Biomedical subjects

J Roider

Publications and source records attributed to J Roider.

54 records · Page 3Linked to original sources

PubMed1998

Delayed intraocular lens dislocation after neodymium:YAG capsulotomy.

A poly(methyl methacrylate)(PMMA) intraocular lens (IOL) dislocated into the vitreous cavity in 2 patients after a neodymium:YAG (Nd:YAG) laser posterior capsulotomy. In Case 1, the capsulotomy was performed 19 months after extracapsular cataract extraction (ECCE) and sulcus fixation of an IOL. Six months later the IOL dislocated posteriorly. In Case 2, ECCE with intracapsular IOL implantation was followed 4 years later by an Nd:YAG capsulotomy; 6 months later the IOL dislocated into the vitreous cavity within the intact capsular bag. Different mechanisms were responsible for the dislocation: in case 1, radial tearing of the large capsular defect with IOL loosening and dislocation into the vitreous cavity; in Case 2, zonulysis and IOL dislocation within the intact capsular bag. A neodymium:YAG capsulotomy may cause delayed IOL dislocation into the vitreous cavity.

Aged↗

PubMed1998

[Subretinal neovascular membranes in membranoproliferative glomerulonephritis type II].

BACKGROUND: So called 'dense deposits' in the retina of a patient suffering from membranoproliferative glomerulonephritis type II (MPGN II) were first demonstrated in 1989. Appearence of subretinal neovascular membranes associated with MPGN II in three patients was described in 1990. PATIENT AND METHODS: We present a 45-year-old male patient, whose insufficiency of the kidney due to a membranoproliferative glomerulonephritis type II required peritoneal dialysis and later transplantation. In both eyes fundus examination revealed typical disseminated, partly confluencing, drusen-like 'dense deposits' and exsudative degeneration of the macula due to subretinal neovascular membranes. Visual acuity was less than 20/400 and visual fields were reduced to small excentrics islands. There was an atrophy of the optic nerve with nearly extinguished VEP in both eyes. CONCLUSION: Flecked changes of the retina called 'dense deposits' associated with membranoproliferative glomerulonephritis type II have to be differentiated in particular from drusen, as well as metabolic-toxic and degenerative retinopathy. Development of subretinal neovascular membranes is attributed to altered retinal pigment epithelium, similar to age-related macular degeneration. An atrophy of the optic nerve associated with this disease has not been described so far. It is possible that vascular damage because of hypertensive changes due to renal dysfunction is the reason for the optic nerve atrophy. With another hypothesis this could be caused by intraocular pressure due to a risen flow of water into the vitreous cavity following the altered osmotic gradient after peritoneal dialysis.

Cell Membrane↗

PubMed1998

Initial clinical experience with the picosecond Nd:YLF laser for intraocular therapeutic applications.

AIMS/BACKGROUND: Compared with nanosecond (ns) pulses of conventional Nd-YAG lasers, picosecond (ps) laser pulses allow intraocular surgery at considerably lower pulse energy. The authors report initial clinical experiences using a Nd:YLF ps laser for the treatment of various indications for photodisruption. METHODS: A Nd:YLF laser system (ISL 2001, wavelength 1053 nm) was used to apply pulse series of 100-400 microJ single pulse energy at a repetition rate of 0.12-1.0 kHz. Computer controlled patterns were used to perform iridectomies (n = 53), capsulotomies (n = 9), synechiolysis (n = 3), and pupilloplasties (n = 2). Other procedures were vitreoretinal strand incision (n = 2) and peripheral retinotomy (n = 1). For comparison, 10 capsulotomies and 20 iridotomies were performed with a Nd:YAG ns laser. The ps laser cut of an anterior capsule was assessed by scanning electron microscopy (SEM). RESULTS: Open, well defined iridectomies (mean total energy 4028 mJ, mean diameter 724 microns), were achieved at first attempt in 92% of the cases. In 64% an iris bleeding and in 21% an IOP increase of > 10 mm Hg occurred. All capsulotomies were performed successfully (mean energy 690 mJ/mm cutting length) but with a high incidence of intraocular lens damage. The attempted vitreoretinal applications remained unsuccessful as a result of optical aberrations of the eye and contact lens. Although ps laser capsulotomies and iridectomies required much higher total energy than ns procedures, the resulting tissue effects of the ps pulses were more clearly defined. SEM examination of a ps incision of the anterior lens capsule demonstrated, nevertheless, that the cut was more irregular than the edge of a continuous curvilinear capsulorhexis. CONCLUSION: Series of ps pulses applied in computer controlled patterns can be used effectively for laser surgery in the anterior segment and are considerably less disruptive than ns pulses. The ps laser is well suited for laser iridectomies while the ns laser is preferable for posterior capsulotomies. As vitreoretinal applications remained unsuccessful, the range of indications for intraocular photodisruption could not be extended by the ps laser.

