Paulo Schor

Bio: Paulo Schor is an academic researcher from Federal University of São Paulo. The author has contributed to research in topics: Keratoconus & Corneal topography. The author has an hindex of 26, co-authored 160 publications receiving 1921 citations. Previous affiliations of Paulo Schor include University of São Paulo & Vision Institute.

Shifting trends in in vitro antibiotic susceptibilities for common ocular isolates during a period of 15 years

Abstract: Purpose To assess the in vitro susceptibility of the most common ocular bacterial isolates to several antibiotics and verify changing trends in the antibiotic susceptibility in a 15-year period. Design Experimental study. Methods All cultures positive for Staphylococcus aureus , coagulase-negative Staphylococcus (CNS), Streptococcus sp, and Pseudomonas sp in conjunctival (n = 4,585) and corneal (n = 3,779) samples from patients seen at the Federal University of Sao Paulo from 1985 to 2000 were evaluated. Cultures were performed in liquid and solid media, and susceptibility tests were done to amikacin, gentamicin, neomycin, tobramycin, ciprofloxacin, norfloxacin, ofloxacin, cephalothin, and chloramphenicol. Results Amikacin and neomycin showed an improvement of their sensitivity during the study period (88%–95% and 50%–85%, respectively) for corneal and conjunctival samples. Gentamicin and tobramycin revealed a decrease of sensitivity in time, from 95% to less than 80% in corneal and conjunctival samples. Ciprofloxacin, norfloxacin, and ofloxacin had good sensitivity to all evaluated bacteria, better in conjunctiva (95%) than in cornea (90%). Sensitivity of S. aureus to cephalothin decreased during the study but was still 98% for CNS. Chloramphenicol had good sensitivity to S. aureus (85% in corneal and 92%in conjunctival samples), CNS (87% and 88.5%), and Streptococcus sp (95% and 96%). Conclusions Gentamicin, tobramycin, and cephalothin decreased their in vitro susceptibility to all tested pathogens. The fluoroquinolones remained a good choice in the treatment of ocular infections, with high suscep-tibility to all pathogens tested. Chloramphenicol also revealed an increase in its susceptibility to all bacteria evaluated.

Myopic angle-supported intraocular lenses: two-year follow-up.

Abstract: Objective To evaluate clinical and refractive results of myopic angle-supported intraocular lenses (IOLs). Design Prospective, noncomparative case series. Participants Twenty-one eyes of 12 patients (7 female) with a mean age of 29.5 years and a follow-up of 24 months. The prospective study included highly myopic eyes (more than −11.00 diopters [D]) with spectacle-corrected visual acuity better than 20/200. Methods Twenty-one eyes underwent implantation of a single-piece IOL with Z-shaped haptics for angle support (each haptic with two footplates) and an optical zone of 4.5 mm (NuVita, Bausch & Lomb Surgical, Irvine, CA). The dioptric power of the IOL was calculated considering refraction, keratometry, and anterior chamber depth (specific nomogram), and its diameter was determined by adding 0.5 mm to the corneal diameter. Main outcome measures We evaluated the following clinical and refractive data: visual acuity without and with correction (VAsc and VAcc), spherical equivalent (SE) obtained under cycloplegia, slit-lamp biomicroscopy, keratometry, applanation tonometry, endothelial cell count, ultrasound pachymetry, gonioscopy, indirect ophthalmoscopy, subjective complaints, and descriptions of complications. Results Mean postoperative VAsc was 20/74. Mean preoperative VAcc (20/50) increased to 20/30; 65% gained at least two lines of VAcc, and no eye had a decrease in VAcc. Preoperative SE (−18.95 D) evolved to −2.06 D, stabilizing after one month. Iris retraction (pupil ovalization) more than 0.5 mm was noted in eight eyes (40%). Mean keratometry, corneal astigmatism, and ultrasound pachymetry were stable during the study ( P > 0.01). Significant endothelial cell loss was demonstrated in the second year. Gonioscopy showed 70 (87.5%) footplates ideally positioned with no iris depression. Reports of glare and haloes in dark environment were considered light in 80% and not referred in 20%, and spectacles were used for residual refraction in 75%. Intraocular lens exchange was needed in one eye because of undersizing, and the IOL was removed in one eye because of chronic inflammatory reaction associated with ocular hypertension (this patient was excluded from the statistical analysis). Conclusions This report demonstrates good efficacy for correction of high myopia by the phakic IOL used during the two years of follow-up. Long-term complications (safety) such as iris retraction and endothelial cell loss remain a concern.

