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Biomedical subjects

I Karpouzas

Publications and source records attributed to I Karpouzas.

17 recordsLinked to original sources
PubMed1996

[Macular fibrosis after surgery of retinal detachment].

PURPOSE: To report the prevalence and visual outcome of macular pucker occurring after retinal detachment surgery, and to analyze its risk factors. METHODS: We retrospectively studied 865 cases of retinal detachment that had been successfully treated in the absence of macular hole or proliferative vitreoretinopathy higher than grade C1. For the statistical analysis, 63 variables were submitted to CHI-square test. RESULTS: Macular pucker occurred in 68 cases (7.7%). Final visual acuity was 0.5 or better in 24 cases, spontaneously in 7 and after macular surgery in 17. In 6 other cases, macular pucker was much less important in terms of visual impairment than coexisting amblyopia or other posterior pole pathology. In the 38 remaining cases, macular pucker was the cause of visual failure, despite macular surgery in 9 of them. Retinal detachment recurred after macular surgery in 2/26 cases. Nine variables were found to correlate with an increased risk of macular pucker: emmetropia, hyperopia, preoperative acuity reduced to light perception-hand movement, macula off, preoperative proliferative vitreoretinopathy (grade B or C1), retinal tears up to 30 degrees, retinal tears larger than 30 degrees, and cumulative retinal break area larger than 3 disks. CONCLUSION: Our results show that macular surgery can be useful in case of macular pucker after retinal detachment surgery. They also suggest that macular pucker and proliferative vitreoretinopathy have some risk factors in common.

Adolescent↗
PubMed1995

Pseudophakic retinal detachment: anatomic and visual results.

BACKGROUND: Our purpose was to report the anatomic and visual results of pseudophakic retinal detachment surgery in a large series of consecutive cases and to analyze the risk factors for anatomic and functional failure. METHODS: This retrospective study covered 290 primary cases of idiopathic rhegmatogenous retinal detachment operated on by the same surgeon during an 8-year period. Data relating to 26 pre-, per-, and postoperative variables were studied. For the statistical analyses we used both Chi-square and stepwise logistic regression tests. RESULTS: Vitreous loss occurred in 56 cases (19.3%), and the retina detached more than 2 years after lens extraction in 108 cases (37.2%). Breaks could be identified in 249 cases (85.8%), and the macula was involved in 235 (81%). The overall reattachment rate was 85.2% (247/290), and a postoperative visual acuity of 0.5 D or more was attained in 49.6% of cases (144/290). We found no difference between phakoemulsification, extracapsular, intracapsular techniques or between anterior chamber, posterior chamber, iris-fixated lenses as regards anatomic and functional outcomes. Proliferative vitreoretinopathy (PVR) and photoreceptor dysfunction were the main causes of anatomic and functional failure respectively. We identified extensive detachment, preoperative choroidal detachment, intraoperative hemorrhage and surgery for PVR as predictors of anatomic failure, while preoperative inflammation, preoperative PVR of grade B or worse, and surgery for PVR were predictors of functional failure. CONCLUSION: In this series, anatomic and visual results of reattachment surgery were much more affected by detachment features and by PVR than by the techniques and complications of cataract surgery.

Adult↗
PubMed1995

Visual acuity after scleral buckling surgery.

We reviewed 745 cases of retinal detachment which had been successfully treated by scleral buckling and had presented without preoperative ocular problems precluding visual recovery. Final visual acuity (VA) was 0.5 or better in 517 cases (69.4%). The main causes of final VA below 0.5 were photoreceptor dysfunction, macular pucker, cystoid macular edema, and intraoperative retrofoveal hemorrhage. Stepwise logistic regression analysis revealed that five variables predicted visual failure: patient's age of 71 years or more; preoperative VA reduced either to light perception counting fingers or to 0.1-0.4; low or high macular detachment for more than 7 days; grade B preoperative proliferative vitreoretinopathy, and intraoperative hemorrhage.

Adolescent↗
PubMed1995

[Vitrectomy in the treatment of simple retinal detachment].

