Relationship between macular hole size and the potential benefit of internal limiting membrane peeling.
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Epiretinal Membrane↗
Biomedical subjects
G A Williams
Publications and source records attributed to G A Williams.
Safety profile of the intravitreal streptokinase-plasmin complex as an adjunct to vitrectomy in the rabbit.
BACKGROUND: The generation of an atraumatic posterior vitreous detachment (PVD), a common goal in vitreoretinal surgery, is a challenge, particularly in children and young trauma patients. Plasmin has been proposed as an adjunct to vitrectomy to enzymatically generate a PVD. Low doses of streptokinase-activated plasmin were tested in human pilot studies. This dose-escalation study assesses the safety range of intravitreal human streptokinase-plasmin in rabbits. METHODS: Plasminogen was isolated from human plasma by affinity chromatography, followed by activation with streptokinase (1:1), to generate the streptokinase-plasmin complex. Enzyme doses from 0.1-7 activity units (AU, in 0.1 ml) were injected into the mid-vitreous of 35 eyes; six control eyes were injected with balanced salt solution (BSS, 0.1 ml). Thirty minutes after injection, a two-port vitrectomy was performed. Fundus and slit lamp examinations were performed on days 1 and 7. On days 2 and 7, bright flash electroretinography was performed and compared with preoperative recordings. Some animals receiving higher doses of streptokinase-plasmin (1-7 AU) were followed clinically and with electroretinography for up to 9 months. RESULTS: A mild-to-moderate inflammatory response was seen in both control and plasmin-treated eyes on day 1, but had disappeared completely by day 7 in most eyes. In the 7 AU group, inflammation was stronger and more protracted. Two of three eyes from this group developed wrinkling of the medullary rays; one of them showed discoloration and traction at the medullary rays in the late follow-up. Electroretinograms (ERGs) of vitrectomized control eyes showed the following changes from preoperative values: 48 h, a-wave -11.10% [no significant (n.s.)], b-wave -14.62% (P=0.046); 7 days, a-wave +9.18% (n.s.), b wave +11.69% (n.s.). For the enzyme-treated eyes: 48 h: a-wave -20.43% (P<0.001), b-wave -9.57% (p<0.001); 7 days: a wave -14.21% (P<0.001), b-wave +2.48% (P<0.001). There was no evidence of dose-dependent ERG changes in enzyme-treated eyes at doses up to 5 AU. Groups of up to 3 AU were investigated by light and transmission electron microscopy, without evidence of toxicity. CONCLUSION: Streptokinase-plasmin doses up to 3 AU were found to be safe when injected into rabbit eyes followed by vitrectomy.
Animals↗
Different cardiac response to copper in limpets from metal polluted and clean shores of Hong Kong.
The gastropod limpet, Cellana grata, is common on moderately exposed to exposed Hong Kong rocky shores. On the basis of the existing literature on trace metal contamination in Hong Kong, four sites were identified, representative of highly polluted (Aberdeen and Lei Yue Mun) and clean (Cape d'Aguilar and Clear Water Bay) conditions. Limpets from the two polluted sites showed similar, but significantly higher body concentrations of copper than limpets from the two clean sites, which were also similar. Non-invasive measurements of cardiac activity of limpets from the four sites showed between site differences in baseline heart rates under standard seawater, irrespective of pollution level. When acutely exposed to water borne copper (2 h, 0.5+/-0.06 SD ppm), however, limpets from clean sites showed a significantly higher increase in inter-beating time (bradycardia) than those from polluted sites. These results highlight the potential use of cardiac activity to assess the exposure of natural populations of limpets to trace metal pollution.
Animals↗
Indocyanine green mediated photothrombosis for the management of predominantly classic choroidal neovascularisation caused by age related macular degeneration.
