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Biomedical subjects

S Trokel

Publications and source records attributed to S Trokel.

At least 19 recordsLinked to original sources
PubMed1998

Evaluation of night vision disturbances in contact lens wearers.

PURPOSE: We quantitatively recorded and evaluated night vision disturbances with physiologically dilated pupils. We compared the amount of image degradation experienced in eyes wearing spherical soft contact lenses with the amount of image degradation experienced by subjects wearing spectacles. METHODS: We prospectively evaluated 69 eyes from 35 myopic subjects with no ocular pathology. The subjects ranged in age from 22 to 35 years. We designed a test to quantitatively record image degradation with physiologically dilated pupils in scotopic conditions of dim ambient light. Previously, we have shown that this test accurately measures image degradation. We used this test to compare image degradation between new spherical soft contact lens and spectacle correction. Hyperopes and eyes with greater than 1.50 D of astigmatism were excluded. RESULTS: Adequately correcting myopic refractive error decreased recorded image degradation (P < or = 0.0001). There was no significant difference in the amount of image degradation between spectacle trial frames and new spherical soft contact lenses (P < or = 0.2885). CONCLUSIONS: Our test offers an objective method of assessing night vision disturbances in contact lens wearers. Our results suggest that image degradation, which may contribute to the sensation of glare experienced by some patients, is influenced equally by contact lens and spectacle correction.

Adult↗
PubMed1995

The barrier function in neodymium-YAG laser capsulotomy.

BACKGROUND: Complications following neodymium (Nd)-YAG laser capsulotomy have been attributed to damage to the capsule and vitreous face. OBJECTIVES: To measure the disruption of the anterior-posterior extracapsular barrier complex induced by Nd-YAG laser capsulotomy and to determine how it might be minimized, using a fluorophotometer. DESIGN: Prospective study of 21 eyes undergoing Nd-YAG laser capsulotomy and cross-sectional comparison with 15 pseudophakic eyes with clear capsules. SETTING: University-based clinical practice. INTERVENTION: Neodymium-YAG laser posterior capsulotomy per study protocol. MAIN OUTCOME MEASURE: Change in extracapsular barrier efficiency as measured by fluorophotometry. RESULTS: Multivariate regression demonstrated that both anterior vitreous disruption and absence of a posterior chamber intraocular lens (aphakia) were significantly correlated with loss of barrier efficiency, whereas capsulotomy size was not. The anterior vitreous was judged to be undamaged in 67% of eyes treated by the study protocol. However, all myopic eyes sustained damage. Opacification of the posterior capsule itself was also associated with mild loss of barrier function even before capsulotomy, compared with the clear-capsule group. Glaucoma occurred more frequently when barrier efficiency was lost postoperatively. CONCLUSION: Damage to the extracapsular barrier complex by Nd-YAG laser capsulotomy is minimized when the anterior vitreous is preserved. The study treatment protocol may be useful in limiting this damage and in reducing complications.

Aqueous Humor↗
PubMed1993

Orbital fat removal. Decompression for Graves orbitopathy.

BACKGROUND: Orbital decompression has been used to describe surgical procedures that remove some portion of the orbital walls to reduce pressure on the orbital contents. Substantial morbidity associated with these procedures includes infraorbital anesthesia, worsened extraocular motility, globe displacement, and blindness. The authors believe that orbital contents also may be decompressed by removing orbital fat. METHODS: Eighty-one patients with nonactive Graves orbitopathy were selected for orbital fat decompression based on the presence of proptosis and associated signs and symptoms to avoid bone removal. Soft-tissue analysis by computed tomography (CT) scan showed distended pockets of fat extending into the intraconal space, which were removed through medial-upper and lateral-lower anterior orbitotomies. Decompression with bone removal was reserved for those few patients with compressive optic neuropathy unresponsive to medical treatment and those patients with residual deforming exophthalmos after fat removal. RESULTS: One hundred fifty-eight fat decompressions were performed on 81 patients over 9 years. The authors measured an average reduction in proptosis of 1.8 mm (range, 0-6.0 mm). The greatest average reduction in proptosis (3.3 mm) was produced in patients with preoperative Hertel measurements of greater than 25.0 mm. Morbidity was limited to temporary motility impairment of the inferior oblique in two patients. CONCLUSION: The concept of orbital decompression can include removal of orbital fat to reduce proptosis, eliminate symptoms, and improve appearance with far less morbidity than when bone decompression is used as the primary decompressive procedure.

Adipose Tissue↗
PubMed1991

Treatment of acute Graves orbitopathy.

The therapeutic options for the treatment of acute Graves orbitopathy include high-dose oral corticosteroids, surgical decompression, and radiotherapy. The former two treatments are associated with significant morbidity. Although there have been a number of reports of the efficacy of radiotherapy, its role in the management of this disease is still questioned. The authors reviewed 84 cases of acute Graves orbitopathy treated with either high-dose systemic corticosteroids or radiotherapy (2000 rad to each involved orbit). Radiotherapy resulted in significant improvement in subjective and objective signs of orbital congestion and was more effective than high-dose corticosteroids in relieving compressive optic neuropathy. Of the patients with compressive optic neuropathy, only 1 of 29 treated with radiotherapy required surgical decompression, whereas, 6 of 16 treated with corticosteroids required surgery. This study suggests that radiotherapy has greater efficacy and fewer complications than high-dose systemic corticosteroids in the treatment of acute Graves orbitopathy.

