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Biomedical subjects

D P Han

Publications and source records attributed to D P Han.

At least 19 recordsLinked to original sources
PubMed1995

High-resolution magnetic resonance imaging evaluation of blood-retinal barrier integrity following transscleral diode laser treatment.

OBJECTIVE: To compare the effects of contact transscleral diode laser treatment and retinal cryotherapy on blood-retinal barrier integrity with the use of high-resolution magnetic resonance imaging techniques with constant infusion of gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA). METHODS: Transscleral diode laser photocoagulation and retinal cryotherapy were used to treat equivalent areas of the inferior retinal periphery of pigmented rabbits. Magnetic resonance imaging time-course studies with measurement of signal enhancements due to Gd-DTPA leakage were conducted 2 and 15 days following treatment. RESULTS: Two days following treatment, cryotherapy-treated eyes exhibited a mean (+/- SD) effective Gd-DTPA permeability coefficient of 4.6 +/- 0.8 x 10(-6) cm/s; in comparison, diode laser-treated eyes exhibited 1.6 x 1.4 x 10(-6) cm/s effective permeability. Significant decreases in the effective permeability were also noted 15 days after treatment in both groups. CONCLUSIONS: Transscleral contact probe diode laser photocoagulation induces less disruption of the blood-retinal barrier than does conventional cryotherapy. In addition, the continuous infusion method of Gd-DTPA delivery is a reliable and easily interpretable alternative to the commonly used bolus injection approach.

Animals↗
PubMed1995

Experimental transconjunctival diode laser retinal photocoagulation through silicone scleral exoplants.

OBJECTIVE: To study the feasibility of inducing a chorioretinal lesion under a previously placed scleral buckle by experimental transconjunctival diode laser photocoagulation. METHODS: We performed transconjunctival diode laser photocoagulation in the peripheral retinas of seven pigmented rabbit eyes with a silicone exoplant (No. 42 band or No. 276 tire) and seven eyes without an exoplant. Each eye received burns with an intensity of grades 1 to 3 in different quadrants at varying power levels, with a 0.5-second duration and 650-micron spot size. Eyes were enucleated for histopathologic studies 1 day and 1 week after treatment. RESULTS: Although the irradiance emitted through the No. 42 band and the No. 276 tire was attenuated by 17% and 23%, respectively, the range of threshold powers needed to produce grades 1 to 3 burns was similar between eyes with and without a silicone exoplant. At 1 day, full-thickness coagulative necrosis was observed in all lesions, except that the ganglion cell layer and inner nuclear layer were preserved in two of four grade 1 burns and the ganglion cell layer was intact in one of six grade 2 burns. Inner scleral changes were noted acutely in three of five grade 3 lesions. At 1 week, burns of all intensity grades showed a full-thickness atrophic chorioretinal lesion with inner scleral changes. CONCLUSIONS: Experimental transconjunctival diode laser photocoagulation through hard silicone elements reproducibly created a chorioretinal lesion with histopathologic findings similar to those of lesions obtained without these elements. Although retinal photocoagulative effects were prominent, inner scleral abnormalities were also observed histologically.

Animals↗
PubMed1995

Comparison of scleral tensile strength after transscleral retinal cryopexy, diathermy, and diode laser photocoagulation.

OBJECTIVES: To determine the effect of transscleral diode photocoagulation on the tensile strength of sclera in an experimental rabbit model and to compare it with that of transscleral cryotherapy and diathermy. METHODS: Twenty-four Dutch-belted rabbits received one of the following three treatment modalities in one eye: (1) transscleral cryotherapy, (2) transscleral diathermy, or (3) transscleral diode laser photocoagulation. The opposite eye served as a paired control. Tensile strength measurements of scleral strips excised from areas of treatment were obtained 6 weeks later. RESULTS: No statistically significant difference in mean tensile strength was observed between eyes receiving transscleral cryopexy (n = 7) or transscleral diode photocoagulation (n = 8) and their corresponding, paired, control eyes. In contrast, transscleral diathermy reduced mean scleral tensile strength to 26% of that of the paired control eyes (n = 8, P = .0001). CONCLUSIONS: In this rabbit model, scleral weakening is significant following transscleral diathermy while transscleral cryopexy or transscleral diode photocoagulation produces no significant weakening relative to paired, untreated controls.

Animals↗
PubMed1995

Histopathologic study of autosomal dominant vitreoretinochoroidopathy in a 26-year-old woman.