Humans↗

PubMed1997

[Outcome after vitrectomy in rhegmatogenous retinal detachment and dense vitreous opacities].

BACKGROUND: In some cases of rhegmatogenous retinal detachment dense vitreous opacities can delay the diagnosis and prevent a scleral buckling procedure. In these cases a primary vitrectomy is necessary. These results of vitrectomy are of current interest, because intra- and postoperative complications are comparable to the group of patients with retinal detachment and clear media, in which primary vitrectomy is discussed today as an alternative method. PATIENTS AND METHODS: After redetachment and trauma were excluded, we reviewed the charts of 40 patients (40 eyes), who underwent vitrectomy and gas endotamponade for rhegmatogenous retinal detachment and dense vitreous opacities. In 31 cases vitreous hemorrhage and in 9 cases other dense non inflammatory vitreous opacities were present. Intraoperatively detected PVR (1), giant tear (1) and retinal holes located at the posterior pole (1) were excluded. The remaining 37 eyes were examined retrospectively. The median follow-up time was 12 months. RESULTS: In 32 of 37 eyes the retina was reattached after the first vitrectomy (86.5%). In 5 eyes a redetachment occurred, in 3 of them caused by PVR. After revitrectomy successful reattachment could be achieved in all cases. As intraoperative complications iatrogenic retinal break formation could be observed in 3 cases and lens-touch in 1 case. Postoperatively secondary tears in attached retina developed in 2 cases, in 1 case an arterial branch occlusion and in 1 case a Macular-Pucker. During the follow-up period a cataract developed in 12 of the 21 phacic patients. CONCLUSIONS: The reattachment rate of primary vitrectomy in eyes with retinal detachment and associated dense vitreous opacities is slightly lower compared to the rate of scleral buckling procedures in cases of retinal detachment with clear media. Comparable good or even better results may be expected for primary vitrectomy in cases of retinal detachment without vitreous opacities. Since the risk of intra- and postoperative complications in our group of patients is small it is promising also for primary vitrectomy in cases with good view on the fundus.

Adolescent↗

PubMed1997

Autosomal dominant vitreoretinochoroidopathy.

BACKGROUND: Autosomal dominant vitreoretinochoroidopathy recently has been described as a condition characterized by peripheral chorioretinal atrophy and areas of hypopigmentation and hyperpigmentation between the equator and the ora serrata circumferentially in the ocular fundus. We describe the clinical features of a family, some members of which have this disorder. This is the first such report of a family outside the United States. METHODS: We examined a family of 15 individuals, seven of whom were affected. RESULTS: The main clinical findings were peripheral pigmentary changes for 360 degrees, with a discrete boundary near the equator. In one patient, a partial vitreous detachment was found that was creating increasing traction to the macula and to the peripheral retina. Vitreous surgery successfully relieved the traction, and vision recovered from 20/100 to 20/25. One patient lost visual acuity at the age of 10 years when complete rhegmatogenous detachment occurred. In two women, a horizontal nystagmus was present showing typical signs of a congenital nystagmus. Results of electrooculography demonstrated a marked reduction of light rise and a clear reduced Arden ratio in one patient. CONCLUSIONS: Autosomal dominant vitreoretinochoroidopathy appears clinically as mainly a peripheral tapetoretinal disease; patients with this disease have been reported in and outside the United States. In addition to the typical peripheral features, significant vitreous traction maculopathy and congenital nystagmus associated with the disease were found.

