Optical Technologies for the Improvement of Skin Cancer Diagnosis: A Review.

The worldwide incidence of skin cancer has risen rapidly in the last decades, becoming one in three cancers nowadays. Currently, a person has a 4% chance of developing melanoma, the most aggressive form of skin cancer, which causes the greatest number of deaths. In the context of increasing incidence and mortality, skin cancer bears a heavy health and economic burden. Nevertheless, the 5-year survival rate for people with skin cancer significantly improves if the disease is detected and treated early. Accordingly, large research efforts have been devoted to achieve early detection and better understanding of the disease, with the aim of reversing the progressive trend of rising incidence and mortality, especially regarding melanoma. This paper reviews a variety of the optical modalities that have been used in the last years in order to improve non-invasive diagnosis of skin cancer, including confocal microscopy, multispectral imaging, three-dimensional topography, optical coherence tomography, polarimetry, self-mixing interferometry, and machine learning algorithms. The basics of each of these technologies together with the most relevant achievements obtained are described, as well as some of the obstacles still to be resolved and milestones to be met.

Visible and Extended Near-Infrared Multispectral Imaging for Skin Cancer Diagnosis.

With the goal of diagnosing skin cancer in an early and noninvasive way, an extended near infrared multispectral imaging system based on an InGaAs sensor with sensitivity from 995 nm to 1613 nm was built to evaluate deeper skin layers thanks to the higher penetration of photons at these wavelengths. The outcomes of this device were combined with those of a previously developed multispectral system that works in the visible and near infrared range (414 nm⁻995 nm). Both provide spectral and spatial information from skin lesions. A classification method to discriminate between melanomas and nevi was developed based on the analysis of first-order statistics descriptors, principal component analysis, and support vector machine tools. The system provided a sensitivity of 78.6% and a specificity of 84.6%, the latter one being improved with respect to that offered by silicon sensors.

Multispectral imaging system based on light-emitting diodes for the detection of melanomas and basal cell carcinomas: a pilot study (erratum).

This erratum corrects the error of an omitted author in doi: http://dx.doi.org/10.1117/1.JBO.22.6.065006

Multispectral imaging system based on light-emitting diodes for the detection of melanomas and basal cell carcinomas: a pilot study.

This article proposes a multispectral system that uses the analysis of the spatial distribution of color and spectral features to improve the detection of skin cancer lesions, specifically melanomas and basal cell carcinomas. The system consists of a digital camera and light-emitting diodes of eight different wavelengths (414 to 995 nm). The parameters based on spectral features of the lesions such as reflectance and color, as well as others empirically computed using reflectance values, were calculated pixel-by-pixel from the images obtained. Statistical descriptors were calculated for every segmented lesion [mean ( x ˜ ), standard deviation ( σ ), minimum, and maximum]; descriptors based on the first-order statistics of the histogram [entropy ( E p ), energy ( E n ), and third central moment ( µ 3 )] were also obtained. The study analyzed 429 pigmented and nonpigmented lesions: 290 nevi and 139 malignant (95 melanomas and 44 basal cell carcinomas), which were split into training and validation sets. Fifteen parameters were found to provide the best sensitivity (87.2% melanomas and 100% basal cell carcinomas) and specificity (54.5%). The results suggest that the extraction of textural information can contribute to the diagnosis of melanomas and basal cell carcinomas as a supporting tool to dermoscopy and confocal microscopy.

Double-pass technique and compensation-comparison method in eyes with cataract.

PURPOSE: To clinically assess the objective scatter index (OSI) obtained from double-pass images and the log(s) parameter measured with the direct compensation-comparison psychophysical technique in eyes with cataract. SETTING: Ophthalmology Service, Terrassa Hospital, Barcelona, Spain. DESIGN: Prospective observational case series. METHODS: The analysis comprised eyes diagnosed with nuclear, cortical, or posterior subcapsular cataracts and healthy eyes (control group). Patient examinations included assessment of the manifest subjective refraction, corrected distance visual acuity, contrast sensitivity, and cataract grade using the Lens Opacities Classification System III (LOCS III) score. The protocol also included the straylight (log[s]) measured by the C-Quant device, measurement of the objective optical quality (Strehl ratio and modulation transfer function cutoff frequency), and the OSI (HD Analyzer). RESULTS: Significant correlations with LOCS III classification were found in terms of log(s) and OSI, although they were slightly stronger with OSI for all cataract types, which could be attributable to higher-order aberrations. The OSI and log(s) shared approximately 44% of the scattering estimation and to coincide on the visual function decline with scattering for the 3 cataract types evaluated. Limits to discriminate between healthy and cataractous eyes and sensitivity and specificity values were 1.15 (sensitivity 91%, specificity 100%) for log(s) and 1.18 (sensitivity 89%, specificity 100%) for OSI (P < .05). CONCLUSIONS: Both instruments provide complementary information to diagnose cataracts and follow patients. Although backscattered light from deeper retinal layers can have an effect on OSI, the double-pass image provides information to grade different types of cataract when assessing cataractous eyes for treatment. FINANCIAL DISCLOSURE: None of the authors has a financial or proprietary interest in any material or method mentioned.