AIMS: To study the effectiveness of indocyanine green mediated photothrombosis in the management of predominantly classic subfoveal choroidal neovascularisation associated with age related macular degeneration. METHODS: Prospective, non-comparative, interventional case series of nine patients with predominantly classic subfoveal choroidal neovascularisation secondary to age related macular degeneration who declined photocoagulation or verteporfin photodynamic therapy. Patients were submitted to one or more treatments with an intravenous injection of a small volume of high concentration indocyanine green solution followed by low irradiance, large spot 810 nm continuous laser application via a transpupillary approach. Main outcome measures were change in best corrected visual acuity and macular exudative manifestations. RESULTS: After 12 months of follow up, the final best corrected visual acuity was the same (plus or minus two ETDRS lines) in five eyes (55%), improved more than two ETDRS lines in three eyes (33%), and worsened by more than two lines in the remaining eye. The improved vision was probably related to partial or complete restoration of the macular architecture as a result of fluid resolution, whereas the worsened vision was primarily the result of treatment failure in achieving substantial choroidal neovascular occlusion. There were no complications related to the procedure. CONCLUSION: Indocyanine green mediated photothrombosis may be an effective alternative treatment for predominantly classic subfoveal choroidal neovascularisation caused by age related macular degeneration.
Aged↗
A new phenotype of recessively inherited foveal hypoplasia and anterior segment dysgenesis maps to a locus on chromosome 16q23.2-24.2.
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Chromosome Mapping↗
Visual adaptations in a diurnal rodent, Octodon degus.
The degu (Octodon degus) is a diurnal rodent, native to Chile. Basic features of vision and visual organization in this species were examined in a series of anatomical, electrophysiological and behavioral experiments. The lens of the degu eye selectively absorbs short-wavelength light and shows a progressive increase in optical density as a function of age. Electroretinograms recorded using a flicker-photometric procedure reveal three spectral mechanisms: a rod with peak sensitivity of about 500 nm and two types of cone having respective spectral peaks of about 362 nm and 507 nm. Opsin antibody labeling was used to determine the retinal distributions of the three receptor types. A total of about one-third of the approximately 9 million photoreceptors of the degu retina are cones with the two types (507 nm/362 nm) represented in a ratio of about 13:1. The contributions to vision of all three receptor types were examined in a series of behavioral experiments. A consistent feature of both the electrophysiological and behavioral results is that relatively high levels of light adaptation are required to effect the full transition from rod-based to cone-based vision. In behavioral tests degus were shown to be able to make color discriminations between ultraviolet and visible lights.
Adaptation, Ocular↗
Catalase-like oxygen production by horseradish peroxidase must predominantly be an enzyme-catalyzed reaction.
When hydrogen peroxide (H2O2) was provided as the only substrate for horseradish peroxidase C (HRP-C) the catalase-like emission of oxygen gas was observed. The reaction was favored at neutral compared to acidic pH. Addition of the superoxide radical scavengers tetranitromethane (TNM) or superoxide dismutase (SOD) increased activity. TNM's effect was concentration dependent but SOD's was not, indicating that only some of the superoxide generated was released into solution. Manganous ions (Mn2+) react with superoxide radicals to regenerate H2O2 but not oxygen; when added to the reaction medium oxygen production was reduced but not abolished. The effect was essentially concentration independent, suggesting that most oxygen was produced enzymatically and not by chemical disproportionation of superoxide. The catalase-like activities of some site-directed mutants of HRP-C suggest that active site residues histidine 42 and arginine 38 are influential in determining this activity. A clear correlation also existed between catalase activity and the enzymes' resistance to inactivation by H2O2. Computer simulation of a reaction scheme that included catalase-like activity agreed well with experimental data.
Arginine↗
Spectrum of luminescence from laser-created bubbles in water.
The spectrum of the luminescence emitted at the collapse of single laser-induced bubbles in water is measured for different maximum bubble radii. Bubbles as large as 2 mm show a molecular OH(*) band at 310 nm in the spectrum, which otherwise can be fitted approximately with a blackbody curve at a temperature of 7800 K. This finding provides a connection between the light emission of single bubbles and multibubble sonoluminescence, since in the latter case the same molecular band is observed. Surface instabilities are observed in the larger bubbles, and may be connected with the OH(*) emission.
Journal Article↗
Quenched Kosterlitz-Thouless superfluid transitions.
