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Biomedical subjects

K Hanna

Publications and source records attributed to K Hanna.

At least 19 recordsLinked to original sources
PubMed1992

[Use of perfluorocarbon solutions in the surgical treatment of posterior luxation of the lens].

Posterior lens dislocations represent 20 to 40% of all lens dislocations. It can occur after trauma. Visual prognosis can be good, but most often there are complications such as glaucoma, retinal detachment and uveitis. A few years ago, surgery was difficult, and surgery was delayed until the development of specific complications. A new technique, using perfluorocarbon liquids (PFCL), should be recommended because it is simple, and constantly effective. After vitrectomy, perfluorodecalin is injected into the vitreous cavity. As PFCL have a density twice the density of water, it allows the lens to float on the surface of the PFCL, behind the iris. Lens extraction can be associated with trabeculectomy, and anterior chamber lens implantation. We present a prospective study of 6 cases operated according to this technique. Postoperative results were good: visual acuity was preserved and ocular tension was controlled in cases of preoperative hypertonia. We believe this technique can be recommended after posterior lens dislocation, to prevent complications and to preserve visual acuity.

Aged↗
PubMed1990

Healing of excimer laser ablated monkey corneas. An immunohistochemical evaluation.

The healing response of the cornea following excimer laser anterior keratomileusis (a 4-mm-diameter ablation to a depth of 11, 23, or 46 microns) was analyzed immunohistochemically in adult rhesus monkeys. The ablated surface had reepithelialized and the synthesis of type VII collagen (a major component of anchoring fibrils) was evident by 7 days; the reestablishment of a nearly continuous anchoring fibril zone was evident after 12 weeks. Stromal fibroblasts, activated in response to wounding, expressed a fetal antigen for approximately 6 weeks. Although fibronectin and type VII collagen were present only transiently in the regenerating subepithelial stromal matrix in the subepithelial regions, some other alterations, including the presence of type III collagen, increased levels of keratan sulfates, and discontinuities in the anchoring fibril zone were evident even 18 months after wounding. The depths of the regenerated stroma, which were estimated from the depths of remnant staining for type VII collagen in the stromal matrix, generally, but not always, corresponded to the depths of the calculated ablation.

Animals↗
PubMed1990

Music during learning of a tactual-spatial task affects later response generalization.

Equal numbers of men and women learned a finger maze, with half of the subjects initially using their right hands and the other half using their left hands. To reach criterion, subjects receiving music in the ear ipsilateral to the hand used required more trials than did those receiving no music. Furthermore, when the right hand ran the maze, music played to the ipsilateral ear also delayed learning, compared with music played contralaterally. Binaural music delayed learning when the left hand was used but not when the right hand was used. Possible causes of these effects are suggested. When subjects switched hands and relearned the maze, the number of trials to criterion depended on the group subjects were in during initial learning and not on the group they were in during the hand reversal (response generalization) trials. Although the music condition used determined the effect of music on initial learning and on response generalization, some evidence is presented that indicates that the two effects are not entirely interdependent and that they may even involve different mechanisms.

Adult↗
PubMed1990

[Is there a future for the Excimer laser in refractive surgery?].

The refractive surgery concerns all the surgical procedures implicated in the refractive power change of the cornea. Its clinical results are just known, and a new physical procedure is becoming capable to replace surgery: the Excimer laser. Without any instrumental contact with the corneal surface, the laser beam is able to remodel the corneal tissue, and to treat astigmatism, myopia, hypermetropia. Millions of people could be treated by such a laser, and could leave their glasses. Biological effects on rabbit and monkeys are presented. An argon fluoride excimer laser (193 nm) with a moving slit delivery system was used to perform anterior myopic keratomileusis in both eyes of 37 rabbits and 15 monkeys. Histological analysis of the corneas was made after ablation and at intervals up to 20 months. By slit examination at the longer follow up time, 60% of treated rabbits and 40% of treated monkeys keep a clear cornea, but the others had central spotty subepithelial haze. Light and electron microscopy documented corneal healing. In the clear corneas a good reconstitution of the epithelium, its basal lamina was observed, and anterior stromal corneas contained few active fibrocytes with a good preservation of the connective lamellar structure. On the contrary, in the cornea with opacification focal areas of 20 microns thick subepithelial scarring were present and the interface between epithelial cells and anterior stroma remained disturbed by incomplete, disrupted or duplicated basal lamina. Differences between the responses of monkeys, rabbits corneas to the same photoablation procedure remain unclear.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Potential use of lasers for penetrating keratoplasty.

Experimental corneal trephination has been achieved with the 193 nm argon fluoride excimer and 2.9 microns hydrogen fluoride and Er:YAG laser systems. Compared with metal blades and other lasers, the 193 nm excimer laser creates the best quality corneal excision, but has a relatively slow etch rate through the stroma, and its use requires toxic gas. The mid-infrared laser systems trephine the cornea in less than 10 seconds, but cause a 10 microns to 15 microns zone of adjacent stromal damage and create wounds that are approximately 2.5 times larger than wounds made by metal scalpels. The wavelength and laser pulse duration influence the cutting characteristics of the laser. Optical delivery systems using an axicon lens, a rotating slit, and a computer controlled scanning optical system have been developed for penetrating keratoplasty. Selection of the optimal laser system for penetrating keratoplasty must await further experimental studies. Refinements of the laser cavity and delivery system are necessary before clinical studies can begin. A carefully controlled randomized clinical trial comparing laser trephination with conventional mechanical trephines will be necessary to determine the safety and efficacy of a laser trephination system.

