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Biomedical subjects

G A Peyman

Publications and source records attributed to G A Peyman.

At least 37 records · Page 2Linked to original sources
PubMed1998

Toxicity of intraocular lidocaine and bupivacaine.

PURPOSE: To study the toxicity of intraocular lidocaine, bupivacaine, and a combination of the two anesthetics. METHODS: The right eyes of 34 rabbits were divided into eight groups, and each was injected intravitreally with 0.2 ml of lidocaine hydrochloride in a 2%, 1%, 0.5%, or 0.25% concentration, or bupivacaine hydrochloride in a 0.75%, 0.5%, or 0.25% concentration, or a 1:1 mixture of lidocaine 2% and bupivacaine 0.75%. The left eyes of four of these rabbits received an injection of balanced saline solution. Electroretinograms were recorded before injection and 30 minutes, 90 minutes, 3 hours, 6 hours, 24 hours, and 1 week after injection. The amplitude and the implicit time were analyzed. The rabbits were killed 1 week after injection and the eyes evaluated histologically. RESULTS: No adverse clinical reaction and no histologic abnormality was observed in any of the nine groups after injection. The a- and b-waves of the electroretinograms in the control group injected with balanced saline solution, and the a-waves of the experimental groups that received injections of lidocaine, bupivacaine, or the mixture, were normal. The b-waves of the experimental groups demonstrated a marked decrease in the amplitude and an increase (P < .05) in the implicit time after intravitreal injection. Electroretinogram responses recovered within 24 hours. CONCLUSIONS: Intravitreal injection of 0.2 ml of lidocaine up to 2%, or of bupivacaine up to 0.75%, and the mixture of lidocaine 2% and bupivacaine 0.75%, induced reversible electroretinogram changes in the rabbit retina. No histologic abnormalities were observed.

Anesthetics, Local↗
PubMed1998

Endoresection of the iris and ciliary body in epithelial downgrowth.

We present a case of epithelial downgrowth with intractable glaucoma after multiple intraocular surgeries. The eye was successfully managed with a pars plana approach. The iris and epithelial tissue over the ciliary body were removed with intraocular scissors and a vitrector combined with unipolar diathermy and endophotocoagulation. The use of moderate hypotensive anesthesia may have helped prevent intraoperative hemorrhage. During more than 3 years of follow-up, intraocular pressure ranged from 13 to 19 mm Hg, visual acuity was 20/80 with aphakic correction with a rigid gas-permeable lens, and there was no recurrence of epithelial downgrowth.

Adolescent↗
PubMed1998

An evaluation of methylated collagen as a substitute for vitreous and aqueous humor.

PURPOSE: To evaluate ocular tolerance of methylated collagen gel injected intravitreally and into the anterior chamber. METHODS: Methylated collagen (type I/III) was tested in New Zealand white rabbits. Vitreous cavity: After pars plana vitrectomy, methylated collagen gel was injected intravitreally. The eyes were examined clinically; electroretinogram recordings were made before and after surgery. Vitreous samples were taken for immunological analysis for the presence of the injected collagen. The rabbits were sacrificed 6 months after surgery; the retina was evaluated by light microscopy. Anterior chamber: In another group of rabbits, methylated collagen gel (0.2 ml, 0.1 ml, or 0.05 ml) was injected into the anterior chamber after paracentesis. The eyes were examined with a slit lamp; intraocular pressure was measured postinjection. The rabbits were sacrificed after 4 months; the corneas were evaluated histologically. RESULTS: Vitreous cavity: The fundus view was clear for 6 months after intravitreal injection. Scotopic and photopic electroretinograms were normal in 6/7 eyes; one eye experienced a mild decrease one month postoperatively. No abnormal changes were found in the retinal histology. Anterior chamber: Some corneas were hazy and edematous around the injection site for one week. The injected collagen appeared in bundles, patches, and little pieces in the anterior chamber with precipitates on the corneal endothelium, pupillary margin, and the anterior capsule of the lens. The collagen diminished gradually, without causing permanent opacity. Histologically, the corneal endothelium in the eye which received 0.2 ml collagen showed a mild distention of the mitochondriae and vesicle formation between endothelial cells under transmission electron microscope. CONCLUSION: Methylated collagen gel was tolerated by the eye after intravitreal injection. Localized temporary clinical and mild ultrastructural corneal changes were observed after anterior chamber injection.

Animals↗
PubMed1998

Toxicity and efficacy of intravitreal injection of spartanamicin B in the treatment of Candida endophthalmitis.