Rapidly quenched Kosterlitz-Thouless (KT) superfluid transitions are studied by solving the Fokker-Planck equation for the vortex-pair dynamics in conjunction with the KT recursion relations. Power-law decays of the vortex density at long times are found, and the results are in agreement with a scaling proposal made by Minnhagen and co-workers for the dynamical critical exponent. The superfluid density is strongly depressed after a quench, with the subsequent recovery being logarithmically slow for starting temperatures near T(KT). No evidence is found of vortices being "created" in a rapid quench; there is only decay of the existing thermal vortex pairs.
Journal Article↗
A comparison of visual results and complications in eyes with posterior chamber intraocular lens dislocation treated with pars plana vitrectomy and lens repositioning or lens exchange.
PURPOSE: To compare the visual results and the postoperative complications in eyes with posterior chamber intraocular lens (PCIOL) dislocation that underwent pars plana vitrectomy with lens repositioning with eyes that underwent pars plana vitrectomy with lens exchange. DESIGN: Nonrandomized consecutive comparative case series. PARTICIPANTS: Fifty-nine eyes (27 right eyes and 32 left eyes) of 56 subjects (28 women and 28 men) ranging in age from 59 to 90 years. Mean follow-up was 34 months. METHODS: A comparison of the best-corrected preoperative visual acuities, final visual acuities, and postoperative complications in subjects with dislocated PCIOLs that underwent pars plana vitrectomy. Logarithm of the minimum angle of resolution (LogMAR)-converted visual acuities were used for comparison. Categorical data were analyzed by Fisher's exact test, and population means were compared by a pooled Student's t test. MAIN OUTCOME MEASURES: Final mean visual acuities, change in mean visual acuities, and postoperative complications. RESULTS: For all 59 eyes the mean preoperative visual acuity was 20/152, and the mean final visual acuity was 20/48. Final visual results were similar between the eyes that underwent lens repositioning (20/55) and the eyes that underwent lens exchange (20/43; P = 0.19). Final visual results were also similar between the eyes that underwent lens exchange with sutured PCIOL placement (20/51) and the eyes that underwent lens exchange with anterior chamber intraocular lens (ACIOL) placement (20/38; P = 0.26). Final mean visual acuity in eyes that received an ACIOL (20/38) was better than in eyes that underwent repositioning of the dislocated lens into the ciliary sulcus (20/65; P = 0.01). The mean increase in visual acuities was greater for eyes with ACIOL placement compared with eyes with sutured PCIOL placement (P = 0.01). For all eyes, final visual results were unaffected by a concurrent diagnosis of age-related macular degeneration (20/52; P: = 0.71), glaucoma (20/48; P = 0.95), or postoperative cystoid macular edema (20/55; P = 0.45). Final visual acuities were significantly worse in eyes with a detectable preoperative afferent pupillary defect (20/200; P<0.0001). Postoperative retinal detachments developed in 4 of 29 eyes (14%) that underwent lens repositioning and in 2 of 30 eyes (7%) that had lens exchange (P = 0.42). Postoperative lens subluxations occurred in 6 of 29 eyes (21%) that underwent lens repositioning and in 1 of 30 eyes (3%) that underwent lens exchange (P = 0.05). CONCLUSIONS: The final visual results in eyes with dislocated PCIOLs that underwent pars plana vitrectomy with lens repositioning were similar to the visual results obtained in eyes that underwent pars plana vitrectomy with lens exchange. For eyes that underwent lens exchange, final visual results in eyes that received an ACIOL were similar to the visual results obtained in eyes that received a PCIOL; however, eyes with an ACIOL showed a greater increase in mean visual acuity. Eyes with a preoperative afferent pupillary defect had worse final visual results.
Aged↗
Clinical course and surgical treatment of macular epiretinal membranes in young subjects.
