Biomedical subjects

K Hille

Publications and source records attributed to K Hille.

At least 19 recordsLinked to original sources

PubMed2006

[Development of visual acuity and refraction in deep lamellar and penetrating keratoplasty (KPL)].

BACKGROUND: Deep lamellar KPL can be considered as an alternative for penetrating KPL in pathologies of corneal stroma, because there is no risk of decompensation of the endothelium or corneal rejection. Nevertheless, it is well know in lamellar keratoplasty that scars may occur in the interface which can limit the final visual acuity. In a retrospective study we compared the postoperative development of visual acuity and refractive values in deep lamellar keratoplasty with a penetrating procedure. PATIENTS AND METHODS: 16 consecutive patients (mean age 48 years) with corneal stroma pathologies such as corneal ulcer, alkali burn and keratoconus underwent deep lamellar KPL. The control group consisted of 38 patients (mean age 42 years) with keratoconus who received a penetrating keratoplasty. Visual acuity and subjective spherical and cylindrical values of the refraction were evaluated preoperatively and after 6 weeks, 6 months and 1 year. RESULTS: The mean postoperative visual acuity (VA), spherical (SV) and cylindrical (CV) values of the deep lamellar group (results of the control group in brackets) were at 6 weeks VA = 0.24 +/- 0.24 (0.37 +/- 0.23), SV = 0.325 +/- 5.3 dpt, CV = - 1.66 +/- 0.67 dpt (- 3.08 +/- 1.93 dpt), after 6 months VA = 0.38 +/- 0.28 (0.53 +/- 0.31), SV = - 3.0 +/- 4.42 dpt (0.33 +/- 1.93 dpt), CV = - 2.57 +/- 2.03 dpt (- 2.35 +/- 1.32 dpt) and after 1 year VA = 0.41 +/- 0.27 (0.57 +/- 0.26), SV = - 2.57 +/- 4.62 dpt (0.17 +/- 3.98 dpt), CV = - 2.75 +/- 1.25 dpt (- 0.34 +/- 1.86 dpt). There was no significant difference in all the parameters between the two groups. CONCLUSIONS: As the good functional results of deep lamellar KPL are comparable to those of penetration KPL and the risk of endothelial decompensation or rejection is lower in a lamellar procedure, we suggest the use of a deep lamellar KPL in patients with an intact endothelium.

Adult↗

PubMed2005

Medium term results in keratoprostheses with biocompatible and biological haptic.

PURPOSE: Corneal grafts or limbal stem cell transplantation are often unsuccessful in patients with severe ocular surface disorders such as severe dry eye syndrome, symblepharon or diffuse vascularisation. In those patients, a keratoprosthesis (KPro) may be an alternative for the recovery of vision. Various KPro differ from each other in the material of the haptic that supports the optic cylinder. The haptic may be made of biocompatible or biological material such as tibia bone (TKPro) or dentine and alveolar bone (osteo-odonto-keratoprosthesis, OOKP). On the basis of our experience, we wanted to comment on the value of different KPro. METHODS: Over the last 10 years we have implanted a total of 35 KPro, 29 with biological haptic (25 OOKP and four TKPro), and six KPro with biocompatible haptic (one Legais KPro, five Pintucci KPro). A follow up examination was carried out approximately every6 months. RESULTS: The patients gained a visual acuity of > or =0.9 in 20.6%, of > or =0.5 in 52.9%, of > or =0.2 in 61.8% and a significant improvement in visual acuity in 76.5%, respectively. There was no significant difference between the various types of KPro concerning the best postoperative visual acuity. All patients showing poor improvement had a pre-existing end stage secondary glaucoma or other retinal damage. The median follow-up was 2.9 years (maximum 8) for OOKP, 1 year for TKPro, 1 year (maximum 2) for Pintucci Kpro and 6 month for Legeais KPro. During this period, only one of the KPro with biological haptic was lost (one TKPro after 1 year), compared with four out of six of the KPro with biocompatible haptic (P<0.0001). CONCLUSIONS: Fixation of the KPro by a root of the patient s own tooth (OOKP) leads to the best results in the long-term follow up, as our results as well as the literature demonstrate. As long as a KPro is in place, the visual acuity is as good as the retinal function. For the ranking of different types of KPro, the percentage and the duration of the anatomic success are most important. The comparability of the various KPro results may be limited, since the patients were not randomised and the four groups differ in number.

