Improvement of the ocular surface using hypotonic 0.4% hyaluronic acid drops in keratoconjunctivitis sicca.

BACKGROUND: The ocular surface changes of keratoconjunctivitis sicca (KCS) could be the result of the effect of an altered tear film on the epithelial environment. PURPOSE: To evaluate the possibility of improving the environmental conditions of the ocular surface by lowering tear osmolarity, increasing tear film volume and stabilising the tear film. Also, to study the effect of such an improvement on the epithelial cells of the ocular surface. METHODS: One hundred and thirty-five patients with a diagnosis of KCS were treated on a randomised basis with either unpreserved hypotonic 0.4% hyaluronic acid (HHA) eye drops or 0.3% hydroxypropylmethylcellulose plus 0.1% Dextran 70 (HPMC) eye drops 6 times a day for 60 or 90 days. In all patients a Schirmer I test, break-up time (BUT), ocular surface staining with 1% Bengal Rose, or 2% fluorescein, as well as subjective symptoms, were recorded before and 15, 30 and 60 days after the beginning of the study. Patients were divided into three subgroups and the effect of the treatment was studied using three different techniques: the tear ferning test, conjunctival impression cytology and tear osmolarity measurement. RESULTS: Improvements in BUT, vital staining, Schirmer I and symptoms were recorded in both groups of treatment, with significant differences for patients treated with 0.4% HHA. On day 60, 30 min after installation: tear ferning patterns changed from 100% pathological (types III-IV) to 93% physiological (types I-II) in the 0.4% HHA group and from 100% pathological to 78% physiological in the 0.3% HPMC group (p < 0.01 between groups). Tear osmolarity shifted from 353 +/- 23 to 305 +/- 6 mosmol/l in the 0.4% HHA group and from 346 +/- 15 to 336 +/- 8 mosmol/l in the 0.3% HPMC group (p < 0.001 between groups). On day 90, the impression cytology score improved from 1.2 to 1.9 in the 0.4% HHA group while it did not change in the 0.3% HPMC group (p < 0.05 between groups). CONCLUSION: In KCS appropriate treatment with a hypotonic 0.4% HHA tear substitute can change the tear environment and results in improvement of the epithelial conditions of the ocular surface.

Pharmacological profile of a new topical pilocarpine formulation.

A new formulation based on pilocarpine hyaluronate salt has been shown to improve the bioavailability of the drug and to extend the duration of activity. We evaluated the extent of intraocular pressure reduction, the duration of action and the kinetics of miotic response of this formulation in comparison with a commercial preparation with the same drug concentration. Ocular hypertension in the rabbit was induced by alpha-chymotrypsin or by water loading. The hypotensive effect of the new formulation treatment was significantly greater and longer than that observed in rabbit eyes treated with the commercial preparation both in the normotensive and in the hypertensive animals. Furthermore, we evaluated the miotic response in normotensive rabbits showing a greater miotic response and an extended duration when the eyes were treated with the new formulation. The pharmacological profile of the new formulation described in this study indicates an increase of efficacy and duration of action compared to the commercial preparation.

Noise power spectra of images from digital mammography detectors.

Noise characterization through estimation of the noise power spectrum (NPS) is a central component of the evaluation of digital x-ray systems. We begin with a brief review of the fundamentals of NPS theory and measurement, derive explicit expressions for calculation of the one- and two-dimensional (1D and 2D) NPS, and discuss some of the considerations and tradeoffs when these concepts are applied to digital systems. Measurements of the NPS of two detectors for digital mammography are presented to illustrate some of the implications of the choices available. For both systems, two-dimensional noise power spectra obtained over a range of input fluence exhibit pronounced asymmetry between the orthogonal frequency dimensions. The 2D spectra of both systems also demonstrate dominant structures both on and off the primary frequency axes indicative of periodic noise components. Although the two systems share many common noise characteristics, there are significant differences, including markedly different dark-noise magnitudes, differences in NPS shape as a function of both spatial frequency and exposure, and differences in the natures of the residual fixed pattern noise following flat fielding corrections. For low x-ray exposures, quantum noise-limited operation may be possible only at low spatial frequency. Depending on the method of obtaining the 1D NPS (i.e., synthetic slit scanning or slice extraction from the 2D NPS), on-axis periodic structures can be misleadingly smoothed or missed entirely. Our measurements indicate that for these systems, 1D spectra useful for the purpose of detective quantum efficiency calculation may be obtained from thin cuts through the central portion of the calculated 2D NPS. On the other hand, low-frequency spectral values do not converge to an asymptotic value with increasing slit length when 1D spectra are generated using the scanned synthetic slit method. Aliasing can contribute significantly to the digital NPS, especially near the Nyquist frequency. Calculation of the theoretical presampling NPS and explicit inclusion of aliased noise power shows good agreement with measured values.

Fatty acid use in glaucomatous optic neuropathy treatment.

The authors have studied the efficacy of an association of DHA, vitamin E and vitamin B complex (TROFINERV) in glaucomatous patients. The parameters evaluated were computerized visual field (CVF) and retinal contrast sensitivity (RCS). Thirty chronic simple glaucoma patients in good tensional compensation with local therapy were given TROFINERV oral therapy. The results show significant differences after 90 days of treatment both in the perimetric indices (MD, SF, CPSD; p < 0.05) and in the RCS frequency values (p < 0.05). In the light of the results obtained, the authors consider the use of such association to be a useful support in glaucomatous patient therapy for preventing or delaying the progress of damage.