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N Ehlers

Publications and source records attributed to N Ehlers.

At least 19 recordsLinked to original sources
PubMed1998

Paired arcuate keratotomy for congenital and post-keratoplasty astigmatism.

PURPOSE: To study the effect of arcuate keratotomy on corneal astigmatism in previously grafted eyes compared to eyes with naturally occurring astigmatism. SUBJECTS AND METHODS: Twenty-three eyes with naturally occurring astigmatism and 21 eyes with post-keratoplasty astigmatism were treated by arcuate keratotomies in the steepest corneal meridian. Visual acuity, spherically equivalent refraction, and refractive cylinder were measured before surgery and 1 to 10 years after the operation. RESULTS: The preoperative refractive cylinder was reduced from 5.0 dioptres (median) to 1.25 dioptres in eyes with natural astigmatism and from 7.0 dioptres to 3.25 dioptres in post-keratoplasty eyes. Spherical equivalent refraction changed from -0.6 dioptres to -1.5 dioptres in eyes with natural astigmatism and from -3.5 dioptres to -4.5 dioptres in previously grafted eyes. The induced change in astigmatism, as calculated by Fourier analysis, correlated strongly with the existing preoperative astigmatism. The effect of the procedure did not correlate with the type of astigmatism (congenital vs. post-keratoplasty), time after surgery, or with patient age or sex. CONCLUSION: Arcuate keratotomy is a simple procedure to reduce naturally occurring astigmatism as well as induced astigmatism after keratoplasty. Parallel to the astigmatic change, negligible changes in the spherical equivalent are induced.

Adolescent↗
PubMed1998

Endothelial cell loss after photorefractive keratectomy for myopia.

PURPOSE: To study the long-term effect of 193 nm excimer laser photorefractive keratectomy (PRK) on the human corneal endothelial cell density. SUBJECTS AND METHODS: One hundred and twenty-four eyes from 71 patients underwent photorefractive keratectomy for myopia or myopic-astigmatism. Endothelial cell density was examined a short time before the operation and on an average of 50 months after the operation using a contact specular microscope. A subgroup of 32 eyes from 20 patients treated only once was examined preoperatively and 7 and 52 months postoperatively. The endothelial cell densities were corrected for the changing magnification of the contact specular microscope with changing central corneal thickness and for the expected physiological cell loss with time. RESULTS: The average endothelial cell density was preoperatively 3098+/-283 cells/mm2 (mean+/-SD) and postoperatively 3048+/-294 cells/mm2 corresponding to a change of -50+/-157 cells/mm2. This was statistically significantly different from zero in a paired t-test (n=124, t=3.58, 2p<0.001). The average changes in endothelial cell density for the subgroup were -34+/-159 cells/mm2 for the postoperative time interval 0-7 months and -20+/-188 cells/mm2 for the postoperative time interval 7-52 months. These results were not statistically significantly different from zero in a paired t-test (n=32, t=1.21 and t=0.60, 2p>0.05). A statistically significant negative correlation between preoperative cell density and the change in cell density was found (n=124, r=-0.21, 2p<0.05). CONCLUSION: This study suggests a potentially harmful effect of PRK on the human corneal endothelium. It appears that most cells are lost during ablation or within the first period of time after PRK.

Adult↗
PubMed1998

A morphological and functional study of Congenital Hereditary Endothelial Dystrophy.

PURPOSE: To contribute to the basic understanding of Congenital Hereditary Endothelial Dystrophy (CHED) by clinical, functional, and histopathological examinations of three cases. METHODS: Prior to grafting, corneas were evaluated by slit lamp examination and by assessment of endothelial permeability to fluorescein. Following penetrating keratoplasty, corneal buttons were evaluated by light- and electron microscopy and by assessment of stromal swelling pressure. RESULTS: Patients with CHED had a markedly increased corneal thickness (0.93-0.98 mm) with epithelial oedema and a stromal swelling pressure close to zero; suggesting that the stroma was maximally swollen in vivo. Corneal endothelium showed an increased permeability to fluorescein; suggesting a functional barrier defect. Histopathological evaluation revealed: 1) a normal endothelial cell density; 2) an abnormal endothelial morphology with irregular and multi-nucleated cells containing abnormal cell organelles; and 3) a profound thickening of Descemet's membrane, 16-18 microm, with multiple focal areas of abnormal fibrillar deposits in the posterior half. CONCLUSIONS: This study suggests that the primary defect in patients with CHED is a degenerated and dysfunctional corneal endothelium, characterized by an increased permeability and an abnormal and accelerated Descemet's membrane secretion. The underlying pathophysiological mechanism(s) may be related to an abnormal endothelial barrier function, leading to secondary swelling of the stroma and epithelium. Further studies are needed to identify the specific functional defect(s) and the embryological origin of the abnormal corneal endothelium in CHED.