PURPOSE: To report the indications and results of vitrectomy in the treatment of uncomplicated retinal detachment. METHODS: This retrospective study covered 103 vitrectomies that were carried out during an 8-year period for the treatment of rhegmatogenous retinal detachment without severe proliferative vitreoretinopathy, macular hole, or giant tear. Mean follow-up time was 20.3 months. RESULTS: The indications for vitrectomy were vitreal opacities in 32 cases, unseen or uncertain retinal breaks despite a good retinal view in 9 cases, a difficult arrangement of breaks in 34 cases, severe vitreal traction in 15 cases, and iatrogenic intraocular bleeding in 13 cases, 6 of them referred. In all, retinal breaks were uncertain or invisible in 49 cases. A buckle was used in 83 cases and an internal tamponade in 93. After vitrectomy, the retina was reattached in 76 cases, and after further surgery in 88 (85.4%). With vitrectomy, we were able to confirm or to detect all breaks in 36 cases. Of the 13 intraoperatively unseen breaks, 10 were responsible for vitrectomy failure. Late recurrence after more than 6 months was observed in 5 cases (4.9%). Secondary cataract was observed in 22 (66.6%) of the 33 phakic cases that had been operated on successfully and without complication. CONCLUSION: Our results indicate that vitrectomy is a useful procedure in the management of certain cases of uncomplicated rhegmatogenous retinal detachment. However, secondary cataract is a problem, and the risk of late recurrence needs further evaluation.

Adolescent↗
PubMed1994

Clinical risk factors for proliferative vitreoretinopathy after retinal detachment surgery.

PURPOSE: To identify the clinical risk factors for the development of severe proliferative vitreoretinopathy (PVR) after retinal detachment surgery. METHODS: A retrospective study of 1020 patients with either no PVR or with PVR of grade C1 or less at initial examination was conducted. After surgery, severe PVR was defined as grade C2 or worse. The data relating to 94 variables were evaluated by univariate analysis and stepwise logistic regression. RESULTS: Severe PVR developed after surgery in 107 patients (10.5%). Ten significant predictive variables were identified: minor intra- or postoperative hemorrhage, grade A preoperative PVR, preoperative choroidal detachment, giant tears, air tamponade, detachment involving more than 2 quadrants, cumulative break area larger than 3 optic disks, postoperative choroidal detachment, signs of uveitis at initial examination, and grade B preoperative PVR. CONCLUSION: The results indicate that in addition to the size of breaks, extent of detachment, and presence of preoperative inflammation or low-grade PVR, iatrogenic problems also are important factors in the pathogenesis of severe PVR after surgery for retinal detachment.

Aged↗
PubMed1991

Modelling and numerical optimization of corneal rotation.

Rotational ipsilateral penetrating autokeratoplasty can be performed for patients whose vision is impaired by corneal opacities overlying the pupil and where an adequate area of clear peripheral cornea is present. A method is presented for determining the maximum clear central corneal area that can be obtained by rotational autokeratoplasty and the most appropriate trephine size and placement. The mathematical modelling consists of estimating the shape of the opacity perimeter using nonlinear constrained optimization.

Cornea↗
PubMed1991

Microcomputer software applied to corneal stromal biometry.

Here we report a new method for image analysis of the corneal stroma. To obtain the biometric characteristics of a given area, we perform three different treatments of the same image. These automated predictions closely match each parameter (length, surface area, etc.), as measured manually by a "blind investigator." Furthermore, to obtain quantifiable, average values, we have increased the number of successive image measurements, which has led to the development of a series of programs designed to optimize automated data handling. Finally, the acquired, calculated parameters are summarized in the form of intermediate tables for each series of images, and as a final summary table incorporating t-test values and permitting comparison between two stromas (e.g., normal and pathological). Multivariate analysis and an ascending hierarchical classification demonstrate the main trends in differences of pathological vs. normal stroma.

Algorithms↗
PubMed1991

Computerized method for rotational autokeratoplasty.

The aim of our study was to formulate the procedure of rotational autokeratoplasty; that is, design the computer system and software necessary to automatically define the parameters of the problem. To achieve this, we used a CCD camera (Nikon) and a microcomputer with an integrated IMAGENIA (Biocom) interface software card (512 x 512 pixels and 100 gray levels), which permitted acquisition and digitalization of photographs of the lesioned cornea. Digitization of the image allowed us to determine the coordinates (x,y) of the points that lay on the lesion periphery as well as the coordinates of the corneal center; i.e., the geometric center of the cornea. The center of trephination and the optimal diameter of trephination can then be calculated as a function of a point situated on the lesion edge.

Corneal Transplantation↗
PubMed1990

Binding of basic fibroblast growth factor to normal and neovascularized rabbit cornea.