The clinicopathologic findings were obtained from enucleated eyes, obtained post mortem, of a 26-year-old woman with autosomal dominant vitreoretinochoroidopathy. Light microscopy demonstrated atrophic, disorganized peripheral retina with retinal blood vessels obscured by pigmented cells surrounding periodic acid-Schiff-positive deposits. Peripheral retinal pigment epithelial cells showed multilayering and pigmentation, with a thickened basal lamina. By electron microscopy, the peripheral retinal vessel endothelium was replaced by an arrangement of morphologically polarized pigmented cells of presumed retinal pigment epithelial origin oriented with their basal surfaces toward a fibrillar matrix occupying the vessel lumen. The similarity of the findings in this young patient to those of an aged patient described previously suggest that autosomal dominant vitreoretinochoroidopathy is an early-onset dystrophy of the peripheral retina with minimal subsequent progression, characterized by a retinal pigment epithelial response that includes marked intraretinal migration and extracellular matrix deposition.

Adult↗
PubMed1995

Vitrectomy for proliferative diabetic retinopathy with severe equatorial fibrovascular proliferation.

PURPOSE: We studied the surgical treatment and visual outcome in a consecutive series of eyes with an unusual syndrome of diabetic retinopathy and severe peripheral fibrovascular proliferation involving the equatorial and pre-equatorial fundus. METHODS: In a retrospective study of 276 eyes (245 patients) that underwent pars plana vitrectomy for diabetic retinopathy between November 1988 and February 1993, nine eyes of eight patients (3.3% of eyes and 3.3% of patients) had severe equatorial fibrovascular proliferation. The condition occurred primarily in previously unoperated-on eyes (except for panretinal photocoagulation) and resulted in peripheral traction or traction-rhegmatogenous retinal detachment (six eyes), severe vitreous hemorrhage (two eyes), and severe hypotony (one eye). Relief of traction from peripheral fibrovascular membranes was obtained with an encircling scleral buckle (nine eyes) and limited delamination and segmentation (five eyes) or relaxing retinectomy (two eyes). Lensectomy was required for adequate membrane dissection in three eyes. RESULTS: After follow-up of six to 52 months (mean, 20.4 months), the visual acuity was 20/200 or better in seven of nine eyes, with complete retinal attachment in seven of nine eyes and postequatorial attachment in all eyes (100%). Poor outcome resulted from a persistent response resembling Coats' disease in one eye and preexistent long-standing retinal detachment in one eye. CONCLUSIONS: Vitrectomy for severe equatorial fibrovascular proliferation differs from conventional approaches to diabetic retinopathy in that relief of retinal traction must be attained by scleral buckling and adequate dissection of peripheral fibrovascular tissue. In advanced cases, lensectomy and relaxing retinotomy may be required.

Adult↗
PubMed1995

Premacular hemorrhage as a sign of subacute bacterial endocarditis.

PURPOSE/METHODS: We examined a patient with mitral valve insufficiency, a sudden decrease in vision in the right eye, and premacular hemorrhage, which was a sign of subacute bacterial endocarditis. RESULTS/CONCLUSION: The patient was hospitalized and treated with intravenous antibiotics. Blood cultures grew Streptococcus viridans. Ocular symptoms and signs improved over two months. Premacular hemorrhage may be a sign of subacute bacterial endocarditis and may obscure other classic signs. Subacute bacterial endocarditis should be included in the differential diagnosis of premacular hemorrhage.

Acute Disease↗
PubMed1995

Combined pars plana vitrectomy-lensectomy and open-loop anterior chamber lens implantation.

PURPOSE: To investigate the effectiveness of open-loop, one-piece, flexible, Kelman-style, all-polymethylmethacrylate (PMMA) anterior chamber intraocular lenses (AC IOLs) in patients undergoing pars plana vitrectomy surgery for a variety of vitreoretinal disorders. METHODS: Fifteen patients (6 women and 9 men) underwent combined pars plana vitrectomy with insertion of an open-loop AC IOL. Postoperative results were evaluated. RESULTS: The average preoperative visual acuity of 20/360 (logMAR scale, 1.25 +/- 0.80) improved to 20/52 (logMAR scale, 0.42 +/- 0.35) after an average follow-up of 10.2 months (range, 1-41 months). Of 15 eyes, 7 (47%) achieved a visual acuity of better than 20/40. There was no evidence of glaucoma exacerbation or corneal decompensation. Visual acuity was limited primarily by chronic cystoid macular edema in 4 (27%) of 15 eyes. CONCLUSION: In this preliminary series of patients, open-loop, flexible, all-PMMA, Kelman-style AC IOLs appear to be well tolerated and represent a viable, simple alternative to transscleral fixation of a posterior chamber IOL or surgical aphakia in patients undergoing vitrectomy surgery.

Adult↗
PubMed1994

Management of complex retinal detachment with combined relaxing retinotomy and intravitreal perfluoro-n-octane injection.