Repeatability of aberrometric measurements with a new instrument for vision analysis based on adaptive optics.

PURPOSE: To evaluate intersession and intrasession repeatability of aberration data obtained with a new visual simulator based on adaptive optics, which includes a Hartmann-Shack aberrometer (Adaptive Optics Vision Analyzer; Voptica S.L., Murcia, Spain). METHODS: Thirty-one healthy right eyes were included in the study. To evaluate intrasession repeatability, three consecutive measurements without repositioning the patient or realigning the eye were obtained. Intersession repeatability was evaluated in three sessions. Aberrometric data computed from the second to the fifth order for a 4-mm pupil were used. Statistical analysis included the repeated measures analysis of variance (or the Wilcoxon signed rank test), the coefficient of repeatability, the Bland-Altman method, and the intraclass correlation coefficient. RESULTS: No significant differences in the intrasession and intersession repeatability analysis for any of the parameters (P > .05) were found, suggesting a consistent variability of the instrument over time. Similar coefficient of repeatability values were obtained in the three sessions. The Bland-Altman analysis confirmed differences close to zero and the variations were independent of the mean within and between sessions. The intersession intraclass correlation coefficient values were generally above 0.75, suggesting moderate to high repeatability. However, some exceptions were found in the intrasession analysis. CONCLUSIONS: The findings suggest that the new instrument provides consistent and repeatable aberrometric data. It is therefore a suitable tool to perform consistent and repeatable visual simulations.

Discrimination between surgical and nonsurgical nuclear cataracts based on ROC analysis.

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.

Optical quality after myopic photorefractive keratectomy and laser in situ keratomileusis: comparison using a double-pass system.

PURPOSE: 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. SETTING: Universitat Politècnica de Catalunya, Terrassa, Barcelona Institute of Ocular Microsurgery, Barcelona, Spain. DESIGN: Comparative case series. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Objective optical assessment of tear-film quality dynamics in normal and mildly symptomatic dry eyes.

PURPOSE: 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. SETTING: Hospital Universitario Virgen de la Arrixaca, Murcia, Spain. DESIGN: Evaluation of diagnostic test or technology. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Effect of laser in situ keratomileusis on vision analyzed using preoperative optical quality.

PURPOSE: To evaluate the effect on vision of laser in situ keratomileusis (LASIK) based on preoperative optical quality. SETTING: Universitat Politècnica de Catalunya, Terrassa, and Barcelona Institute of Ocular Microsurgery, Barcelona, Spain. DESIGN: Comparative case series. METHODS: The relative change in optical quality and visual acuity were evaluated in eyes that had LASIK for myopia. The optical quality was assessed before and 3 months after surgery using parameters provided by a double-pass system. Patients were classified into 4 groups by preoperative optical quality: low (Group 1), moderate (Group 2), high (Group 3), and very high (Group 4). RESULTS: The study evaluated 25 patients (50 eyes). The optical quality parameters improved postoperatively in Group 1 and Group 2, with the improvement ranging from 15% to 21% and from 13% to 17%, respectively. The preoperative and postoperative optical quality in Group 3 was similar. The optical quality in Group 4 worsened significantly by percentages ranging from -20% to -26%. Although visual acuity had the same trend, there were no statistically significant changes. CONCLUSION: The changes in optical quality after LASIK surgery depended on the patient's preoperative optical quality; visual acuity showed the same trend, although no change was significant.

Intra- and intersession repeatability of a double-pass instrument.

