Jaume Pujol

Polytechnic University of Catalonia, Barcino, Catalonia, Spain

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Publications (62)68.09 Total impact

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    ABSTRACT: The recent use of multispectral systems as a noncontact method for analysis of artworks has already shown promising results. This study explains the application of a novel portable multispectral system based on light-emitting diodes (LEDs) for artwork imaging. This method provides spectral information in a spectral range from 370 to 1630 nm with a 25 cm × 25 cm field of view by using two different image sensors in synchrony with 23 bands of irradiation. The spectral information for each point is estimated and validated using the pseudo-inverse and spline interpolation methods for spectral estimation and three different evaluation metrics. The results of the metrics obtained with both estimation methods show a general good performance of the system over the whole spectral range. The experiments also showed that the selection of the training set for the pseudo-inverse estimation has a great influence in its performance, and thus, it defines whether or not the pseudo-inverse outperforms the spline interpolation method. The system is applied in situ to the study of Catalan art masterpieces, and the results demonstrate the potential of a cost-effective and versatile system using various off-the-shelf elements to reconstruct color information and to reveal features not previously identified. © 2014 Wiley Periodicals, Inc. Col Res Appl, 2014
    Color Research & Application 08/2014; · 1.01 Impact Factor
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    ABSTRACT: To expand and investigate the potential of spectral imaging, we developed a portable multispectral system using light-emitting diodes. This system recovers spectral information from the UV to the near IR over a large area using two different image sensors synchronized with 23 bands of illumination. The system was assessed for spectral reconstruction through simulations and experimental measurements by means of two methods of spectral reconstruction and three different evaluation metrics. The results over a Macbeth ColorChecker chart and other samples, including pigments usually employed in art paintings, are compared and discussed. The portable multispectral system using LEDs constitutes a cost-effective and versatile method for spectral imaging.
    Applied Optics 05/2014; 53(14):3131-3141. · 1.69 Impact Factor
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    ABSTRACT: Abstract Purpose: The aim of this article is to propose a quantitative methodology for determining a criterion to discriminate the nonsurgical nuclear cataract from the surgical one taking into account objective measures of intraocular scattering in patients with good visual acuity (>0.6). Methods: Two groups of subjects were taken into account: a control group and a group with nuclear cataracts. At a first stage, eyes belonging to the cataract group were classified into "nonsurgical" and "surgical" cataracts by ophthalmologists at their clinical settings. At a second stage a double-pass instrument was also used to determine the objective scatter index (OSI) at the laboratory. Receiver operating characteristic (ROC) curves were used to analyze OSI values to determine a value able to separate between nonsurgical and surgical cataracts. Results: We obtained statistically significant differences among the control and both nuclear cataract groups (p < 0.05). ROC curves determined an OSI criterion level (of 2.1) to suggest surgery in nuclear cataracts with an area under curve of 0.83, i.e. with 80% of sensitivity and 80% of specificity. Conclusions: ROC analysis allows separating both groups of nuclear cataract, and we determined a value of OSI in nuclear cataract quantification for surgery.
