Biomedical subjects

W E Smiddy

Publications and source records attributed to W E Smiddy.

At least 19 recordsLinked to original sources

PubMed1995

Laser energy and dye fluorescence transmission through blood in vitro.

PURPOSE: Because of the potential usefulness of evaluating and treating choroidal neovascularization obscured by blood, we designed this study to quantify the transmission of dye fluorescence and laser energy through blood. METHODS: Blood preparations anticoagulated with ethylenediaminetetraacetic acid with hematocrits of 0% (plasma), 46%, and 99% were placed in open cuvettes with path lengths of 100, 200, or 500 microns and were exposed for one minute to either 100% oxygen or 100% carbon dioxide. Each cuvette was then sealed. Photographs of the cuvettes of blood in front of a flask of fluorescein or indocyanine green solution were decoded and used to calculate the percent transmission of fluorescence through blood. Cuvettes of blood were also placed in the path of argon, krypton, and diode lasers for energy transmission measurements. RESULTS: Plasma transmission of fluorescein and indocyanine green fluorescence and argon, krypton, and diode laser energy was 89% to 100% for all samples tested. Transmission of fluorescein fluorescence and argon laser energy through 99% hematocrit samples were both less than 5%. Transmission of indocyanine green fluorescence through 100-, 200-, and 500-microns-thick cuvettes filled with 99% hematocrit blood was 57%, 34%, and 4%. Transmission of krypton laser energy was 50%, 25%, and 6%; and transmission of diode laser energy was 60%, 35%, and 12% through 99% hematocrit blood. Intermediate transmission values were obtained for 46% hematocrit samples. CONCLUSIONS: Krypton and, to a slightly greater degree, diode laser energy penetrate a thin film of blood. Indocyanine green fluorescence also penetrates a thin film of blood. If a layer of blood appears thinner than 500 microns, then indocyanine green angiography may be useful in imaging underlying pathologic features. If a lesion can be imaged with indocyanine green, then it can probably be treated with a krypton or diode laser.

Blood↗

PubMed1995

Pars plana vitrectomy for chronic pseudophakic cystoid macular edema.

PURPOSE: We determined the efficacy of pars plana vitrectomy in a series of patients with chronic pseudophakic cystoid macular edema. METHODS: Clinical records were reviewed on 24 consecutive patients who underwent pars plana vitrectomy in one eye for chronic pseudophakic cystoid macular edema. All 24 patients had failed to improve on medical therapy and had preoperative evidence of either vitreous adhesions to anterior segment structures (23 eyes) or iris capture of the intraocular lens (one eye). RESULTS: The mean, best-corrected Snellen visual acuity was 20/190 preoperatively (median, 20/200; range, 20/50 to 3/200) and 20/52 postoperatively (median, 20/40; range, 20/20 to 20/400 [P < .0001]). Visual acuity improved postoperatively in all 24 eyes, with a mean improvement of 4.7 Snellen lines (range, one to eight lines). There was no highly significant difference in preoperative visual acuity (P = .41) or postoperative visual improvement (P = .17) between patients with anterior as opposed to posterior chamber intraocular lenses. Longer time interval from cataract surgery to vitrectomy did not correlate with less postoperative visual improvement. CONCLUSIONS: In pseudophakic eyes with chronic cystoid macular edema, vitreous adhesions to anterior segment structures, and visual loss that is unresponsive to medical therapy, pars plana vitrectomy with removal of these vitreous adhesions may lead to improved visual acuity.

Aged↗

PubMed1995

Endophthalmitis after pars plana vitrectomy. The Postvitrectomy Endophthalmitis Study Group.

