Home About us Contact
|
Home About us Contact | ||
|
|
||
Healthy Eyes (healthy + eye)
Selected AbstractsOcular penetration of intravenously administered enrofloxacin in the horseEQUINE VETERINARY JOURNAL, Issue 2 2008T. J. DIVERS Summary Reason for performing study: Information on antibiotic concentrations in the equine eye following systemic therapy is limited. Reports that Leptospira spp. are frequently present in the eyes of horses with recurrent uveitis, emphasises a need for studies on ocular concentrations of specific antibiotics. Hypotheses: 1) Enrofloxacin, administered i.v. at 7.5 mg/kg bwt q. 24 h, results in aqueous humour concentrations greater than the reported minimum inhibitory concentration (MIC) for Leptospira pomona. 2) Aqueous humour paracentesis sufficiently disrupts the blood-aqueous humour barrier (BAB) to cause an increase in aqueous humour protein and enrofloxacin concentrations. Methods: Aqueous humour enrofloxacin and total protein concentrations were determined in 6 healthy, mature horses after i.v. administration of enrofloxacin. Paracentesis was performed on the left eye on Days 3 and 4, one hour following enrofloxacin administration, to determine enrofloxacin concentrations in healthy eyes and in eyes with mechanical disruption of the BAB. Paracentesis was also performed on the right eye 23 h after enrofloxacin administration. Blood samples were collected from the horses at identical times to determine enrofloxacin aqueous humour:plasma ratios. Results: Mean ± s.d. enrofloxacin concentration in the aqueous humour one hour post administration on Day 3 was 0.32 ± 0.10 mg/l (range 0.18-0.47); and aqueous humour enrofloxacin, total protein and aqueous humour:plasma enrofloxacin ratios were higher on Day 4 than Day 3. Conclusions and potential relevance: Following disruption of the BAB, enrofloxacin concentrations were above the reported MIC for Leptospira pomona. [source] Numerical analysis of interferograms for evaluation of tear film build-up timeOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 3 2009Dorota H. Szczesna Abstract The lateral shearing interferometer was applied to the in vivo dynamic investigation of the external surface of the pre-corneal tear film after an eye blink. Sequences of interferograms were recorded at a sampling frequency of 25 Hz. Immediately after every eye blink, a bright pattern was observed under the interference fringes. This disappeared after a short time interval (around 0.5,2 s): smooth interference fringes were then observed, corresponding to the creation of a smooth anterior optical surface over the cornea. The purpose of this study is to describe in detail the kinetics of pre-corneal tear film stability and to propose quantitative measures of the stabilisation process in healthy eyes during the 3 s period after a blink. Two methods of quantitative assessment of the tear film build-up time are presented. The first is based upon the evaluation of the inhomogeneity of the background of the interferogram; the second evaluates the orientation of the structure of the background by the analysis of the zero order of the Fast Fourier Transform (FFT) spectrum. The quasi-vertically oriented bright line patterns observed in interferograms immediately after a blink and the mirror-symmetry of their tilts for right and left eyes indicate that the pattern is related to the wiping movements of the upper eyelids during the eye blink. [source] 3422: Sources of straylight in the human eyeACTA OPHTHALMOLOGICA, Issue 2010D DE BROUWERE Purpose Besides refractive aberrations, ocular light scattering is a major parameter affecting image quality on the retina in healthy eyes. Several pathologies in the anterior segment such as corneal scarring and cataract cause significant increase of straylight in the eye. In this study, we link morphologic changes addressed to corneal scarring to a scattering function. Methods Excised rabbit corneas with different grades of scarring following photorefractive keratectomy were optically evaluated for their forward light scattering distribution and consecutively prepared for histology. An absolute parameter for forward scattering was calculated based on the readings in the optical device. We compared this parameter to the relative thickness of the scar tissue observed in the histological data. Results The histological data showed a wide variation of thickness a scar tissue layer in the anterior stroma. The scattering ratio measured using the optical device measuring forward light scattering correlated strongly with the relative thickness of the scar tissue layer with (0.63, Pearson's coefficient), as well as a standard haze exam (measuring backscattered light) (0.51, Pearson's coefficient). The light scattering distribution is narrowly forward peaked (FWHM 30 arcmin), suggesting this light scattering is caused by large particles such as myofibroblasts, oedema or irregular scar tissue in the ablated zone. Conclusion Corneal light scattering associated with the increased amount of haze after excimer laser ablation has a narrowly forward distribution that can be attributed to the subepithelial structures observed in treated corneas. This is in contrast to the origin of scatterers linked to cataract, as small protein aggregates and multilamellar bodies that are scattering over wider angles. [source] 4424: Visual acuity loss with healthy ageing: can it be reversed by wavefront laser?ACTA OPHTHALMOLOGICA, Issue 2010D ELLIOTT Purpose To consider what levels of "super acuity" might be achieved by the correction of ocular aberrations in older patients by wavefront corrected ophthalmic surgery. Note that when comparing visual acuity (VA) of older patients with VA in the young, the