Adult↗

PubMed1996

[Cyclophotocoagulation with the diode laser in contact procedure with a new focussing tip].

UNLABELLED: During contact cyclophotocoagulation (CPC) energy is transmitted through the conjunctiva and the sclera by direct contact of a plain fibre tip. Alteration and scarring of the conjunctiva and the outer parts of the sclera cannot always be avoided. We used a new fibre tip which defocuses the laser light on the conjunctiva and sclera and focuses the laser light on the ciliar body. The coupling and focusing medium between fibre and sclera is a small glass ball (3 mm diameter). METHODS: Up to now we have treated 52 human eyes of 35 patients affected by refractory glaucoma using a diode laser (Zeiss Visulas II) coupled with a 200-microns fibre and a 3-mm focusing ball tip. In all cases 20-40 spots were applied 1.5 mm posterior of the limbus, power varied between 1.5 and 2.2 W and exposure time was 1.5 s. RESULTS: In all cases the conjunctiva and the sclera was unaltered. The mean follow-up time was 224 days. The mean IOP values +/- SD before treatment and 6 days, 4 weeks and 1 year after treatment were 40.9 +/- 7.1, 19.3 +/- 7.9, 22.4 +/- 14.8 and 17.2 +/- 11.3 mmHg. No positive, linear correlation was found between number of spots and IOP drop after 6 days. There was considerable individual variance. The main complications were anterior fibrinous uveitis (10%), slight vitreous haemorrhage (2/52) and transitory hypotony (2/52). In one enucleated eye structural alterations to the pigmented and non-pigmented epithelial cells of the ciliary body were found histologically. CONCLUSIONS: Contact diode CPC can significantly reduce IOP, and the conjunctiva and sclera can be left totally unaltered by the focusing ball tip used in this study.

Aged↗

PubMed1995

[Laser coagulation of senile, moist macular degeneration].

Age-related macular degeneration (AMD) is a common disease in ophthalmology. The current status of knowledge in subretinal neovascularisations concerning epidemiology and treatment based on the findings of the macular photocoagulation study is shown. Most important parameters in treatment of subretinal neovascularisations in AMD are exact localization of the membrane in fluorescein angiography, its size and the visual acuity. The treatment of extra-foveal, well demarcated membranes can be recommended. Moreover recent results in the treatment of subfoveal, well demarcated membranes show some benefit for the patient as long as the size of the membrane is lower than 2 discs areas and the actual visual acuity is taken into account. Indocyanin-Green-(ICG)-angiography is recommended in occult subretinal membranes. Guidelines for the treatment are given.

Aged↗

PubMed1995

Laser sclerostomy ab externo using two different infrared lasers: a clinical comparison.

This study was designed to compare the clinical results of an ab externo approach to laser sclerostomy using two different laser sources under identical conditions. A pulsed (200 microseconds) erbium-YAG laser (lambda = 2940 nm) and a pulsed (200 microseconds) holmium:YAG laser (lambda = 2120 nm) were used. The energy of each laser was transmitted via a fiber (300 microns in diameter) and applied near the limbus, with the fiber tip remaining in steady contact with the sclera. According to the higher tissue absorption coefficient, a shorter penetration depth and, therefore, fewer complications were expected for the Er:YAG laser. A total of 26 patients with advanced open-angle glaucoma were treated and followed for up to 6 months. In all cases a functioning fistula with a prominent filtering bleb and a marked reduction in the intraocular pressure (from up to 35 mm Hg to < 10 mm Hg) could be achieved primarily. The total energy required was about 4 times lower for erbium:YAG laser was compared with holmium:YAG laser sclerostomies. No complication occurred intraoperatively. Postoperatively, reversible adherence of the iris to the internal ostium was more frequently observed in Ho:YAG laser sclerostomies (60%) and small hyphemas were more often seen in Er:YAG laser sclerostomies (30%). After 6 months of follow-up, about 40% of the fistula remained patent in both groups. In principle, both lasers are suited to serve as energy sources for the described approach. Under the conditions of the present study, different levels of thermal effects did not cause any significant difference in the clinical success rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1995