    Current eye research 04/2014; · 1.51 Impact Factor
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    ABSTRACT: Abstract: Purpose: To objectively estimate the intraocular scattering by means of a new index (Frecuency Scattering Index, FSI), which is computed by using the whole double-pass (DP) image. The index proposed takes into account the maximum variation of the slope of the modulation transfer function (MTF) obtained from the DP image recorded. Methods: We selected a group of 50 patients with different grades of nuclear cataracts, including from early to moderate stages according to the LOCS III classification system (from NO1 to NO3). A control group of 10 young normal eyes was also evaluated with the same procedure. DP images (size: 72 arc min) were obtained using a clinical instrument (OQAS, Visiometrics SL, Spain). From those images the FSI was computed by means of the corresponding MTF images and the analysis of their maximum slope. The FSI index was then compared with the OSI values (Objective Scatter Index) in terms of correlation. The OSI was provided by the OQAS instrument (Artal et al Plos 2011). The influence of low-order aberrations on the FSI was also analyzed by performing measurements on 8 healthy young subjects with induced defocus from -1.50 to +1.50 D in 0.25 D steps. These results were compared with those obtained by using the OSI parameter. Results: For the control group and patients with different cataract grades, a statistically significant correlation (r=0.726, p<0.001) was found between the FSI and LOCS III classification. Mean FSI (±SD) was of 0.49±0.12 for the control group; 1.86±1.02 for the NO1 group; 2.47±1.12 for the NO2 group; and 3.35±1.67 for the NO3 group. FSI and OSI values also showed a good and significant correlation (r =0.783, p<0.001). Furthermore, none of the 8 subjects with induced defocus showed a variation in the FSI index higher than 0.7 within the tested range. In the case of the OSI, the range within which that was accomplished was between -1.50 and +1.00 D (Martinez-Roda et al. Clin Exp Optom 2011). Conclusions: In this study a new index (FSI) to objectively estimate intraocular scattering by analyzing the slope variation in the MTF computed from the DP images is proposed. This index is computed using the complete DP image recorded and performs very well in discriminating different grades of nuclear cataracts. It has good correlations with the LOCS III clinical classification system and with the OSI parameter. FSI shows a high robustness regarding the induced defocus. Therefore, the FSI index could be a complementary and powerful tool in the objective assessment of intraocular scattering and thus for the improvement of cataract detection and surgery scheduling.
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    ABSTRACT: Purpose To evaluate the impact of contact lens (CL)-induced corneal swelling on the optical quality of the eye by means of the double-pass technique. Methods Measurements of 6 healthy subjects were obtained in 5 visits over 1 week, at baseline and after sleeping with 4 different CLs of +0.50 D, +2.00 D, +5.00 D and +8.00 D (Acuvue2), randomly fitted on 4 different days. The control eye wore no CL. Corneal pachymetry and optical quality of the eye (OQAS, Visiometrics) were measured once at baseline and at three interval times in the follow-up visits: immediately after CL removal, and 1 and 2 h after CL removal. Optical quality was evaluated by means of the Strehl ratio and OQAS values at 100%, 20% and 9% contrasts. Intraocular scattering was evaluated with the objective scatter index (OSI). Results Mean overnight swelling was 5.98 ± 4.29% in CL-eyes versus 0.30 ± 0.78% in control eyes (p < 0.01). Corneal swelling was maximal immediately after CL removal and decreased with time (p < 0.01). A significant worsening in all optical quality parameters and a significant increase of the OSI were found in eyes with corneal swelling (p < 0.05). Two hours after CL removal there were no statistically significant differences (p > 0.05) between CL-eyes and control eyes in any of the measured parameters. Conclusions Corneal swelling has a significant impact on the optical quality of the eye and on intraocular scattering as assessed with the double-pass technique.
    Contact lens & anterior eye: the journal of the British Contact Lens Association 01/2014;
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    ABSTRACT: This study analyzes the repeatability, reproducibility and accuracy of a new hyperspectral system based on a pushbroom sensor as a means of measuring spectral features and color of materials and objects. The hyperspectral system consisted of a CCD camera, a spectrograph and an objective lens. An additional linear moving system allowed the mechanical scanning of the complete scene. A uniform overhead luminaire with daylight configuration was used to irradiate the scene using d:45 geometry. We followed the guidelines of the ASTM E2214-08 Standard Practice for Specifying and Verifying the Performance of Color-Measuring Instruments that define the standards and latest multidimensional procedures. The results obtained are analyzed in-depth and compared to those recently reported by other authors for spectrophotometers and multispectral systems. It can be concluded that hyperspectral systems are reliable and can be used in the industry to perform spectral and color readings with a high spatial resolution. © 2013 Wiley Periodicals, Inc. Col Res Appl, 2013
    Color Research & Application 10/2013; · 1.01 Impact Factor
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    ABSTRACT: In this study we show a novel double-pass configuration to correct the spherical refractive error by means of an electro-optical liquid lens.The proposed method enables spherical correction in the -12 D to +7 D range without movable parts using an electro-optical liquid lens.We have measured the optical performance of the spherical corrector in terms of power, pupil size and optical quality verifying that it fitsthe requirements to be applied to a double-pass system. We have also evaluated the performance of the proposed method in patients bycomparison with a conventional double-pass system using a Badal optometer.
