Search PubMed⌕ Search

Biomedical subjects

D P Han

Publications and source records attributed to D P Han.

At least 91 records · Page 5Linked to original sources
PubMed1990

The effect of scleral buckling on ocular rigidity.

In a study of enucleated human eyes, the authors investigated the effect of scleral buckling on the ocular pressure-volume relationship. Intraocular pressure was recorded continuously during intravitreal infusion of saline solution before and after the application of encircling silicone elements. Scleral buckling produced a marked reduction in ocular rigidity, with reversibility of the effect on removal of the buckling elements. Similar results were obtained during incremental intravitreal air injection. The authors propose that the greater extensibility of silicone compared with sclera and the induced alterations in ocular shape are the primary factors responsible for the observed change in ocular rigidity. The clinical implications of these findings for intravitreal gas injection are discussed.

Aged↗
PubMed1990

Tissue plasminogen activator for postvitrectomy fibrin formation.

The authors injected 25 micrograms of recombinant tissue plasminogen activator (tPA) into the anterior chamber or vitreous cavity of 23 eyes of 22 patients with severe intraocular fibrin formation that developed after vitrectomy surgery for complicated cases of proliferative vitreoretinopathy (PVR) (13 eyes), diabetic traction retinal detachment (TRD) (7 eyes), or endophthalmitis (3 eyes). Tissue plasminogen activator injected an average (+/- standard deviation) of 73 +/- 63 hours after vitrectomy surgery resulted in complete fibrinolysis in 21 of 23 eyes and partial fibrinolysis in one eye. The mean time to fibrin resolution was 3.0 +/- 1.0 hours. Four eyes required repeat tPA injection for recurrent fibrin formation; repeat injection resulted in complete fibrinolysis in each case. The mean follow-up duration after tPA administration was 6 months. At the final follow-up examination, the retina was totally attached in 18 of 23 eyes and was partially attached in 2. Visual acuity improved in 12 eyes (52%); it was at least 20/400 in 8. Complications of tPA injection included hyphema (2 patients) and corneal stromal thickening (2 patients). Mild, transient, periocular pain that was easily managed with non-narcotic analgesia developed in three patients.

Adolescent↗
PubMed1989

Treatment of postvitrectomy fibrin pupillary block with tissue plasminogen activator.

We injected 25 micrograms of recombinant tissue plasminogen activator into the anterior chamber or the vitreous cavity in seven aphakic patients for pupillary block caused by a complete fibrin pupillary membrane that formed after vitrectomy with fluid-gas exchange. Progressive fibrin deposition resulted in pupillary block by three days after vitrectomy surgery in six patients, and seven days after vitrectomy in one patient. The pupillary block was associated with increased intraocular pressure in six patients. Tissue plasminogen activator was injected via the corneoscleral limbus in five patients and via the pars plana in two patients. In all patients, injection of tissue plasminogen activator resulted in complete fibrinolysis of the fibrin pupillary membrane within four hours, associated with a deepening of the anterior chamber. In the six patients with increased intraocular pressure at the time of tissue plasminogen activator injection, dissolution of the fibrin membrane was associated with a decrease in pressure. In all patients, intraocular pressure had returned to normal by three days after the injection. No complications were associated with the injection.

Adult↗
PubMed1989

Retinal hemorrhage predicts neurologic injury in the shaken baby syndrome.

Shaken baby syndrome consists of intracranial and intraocular hemorrhage in the absence of signs of direct trauma in infants who have sustained whiplash/shaking injuries. We evaluated 14 consecutive cases of presumed shaken baby syndrome seen at the University of Michigan Hospitals, Ann Arbor, between August 1983 and March 1988, to determine if the severity of retinal hemorrhage was predictive of the severity of acute neurologic injury. The severity of retinal hemorrhage was based on the type and size of hemorrhage and the extent of fundus involvement. We found a significant correlation between retinal hemorrhage severity and acute neurologic findings. Diffuse fundus involvement, vitreous hemorrhage, or large subhyaloid hemorrhages were associated with more severe acute neurologic injury.

Brain Injuries↗
PubMed1989

Mechanisms of intraocular pressure elevation after pars plana vitrectomy.

A prospective study of 222 consecutive patients undergoing pars plana vitrectomy was done to determine the incidence and mechanisms of postoperative intraocular pressure (IOP) elevation. Within 48 hours of surgery, postoperative IOP increased by at least 5 to 22 mmHg in 136 eyes (61.3%) and to 30 mmHg or more in 79 eyes (35.6%). Presumed mechanisms of open-angle glaucoma included intraocular gas expansion (28.4%), inflammatory trabecular meshwork obstruction (4.5%), silicone oil-related glaucoma (3.6%), and erythroclastic glaucoma (2.2%). Closed-angle mechanisms included pupillary block glaucoma (6.8%) and ciliary body edema (3.6%). Factors which were associated with postvitrectomy pressure elevation included placement of a scleral buckle, either intraoperatively (P = 0.003) or before vitrectomy (P = 0.001), intraoperative scatter endophotocoagulation (P = 0.041), intra-operative lensectomy (P = 0.024), and development of postoperative fibrin membranes (P = 0.038). Surgery was required to lower IOP or relieve pupillary block in 25 eyes (11.3%).

Adolescent↗
PubMed1988

Vitrectomy for traumatic retinal incarceration.