AIMS/BACKGROUND: We evaluated the retinal toxicity of spartanamicin B and its efficacy in a rabbit model of Candidal endophthalmitis. METHODS: Toxicity. Fourteen albino rabbit eyes were injected intravitreally with spartanamicin B (1, 2, 5, 10, 25, 50, and 100 microg); 2 eyes received the vehicle alone. Efficacy. Ten rabbit eyes were inoculated with 3000 Candida organisms which caused endophthalmitis in 24 hours. Eight eyes were treated with intravitreal spartanamicin B in doses of 1, 2, 5, or 10 microg/0.1 ml; 2 untreated eyes served as controls. RESULTS: Toxicity. The eyes injected with < or =10 microg and the control group eyes exhibited no clinical, histological, or electroretinographic evidence of retinal toxicity. Doses >10 microg caused vitritis. Efficacy. Clinical examination of the treated eyes showed a gradual improvement over 3-6 days; mild opacities remained until day 14. Results of cultures performed 15 days after infection were negative in all treated eyes. CONCLUSIONS: Intravitreally injected spartanamicin B (10 microg) is nontoxic to the retina, effective against C. albicans in the endophthalmitis model in the rabbit eye and caused no discernible histological changes in the retina.

Animals↗
PubMed1998

Internal resection of posterior uveal melanomas.

AIMS: To evaluate the safety and efficacy of internal resection in the treatment of malignant melanoma of the choroid. METHODS: 32 consecutive patients with histopathologically proved malignant choroidal melanomas were treated with internal resection. 29 of the 32 (90.6%) tumours were within 2 disc diameters of the optic nerve or fovea. The surgery was performed at two university centres by one of the authors. Follow up was between 1 and 85 months (mean 40.1 months). RESULTS: Three patients developed distant metastases and died of malignant melanoma (metastatic and mortality rate 9.4%). In one case, distant metastases developed in association with an intraocular recurrence. There have been no other intraocular recurrences. The most common postoperative complication was vitreous haemorrhage, which occurred in 12 patients (37.5%); cataract occurred in eight eyes; and three patients developed retinal detachment postoperatively. Three of the operated eyes have been enucleated (9.4%); a total of four (12.5%) have lost light perception. 10 patients (31.2%) had visual acuities of 6/60 or better and 18 of 32 (56.3%) were between 6/120 and light perception. CONCLUSION: These data suggest that the internal resection of posterior uveal melanomas is a reasonable globe saving management option. This treatment modality is particularly well suited to elevated tumours in close proximity to the optic nerve or fovea.

Adult↗
PubMed1998

Blood velocity in an experimental iris tumor.

BACKGROUND AND OBJECTIVE: Greene strain melanoma was implanted into the irides of eight nonpigmented rabbits to evaluate the blood flow in tumor vasculature. MATERIALS AND METHODS: Conventional scanning laser ophthalmoscopy was used in conjunction with fluorescent microsphere angiography (FMA). Changes were documented on SVHS videotape for later analysis. Individual microsphere movement was tracked through the tumor vessels. Subsequently, blood velocity measurements were taken. RESULTS: The tumor vessels were poorly organized and inefficient. Tumor blood velocity was up to 2.5 times slower compared with normal blood velocity in the unaffected iris of the same eye of the same rabbit (P = .05). Tumor blood flow could be qualitatively visualized in real time in the liver rabbit model. CONCLUSION: The ability to visualize fluorescent microspheres within the poorly organized tumor vasculature coupled with the reduced blood velocity in the tumor helps to explain the success of hyperthermic tumoricidal therapy, and may allow for development of more efficient and selective drug delivery systems and tumoricidal agents.

Animals↗
PubMed1998

Reversal of blood flow in experimental branch retinal vein occlusion.

BACKGROUND AND OBJECTIVE: To demonstrate that the obstructed vascular lumen of the experimentally induced branch retinal vein occlusion (BRVO) induces retrograde blood flow, resulting in flow from the occluded vein to the feeder arterioles. MATERIALS AND METHODS: Photocoagulation was used to create occlusion of the branch retinal vein in a monkey model (n = 2; 1 cynomolgus, 1 rhesus). Twenty-four hours following photocoagulation, the eyes were examined for evidence of vascular occlusive disease. Vascular occlusion was proven by fluorescent vesicle angiography with scanning laser ophthalmoscopy; these results were recorded to SVHS videotape. The images were then serially analyzed frame by frame to track individual microsphere movement. RESULTS: The authors observed retrograde flow proximal to the point of vessel obstruction and extending backward into the arterial system. CONCLUSIONS: This demonstrates the existence of retrograde flow in an experimental model of BRVO and might explain vascular complications seen in this disease process.

Animals↗
PubMed1998

Ocular vascular thrombosis following tin ethyl etiopurpurin (SnET2) photodynamic therapy: time dependencies.