PURPOSE: To describe the clinical course and incidence of culture-proven postvitrectomy endophthalmitis in 18 patients from five academic centers and three private practices. METHODS: Patients undergoing pars plana vitrectomy for recent trauma or endophthalmitis were excluded. The average age was 58 years (range, 21-85 year). Sixty-one percent of the patients (11/18) had diabetes mellitus. The indication for initial vitrectomy was vitreous hemorrhage (n = 10), macular epiretinal membrane (n = 3), recurrent retinal detachment with proliferative vitreoretinopathy (n = 2), retinal detachment with retinoschisis (n = 1), proliferative diabetic retinopathy with tractional retinal detachment (n = 1), and dislocated intraocular lens (n = 1). None of these eyes received prophylactic intraocular antibiotics during the vitrectomy. RESULTS: All eyes were treated with intraocular antibiotics after the diagnosis of postvitrectomy endophthalmitis was made. Final visual acuity ranged from 20/20 to no light perception and included five eyes with 20/50 or better visual acuity and 11 eyes with less than 5/200 visual acuity. Nine eyes had a final visual acuity of no light perception. Of the 16 eyes infected with a single organism, 71% (5/7) of eyes infected with coagulase-negative staphylococci retained 20/50 or better final visual acuity compared with no eyes (0/9) infected with other organisms (P = 0.005). Two eyes infected with both coagulase-negative Staphylococcus and Streptococcus had a final visual acuity of 20/400. Three eyes with a total hypopyon later had enucleation or evisceration. Based on the data from four medical centers, the incidence of endophthalmitis after pars plana vitrectomy performed over the last 10 years was 9/12,216 (0.07%). CONCLUSION: Endophthalmitis after vitrectomy is rare. Postvitrectomy bacterial endophthalmitis caused by organisms other than coagulase-negative staphylococci has a poor visual prognosis.

Adult↗

PubMed1995

Primary intraocular lens implantation in the setting of penetrating ocular trauma.

PURPOSE: To evaluate the clinical outcome of patients who underwent lensectomy and intraocular lens (IOL) implantation at the time of primary repair of a penetrating ocular injury. METHODS: A review of 14 patients who sustained cataracts and lens rupture in the setting of a corneal laceration to determine anatomic and visual outcome, in addition to complications related to the primary IOL. RESULTS: The IOL remained anatomically stable in all 14 patients with no complications encountered at implantation or after surgery. Final visual acuity in 9 of the 14 patients was 20/40 or better. Six patients underwent pars plana vitrectomy for removal of an intraocular foreign body. CONCLUSION: Intraocular lens implantation at the time of lensectomy and primary repair of a corneal laceration allows good visual rehabilitation with restoration of binocular function and serves as an alternative to contact lens correction in select patients.

Adolescent↗

PubMed1995

Surgical management of dislocated intraocular lenses.

Intraocular lens (IOL) malpositions range from simple IOL decentration to luxation into the posterior segment. Many surgical techniques and approaches have been devised to treat visually significant IOL dislocation. In this series, 78 eyes with IOL dislocation were managed by anterior segment and vitreous surgeons with a variety of surgical techniques using a limbal, pars plana, or combined limbal-pars plana approach. Most of the dislocated lenses were posterior chamber IOLs. In 39 of 78 eyes (50%), final visual acuity was 20/50 or better. Neither surgical approach nor management technique appeared to be related to outcome. The timing of surgery did not appear to affect visual outcome but was not examined in a randomized fashion. Guidelines for determining optimal management are presented.

Adult↗

PubMed1994

Treatment of massive subretinal hemorrhage from complications of scleral buckling procedures.

Vitrectomy techniques permit removal of subretinal hemorrhage, but the prognosis varies and depends principally on the cause of the hemorrhage. Nine consecutive patients undergoing pars plana vitrectomy with internal drainage of massive subretinal hemorrhage from complications of scleral buckling procedures were studied, to evaluate the long-term results. In all eyes, the final visual acuity was improved, compared with preoperative visual acuity, and was 20/80 or better in seven of nine cases. Recurrent retinal detachment secondary to proliferative vitreoretinopathy developed in two patients, but complete retinal reattachment was achieved after further procedures were performed. Patients with massive subretinal hemorrhage from complications of scleral buckling procedures comprise a subgroup of patients with subretinal hemorrhage in which internal drainage via pars plana vitrectomy is an acceptable alternative to observation only and may result in improved visual acuity outcomes.

Adult↗

PubMed1994

Acute retinal necrosis caused by reactivation of herpes simplex virus type 2.

Acute retinal necrosis is a severe form of necrotizing retinitis. Acute retinal necrosis has been demonstrated to be caused by varicella-zoster virus and herpes simplex virus type 1. We treated three patients with acute retinal necrosis apparently caused by recrudescence of latent herpes simplex virus type 2. Primary viral infection was probably congenital, with documented perinatal herpes simplex virus type 2 infection in two patients. Bilateral chorioretinal scars were present in two patients, neither of whom had a history of ocular herpetic infection, suggesting that earlier subclinical chorioretinitis had occurred. In each case, periocular trauma preceded the development of retinitis by two to three weeks. These cases are evidently caused by trauma-induced reactivation of latent virus rather than the onset of a primary infection.

Acyclovir↗

PubMed1994

Differentiating macular holes from macular pseudoholes.

