (VIP), neuropeptide Y (NPY), calcitonin gene-related peptide (CGRP), substance P (SP), nerve growth factor (NGF)) in chronic ocular topical hypotensive therapy with and without benzalkonium chloride (BAK) preservative.

METHODS

A comparative, open label, cross-sectional study of patients using antiglaucoma medications for >6 months with BAK (group I), without BAK (group II) and controls was done. Tear NPs (ELISA), ocular surface evaluation tests (tear breakup time (TBUT), Schirmer's test, corneal and conjunctival staining score) and confocal central corneal subbasal nerve fibre layer (SBNFL) imaging was done.

RESULTS

Of 153 eyes evaluated, group 1 (82 eyes (41 patients; mean age 48±14.5 years)) and group 2 (71 eyes (36 patients; mean age 43.11±15 years)) were on therapy for a mean duration of 10.05±2.0 and 9.67±2.3 months, respectively. Tear analysis showed elevated SP and NGF (p<0.01); decreased CGRP (p=0.03), VIP and NPY (p<0.01) compared with controls (n=30, mean age 29.33±5.7 years). Tear NP levels (SP (p=0.1), NGF (p=0.33), CGRP (p=1), VIP (p=0.87), NPY (p=0.83)) and SBNFL (p=0.09) were comparable in both groups. There was no correlation seen between tear NP levels and clinical tests and SBNFL.

CONCLUSION

Our study analysis points towards altered tear NP levels in eyes on chronic topical hypotensive therapy in comparison with controls with no significant difference in tear NP levels and central corneal SBNFL density between the BAK preservative and BAK-free antiglaucoma therapy.

Use of Topical Cannabinomimetic Palmitoylethanolamide in Ocular Surface Disease Associated with Antiglaucoma Medications

PURPOSE

Chronic use of topical hypotensive therapies in glaucoma patients leads to chronic inflammation of the ocular surface, which decreases the success rate of long-term glaucoma management. The aim of this study is to evaluate the effect of topical palmitoylethanolamide (PEA) (Defluxa^©), a well-known anti-inflammatory and analgesic agent, in suppressing the ocular surface inflammation associated with the use of hypotensive eye drops.

METHODS

In a pilot clinical trial, we enrolled 15 glaucomatous patients who received topical PEA (Defluxa) in addition to the current antiglaucoma drugs, while 15 glaucomatous patients did not receive any additional treatment. At 3 different time points (day 0, 15, and 30), signs of ocular surface involvement, adverse events, visual acuity, and intraocular pressure were assessed.

RESULTS

Topical PEA (Defluxa) was effective in increasing the Schirmer test (P < 0.05) and the tear film breakup time (T-BUT) (P < 0.0001), and improving the conjunctival hyperemia (P < 0.0001) by day 30, compared to baseline. Compared to control, by day 15, the conjunctival hyperemia score was significantly decreased in the PEA (Defluxa) group (P < 0.01), while the T-BUT and the Schirmer Test achieved a significant improvement by day 30 (P < 0.05; P < 0.01).

DISCUSSION

Our data suggests that topical PEA (Defluxa) is a safe, effective, and generally well-tolerated treatment to prevent or suppress ocular surface inflammation attributable to chronic glaucoma treatment.

The tear ferning test: a simple clinical technique to evaluate the ocular tear film

A healthy tear film is very important for many major functions of the ocular surface. Dry eye disease is a significant clinical problem that needs to be solved but the poor correlation between clinical signs and reported symptoms makes it difficult for the clinician to apply a scientific basis to his clinical management. The problem is compounded by the difficulties of evaluating the tear film due to its transparency, small volume and complex composition. Practical insight into tear film composition would be very useful to the clinician for patient diagnosis and treatment but detailed analysis is restricted to expensive, laboratory-based systems. There is a pressing need for a simple test. The tear ferning test is a laboratory test but it has the potential to be applied in the clinic setting to investigate the tear film in a simple way. Drying a small sample of tear fluid onto a clean, glass microscope slide produces a characteristic crystallisation pattern, described as a 'tear fern'. This test is currently not widely used because of some limitations that need to be overcome but several studies have demonstrated its potential. Such limitations need to be resolved so that tear ferning could be used in the clinic setting to assess the tear film.