Radiobiology of ultrasoft X rays. I. Cultured hamster cells (V79).

Abstract: Ultrasoft X rays (approximately less than keV) provide a useful probe for the study of the physical parameters associated with the induction of biological lesions because the spatial scale of their energy depositions is of nanometer dimensions, comparable to that of critical structures within the cell. We report on cell-killing experiments using cultured hamster cells (V79) exposed to carbon K (0.28 keV), aluminum K (1.5 keV), copper K (8.0 keV), and 250 kVp X rays, under oxic and hypoxic conditions, and as a function of cell-cycle phase. Our principal results are: RBE increases with decreasing X-ray energy; OER decreases with decreasing X-ray energy; and cell-cycle response is similar for all X-ray energies. Our RBE results confirm earlier observations using ultrasoft X rays on mammalian cells. The shapes of fitted curves through the data for each energy are statistically indistinguishable from one another, implying that the enhanced effectiveness is purely dose modifying. The results reported herein generally support the view that single-track effects of radiation are predominantly due to very local energy depositions on the nanometer scale, which are principally responsible for observed radiobiological effects.

A direct method to measure the power of the central cornea after myopic laser in situ keratomileusis.

Abstract: Objective: To measure the corneal power after myopic laser in situ keratomileusis (LASIK). Methods: Six central areas in 6 corneal power maps were studied using the Orbscan II statistical analysis device in 26 eyes that underwent myopic LASIK. Refractive and corneal power changes were compared. Factors related to wrong corneal power measurement were evaluated. Main Outcome Measures: Cycloplegic refraction, refractive change at the corneal plane, and Orbscan II corneal power maps. Results: Preoperatively, only posterior-mean power (P<<.001) and anterior-posterior power ratio (P<<.001) varied according to the size of the analyzed area. Postoperatively, total-optical (P=.03), keratometric-mean (P=.04), total-mean (P<.001), anterior-mean (P=.03), and posterior-mean (P<<.001) powers; and anterior-posterior power ratio (P<<.001) varied according to the area. Postoperatively, the difference between keratometric-mean and total-mean powers became larger (P<.001), and the anterior-posterior power ratio was reduced (P<<.001). A posterior-mean power change occurred (P=.04). Refractive change after myopic LASIK was best estimated by 2-mm total-mean power (mean±SD difference, 0.07±0.62 diopters [D]; P=.55) and 4-mm total-optical power (mean±SD difference, -0.08±0.53 D; P=.37). Conclusions: Total corneal power is more positive and refractive change is underestimated when deduced from the anterior surface radius and keratometric refractive index. The anterior-posterior power ratio is not a fixed value. The best area to estimate the refractive change depends on the method used to obtain the power in diopters. Refractive change tended to be underestimated in larger areas and higher preoperative myopia. Orbscan II total-mean and total-optical power maps accurately assess the corneal power after myopic LASIK independent of preoperative data or correcting factors, and should improve intraocular lens calculation.

Limbal relaxing incisions to correct corneal astigmatism during phacoemulsification.

Abstract: PURPOSE To evaluate the safety and efficacy of limbal relaxing incisions for the correction of corneal astigmatism during phacoemulsification. METHODS Fifty eyes of 37 patients (mean age 66.5 years, range: 45 to 80 years) with cataract and coexisting topographic astigmatism were included in the study. Eyes were randomly divided into two groups: eyes that underwent cataract surgery with limbal relaxing incisions (cataract LRI group) and eyes that underwent cataract surgery only (control group). All limbal relaxing incisions were performed during phacoemulsification. Best spectacle-corrected visual acuity (BSCVA), uncorrected visual acuity (UCVA), and corneal topography were recorded preoperatively and 1, 3, and 6 months postoperatively. RESULTS A statistically significant improvement in BSCVA was seen in the cataract LRI eyes from 0.9 +/- 0.7 preoperatively to 0.1 +/- 0.1 at 1, 3, and 6 months postoperatively (P < .01). A statistically significant improvement in BSCVA was seen in control eyes from 0.8 +/- 0.6 before surgery to 0.2 +/- 0.2 at 1, 3, and 6 months after surgery (P < .01). No difference in postoperative BSCVA was noted between the groups. A statistically significant reduction in the mean topographic astigmatism was seen in the cataract LRI eyes from 1.93 +/- 0.58 diopters (D) preoperatively to 1.02 +/- 0.60 D 6 months postoperatively (P < .05). The control eyes did not show a statistically significant change in topographic astigmatism. CONCLUSIONS Limbal relaxing incisions performed during phacoemulsification surgery appear to be a safe, effective, and stable procedure to reduce pre-existing corneal astigmatism.