    Journal of the European Optical Society Rapid Publications 09/2013; 8(2013):13062. · 0.93 Impact Factor
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    ABSTRACT: PURPOSE: To measure the accommodative response in a wide age range population using the retinal image quality assessments provided by a double-pass system. METHODS: The accommodative response was measured using a custom-built double-pass setup in 84 patients from 15 to 55 years of age. Patients were classified in four groups (A: 15-25 year old; B: 26-35; C: 36-45; D: 46-55). Accommodation was stimulated from 0 to 5 dioptres (D) with the push up method using an open field fixation test. The total accommodative response in the stimulated range, the accommodative stimulus-response curve, the slope and the progression of optical quality with accommodation were measured. RESULTS: The total accommodation obtained in groups A and B was high, with a mean value of 4 D or higher, whereas values in older individuals were significantly lower. The accommodative stimulus-response curve and the slope were also high with a sudden decrease in patients over 35 years of age. The optical quality of the eye during accommodation did not change significantly. CONCLUSIONS: Participants aged 15-35 years showed a good accommodative response. Thereafter, a significant decrease of the response in the total accommodation, stimulus response curve and slope was observed. The younger groups showed a larger accommodative response than previously published.
    Ophthalmic and Physiological Optics 03/2013; · 1.74 Impact Factor
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    ABSTRACT: To evaluate the accuracy of spherical equivalent (SE) estimates of a double-pass system and to compare it with retinoscopy, subjective refraction and a table-mounted autorefractor. Non-cycloplegic refraction was performed on 125 eyes of 65 healthy adults (age 23.5±3.0 years) from October 2010 to January 2011 using retinoscopy, subjective refraction, autorefraction (Auto kerato-refractometer TOPCON KR-8100, Japan) and a double-pass system (Optical Quality Analysis System, OQAS, Visiometrics S.L., Spain). Nine consecutive measurements with the double-pass system were performed on a subgroup of 22 eyes to assess repeatability. To evaluate the trueness of the OQAS instrument, the SE laboratory bias between the double-pass system and the other techniques was calculated. The SE mean coefficient of repeatability obtained was 0.22D. Significant correlations could be established between the OQAS and the SE obtained with retinoscopy (r=0.956, P<0.001), subjective refraction (r=0.955, P<0.001) and autorefraction (r=0.957, P<0.001). The differences in SE between the double-pass system and the other techniques were significant (P<0.001), but lacked clinical relevance except for retinoscopy; Retinoscopy gave more hyperopic values than the double-pass system -0.51±0.50D as well as the subjective refraction -0.23±0.50D; More myopic values were achieved by means of autorefraction 0.24±0.49D. The double-pass system provides accurate and reliable estimates of the SE that can be used for clinical studies. This technique can determine the correct focus position to assess the ocular optical quality. However, it has a relatively small measuring range in comparison with autorefractors (-8.00 to +5.00D), and requires prior information on the refractive state of the patient.
    International Journal of Ophthalmology 01/2013; 6(5):618-25. · 0.12 Impact Factor
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    ABSTRACT: In this study we evaluate the intraocular scattering in eyes with nuclear and cortical cataracts by means of several techniques, including the LOCS III classification system, the C-Quant instrument and the OSI parameter. The results show that a correlation exists between the different tested techniques.
