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Table of Contents
ORIGINAL ARTICLE
Year : 2020  |  Volume : 2  |  Issue : 1  |  Page : 21

Evaluation of visual function in patients with cataract, amblyopia, optic neuritis, and retinopathies


Department of Ophthalmology, Fundación Universitaria de Ciencias de la Salud, Hospital de San José, Bogotá, Colombia

Date of Submission15-Jan-2020
Date of Decision04-Feb-2020
Date of Acceptance08-Mar-2020
Date of Web Publication19-Aug-2020

Correspondence Address:
Dr. Adriana Solano
10 # 1875, Bogotá
Colombia
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/PAJO.PAJO_4_20

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  Abstract 


Purpose: The purpose was to describe the changes in the visual function of patients with cataract, optic neuritis, amblyopia, and retinopathies evaluated at the Hospital de San José, Bogotá, Colombia, between August 2015 and May 2019.
Materials and Methods: This is a descriptive cross-sectional study. One hundred and ninety-six patients with a diagnosis of cataract, retinopathies, optic neuritis, and amblyopia were evaluated; the tests were performed to determine the visual function (visual acuity, stereopsis, contrast sensitivity, and color tests). Qualitative and quantitative characteristics were described.
Results: Of the 196 patients, 17.3% had amblyopia of any cause, 16.8% optic neuritis, 40.8% cataract, and 25% retinopathies of multiple etiologies. Amblyopic patients presented less deterioration of the stereopsis (160 arc seconds), whereas patients with retinopathy presented more significant compromise (400 arc seconds). Patients with optic neuritis showed severe deterioration in contrast sensitivity; in the other pathologies, the decline was moderate. Nearly 42.4% of the patients with optic neuritis and 38% of the amblyopic patients did not present color vision disorders, whereas 32.6% and 31.2% of the patients with retinopathy and cataract showed tritanomaly.
Conclusion: Visual acuity is not equivalent to visual function. Stereopsis, contrast sensitivity, and color vision are affected by pathologies such as amblyopia, optic neuritis, cataract, and retinopathies. These assumptions of visual function could be considered for studies that take into account all the factors that may compromise the visual performance and, accordingly, define early diagnosis strategies, in addition to therapeutic behaviors such as performing early cataract surgery and visual rehabilitation.

Keywords: Amblyopia, cataract, color vision, contrast sensitivity, depth perception, optic neuritis, visual acuity


How to cite this article:
Espinosa N, Pinto I, Arias A, Toro L, DiazGranados J, Solano A. Evaluation of visual function in patients with cataract, amblyopia, optic neuritis, and retinopathies. Pan Am J Ophthalmol 2020;2:21

How to cite this URL:
Espinosa N, Pinto I, Arias A, Toro L, DiazGranados J, Solano A. Evaluation of visual function in patients with cataract, amblyopia, optic neuritis, and retinopathies. Pan Am J Ophthalmol [serial online] 2020 [cited 2020 Sep 19];2:21. Available from: http://www.thepajo.org/text.asp?2020/2/1/21/292655




  Introduction Top


The sense of vision is compared to a complex circuit in which anatomical, molecular, and cellular mechanisms intervene for its proper functioning that allows us to have an optimal visual perception of the world around us. The initial stage of this process is determined by optical and molecular phenomena through which light is translated into electrical signals in the retina, generating the information that will be transmitted from the eye to the brain.[1] The alteration in any of these mechanisms will produce a visual dysfunction that results in a change in the quality of life of the patients and a major public health problem.[2],[3]

Worldwide, there are approximately 1.3 billion people with visual impairment.[4] More than 140 million visually impaired people live in developing countries, and 26 million of them are in Latin America.[2],[5] Its distribution is not uniform throughout the world because the least developed regions are the most affected. It is also distributed unevenly between age groups, as older adults suffer the most (82%), and there is also an imbalance in terms of distribution by gender because the risk of visual impairment is higher in women than in men (ratio 1.5:1).[2]