Decreased keratocyte density and central corneal thickness in primary open-angle glaucoma patients undergoing treatment with topical prostaglandin analogues

Purpose:

To evaluate whether prostaglandin (PG) analogue use is associated with alterations in keratocyte density and central corneal thickness (CCT) in subjects with primary open-angle glaucoma (POAG).

Materials and Methods:

Thirty-five POAG patients treated with PG analogues for >2 years and 35 control subjects without glaucoma were included in this cross-sectional study. All subjects were underwent CCT measurements using ultrasound pachymetry. Keratocyte densities of each stromal layer were determined by in vivo confocal microscopy. Student's t-test and Chi-square test were used for statistical evaluations. Correlations between keratocyte densities and CCT were analyzed using Pearson's correlation analysis.

Results:

Keratocyte densities in each stromal layer were significantly lower in glaucoma patients receiving PG analogues as compared to those of controls (P < 0.001). The mean CCT was also lower in glaucoma patients (515.2 ± 18.8 μ) than control subjects (549.6 ± 21.1 μ, P < 0.001). A positive correlation between keratocyte densities in each stromal layer and CCT was observed in POAG patients.

Conclusions:

Long-term administration of topical PG analogues may adversely influence keratocyte densities and CCT. Further prospective studies are required clarify the relationship between PG analogues and their effects on the cornea.

Ocular surface evaluation in patients treated with a fixed combination of prostaglandin analogues with 0.5% timolol maleate topical monotherapy: a randomized clinical trial

OBJECTIVES

To compare ocular surface changes induced via glaucoma treatment in patients using fixed combinations of prostaglandin analogues (travoprost, latanoprost and bimatoprost) with 0.5% timolol maleate

METHODS

A prospective, multicenter, randomized, parallel group, single-blind clinical trial was performed in 33 patients with ocular hypertension or open angle glaucoma who had not been previously treated. The ocular surface was evaluated prior to and three months after treatment, with a daily drop instillation of one of the three medications. The main outcome measurements included the tear film break-up time, Schirmer's test, Lissamine green staining, the Ocular Surface Disease Index questionnaire, impression cytology using HE and PAS and immunocytochemistry for interleukin-6 and HLA-DR. Ensaiosclinicos.gov.br: UTN - U1111-1129-2872 RESULTS: All of the drugs induced a significant reduction in intraocular pressure. Decreases in the Schirmer's test results were observed with all of the drugs. Decreases in tear-film break-up time were noted with travoprost/timolol and latanoprost/timolol. An increase in the Lissamine green score was noted with travoprost/timolol and bimatoprost/timolol. The Ocular Surface Disease Index score increased after treatment in the travoprost/timolol group. Impression cytology revealed a significant difference in cell-to-cell contact in the same group, an increase in cellularity in all of the groups and an increase in the number of goblet cells in all of the groups. The fixed combinations induced an increase in IL-6 expression in the travoprost/timolol group, in which there was also an increase in HLA-DR expression.

CONCLUSIONS

All of the fixed combinations induced a significant reduction in intraocular pressure, and the travoprost/timolol group showed increased expression of the inflammatory markers HLA-DR and interleukin-6. All three tested medications resulted in some degree of deterioration in the ocular surface after three months of glaucoma treatment.

Apoptotic effects of topical antiglaucoma medications on conjunctival epithelium in glaucoma patients

PURPOSE

In this study, we aimed to investigate the apoptotic effects of topical antiglaucoma medications on the conjunctival epithelium.