The labeling pattern of frozen sections of rabbit cornea incubated with radioiodinated basic fibroblast growth factor (bFGF) was investigated in normal corneas and prostaglandin-induced neovascularized corneas by autoradiography followed by image analysis. 125I-bFGF binds to Bowman's, Descemet's, and vascular basement membranes in a dose-dependent manner. The specificity of the binding of bFGF to basement membrane was demonstrated by the following experiments: 1) an excess of unlabeled growth factor displaced the labeling; 2) histones did not modify the labeling; and 3) 2 M NaCl washing and enzymatic treatment with heparitinase prevented binding of labeled growth factor without apparent destruction of the overall structure of the basement membrane. Our results suggest that bFGF binds to the heparan sulfate proteoglycan of basement membranes. Both normal limbal vessels and the newly formed corneal vessels exhibited the same type of labeling but with different intensities, according to the degree of maturation of the new vessels. bFGF binding also is located clearly on the endothelial cells in both types of vessels. This second binding site could correspond to the high affinity receptors on the cell surface and suggests a direct interaction of bFGF with endothelial cells during new vessel formation.

Alprostadil↗
PubMed1990

[Treatment of dry eye by temporary punctum plug. Comparison with a control group].

35 patients with chronic dry eye were treated with punctum plug on one side only. The other side was a control: after simulation dilatation, the patient underwent a simulation insertion. This is an open study in which only the patient ignored the reality of treatment. The study was prospective. 28 females and 7 males were enrolled in this study. The age' average was 53. The follow-up average is 5.3 months. The etiologies were: idiopathic dry eye: 10 cases, Sjögren's syndrome: 11 cases, drug induced dry eye: 6 cases, filamentous keratitis: 4 cases. Other: 4 cases. Enrollment criteria were: functional symptomatology not answering to topical therapy (physiological serum drops) associated with one or more of the following items: positive Rose Bengal staining and/or Schirmer lower than 5 mm in 5 min and/or filamentary keratitis. Subjective improvement is significantly better after closing the two puncta on the same side (77%) than the other side (placebo) (17%) (p less than 0.001). This difference is also demonstrated for the improvement of Rose Bengal staining (p = 0.068) and for Schirmer's test (p = 0.002). These results demonstrated the effectiveness of this therapy versus placebo. Results after closing the 2 puncta on the same side are better than after closing one punctum.

Adolescent↗
PubMed1990

[Treatment of superficial herpes simplex keratitis with vidarabine (Vira A): multicenter study of 100 cases].

The efficacy of 3% Ara-A ophthalmic ointment (Vira A) has been evaluated on 100 epithelial herpetic keratitis; the poor intra-ocular penetration of Ara-A explains the exclusion of stromal keratitis and kerato-unveitis. Patients were treated 5 times a day until complete epithelial healing of ulcers, then twice a day during 7 days. Healing was obtained within 10.6 days for 87% of the patients, who have been treated by Ara-A at first (n = 77) or after failure of IDU or of IDC (n = 23). The healing rate was higher for the 52 first ocular episodes (92%) than for the 48 recurrences (81%); it decreases to 77% for recurrences after failure of IDU or IDC. Geographic ulcers heal in 76% of cases only. Their length has no influence on their healing. The longest healing time, 10.6 days, can be explained by the long period of time before beginning to apply Ara-A, 12.8 days: significative correlation between both periods of time is highlighted and shows the advantage of an early treatment. The need for a local corticotherapy (n = 8) does not hinder healing in 15.5 days. Two weeks after discontinuation of the treatment, 3 patients presented a relapse, sensitive to a 2nd Ara-A course; a maintenance treatment, superior to 7 days, is necessary. Tolerance to Vira A ointment is good. Indications of Ara-A during ocular herpes are superficial keratitis, especially those resistant to IDU or, from experimental data, to ACV, and their prevention by a possible long term treatment.

Adult↗
PubMed1990

[Mathematical model of the rotation of cornea].

The aim of our study is to informatise the procedure, ie, design the computer system and software necessary to automatically define the parameters of our problem. To achieve this, we have used an image analyser which permits us to acquire and digitalise a photograph of the lesioned cornea. Digitalisation of the image allows us to determine the co-ordinates (x, y) of the points which lie on the lesion periphery as well as the co-ordinates of the corneal centre, ie, geometric centre of the cornea. One calculates the centre of trephination and the optimal diameter of trephination as a function of a point situated on the lesion edge.

Cornea↗
PubMed1989

Distribution and spatial geometry of dopamine interplexiform cells in the rat retina: I. Developing retina.