Cataract continues to be the leading cause of visual deficiency in all regions of the world, except the most developed countries. Other pathologies that generate visual function deficits are glaucoma, age-related macular degeneration,[6] retinopathy, amblyopia, and eye trauma,[7] in addition to pathologies such as optic neuritis and other retinopathies, which, although less frequent, have a significant impact on the quality of life of patients.[8] In the routine evaluation of patients, the test that is taken into account to determine the degree of the visual deficit is visual acuity (VA) using the Snellen optotype, most of the time. However, the determination of visual function should include other tests such as contrast sensitivity, stereopsis, and color perception because they are essential to determine the degree of visual impairment and need for visual rehabilitation.[9]

In the literature, some studies evaluate stereopsis, contrast sensitivity, and color perception in some specific pathologies; however, no studies are found locally or internationally where the results of different visual function tests are compared in patients with pathologies such as cataract, optic neuritis, retinopathies, and amblyopia. Lee and Isenberg, in the United Kingdom, evaluated the relationship between VA and postocclusion therapy stereopsis in patients with amblyopia, showing that as VA improved, stereopsis also improved.[6] On the other hand, Shandiz et al. described a direct relationship between the increase in the degree of cataract and the decrease in contrast sensitivity.[9] Datta et al. in the United Kingdom found a relationship between the degree of compromise of contrast sensitivity and stereopsis with quality of life and the degree of disability in female cataract patients and their change after treatment.[10] Studies on the impact of pathologies such as optic neuritis, retinopathies, cataract, and amblyopia on color perception are scarce. However, as of 1982, early changes in color vision began to be described in these and other diseases, as well as this evaluation could be useful in the early diagnosis and treatment.[11],[12]

The purpose of this study is to describe the alterations of visual function in patients with cataract, optic neuritis, amblyopia, and retinopathies of any cause, comparing the behavior of changes in visual function between pathologies, according to the compromise of VA, in patients assessed at the San José Hospital, in Bogotá, Colombia, between August 2015 and May 2019.


  Methods Top


A descriptive cross-sectional study was carried out. Patients with a diagnosis of cataract, optic neuritis, retinopathy, and amblyopia of different etiologies were assessed at the San José Hospital in Bogotá, Colombia, between August 2015 and May 2019. All patients with these diagnoses who met the inclusion criteria were included.

Patients with the diagnoses mentioned above with VA between 20/20 and 20/400 with the best optical correction were included. Preverbal patients, with a single eye, diagnosis of glaucoma, corneal alterations and pathologies that did not allow assessing the fundus were excluded. Demographic data, visual acuity (VA), diagnosis (cataract, optic neuritis, retinopathies, and amblyopia), degree of stereopsis, contrast sensitivity, and type of color alteration were collected. The data collection and the application of the tests were carried out under standardized conditions of light and distance (all the tests were carried out in the same office), according to the indications proposed by the tests to guarantee proper execution. The analyzed data were taken from a single assessment of each patient, and the information was recorded in a standardized format prepared by the authors for subsequent interpretation.

The best-corrected VA was evaluated using the Snellen chart at 20 feet and classified as normal: 20/20–20/30; mild alteration: VA of 20/40–20/60; moderate alteration: 20/70–20/150, and severe alteration: 20/200–20/400 for each eye. The stereopsis was evaluated using the Titmus Test ®. Contrast sensitivity was assessed using The Mars Letter Contrast Sensitivity Test ® (Pelli Robson type test), and color perception was evaluated with the Roth 28-ColorTest ® test.

Stereopsis was evaluated binocularly and was classified as follows: normal values of 20–40 arc seconds; mild alteration 50–100 arc seconds and, moderate alteration worse than 100 arc seconds. These results were related according to the VA of the most compromised eye, bearing in mind that this is the one that will affect binocular function the most, and its behavior among the different pathologies was examined.

Contrast sensitivity was evaluated monocularly, measured in logarithmic units (LogMar), and classified according to the recommendations of the test provider: normal values 1.52–1.92; moderate defect: 1.04–1.48; severe defect, 0.52–1.00 and, defect depth <0.48. These values were correlated with the degree of VA of the eye with the diagnosis of interest, and its behavior in the different pathologies was compared.