METHODS

A total of 65 patients were included in the study. Thirty patients were included in the first group who had received antiglaucomatous therapy before trabeculectomy. In the second group, 20 patients who had received no drugs before trabeculectomy were included, while the third group underwent only cataract surgery as control. During the surgery, 2 x 4 mm conjunctival samples were harvested from the upper bulbar conjunctiva. The mean apoptosis rate was calculated by determining apoptosis at conjunctival epithelium using the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) method.

RESULTS

The mean apoptosis rate was 0.537 ± 0.369 (0.026 ± 0.962) in group 1, 0.139 ± 0.162 (0.005 ± 0.676) in group 2, and 0.078 ± 0.035 (0.035 ± 0.142) in the control group (group 3). The mean apoptosis rate was significantly higher in the first group than the other 2 groups (p = 0.0001).

CONCLUSION

Apoptotic effects of topical antiglaucoma drugs on the conjunctival epithelial cells were found. However, our results revealed that the number of medications, duration of medication, and type of glaucoma had no effect on the apoptotic effect.

Intraocular pressure-lowering combination therapies with prostaglandin analogues

Intraocular pressure (IOP) reduction is currently the only therapeutic approach demonstrated to preserve visual function in patients with glaucoma. The first line of glaucoma treatment consists of topical IOP-lowering medications, usually initiated as monotherapy. A significant proportion of patients require more than one medication to reach a target IOP at which optic nerve damage will not progress. As prostaglandin analogues (PGAs) are the most effective class for reducing IOP, one of the other commonly used classes (β-adrenoceptor antagonist [β-blocker], carbonic anhydrase inhibitor or α(2)-adrenoceptor agonist) is frequently combined with a PGA. In the last decade, the use of fixed combinations containing two medications in a single bottle has steadily increased. Fixed combinations have the potential to simplify the dosing regimen, increase patient adherence, avoid the washout effect of the second drop on the first medication instilled, decrease exposure to preservatives and, sometimes, reduce the cost of treatment. Clinical trials have evaluated PGA-based fixed combinations versus unfixed combinations (individual components administered concomitantly) or versus individual monotherapies; however, any advantage that the fixed combinations may have in terms of IOP-lowering efficacy is still debated. For these reasons, the PGA-based fixed combinations are not approved by regulatory authorities in some countries, such as the US. We review the published studies evaluating the efficacy and tolerability of the IOP-lowering unfixed and fixed combination therapies with PGAs. Regarding unfixed combinations, the review shows that α(2)-adrenergic agonists-PGA and carbonic anhydrase inhibitor-PGA combinations seem to be at least as effective at reducing IOP as the β-blocker-PGA combinations. As for the fixed combinations, the review shows that the three PGA-timolol fixed combinations are more effective than their component medications used separately as monotherapy and are better tolerated than the three respective prostaglandins. The three PGA-timolol fixed combinations are less effective at reducing IOP than the unfixed combinations but are better tolerated. The advantage of the fixed combinations in terms of patient adherence and persistence is supported by a very small number of studies and remains to be more accurately determined. Most studies, but not all, seem to show that PGA-timolol fixed combinations are more effective than other available β-blocker fixed combinations (dorzolamide-timolol fixed combinations) at reducing IOP and are similarly tolerated.

Preservative use in topical glaucoma medications

Benzalkonium chloride (BAK) is the principal preservative employed in topical ocular hypotensive medications, although alternative compounds recently have begun to be employed or examined. Individual clinical trials have shown that exposure to BAK concentrations contained in ophthalmic solutions does not produce adverse sequelae in the majority of glaucoma patients, but concerns continue with regard to its long-term use. These concerns have resulted from an extensive research effort, including preclinical studies with in vitro and in vivo models, as well as recent clinical investigations dedicated specifically to this issue. The aim of this systematic literature review of both preclinical and clinical data was to determine the relevance of these findings to clinical practice. Most preclinical studies reported negative effects of BAK exposure, but with few exceptions, BAK concentrations and exposure times greatly exceeded those likely to be experienced by patients, given the normal physiological dilution by the tear film. In addition, consistent evidence of BAK-related toxicity did not emerge from our review of dedicated clinical investigations. Thus, taken together, current evidence supports the safety of BAK for most glaucoma patients, although subpopulations with abnormal tearing may benefit from alternative preservative compounds or preservative-free formulations. Further studies to identify these populations are needed.