The morphology and distribution of dopaminergic interplexiform cells were analyzed in 9-day-old rat retinas processed as wholemounts for tyrosine hydroxylase immunohistochemistry. The mean number of dopaminergic interplexiform cells was estimated as about half of the total number of dopaminergic neurons in the immature retina, with a higher density in the temporal retina. Four interplexiform cells were individually analyzed and reconstructed with a computer system. Their arborizations could be divided into three different regions based on both their morphological features and their position within the retinal layers: (1) an internal arborization, spreading at the margin between the inner nuclear layer and the inner plexiform layer, composed of long, thick, somatofugal dendrites branching at acute angles, (2) an external arborization in the middle of the inner nuclear layer, formed by short, thin, varicose, recurved, axon-like processes branching at right angles, (3) and one or more scleral process(es), originating either from the cell body or from the internal arborization, running toward the outermost cell row of the INL, some of which reached the outer plexiform layer. Finally, analysis of the arborization network by computer simulations based on the 4 digitalized cells was compared with a nearest-neighbour analysis of cell body distribution. It showed that cell bodies are almost randomly distributed--at least in the inferior retina--but that an adjustment of dendritic growth and orientation probably occurs to ensure a homogeneous coverage of the retina with a constant degree of overlap in the adult. This report represents the first three-dimensional computer reconstruction of chemically identified neurons in the retina.

Animals↗
PubMed1989

Colocalization of fibroblast growth factor binding sites with extracellular matrix components in normal and keratoconus corneas.

Basic and acidic fibroblast growth factor (bFGF, aFGF) binding sites were determined in frozen sections of normal and keratoconus corneas. After incubation with I-125 radiolabelled growth factors, corneal binding sites were revealed by autoradiography. The growth factors were localized mainly to Descemet's membrane and to the epithelial basement membrane. FGF binding sites were generally similar in normal and keratoconus corneas. The binding specificity was demonstrated by competitive inhibition experiments with an excess of unlabelled growth factors. The binding sites were sensitive to pretreatment of the corneal sections with heparitinase. We have attributed FGF's basement membrane affinity to one of its constituents, proteoheparan sulfate. Proteoheparan sulfate, laminin, collagen type IV, and fibronectin were all revealed by immunofluorescent techniques. While keratoconus cornea stroma had less laminin but more fibronectin than normal corneas the main difference lied in type IV collagen which was overexpressed in keratoconus epithelium.

Adult↗
PubMed1986

Mathematical modelling accounting for discrepancies between blood levels and pharmacodynamic effects of a drug. Application to the numerical optimization of tertatolol.

In this paper we propose a non-linear model for explaining the relation between doses, blood levels and pharmacodynamic effects. Several models are examined and a functional relation (without derivatives or integrals) is retained. From there the medical system is optimized by using optimal control methods. In practice, optimal doses and times are numerically determined for the drug tertatolol.

Adult↗
PubMedDate not supplied

Influence of food on the absorption of theophylline administered in the form of sustained release tablet and microgranules.

Two sustained-release formulations of theophylline, tablets (T) and microgranules (MG) forms, were administered in a randomized order to 8 healthy subjects in fasting or with a high-protein test meal (50 per cent). Blood was collected for 32h post-dose. In fasting subjects, absorption of theophylline was significantly faster for T (tmax 5 h) as compared with MG (tmax 8 h, p less than 0.05), but Cmax and AUC were comparable; intersubject variability was higher with T. Administration of a high-protein test meal with T produced a significant decrease of the zero-order absorption rate constant of theophylline (K omicron 37.8 +/- 9.1 mgh-1 after meal versus 58.8 +/- 13 mgh-1 in fasting, p = 0.01), tmax was doubled to 10 h, and Cmax increased by 25 per cent (6.33 +/- 2.16 mgl-1 versus 5.04 +/- 1.28 mgl-1, p less than 0.02); with MG, tmax were the same (8 h), Cmax were not significantly increased (4.79 +/- 0.84 mgl-1 versus 4.55 +/- 0.67 mgl-1), absorption was delayed (lag-time 1.28 +/- 0.58 h) and the absorption was slightly accelerated (K omicron 50.4 +/- 10.4 mgh-1 versus 42.3 +/- 11.9 mgh-1, NS). For each form bioavailability was not significantly modified by food. This study demonstrated that food rich in protein modifies the absorption rate of theophylline in a sustained-release tablet formulation but is without influence in a pH-independent, sustained-release microgranule formulation.

Administration, Oral↗