BACKGROUND AND OBJECTIVES: To evaluate the optimal time from the end of photosensitizer injection to the commencement of light application for creating characteristic fundus lesions and the time to vascular occlusion following photodynamic therapy (PDT) with tin ethyl etiopurpurin (SnET2). MATERIALS AND METHODS: Following intravenous injection of SnET2 0.5 mg/kg or lipid emulsion alone, the fundus of rabbits was irradiated at different times (5 to 240 minutes) after photosensitizer injection using 664 +/- 7-nm laser light with an irradiance of 354 mW/cm2 and fluence of 20 J/cm2. Ophthalmoscopy and fluorescein angiography were performed 1 day after SnET2 PDT. In separate groups of rabbits, treated areas of the fundus were imaged within 30 minutes following PDT using fluorescein vesicle and microsphere angiography with scanning laser ophthalmoscopy to document time of vascular occlusion. All animals were killed 1 day following treatment and eyes were examined by histopathology. RESULTS: Areas of hypofluorescence (indicating vascular occlusion) were seen when activating laser light was applied 5 to 20 minutes after SnET2 injection. Retinal vessels remained perfused in all cases. The time to vascular occlusion was 70 to 120 and 40 to 90 minutes in nonpigmented and pigmented rabbits, respectively. No safety issues were seen. CONCLUSION: PDT with SnET2 was effective in occluding the choriocapillaris. Activating light needs to be applied within a specific time frame after photosensitizer injection to achieve vascular occlusion.

Animals↗
PubMed1998

Accidental subretinal injection of triamcinolone acetonide.

Approximately one-third of the contents of a 1-ml, 40-mg ampule of triamcinolone acetonide was accidentally injected into the subretinal space of the left eye of a 30-year-old man with chronic uveitis. The manufacturer provided a list of the contents of the ampule. A large, white subretinal mass was seen in the superotemporal quadrant. In subsequent days, the medication was seen to migrate inferiorly. Visual acuity in the left eye was 20/400. Subretinal hemorrhage and mild atrophy of the retinal pigment epithelium and choroid were observed superotemporally. Visual acuity returned to 20/100 (preinjection level) in 1 week. Four months postinjection, the superotemporal atrophy was more severe; the inferotemporal medication was minimally visible without producing significant chorioretinal atrophy. The visual acuity remained at 20/100 until the patient underwent cataract extraction and intraocular lens implantation; his vision then improved to 20/40. Steroids, when not accompanied by harmful vehicle substances, may be well tolerated by ocular tissues.

Adult↗
PubMed1997

The management of giant retinal tears using perfluoroperhydrophenanthrene. A multicenter case series. Vitreon Collaborative Study Group.

OBJECTIVE: The purpose of the study was to determine the predictors of success and evaluate the use of perfluoroperhydrophenanthrene as an intraoperative and postoperative tool in the management of giant retinal tears in a multicentered collaborative study. DESIGN: Multicentered prospective case series. PARTICIPANTS: Twenty-three centers consecutively enrolled 162 eyes of 161 patients with retinal tears 90 degrees or greater in circumferential extent. INTERVENTION: Perfluoroperhydrophenanthrene was used as an intraoperative surgical adjunct in all cases and left after surgery in 16 eyes (9.9%). MAIN OUTCOME MEASURES: Retinal reattachment and visual acuity. RESULTS: Intraoperative reattachment was achieved in 158 eyes (97.5%); 147 eyes (90.7%) remained attached at their most recent follow-up. Seventy-nine eyes (48.8%) experienced an improvement in their visual acuity, 26 eyes (16.0%) remained unchanged, and 57 (35.2%) worsened. Recurrent retinal detachment occurred in 80 patients (49.4%). Other significant postoperative complications included cataract formation in 20 (39.2%) of 51 eyes, macular pucker in 12 (7.4%), corneal decompensation in 10 (6.2%), and hypotony (intraocular pressure equal to or less than 5 mmHg) in 9 (5.6%). A chi-square analysis of preoperative characteristics showed that hypotony (P = 0.007), macular detachment (P = 0.020), a history of cataract extraction (P = 0.003), poor visual acuity (P = 0.000), giant tear extent greater than 180 degrees (P = 0.004), and higher grade proliferative vitreoretinopathy (P = 0.000) all predicted a poor visual outcome. Vitreon (Vitrophage, Inc., Lyons, IL) was left in 16 eyes (9.9%) for an extended postoperative retinal tamponade for between 3 and 1034 days (mean, 87.2 days). The Vitreon was well tolerated, and these eyes experienced a similar outcome and rate of retinal reattachment to the rest of the group. CONCLUSIONS: Vitreon is a safe and useful adjunct to pars plana vitrectomy in the management of giant retinal tears and may, additionally, be the perfluorocarbon liquid that can be used most safely as a temporary postoperative tool for extended retinal tamponade, reinforcing its role as a useful adjunct in the management of these complex retinal detachments.

Adolescent↗
PubMed1997

Management of dry retinal folds.