A double-masked study to compare the efficacy and safety of topical cromolyn for the treatment of allergic conjunctivitis

BACKGROUND/PURPOSE

To compare the efficacy and safety of topical cromolyn between with and without preservative for the treatment of allergic conjunctivitis.

METHODS

A double-masked study was performed in patients with allergic conjunctivitis. Each cromolyn sodium 2% ophthalmic solution with or without 0.01% benzalkonium chloride (BAK) was randomized to apply on either eye. The efficacy and safety were evaluated every other week by a questionnaire about ocular itching, redness and foreign body sensation, and objective scores of conjunctival redness, chemosis, cornea erosion and discharge using slit-lamp biomicroscopy. An overall response was also rated by physician's impression.

RESULTS

A total of 37 subjects were enrolled in this study but only 33 completed the study. All of subjective questionnaire scores showed a significant improvement after treatment in both groups. Objective score of redness significantly decreased after treatment in either groups but not chemisos or discharge. After 4-week treatment, corneal erosion diminished significantly in the group without preservative but not in the group with 0.01% BAK. There was no significant difference between with and without 0.01% BAK groups in each subjective or objective score. No adverse effect related with medication was observed.

CONCLUSION

Cromolyn 2 % ophthalmic solution was effective and safe to treat allergic conjunctivitis. A short-term use of cromolyn 2 % ophthalmic solution with 0.01% BAK would not cause any significant toxicity in patients with allergic conjunctivitis. Preservative-free cromolyn may be beneficial to the compromised eyes or eyes required of long-term medication.

Effects of benzalkonium chloride on the ocular surface of the rabbit

PURPOSE

To evaluate the effects of benzalkonium chloride (BAK) on the ocular surface in rabbits.

METHODS

Eighteen white rabbits were divided into three groups. Topical administration of eye drops was performed four times a day for 14 days; 0.01% BAK for group I, 0.1% BAK for group II, and phosphate-buffered saline (PBS) for the control group. Schirmer test and Rose Bengal staining were carried out and conjunctival impression cytology was performed in both the upper and lower bulbar conjunctiva on days 0, 7, and 14. After day 14, both the upper and lower conjunctiva were evaluated by light and electron microscopy. Immunofluorescence staining was also performed for the detection of mucin 5AC.

RESULTS

A decrease in the goblet cell density (GCD) and histopathological changes were more prominent in the BAK-treated groups compared to the control group (P < 0.05). Moreover, these changes were more noticeable in group II than in group I (P < 0.05). The decrease in the GCD and histopathological changes were statistically more significant in the lower conjunctiva than in the upper conjunctiva in the BAK-treated groups (P < 0.05).

CONCLUSION

BAK caused damage to the ocular surface in a gravity-dependent manner. The adverse effects of BAK were more severe in the lower conjunctiva than in the upper conjunctiva.