Adolescent↗
PubMed1998

Chemotaxis of human keratocytes is increased by platelet-derived growth factor-BB, epidermal growth factor, transforming growth factor-alpha, acidic fibroblast growth factor, insulin-like growth factor-I, and transforming growth factor-beta.

PURPOSE: Following corneal wounding, early migration of keratocytes into the wound area is of pivotal importance in the healing process, but the nature of this migration is not well understood. The influence of peptide growth factors on the chemotactic and chemokinetic migration of human corneal keratocytes was investigated, using the following growth factors: platelet derived growth factor-BB (PDGF-BB), epidermal growth factor (EGF), transforming growth factor-alpha (TGF-alpha), acidic fibroblast growth factor (aFGF), basic fibroblast growth factor (bFGF), insulin-like growth factor-I (IGF-I), and transforming growth factor-beta-1 (TGF-beta 1). METHODS: The chemotactic stimulation was investigated in the Boyden blind-well chemotaxis chamber, and the chemokinetic effect of the growth factors determined by a modified checker-board analysis. RESULTS: PDGF-BB, EGF and TGF-beta 1 stimulated chemotaxis towards a peak value, with a subsequent decline at higher concentrations. PDGF-BB and EGF peaked at 1 ng/ml with a 2.0 and a 2.5-fold increase respectively in the number of keratocytes migrating, whereas TGF-beta 1 reached a maximum response at 0.1 ng/ml, with a 1.7-fold increase. Chemotaxis reached an early plateau and remained constant at concentrations between 1 ng/ml and 100 ng/ml when stimulating with TGF-alpha (2.7-fold), bFGF (2.0-fold), aFGF (2.7-fold), and IGF-I (4.5-fold). Checkerboard analysis revealed that all growth factors were chemotactic agents for human keratocytes, except bFGF, which principally stimulated chemokinesis. CONCLUSION: These in vitro results demonstrate that PDGF-BB, EGF, TGF-alpha, aFGF, IGF-I, and TGF-beta 1 increase keratocyte chemotaxis, and they may play an important role in the early recruitment of keratocytes to the corneal wound site in vivo.

Becaplermin↗
PubMed1997

[Biomechanical study of corneal stability after photorefractive keratectomy].

BACKGROUND: Photorefraktive keratectomy (PRK) is the most frequent refractive surgical procedure worldwide. The central corneal thickness is reduced due to removal of the anterior stroma, including Bowman's layer, with a laser beam. This procedure results in considerable alterations of the corneal structure. What does this mean for the mechanical properties of the cornea? METHODS: Intraocular pressure was increased via a 180 degrees tilt. Before and during this procedure, corneal topography was measured by photokeratoscopy. We examined 26 patients after PRK and 25 controls who had not undergone any surgical procedure. RESULTS: The corneal center flattened by 0.038 +/- 0.05 dpt (P > 0.05) in the PRK patients and by 0.187 +/- 0.045 dpt (P < 0.05) in the control group. PRK patients within 1 year after operation showed a minimal central corneal steepening, whereas PRK patients after more than 1 year showed a reaction similar to that in normal corneas (P < 0.05). CONCLUSION: Corneal stability is altered after PRK. After 1 year corneal stability seems to normalize due to stromal remodelling.

Adult↗
PubMed1997

Keratocyte migration and peptide growth factors: the effect of PDGF, bFGF, EGF, IGF-I, aFGF and TGF-beta on human keratocyte migration in a collagen gel.

PURPOSE: Peptide growth factors are known accelerators of corneal wound healing, probably mediated through increased proliferation of the cells; however, information about their effect on keratocyte motility is lacking. The influence of peptide growth factors on keratocyte migratory activity was investigated, using the following growth factors: platelet derived growth factor (PDGF-BB), epidermal growth factor (EGF), acidic fibroblast growth factor (aFGF), basic fibroblast growth factor (bFGF), insulin-like growth factor-I (IGF-I) and transforming growth factor-beta-1 (TGF-beta 1). METHODS: Keratocytes were seeded on gels of type 1 collagen, growth factor added, and the cells left to migrate for 72 hours. Subsequently, the number of keratocytes at the different levels in the collagen gel was evaluated by optically sectioning the gel at 20 microns, intervals, with an inverted phase contrast microscope. RESULTS: PDGF, EGF and bFGF at 10 ng/ml, all increased the number of keratocytes at the different levels of the gel as compared to a non-stimulated control (p < 0.05 or p < 0.01, students t-test). TGF-beta proved to be a strong inhibitor of keratocyte migration, decreasing the number of keratocytes observed at every level in the gel (p < 0.05 and p < 0.01, students t-test), whereas no effect of IGF-I and aFGF was found. During the 72 hours of migration, no contraction of the collagen gels was observed. Autoradiography of histological sections of the gels showed that during the 72-hour period only TGF-beta and 10% fetal bovine serum induced an increase in keratocyte proliferation. CONCLUSION: PDGF, EGF and bFGF increase keratocyte migration, independent of proliferation in a collagen gel invasion assay and might promote corneal wound healing, not only by increasing cell proliferation, but also through increased motility.

