[Show abstract][Hide abstract] 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.
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).
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.
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 08/2014;
[Show abstract][Hide abstract] 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.
[Show abstract][Hide abstract] ABSTRACT: Purpose: To assess the visual performance of a new multifocal intraocular lens design by means of a vision
Methods: We measured and compared the visual performance (VP) of a new multifocal intraocular lens
(MIOL) design (NDIOL, OPHTEC prototype, Add=2D) a monofocal IOL (monIOL, used as a reference) and a
commercial MIOL (MPlus, Oculentis® Add=+3D). To assess VP a vision simulator (VirtIOL, 101Lens S.L.U.)
that projects the IOL in the pupil of the patients eye was used. VirtIOL allowed us to simulate vision through
IOLs before surgery. LogMAR visual acuity (VA) and perception of halos in a throughfocus scanning from +1D
to -4D, in 0.5D steps was tested using a pupil diameter of 4mm. The effect of IOL orientation error (3 positions
with a change of 120 deg between them) and IOL positioning error (±0.5mm in both x and y axis) was also
tested. All measurements were performed by the same operator and the same well trained observer in order
to maintain the same criterion. Measurements were repeated 3 times showing similar results
Results: In far vision (FV) the best VA was obtained for the monIOL(-0.2), followed by the Mplus(-0.1) and the
NDIOL lens(0.0). In near vision (NV), the higher VA was obtained with the NDIOL(0.0) followed by Mplus(0.1),
and the monIOL(0.4). No differences were found in the perception of halos between both MIOL lenses. The
throughfocus scanning showed a bifocal lens behavior for the Mplus, this is, an accommodative curve with two
well identified peaks of good VA in FV and NV and a VA decrease in intermediate distance(0.2). The NDIOL
lens showed a nearly constant VA(0.0) for FV, intermediate and NV. The monIOL and NDIOL VA were
unaffected by orientation, while Mplus VA was dependent on it. Positioning errors had no effect on the VA of
the IOLs, except in Mplus when with a decentration of 0.5mm it had nearly a monofocal behavior due to the
pupil is mainly covered by the FV zone of the lens
Conclusions: VirtIOL allows assessing VP of IOL before surgery. The two MIOL lens analyzed showed a
good VA performance for FV and NV. During the throughfocus scanning NDIOL lens had nearly constant VA
values, while Mplus showed a bifocal lens behavior. NDIOL VA were unaffected by orientation, while Mplus VA
was dependent on it. Mplus is more sensible to positioning errors due to pupil can be mainly covered by the
FV. Further work with NDIOL will be developed to improve the VA values for FV
Association for Research in Vision and Ophthalmology (ARVO); 05/2014
[Show abstract][Hide abstract] 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
[Show abstract][Hide abstract] 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.
[Show abstract][Hide abstract] 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. · 1.15 Impact Factor
[Show abstract][Hide abstract] 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
[Show abstract][Hide abstract] 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. · 0.50 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In our aim of measuring accommodative response with a double-pass system, we developed a method based on maximizing the retinal image quality. After confirming the suitability of the double-pass technique for measuring the accommodative response, an extended group of patients with a wide age range was measured.
6th European Meeting on Visual and Physiological Optics; 08/2012
[Show abstract][Hide abstract] 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
[Show abstract][Hide abstract] 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