OBJECTIVE: To examine the surgical and nonsurgical visual outcomes of young subjects with idiopathic macular epiretinal membranes (ERMs). DESIGN: Retrospective observational and noncomparative interventional case series. PARTICIPANTS: Nineteen consecutive subjects (20 eyes) aged 40 years or less with an idiopathic macular ERM. METHODS: Group 1: 10 consecutive eyes were initially seen with visual acuity of 20/50 or better; 7 eyes were observed, and 3 eyes with progressive visual loss to <20/50 underwent vitrectomy and membrane peeling. Group 2: 10 consecutive eyes with presenting visual acuity of 20/60 or worse underwent vitrectomy and membrane peeling. MAIN OUTCOME MEASURES: Visual acuity, cataract formation, ERM recurrence, operative complications. RESULTS: Group 1: With no surgery, visual acuity remained stable or improved in 5 of 10 eyes (50%), with a mean follow-up of 3.7 years. Three of 10 eyes (30%) had visual loss < or =20/60 develop and underwent vitrectomy. Postoperative visual acuity improved an average of 6 lines with a mean follow-up of 17.6 months. Group 2: After vitrectomy, visual acuity improved 2 or more lines in 7 of 10 eyes (70%), with a mean improvement of 4.4 lines and mean follow-up of 29.2 months. Groups 1 and 2: Three of 13 eyes (23%) that underwent vitrectomy had recurrent ERM formation. CONCLUSIONS: Young subjects with idiopathic macular ERMs and a presenting visual acuity of 20/50 or better had a favorable visual outcome with observation. Subjects with an initial vision of 20/60 or worse, or those who had a visual decrease to < or =20/60 had significantly improved visual acuity after vitrectomy. ERM recurrence is relatively high after surgery.
Adolescent↗
Adult retinopathy of prematurity: outcomes of rhegmatogenous retinal detachments and retinal tears.
PURPOSE: To describe the results of retinal tears and rhegmatogenous retinal detachments (RD) in adults with retinopathy of prematurity (ROP). DESIGN: Noncomparitive interventional case series. METHODS: Retrospective cohort of 216 eyes of 108 patients, 15 years or older, followed for up to 23 years (median, 6.2 years). RESULTS: One eye was initially seen with an RD, and during follow-up 30 eyes had an RD develop. An additional surgical procedure was required in 7 of the 31 eyes (23%) with an RD. Four eyes were initially seen with retinal tears, and during follow-up 19 eyes had a retinal tear develop. Seven of the 23 eyes (30%) with a retinal tear had initial repair fail. Eyes with minimal cicatricial changes from ROP were still at high risk for tears and detachments developing. Eighty percent of eyes with retinal tears and 60% of eyes with an RD that started with vision >20/60 maintained that level of vision at the final examination. CONCLUSION: In patients with a history of premature birth, features of fundus examinations do not correlate with the occurrence of a retinal tear or RD. Repair of a tear or detachment in such a patient is more likely to require multiple procedures but can still be associated with good visual results. Physicians should consider widespread relief of vitreoretinal traction for a tear or detachment in any patient with a history of premature birth.
Adolescent↗
Autologous plasmin enzyme in the surgical management of diabetic retinopathy.
PURPOSE: This is a pilot study to assess the use of autologous plasmin enzyme (APE) as an adjunct to vitreous surgery in eyes with advanced diabetic retinopathy. DESIGN: Prospective noncomparative interventional case series. PARTICIPANTS: Seven patients with advanced diabetic retinopathy selected at random from our practice population. METHODS: Seven eyes were treated with APE as an adjunct to standard vitreous surgery. Six eyes had macular tractional retinal detachments, and one eye had refractory macular edema. Three fellow eyes had standard vitreous surgery performed for macular tractional retinal detachments without APE. All 10 eyes had macular edema and background diabetic retinopathy. MAIN OUTCOME MEASURES: The main outcome measures included induction of a posterior vitreous detachment, retinal reattachment, improvement in visual acuity, and resolution of macular edema. RESULTS: All seven APE-treated eyes achieved spontaneous or easy removal of the posterior hyaloid including one eye that had vitreoschisis over areas of detached retina. All eyes treated with APE had resolution of intraretinal edema. Retinas of all eyes treated with APE were reattached. The three fellow eyes were treated by vitreous surgery without APE. Two of the three fellow eyes had reattached retinas, but none had resolution of intraretinal edema without further focal photocoagulation treatment. Mean visual acuity improvement was 0.7 logarithm of the minimum angle of resolution (LogMAR) units in APE-treated eyes and 0.1 LogMAR units in eyes without APE. The average follow-up period was 14 months. CONCLUSIONS: This pilot study suggests that APE may be beneficial in the surgical management of diabetic retinopathy.