Surgical treatments of macular holes have become increasingly effective in inducing resolution of the cuff of surrounding subretinal fluid, resulting in increased vision in many patients. However, for many conditions that mimic a macular hole, either surgery is not indicated or different surgical manipulations are necessary. Differentiating macular holes from some forms of macular pseudoholes can be difficult or impossible based solely on clinical examination. Adjunctive tests that may enhance the accuracy of diagnosis are either not feasible or not available to most clinical practices. We evaluated three clinic-based tests for their value in allowing the differentiation between macular holes and macular pseudoholes: Amsler grid testing, Watzke-Allen sign, and laser aiming beam test. These tests were evaluated in three groups of clinically defined patients: those with full-thickness macular holes, those with macular pseudoholes, and those who had previously undergone successful macular hole treatment. Although the Amsler grid testing was sensitive in correlating with clinically defined macular holes, it was not specific. The Watzke-Allen sign and, to a greater extent, the laser aiming beam test were extremely sensitive and specific in correlating clinically defined full-thickness macular holes and pseudoholes. These tests improve the accuracy of diagnosis of full-thickness macular holes.

Aged↗

PubMed1994

Retained lens fragments after phacoemulsification.

PURPOSE: The authors present the clinical features of patients with retained lens fragments after phacoemulsification and their outcome after pars plana vitrectomy. METHODS: The authors performed a retrospective chart review of 62 patients who had surgical management of posteriorly dislocated lens fragments after phacoemulsification during the 3-year period from January 1990 to December 1992. RESULTS: Eight of the 62 patients underwent vitrectomy on the same day as the cataract surgery. Of the remaining 54 patients examined in the outpatient clinic, initial clinical features included marked intraocular inflammation (87%), elevated intraocular pressure of 30 mmHg or higher (46%), and corneal edema (46%). Retinal detachment was present before vitrectomy in one patient and occurred after vitrectomy in two others. Initial visual acuity was 20/200 or worse in 68% of patients. After vitrectomy, final visual acuity was 20/40 or better in 68% of patients. Using the percentage of patients with 20/40 or better final visual acuity, there was no statistically significant difference in surgery performed within 7 days (70%), between 1 and 4 weeks (60%), and after 4 weeks (70%). Twenty (80%) of 25 patients with initial posterior chamber intraocular lenses (PC IOLs) and 16 (62%) of 26 patients with initial anterior chamber IOLs (AC IOLs) achieved 20/40 or better visual acuity. A visual acuity outcome of 20/200 or worse occurred in all three patients with retinal detachment. Six of the eight patients who underwent vitrectomy on the same day as the cataract surgery achieved 20/30 or better visual acuity. CONCLUSIONS: The timing of vitrectomy did not influence visual acuity outcomes. Intraocular lenses inserted at the primary operation did not adversely affect the visual outcome. However, vitrectomy on the same day as cataract surgery generally yielded favorable visual acuity outcomes and eliminated the need for a second operation at a later date. In most patients with retained lens fragments, management with vitrectomy allowed good visual acuity outcomes.

Aged↗

PubMed1994

Use of the potential acuity meter and laser interferometer to predict visual acuity after macular hole surgery.

PURPOSE: As reported anatomic success rates for macular hole surgery increase, a method of accurately predicting postoperative visual acuity has increased clinical utility. METHODS: A series of 18 patients undergoing vitrectomy for idiopathic macular holes was evaluated prospectively for best refracted preoperative visual acuity, potential acuity meter (PAM) reading, and laser interferometer (LI) reading. Best refracted visual acuity after surgery was recorded and analyzed to assess the predictive value of the PAM and LI readings. RESULTS: The LI correctly predicted the final visual result in 6 of the 10 patients who achieved a final visual acuity of 20/50 or better (P = < 0.011). The PAM did not accurately predict postoperative visual acuity for any of the eyes with a final visual acuity of 20/50 or better. Both correctly predicted outcome in the 7 patients with final visual acuity worse than 20/50. The LI prediction was within 2 lines of final visual acuity in 12 (70%) of 17 anatomically successful cases, and the PAM was within 2 lines of final visual acuity in 11 (64%) of 17 cases. CONCLUSION: Both the LI and PAM were modestly accurate in predicting final visual acuity after macular hole surgery, but the LI was more accurate in predicting a visual acuity of 20/50 or better.

Aged↗

PubMed1994

Vitrectomy for pars plana placement of a glaucoma seton.

