Biomedical subjects

Tsontcho Ianchulev

Publications and source records attributed to Tsontcho Ianchulev.

5 recordsLinked to original sources

PubMed2006

Role of vascular endothelial growth factor in ocular angiogenesis.

VEGF-A is a critical regulator of ocular angiogenesis and vascular permeability and is involved in the pathogenesis of several ocular diseases involving neovascularization or increased vascular permeability, such as neovascular AMD, diabetic ME, and diabetic retinopathy. Currently available therapies for neovascular AMD, such as laser photocoagulation, PDT with verteporfin, and pegaptanib sodium, slow visual loss but do not improve vision for most patients. In contrast, an emerging anti-VEGF agent, ranibizumab, improved vision in 25% to 34% of treated patients in one clinical trial, rather than slowing visual loss and is the first treatment for neovascular AMD to demonstrate visual improvement in a substantial number of patients. This represents a major advance in the treatment of ocular diseases involving neovascularization or increased vascular permeability and provides hope to patients with these debilitating diseases. Since the submission of this article, ranibizumab was approved by the FDA for the treatment of neovascular AMD.

Animals↗

PubMed2005

Selective laser trabeculoplasty as a replacement for medical therapy in open-angle glaucoma.

PURPOSE: To evaluate selective laser trabeculoplasty (SLT) as a replacement for medical therapy in controlled open-angle glaucoma. DESIGN: Prospective, non-randomized, interventional clinical trial. METHODS: SLT was performed inferiorly in 66 eyes of 66 patients with medically controlled primary open-angle glaucoma (OAG) or exfoliation glaucoma, and no history of glaucoma surgery. The primary outcome was number of medications at 6 and 12 months while maintaining a pre-determined target intraocular pressure (IOP). RESULTS: The mean of the differences in medications from baseline was 2.0 (95% confidence interval = 1.8-2.3) at 6 months, and 1.5 (1.27-1.73) at 12 months (P < .0001). The group mean of medications was 2.8 +/- 1.1 at baseline, 0.7 +/- 0.9 at 6 months, and 1.5 +/- 0.9 at 12 months (P < .0001). Reduction in medications was attained in 64 of 66 eyes (97%) at 6 months, and 52 of 60 (87%) at 12 months. CONCLUSION: SLT enabled a reduction in medicine in controlled OAG over 12 months.

Aged↗

PubMed2005

Intraoperative optical refractive biometry for intraocular lens power estimation without axial length and keratometry measurements.

PURPOSE: To correlate intraoperative aphakic autorefraction to conventional emmetropic intraocular lens (IOL) calculations and derive an empiric predictive model for IOL estimation based on optical refractive biometry without axial length and keratometry measurements. SETTING: Institutional Review Board of the University of Southern California, Los Angeles County General Hospital, Los Angeles, California, USA. METHODS: A pilot group of 22 eyes of 22 patients scheduled for cataract surgery were enrolled in a prospective trial. All patients had a standard preoperative workup with subsequent cataract extraction and IOL implantation according to conventional biometric measurements and IOL calculations. Intraoperative autorefractive retinoscopy was used to obtain aphakic autorefraction and to measure the aphakic spherical equivalent before lens implantation. A linear regression analysis was used to correlate the aphakic spherical equivalent to the final adjusted emmetropic IOL power to empirically derive a refractive formula for IOL calculation (optical refractive biometry method). A second validation series of 16 eyes was used in a head-to-head comparison between the optical refractive biometry and the conventional IOL formulas. A subset of 6 eyes from the validation series were post-refractive cases having subsequent cataract surgery. RESULTS: Intraoperative retinoscopic autorefraction was successfully obtained in all 22 patients in the pilot group and all 16 patients in the validation group. The spherical equivalent of the aphakic autorefraction correlated linearly with the final adjusted emmetropic IOL power (P<.0001, with adjusted r(2)=.9985). The relationship was sustained over an axial length range of 21.43 to 25.25 mm and an IOL power range of 12.0 to 25.5 diopters (D). In a subsequent validation series of 10 standard and 6 post-laser in situ keratomileusis (LASIK) cataract cases, the optical refractive biometry method proved to be a better predictive model for IOL estimation than conventional formulas; 83% of the LASIK eyes and 100% of the normal eyes were within +/-1.0 D of the final IOL power when aphakic autorefraction was used, compared with 67% of LASIK eyes and 100% of the normal eyes, using the conventional methodology. CONCLUSIONS: A new model for IOL power calculation was derived based on an optical refractive methodology that breaks away from the conventional art introduced by Fyodorov in the 1960s. A purely refractive algorithm is used to predict the power of the IOL at the time of surgery without the need for axial length and keratometry measurements. This method bypasses some limitations of conventional biometry and shows promise in the post-refractive cataract cases.