    EOS Topical Meeting: 6th European Meeting on Visual and Physiological Optics (EMVPO); 08/2012
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    ABSTRACT: To evaluate objectively intraocular scattering in eyes with nuclear, cortical and posterior subcapsular cataracts by means of an objective scatter index (OSI) obtained from double-pass images. To compare the results with those obtained using clinical conventional procedures. In this prospective, observational, cross-sectional, non-consecutive case series study, 188 eyes with cataracts of 136 patients were analysed (123 eyes had nuclear, 41 eyes had cortical and 24 eyes had posterior subcapsular cataracts). The control group consisted of 117 eyes of 68 healthy patients. Patient examination included subjective refraction, best spectacle-corrected visual acuity (BSCVA), cataract grade using the lens opacities classification system III (LOCS III) and OSI. We found a decrease in the BSCVA and an increase in the OSI with increasing cataract grade. Statistically significant differences were observed when the OSI of eyes without cataracts and those with different LOCS III were compared. The comparison between the OSI and LOCS III reported good percentages of agreement regarding the number of eyes classified in equivalent levels: 72.4% (nuclear cataracts), 86.6% (cortical cataracts) and 84.3% (posterior subcapsular cataracts). A non-linear regression model was applied between OSI and BSCVA, which resulted in the following multiple correlation coefficients: r=0.878 (nuclear), r=0.843 (cortical) and r=0.844 (posterior subcapsular). The results of the study showed that OSI is a useful parameter for evaluating large amounts of intraocular scattering that can be used, in combination with other conventional procedures, as a valuable tool in clinical practice to grade cataracts objectively.
    The British journal of ophthalmology 07/2012; 96(9):1204-10. · 2.92 Impact Factor
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    ABSTRACT: In this study we present the comparison of the performance of two systems to measure intraocular scattering. Measurements were made by using a psychophysical system based on a brightness comparison method that provides a glare index and a physical system based on the double-pass technique, which gives an objective scatter index by measuring the optical quality of the eye. Three external diffuser filters that simulated different grades of intraocular scattering were used in subjects with normal vision. The two measured indexes showed a graded rise with increasing level of scattering. The discrimination ability obtained for both systems showed that they were able to distinguish among conditions ranging from normal to early cataracts.
    Journal of the Optical Society of America A 07/2012; 29(7):1293-9. · 1.67 Impact Factor
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    ABSTRACT: The current study aims at analysing the suitability of the double-pass technique in measuring the accommodative response. A custom-built setup which allowed simultaneous double-pass and Hartmann-Shack measurements was used. Several metrics to assess the accommodative response were tested and compared. In order to validate double-pass based measurements, the accommodative response was measured in 10 young adults under monocular viewing conditions with an open field fixation test. Accommodation was stimulated with the push up method in the 0-5diopters (D) range with a 1-D step. We found no significant differences among accommodative response measurements obtained with the several metrics compared in the double-pass and the Hartmann-Shack technique. In addition, differences between the double-pass and Hartmann-Shack techniques were not statistically significant. However, we obtained slightly higher values in the measured accommodative response with the double-pass system than those usually reported by other authors. The double-pass technique takes into account all factors influencing retinal image quality. Consequently, we consider this technique as a potential powerful candidate for the analysis of accommodation.
    Vision research 04/2012; 62:26-34. · 2.29 Impact Factor
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    ABSTRACT: PurposeTo objectively estimate the intraocular scattering by means of a new index (Frecuency Scattering Index, FSI), which is computed by using the whole double-pass (DP) image. The index proposed takes into account the maximum variation of the slope of the modulation transfer function (MTF) obtained from the DP image recorded. MethodsWe selected a group of 50 patients with different grades of nuclear cataracts, including from early to moderate stages according to the LOCS III classification system (from NO1 to NO3). A control group of 10 young normal eyes was also evaluated with the same procedure. DP images (size: 72 arc min) were obtained using a clinical instrument (OQAS, Visiometrics SL, Spain). From those images the FSI was computed by means of the corresponding MTF images and the analysis of their maximum slope. The FSI index was then compared with the OSI values (Objective Scatter Index) in terms of correlation. The OSI was provided by the OQAS instrument (Artal et al Plos 2011). The influence
    ARVO Meeting Abstracts. 03/2012; 53(6):3053.