Adult↗
Surgical management of macular holes: a report by the American Academy of Ophthalmology.
OBJECTIVE: The document describes macular hole surgery and examines the available evidence to address questions about the efficacy of the procedure for different stages of macular hole, complications during and after surgery, and modifications to the technique. METHODS: A literature search conducted for the years 1968 to 2000 retrieved over 400 citations that matched the search criteria. This information was reviewed by panel members and a methodologist, and it was evaluated for the quality of the evidence presented. RESULTS: There are three multicenter, controlled, randomized trials that constitute Level I evidence and compare the value of surgery versus observation for macular hole. There are three multicenter, controlled, randomized trials studying the use of adjuvant therapy in macular hole repair. Postoperative vision of 20/40 or better has been reported in 22% to 49% of patients in randomized trials. The risks of surgical complications include retinal detachment (3%), endophthalmitis (<1%), cataract (>75%), and late reopening the hole (2% to 10%). CONCLUSIONS: The evidence does not support surgery for patients with stage 1 holes. Level I evidence supports surgery for stage 2 holes to prevent progression to later stages of the disease and further visual loss. Level I evidence shows that surgery improves the vision in a majority of patients with stage 3 and stage 4 holes. There is no strong evidence that adjuvant therapy used at the time of surgery results in improved surgical outcomes. Patient inconvenience, patient preference, and quality of life issues have not been studied.
Clinical Trials as Topic↗
Incidence of retinal detachment and visual outcome in eyes presenting with posterior vitreous separation and dense fundus-obscuring vitreous hemorrhage.
PURPOSE: To determine visual outcomes and the incidence of retinal detachment in eyes presenting with posterior vitreous separation and dense fundus-obscuring vitreous hemorrhage. DESIGN: Retrospective consecutive noncomparative interventional case series. PARTICIPANTS: Thirty-six eyes (15 right eyes and 21 left eyes) of 34 patients (18 female and 16 male) ranging in age from 42 to 94 years. Mean follow-up was 14 months. METHODS: A comparison of the best-corrected initial visual acuities versus final visual acuities after spontaneous resolution of vitreous hemorrhage or surgical intervention. The number of eyes that were found to have retinal tears or that had a rhegmatogenous retinal detachment develop was documented. Logarithm of the minimum angle of resolution-converted visual acuities was used for comparison. Categorical data were analyzed by Fisher's exact test, and population means were compared by Student's t test. MAIN OUTCOME MEASURES: Final mean visual acuities, number of eyes with at least one retinal tear, location of retinal tears, number of eyes that had retinal detachment develop, and the number of eyes repaired with scleral buckling surgery and/or pars plana vitrectomy. RESULTS: Twenty-four of 36 eyes (67%) were found to have at least one retinal break (range, 0-4 breaks), with 88% of breaks located in the superior retina. Eleven eyes (31%) had more than one retinal break. Fourteen of 36 eyes (39%) had a rhegmatogenous retinal detachment develop that was repaired with pars plana vitrectomy and scleral buckling. An additional 14 eyes (39%) underwent vitrectomy for nonclearing vitreous hemorrhage. The incidence of retinal detachment in eyes with a history of retinal detachment in the contralateral eye was 75% (P = 0.04). Seven of 14 eyes (50%) with retinal detachment had coexisting proliferative vitreoretinopathy. Most retinal breaks and detachments occurred in emmetropic or myopic eyes. For all 36 eyes the mean preoperative visual acuity was 20/1233, and the mean final visual acuity was 20/62 (P < 0.0001). Eyes that had a macula-off retinal detachment develop had worse final visual outcomes (20/264; P = 0.01), as did eyes that had proliferative vitreoretinopathy develop (20/129; P = 0.04). CONCLUSIONS: Acute, spontaneous, nontraumatic posterior vitreous separation with dense fundus-obscuring vitreous hemorrhage is associated with a high incidence of retinal tears and detachment. Close follow-up with clinical examination and ultrasonography is necessary, because many of these eyes may eventually require surgical intervention. Aggressive management with early vitrectomy should be considered when there is a history of retinal detachment in the contralateral eye.