Biometry↗

PubMed2005

Peristat: a computer-based perimetry self-test for cost-effective population screening of glaucoma.

PURPOSE: Peristat is a virtual perimetry system that allows self-testing on any standard computer monitor via Internet connection. The sensitivity and specificity of Peristat to detect visual-field defects were compared to standard Humphrey Visual Field Analyzer data. MATERIALS AND METHODS: In this prospective, comparative observational case series, 58 eyes of 33 patients were examined. Semiquantitative analyses compared Peristat and Humphrey Visual-Field scores. The study evaluated patients with an established glaucoma diagnosis, as well as glaucoma suspects who had undergone comprehensive ophthalmologic examinations including prior office perimetry evaluation (Humphrey Field Analyzer). Inclusion criteria were (1) diagnosis or suspicion of glaucoma, (2) BCVA better than 20/200, (3) reliable performance on prior standardized office perimetry, and (4) CDR greater than 0.5. Computer literacy was not required, and more than 40% of the patients tested were computer illiterate, with no previous computer or Internet experience. A total of 58 eyes of 33 patients were tested with the Humphrey and the Peristat systems: 10 eyes of 5 patients without documented glaucomatous field loss and 48 eyes of 23 patients with mild-to-severe scotomas by standard 24-2 office perimetry. A standard computer setup was used with a 17" monitor, and the Peristat system was enabled through a remote connection with a server. RESULTS: All patients completed the Peristat test without difficulty. Testing time varied between 2 and 5 min, tending to be longer with more severe visual-field defects. Test results were reviewed, in a masked fashion, by two glaucoma specialists and one general ophthalmologist. The Peristat demonstrated a high degree of correlation with the Humphrey system. Among the three reviewers, sensitivity ranged from 80% to 83%. In a second subanalysis in which cases with mild defects were excluded, the Peristat's sensitivity increased to 84%-86% while specificity remained between 94% and 97% for all three reviewers. Patients performed the Peristat test with similar facility to their Humphrey test. Fixation losses and test reliability were comparable for both tests. CONCLUSIONS: Peristat is a reliable self-test perimetry system that demonstrates high clinical utility for the detection of visual-field defects from glaucoma. Peristat could be a valuable public health tool for cost-effective screening of glaucoma.

Algorithms↗

PubMed2003

Optic nerve atrophy in propionic acidemia.

OBJECTIVE: Propionic acidemia is a rare metabolic disorder that is diagnosed in the early neonatal period. The disorder is characterized by life-threatening ketoacidosis, lethargy, failure to thrive, and developmental delay. Herein we report the ocular findings in a prospective series of six patients with propionic acidemia. DESIGN: Prospective case series. PARTICIPANTS: Six children (three male and three female) between the ages of 2 and 10 years with propionic acidemia who were examined at Children's Hospital Los Angeles. METHODS: A complete ophthalmic examination was performed on each of the six children. The examination included visual acuity testing, ocular motility, anterior segment examination, and funduscopic evaluation. Emphasis was placed on the function of the optic nerve and on the appearance of the optic disc, looking for possible atrophic changes. MAIN OUTCOME MEASURES: The clinical appearance of the optic disc and evidence of optic neuropathy. RESULTS: Optic nerve atrophy was present exclusively in all of the male patients in the series; none of the female patients demonstrated any detectable impairment of optic nerve function. The optic nerve atrophy was symmetric and age dependent and varied from moderate to severe. There were no other anterior or posterior segment abnormalities, other than one case of unilateral morning glory syndrome, diagnosed at birth. There was no correlation between metabolic control and the development and progression of optic nerve atrophy. CONCLUSIONS: Males with propionic acidemia have moderate to severe bilateral optic atrophy.

Amino Acid Metabolism, Inborn Errors↗