Finally, the color perception test was performed under monocular conditions. The results were evaluated and classified by the authors as follows: normal, deuteranopia (alteration in the perception of green color), protanopia (change in the perception of red color), tritanopia (alteration in the perception of blue color), scotopic defect (monochromatic perception), and tetartan-type defect (alteration in the perception of yellow color). The degree of VA of the eye was correlated with the study pathology, and its behavior was evaluated among the different pathologies.

Information was analyzed with the statistical package Stata 12 absolute and relative frequencies, measures of central tendency, dispersion, and location (stereopsis, sensitivity to contrast, and color vision) were used.

This investigation is considered risk free for patients according to Resolution 8430 of 1993. Patient confidentiality was respected, and identification data were not included.


  Results Top


One hundred and ninety-six patients corresponding to 196 eyes were studied; the median age was 62 years (IQR 41.5–69) (interquartile range), 54% of the patients were female. Nearly 40.8% of the patients had a diagnosis of cataract, 25% retinopathies, 17.3% amblyopia, and 16.8% had a diagnosis of optic neuritis. Male patients had a more frequent diagnosis of amblyopia, cataract, and retinopathies of any etiology. Regarding the age at which the tests were performed for patients with the diagnoses of interest, the median age of patients with amblyopia and optic neuritis was lower than the median age of those with cataracts and retinopathies (42 and 31 years vs. 62 and 69 years, respectively) [Table 1].
Table 1: Sociodemographic and clinical characteristics of the evaluated patients

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Regarding the different degrees of VA according to the pathology, it was found that 55.8% of the patients with amblyopia presented moderate compromise of VA. In the rest of the pathologies, most of the patients presented mild compromise of VA [Table 1].

The results of the different visual function tests are reported below:

Stereopsis in relation to pathologies

Patients with amblyopia had median stereopsis of 160 arc seconds (interquartile range 63–400 arc seconds), whereas the median stereopsis of patients with retinopathies was 400 arc seconds [Graph 1].



Sensitivity to contrast in relation to pathologies

It was found that in patients with amblyopia, the median contrast sensitivity was 1.12 (moderate decrease), followed by patients with cataract and retinopathy, both with 1.04 (moderate decrease), and lastly optic neuritis 0.92 (severe decrease) [Graph 2].



Color perception in relation to pathologies

Almost 38.2% of amblyopic patients did not show any alteration, followed by 26.4% with a tetartan-type defect and 17.6% with tritan-type defects. Of the patients with optic neuritis, 42% did not present any color alteration, whereas 18.1% and 12.1% presented tritanomaly and deuteranomaly, respectively; the least frequent color alteration was scotopic (3%). In patients diagnosed with cataract and retinopathy, tritanomaly was the most frequent change (31.2% and 32.6%, respectively). In patients with amblyopia and retinopathy, protan-type abnormalities were the least frequent, and none presented deuteranomaly [Graph 3].



The results regarding the relationship of the different degrees of VA on the visual function test were:

Stereopsis

Patients with amblyopia and retinopathies have deterioration of stereopsis as VA decreases (between a slight and moderate reduction in VA); however, this variation is more significant in amblyopic patients (median stereopsis of 63 arc seconds to 400 arc seconds); while in patients with optic neuritis and cataract, the relationship between the decrease in VA and stereopsis is not so clear [Graph 4].



Sensitivity to contrast

It was found that patients with the aforementioned pathologies with VA between 20/40 and 20/60 had a moderate compromise in contrast sensitivity (between 1.04 and 1.48). In patients diagnosed with amblyopia, cataract, and retinopathy with VA worse than or equal to 20/200, contrast sensitivity was severely compromised (0.52 to 1.00). In contrast, in those diagnosed with optic neuritis and this same VA, deterioration in contrast sensitivity was deep (≤0.48) [Table 2].
Table 2: Contrast sensitivity according to visual acuity

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Perception of color

In amblyopic patients, it was found that 63% of patients with a slight decrease in VA had no color vision disturbances, whereas 52.6% and 50% of eyes with a moderate and severe decrease, respectively, in VA had a defect in tetartan type.

In patients with optic neuritis, it was found that in the mild, moderate, and severe decrease in VA, tritanomaly was the most frequent defect (36%, 45.5%, and 37.5%, respectively), however the severity of this alteration was higher in patients with poorer VA.