average optimal monocular visual acuity of a young subject is about 6/4 (decimal VA 1.50) and not the often quoted ,normal' figure of 20/20 (6/6 or 1.0 decimal). Methods Studies that attempted to isolate the cause(s) of deterioration in visual function with age in normal, healthy eyes were reviewed. Results The majority of studies suggest that the deterioration in visual function with age is primarily due to changes within the neural system rather than optical factors. In addition, several studies have shown increases in ocular aberrations with age, but this is only found when comparisons are made across age groups with fixed pupil sizes. When natural pupil sizes are considered, there is no change in aberrations with age because of age-related pupillary miosis Conclusion There appears to be little scope for ocular aberration correction to be used to counteract the loss of vision with age. Reduced vision in patients with cataract is primarily due to increased forward light scatter, and aberrations play a minor role in reducing vision. Intra-ocular lenses (IOLs) should be designed to keep ocular aberrations at a minimum after cataract surgery, but given that vision loss with age appears to be primarily due to neural changes, there seems little scope for IOLs to improve on the vision of phakic subjects under natural pupil conditions. [source] 2143: Corneal keratocyte population after laser subepithelial keratectomy (LASEK) with mitomycin C (MMC): 3 months vs 15 months comparisonACTA OPHTHALMOLOGICA, Issue 2010P CANADAS SUAREZ Purpose To study corneal keratocyte population after LASEK with mitomycin C (MMC) 15 months vs 3 months after surgery Methods Sixty eyes were included in this study, all of them treated with LASEK with intraoperative 0.02% MMC, divided into 2 groups. 32 eyes had LASEK performed 3 months before, versus 28 in the 15 months post-op group. Keratocyte density was examined by using confocal microscopy in the anterior, mid and posterior stroma in both groups, and the mean density was compared with a control group of healthy eyes Results Keratocyte density in the anterior stroma was 16993,75+ 8001,7 cells/mm3 and 18529,1 + 2917,7 cells/mm3(p=0,3) in the 3 months and in the 15 months groups respectively, in the mid stroma it was 30783,3+ 9300 cells/mm3 in the 3 months and 20754,7 + 3615,3 cells/mm3 in the 15 months groups (p= 0,0001) and 30286,75+ 8321 cells/mm3and 19994+ 3085,9 cells/mm3 (p= 0,0001) in the posterior stroma in the 3 months and in the 15 months groups respectively. The comparison between the average densities through the whole cornea showed statistically significant difference between the 3 months vs 15 months group and 3 months vs normals, but it was not statistically significant different between 15 months vs normals Conclusion The changes in the corneal keratocyte population after LASEK + MMC seen in the early post-op, seem to change towards the normal values 15 months after the procedure. [source] Corneal hysteresis measured with the Ocular Response Analyzer® in normal and glaucomatous eyesACTA OPHTHALMOLOGICA, Issue 1 2010Olivia Abitbol Abstract. Purpose:, To identify differences in corneal hysteresis (CH) and central corneal thickness (CCT) between healthy and glaucomatous patients. Methods:, Retrospective observational study. One hundred and thirty-three eyes of 75 healthy and 58 glaucomatous patients were included. CH was measured in each patient using Ocular Response Analyzer. CCT was determined by ultrasonic pachymetry. For each patient, one eye was randomly selected. We used a Student t -test to search for significant differences between the different groups (p<0.05). Results:, In healthy and glaucomatous eyes, mean CH values were 10.46 ± 1.6 and 8.77 ± 1.4 mm Hg, respectively. Mean CCT values were 560.2 ± 36.3 and 535.3 ± 42.7 ,m, respectively. CH and CCT were significantly lower in glaucomatous eyes than in normal eyes, (p<0.05). Discussion:, In our series, CH was lower in glaucomatous than in normal eyes. The relationship between glaucoma, IOP, and ocular structures may not be confined to the consideration of CCT. A low CH value could be responsible for under-estimation of IOP. CH could also be a risk factor for glaucoma, independent of IOP. Further studies are needed to support these hypotheses. Conclusion:, In our investigation, CCT and CH were significantly lower in glaucomatous eyes than in healthy eyes. [source] Investigating the influence of wavelength, light intensity and macular pigmentation on retinal straylightACTA OPHTHALMOLOGICA, Issue 2009J ROZEMA Purpose To investigate the influence of wavelength, light intensity and macular pigmentation on retinal straylight. This will be tested in both phakic and pseudophakic eyes by means of color filters, as well as by comparing postoperative straylight results of eyes implanted with either clear or blue-blocking IOLs. It has also been suggested in the literature that the yellow macular pigment reduces the effects of the short wavelength components of retinal straylight. Methods In this prospective study the straylight is measured on two groups of pseudophakic subjects: one group of 25 subjects implanted with a clear IOL (Alcon AcrySof SA60AT) and another group of 25 subjects implanted with a yellow IOL (AcrySof Natural SN60AT) using white light as well as with blue, green and red filters. These measurements are repeated on a group of age matched 25 phakic subjects. All retinal straylight measurements will be performed using the Oculus C-Quant straylight meter. In the normal and clear IOL subjects the macular pigment is measured as well using the Tinsley M|Pod device. Results The first, preliminary results demonstrate that in healthy eyes the retinal straylight