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Biomedical subjects

T Seiler

Publications and source records attributed to T Seiler.

At least 19 recordsLinked to original sources
PubMed1992

Repeated excimer laser treatment after photorefractive keratectomy.

Scarring or undercorrection occurs in a small percentage of patients after myopic photorefractive keratectomy. Scarring occurred in 1.8% of 298 patients with a baseline myopia of 6.0 diopters or less, increasing to 8.8% in those with corrections of more than 6.0 D. Undercorrection of more than 1 D occurred in 2.7% of the eyes with a baseline myopia of up to -6.0 D. A much greater incidence of undercorrection (30% to 40%) was found after corrections of more than 6.0 D. Thirty eyes in 30 patients were reoperated because of scarring (11 eyes) and/or undercorrection (27 eyes) and were observed for 6 to 18 months (average, 7.8 months). Only one of the eyes has shown mild scar formation after this second laser treatment. Sixty-three percent of these patients had a manifest refraction between -1.0 D and +1.0 D six months after reoperation. Repeated phototablation seems to be a valuable technique for treatment of undercorrection and/or scarring after photorefractive keratectomy.

Adult↗
PubMed1992

[Complications of laser keratomileusis with the excimer laser (193 nm)].

Complications of photorefractive keratectomy (PRK) for myopia correction are presented based on 615 procedures with a follow-up of up to 2 years. Intraoperative complications with experienced surgeons are extremely rare. The used laser system worked without technical failures for the last 18 months. Gross eccentricities of the ablative zone (1.0 mm to 1.5 mm) occurred in two eyes (0.3%). Also, epithelial disorders are very rare. Recurrent erosions did not occur. Increased intraocular pressure due to the postoperative steroid medication (dexamethasone 0.1% or prednisolone 1%) was manifest in about 30% in patients with a baseline myopia of up to -9.0 D. In myopia over -9.0 D the incidence of steroid glaucoma was about 50%. Steroid responders reveal an increased risk of overcorrection. Subepithelial haze is a common symptom after PRK. Scarring interfering with vision correlates with the amount of attempted correction: up to 6.0 D the incidence of scars is about 0.5% and increases to more than 10% in corrections of more than 10 D. Also, undercorrections of more than 1 D depend strongly on the attempted correction. The most severe complication was a noninfectious corneal ulcer in a patient with systemic lupus erythematosus. Therefore, autoimmune and connective-tissue diseases represent an absolute contraindication for PRK. Corrections of more than 6.0 to 7.0 D should be considered as a relative contraindication for PRK at this time.

Adult↗
PubMed1992

[Space-occupying lesions of the orbit: modern imaging diagnosis].

The paper summarises imaging of orbital diseases by CT and MRI. As localisation is an important clue to differential diagnosis in orbital tumours, the different pathologies are described according to sites of prevalent occurrence. Morphological criteria of orbital pathology are described, and the more frequent entities are illustrated.

Diagnosis, Differential↗
PubMed1992

Diurnal variation in refraction after excimer laser photorefractive keratectomy.

Diurnal fluctuations in vision are common after radial keratotomy (RK), associated with a myopic change in refraction and keratometric power mostly in the morning. After photorefractive keratectomy (PRK), only a small percentage of patients report fluctuations of vision. We tested ten such patients who had undergone excimer laser PRK with regard to refraction, keratometry, and visual acuity 5 to 20 months after surgery. Patients were examined five times during one day from 8:00 a.m. to 8:00 p.m. Ten volunteers serving as a control group were examined following the same protocol. None of the patients showed an increase in minus spherical power of the manifest refraction between morning and evening. The change in manifest refraction from morning to evening was +0.3 D +/- 0.3 D, which was not significantly different from the control group. The change in refraction did not correlate with keratometric power, follow-up time of age of the patients.

Adult↗
PubMed1992

Pseudoexfoliation syndrome and glaucoma. Does glaucoma capsulare exist?