Image understanding for iris biometrics: A survey

Abstract: This survey covers the historical development and current state of the art in image understanding for iris biometrics. Most research publications can be categorized as making their primary contribution to one of the four major modules in iris biometrics: image acquisition, iris segmentation, texture analysis and matching of texture representations. Other important research includes experimental evaluations, image databases, applications and systems, and medical conditions that may affect the iris. We also suggest a short list of recommended readings for someone new to the field to quickly grasp the big picture of iris biometrics.

Big-bubble technique to bare Descemet's membrane in anterior lamellar keratoplasty.

Abstract: We describe a lamellar keratoplasty technique to bare Descemet's membrane in which air is injected to detach the central Descemet's. After a partial-thickness corneal trephination is performed, a disposable needle is inserted, deeply and bevel down, into the paracentral corneal stroma and air is injected. In most cases, this forms a large air bubble between Descemet's membrane and the corneal stroma. After anterior lamellar keratectomy is performed, a small opening is made in the air bubble and the remaining stromal layers are lifted with an iris spatula, severed with a blade, and excised with scissors. This technique is faster, safer, and easier to perform than previous methods.

Global consensus on keratoconus and ectatic diseases.

Abstract: Background Despite extensive knowledge regarding the diagnosis and management of keratoconus and ectatic corneal diseases, many controversies still exist. For that reason, there is a need for current guidelines for the diagnosis and management of these conditions. Purpose This project aimed to reach consensus of ophthalmology experts from around the world regarding keratoconus and ectatic diseases, focusing on their definition, concepts, clinical management, and surgical treatments. Methods The Delphi method was followed with 3 questionnaire rounds and was complemented with a face-to-face meeting. Thirty-six panelists were involved and allocated to 1 of 3 panels: definition/diagnosis, nonsurgical management, or surgical treatment. The level of agreement considered for consensus was two thirds. Results Numerous agreements were generated in definitions, methods of diagnosing, and management of keratoconus and other ectatic diseases. Nonsurgical and surgical treatments for these conditions, including the use of corneal cross-linking and corneal transplantations, were presented in a stepwise approach. A flowchart describing a logical management sequence for keratoconus was created. Conclusions This project resulted in definitions, statements, and recommendations for the diagnosis and management of keratoconus and other ectatic diseases. It also provides an insight into the current worldwide treatment of these conditions.

Soft X-ray microscopes and their biological applications

Abstract: In this review we propose to address the question: for the life-science researcher, what does X-ray microscopy have to offer that is not otherwise easily available?We will see that the answer depends on a combination of resolution, penetrating power, analytical sensitivity, compatibility with wet specimens, and the ease of image interpretation.

The computer program

Abstract: A computer program is a series of coded instructions for the computer to obey and represent a method of processing data. Programs can't be written in English. They must first be written using a special language called a programming language. A PROGRAMMING LANGUAGE (e.g. BASIC, PASCAL, and C+) consists of a set of codes and rules which can be used to construct commands for the computer. These commands are read and translated into electronic pulses needed to make the computer work. Programs are written by programmers. A computer language is a set of instructions used for writing computer programs. There are THREE (3) levels of languages: 1. MACHINE LANGUAGE – this was the first language available for programming. It varies from one computer to another, but the basic principles are the same. MACHINE LANGUAGE PROGRAMS are written using a series of 0's and 1's i.e. using a BINARY SYSTEM. All programs written today must be translated into machine language before they can be executed (used) by the computer. EXAMPLE: 110110001 2. ASSEMBLY LANGUAGE / LOW LEVEL LANGUAGE – these were developed to replace the 0's and 1's of machine language with symbols that are easier to understand and remember. Like with machine language, Assembly language varies form one make of computer to another so that a program written in one assembly language will not run on another make of computer. EXAMPLE: LDA 300 ADD 400 STA 500 3. HIGH LEVEL LANGUAGE – these differ from low level languages in that they require less coding detail and make programs easier to write. High level languages are designed for the solution of problems in one ore more areas of the application and are commonly described as application-oriented or problem-oriented languages. High level languages are not machine dependant. Programs written in a high level language must be translated to a form which can be accepted by that computer, i.e.