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    ABSTRACT: PurposeTo assess ocular optical quality (OQ) and intraocular scattering (IS) from double-pass (DP) images in patients with amblyopia. MethodsWe considered a group of 30 eyes of 30 subjects with treated amblyopia and a control group of 43 eyes of 27 healthy young subjects. Mean ages ({+/-} SD [range]) were of 9.90 {+/-} 3.60 (8.62 to 10.93 yr.) for the amblyopic group and 7.13 {+/-} 2.56 (5.71 to 8.55 yr.) for the control group. DP images with a pupil diameter of 4 mm were taken using a clinical instrument (OQAS, Visiometrics SL, Spain) (Guell et al. J Cataract Refr Surg 2004), and several parameters related to the OQ and IS of the eye (Strehl ratio, OQAS values [OV] at contrasts 100%, 20% and 9%, and Objective Scatter Index [OSI]) (Martinez-Roda et al. Clin Exp Optom 2011; Artal et al. Plos 2011) were computed. Moreover, we measured the best spectacle-corrected visual acuity (BSCVA) with a standard logMAR chart. ResultsLogMAR BSCVA for amblyopic eyes was 0.12 {+/-} 0.11 and for control group -0.05 {+/-
    ARVO Meeting Abstracts. 03/2012; 53(6):3063.
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    02/2012; , ISBN: 978-953-51-0230-4
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    ABSTRACT: To use a double-pass system to compare the optical quality after photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) for mild to moderate myopia. Universitat Politècnica de Catalunya, Terrassa, Barcelona Institute of Ocular Microsurgery, Barcelona, Spain. Comparative case series. Optical quality was assessed with a clinical double-pass system preoperatively and 3 months after PRK or LASIK. The modulation transfer function (MTF), retinal image quality parameters (MTF cutoff frequency, Strehl ratio), and intraocular scattering (objective scatter index [OSI]) were calculated. This study evaluated 34 eyes that had PRK and 55 eyes that had LASIK. Both PRK and LASIK had a statistically significant impact on retinal image quality, although no significant differences between the techniques were observed. The MTF at 30 cycles per degree decreased by a factor of 1.50 in the PRK group and by a factor of 1.32 in the LASIK group. The MTF cutoff frequency decreased by a factor of 1.04 in the PRK group and by a factor of 1.06 in the LASIK group. The Strehl ratio decreased by a factor of 1.10 and 1.07, respectively. Photorefractive keratectomy and LASIK increased the objective scatter index by factors of 1.48 and 1.57, respectively. Significant correlations between the preoperative refraction and the OSI were found. Retinal image quality was similarly reduced with PRK and LASIK, with no significant differences between the 2 methods. Some PRK patients had a residual refractive error that might have been related to corneal-wound healing still present 3 months postoperatively.
    Journal of Cataract and Refractive Surgery 01/2012; 38(1):16-27. · 2.75 Impact Factor
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    ABSTRACT: To evaluate and compare the tear-film dynamics in normal eyes and in eyes with mild dry-eye symptoms using a new noninvasive optical method based on a double-pass instrument. Hospital Universitario Virgen de la Arrixaca, Murcia, Spain. Evaluation of diagnostic test or technology. Dynamic recording of double-pass retinal images during unforced tear-film breakup was performed in eyes with mild dry-eye symptoms (study group) and in an asymptomatic control group. Series of consecutive retinal images were recorded every 0.5 seconds while the patient avoided blinking. Measurements were performed under low-light conditions to naturally increase pupil diameter and maximize the method's sensitivity. Additional clinical tests were performed for comparison and included tear breakup time (TBUT), Schirmer I tests, and a normalized questionnaire (McMonnies). From the retinal images, a quality metric, the intensity distribution index, was calculated. An objective TBUT value was estimated in each eye when the intensity distribution index surpassed a defined threshold value compared with the initial baseline. The study group comprised 20 eyes and the control group, 18 eyes. Symptomatic dry eyes had a typical exponential increase in the intensity distribution index with time. The objective TBUT values in the study group were comparable to the clinical TBUT estimates. The new objective optical method to evaluate the quality and stability of the tear film was sensitive in detecting mild symptoms of dry eye and differentiating from normal cases. The procedure may allow early detection and follow-up of patients' tear film-related complaints.
    Journal of Cataract and Refractive Surgery 08/2011; 37(8):1481-7. · 2.75 Impact Factor
  • Meritxell Vilaseca, Jaume Pujol
    Clinical and Experimental Optometry 07/2011; 94(4):393-5. · 0.92 Impact Factor