PURPOSE: To evaluate the intra- and intersession repeatability of the optical quality parameters provided by the Optical Quality Analysis System (OQAS), which is based on the double-pass technique. METHODS: We performed optical quality measurements using the OQAS on 20 eyes of 10 healthy subjects who had best spectacle-corrected visual acuity of 20/20 or better. Measurements were performed by the same examiner in three different sessions that were separated by 10-min intervals. The subject's eye was realigned at the beginning of each session. During each session, three consecutive measurements were taken without realignment. The following optical quality parameters were analyzed: the modulation transfer function cutoff frequency (MTFcutoff), the Strehl ratio, the OQAS values (OV) at contrasts of 100%, 20%, and 9%, and the objective scatter index (OSI). RESULTS: The mean coefficients of repeatability obtained for the first session were 4.51 (MTFcutoff), 0.049 (Strehl ratio), 0.15 (OV 100%), 0.21 (OV 20%), 0.28 (OV 9%), and 0.11 (OSI), which were similar to those found in the second and third sessions. The confidence limits in the Bland and Altman charts when the intrasession repeatability was assessed (in a comparison of the first and second measurements of the first session) ranged from -3.16 to 3.94 (MTFcutoff), -0.060 to 0.069 (Strehl ratio), -0.12 to 0.18 (OV 100%), -0.20 to 0.23 (OV 20%), -0.29 to 0.27 (OV 9%), and -0.12 to 0.13 (OSI). The same limits when the intersession repeatability was assessed (in a comparison of the first and second sessions) ranged from -5.30 to 5.49 (MTFcutoff), -0.054 to 0.050 (Strehl ratio), -0.17 to 0.17 (OV 100%), -0.22 to 0.19 (OV 20%), -0.26 to 0.29 (OV 9%), and -0.12 to 0.13 (OSI). CONCLUSIONS: Our findings showed that OQAS is a clinical instrument with a good intra- and intersession repeatability and that the realignment of the eye does not introduce any additional variability in the measurements.

Optical quality one month after verisyse and Veriflex phakic IOL implantation and Zeiss MEL 80 LASIK for myopia from 5.00 to 16.50 diopters.

PURPOSE: To evaluate the eye's optical quality after phakic intraocular lens (IOL) implantation and LASIK for moderate to high myopia. METHODS: The retinal image quality of 45 patients was evaluated after undergoing one of three surgical procedures (9 patients with Verisyse IOL [AMO] implants, 11 patients with Veriflex IOL [AMO] implants, and 25 patients who underwent LASIK). Patients were aged <40 years, had at least 5.00 diopters of myopia, and had preoperative best spectacle-corrected visual acuity and postoperative uncorrected visual acuity better than 20/30. The eye's optical quality was measured using the Optical Quality Analysis System (OQAS, Visiometrics S.L.), which is an instrument based on the double-pass technique. Measurements were performed before surgery and 1 day and 1 month after surgery. RESULTS: Optical quality worsened noticeably 1 day after surgery with the Verisyse IOL with a 50% to 60% loss, most likely due to the large incision and the presence of sutures in most eyes. The LASIK technique and Veriflex IOL implant did not cause as remarkable a decrease in optical quality (20% to 25% loss). One month after surgery, the optical quality of patients with IOL implants was high, although some surgically induced astigmatism remained, especially in the Verisyse patients. Conversely, LASIK patients had slightly lower optical quality, with optical parameters that represented 90% of their initial value. CONCLUSIONS: Verisyse and Veriflex phakic IOL implantation and LASIK are both safe and effective in correcting moderate to high myopia, but they involve different processes of optical quality recovery. One day after surgery, the Verisyse IOL implantation significantly reduced the eye's optical quality, mainly due to the larger incision required and the higher number of sutures used. This reduction was not as remarkable with the other two techniques. However, 1 month after surgery, patients with IOL implants recovered more optical quality than LASIK patients.

Optical quality of foldable monofocal intraocular lenses before and after injection: comparative evaluation using a double-pass system.

PURPOSE: To use the double-pass technique to evaluate the in vitro optical quality of foldable monofocal intraocular lenses (IOLs) used to correct aphakia. SETTING: Universitat Politècnica de Catalunya, Terrassa, and Instituto de Microcirugía Ocular de Barcelona, Barcelona, Spain; Universidad Nacional de Tucumán, Tucumán, Argentina. METHODS: This study assessed the in vitro optical quality of 7 IOLs before and after injection in an artificial eye that was attached to a double-pass system (Optical Quality Analysis System [OQAS]). The procedure imitated the conventional in vivo technique used to assess the optical quality of eyes with an IOL. The following parameters were evaluated: point-spread function, modulation transfer function (MTF), MTF cutoff frequency, Strehl ratio, and OQAS values. RESULTS: The in vitro optical quality of most IOLs was as good after injection as before injection. In 1 IOL, the post-injection optical quality was statistically significantly different but the optical quality remained high. CONCLUSIONS: Results indicate that after an IOL is placed in the eye, its optical performance will be good, providing good visual quality. The eye cell model attached to the double-pass system was useful and effective for fully characterizing the optical quality of IOLs and evaluating variations resulting from the injection process.