We evaluated intravitreal perfluoro-n-octane injection for the positioning of large retinal flaps after relaxing retinotomies. Nineteen eyes underwent vitrectomy for advanced retinal detachments from proliferative vitreoretinopathy (11 eyes), trauma (five eyes), and proliferative diabetic retinopathy (three eyes). After retinotomy and complete relief of traction, injection of perfluoro-n-octane to a level anterior to the retinotomy edge was used to remove subretinal fluid thoroughly from beneath the retinal flap. All irrigation fluid anterior to the perfluoro-n-octane meniscus was aspirated before perfluoro-n-octane removal. Final tamponade was obtained with gas (four eyes) or silicone oil (15 eyes). After six to 17 eyes) or silicone oil (15 eyes). After six to 17 months of follow-up, the retinas were attached in 13 eyes (68%), and visual acuity of 5/200 or better was obtained in eight eyes (42%). Subretinal migration of perfluoro-n-octane and posterior slippage of the retinal flap occurred during perfluoro-n-octane/silicone oil exchange in one eye. No other complications were detected. Perfluoro-n-octane injection is an effective technique for positioning large retinal flaps after relaxing retinotomy.

Adolescent↗
PubMed1994

The effects of silicone oil removal. Silicone Study Report 6.

OBJECTIVE: To evaluate the advisability of removing silicone oil from eyes after surgery for severe (with a classification of at least C-3) proliferative vitreoretinopathy. DESIGN: Subgroup analysis of the Silicone Study, a randomized, multicentered, surgical trial. SETTING: Community- and university-based clinics. PATIENTS: Two hundred twenty-two eyes with severe proliferative vitreoretinopathy followed up in the Silicone Study. INTERVENTIONS: Vitrectomy for proliferative vitreoretinopathy with silicone oil as the intraocular tamponade. OUTCOME MEASURES: Changes in visual acuity, recurrent retinal detachment, and incidence of complications. RESULTS: Ninety-nine (45%) of 222 eyes had surgery for silicone oil removal (oil-removed eyes). Compared with the eyes that did not undergo silicone oil removal (oil-retained eyes) evaluated at a comparable time after oil injection, oil-removed eyes at the examination prior to oil removal were more likely to be attached (85% vs 40%; P < .0001), have a visual acuity of 5/200 or greater (63% vs 35%; P < .0001), and not be hypotonous (5% vs 22%; P < .001). There was no association between the length of oil retention and incidence of recurrent retinal detachment after oil removal. Eyes with attached retinas at the time of oil removal generally improved in visual acuity at the last follow-up examination (P < .0001), which was not evident in eyes with detached retinas at the time of oil removal. In a matched-pair cohort analysis comparing both sets of eyes, there was an increased risk for recurrent retinal detachment at the last follow-up examination in the oil-removed eyes (odds ratio [OR], 2.1; P = .09). However, overall visual acuity improved for oil-removed eyes in 19 (29%) of 66 pairs and for oil-retained eyes in one (2%) of 66 pairs (OR, 19.0; P < .0001). Although nonsignificant, incidence rates of keratopathy (OR, 0.5) and hypotony (OR, 0.5) were lower in oil-removed eyes. CONCLUSION: Removal of silicone oil in anatomically successful eyes significantly increases the likelihood of improved visual acuity with a slight increase in the likelihood of recurrent retinal redetachment. There was a trend for a reduction in the incidence of complications in the oil-removed eyes.

Adult↗
PubMed1994

Segmental infarction of the testicle: atypical presentation of a testicular mass.

Segmental infarction of the testis represents a rare entity. To our knowledge 11 cases have been reported in the literature. We report 4 additional cases of segmental testicular infarction masquerading as testis tumors. Inability to distinguish these benign lesions from malignant testis tumors resulted in orchiectomy in all 4 cases.

Adult↗
PubMed1994

A modified en bloc excision technique during vitrectomy for diabetic traction retinal detachment. Results and complications.

PURPOSE: The visual results and complications were determined for a modified en bloc excision technique for management of diabetic traction macular detachment. PATIENTS AND METHODS: A consecutive series of 30 eyes with this condition underwent pars plana vitrectomy, during which all posterior hyaloid except for portions essential for membrane dissection were excised. Bimanual dissection techniques then allowed excision of fibrovascular membranes "en bloc" with the retained hyaloid. RESULTS: After 6 to 44 months of follow-up, visual acuity of 5/200 or better was obtained in 23 (77%) of 30 eyes, with complete reattachment in 29 (97%) of 30 eyes. Iatrogenic retinal breaks occurred in 6 (20%) of 30 eyes. Two eyes required repeat vitrectomy. CONCLUSIONS: The modified en bloc excision technique allowed similar visual outcome, a higher reattachment rate, and less postoperative morbidity than previously reported surgical approaches to diabetic traction macular detachment.