Preservatives in eyedrops: the good, the bad and the ugly

There is a large body of evidence from experimental and clinical studies showing that the long-term use of topical drugs may induce ocular surface changes, causing ocular discomfort, tear film instability, conjunctival inflammation, subconjunctival fibrosis, epithelial apoptosis, corneal surface impairment, and the potential risk of failure for further glaucoma surgery. Subclinical inflammation has also been described in patients receiving antiglaucoma treatments for long periods of time. However, the mechanisms involved, i.e., allergic, toxic, or inflammatory, as well as the respective roles of the active compound and the preservative in inducing the toxic and/or proinflammatory effects of ophthalmic solutions, is still being debated. The most frequently used preservative, benzalkonium chloride (BAK), has consistently demonstrated its toxic effects in laboratory, experimental, and clinical studies. As a quaternary ammonium, this compound has been shown to cause tear film instability, loss of goblet cells, conjunctival squamous metaplasia and apoptosis, disruption of the corneal epithelium barrier, and damage to deeper ocular tissues. The mechanisms causing these effects have not been fully elucidated, although the involvement of immunoinflammatory reactions with the release of proinflammatory cytokines, apoptosis, oxidative stress, as well as direct interactions with the lipid components of the tear film and cell membranes have been well established. Preservative-induced adverse effects are therefore far from being restricted to only allergic reactions, and side effects are often very difficult to identify because they mostly occur in a delayed or poorly specific manner. Care should therefore be taken to avoid the long-term use of preservatives, otherwise a less toxic alternative to BAK should be developed, as this weakly allergenic but highly toxic compound exerts dose- and time-dependent effects. On the basis of all these experimental and clinical reports, it would be advisable to use benzalkonium-free solutions whenever possible, especially in patients with the greatest exposure to high doses or prolonged treatments, in those suffering from preexisting or concomitant ocular surface diseases, and those experiencing side effects related to the ocular surface. Indeed, mild symptoms should not be underestimated, neglected, or denied, because they may very well be the apparent manifestations of more severe, potentially threatening subclinical reactions that may later cause major concerns.

Comparison of preservative-induced toxicity on monolayer and stratified Chang conjunctival cells

Preservatives are used in ocular medications to prevent microbial contamination. The use of benzalkonium chloride (BAC), the most widely used preservative in ocular medications, has been scrutinized with a number of studies indicating its toxicity to monolayer cultures of corneal and conjunctival epithelial cells. The purpose of this study was to evaluate and compare the toxicity of BAC and other preservatives and common components of ocular formulations on monolayer and stratified air-lifted cultures of Chang conjunctival cells. Air-lifting Chang cells grown on transwell filters increased stratification as assessed by transepithelial electrical resistance and histology. Unlike monolayer cultures in which ocular medications containing BAC caused near complete loss of cell viability, stratified, air-lifted cultures were not affected by the presence of BAC in ocular medications with up to 30-min exposures. Stratification shifted the dose-response curve to the right for benzalkonium chloride, thimerosal, chlorhexidine digluconate, potassium sorbate and EDTA. These results demonstrate that stratification significantly affects cell viability of Chang conjunctival cells in response to preservatives and additives of ophthalmic preparations.

Detrimental effect of preservatives in eyedrops: implications for the treatment of glaucoma

Antiglaucoma medications are often associated with ocular adverse reactions such as dry eye, and burning or stinging sensations. These undesirable effects may lead to treatment discontinuation and reduced quality of life in patients with glaucoma. Antiglaucoma medications usually contain benzalkonium chloride (BAK) as a preservative. Animal studies, in vitro studies and in vivo experiments have demonstrated various adverse effects of BAK. Clinical studies have also shown an increased incidence of adverse events with BAK and have demonstrated that the withdrawal of preservatives reduces these effects. Collectively, these data suggest that preservative-free antiglaucoma treatments have clinically relevant benefits for patients.

Effects of topical antiglaucoma medications on the ocular surface

The side effects of topical antiglaucoma medications and their preservatives range from ocular discomfort to sight-threatening alterations of the ocular surface. Conjunctival hyperemia, decreased tear production and function, and superficial punctate keratitis are among the most common signs seen on routine clinical examination. Squamous cell metaplasia and changes in cell morphology have been demonstrated by impression cytology studies and evaluation of biopsy specimens, and inflammatory effects are documented by the presence of inflammatory markers. The adverse effects of topical antiglaucoma eyedrops interfere with the treatment of glaucoma on two levels: first, the discomfort produced by the eye drops discourages patient compliance; and, second, long-term treatment with eyedrops is associated with a higher failure of filtration surgery. The detailed mechanism of inflammatory response and/or direct toxicity of eye drops has yet to be determined, but it may vary with the different classes of eye drops, different preservatives, and durations of treatments. Upcoming multicenter trials for new antiglaucoma eye drops should specifically evaluate ocular surface effects.