In patients with a cataract diagnosis, regardless of the degree of AV involvement, tritanomaly and mixed defects were the most frequent changes in color vision.

Nearly 30% of the patients with retinopathy and a slight decrease in VA did not show any color alteration, whereas patients with moderate VA compromise presented tritan-type and scotopic defects, each with 26.7%. Lastly, 35.7% of the patients with severe VA involvement presented tetartan-type defects.


  Discussion Top


With the correct functioning of the visual system and each of its components, the interaction of the human being with the surrounding environment occurs, that is, it determines the degree of functionality of the latter with daily activities. This is why the assessment of visual function could be a key piece in evaluating the quality of life of patients with certain ophthalmic pathologies;[12] an example of this is the study developed by Datta et al.,[10] who evaluated the importance and impact of VA, stereopsis, and contrast sensitivity on the quality of life of older women with cataract using the Visual Function Index (VF-14), finding a relationship between the commitment of stereopsis and contrast sensitivity with quality of life; on the other hand, it should be mentioned that in routine ophthalmological consultation, only VA is usually valued as a classification parameter of visual deficiency and/or disability, leaving aside the evaluation of stereopsis, contrast sensitivity, and color perception.

The results are analyzed below according to the pathologies of interest:

Amblyopic patients

Regarding stereopsis, in our study, we found that the average VA of amblyopic patients was 20/80, and the median stereopsis was 160 arc seconds. This differs from that reported by Jeon and Choi[13] on 35 patients diagnosed with anisometropic amblyopia with an average VA of the worst eye of 0.374 (standard deviation 0.369) LogMar and an average of stereopsis (with Titmus Test ®) of 641 (SD 1443) (standard deviation) arc seconds. Lee and Isenberg,[6] in California, reported an average stereopsis of 1167.4 arc seconds (with Titmus Test ®) on 61 patients with a mean VA of 0.43 LogMar. These differences could be explained by the different types of amblyopia and the variation between the degrees of VA between one eye and the other. Although so far, no definitive relationship has been established between VA and the degree of stereopsis, it is known that with VA better than or equal to 20/40, a constant and useful level of stereopsis can be maintained thanks to a mechanism of contour detection within the visual system.[14]

Regarding the contrast sensitivity test, a median of 1.12 was found in amblyopic patients, which corresponds to moderate deterioration and as VA decreases, contrast sensitivity also decreases. These results are similar to those reported by Chatzistefanou et al.[15] in 48 amblyopic (unilateral) patients and 22 successfully treated amblyopic subjects, and 20 control patients, finding that both untreated and treated amblyopic eyes, as well as nonamblyopic “normal” contralateral eyes, show a significant decrease in contrast sensitivity compared to controls. Despite the fact that the history of treatment of amblyopia patients and control patients were not taken into account in our study, these findings suggest the importance of evaluating contrast sensitivity in response to treatment of this pathology, as well as the evaluation of the contralateral eye.

Lastly, 62% of amblyopic patients presented alteration in color perception, which correlates with what was concluded by Slope,[16] who argue that binocularity is essential to form a three-dimensional and color representation of the world that surrounds us; therefore, patients with amblyopia present an alteration in the processing of stimuli by the magnocellular and parvocellular pathways, with the latter responsible for responding to color stimuli.

These results could be related to what was reported by Kumaran et al.[17] in a descriptive study in which 37 adult patients with amblyopia of different etiologies participated. The participants manifested difficulties in daily tasks such as driving (setting distances and changing lanes), reading (small print, reading for a long time), and sports (catching a ball); they also described problems using stairs and other activities such as doing work tasks and routine tasks (cutting vegetables). Although the VA of the patients was not taken into account, these results show the impact of amblyopia on the daily life of these patients.

Patients with optic neuritis

Since 1985, Friedman et al.[18] have proposed the association of the decrease in VA with the decrease in in-depth perception in patients with optic neuritis; of 17 patients studied with this diagnosis, 76% presented a result in the Titmus ® Test not according to VA in the nomogram proposed by Donzis in 1983 (14); for example, patients with visual acuities better than 20/40 had very low scores on the Titmus ® Test (3/9, 4/9, 6/9, and 1/9) and although the evaluation scale used it is not comparable, in our study, it was found that patients with a mild and moderate decrease in VA presented median stereopsis of 160 arc seconds, whereas in patients with a severe decrease in VA, the median stereopsis presented was 400 arc seconds. However, what is clear for both studies, although with limited samples and according to what was reported by Shah et al.,[19] patients with VA worse than 20/30 in the worst eye, will present alteration in stereopsis.