Autoradiography↗
PubMed1997

Persisting corneal oedema following intracapsular cataract extraction.

PURPOSE: The purpose of this study was to reveal the frequency of persisting corneal oedema following intracapsular cataract extraction and at the same time to examine whether the survival rate after penetrating keratoplasty due to this diagnosis differs from the survival rate following penetrating keratoplasty due to primary Fuchs' endothelial dystrophy. METHODS AND MATERIAL: A series of 2455 eyes underwent intracapsular cataract extraction between January 1, 1986 and December 31, 1988, at the Department of Ophthalmology, Arhus University Hospital. The medical files were examined to study the frequency of persisting corneal oedema. Patients with persisting corneal oedema were offered penetrating keratoplasty and the survival rate following this procedure was calculated. RESULTS: The frequency of pseudophakic persisting corneal oedema was 5.3% in the group of patients who underwent intracapsular cataract extraction. The survival of the following corneal transplantation was 54% after 2 years of follow-up. This is a low survival rate compared to the survival rate in primary Fuchs' endothelial dystrophy, but there is a similarity to this disease in a development of a slowly progressive oedema in 17% compared to 13% in primary Fuchs' endothelial dystrophy. CONCLUSION: 5.3% of a group of patients who underwent intracapsular cataract extraction developed persisting corneal oedema within a 5 to 7-year follow-up period. When these patients underwent penetrating keratoplasty the survival rate of the graft was 54% after 2 years of follow-up.

Cataract Extraction↗
PubMed1997

Value of intraoperative keratometry in predicting outcome of radial keratotomy.

PURPOSE: To investigate whether the immediate change in corneal power during radial keratotomy correlates with the long-term postoperative change in subjective refraction, and thereby being predictive for refractive outcome. METHODS: Manual keratometry was performed on 45 consecutively operated eyes of 45 young persons with myopia of 5 dioptres and less and immediately after radial keratotomy. Automated keratometry and subjective spherical equivalent refraction were investigated during a follow-up period of 6 months and correlated to the intraoperative keratometric measurements. RESULTS: On average, the majority of the change in corneal curvature after radial keratotomy took place within 1 min. There was no correlation between the intraoperative curvature change and the changes in curvature measured up to 6 months after surgery. There was a weak significant positive correlation between intraoperative curvature change and the change in subjective refraction at 6 months after surgery (R = 0.48, p < 0.01). The prediction error in estimating subjective refractive changes from intraoperative keratometry changes was, however, similar in patients who had bilateral radial keratotomy. Inclusion of such fellow-eye information together with the age of the patient in a multiple linear regression analysis increased the correlation coefficient from 0.48 to 0.75. CONCLUSIONS: The change in central corneal curvature takes place within minutes after corneal incision. As a single parameter, intraoperative keratometry cannot be used for titrating surgery. Information from the results of first eye radial keratotomy surgery with intraoperative keratometry is, however, predictive for radial keratotomy in the second eye. These findings suggest that a large source to refractive variability after radial keratotomy is related to individual patient factors, such as corneal biomechanics and wound healing.

Adult↗
PubMed1997

Graft survival and risk factors of penetrating keratoplasty for microbial keratitis.