BACKGROUND: To describe the surgical technique used in the management of two cases of dry retinal folds which occurred following retinal detachment surgery. METHODS: Two patients with persistent dry retinal folds. RESULTS: Patients underwent complete vitrectomy and membrane peeling, followed by injection of perfluorocarbon liquid. The retina was prodded and massaged flat with a silicone-tipped cannula under the perfluorocarbon liquid. The folds disappeared and the retina remained flat. CONCLUSION: The use of gentle manipulation under heavy perfluorocarbon liquids is an effective strategy for managing longstanding dry posterior retinal folds.

Adult↗
PubMed1997

Surgical closure of macular hole using an absorbable macular plug.

BACKGROUND: The surgical management of macular holes has been a subject of controversy in recent years. Various techniques such as vitrectomy, membrane peeling, and gas tamponade with or without transforming growth factor-beta 2, and recently the use of autologous platelets have produced closure rates from 58% to 96%, depending on the stage of the hole. METHODS: The authors present preliminary results in a study of 19 consecutive patients with stage 3 or stage 4 macular hole who underwent vitrectomy followed by placement of an absorbable partially cross-linked gelatin plug in the macular hole. The vitreous cavity was filled with a nonexpanding gas or air alone; the patient was instructed to maintain prone positioning for 2-3 days. RESULTS: Anatomic attachment of the edges of the macular hole was achieved in 19 out of 19 patients with a minimum follow-up period of 6 months (average 11.5 months). CONCLUSIONS: A cross-linked gelatin plug can effectively reattach the edges of macular holes of stages 3 and 4. Its use is recommended only in macular holes in high myopes with posterior staphyloma or recurrent macular hole.

Absorption↗
PubMed1997

Surgical management of cataract and posterior chamber intraocular lens implantation in Fuchs' heterochromic iridocyclitis.

BACKGROUND: To determine the inflammatory course and level of visual rehabilitation after cataract extraction and posterior chamber lens implantation in patients with Fuchs' heterochromic iridocyclitis complicated by cataract. METHODS: In a clinical trial, 32 eyes (visual acuity of 20/160 or worse) of 30 patients underwent extracapsular cataract extraction (19 eyes) or lensectomy (13 eyes) accompanied by posterior chamber intraocular lens implantation. Indirect ophthalmoscopy was performed intraoperatively prior to intraocular lens implantation and the extent of vitreous haze was assessed. If vitreous haziness was 3+ or more, core vitrectomy (two eyes) or three-port pars plana deep vitrectomy (four eyes) was performed. RESULTS: After an average follow up of 14.4 months (6 to 24 months), there was no statistically significant increase in cell and flare in the anterior chamber and vitreous or in keratic precipitates compared with the preoperative status of the eyes. However, 12% of the eyes developed synechiae (anterior and/or posterior) in comparison to preoperative condition (p < 0.05). Eight-seven percent of the eyes gained visual acuity of 20/40 or better (P < 0.005). Using the logistic regression model, a higher level of preoperative inflammation was associated with reduced likelihood of gaining visual acuity of 20/25 or more (OR = 0.25, 95% CI 0.049, 1.255). The complications of surgery were synechiae, 12%; opaque posterior capsule, 12%; vitreous loss, 3%; chronic glaucoma, 3%; and retinal detachment, 3%. CONCLUSIONS: Implantation of a posterior chamber intraocular lens can be well tolerated in patients with Fuchs' heterochromic iridocyclitis. Vitrectomy, whenever indicated in addition to cataract extraction, improves visual rehabilitation.

Adolescent↗
PubMed1997

Liposome uptake by human retinal pigment epithelial cells in culture.

PURPOSE: To examine the internalization of liposomes containing various phospholipids by human retinal pigment epithelial (RPE) cells in culture. The internalization was compared to that exhibited by macrophages and fibroblast cells. METHODS: The uptake into cells was monitored by using a non-degradable, radioactive cholesterol-hexadecyl ether derivative and a pH-sensitive, water-soluble fluorescent dye. Variables tested to determine their effect on uptake included time, phospholipid concentration, the presence or absence of serum in medium and the presence or absence of cholesterol in the liposome bilayer. The most avidly ingested liposome was tested to determine its ability to deliver a liposome-dependent drug. RESULTS: Liposome uptake was time and concentration dependent. Uptake for RPE was maximal in serum-free media, while the opposite was true for the other cells tested. Cell survival following exposure to fluoroorotic acid-containing liposomes correlated with the radioactive cholesterol-hexadecyl ether and fluorescent dye uptake data. CONCLUSIONS: No single liposome carrier or set of conditions tested appeared to be optimum for the delivery of a cytotoxic agent to these three cell types. This bears consideration when designing strategies for the prevention and treatment of intraocular proliferative diseases such as proliferative vitreoretinopathy (PVR).

Adult↗