Penetration of 0.3% ciprofloxacin, 0.3% ofloxacin, and 0.5% moxifloxacin into the cornea and aqueous humor of enucleated human eyes.

We aimed to quantify the penetration of ciprofloxacin, ofloxacin, and moxifloxacin into the cornea and aqueous humor of cadaver eyes. A total of 60 enucleated eyes, not eligible for corneal transplantation, were divided into three groups and immersed in commercial solutions of 0.3% ciprofloxacin, 0.3% ofloxacin, or 0.5% moxifloxacin for 10 min. Whole corneas and samples of aqueous humor were then harvested and frozen, and drug concentrations analyzed by liquid chromatography tandem mass spectrometry. The mean corneal concentration of moxifloxacin was twice as high as ofloxacin, and the latter was twice as high as ciprofloxacin. The mean concentration of moxifloxacin in the aqueous humor was four times higher than the other antibiotics, and the mean concentrations of ciprofloxacin and ofloxacin were statistically similar. The amount of drug that penetrated the anterior chamber after a 10-min immersion was far below the safe limit of endothelial toxicity of each preparation. Moxifloxacin demonstrated far superior penetration into the cornea and anterior chamber of cadaver eyes compared to ciprofloxacin and ofloxacin. One should not expect endothelial toxicity with the commercial eye drops of ciprofloxacin, ofloxacin, and moxifloxacin that reach the anterior chamber through the cornea.

Penetration of 0. 3% ciprofloxacin, 0. 3% ofloxacin, and 0. 5% moxifloxacin into the cornea and aqueous humor of enucleated human eyes

We aimed to quantify the penetration of ciprofloxacin, ofloxacin, and moxifloxacin into the cornea and aqueous humor of cadaver eyes. A total of 60 enucleated eyes, not eligible for corneal transplantation, were divided into three groups and immersed in commercial solutions of 0.3% ciprofloxacin, 0.3% ofloxacin, or 0.5% moxifloxacin for 10 min. Whole corneas and samples of aqueous humor were then harvested and frozen, and drug concentrations analyzed by liquid chromatography tandem mass spectrometry. The mean corneal concentration of moxifloxacin was twice as high as ofloxacin, and the latter was twice as high as ciprofloxacin. The mean concentration of moxifloxacin in the aqueous humor was four times higher than the other antibiotics, and the mean concentrations of ciprofloxacin and ofloxacin were statistically similar. The amount of drug that penetrated the anterior chamber after a 10-min immersion was far below the safe limit of endothelial toxicity of each preparation. Moxifloxacin demonstrated far superior penetration into the cornea and anterior chamber of cadaver eyes compared to ciprofloxacin and ofloxacin. One should not expect endothelial toxicity with the commercial eye drops of ciprofloxacin, ofloxacin, and moxifloxacin that reach the anterior chamber through the cornea.

Maintenance of the corneal epithelium is carried out by germinative cells of its basal stratum and not by presumed stem cells of the limbus

The purpose of this investigation was to analyze the proliferative behavior of rabbit corneal epithelium and establish if any particular region was preferentially involved in epithelial maintenance. [3H]-thymidine was injected intravitreally into both normal eyes and eyes with partially scraped corneal epithelium. Semithin sections of the anterior segment were evaluated by quantitative autoradiography. Segments with active replication (on) and those with no cell division (off) were intermingled in all regions of the tissue, suggesting that the renewal of the epithelial surface of the cornea followed an on/off alternating pattern. In the limbus, heavy labeling of the outermost layers was observed, coupled with a few or no labeled nuclei in the basal stratum. This suggests that this region is a site of rapid cell differentiation and does not contain many slow-cycling cells. The conspicuous and protracted labeling of the basal layer of the corneal epithelium suggests that its cells undergo repeated cycles of replication before being sent to the suprabasal strata. This replication model is prone to generate label-retaining cells. Thus, if these are adult stem cells, one must conclude that they reside in the corneal basal layer and not the limbal basal layer. One may also infer that the basal cells of the cornea and not of the limbus are the ones with the main burden of renewing the corneal epithelium. No particular role in this process could be assigned to the cells of the basal layer of the limbal epithelium.

Maintenance of the corneal epithelium is carried out by germinative cells of its basal stratum and not by presumed stem cells of the limbus.

The purpose of this investigation was to analyze the proliferative behavior of rabbit corneal epithelium and establish if any particular region was preferentially involved in epithelial maintenance. [3H]-thymidine was injected intravitreally into both normal eyes and eyes with partially scraped corneal epithelium. Semithin sections of the anterior segment were evaluated by quantitative autoradiography. Segments with active replication (on) and those with no cell division (off) were intermingled in all regions of the tissue, suggesting that the renewal of the epithelial surface of the cornea followed an on/off alternating pattern. In the limbus, heavy labeling of the outermost layers was observed, coupled with a few or no labeled nuclei in the basal stratum. This suggests that this region is a site of rapid cell differentiation and does not contain many slow-cycling cells. The conspicuous and protracted labeling of the basal layer of the corneal epithelium suggests that its cells undergo repeated cycles of replication before being sent to the suprabasal strata. This replication model is prone to generate label-retaining cells. Thus, if these are adult stem cells, one must conclude that they reside in the corneal basal layer and not the limbal basal layer. One may also infer that the basal cells of the cornea and not of the limbus are the ones with the main burden of renewing the corneal epithelium. No particular role in this process could be assigned to the cells of the basal layer of the limbal epithelium.

Restoration of the rabbit corneal surface after total epithelial debridement and complete limbal excision.