PURPOSE: To evaluate graft survival rates and prognostic factors in relation to penetrating keratoplasty for microbial keratitis. METHODS: The records of 95 patients treated with penetrating keratoplasty for microbial keratitis during a twenty-year period were reviewed. Data were analysed by construction of survival curves using the Kaplan-Meier non parametric method. RESULTS: The overall survival of a clear cornea was 72% after one year, 71% after two years and 52% after five years. A significantly lower survival rate (p<0.05) was found in the presence of preoperative local risk factors such as wear of contact lenses and trauma and in inflamed eyes. In contrast, systemic diseases like diabetes, cancer or rheumatoid arthritis did not affect survival and neither did recipient age nor the degree of vascularization of the eye. Male donor buttons showed superior survival compared to female ones (p < 0.05), while females seemed to constitute the best recipients. Recurrence rates of microbial keratitis postoperatively were 11%, 16% and 24% after one, two and five years, respectively. Corresponding graft rejection rates were 9%, 15% and 27%. CONCLUSIONS: Patients suffering from microbial keratitis have a relatively high risk of graft failure. To improve the prognosis care should be taken to minimize local risk factors. Surgery should whenever possible be performed on quiet eyes. The unexpected finding of a better prognosis for male donor buttons might suggest the preferred use of male donors in patients suffering from microbial keratitis, but the observation needs further documentation.

Adolescent↗
PubMed1997

Comparison of objective methods for quantifying the refractive effect of photo-astigmatic refractive keratectomy using the MEL-60 excimer laser.

PURPOSE: To investigate the accuracy and precision of automated keratometry, automated refractometry, and computerized corneal topography in estimating the subjective refractive outcome of photo-astigmatic refractive keratectomy six months postoperatively. METHODS: Photo-astigmatic refractive keratectomy (Aesculap-Meditec, MEL-60 Excimer Laser) was performed on 26 eyes with a preoperative myopia ranging from -4.0 to 7.6 dioptres, and a naturally occurring astigmatism from 0.75 to 5.0 dioptres. Six months postoperatively refractive outcome was evaluated by automated keratometry, automated refractometry (Nikon NRK-8000), computerized topography (TMS-1), and subjective refraction. Estimate errors were computed as the difference between the change in subjective refraction and the change in automated keratometry, automated refractometry, and surface topography, respectively. Astigmatic changes were evaluated by the second harmonic component in the Fourier series analysis. RESULTS: Subjective spherical as well as cylindrical values were reduced significantly six months postoperatively. The estimate error (mean +/- one standard deviation) for automated keratometry was -1.26 +/- 0.72 dioptres for the spherical equivalent and -1.36 +/- 1.02 dioptres for the cylinder; for automated refractometry it was -0.78 +/- 0.91 dioptres for the spherical equivalent and -0.66 +/- 0.92 dioptres for the cylinder. The best estimates of subjective changes were obtained when the average of ring 2 and 3 of the topographic data was used: -0.15 +/- 0.82 dioptres for the spherical equivalent and -0.78 +/- 0.80 dioptres for the cylinder. CONCLUSIONS: The computerized topographer with the Fourier analysis was superior to automated keratometry and automated refractometry in estimating the subjective spherical refractive outcome and comparable to automated refractometry in estimating the subjective cylinder refractive outcome after photo-astigmatic refractive keratectomy.

Adult↗
PubMed1997

Topography of corneal grafts before and after penetrating keratoplasty.

PURPOSE: Refractive error after penetrating keratoplasty is a major clinical problem. The purpose of the present study was to investigate whether the topography of the donor cornea influence the topography of the graft after transplantation. METHODS: Twenty-five donor corneas were measured with a video-keratograph (TMS-1): in situ and before and after organ culture. Clinical video-keratographic images of the transplanted grafts were subsequently obtained one week, 1, 3, 6, 12, and 24 months after surgery. The central spherical equivalent power and corresponding regular and irregular astigmatic powers were computed. RESULTS: A statistically significant correlation between spherical equivalent central donor power and spherical equivalent central graft power after keratoplasty was found at all times up to two years after surgery. Only 13-50% of the variation in post-keratoplasty spherical graft power could, however, be explained by the donor graft power. Corresponding 95% confidence limits for prediction of post-keratoplasty power from donor graft power were approximately +/- 6.5 diopters. Post-keratoplasty regular or irregular corneal astigmatism did not correlate with astigmatism in the donor graft. CONCLUSION: Corneal donor graft spherical equivalent power does influence the spherical equivalent corneal power after keratoplasty, especially during the first months after surgery. The dependency is, however, not very strong and until other determinants of post-keratoplasty corneal shape are known and controllable, 'power-typing' of donor corneas appears to be of limited clinical use.

Adolescent↗
PubMed1996

Significant effect of high-resolution HLA-DRB1 matching in high-risk corneal transplantation.