Comparison of Toxicological Profiles of Benzalkonium Chloride and Polyquaternium-1: An Experimental Study

PURPOSE

The aim of this study was to compare, in vivo on a rat model, two different preservatives- benzalkonium chloride (BAC) and polyquaternium-1 (PQ-1)-using new experimental approaches.

METHODS

Thirty (30) eyes of 15 male Lewis rats were used in this study. Rats were randomly divided into five groups instilled twice a day for 11 days with eye drops containing different concentrations of preservatives, 0.1% BAC, 0.5% BAC, 0.1% PQ-1, 0.5% PQ-1, and balanced salt solution (BSS) as a control. The ocular surface toxicity of these two preservatives was investigated using new in vivo experimental approaches. Slit-lamp examination, the fluorescein test, the red phenol test, impression cytology, and in vivo corneal confocal microscopy were used to evaluate the rat ocular surface after preservative instillation. Histology sections and immunohistochemistry were also examined to confirm these results.

RESULTS

Compared to PQ-1, BAC consistently and dramatically altered the corneoconjunctival surface as evaluated by slit-lamp examination, the fluorescein test, impression cytology, in vivo confocal microscopy, and histology. The 0.5% BAC solution also significantly decreased tear production compared to the control. Although 0.5% PQ-1 significantly decreased goblet cell density in comparison to the control, and some abnormalities were observed with in vivo confocal microscopy, no statistically significant differences were observed between these two groups using the tear production test, slit-lamp and fluorescein evaluation, or histology.

CONCLUSION

Using an acute rat model of ocular toxicity by comparing preservatives at high concentrations, we demonstrated in vivo that high doses of PQ-1 were much less toxic than BAC. In vivo confocal microscopy and impression cytology are new promising experimental approaches to studying the rat corneoconjunctival surface, particularly in the field of ocular surface toxicity.

Achieving low target pressures with today's glaucoma medications

In the 21st century there are more highly effective medical management options for glaucoma than there were in the 1980s and 1990s. In deciding among them, the clinician's challenge is to select what is clinically relevant from the large amounts of available data. In evaluating different drugs the clinician must consider not only the mean intraocular pressure (IOP) of a trial population, but also the percentage of patients achieving clinically relevant low IOPs. The consistency of IOP control throughout the day and night is also critical. Other factors such as safety, tolerability, and cost-effectiveness must also be kept in mind, with an awareness (both in human and monetary terms) of the cost of treatment failure. This overview concludes that newer medical regimens for IOP lowering address efficacy and safety issues more successfully than older ones.

Lyophilisates for drug delivery in ophthalmology: pharmacokinetics of fluorescein in the human anterior segment

AIMS

To assess the ocular bioavailability of fluorescein from a novel water free, freeze dried ophthalmic drug delivery system compared to conventional preservative-free fluorescein eye drops.

METHODS

Sodium fluorescein 0.17% was dissolved in an aqueous solution of hydroxypropylmethyl cellulose 1.0% (HPMC), deposited on sterilised flexible hydrophobic poly(tetrafluoroethylene) (PTFE) carrier strips and freeze dried under aseptic conditions. The fluorescein dose of the lyophilisate was 68 micro g, corresponding to a single conventional drop of 40 micro l fluorescein 0.17% solution. In a randomised, open label study 12 healthy volunteers applied the lyophilised fluorescein to one eye and one drop of conventional fluorescein ophthalmic solution to the fellow eye. Fluorophotometry measurements of fluorescein concentrations in the anterior segment were performed with the Fluorotron Master II (Ocumetrics, USA) before and +15, 30, 45, 60, 120, and 180 minutes after application.

