Biomedical subjects

Barbara Link

Publications and source records attributed to Barbara Link.

6 recordsLinked to original sources

PubMed2006

Measurement of autofluorescence in the parapapillary atrophic zone in patients with ocular hypertension.

PURPOSE: The purpose of the study was to investigate area and intensity of parapapillary autofluorescence in patients with ocular hypertension and controls. PATIENTS AND METHODS: Forty-two consecutive patients with ocular hypertension and 25 controls were investigated in a controlled prospective cross-sectional trial. All patients and controls were members of the Erlangen Glaucoma registry and received complete ophthalmologic examination and detailed standardized glaucoma examination, including 24-h IOP measurement, perimetrie (G1, three phases) and 15 degrees stereographic slides of the optic disc. Additionally, patients and controls were investigated with VEP with blue on yellow pattern stimulation and confocal scanning laser ophthalmoscope (HRA II, Heidelberg Engineering, Dossenheim, Germany) to detect lipofuscin in the parapapillary atrophic zone. Eyes with retinal diseases or pathologic changes of retinal pigmentepithelium were excluded. Extension of parapapillary area with increased autofluorescence compared (qualitatively) to background autofluorescence around the optic disc and the level of autofluorescence (quantitatively) in the area of qualitatively increased autofluorescence was measured. Patients and controls did not differ significantly concerning age. RESULTS: The area of parapapillary autofluorescence was significant larger in patients with ocular hypertension than in the control group (0.21+/-0.17 mm(2) versus 0.07+/-0.06 mm(2); P<0.001, Mann-Whitney U-test). An increased latency of blue-on-yellow pattern VEP was seen in patients with OHT with increasing parapapillary autofluorescence area (r=0.496; P<0.001, Spearman-Rho test). CONCLUSION: Parapapillary autofluorescence is increased in patients with ocular hypertension. Patients with large area of parapapillary autofluorescence had also an increased latency in blue on yellow pattern VEP.

Cross-Sectional Studies↗

PubMed2006

Pattern reversal ERG and VEP--comparison of stimulation by LED, monitor and a Maxwellian-view system.

PURPOSE: Pattern stimulation is widely used to detect inner retinal dysfunction. In this work we describe a pattern stimulation technique with LEDs and compare the results with conventional methods. METHODS: PERG and VEP were derived from three normal subjects. Three different techniques were used to generate a checkerboard pattern reversal stimulus: a 70 Hz monitor, a Maxwellian-view system equipped with a Xenon-arc lamp and a mechanical mirror system, and a LED array (Roland Consult) consisting of 100 white LEDs. Two kinds of luminance (125 and 340 cd/m2) and four temporal frequencies (4, 8, 12 and 24 reversals per second) were studied on three healthy subjects. Additionally, a luminance tuning experiment (30, 60, 90, 125 and 340 cd/m2) was performed on one subject. RESULTS: Comparison of different stimulation techniques shows reproducible responses of PERG and VEP with all three methods. The LED array leads to slightly smaller amplitudes than both other techniques, which we ascribe to the design of the LED field. No difference of peak times or phases was noticed between different stimulation techniques. A luminance dependency of PERG and VEP is noticeable using stimulation with LED: with decreasing luminance we measured increasing peak times of PERG and VEP and decreasing amplitude of PERG. CONCLUSION: We conclude that central retinal stimulation with checkerboard pattern reversal is possible with LED. It gives comparable results to monitor and Maxwellian-view system.

Adult↗

PubMed2006

Pattern reversal ERG with LED-stimulation using cyclic summation technique.

PURPOSE: Multifocal pattern reversal stimulation can be used to detect inner retinal dysfunction. Commonly, the stimulus is generated on a monitor using m-sequence technique. We describe a pattern reversal ERG evoked by LED arrays using cyclic summation (CS). METHODS: One eye of eight healthy subjects was examined with an arrangement of 13 LED arrays. Each array consisted of 100 LEDs separated by thin walls. One of the fields was placed centrally, three fields each were placed above, below, left and right of the central field. CS technique at a temporal frequency of 16 reversals per second (RPS) was used for stimulation. Viewing distance was 30 cm, check size was 0.58 cyc/deg. Luminance of the bright fields was 340 cd/m2. RESULTS: Fourier analysis was performed. Centrally, the amplitude of the 2nd harmonic wave was highest (0.87 microV). In the first paracentral fields, amplitudes were 0.28 microV (nasally), 0.21 microV (superior, inferior and temporally). In the second paracentral fields, amplitudes were 0.11 microV (nasally), 0.09 microV (superior), 0.13 microV (inferior) and 0.15 microV (temporally). With exception of the temporal field (0.1 microV), in the outermost fields no reproducible ERG response could be recorded. CONCLUSION: Peripheral ERG responses to a pattern reversal stimulus can be recorded with LED stimulation using CS technique up to an eccentricity of 30 degrees. Responses are highest centrally and decrease with increasing distance to the centre.

Adult↗

PubMed2006

Pupillographic measurements with pattern stimulation: the pupil's response in normal subjects and first measurements in glaucoma patients.