Adult↗

PubMed2005

[The Ahmed glaucoma valve. Medium term results].

BACKGROUND: In complicated glaucoma, when classical filtrating surgery would be ineffective, aqueous shunts may be used. Complications due to hypotonia are reduced by valved systems, such as the Ahmed glaucoma valve (AGV). METHOD: In a retrospective case control study, 28 patients with complicated glaucoma were included. In addition to the clinical examination, we examined the size and function of the filtering area using ultrasound. RESULTS: The medium term follow-up was 25+/-16 months, the preoperative intraocular pressure (IOP) 35.5 mmHg+/-10.3 while 17 eyes were pseudophakic and nine aphakic. In the first weeks after AGV implantation, the mean IOP was 6.3+/-2.5 mmHg. In nine eyes, the pressure was less than 5 mmHg and five developed a temporary choroidal detachment. At the last visit, IOP was regulated in 22 eyes (82.1%). There was no correlation between IOP regulation and the size of the filtering bleb or the increase in the latter by digital pressure. CONCLUSION: In the management of complicated glaucoma, if there is a high risk of failure due to conjunctival scarring, AGV implantation can be used as a save procedure with a success rate comparable to other glaucoma implants.

Adolescent↗

PubMed2004

Drainage devices in glaucoma surgery.

Glaucoma drainage devices, also termed aqueous shunts (AS), are widely used in the USA. Indications for AS include excessive conjunctival scarring diminishing the success of another filtration surgeries, abnormalities of the iridocorneal angle, neovascular glaucoma, presence of corneal grafts, and inflammatory glaucoma. Qualified success has been achieved for many years in 50 to 100 % of the treated eyes, depending on the patient selection. An AS consists of a silicone tube that is inserted into the anterior chamber and a plate (explant) made of silicone or polypropylene. The latter is positioned between the recti muscles. Within some weeks the surrounding tissue forms a fibrous bleb around the plate. This serves as a permanent filtration reservoir. The most serious complication is postoperative hypotonia, that can lead to serious choroidal detachment, suprachoroidal hemorrhage, anterior chamber flattening, and corneal decompensation. To avoid this complication some devices, e.g. the Ahmed Glaucoma valve and the Krupin valve, have integrated mechanisms to sustain a residual intraocular pressure. With other devices such as the Molteno and the Baerveldt devices the tube has to be temporarily ligated until a scar area forms around the explant. On the other hand, fibrous infiltration of the wall of the bleb often leads to a reversible rise in intraocular pressure about one to four months after surgery which can be treated by massaging the bulb, needling the bleb, or injection of antimetabolites. There are no obvious differences between the different AS regarding the success of pressure control. With appreciation of indications and therapy of complications, AS are an useful option in the management of complicated glaucoma, where conventional filtration surgery is considered to carry a high risk of failure.

Equipment Design↗

PubMed2002

[Keratoprostheses. Historical overview, materials and status of current research].

The idea to substitute optically clear material in an opaque cornea is two centuries old and in that time experiments have been carried out in animals and patients without much success. The historical development of and the clinical experiences with keratoprostheses are described. Especially in the last 40 years there have been great efforts concerning design, fixation, material and surgical technique to create a device with long-term success. The best long-term survival rates are achieved with the osteo-odontokeratoprosthesis, as it is the only model with a biological haptic. Due to some disadvantages of this procedure the present research is looking for new, soft materials and surface modifications to create a biointegrable artificial cornea.

Animals↗

PubMed2002

[Keratoprostheses. Clinical aspects].