Cornea↗
PubMed1988

Excimer laser trephination in penetrating keratoplasty. Morphologic features and wound healing.

The imprecision of trephination of donor and recipient corneas is a major factor in post-keratoplasty astigmatism. In order to improve the quality of trephination, the authors developed a rotating slit delivery system for noncontact penetrating keratoplasty trephination using the excimer laser at 193 nm. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and light microscopy (LM) demonstrated the superior quality of excimer-cut buttons and recipient beds as compared with those obtained by free hand and suction trephines in human cadaver and rabbit eyes. The laser trephined more regularly and precisely without distortion of corneal topography and with less damage to adjacent corneal tissue. The authors morphologically examined wound healing at 6 hours, 12 hours, 3 days, 5 days, 2 weeks, 2 months, and 3 months after penetrating keratoplasty with laser and mechanical trephination in an animal autograft model. The laser did not cause any adverse alteration of wound healing processes including cellular migration, proliferation, and production of new tissue.

Animals↗
PubMed1988

[Lamellar keratoplasty with the Barraquer microkeratome. Preliminary clinical study apropos of 7 cases].

The authors report the results of a preliminary clinical study about lamellar keratoplasty performed with the Barraquer microkeratome. Seven eyes were operated on by this technique, with good functional and anatomical results. Nevertheless, some problems remain. An accurate diameter of the resected button, concerning both the donor and recipient corneas cannot be exactly predicted. There may also exist some irregularities at the edges of the resection. For these reasons, a good incorporation of the donor cornea into the recipient bed may be difficult. These are the main problems with this technique, which facilitates an improved visual prognosis of lamellar keratoplasty.

Adolescent↗
PubMed1988

[Results of myopic keratomileusis. A retrospective clinical study apropos of 40 cases].

The authors report in a retrospective study, the results of myopic keratomileusis. 40 eyes were operated on at the department of ophthalmology of Hotel-Dieu Hospital in Paris, with a range follow-up of 6 to 24 months. The mean pre-operative spherical equivalent was - 15.08 +/- 3.32 D., and the mean post-operative spherical equivalent was - 5.02 +/- 3.75 D. relative to preoperative conditions, best corrected visual acuity were unchanged in 6 cases, improved in 16 cases and diminished in 18 cases. The predictability of results was better for patients with myopia in the range of - 9 to - 16 D. During the first post-operative year, a mean regressive tendency of 3 diopters was noted. Complications are reported and analysed. Myopic keratomileusis is indicated for myopia between - 10 and - 16 D., when correction by contact lenses has failed. Candidates for surgery must be informed and consent about possibilities, limits and risks of the procedure.

Cornea↗
PubMed1988

Phencyclidine-induced psychosis: eight-year follow-up of ten cases.

In 1978, we identified ten patients who were hospitalized for phencyclidine-induced psychosis. Over the next eight years, we used their medical records to document their subsequent hospitalizations and psychosocial functioning. The overall outcome for this group of patients was poor, with chronic unemployment, continuing use of illicit drugs, dependence on relatives for shelter and financial support, and repeated hospitalizations being the rule.

Adolescent↗
PubMed1987

Financing of child psychiatry pediatric consultation-liaison programs.

Child psychiatrists and pediatricians recognize the importance of providing psychosocial care for children and their families in medical settings. Consultation-liaison and behavioral pediatric programs provide most of the training in this area. Twenty-nine pediatric consultation-liaison program directors participated in an initial and follow-up telephone survey about their programs. In the 5 years between the surveys, there was a drastic reduction in federal funding for these programs. The findings include a change in the number and composition of both staff and trainees. There were major shifts in the financial support of the programs. The programs were involved in fewer activities and in more restricted settings at the time of the follow-up survey. Financing of pediatric consultation-liaison programs plays a major role in shaping the structure and function of the programs.

Child↗
PubMed1987

Excimer laser experimental keratectomy. Ultrastructural study.

Excimer lasers have been shown to produce precise etching and clean incisions of the cornea. On two freshly enucleated human eyes radial incisions and a myopic keratomileusis were performed with a specially designed delivery system. The cornea was then studied by transmission and scanning electron microscopy. The surface of the irradiated area was extraordinarily smooth and clean with a precision greater than 10 nm. The epithelial cells were literally cleaved by the ablation process. The cytoplasm and the nucleus were cut without any damage to the other part of the cell and no disturbance of the cells proximal to the incision. The corneal stroma was cut in a regular and smooth fashion, and the aspects observed with the scanning electron microscope differed mainly from the surface observed after an incision made with a diamond knife. The excimer laser allowed optimal conditions for quick and safe wound healing but the long-term effects on the epithelial cells must be evaluated by further studies.

Cornea↗