Acute Disease↗
PubMed1990

The barrier function in extracapsular cataract surgery.

The distribution of fluorescein between the anterior chamber and the anterior vitreous was measured in two groups of patients after oral administration: group I, extracapsular cataract extraction (ECCE) patients with intact capsule and posterior chamber intraocular lens (PC IOL) (n = 12); group II, intracapsular cataract extraction (ICCE) patients with anterior chamber IOL (AC IOL) (n = 13). The fluorescein concentrations were measured by fluorophotometry and the penetration ratios were calculated. The penetration of fluorescein into the anterior vitreous was significantly less in the ECCE group (group I, penetration ratio = 2.03 +/- 1.00 X 10(-3) min-1; group II, penetration ratio = 5.99 +/- 4.89, X 10(-3) min-1, P less than 0.01). The authors concluded that in ECCE versus ICCE a significantly smaller proportion of fluorescein is found in the anterior vitreous relative to the aqueous after passage through the blood-aqueous barrier. This suggests a barrier to posterior movement of other molecules that may initially gain access to the eye in the anterior segment (e.g., prostaglandins).

Aged↗
PubMed1989

Evolution of excimer laser corneal surgery.

Interest in the potential of the excimer laser for refractive surgery was generated by a series of experiments performed in IBM's T.J. Watson laboratories. The development of photoablative decomposition was applied to corneas with immediate implication for corneal refractive control. Scientific investigations demonstrated that submicron erosion ablation of material was possible without damage to remaining tissues. After refinement of the beam and analysis of thresholds, we subsequently demonstrated that healing of large ablated areas in rabbits and then primate eyes would occur without scar formation or loss of transparency. This prompted a number of commercial efforts to develop this device for both refractive and general corneal surgical applications. The early clinical investigations show that a predictable refractive change could be induced in a cornea and this change was stable over many months. Furthermore, the transparency of the cornea was unimpaired. These favorable early results have led to a number of clinical investigations of excimer laser corneal surgery including refractive keratectomy, a direct laser keratomileusis.

Animals↗
PubMed1988

Excimer laser keratectomy for correction of astigmatism.

We treated 13 eyes (12 patients) with excimer laser surgery for correction of astigmatism using linear corneal T-excisions. All eyes were followed up for a minimum of three months. We used a newly developed delivery system and special contact masks to deliver the 193-nm excimer light. Astigmatic corrections of up to 4.16 diopters were obtained. The actual corrections corresponded well with the intended values as predicted by a biomechanical theory. The refractive change over time was different than that observed after knife incisions, suggesting different repair mechanisms. An epithelial plug filling the whole T-excision persisted for over one year in all eyes.

Adult↗
PubMed1986

A comparative study of corneal incisions induced by diamond and steel knives and two ultraviolet radiations from an excimer laser.

This paper reviews the potential role of excimer lasers in corneal surgery. The morphology of incisions induced by two wavelengths of excimer laser radiation, 193 nm and 248 nm, are compared with the morphology of incisions produced by diamond and steel knives. Analysis suggests that ablation induced by excimer laser results from highly localised photochemical reactions and that 193 nm is the optimal wavelength for surgery. The only significant complication of laser surgery is loss of endothelial cells when incisions are within 40 micron of Descemet's membrane.

Animals↗
PubMed1985

An ultrastructural study of corneal incisions induced by an excimer laser at 193 nm.

Far ultraviolet light (193 nm) produced by an excimer laser has been used to produce a variety of incisions in the corneas of anaesthetised rabbits. Tissue was lost from the site of irradiation but the nature of the underlying molecular interactions responsible for such tissue erosion remain obscure. Ultrastructural analysis of the walls of the ablated areas show damage to the adjacent structures to be confined to a zone 60 to 200 nm in width. These dimensions could either be attributed to photochemical processes in which high energy photons directly break organic molecular bond, or to thermal reactions which result in limited heat flow and damage confined to the absorption depth at 193 nm of less than 1 micron. In non-penetrating incisions that reached within 40 micron of Descemet's membrane, endothelial cells were lost beneath the line of the irradiation. This spalling of cells seemed to be generated by shock or acoustic waves.

Animals↗
PubMed1984

Surgical management of malignant tumors of the lacrimal gland.

Malignant lacrimal gland tumors are rare but serious and life-threatening neoplasms. Patients frequently present with symptoms of less than 1 year duration, often demonstrating rapid change during the 6 months preceding diagnosis. Pain and periorbital sensory changes are also reported by patients. Radiographically, bone destruction is a strong indication of a lacrimal gland malignancy as is ophthalmoplegia. Radical three-dimensional resection utilizing a cranioorbital approach offers the best chance for total tumor removal. Immediate reconstruction with a scalp flap is essential for primary healing, as well as esthetic balance of the orbital region.