In patients with dry eye, like pemphigoid, Fuchs-Stevens-Johnson syndrome and xerophthalmia, in eyes with severe vascularisation of the cornea due to severe burns, in a leucoma adherens or following recurrent transplant rejections as well as in cloudy corneas of silicone-filled eyes, restoration of visual acuity can often only be achieved by a keratoprosthesis. In the case of an intact posterior segment and retinal function a normal visual acuity can be anticipated but mostly with a restricted visual field. Complications vary from glaucoma, retroprosthetic membranes, necrosis of the recipient tissue at the rim of the prosthesis, endophthalmitis, loosening and loss of the prosthesis even to the loss of visual acuity. With some types of prostheses the visual acuity will be reduced again within a short time, but in osteo-odonto-keratoprostheses, using the root of a patients tooth as haptic material for the optical cylinder, good long-term results even for several decades are possible. In patients without suitable teeth, prostheses with biointegrable materials such as Pintucci keratoprostheses can be used. A basic rule is that a secondary glaucoma, which in this patient group frequently develops even preoperatively, must be treated adequately.

Corneal Opacity↗

PubMed2002

[Drainage systems in glaucoma surgery].

Glaucoma drainage devices, also known as aqueous shunts (AS) are widely used in the USA. They consist of a silicone tube that is inserted into the anterior chamber and connected to a plate made of silicone or polypropylene, the explant. The latter is positioned between the recti muscles and over several weeks the surrounding tissue forms a fibrous bleb around the plate. This serves as a permanent filtration reservoir.Recurrent failure of filtrating surgery is the main indication for the use of AS. Other indications include situations in which the formation of a filtering bleb seems to be unpromising because of extensive conjunctival scarring. Qualified success has been achieved for many years in 50-100% of the eyes treated depending on patient selection. The most serious complication is postoperative hypotonia that can lead to serious chorioidal detachment, suprachorioidal hemorrhage, flat anterior chamber and corneal decompensation. To avoid this complication some devices, i.e.the Ahmed Glaucoma and the Krupin valve have integrated mechanisms to sustain a residual intraocular pressure. With other devices i.e. the Molteno and the Baerveldt devices, the tube has to be temporarily ligated until bleb formation has started. On the other hand fibrous infiltration of the bleb 1-4 months after the surgery often leads to a reversible rise in introcular pressure, which can be treated by massaging the bulbus, needling the bleb or injection of antimetabolites. There are no obvious differences between the various forms of AS with regard to the success of pressure regulation. In summary,by close scrutiny of indications and management of complications,drainage systems are a useful option in the management of complicated glaucoma that carry a high risk of failure from conventional filtering surgery.

Equipment Design↗

PubMed2002

[Osteo-odonto-keratoprosthesis. A summary of 6 years surgical experience].

PURPOSE: In patients with severe corneal scarring and vascularisation, corneal grafts have a high risk of failure. In those patients an osteo-odonto-keratoprosthesis (OOKP) can be performed. METHOD: We performed OOKP in eight patients in all with ocular pemphigoid, severe alkali burns, or repulsion of a corneal graft. Each of the patients had finger-counting visual acuity or less. The OOKP consisted of a PMMA cylinder 8 mm long, with a diameter of 3-4 mm, and from a root of the patient's tooth. This was implanted in the cornea and covered with buccal mucosa. RESULTS: The medium follow-up was 3 years. The implants are now well incorporated. The best visual acuity was between 0.6 and 0.9 in four patients with intact retinas. In the remaining patients, visual acuity was dependent on the posterior segment findings. The visual field was centred. Five of the eight patients had vitreous bleeding after the operation that was spontaneously absorbed. Revision of the mucous coverage was necessary in four patients, and one of them had a severe inflammation with partial absorption of the bone and tooth implant. One patient developed a secondary angle-closure glaucoma and was treated successfully by implantation of an Ahmed valve. Two patients developed membranes behind the cylinder that were successfully removed. There was no loss of any prosthesis during follow-up. CONCLUSIONS: In impasse in severe corneal scars, the osteo-odonto-keratoprosthesis is still indicated and shows good results in visual rehabilitation of patients.

Adult↗

PubMed2002

[The effectiveness of limbus epithelium transplantation].