RESULTS

At all times anterior chamber fluorescein concentration was greater in the lyophysilate treated eye than the solution treated eye. The magnitude of this difference ranged from 2-5.3 times and was statistically significant.

CONCLUSION

The greater intraocular bioavailability of fluorescein from the lyophilisate relative to the solution suggests that it may be a useful method for delivering substances to the eye.

Dry eye: an update on clinical diagnosis, management and promising new treatments

Dry eye conditions are prevalent with one in four to five patients presenting to eye care practitioners having dry eye signs and/or symptoms. An intimate relationship exists between the ocular surface and the tear film. The cycle of tear film instability and ocular surface damage characteristic of dry eye conditions suggests that dry eye represents a dysfunction of an integrated ocular surface-lacrimal gland unit. Therefore, dry eye is a multifactorial condition and an approach based on clinical subtypes is required for diagnosis and management. There is increasing evidence that inflammation is a contributing and exacerbating factor in dry eye conditions and anti-inflammatory or immunomodulatory therapy for chronic dry eye conditions may facilitate ocular surface healing. Other promising new treatments for dry eye include new generation artificial tear polymers and preservative systems, secretagogues, topical androgen supplements and surgical techniques for ocular surface reconstruction.

Tear secretion following spherical and astigmatic excimer laser photorefractive keratectomy

PURPOSE

To evaluate the effect of spherical and astigmatic excimer laser photorefractive keratectomy (PRK and PARK, respectively) on tear secretion.

SETTING

The Vlemma Eye Center, Athens, Greece.

METHODS

Forty-eight eyes of 48 patients had PRK (28 eyes) or PARK (20 eyes) for the correction of myopia and combined myopic astigmatism. The fellow eye served as a control. The mean preoperative spherical equivalent was -3.96 diopters (D) +/- 1.00 (SD) in the PRK eyes (range -2.00 to -6.50 D) and -3.45 +/- 0.50 D in the PARK eyes (range -1.75 to -6.00 D). Attempted correction aimed at emmetropia. Schirmer I and II and tear film breakup time (BUT) tests were performed preoperatively and 1, 3, and 6 months postoperatively. All tests were correlated to the amount of attempted correction.

RESULTS

In the PRK group, the preoperative mean values were Schirmer I, 16.20 mm; Schirmer II, 12.73 mm; and BUT, 16.46 sec. At 1 month, they were 12.23 mm, 8.46 mm, and 13.33 sec, respectively; at 3 months, 13.86 mm, 10.64 mm, and 14.42 sec, respectively; at 6 months, 14.32 mm, 11.32 mm, and 15.36 sec, respectively. In the PARK group, the mean Schirmer I, II, and BUT values were preoperatively 18.52 mm, 14.86 mm, and 17.42 sec, respectively; at 1 month, 14.5 mm, 10.4 mm, and 14.36 sec, respectively; at 3 months, 15.36 mm, 11.81 mm, and 14.72 sec, respectively; and at 6 months, 16.5 mm, 12.15 mm, 16.5 sec, respectively. No correlation to the amount of attempted correction was found. Fellow-eye tests were not affected at any interval.

CONCLUSIONS

In the first 6 months after PRK and PARK, tear secretion test values decreased.

Antiglaucoma medications: a review of safety and tolerability issues related to their use

BACKGROUND

Much experience has been gained with the use of older classes of antiglaucoma agents--topical beta-adrenergic-receptor antagonists, nonselective adrenergic-receptor agonists, oral carbonic anhydrase inhibitors, and cholinergic agents. In the past decade, new drugs and classes of drugs used to treat glaucoma have become available, including topical carbonic anhydrase inhibitors, prostaglandin analogues, and alpha2-adrenergic-receptor agonists. Extensive community-based use of antiglaucoma medications has led to an increased understanding of the acute and long-term safety and tolerability issues associated with their use.

OBJECTIVE

This paper reviews the side effects associated with the various classes of topical antiglaucoma drugs, with a particular focus on long-term safety issues.