The effect of HLA matching in corneal transplantation is still--after numerous of studies--disputable. We investigated the effect of DRB1 matching in high-risk cases with vascularization and/or retransplantation. Only class II antigens were matched because we were unable to obtain donor lymphocytes for HLA typing. Typing was performed on DNA isolated from the ocular tissues up to 24 hr after death. When this study was initiated, DNA-based methods had been developed only for class II typing. The first part of the study concerns 74 cases with at least 3 years of observation fully matched for 17 DRB1 specificities detected using restriction fragment-length polymorphism. This showed an improved long-term graft survival of 72% compared with 45% in a historical control group of 23 comparable cases. In the second part of the study, stored DNA samples from the restriction fragment-length polymorphism-matched donor-recipient pairs were subjected to retyping with a new method based on sequence-specific polymerase chain reaction. It was possible to split DRB1*01, *04, and *11 in 3, 14, and 5 alleles, respectively. The matching was then re-assigned taking all splits into account. This showed that 36 cases had at least one incompatibility, whereas 38 cases were fully compatible. The long-term graft survival rate was 79% in the matched group compared with only 59% in the mismatched group, which is significantly different at P=0.032. This retrospective, but blinded, randomized study is strong evidence for the effect of matching and may give scope for international collaboration to obtain completely matched corneas for this group of patients.

Adult↗
PubMed1996

[Diagnosis and treatment of conjuncitivitis].

Conjunctivitis is a frequent reason for consulting a doctor. Most often treatment consist of antibiotics, even though sensitive bacteria are only rarely demonstrated. In our part of the world conjunctivitis is self-limiting, and it may be worth considering the effect of treatment, if any. With this in mind, diagnosis and differential diagnoses are reviewed, and with regard to treatment distinctions are made between neonatal conjunctivitis (gonococcus, chlamydia, virus), conjunctivitis in children (symptoms of upper respiratory tract infections), and conjunctivitis in adults and the elderly (dry eyes, epiphora in ectropion).

Adult↗
PubMed1996

[Biomechanical study of corneal stability after radial keratotomy].

BACKGROUND: Radial Keratotomy is one of the most frequent refractive surgical procedures performed worldwide. It results in considerable alterations of the corneal structure. What does this mean for the mechanical properties of the cornea? METHODS: Intraocular pressure was increased via a 180 degrees tilt. Before and during this procedure, corneal topography was measured by photokeratoscopy. We examined 36 patients after RK and 25 controls who had not undergone any surgical procedure. RESULTS: The corneal center flattened by 0.523 +/- 0.054 dpt (p < 0.01) in the RK patients and by 0.187 +/- 0.045 dpt (p < 0.05) in the control group. CONCLUSION: Even several years after radial keratotomy, corneal stability is still decreased.

Adult↗
PubMed1996

The effect of 193 nm excimer laser radiation on the human corneal endothelial cell density.

The effect of 193 nm excimer laser radiation on human corneal endothelial cell density was examined. Fifty-five eyes from 35 patients underwent photorefractive keratectomy for myopia. Photomicrographs of the endothelium were taken a short time before the operation and on an average of 7 months postoperatively with a specular microscope. The average endothelial cell densities were preoperatively 3375 +/- 266 cell/mm2 (mean +/- SD) and postoperatively 3348 +/- 287 cells/mm2, corresponding to a fall of 27 cells/mm2 (N = 55). This fall in endothelial cell density was not statistically significant. A significant correlation between the change in cell density and age of the patient was found, with older patients losing more cells (N = 35, 2p < 0.05). The magnification of the specular microscope was found to change with corneal thickness. The importance of correcting the endothelial cell densities for corneal thickness is discussed.

Adolescent↗
PubMed1996

Epithelial healing in the second eye after corneal abrasion.

Corneal epithelial healing velocity was determined in patients admitted to excimer laser photo refractive keratectomy, by daily video planimetry of the denuded area until complete healing. The epithelial healing process was followed in fellow eyes with regard to intervals between surgery of the two eyes of 1 to 10 weeks. In cases where the fellow eye was treated at one week after the first eye, the lesions healed significantly faster in the second eye as compared to patients with longer delay between the two operations.

Adult↗
PubMed1996

[Diagnosis and treatment of conjunctivitis].

Conjunctivitis is a frequent reason for consulting a doctor. Most often treatment consists of antibiotics, even though sensitive bacteria are only rarely demonstrated. In our part of the world conjunctivitis is self-limiting, and it may be worth considering the effect of treatment, if any. With this in mind, diagnosis and differential diagnoses are reviewed and with regard to treatment distinctions are made between neonatal conjunctivitis (gonococcus, chlamydia, virus), conjunctivitis in children (symptoms of upper respiratory tract infections), and conjunctivitis in adults and the elderly (dry eyes, epiphora in ectropion).

Administration, Topical↗