BACKGROUND: The transplantation of the limbus is based on the theory that limbal stem cells are necessary for epithelialisation and maintenance of a clear cornea. We used a genetic analysis procedure to demonstrate the survival of transplanted limbus stem cells. PATIENT AND METHODS: A lamellary corneal graft and limbus transplantation from donor material was carried out on a patient with severe alkali burns and destroyed Bowmann's membrane to prepare the cornea for perforating keratoplasty. Subsequently, perforating corneal graft was carried out and the epithelium and endothelium of the removed cornea were analysed with a gene analytical procedure. For the cellular typing we used the SGM kit, well known in forensic analysis, that allows simultaneous detection of alleles at 11 loci. The genetic analysis was performed using an ABI PRISM 310 Genetic Analyser (Perkin Elmer Applied Biosystems) after DNA amplification by the polymerase chain reaction. RESULTS: The cornea-limbus transplant was integrated without vascularisation from the limbus under treatment with cyclosporin A. The epithelium cells of the corneal tissue gained by keratoplasty had the same genetic pattern as the primary donor in all loci, but no congruence with the recipient (except for the amelogenin marker because both the donor and the recipient were males). Therefore the epithelium cells must have originated from the transplanted stem cells of the donor. CONCLUSIONS: The identical genetic pattern found for the donor and the epithelium of the corneal-limbal transplant demonstrate the survival of the transplanted stem cells in a patient with adequate cytostatic therapy.

Adult↗

PubMed2001

[Laser flare in combined cataract and glaucoma surgery].

BACKGROUND: We used a laser-flare meter to compare inflammation of the anterior chamber in combined cataract and glaucoma surgery with that in pure filtering surgery. MATERIALS AND METHODS: In 34 consecutive patients with primary chronic open-angle glaucoma (PCOG) we combined glaucoma surgery and cataract extraction with phacoemulsification and implantation of a foldable intraocular lens via the same incision. We compared the results with those in 32 PCOG patients receiving a single goniotrephination and in 45 PCOG patients receiving cataract extraction via clear cornea with implantation of a foldable lens. RESULTS: The increase in the flare in the first 2 days was significant in those receiving combined cataract and glaucoma surgery and in those receiving single goniotrephination but not in those receiving a single cataract extraction. After 3 weeks there was no significant difference to the preoperative value in any of the groups. The highest flare values were in patients after combined surgery, significantly higher than after cataract extraction in the first days and higher than in the goniotrephination patients 3 weeks after the operation. CONCLUSION: The highest flare on the first day was in combined cataract and glaucoma surgery. This may explain the more frequent scarring of the filtering bleb in combined surgery. Postoperatively the intraocular pressure and number of drugs used for glaucoma did not differ in patients with combined and single goniotrephination.

Aged↗

PubMed2001

[Technical construction, calibration and results with a new intraocular pressure sensor with telemetric transmission].

BACKGROUND: Presently intraocular pressure is measured indirectly by applanation or impression of the cornea. Only isolated values are available with this method. We present a new implantable system for direct and continuos measurement of the intraocular pressure. METHODS: An implantable system consisting of a miniaturized sensor and a telemetric unit was integrated in an intraocular lens. The eye pressure is determined by the sensor, modulated and transduced by the telemetric system. By an extracorporal receiver the signal is demodulated. The electric supply of the intraocular system is achieved by external electromagnetic induction. RESULTS: The telemetric transmission of the intraocular pressure can be achieved with an accuracy of +/- 1 mm Hg and a frequency of registration of 3 values per second. CONCLUSION: Clinical application necessitates further animal trials in vivo.

Calibration↗

PubMed2001

Synthesizing emotional behavior in a simple animated character.

A simple computer-generated agent was developed of which four behavioral aspects could be altered. Emotional behavior was defined and simulated in terms of these aspects. Participants matched a list of six emotions to the animated emotional behavior of the agent. Results suggest that it is possible to identify emotions from a set of simulated modulation patterns. The successful simulation of a computer-generated "emotional" agent supports a behavioral theory of emotion. In addition, it reveals an almost overlooked aspect of emotion that may spark further research and shows the fertility of the approach known as "artificial life" for the field of psychology.