How is the corneal epithelium restored when all of it plus the limbus have been eliminated? This investigation explored the possibility that this may be achieved through the conjunctival epithelium. The corneal epithelium of the right eye of 12 rabbits (Oryctolagus cuniculus) was totally scraped followed by surgical excision of the limbus plus 1.0-1.5 mm of the adjacent conjunctiva. Antibiotics and corticosteroids were applied for 1 week after surgery. Histological and immunohistochemical techniques were used to monitor the events taking place on the eye surface 2 weeks and 1, 3 and 6 months thereafter. Initially, the corneal surface was covered by conjunctival-like epithelium. After 1 month and more prominently at 3 and 6 months an epithelium displaying the morphological features of the cornea and reacting with the AE5 antibody was covering the central region. It is likely that the corneal epithelium originated from undifferentiated cells of the conjunctiva interacting with the corneal stroma.

Corneal astigmatism measuring module for slit lamps.

We have developed an automatic keratometer module for slit lamps that provides automatic measurements of the radii of the corneal curvature. The system projects 72 light spots displayed in a precise circle at the examined cornea. The displacement and deformation of the reflected image of these light spots are analysed providing the keratometry. Measurements in the range of 26.8-75 D can be obtained and a self-calibration system has been specially designed in order to keep the system calibrated. Infrared LEDs indicate automatically which eye is being examined. Volunteer patients (492) have been submitted to the system and the results show that our system has a high correlation factor with the commercially available manual keratometers and the keratometry measurements from a topographer. Our developed system is 95% in agreement with the corneal topographer (Humphrey--Atlas 995 CZM) and the manual keratometer (Topcon OM-4). The system's nominal precision is 0.05 mm for the radii of curvature and 1 degree for the associated axis.

System for measuring the transmission spectrum of 'in vitro' corneas.

We have developed a spectroscopy system dedicated to eye banks in order to standardize the evaluation of the donated corneas, with respect to their transparency. The system for measuring the corneal transmission spectrum basically consists of a conventional spectroscopy single beam optical apparatus, with particularities in order to attend to the needs of the eye banks, having a linear CCD (2048 sensors) as a detector. The range of evaluation of the system is from 400 to 700 nm, which is the range of interest for these kinds of sample (corneas). Dedicated software has been developed in order to acquire the data from the system and to provide the graphical interface for the user. The software is quite easy to manipulate and provides the diagnostic with respect to the transparency of the cornea, which is based on research done in association with the clinicians of the Eye Bank of Hospital das Clínicas de Ribeirão Preto (Brazil). The system presents a resolution of 9 nm (which is good enough for this kind of measurement, that presents large bandwidths) and it is in agreement with the spectra obtained from commercial spectrophotometers (the correlation factor between our system and a Beckman DU-70 is 0.995 43 for samples of well defined bandwidths, and 0.989 73 for corneas--large bandwidth).

Detection system for ocular refractive error measurement.

An automatic and objective system for measuring ocular refractive errors (myopia, hyperopia and astigmatism) was developed. The system consists of projecting a light target (a ring), using a diode laser (lambda = 850 nm), at the fundus of the patient's eye. The light beams scattered from the retina are submitted to an optical system and are analysed with regard to their vergence by a CCD detector (matrix). This system uses the same basic principle for the projection of beams into the tested eye as some commercial refractors, but it is innovative regarding the ring-shaped measuring target for the projection system and the detection system where a matrix detector provides a wider range of measurement and a less complex system for the optical alignment. Also a dedicated electronic circuit was not necessary for treating the electronic signals from the detector (as the usual refractors do); instead a commercial frame grabber was used and software based on the heuristic search technique was developed. All the guiding equations that describe the system as well as the image processing procedure are presented in detail. Measurements in model eyes and in human eyes are in good agreement with retinoscopic measurements and they are also as precise as these kinds of measurements require (0.125D and 5 degrees).

The exact solution for the centre thickness of spectacle and contact lenses.

The available methods for the exact calculation of centre thickness presuppose that one knows simultaneously both surfaces of the lens and that the lens' power is determined afterwards. However, this approach is of secondary importance in practical situations. The issue in daily practice is the determination of the centre thickness of lenses that already have explicit vertex powers. In such cases one can set only one surface. The other has to be calculated following the prescription, the known surface and the optical effect of the centre thickness. Exact solution for this problem leads to four expressions, reflecting the number of ways one can treat it. Two of them are complete second-order algebraic equations and the other two, complete third-order algebraic equations. The practical value of the latter is limited by the fact that one cannot always obtain their three roots by pure algebraic procedures.

Addition of obliquely crossed spherocylindrical lenses.

This paper presents a three-step method for the addition of obliquely crossed spherocylinders. Contrary to other methods it does not require algorithms or complicated abstract concepts to secure the consistency of the results.

HP program for the center thickness of convex spectacle lenses.

A HP program for a quick and precise determination of the center thickness of convex spectacle lenses is presented. The program uses 150 lines of programming and 10 storage registers. With the exception of the center thickness and one of the surface powers all the other parameters must be known.

Sindrome de Adie e lente multifocal. / Adie's syndrome and multifocal lens

Descricao de um caso tipico de sindrome de Adie. Durante o periodo de convalescencia, garantiu-se uma boa cooperacao binocular mediante o uso de lente multifocal no olho afetado. Pacientes com grande exigencia visual podem ser grandemente beneficiados com esse procedimento

Medida da posicao ocular durante a anestesia geral. / Measurement of eye position during general anesthesia

O autor descreve algumas opcoes metodologicas para a determinacao da posicao ocular no paciente submetido a anestesia geral. Conclue que as medidas das distancias do canto interno da rima palpebral a porcao nasal do limbo corneo-escleral sao particularmente uteis na avaliacao das variacoes da posicao ocular durante a anestesia geral