On the other hand, it should be mentioned that patients with optic neuritis presented greater compromise in contrast sensitivity than the other subgroups, especially patients with VA worse than or equal to 20/200, which is similar to that reported by Owidzka et al. and Beck et al.[20],[21] in patients with optic neuritis due to multiple sclerosis and with sequelae of optic neuritis (without a decrease in VA or visual field involvement), this could be related to the compromise of the nerve fibers of the papillomacular bundle, responsible for the transmission of the visual stimulus sent by the foveal cones (cones with greater contrast discrimination capacity).[22]

Regarding color perception, unlike what was found in the Optical Neuritis Treatment Trial,[23] in which 40.8% of patients presented tritanomalia, and 29.6% presented alteration in the vision of the patients (Red-green colors), in this study, 42% did not present alterations in color perception, and only 18.1% presented tritanomaly, 12.1% deuteranomaly, and 6% protanomaly.

The foregoing demonstrates the importance of the evaluation and individualization of patients diagnosed with optic neuritis because due to their variable etiology and severity, it is essential to recognize the commitment of visual function and consider the possibilities of visual rehabilitation that may favor the least impact of this pathology. Additional studies are required to evaluate the impact of visual function compromise on the quality of life of these patients.

Patients with cataract

Most studies worldwide use VA to determine visual function compromise due to cataract, as well as to evaluate the surgical result; however, other aspects such as binocular function are ignored in these patients. Studies such as that reported by Manoranjan et al.,[24] in Nepal, showed that of 142 patients diagnosed with a cataract (without other ophthalmological comorbidities), 71% did not present stereo acuteness (defined as a value of 1300 arc seconds) and the median of the remaining 29% stereopsis was 192 arc seconds in the Frisby stereo test; postoperatively, the improvement in stereopsis was significant, reaching a median of 19.79 arc seconds. In the study reported by Datta et al.,[10] in the United Kingdom, in a sample of 306 female patients over 70 years of age and bilateral cataract (without other ophthalmological pathologies), they found that for a VA median 0.20 Log Mar the median of stereopsis was 150 s of arc, 6 months after cataract surgery due to phacoemulsification, the median stereopsis did not change. Although these case series do not take into account the association between VA and stereopsis, these results correlate with what was found in our study, where the median stereopsis for patients with a mild and moderate decrease in VA was 200 and 400 arc seconds, respectively, showing that the decrease in VA favors the deterioration of the stereo acuteness, however, the impact of the bilaterality of the cataract, as well as the anisometropia induced by it, is not yet clear. The results of the stereopsis in the postoperative period of these two studies are contradictory.

Contrast sensitivity, in addition to evaluating the stimulus size, as the VA measurement does, allows us to independently evaluate contrast, which is why it is a useful measure in the characterization of visual function. It is also one of the aspects early compromised in cataract patients.[19],[25] In our study, it was found that all the cataract patients presented a compromise of contrast sensitivity; however, the variability of the data was wide. Datta et al.,[10] in the United Kingdom, suggest a strong association between VA involvement, contrast sensitivity, and impairment of quality of life in cataract patients, and in our study, 50% of cataract patients presented moderate, severe, and/or profound compromise of contrast sensitivity, suggesting the importance of contrast sensitivity assessment to define the need for cataract surgery.