Behavior↗

PubMed2000

Three-dimensional analysis of measurements of the Heidelberg Retina Tomograph.

BACKGROUND: With the aid of scanning laser tomography, feasible with the Heidelberg Retina Tomograph (HRT), refined structures can be measured three-dimensionally. Pictures are built up from scanned layers which are represented as two-dimensional topographical or reflectivity pictures by the HRT software. The kind of information that is provided by the third dimension can be exploited much better by real spatial three-dimensional presentation. The autostereoscopic Dresden 3D display makes such a spatial presentation feasible as add-on to the HRT. METHODS: Seventeen patients (9 women, 8 men) were chosen on the basis of a long duration of observation (mean 42.41 months) and a large number of follow-up examinations (mean 5.29). These patients were examined with the HRT as well as with the Dresden 3D display. The results were compared regarding their correlation pairs. RESULTS: Comparing the correlation pairs (r>0.7) the Dresden 3D display provided a higher Pearson correlation coefficient with 8 out of 10 pairs. It was evident that the evaluations of the two devices referred to the same parallel structures. DISCUSSION: The Dresden 3D display facilitates, with its form of presentation, a better evaluation of the measurements of the HRT. More precise evaluation of retinal structures by virtue of the autostereoscopic display presents an improvement.

Feasibility Studies↗

PubMed2000

[Ocular injuries and triage after the bombing attack on the United States embassy in Nairobi (Kenya)].

BACKGROUND: As a result of the terrorist bombings of the United States Embassies in Daressalam (Tansania) and Nairobi (Kenya) on August 7, 1998, over 200 people were killed. 5000 persons were injured severely. The purpose of this article is to provide a review of our experiences in the evaluation and treatment of patients with multiple simultaneous ocular injuries sustained in the Nairobi attack. PATIENTS AND METHODS: We treated eight survivors of the assault, four of them with extremely severe eye injuries. A three-tiered system of triage developed. The first level occurred on scene, in which minor injuries were treated locally and more severe injuries were transported by aeromedical evacuation to Landstuhl Regional Medical Center (LMRC), in Germany among other locations. Surgical exploration of all patients arriving at LRMC was performed and surgical repair was undertaken when appropriate and technically possible. Patients requiring vitreoretinal surgery were transferred either to Saarland University Eye Hospital, Homburg, Germany, or Walter Reed Army Medical Center, Washington, DC. RESULTS: Only one eye required enucleation, due to an almost complete extrusion of the retina. It was possible to stabilize even severely injured eyes with multiple intraocular foreign bodies. CONCLUSIONS: Modern microsurgical techniques such as temporary keratoprothesis, perforating keratoplasty, and pars plana vitrectomy can now save eyes and often allow restoration of usuable visual acuity where this once have been deemed impossible.

Adult↗

PubMed1999

[Ultrasound localization of haptics of sclera attached posterior chamber lenses. Comparison of 2 high resolution ultrasound instruments].

BACKGROUND: The ciliary sulcus as the intended location of transsclerally fixated posterior chamber lenses (PCL) is withdrawn from the surgeon's view. Using high-resolution ultrasound, we acquire pictures that postoperatively allows us to determine the position of the haptics. METHODS: After transscleral fixation of PCLs in nine patients, we localized the haptics (central part and distal part of the haptic) by high-resolution ultrasound using the Ultrasound Biomicroscope 840 (Humphrey, 50 MHz) and the 13-System-ABD (M & C, 20 MHz). RESULTS: In most cases the central part of the haptic was located in the ciliary sulcus (UBM 840: 11/18; 13-System-ABD: 13/18). The peripheral part of the haptic could not be located in the ciliary sulcus in most cases (UMB 840: 5/18, 13-System-ABD: 6/18). In 6/36 cases the results of evaluation of the positioning of the haptic were different in both ultrasound examination systems. CONCLUSIONS: Both kinds of instruments lead to a sufficiently exact location of the haptics in all cases. Due to the higher resolution of the UBM 840 the structures of the ciliary body can be better demonstrated. The disadvantage, however, is that the instrument is more difficult to handle than the 13-System-ABD.