[Endotamponade with silicon oil in severe proliferative retinopathy with attached retina].

Silicone oil as endotamponade in cases with attached retina is only indicated in a few very selected cases. These are cases with a high risk of intravitreal hemorrhage and a need for quick visual rehabilitation. We examined 23 patients, who had undergone pars plana vitrectomy and silicone oil filling. All patients were diabetics with proliferative retinopathy and recurrent intravitreal hemorrhage. In 14 cases it was the only eye; 11 eyes previously had a vitrectomy. We analyzed these cases for visual acuity, rubeosis, bleeding tendency, reproliferations, cataract development and glaucoma. The follow-up time was 32 months. In 22 of 23 eyes quick visual rehabilitation was achieved, and the patients had at least ambulatory vision within the first week. In one case poor visual acuity was due to exudative maculopathy. No relevant bleeding occurred. In 14 of 16 phacic patients we observed a cataract. Seven patients developed glaucoma, which was due to neovascularization in 5 cases. It was successfully treated in all cases and no visual loss occurred. In 5 cases we observed a peripheral traction retinal detachment, in one case a traction retinal detachment at the posterior pole. In selected cases silicone oil can prevent recurrent intravitreal hemorrhage, allowing rapid visual recovery. Considering the complications, the silicone oil should be removed as soon as possible.

Diabetic Retinopathy↗

PubMed1994

Chromophore-assisted laser inactivation of proteins is mediated by the photogeneration of free radicals.

Chromophore-assisted laser inactivation (CALI) is a technique that selectively inactivates proteins of interest to elucidate their in vivo functions. This method has application to a wide array of biological questions and an understanding of its mechanism is required for its judicious application. We report here that CALI is not mediated by photoinduced thermal denaturation but by photogenerated free radicals. Thermal diffusion calculations suggest that the temperature changes resulting from CALI are too small to cause thermal denaturation, and Arrhenius plots of CALI are inconsistent with a photothermal mechanism. CALI shows an energy dose reciprocity above a threshold and can be inhibited by free-radical quenchers, thus demonstrating a photochemical mechanism of protein inactivation. The type of quenchers that are effective in inhibiting CALI indicates that the active species is a hydrogen abstractor which is not derived from molecular oxygen. We suggest that the active free-radical species is the hydroxyl radical and its very short lifetime explains the spatial specificity of CALI such that half-maximal damage is effected within 15 A from the dye moiety and no significant damage occurs at 34 A. The data are consistent with free-radical formation resulting from a sequential two-photon process.

Coloring Agents↗

PubMed1994

[Retinal photocoagulation with a pulsed, frequency-doubled Nd:YAG laser (532 nm)].