Simunovic et al.[23] argue that the most common mechanism of acquired deficiency of color vision occurs due to the increase in optical density and absorption of pigment at the level of the lens that favors the presence of tritanomalies and alteration in the perception of yellow color. These approaches are correlated with the results obtained in cataract patients, in which 31.2% and 22.5% presented tritan- and tetartan-type defects, respectively. However, they differ from that reported by Bergholz et al.[26] in the study of ophthalmological health status of an aging population (data from the Berlin Agin Study II, BASE II) with pathologies such as cataract, macular degeneration related to age, retinopathies, and glaucoma, among others. Although they do not describe the alterations according to the pathologies presented, they report that protanomaly and deuteranomaly were the most frequent alterations in color vision and also describe difficulties in carrying out activities of daily living such as driving and in older adults (>60 years) greater dependence (according to the results of the visionrelated quality of life assessment questionnaire [VFQ25]). It could be suggested that the great variation in the color alterations found in this study may be related to the different types and degrees of cataract, however additional studies are required to evaluate this relationship and the influence of other factors.

Patients with retinopathies

No information was available on the changes in stereopsis in cases of retinopathy of any etiology, however, in diabetic retinopathy, Faraji et al.[27] compared the stereopsis of patients with early retinopathy (characterized only by the presence of microaneurysms at the worst eye) and control patients and found that 86% of the patients with diabetic retinopathy presented stereopsis of 40, 50, and 60 arc seconds in the Titmus Test, whereas in nondiabetic patients, 91% presented stereopsis of 40 arc seconds. These findings vary from those found in this study because the median stereopsis found was 400 arc seconds (RIQ: 100–400). This variation could be explained by the different etiologies of retinopathy and the fact that the degree of retinopathy was not taken into account in the case of diabetic patients. What is clear for both studies is that in the majority of patients, stereopsis had decreased, and this could be correlated with retinal neurodegeneration that occurs previously or concomitantly with retinal microvascular changes.[27] The alteration of depth perception could be a risk factor for falls in patients with diabetic retinopathy.[27]

Regarding contrast sensitivity, Arend et al.[28] concluded that contrast sensitivity correlates more sensitively with angiographic findings than VA itself in patients with diabetic retinopathy in the absence of macular edema and even in 20/20 VA; therefore, the assessment of sensitivity to contrast could be a useful measure in the early diagnosis of these diseases; however, additional studies are required in cases of retinopathy of nondiabetic etiology.

In patients with retinopathy of any etiology, 32.6% had tritan-type defects and only 16% had no abnormalities; these findings could be related to the histological studies described by Cho et al.[29] in eyes with diabetic retinopathy, in which there is a selective reduction of the S cones, in charge of the blue–yellow color processing. These results are not applicable to the results obtained in cases of nondiabetic retinopathy. As mentioned in the results of the BASE II study, these changes in color vision favor the compromise of the quality of life of patients with ophthalmic pathologies (including diabetic and hypertensive retinopathy). The great variability of the alterations in color perception could be related to the different types of retinopathies included in the study; however, additional studies are required to confirm these findings.


  Conclusion Top


Finally, it is clear that VA is not equivalent to visual function, and that having alterations, in-depth perception, contrast sensitivity, and color vision could significantly affect the quality of life of patients with ophthalmic pathologies such as those described in our study; therefore, additional studies are suggested, in which, in addition to characterizing the alterations of visual function, the impact of these on the compromise of quality of life is evaluated. The most widely used instruments worldwide are the National Eye Institute 25item Visual Function Questionnaire, the Vision Core Measure1, and the VF14.[30] The results of these possible studies, new criteria could be proposed that, in the case of cataract patients, indicate their surgical management. A study is suggested in which the sample size of the cataract patients is expanded and the visual function and quality of life are evaluated before and after surgery. In patients with optic neuritis, evaluation of visual function may determine the need for and subsequent response to visual rehabilitation. In patients with retinopathies, the results of these tests could be evaluated according to the etiology and in the case of diabetic and hypertensive retinopathy according to their severity, which would allow the possibility of new screening strategies and/or early diagnosis of these diseases to be considered.

We recognize the size of the sample as limitation of this study, especially in the subgroups of amblyopia and optic neuritis; also the learning difficulties for the development of the different tests taking into account the great variation in the age of the patients between the different groups and the complexity of some tests could generate an information bias; to control this bias, it was verified that the patients understood the process to develop the tests (all the tests were carried out by two of the authors). Due to the study design, patients without pathology (cases and controls) were not taken into account. Finally, we recognize the limited information found, as well as the variability of the existing tests, to assess visual function between studies.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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    Tables

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