Adenocarcinoma↗
PubMed1984

Endothelial repair following Nd:YAG laser injury.

Effects of different energy levels (1.2, 2.0, 2.8, 4.0 mj) of a mode-locked Nd:YAG laser beam focused directly on the corneal endothelium were evaluated in rabbit, cat, and owl monkey. The endothelial lesion observed by specular microscopy at 10 min; 8, 16, and 24 hr; 3, 5, 7, and 21 days measured up to 0.8 mM in diameter. It showed focal destruction of Descemet's membrane and a larger area of endothelial denudation corresponding probably to the shock wave generated by the plasma. The size of the defect correlated with the amount of energy delivered. Even though healing was characterized by a phase of rapid endothelial migration during the first 24 hr, only about one-half of the defect was covered after 1 week in all animals. This lesion persisted with minimal endothelial proliferation for 3 weeks in the rabbit and for 3 months in the cat. The monkey was followed for only 1 week. Our findings indicate that the laser-tissue interaction is different from mechanical or thermal modes of injury and interferes with the specific endothelial functions in repair.

Animals↗
PubMed1983

YAG laser treatment of cystoid macular edema.

Fourteen eyes (some aphakic and some with implanted intraocular lenses) underwent neodymium-YAG laser treatment for cystoid macular edema with vitreous incarceration in the corneoscleral wound. Visual acuity improved in all 14 eyes; ten eyes improved at least three Snellen lines and 12 eyes improved at least two Snellen lines. After follow-up periods of one to nine months, 11 eyes had visual acuities of 20/40 or better (only two had had visual acuities of 20/40 preoperatively and none had had a better visual acuity). An additional eye, which had an intraocular lens implant, was treated prophylactically. Visual acuity in this eye remained stable during a nine-month follow-up period. YAG laser treatment produced no adverse side effects or complications in any of the 15 eyes.

Aged↗
PubMed1983

Plasma formation and shielding by three ophthalmic neodymium-YAG lasers.

Because microplasma formation may provide an energy-absorbing shield that protects the retina from inadvertent injury during neodymium-YAG laser surgery, we studied plasma formation and shielding by three ophthalmic neodymium-YAG lasers (the Q-switched American Medical Optics YAG-100, the mode-locked Meditec OPL-3, and the Q-switched LASAG Sirius Microruptor 2) with three model targets (physiologic saline, 1% sodium hyaluronate, and a cellophane membrane). Plasma formation produced a linear reduction in the transmission of light energy along the beam path in a qualitatively differences. Plasma shielding was similar in both saline and sodium hyaluronate; enhancement of the shield effect occurred only with the cellophane membrane target. Operating the lasers at energy levels far above threshold did not reduce total light transmission significantly. Clinical use should be guided by the principle of employing the minimum energy necessary to cut the target tissue.

Lasers↗
PubMed1979

Sino-orbital polyposis.

A 70-year-old woman with a long history of nasal and sinus polyps developed bilateral proptosis and left total external ophthalmoplegia. She was known to have hypercalcemia, which was later discovered to be caused by a parathyroid adenoma. X-ray studies, including computerized tomography, revealed increased radiodensity in the ethmoid sinuses (due to dystrophic calcification from the hypercalcemia), partial absence of the orbital walls from earlier surgical procedures, and bilateral rounded, retrobulbar tumors. At surgery, glistening, yellow, transparent, and encapsulated-lobulated masses were removed from the left orbit; they appeared to have prolapsed through a postsurgical dehiscence in the superomedial orbital wall. Light and electron microscopy confirmed that the lesional tissue represented polyps covered by respiratory epithelium; the yellow color was the consequence of secondary lipidization of the stromal fibroblasts.

Aged↗
PubMed1978

Immunofluorescent and immunoperoxidase characteristics of IgDlambda myeloma involving the orbit.

A biopsy specimen from a 59-year-old man with unilateral proptosis revealed an orbital plasmacytic tumor. In vitro immunoperoxidase and immunofluorescence studies and direct immunoperoxidase staining of Bouin's fixed, paraffin-embedded tissue sections demonstrated that the tumor consisted of plasma cells with surface and intracellular IgDlambda immunoglobulin. Systemic evaluation demonstrated multiple myeloma. A review of previously published reports combined with the case presented here suggests that IgD myeloma has a predilection for orbital involvement. Thus, while IgD myeloma accounts for only 2% of all myelomas, it may account for a significant percentage of myelomas with orbital involvement. The distinctive clinical course of IgD myeloma, particularly its poor prognosis, warrants consideration of the immunologic and serologic findings in patients with orbital involvement by myeloma. The application of immunofluorescence and immunoperoxidase techniques to the study of orbital lymphoreticular neoplasms should result in a clearer understanding of these neoplasms.

Diplopia↗