Pseudoexfoliation syndrome (PES) is seen in patients with a characteristic deposition of material on the anterior preequatorial region of the lens and on a variety of surfaces throughout the anterior segments of the eye. A high frequency of associated glaucoma has also been reported. In spite of numerous clinical and histological investigations, the mechanisms for the glaucoma are unclear. In a series of 5154 patients referred to our hospital for cataract extraction we found a prevalence of 6.1% (n = 314). In 51 of these patients (16.2%) glaucoma was diagnosed in contrast to 33 patients (10.9%) in an age-matched control group. The prevalence of glaucoma in PES patients and the control group was not statistically different, so our findings in cataract patients do not support the interpretation that there is a clinical entity called "glaucoma capsulare."

Aged↗
PubMed1992

[Analysis of photo-ablation products of excimer and erbium:YAG laser treated human corneas. Combined gas chromatography/mass spectroscopy].

The photoablation products from human cadaver corneas treated with an excimer laser (192 nm) or an erbium: YAG laser (2.94 microns) were qualitatively analyzed using a combined gas chromatography mass spectrometry (GC/MS) system. GC/MS is the most sensitive analyzing system in use today for molecules with a relative molecular mass of 40 to 400. More than 20 different types of molecules were detected; most of them were identified as alkanes. Comparison of the two types of laser showed larger fragments and fewer different types of molecules after excimer laser treatment than after erbium: YAG photoablation. We postulate that the smaller molecules after erbium: YAG treatment indicate a greater heat during photoablation than with excimer laser treatment.

Alkanes↗
PubMed1992

Pterygium excision using 193-nm excimer laser smoothing and topical mitomycin C.

A total of 31 eyes with primary pterygium and 24 eyes with recurrent pterygium underwent surgical treatment and were followed for at least 1 year. The surgery involved a conventional bare-sclera technique combined with excimer laser smoothing of the wound bed. Postoperatively, the eyes were medically treated with topical mitomycin C (0.02%) for 4 days and with steroids for several weeks. No recurrence was noted within the 1st year in the primary pterygium group, whereas recurrence was observed in 3/24 eyes that had been treated for recurrent pterygium, equivalent to a recurrence rate of 12.5% in this subgroup. Nine eyes (16.4%) had gained 2 lines or more in visual acuity by 1 year after surgery. Granuloma developed in 3 eyes, and dellen formation was detected in 1 eye after surgery. The combination of surgical management with local mitomycin therapy may be considered to be a safe and effective technique for the removal of pterygium. Although the visual results were good, the role of excimer laser smoothing in the treatment of this disorder needs further investigation.

Female↗
PubMed1992

[Dye laser coagulation of diabetic maculopathy].

Eighty eyes of 48 patients were followed after laser photocoagulation (615 nm) of the macula because of diabetic macular edema. The follow-up time was at least 6 months (average 10.2 months). The morphological status improved in more than 60% of eyes with focal edema but in only 40% of eyes with diffuse macula edema. Improvement of distance visual acuity was obtained in 35% of the eyes, mostly in those with good baseline acuity (greater than or equal to 0.7). The fraction with improved visual acuity decreased to 13% in eyes with a baseline acuity of 0.6 or less. Similar results were found for near visual acuity. The discrepancies between morphological and functional improvement are still unclear.

Adult↗
PubMed1992

[The Excimer laser. An instrument for corneal surgery].

Photoablation of the cornea using excimer lasers (193 nm) results in keratectomies with very precise edges and minimal damage to the adjacent tissue. Deep keratectomies for relaxation incisions (astigmatic correction) and for trephination (lamellar or penetrating keratoplasty) are possible, but have not been applied routinely. Superficial keratectomies can induce corneal flattening--a promising approach for correction of myopia. This unique keratorefractive technique, called photorefractive keratectomy (PRK), has been studied worldwide with a follow-up time of up to 2 years. The success rate (+/- 1 D from the refraction aimed at) is approximately 90%, and vision-threatening complications are extremely rare. However, this is true only in corrections of up to -6.0 D. Corrections of more than this result in a significant decrease in the refractive success and a tremendous increase in complications. Therefore, we believe that corrections of more than -6.0 D are clinically not acceptable. Long-term stability is not yet proven, and consequently PRK must be used with strict indications. Superficial scars, corneal dystrophies, and degenerations of the outer cornea can be removed with the excimer laser much more gently than with conventional techniques.