PURPOSE: This study was undertaken to characterize the influence of contrast, luminance, and spatial frequency of a pattern stimulus on the pupil reaction of healthy subjects. First measurements with this technique in patients with glaucoma were compared with those in a control group. METHOD: Grating patterns were presented using a Maxwellian-view system to study series of contrast, luminance, and spatial frequency in three healthy subjects. The best two stimulus conditions were determined and were then used to examine 19 patients with open-angle glaucoma and 16 control subjects. RESULTS: In healthy subjects, an increasing contrast led to an increase in amplitude and a decrease in latency of the pupil reflex. Increasing luminance also resulted in an increase in the amplitude. The offset component of the pupil reflex was most pronounced at low spatial frequencies and the onset component at high spatial frequencies. When healthy subjects were compared with patients with glaucoma, control subjects generally had higher amplitudes, velocity, and acceleration of pupil constriction than did the patients with glaucoma. These differences were significant when the test was performed with a spatial frequency of 6.25 cyc/deg. CONCLUSIONS: Best stimulus conditions to elicit a pupil response to a pattern grating stimulus are 100% contrast and 55 cd/m(2) mean luminance. The choice of the spatial frequency determines which component of the pupil reflex is more pronounced. Differences between patients with glaucoma and healthy control subjects are demonstrable.

Contrast Sensitivity↗

PubMed2005

Long-term outcome of excimer laser phototherapeutic keratectomy for treatment of Salzmann's nodular degeneration.

PURPOSE: To describe the technique and evaluate the long-term success of excimer laser phototherapeutic keratectomy (PTK) for treatment of Salzmann's nodular degeneration. SETTING: Department of Ophthalmology, University of Erlangen-Nürnberg, Erlangen, Germany. METHODS: This retrospective study comprised 22 eyes of 14 patients who consecutively had PTK for superficial corneal opacities in Salzmann's nodular degeneration between January 1990 and November 2003. In all cases, the nodules and as much pannus tissue as possible were removed with a hockey knife. Afterward, the laser ablation (MEL 60 or 70, Carl Zeiss-Meditec) was performed with repeated application of masking fluid to remove further scar tissue and smooth the surface. Intended depth of laser ablation ranged from 10 to 100 microm (mean: 41 microm +/- 43 [SD]). RESULTS: In 86% of eyes, visual acuity improved after PTK, from 0.4 +/- 0.2 preoperatively to 0.7 +/- 0.3 postoperatively. The mean myopic shift was 1.5 +/- 0.7 diopters [D]. Median refractive cylinder changed from 1.0 D preoperatively to 0.7 D postoperatively. The median surface regularity index/surface asymmetry index (SRI/SAI) of the TMS-1 topography analysis system (Tomey) decreased from 2.0/1.6 preoperatively to 1.2/1.2 postoperatively. In 4 (18%) of 22 eyes, a recurrence had to be treated by repeat PTK during a mean follow-up of 2.0 +/- 1.8 years. CONCLUSIONS: Results indicate that PTK is an effective and safe procedure for treatment of Salzmann's nodular degeneration. Laser ablation should be combined with prior mechanical removal of nodules and excessive pannus tissue.

Adult↗

PubMed2005

Salzmann's nodular degeneration of the cornea: a review and case series.

Salzmann's nodular degeneration is a rare, noninflammatory, slowly progressive, degenerative condition. Bluish-white nodules raised above the surface of the cornea characterize it. It has usually developed in corneas with a history of phlyctenulosis, trachoma, vernal keratoconjunctivitis, measles, scarlet fever, and various other viral diseases. However, today the majority of cases have been seen without recognized previous keratitis. It is composed of dense irregularly arranged collagen tissue with hyalinization between epithelium and Bowman's layer or beyond. Manual removal, phototherapeutic keratectomy (PTK) with or without the use of topical mitomycin-C, lamellar or penetrating keratoplasty have been used in the treatment of this disease. Salzmann's nodular degeneration does not seem to consist of one clinical entity. In some cases, elevated and pannus-like tissue can be separated easily from the corneal surface leaving Bowman's layer almost untouched. In these eyes, subsequent PTK may be necessary to smooth the surface. Recurrences are rare in these eyes. In contrast, some eyes (often with major peripheral vascularization) are left with deep defects in Bowman's layer and superficial stroma after difficult mechanical removal of nodules. In these eyes, multiple masking/laser ablation procedures are mandatory to acquire a homogenous surface. In our experience, the required laser ablation depth is significantly greater and the best-corrected visual acuity to be expected is reduced in contrast to the eyes with easy removal of the nodules. In these eyes recurrences seem to occur more frequently after treatment. Of 35 eyes documented to have Salzmann's nodular degeneration during the last 15 years in our department, 22 needed PTK treatment. Visual acuity increased from 0.4 to 0.7 on average. As a routine, laser ablation should be combined with previous conventional removal of nodules and excessive pannus tissue. By doing so, lamellar and penetrating keratoplasty techniques are hardly ever required in those eyes.

Cornea↗