Traumatic retinal incarceration into a scleral wound may prevent successful surgical rehabilitation of eyes with severe posterior segment injury. We managed 15 consecutive eyes with traumatic retinal incarceration and associated retinal detachment with vitrectomy techniques. We based our approach on the anteroposterior location of the incarceration site and the amount of retina incarcerated into the wound. Despite successful anatomic reattachment in six of seven eyes with retinal incarceration posterior to the vortex vein ampullae, only two of seven eyes achieved visual acuity of 5/200 or better. In eyes with more peripheral retinal incarceration, anatomic reattachment was achieved in five of eight eyes and visual acuity of 5/200 or better was achieved in four eyes. Overall, a visual acuity of 5/200 or better was achieved in six (40%) of 15 eyes with a minimum follow-up of six months.

Adolescent↗
PubMed1988

Surgical excision of the attached posterior hyaloid.

When vitrectomy is performed in eyes without posterior vitreous detachment, complete removal of the posterior hyaloid may be important to relieve existing vitreoretinal traction or to remove a surface for subsequent cellular proliferation. We used two alternative techniques of detaching the posterior hyaloid in an unselected consecutive series of ten patients; we used either a tapered extrusion needle or a microvitreoretinal blade to initiate separation of the posterior hyaloid at the optic disc margin. After surgical peeling of the posterior hyaloid from the retina, complete removal of the posterior vitreous and surgical relief of posterior vitreoretinal traction were facilitated.

Dissection↗
PubMed1988

Photocoagulation to prevent retinal detachment in acute retinal necrosis.

Retinal detachment (RD) occurs in more than 50% of eyes with acute retinal necrosis (ARN) and is the leading cause of visual loss in this syndrome. In order to decrease the incidence of RD in ARN, the authors treated 12 eyes of 10 patients with prophylactic laser photocoagulation. Retinal detachment occurred in two eyes (17%). Over the same time period, seven eyes with ARN did not receive prophylactic laser treatment, most often because of dense vitreous debris, with a 67% rate of RD. Prophylactic photocoagulation treatment should be considered in the management of patients with ARN.

Acute Disease↗
PubMed1988

Visual loss after successful photocoagulation of choroidal neovascularization.

A retrospective study was performed on 75 eyes with presumed ocular histoplasmosis syndrome and 59 eyes with aging macular degeneration to determine risk factors for visual loss in the early postoperative period after successful laser photocoagulation of primary and recurrent choroidal neovascular membranes (CNVMs). Despite successful obliteration of neovascularization, visual loss of two lines or greater occurred in 18.8% of eyes with presumed ocular histoplasmosis syndrome and 40.4% of eyes with aging macular degeneration (mean follow-up, 33.6 weeks). Factors which predicted visual loss after treatment included a short distance of CNVMs from the foveal center (P = 0.002), good preoperative visual acuity (P = 0.003), increased area of CNVM (P = 0.025), and postoperative internal limiting membrane wrinkling (P = 0.017). Eyes with CNVMs greater than 0.8 mm2 in area or less than 0.6 mm from the foveal center had at least twice the frequencies of visual loss of eyes without these characteristics.

Adult↗
PubMed1988

Regression of disc neovascularization by photocoagulation in the acute retinal necrosis syndrome.

Disc neovascularization developed in one eye of a 40-year-old white woman with the acute retinal necrosis syndrome. Krypton laser scatter photocoagulation was placed in areas of nonnecrotic and segmentally nonperfused retina that were demonstrated by fluorescein angiography. Marked reduction in disc neovascularization was noted clinically 16 days after laser treatment and was confirmed angiographically 4 weeks after treatment. Neovascularization was completely regressed at 9 weeks after treatment. The authors postulate that the retinal vasculitis and nonperfusion produced retinal ischemia which stimulated neovascular proliferation, and that photocoagulation caused regression of the neovascularization.

Adult↗
PubMed1987

Laser photocoagulation in the acute retinal necrosis syndrome.

Acute retinal necrosis (ARN) is a syndrome of fulminant necrotizing vaso-occlusive retinitis associated with a high incidence of retinal detachment due to retinal breaks and vitreous traction. We performed argon or krypton laser photo-coagulation to demarcate areas of active retinitis as prophylaxis against retinal detachment in five patients with ARN. Patients were concomitantly treated with antiviral agents, systemic steroids, and antiplatelet therapy. One patient required multiple additional treatments as retinal necrosis progressed. The retinas remained attached in all five patients over a mean follow-up period of 15 months. By creating a chorioretinal adhesion in areas of potential retinal break formation, laser photocoagulation may be an effective prophylaxis against retinal detachment in ARN.

Acute Disease↗
PubMed1987

Occlusion of bridging or avulsed retinal vessels by repeated photocoagulation.

A technique is described for occlusion of bridging vessels associated with retinal breaks, and recurring vitreous hemorrhage. Argon laser photocoagulation, applied around and to the vessel in repeated sessions, produces scarring and progressive thinning of the retina until laser energy absorbed in the deep pigmented layers can reach the vessel and occlude it. Seventeen patients presenting with vitreous hemorrhage from bridging vessels were treated. Vitreous hemorrhage recurred in only two patients, one of whom had not returned for completion of treatment. The authors conclude that repeated argon laser photocoagulation is a safe, simple, and effective method for preventing recurrent vitreous hemorrhage from bridging vessels.

Aged↗