Adult↗
PubMed1992

Gas chromatographic and mass spectroscopic analysis of excimer and erbium: yttrium aluminum garnet laser-ablated human cornea.

The photoablative products from human cadaver corneas treated with lasers were investigated using gas chromatography and mass spectroscopy. The photoablations were done separately with an excimer laser (193 nm) and with an erbium: yttrium aluminum garnet (Er:YAG) laser (2.94 microns). More than 20 different types of molecules with a molecular weight of 40-400 mass units could be identified, most of which were found to be alkanes. The comparison of the two types of laser ablations showed larger fragments and fewer types of molecules present after excimer laser treatment than after Er:YAG photoablation.

Cornea↗
PubMed1991

[Refractive surgery of the cornea. Corneal surgery--an alternative to optical aids?].

Errors of refraction of the eye can be corrected not only by means of spectacles, contact lenses or intra-ocular lenses, but also by operative procedures on the cornea. At present, correction of myopia is accomplished with radial keratotomy (RK), a procedure that achieves the best results in the range up to - 6.0 diopters. However, on account of its side effects, in particular poor predictability, the method is no true alternative to the use of optical aids. Epikeratoplasty done to correct hyperopia and aphakia, is even more imprecise, and should only be employed in exceptional cases. Laser surgery of the cornea is still undergoing clinical testing, but has already produced promising results.

Astigmatism↗
PubMed1991

Myopic photorefractive keratectomy with the excimer laser. One-year follow-up.

To evaluate the efficacy, predictability, and stability of myopic photorefractive keratectomy (PRK), the authors completed a 1-year follow-up study on a consecutive series of 26 sighted eyes undergoing this procedure. The results of this follow-up are presented. In addition, side effects and complications in another 255 sighted eyes with a follow-up of 3 months to 1 year are reported to judge the safety of the procedure. Twenty-four of 26 eyes (92%) were within +/- 1.0 diopter (D) of the intended final refraction (baseline, -1.4 to -9.25 D). Fifty-eight percent of the eyes were stable within +/- 0.25 D between 6 and 12 months. One year after surgery, none of the patients lost or gained more than one line of best corrected (spectacle) visual acuity. Uncorrected visual acuity improved to 20/40 or better in 96% of the eyes and to 20/20 or better in 48% of the eyes (not including the eyes that were intentionally undercorrected). However, visual acuity with glare decreased from 20/27 preoperatively to 20/31 after 1 year. Scarring occurred in 2.8% of the treated corneas. Risk factors for scarring include noncompliance with postoperative steroid medication, high myopic corrections, and high steroid responders (3.1%). Collagen vascular and other autoimmune diseases are a contraindication for PRK.

Adult↗
PubMed1991

[Excimer laser keratomileusis for myopia correction. Results and complications].

Results of excimer laser keratomileusis in 26 myopic sighted eyes are presented. The follow-up was at least 9 months. The base-line refraction was -4.48 +/- 1.81 D (range: -1.4 to -9.25 D). After 3 months 85% were within +/- 1 D from the intended refraction. The such defined success rate after 6 months was 87.5%, after 9 months 88%, and after 12 months 92%. One month after surgery we found an overcorrection of +1.45 +/- 1.22 D decreasing to +0.27 +/- 0.94 D at three months, becoming an undercorrection of -0.24 +/- 0.76 D after six, and -0.32 +/- 0.69 D after nine months, and of -0.36 +/- 0.6 D after one year. Stability within the measurement error (+/- 0.25 D) appeared in 79% of the treated eyes six months after treatment. Three patients have been excluded from the study group because they did not follow the protocol. Subepithelial haze occurred in all patients, becoming most intense after 3 months, gradually clearing over the next months. With appropriate steroid medication, the refractive effect may be modulated. Complications as steroid glaucoma, recurrent erosion, loss of acuity, or extensive corneal scarring seem to be very rare.