Humans↗

PubMed1999

[The Ahmed glaucoma valve - a new implant for high intraocular pressure].

UNLABELLED: In incurable glaucoma the implantation of traditional drainage systems (such as the Molteno implant) usually leads to extreme hypotension in the eye in the first postoperative period. The Ahmed Glaucoma Valve presents an alternative method to avoid this problem. PATIENTS AND METHOD: Ten patients with incurable glaucoma received an Ahmed Glaucoma Valve. The average age was 59 years (22-81) and the follow-up period was an average of 8 months (4-20). RESULTS: In the early postoperative period the average IOP was 5.5 mm Hg (range 4-8.5). We saw chorioidal detachments in two patients but no shallow anterior chamber. In six patients the pressure rose over 22 mm Hg, but we induced filtration by massaging the eye or rinsing the system in three and two patients, respectively. In nine of the ten patients, tension was definitively regulated, in one with an additional topical medication against glaucoma. CONCLUSIONS: Unlike the classic glaucoma drainage systems, the Ahmed Glaucoma Valve reduces intraocular pressure in the first postoperative period without the problems of excessive hypotension.

Adult↗

PubMed1999

Improvement of the osteo-odonto-keratoprosthesis according to Strampelli: influence of diameter of PMMA cylinder on visual field.

BACKGROUND: In surgical management of severe corneal scarring, the osteo-odonto-keratoprosthesis (OOKP) according to Strampelli is recognised as the best choice. Nevertheless, the patients are handicapped by a restricted visual field. Enlarging the optical cylinder diameter should allow better rehabilitation of the patients. PATIENTS AND METHODS: A mathematical model to calculate the theoretical maximum visual field according to the length and the diameter of the cylinder of a keratoprosthesis was developed. The theoretical values were compared with our findings in three OOKP patients operated on in our hospital. RESULTS: The theoretical extent of the visual field with a cylinder of 8 mm length is 55 deg if the diameter is 3 mm and 62 deg if the diameter is 3.5 mm. The visual fields of our OOKP patients in both types of keratoprosthesis are, however, below the theoretically calculated values. Implantation of a prosthesis with a diameter of 3 mm produced horizontal visual fields of 30 and 36 deg in two patients. In one patient with a prosthesis diameter of 3.5 mm the field was 53 deg. CONCLUSIONS: The diameter of the visual field increases with the diameter and decreases with increasing length of the optical cylinder. In OOKP the implantation of a PMMA cylinder with a diameter of 3.5 mm is possible. The enlargement of the diameter of the optical cylinder leads to significant enlargement of the visual field. The size of the cylinder is limited by the diameter of the available root of the tooth.

Biocompatible Materials↗

PubMed1999

[Initial clinical experiences with the Dresden 3D display in conjunction with the Heidelberg Retina Tomograph (HRT)].

BACKGROUND: For years the Heidelberg Retina Tomograph has been an established method to diagnose early glaucomatous damages at the optic nerve head. The major difficulty consists in defining the outlayer of the optic nerve head in a 2-dimensional reflective or topographic picture. A 3-dimensional presentation of the ocular fundus could ease the defining very much. The Dresden 3D-display tested provides a true 3-dimensional presentation of the HRT-values measured. METHODS: For the study 5 groups of prediagnosed follow-up examinations were formed, which in their course showed various progression. The examination firstly was carried out by manual defining of the papilla contour on the Dresden 3D-display and secondly by the new automatic contour-finding of the 3D-software. RESULTS: Through the 3-dimensional presentation a more correct position of the contour can be found when drawn manually. As a result some diagnoses of the 2-dimensional HRT-pictures had to be revised. The results proved considerable differences between the automatic outlayer-finding and the probably real position of the papilla borders. CONCLUSION: The 3-dimensional presentation of the HRT-pictures represents an subjective improvement regarding the accuracy of manual contour definition. In particular, the fact that it is feasible to make the pictures rotate around the axes offers completely new insights to the morphology of the disc.

Computer Systems↗