measured by the Oculus C-Quant depends on the wavelength of the stimulus light. Measurements performed with blue light were lower than those performed in green or red light. Conclusion Stimulus light wavelength appears to have an influence on straylight measurements. Further study on a larger population is required to confirm this trend and to study how IOL color may influence this result in pseudophakic eyes. The possible influence of macular pigment on retinal straylight will be studied simultaneously. [source] Effects of higher-order wavefront aberrations on the eye's depth of focusACTA OPHTHALMOLOGICA, Issue 2008N CHATEAU Purpose To evaluate the impact of higher order aberrations (HOA), defined by individual Zernike polynomial coefficients, on the eye's depth of focus using an adaptive optics (AO) system. Methods A crx1 AO visual simulator (Imagine Eyes, France) was used to introduce different amounts of individual 3rd and 4th order HOA in 10 healthy eyes. These HOA included coma (Z(3,-1)) and trefoil (Z(3,-3)) at magnitudes of +/-0.3 µm, and spherical aberration (SA) (Z(4,0)) at magnitudes of +/-0.3,+/-0.6 and +/-0.9 µm through a fixed 6-mm pupil diameter. A through-focus response (TFR) curve was assessed by recording the percentage of optotype letters of fixed 20/50 size that the subject could identify while these letters were presented at various target distances. Testing was performed under cycloplegia. For each applied HOA, the subject's depth of focus (DoF) and center of focus (CoF) were computed as, respectively, the half-maximum width and the midpoint of the TFR curve. Results The introduction of SA resulted in linearly shifting the CoF by 1.3 D for each 0.5 µm of wavefront. The shift was hyperopic with positive SA, myopic with negative SA. The simulation of either positive or negative SA also had the effect of enhancing the DoF, up to a maximum increase of 2 D with 0.6 µm of SA. The enhancement became smaller when the SA was further increased. Trefoil and coma appeared to neither shift the CoF nor significantly modify the DoF. Conclusion AO technology allowed us to selectively test the visual impact of several HOA on the DoF. The introduction of SA significantly shifted and expanded the subjects' overall DoF. This technique could help in designing optimal corrections for presbyopia and allowing patients to preview refractive surgery outcomes. Commercial interest [source] Diagnostic ability of GDx VCC to discriminate between healthy eyes, ocular hypertensive subjects and glaucoma patientsACTA OPHTHALMOLOGICA, Issue 2007E BORQUE Purpose: To evaluate the diagnostic ability of laser polarimeter GDx VCC to discriminate between healthy eyes, ocular hypertensive subjects and glaucoma patients. Methods: 417 eyes of 417 subjects were included. They were divided into 60 healthy controls, 289 ocular hypertensive subjects and 71 glaucoma patients. The GDx VCC parameters were compared among the study groups using analysis of variance. The receiver operating characteristic (ROC) curves were plotted for TSNIT average, superior average, inferior average, TSNIT standard deviation and nerve fiber indicator (NFI) between control and glaucoma eyes. Results: All evaluated parameters of the GDx VCC showed significant differences between control and glaucomatous eyes and between ocular hypertensive eyes and glaucoma patients. NFI had the greatest area under the ROC curve (AUC=0.881). The AUCs for the inferior average, TSNIT standard deviation and TSNIT average were 0,834, 0.824 and 0.819, respectively. NFI presented a larger AUC than the other GDx VCC parameters. Conclusions: The GDx VCC exhibited a good diagnostic ability to discriminate between healthy and glaucomatous eyes with damage in SAP. The best parameter was NFI. [source] Optic disc biomorphometry with the Heidelberg Retina Tomograph at different reference levelsACTA OPHTHALMOLOGICA, Issue 1 2002Kyösti Vihanninjoki ABSTRACT. Purpose: The Heidelberg Retina Tomograph (HRT) is a confocal scanning laser tomograph that produces high resolution optical section images of the optic disc and central retina. Measurement accuracy and reproducibility is good. Several of the stereometric variables depend on the definition of a reference plane level. The purpose of the present study was to evaluate the four different reference levels in terms of their advantages and disadvantages in clinical work. Methods: Sixty-seven randomly chosen eyes belonging to 67 subjects were included in this study. Forty of the eyes were healthy and 27 had glaucoma. The HRT with software versions 1.09 and 1.11 was used to acquire and evaluate topographic measurements of the optic disc. Image analysis was performed at four different reference levels: 320 µm fixed offset reference level (REFd) (version 1.09), an individually determined reference level (REFi), a papillo-macular reference level (REFm) and a flexible reference level (REFf) (version 1.11). ANOVA was used to determine differences in the topographic parameters between the reference levels. Results: In terms of the healthy eyes, all the variables using different reference levels give rather similar results. However, with advanced glaucoma the measurement values provided with REFd are clearly different to those of the other reference levels. The measurement values using REFm and REFf provide fairly similar results in all clinical groups. REFf indicates the lowest point in the segment between 350° and 356° along the contour line and thus provides the most stable and clinically useful reference level at present. Conclusion: At present, the flexible reference level REFf gives the most reliable and adequate HRT measurement values, both in normal and in glaucomatous eyes. [source] | ||||||||||