Trabeculectomy, even with supplemental antifibrosis agents, has a low success rate in controlling intraocular pressure (IOP) in certain cases; ones involving severe anterior-chamber-angle disease are particularly challenging. Ten patients with advanced, non-neovascular glaucoma underwent vitrectomy and pars plana placement of seton implants. The tube was placed through the pars plana sclerotomy in each case because severe anterior chamber angle narrowing, aphakia, or penetrating keratoplasty prevented standard placement. Previous trabeculectomy had failed to control IOP in 9 of the 10 patients. In each, the preoperative IOP was 25 mm Hg or more despite maximal medical therapy. In nine of the patients, the postoperative IOP was 19 mm Hg or less, without pressure-lowering agents. The seton appeared to be functional in all of the cases. Vision remained stable or improved in seven cases, but deteriorated in three due to graft failure, progressive traction retinal detachment, or rhegmatogenous retinal detachment (one case each). Pars plana placement of tubes for glaucoma seton implants should be considered as an alternative to anterior chamber placement in certain cases of refractory glaucoma in which the anterior chamber anatomy has been severely disrupted.

Adult↗

PubMed1994

Macular hole syndromes. Echographic findings with clinical correlation.

BACKGROUND: Anatomic characteristics of macular holes may be difficult to define, even with contact lens biomicroscopy. With the advent of successful macular hole surgical techniques, accurate diagnosis has become increasingly important to avoid unnecessary or incorrect surgery. Echography may provide additional diagnostic information in some cases. The purpose of this study is to correlate echographic and intraoperative clinical features of macular holes. METHODS: The echographic features and intraoperative findings in 25 patients were compared. The spectrum of identifiable echographic features included (1) a thin, smooth, membrane-like surface minimally elevated over the macula (limited posterior vitreous face separation); (2) macular thickening; (3) an operculum; and (4) a complete posterior vitreous face separation. Intraoperative clinical findings included the presence or absence of (1) a thin, limited posterior vitreous face separation, (2) a subretinal fluid cuff, (3) an operculum, and (4) a complete posterior vitreous face separation. RESULTS: Echographic and intraoperative findings correlated regarding the limited posterior face separation in 23 of 25 patients, a surrounding subretinal fluid cuff (macular thickening) in 24 of 25 patients, an operculum in 19 of 25 patients, and complete posterior vitreous face separation in 24 of 25 patients. Thus, echography was very effective in detecting the position of the posterior vitreous face. Overall, echography correlated accurately with 90 (90%) of 100 of these four features. CONCLUSION: Echographic features correlate accurately with clinical features.

Fundus Oculi↗

PubMed1993

Accidental skin punctures during ophthalmic surgery.

PURPOSE: Accidental skin puncture carries the risk of both hepatitis B and human immunodeficiency virus transmission. There have been studies of the incidence of these skin punctures in general surgery, but no study has focused on ophthalmic surgery. METHOD: All incident reports of skin punctures in the Bascom Palmer Eye Institute operating rooms from January 1990 through November 1991 were reviewed retrospectively. The incidence of skin puncture also was studied propsectively from December 1991 through May 1992. During the prospective phase, the healthcare worker was asked to complete an anonymous form regarding the instrument involved, whether it was clean or contaminated, the persons involved, and whether the room lights were on or off. RESULTS: There were 37 such occurrences in 14,878 operations (0.25%) during the retrospective study and 12 in 4246 operations (0.28%) in the prospective period. In only one case was the instrument contaminated by contact with a patient known to have positive serology for the human immunodeficiency virus. There were no documented seroconversions of healthcare personnel for either hepatitis B or human immunodeficiency virus. In 63% of these occurrences, the penetrating instrument was known to be definitely contaminated with the patient's blood. Only one person was handling the instrument 84% of the time. CONCLUSION: The low but present danger to ophthalmic personnel during surgical procedures justifies precautions to decrease the occurrence of skin punctures.

Accidents, Occupational↗

PubMed1993

Transforming growth factor-beta 2 significantly enhances the ability to flatten the rim of subretinal fluid surrounding macular holes. Preliminary anatomic results of a multicenter prospective randomized study.