Adult↗
PubMed1994

Evaluation of anterior segment tolerance to short-term intravitreal perfluoron.

PURPOSE: A study was performed to evaluate corneal and anterior segment toxicity from short-term (24-hour) intravitreal use of perfluoro-n-octane. METHODS: Forty aphakic, vitrectomized eyes of pigmented rabbits underwent intravitreal injection of either 0.5 ml of perfluoro-n-octane (Perfluoron; Infinitech, St. Louis, MO; treated) or 0.5 ml balanced saline solution (control). Perfluoron was allowed to remain in the vitreous cavity for 24 hours. Serial measurements of corneal pachymetry and pneumotonometry were performed at 1, 4, 12, and 24 hours after injection. After 24 hours, endothelial cell morphology and barrier function were evaluated. RESULTS: No significant differences in corneal thickness or intraocular pressure were noted between the two groups at any of the time points studied, and no differences in endothelial cell density/hexagonality or endothelial cell barrier function were observed 24 hours after injection. CONCLUSIONS: In the absence of sustained corneal contact, no evidence of significant acute corneal or anterior segment toxicity was observed in response to short-term intravitreal perfluoro-n-octane in aphakic, vitrectomized rabbit eyes.

Animals↗
PubMed1994

Postoperative fibrin formation and visual outcome after pars plana vitrectomy.

PURPOSE: To determine whether postvitrectomy fibrin formation was associated with visual outcome, a prospective study of patients undergoing pars plana vitrectomy was performed. METHODS: In 121 patients undergoing vitrectomy at the Medical College of Wisconsin between July 1986 and April 1989, the association of fibrin formation and other perioperative factors with visual outcome was evaluated by univariate and multivariate regression analysis. Poor visual outcome was defined as visual acuity worse than 5/200. RESULTS: After a median follow-up period of 23 months (range 6 to 51 months), patients with severe fibrin formation experienced a higher rate of poor visual outcome (19 of 26 patients, 73%) than patients with little or no fibrin formation (23 of 95 patients, 24%; P < 0.0001, univariate analysis). After adjusting for a variety of factors with multivariate regression analysis, fibrin formation was not significantly predictive of final visual outcome. CONCLUSIONS: Factors associated with postvitrectomy fibrin formation may affect visual outcome more than fibrin formation itself.

Adolescent↗
PubMed1993

Perioperative choroidal hemorrhage at pars plana vitrectomy. A case-control study.

PURPOSE: Risk factors for choroidal hemorrhage during pars plana vitrectomy surgery are currently not well defined. The authors analyzed potential risk factors for perioperative choroidal hemorrhage at pars plana vitrectomy in a case-control study. METHODS: Of 683 consecutive vitrectomy procedures, 13 cases of choroidal hemorrhage were identified in the operative or immediate postoperative period. Fifty vitrectomy controls from the same period were randomly selected and were compared with the hemorrhage cases by univariate analysis with respect to various potential risk factors. RESULTS: The incidence of choroidal hemorrhage associated with vitrectomy was 1.9%. Statistically significant risks (P < or = 0.05) included: greater age (mean, 70.9 versus 52.1 years); elevated preoperative pressure (19.9 versus 13.0 mmHg); preoperative diagnosis of rhegmatogenous retinal detachment (relative risk, 8.1); aphakic or pseudophakic status (relative risk, 5.2); and scleral buckle procedure at vitrectomy (relative risk, 12.0). Eyes with previous ocular trauma and previous vitrectomy had a reduced risk of choroidal hemorrhage. The incidence of severe visual loss (final visual acuity < 5/200) did not differ significantly from controls. CONCLUSIONS: Significant risk factors for choroidal hemorrhage are identified in this study which may help to identify patients at increased risk for this complication. Good visual outcome is possible after choroidal hemorrhage at vitrectomy (69% with visual acuity > 5/200).

Aged↗
PubMed1993

Choroidal rupture and optic atrophy.

The association between post-traumatic optic disc pallor and traumatic choroidal rupture is poorly understood. To further define this relationship, nine cases of indirect traumatic choroidal rupture and post-traumatic optic disc pallor were compared with cases of indirect choroidal rupture without disc pallor in terms of severity of ocular injury, fundus findings, and visual outcome. The type and severity of the injury did not appear to influence the risk of optic disc pallor. Optic disc pallor was associated with a slightly poorer long term visual acuity than eyes without pallor (p = 0.059). The presence of a relative afferent pupillary defect was strongly associated with optic disc pallor (p = 0.016). Peripapillary retinal pigment epithelial abnormalities were a common finding, suggesting peripapillary trauma as a cause for optic disc pallor.

Adolescent↗