The small difference in wavelength between an argon laser (514 nm) and a frequency-doubled Nd:YAG laser (532 nm), together with the advantage of the solid-state technology, makes the Nd:YAG laser likely to play a major role in retinal photocoagulation in the near future. For technical reasons all frequency-doubled Nd:YAG lasers work in a quasi-continuous mode, emitting a burst of highly repetitive short laser pulses during the exposure time desired. We investigated the side effects due to high peak irradiances of those short laser pulse trains (Crystal Focus Nd:YAG laser, Emerald; pulse duration 1-10 microseconds, repetition rate 13 KHz) in rabbits in comparison with a standard argon laser system (Zeiss, Visulas, Argon II). The energy necessary for blanching the retina was similar in both cases. As opposed to the argon laser system, subretinal bubbles were regularly visible ophthalmoscopically with the Nd:YAG system, when average powers as high as 200 mW were used. The ED50 power for bubble formation is about 2-3 times above the ED50 power for blanching. Thermal calculations show that this bubble formation effect is likely to be related to the peak power of the short pulses. The hemorrhage threshold is similar in both systems. However, light microscopically there is no difference between the two laser systems. Panretinal photocoagulation (300-500 microns, 100-200 ms) in patients with proliferative diabetic retinopathy produced such bubbles about once per 1000 lesions.

Animals↗

PubMed1994

[Selective vascular occlusion by repetitive short laser pulse].

The occlusion of arterioles and venules (30 microns in diameter) by means of repeated dye laser pulses (577 nm, 160 microseconds, 0.5 Hz) was studied in the hamster cheek pouch model. Microscopically visible changes during and after irradiation were recorded and monitored by a video system. The energy necessary per pulse for vessel occlusion with a single pulse (arterioles 5 J/cm2, venules 3.5 J/cm2) can be lowered more than 50% with 100 pulses (1.8 J/cm2, 1.2 J/cm2). Rupture of vessels, which regularly occurs with a single pulse, can be totally avoided with 100 repetitive laser pulses. Investigations of the temperature dependence of the occlusion rate of arterioles showed different interaction mechanisms with one pulse and 100 pulses (mechanical and thermal respectively). Light and electron microscopic investigations supported this concept of selective occlusion using repeated short laser pulses. Possible clinical applications are portwine stains of the eyelid, neovascularisation on the cornea and subretinal neovascularisation.

Animals↗

PubMed1993

Microphotocoagulation: selective effects of repetitive short laser pulses.

Repetitive exposure to short laser pulses is shown to cause selective damage to absorbing structures (cells, organelles, or enzymes) with pulse energies below the threshold energy for single-pulse damage. Directly adjacent structures are spared in vivo. Additivity of (presumably nonphotochemical) subthreshold effects is demonstrated. Selective damage to the retinal pigment epithelium with sparing of the neural retina is shown (514 nm, 5 microseconds, 1-500 pulses at 500 Hz, 2- to 10-microJ pulse energy). A melanin granule model has been developed and applied to the experimental situation. Histological results as well as the basic mechanism for these effects are discussed.

Animals↗

PubMed1993

[Histology of retinal lesions after continuous irradiation and selective micro-coagulation of the retinal pigment epithelium].

Mild continuous wave (CW) irradiation (100 ms, 20 mW, 514 nm) and irradiation with 100 repetitive 5 microseconds laser pulses (3 or 6 microJ, 514 nm) at a repetition rate of 500 Hz was performed to the regio macularis of chinchilla rabbits. The angiographically visible lesions were histologically followed up to 4 weeks. With both irradiation modalities the original retinal pigment epithelium (RPE) was replaced by a monolayer of new RPE cells. Only minimal immediate and no subsequent damage to the photoreceptors was found after selective RPE photocoagulation. Only minimal inflammatory response was found after selective RPE photocoagulation in contrast to CW photocoagulation where macrophages, RPE cells and lymphocytes regularly appear in the damaged photoreceptor layer.

Animals↗

PubMed1993

[Spatial confinement of intraocular picoseconds-photodisruption effects].

Laser photodisruption is a routinely performed clinical procedure in intraocular microsurgery of post-cataract membranes, anterior synechies and iridectomies. Damage ranges of several millimeters in diameter, however, limit the use of nanosecond photodisruption close to delicate structures, e.g., in the posterior vitreous. Multiple ps-laser pulses of about 100 microJ pulse energy were used to produce disruptive effects in the anterior lens capsule in rabbit eyes in vivo. Ophthalmoscopical and morphological investigations of these effects were compared with those of minimal ns-disruptions. The direct tissue separation effects as well as the collateral damage zones are about one order of magnitude smaller if ps-laser pulses are used. Minimal sizes of disruptive effects are about 50 microns to 150 microns and 500 microns to 1000 microns for ps- and ns-pulses, respectively. The substantial improvement of spatial confinement of ps-photodisruption enables increased precision of intraocular laser microsurgery and opens up new areas of clinical application in structures like the cornea, anterior chamber angle, and crystalline lens.

