The palliative treatment of the dry eye

Chitosan-Coated SLN: A Potential System for Ocular Delivery of Metronidazole

Ophthalmic drops for ocular delivery exhibit inadequate residence time, which often requires multiple daily dosing that may result in patient non-adherence. In this study, the development of a once-daily-dosed chitosan-coated metronidazole (MTZ)-loaded solid lipid nanoparticles (SLNs) for ocular delivery was undertaken. Melt emulsification and ultrasonication were used to manufacture MTZ-loaded SLN, which were subsequently coated with chitosan (CS) by mechanical stirring using a 0.1% w/v solution. Gelucire^® 48/16 and Transcutol^® HP were used as the solid lipid and synthetic solvent, respectively, with Tween^® 20 included as a stabilizing agent. The critical quality attributes (CQA) of the optimized CS-coated SLN that was monitored included particle size, polydispersity index, Zeta potential, % entrapment efficiency, % MTZ loading, pH, and osmolarity. The optimized coated nanocarriers were evaluated using laser Doppler anemometry (LDA) and were determined to be stable, with particle sizes in the nanometre range. In vitro mucoadhesion, MTZ release and short-term stability, in addition to the determination of the shape of the optimized CS-coated SLN, were undertaken. The mucoadhesive properties of the optimized CS-coated MTZ-loaded SLN demonstrated increased ocular availability, which may allow dose reduction or longer intervals between doses by improving precorneal retention and ocular availability. Overall, our findings suggest that CS-coated MTZ-loaded SLNs have the potential for clinical application, to enhance ocular delivery through the release of MTZ.

Efficacy of different dry eye treatments with artificial tears or ocular lubricants: a systematic review

PURPOSE

To objectively review the outcome of clinical studies where rose bengal stain (RB) has been used as an outcome measure to assess the efficacy of artificial tears (AT) in patients with dry eye.

METHODS

From peer-reviewed articles published between 1947 and 2008, information was sought on dry eye status, as reported using a grading scheme, after use of RB as a diagnostic test, before and after use of a specific regimen of artificial tears or ocular lubricants for approximately 30 days. Mean baseline scores and post-treatment scores were calculated, along with the net change and the percentage change in the RB scores.

RESULTS

From a total of 33 suitable data sets, published between 1985 and 2006, the group mean pre-treatment RB score was 4.25 +/- 1.55 (+/-S.D.), which decreased to 2.84 +/- 1.24 after 30 days of treatment. This represented a net change of -1.43 (95% CI of -1.04 to -1.45). For use of traditional AT (saline, hypromellose, etc), the net change was -0.95, it was -1.33 for use of carbomer (polyacrylic acid) gels and -2.10 for hyaluronic acid (HA) products. These changes represented net improvements of 25.9 +/- 18.4%, 38.0 +/- 20.7% and 41.8 +/- 16.3% respectively. The greater change with HA was not associated with a lower final outcome score, but with higher pre-treatment scores.

CONCLUSIONS

Based on RB grading schemes used by numerous different clinicians over many years, treatment of dry eye with artificial tears or ocular lubricants can be expected to improve the condition of the exposed ocular surface. Assuming no improvement without treatment, a 30 days treatment period can be projected to produce an overall improvement of around 25%, but with no unambiguous statistical differences between product types.

Corneal epithelial permeability of dry eyes before and after treatment with artificial tears

PURPOSE

The question of whether artificial tears can lead to objective improvement of ocular surface disease in dry eyes is still unanswered. The aim of the current study is to assess the influence of artificial tears on corneal epithelial permeability of dry eyes. Furthermore, the effect of benzalkonium chloride, used as a preservative of artificial tears, on corneal epithelial permeability is investigated.

METHODS

The corneal epithelial permeability of 40 dry eye patients (80 eyes) was measured by computerized objective fluorophotometry before and 6 weeks after treatment with artificial tears containing either polyvinyl pyrrolidone 2% without preservative (20 patients) or polyvinyl pyrrolidone 2% preserved with benzalkonium chloride 0.005% (20 patients).

RESULTS

Before treatment, the epithelial permeability of the dry eye patients was found to be 2.7 times that of a control group. After treatment, the epithelial permeability of patients treated with unpreserved polyvinyl pyrrolidone 2% had decreased significantly (-37%; P less than 0.001), whereas patients who had been treated with polyvinyl pyrrolidone 2% preserved with benzalkonium chloride 0.005% showed an increase in epithelial permeability (+21%; P = 0.05%).

CONCLUSION

These data suggest that, in dry eyes, treatment with unpreserved artificial tears may lead to an objective improvement in corneal surface disease. However, this effect may be counteracted by preservation of tear substitutes with benzalkonium chloride.