Previous studies of treatment of full-thickness macular holes have effected resolution of the surrounding subretinal fluid cuff in 58%-71% of cases. An initial report has found 330 ng and 1,330 ng transforming growth factor-beta 2 to be successful in effecting resolution of the surrounding subretinal fluid cuff in 100% of cases. A randomized, masked, controlled, prospective, multicenter study of 90 patients with full-thickness macular holes was performed to assess the efficacy of the local application of TGF-beta 2 at the time of vitrectomy surgery. Eligibility criteria included: (1) best corrected visual acuity of 20/80 or worse; (2) duration of macular hole for less than 1 year; and (3) absence of other ocular disorders that might interfere with vision. Patients were evenly randomized to receive placebo, 660 ng transforming growth factor-beta 2, or 1,330 ng transforming growth factor-beta 2. The treatment assignment was unmasked at the examination 3 months after treatment only if the macular hole failed to close. If the initial treatment had been placebo, patients were offered crossover to 1,330 ng transforming growth factor-beta 2 during a reoperation. It can be deduced that resolution of the subretinal fluid cuff occurred in 16 of 30 placebo-treated eyes, 53 of 58 eyes treated with transforming growth factor-beta 2, and in 9 of 13 cases (69%) initially treated with placebo that subsequently underwent repeat surgery under the crossover option.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗

PubMed1993

Scleral buckle removal following retinal reattachment surgery: clinical and microbiologic aspects.

Scleral buckle infection following retinal reattachment surgery is infrequent but not rare. We identified 45 cases among approximately 3000 scleral buckling procedures performed at our institution between July 1, 1985 and July 1, 1991. The scleral buckle was exposed in all 45, and the subsequent microbiologic culture was positive in 33. The most common causative organism was coagulase negative staphylococci (17 of 33 cases with positive cultures). Risk factors for an adverse outcome included positive culture, preoperative vision < or = 20/200, and preoperative retinal detachment. Broad spectrum antibiotics covered organism sensitivity profiles in 16 of the 18 cases tested. Prompt removal of infected buckles and treatment with broad-spectrum topical antibiotics are important for maintaining vision.

Adult↗

PubMed1992

Histopathologic results of retinal diode laser photocoagulation in rabbit eyes.

Diode laser photocoagulation was applied to rabbit retina simulating scatter treatment using an endolaser probe and in a manner simulating treatment of peripheral retinal breaks using a transscleral retinopexy probe. Clinically appearing mild, moderate, and severe burns were created by altering the burn duration in one eye and by altering the power setting in the fellow eye. Histopathologic results demonstrated the clinically evident dose-response effect with sparing of inner retinal cellular elements with mild burns and full-thickness retinal cell loss with severe burns. Bruch's membrane ruptures were seen in three of 42 endophotocoagulation severe spots placed with high power, but in none of the 42 severe spots placed with long burn duration. Thus, longer burn duration appeared to be a safer way to produce a severe burn than higher power. Burns characteristically bloomed during the several seconds following laser application by both modalities, possibly indicating a deep source of energy absorption. Scleral effects, seen only when high energy levels were used to treat atrophic areas, were mild.

Animals↗

PubMed1992

Diode endolaser photocoagulation.

Endolaser photocoagulation was applied using a diode laser in 25 patients. Indications were for treatment of complications of proliferative diabetic retinopathy (17 patients), proliferative vitreoretinopathy (four patients), complex retinal detachments (three patients), and a retinal break (one patient). Good retinal and retinal pigment epithelial laser uptake was observed in all cases. The clinical appearance of the burn while it is being made is similar to that with the argon laser, but it is subtly lighter, especially in less-pigmented areas and eyes. Predictable clinical results and no adverse effects have been observed. While the clinical utility of the diode laser is analogous to that of standard argon endolaser systems, numerous logistical advantages are offered by this system.

Adult↗

PubMed1992

Histopathologic characteristics of diode laser-induced chorioretinal adhesions for experimental retinal detachment in rabbit eyes.

A retinal break and localized retinal detachment were induced in 10 rabbit eyes. The retinal break was treated within regions of detached retina using diode laser transscleral retinopexy (four eyes), diode laser indirect ophthalmoscopy (two eyes), or retinocryopexy (two eyes). Two eyes were left as untreated controls. The clinical and histopathologic effects were studied 1 day and 3 weeks after initial treatment. Suitable chorioretinal adhesions were induced with all treatment modalities. The extent of tissue effects was greater in cryopexy and smaller in laser treatment. The histopathologic characteristics of the lesions induced by diode laser indirect ophthalmoscopy were similar to those seen with transscleral diode treatment and were more focal than those seen with cryopexy. Transscleral and transpupillary diode laser photocoagulation were effective in inducing chorioretinal adhesions in detached retina in this experimental model in rabbits.

Animals↗