Animals↗

PubMed1992

Response of the retinal pigment epithelium to selective photocoagulation.

Multiple short argon laser pulses can coagulate the retinal pigment epithelium selectively, while sparing the adjacent neural retina and choroid; in contrast, continuous-wave laser irradiation typically damages the neural retina and choroid. The healing response to selective photocoagulation of the retinal pigment epithelium was studied in rabbits during a period of 4 weeks. The lesions were never visible ophthalmoscopically. During the healing period, the epithelium was reformed by a single sheet of hypertrophic retinal pigment epithelial cells. In contrast to continuous-wave photocoagulation, only minimal inflammatory response was found. Retinal pigment epithelial cells showed clear signs of viability, eg, phagocytized outer segments. The local edema in the photoreceptor layer and subretinal space found in the early stage disappeared when the blood-retinal barrier was reestablished. The choriocapillaris remained unaffected. No subsequent damage to the photoreceptors was found. This type of photocoagulation may be useful for retinal pigment epithelium-related diseases, eg, diffuse diabetic macular edema.

Animals↗

PubMed1991

[Microcoagulation of the fundus. Experimental results of repeated laser pulse exposure].

Angiographically visible lesions were produced in the fundus of rabbit eyes with repetitive 5 microseconds pulses and continuous wave exposures with 50-ms to 1-s pulse duration from an modified argon laser (514 nm). The ophthalmoscopic and the fluorescein angiographic findings showed less damage in the neural retina and the choroid after repetitively pulsed irradiation. Light microscopy and transmission electron microscopy showed that the neural retina and the choroid can mostly be spared by using repetitive 5 microseconds pulses, even though the damage to the retinal pigment epithelium is similar to the damage caused by continuous wave irradiation. Possible clinical applications, e.g. for macular edema and central serous retinopathy, are discussed.

Animals↗

PubMedDate not supplied

Fundus autofluorescence in macular hole surgery.

BACKGROUND: Macular holes usually are diagnosed by biomicroscopy. Fluorescence angiography (FLA) is helpful especially for judging early stages or pseudoforamina. The importance of fundus-autofluorescence in macular hole surgery was studied. PATIENTS AND METHODS: Twenty-five consecutive patients with macular holes (n = 21) and clinically-similar appearances (n = 4) were examined biomicroscopically. In addition, fundus-autofluorescence and FLA were determined by Heidelberg-Retina-Angiograph (HRA, Heidelberg, Germany). A vitrectomy was performed on 16 patients with macular hole stage II, III, and IV, and membrane peeling was performed if necessary. Platelet-concentrate as an adjuvant agent was used in all surgeries, and all 16 patients were examined afterward. RESULTS: In all patients with macular hole stage III and IV (n = 18), fundus-autofluorescence revealed a marked hyperfluorescent spot in the foveolar region and also a hyperfluorescence in FLA. Patients with macular hole stage II (n = 3) showed a slight punctured hyperautofluorescence and a subtle window-defect in the FLA. Postoperatively, the autofluorescence was normal in all eyes with a closed macular hole (87.5%). In some patients, a variable punctured hyperautofluorescence was noticed (n = 3). In eyes with pseudoforamina, the autofluorescence was normal (n = 4). CONCLUSION: In macular hole diagnostics, fun-dus-autofluorescence is able to replace invasive fluorescence angiography. The autofluorescence is helpful for the examination of pseudoforamina and might be useful for estimating therapeutic success.

Aged↗