Adult↗
Constrained global optimization for estimating molecular structure from atomic distances.
Finding optimal three-dimensional molecular configurations based on a limited amount of experimental and/or theoretical data requires efficient nonlinear optimization algorithms. Optimization methods must be able to find atomic configurations that are close to the absolute, or global, minimum error and also satisfy known physical constraints such as minimum separation distances between atoms (based on van der Waals interactions). The most difficult obstacles in these types of problems are that 1) using a limited amount of input data leads to many possible local optima and 2) introducing physical constraints, such as minimum separation distances, helps to limit the search space but often makes convergence to a global minimum more difficult. We introduce a constrained global optimization algorithm that is robust and efficient in yielding near-optimal three-dimensional configurations that are guaranteed to satisfy known separation constraints. The algorithm uses an atom-based approach that reduces the dimensionality and allows for tractable enforcement of constraints while maintaining good global convergence properties. We evaluate the new optimization algorithm using synthetic data from the yeast phenylalanine tRNA and several proteins, all with known crystal structure taken from the Protein Data Bank. We compare the results to commonly applied optimization methods, such as distance geometry, simulated annealing, continuation, and smoothing. We show that compared to other optimization approaches, our algorithm is able combine sparse input data with physical constraints in an efficient manner to yield structures with lower root mean squared deviation.
Algorithms↗
Sympathetic ophthalmia associated with pars plana vitrectomy without antecedent penetrating trauma.
PURPOSE: To evaluate, describe, and categorize the clinical presentation, clinical course, histopathology, and response to therapy in patients without a history of penetrating ocular trauma who developed sympathetic ophthalmia following pars plana vitrectomy. METHODS: The records of patients without a history of trauma who underwent pars plana vitrectomy and developed sympathetic ophthalmia were retrospectively reviewed. Cases were analyzed with respect to clinical presentation, fluorescein angiographic findings, anatomic and visual outcomes, histopathology, and response to therapy. RESULTS: Eight eyes were identified. The median age at presentation was 55 years, with a range of 14 to 62 years. The time from vitrectomy to diagnosis of sympathetic ophthalmia ranged from 2 months to greater than 2 years, with a median of 7 months. Six of eight patients (75%) presented with anterior chamber reaction. All eight patients presented with a vitreous inflammatory response. The optic nerve was inflamed clinically or angiographically in four of eight cases (50%). Small yellow-white sub-retinal pigment epithelial deposits were present in four of eight cases (50%). Two eyes had lesions characterized as multifocal choroiditis. One eye had larger yellow placoid-like lesions. One eye presented with vitritis but no retinal lesions. Subretinal choroidal neovascularization was noted in the inciting eye of one patient. Vision improved in the sympathizing eye with immunosuppressive therapy in five of eight cases (62.5%). CONCLUSIONS: Sympathetic ophthalmia can be seen following pars plana vitrectomy in patients without penetrating injuries or a history of trauma. Indeed, it may be seen after successful vitrectomy for retinal detachment. Diverse clinical presentations are possible, and persistent or atypical uveitis following vitrectomy should alert the surgeon to the development of sympathetic ophthalmia.
Adolescent↗
Presumed acquired ocular toxoplasmosis in deer hunters.
PURPOSE: To describe acquired ocular toxoplasmosis in deer hunters. METHODS AND RESULTS: The authors describe five young men presenting with flu-like symptoms followed by visual loss due to a unilateral, focal necrotizing retinitis. All five men gave a history of ingesting undercooked or uncooked venison. All five had elevated toxoplasma serology, and all five improved clinically with an antitoxoplasma regimen. CONCLUSION: In previously healthy young men, flu-like symptoms associated with visual loss and retinitis should prompt questioning about hunting and raw game meat ingestion, especially when toxoplasmosis is suspected.
Adolescent↗