Biomedical subjects

Christina Kramann

Publications and source records attributed to Christina Kramann.

4 recordsLinked to original sources

PubMed2005

Repeatability and reproducibility of optic nerve head topography using the retinal thickness analyzer.

OBJECTIVE: The objective was to determine the reproducibility and repeatability of topographic disk parameters with the retinal thickness analyzer (RTA). METHODS: Thirty-nine eyes of 39 healthy subjects were included. Three observers performed three consecutive measurements of optic disk topography independently. Combined repeatability (intra-observer component of variability) and reproducibility (inter-observer component of variability, R and R) was assessed by variance component analysis. RESULTS: Six topographic parameters (disk area, cup area, cup volume, mean cup depth, maximum depth, and cup shape measure) revealed an acceptable repeatability and reproducibility expressed as the percentage of the total measurement variability (range 17.6-28.4%). The average reproducibility and repeatability of all optic disk parameters measured using the RTA was not acceptable (combined R and R = 33.4%). CONCLUSIONS: Repeatability and reproducibility of the optic disk topography analysis using the RTA reveals a high variation, and should, therefore, be interpreted carefully for glaucoma diagnosis and for monitoring the disease.

Adult↗

PubMed2004

[Laser in situ keratomileusis with a flying-spot excimer laser and a carriazo-barraquer microkeratome - outcomes after 6 months].

PURPOSE: To evaluate safety, efficacy, predictability and refractive stability of LASIK, using a flying-spot excimer laser, 91 eyes were examined during a 6-months follow-up. PATIENTS AND METHODS: Consecutively, 91 eyes were enrolled in the study, each eye previously underwent LASIK with the ESIRIS excimer laser (ESIRIS, supplier: eye-tech-solutions Schwind, Kleinostheim, Germany). 91 myopic eyes (mean preoperative refraction: - 5.4 D, range: - 3 to - 13.3 D, astigmatism: - 1 D, range: 1.3 to 3.5 D) were included. A full ophthalmological examination was performed during the first week, 1, 3 and 6 months postoperatively. RESULTS: 26 % of all eyes achieved an uncorrected visual acuity of 0.8, 35 % of 1.0 and 5 % 1.2 6 months postoperatively. 23 % of the eyes lost 1 line of best spectacle-corrected visual acuity (BSCVA), 25 % gained one or more lines of BSCVA. Refraction of 90 eyes were within +/- 1 D of emmetropia 6 months postoperatively. There was no change in spherical equivalent within the interval of 6 months, all eyes were within +/- 0.5 D. CONCLUSION: LASIK with the ESIRIS excimer laser was an effective and safe option with good stability and predictability within the specified interval.

Adult↗

PubMed2003

Corneal model.

PURPOSE: To describe the optical region of the cornea with as few parameters as possible and to compare this approach to commonly used mathematical models for the cornea. SETTING: University eye hospital, Mainz, Germany. METHODS: Corneal surface is approximated by a simple model (SM) that is defined by 2 perpendicular vertex radii, their angle to the horizontal, and a unique numerical eccentricity. These parameters, together with a parameter quantifying the decentration of the recording, are obtained in a consistent fit of corneal topographic data. The SM is compared to Zernike polynomial approximations of the 4th (Z4 model) and 8th (Z8 model) radial orders. Residual refraction errors for these approximations are calculated by numerical ray tracing, allowing a comparison of the different approaches. The statistical evaluation was carried out in 100 healthy eyes. RESULTS: The model approximation accuracy for the SM was at least as high as the reproducibility of the topographic measurements. For small optical zones up to 4.0 mm in diameter, the SM was on average more accurate than the Z4 model. CONCLUSIONS: The parameters of the SM, which are closely related to conventional parameters of the cornea, provided a highly accurate basis for following refractive interventions (customized corneal or cataract surgery). Zernike polynomials tend to improve peripheral optical quality at the expense of the central quality. Except in cases of technical optics, this is an unwanted effect in the human eye.

Adolescent↗

PubMedDate not supplied

Is homelessness a risk factor for eye disease? Results of a German screening study.

BACKGROUND: There is general agreement on the presence of a correlation between poverty and impaired health. However, only scarce data are available on whether this also applies to the incidence of eye disease. The present study was carried out to evaluate the prevalence of ocular disease in homeless people in Germany. METHODS: 107 homeless people (97 male, 10 female; mean age 49 years, range 18-81 years) treated in specialised social service institutions were investigated prospectively according to a standardised ophthalmological screening protocol. This comprised visual acuity, assessment of pupillary light reaction, intra-ocular pressure, slit lamp examination as well as funduscopy. RESULTS: The median best-corrected visual acuity of all 213 eyes examined was 0.8 (range: no light perception to 1.25). 74 eyes of a subgroup of 50 patients showed one or more of the following disorders: 32% of the patients suffered from external eye disease, 8% exhibited a cataract associated with a visual acuity of 0.63 or below. 6% of the patients had optic nerve atrophy, and 4% suffered from amblyopia. Diabetic retinopathy as well as age-related macular degeneration were detected in 2%, while anophthalmos, lid malposition and traumatic choroidal rupture were noted in 1% of patients. The median visual acuity measured in these 74 eyes was 0.5 (range: no light perception to 1.25), which differs significantly from the acuity of 0.8 in the entire study population (p < 0.001). The prevalence of legal blindness according to WHO criteria was 2%. CONCLUSIONS: The present study revealed an unexpectedly high prevalence of optic nerve atrophy in homeless people. The prevalence for cataract and legal blindness was slightly higher than in representative epidemiological investigations. Thus, homelessness seems to be correlated with an increased ocular morbidity. As best-corrected visual acuity differed significantly between eyes with and those without eye disease, the assessment of this parameter may serve as a cost-effective first-stage screening method.

Adolescent↗