Adult↗
PubMed1991

[Wound healing of the cornea of New World monkeys after surface keratectomy: Er:YAG-excimer laser].

Corneal wound healing was studied after photoablation with an excimer laser (193 nm, 43 pulses at 180 mJ/cm2 [symbol: see text] 11 microns ablation depth, optical zone 2.0 mm) and with an erbium-YAG laser (2.94 microns, 5 pulses at 2.5 J/cm2 [symbol: see text] 50 microns ablation depth, optical zone 1.6 mm). The corneas of marmosets (Callithrix jacchus) were prepared 5 and 10 days and 4 and 25 weeks after photoablation. The sections were investigated by conventional light microscopy or exposed to antibodies against collagen types I, III, IV, VII and laminin and stained by indirect immunofluorescence. Macroscopically, the time-course of wound healing was comparable to that seen, after laser keratomileusis for correction of myopia in humans (epithelium closure after 24-48 h, subepithelial haze: erbium-YAG less than or equal to excimer). Histologically the time-course of wound healing could be schematically divided into three phases: (1) epithelial hyperplasia, inhomogeneous new synthesis of collagen fibrils subepithelially; (2) reorganization of the epithelium, hyperplasia of keratocytes, incipient reorganization of the collagen fibrils, increase in subepithelial haze; (3) reorganization of the collagen fibrils, decrease in subepithelial haze. The distribution of collagen type VII during the corneal wound healing suggests that the subepithelial haze observed during the healing process after laser keratomileusis for correction of myopia is based on the anchoring fibrils of the basement membrane.

Animals↗
PubMed1991

[Laser coagulation of the cornea with a holmium:YAG laser for correction of hyperopia].

We present a new technique of hyperopic correction similar to radial thermokeratoplasty. A pulsed Ho: YAG laser was used that emitted radiation at 2.06 microns and was guided by a quartz fiber and a focusing hand piece. The penetration depth of this light in the cornea is about 400 microns. Eight or 16 concentric point coagulations result in steepening in the central cornea. This refractive change is inverse related to the distance to the cornea center, and it increases linearly with increasing laser pulse energy. In four blind eyes it was demonstrated that the parameters evaluated in cadaver eyes can be transferred to living eyes. Surprisingly, the refractive change so created of up to 5 dpt is stable within a period of 4 months. Immediately after surgery, concentric descemet folds can be detected, which gradually decrease within the period reported.

Cornea↗
PubMed1991

[Photoablation with the Er:YAG laser in ocular tissues].

Photoablation of ocular tissues is not restricted to the excimer laser. Alternative tools are erbium lasers. As there is maximum absorption in ocular tissue at about 3 microns, two types of erbium lasers are capable of photoablation. One is the Er:YAG laser working at a wavelength of 2.94 micron; the other is the Er:YSGG laser emitting light with a wavelength of 2.79 microns. Both lasers produce higher ablation rates than the excimer laser. In comparison to the excimer laser (thermal damage of less than 1 micron), there is more thermal damage in the remaining tissue (3 microns). The lower ablation rate of the Er:YSGG laser due to the greater distance of the wavelength from the absorption maximum can be compensated by a higher output energy and a higher repetition rate (25 Hz). Wound-healing studies in rabbit corneas show no significant differences between the excisions performed with the Er:YAG laser and 193 nm excimer laser.

Cornea↗
PubMed1990

[Emmetropization. A statistical study].

The relations between bulb length and the refractive power of the cornea were investigated in 3358 eyes of nonselected patients. There was a negative correlation between corneal refraction and bulb length in the range 19 to 29 mm. However, the data do not support the recently advanced hypothesis that corneal curvature and bulb length are regulated by means of optimal retinal contrast. The mean bulb length in males was 23.83 mm, in females 23.25 mm.

Cataract Extraction↗