Vision-Related Quality of Life in Patients with Ocular Chemical Burns

Abstract

Purpose.: To assess vision-related quality of life in patients with ocular chemical burns by the application of the 25-item National Eye Institute Visual Function Questionnaire (NEI VFQ-25).

Methods.: Eighty-seven patients with ocular chemical burns were enrolled in the study from January 1 through May 31, 2010. Apart from the collection of sociodemographic and clinical data, NEI VFQ-25 with an additional appendix question, being translated to Chinese, was administered to all subjects. Main outcome measures were comparison of the NEI VFQ-25 subscale item scores among subgroups and multivariate analysis of the NEI VFQ-25 subscale scores.

Results.: Fifty-five subjects were bilaterally burned and the rest were unilaterally injured. The mean age of enrolled subjects was 39.4 ± 11.6 years, with the majority being male (98.9%) and worker (77.0%); the mean composite score of all subjects was 40.4 ± 23.8. The composite score and majority subscale scores of binocularly injured patients were significantly lower than those of monocularly injured patients. Further comparisons among groups divided by either clinical severity classification or best-corrected visual acuity (BCVA) produced similar results. The BCVA of both the better-seeing eye and the worse-seeing eye strongly correlated with the NEI VFQ-25 composite score (ρ = 0.664 and 0.498, both P = 0.000). Multivariate regression analysis revealed that the VFQ-25 composite score correlated significantly with the following independent variables: BCVA of the better-seeing eye and the worse-seeing eye, the injury classification of the less severely injured eye, and correct and immediate irrigation after injury as well.

Conclusions.: Ocular chemical burns have a significant and extensive impact on patients' visual function outcomes and vision-related quality of life.

Ocular chemical burns constitute one of the most common ocular injuries in developing countries, with a reported prevalence ranging from 1.25 to 4.4‰. ^{1 –5} The severity of ocular injury after a chemical exposure has a close relationship with the contact surface area and degree of penetration. Severe chemical burns, either alkaline or acid, usually lead to complete destruction of the ocular surface, cornea opacification, permanent vision loss, and rarely loss of the eye. ⁶ According to a previous retrospective case series, severe ocular chemical injury accounted for a small but significant part of corneal blindness in China. ⁷ Moreover, most victims are young and ocular chemical injuries not only cause visual impairment but also affect their ability to perform various vision-specific functions in daily life. Therefore, the traditional objective examinations to measure the clinical outcome in ophthalmology, for instance visual acuity, are inadequate in assessing a broad array of outcomes, such as physical function, social function, and overall health. However, until now, only one study focusing on health-related quality of life (QOL) in chemical warfare victims with ophthalmologic complications has been published, ⁸ and no studies have been performed to specifically determine the vision-related QOL in persons with ocular chemical injury. 

To understand the effect of a disease on patients' QOL and to evaluate disease from the patients' perspective, the National Eye Institute 25-Item Visual Function Questionnaire (NEI VFQ-25) may be used. It is a vision-related quality of life instrument designed to assess patients' perception of their visual function and QOL. ⁹ The VFQ-25 has been used to track the outcome of many ocular diseases, including age-related macular degeneration, retinal vein occlusion, retinal detachment, diabetic retinopathy, glaucoma, and various ocular surgeries. ^{10 –17} Therefore, we assessed the QOL in persons with ocular chemical injury by applying the NEI VFQ-25. 

Materials and Methods

Subjects

This prospective study enrolled 87 consecutive patients with ocular chemical burns who were scheduled for vision care at the Department of Ophthalmology, Shanghai Eye, Ear, Nose, and Throat Hospital of Fudan University, from January 1 through May 31, 2010. Patients were enrolled into the study if they were 16 years of age and older, with at least 3 months of clinical course to achieve relatively stable results of the visual outcome, having no other systemic or ocular disease that could potentially affect vision. If the patients had ocular surgery after injury, the frequency and method of surgery were recorded. The study was approved by the ethics committee of the hospital and conducted according to the tenets of the Declaration of Helsinki. Written informed consent was obtained from all patients. 

Clinical Assessment and Tests of Visual Function

All patients underwent a complete ophthalmologic examination, including best-corrected visual acuity (BCVA), slitlamp biomicroscopy, tonometry, and indirect ophthalmoscopy if the dioptric media was clear. The degree of injury was assessed by an experienced cornea specialist under the slitlamp biomicroscopy, according to the Hughes-Roper-Hall classification scale. ^18,19 Visual acuity testing was performed for each eye separately. The BCVA was evaluated with Snellen equivalents, based on a standard refraction and testing protocol at a starting distance of 5 m. Participants who failed to read the largest letters at 5 m were tested at 1 m. Patients with failure to read any letters were tested using counting fingers, hand movements, and light perception. Intraocular pressure (IOP) was measured with a Goldmann applanation tonometer unless the cornea could not be exposed sufficiently due to severe symblepharon. 

Visual Function Questionnaire (VFQ-25)

A Chinese version of the VFQ-25, which was used in previous studies, ^20,21 was administered to all subjects, and they were requested to fill out the questionnaire by themselves. The research staff explained the questionnaire to them, and provided assistance when required. For the participants whose eyesight was too poor to enable reading, a single research staff member read the questionnaire for them, in a neutral and uniform manner, and recorded the patients' choices. The completed questionnaires were reviewed for missing data by the research staff. 

NEI VFQ-25 with an additional question, being translated to Chinese, was used in the present study to evaluate the vision-specific quality of life. Since the response rate of No.14 item was rather low in the Chinese population, ²⁰ we chose item A8 from the NEI VFQ-39 to serve as an appendix of the No. 14 item according to the instruction of the NEI VFQ-25 manual. If the statistical analysis showed a low response rate of the No. 14 item in the present study, the result of its appendix would be used to alleviate the impact of a high miss rate of the No. 14 item on the validity and reliability of the whole questionnaire. Each item in the questionnaire was assigned to one of the 12 subscales: general health, general vision, ocular pain, near activities, distance activities, social functioning, mental health, role difficulties, dependency, driving, color vision, and peripheral vision. Answers to each question on the VFQ-25 were converted to a 100-point scale, in which 100 represents the best possible score or the minimal subjective impairment, and 0 represents the worst or the maximal. Guidelines published by the NEI were adhered to when calculating the above-described scale conversions and subscale scores. 

Statistical Analysis

The mean scores and SDs were calculated for each VFQ-25 subscale and composite score. The Mann-Whitney U test was performed to compare each subscale and composite score between the patients with monocular injury and those with binocular injury. Nonparametric ANOVA was performed to make further analysis on the mean VFQ-25 scores by clinical severity based on the classification of injury and the number of injured eyes (unilaterality or bilaterality), after the adjustment of age and sex. The same analysis was performed to determine the VFQ-25 scores by BCVA in the better-seeing eye. Nonparametric correlation analysis was performed to investigate the relationship between mean VFQ-25 scores and variables, including better-seeing BCVA and worse-seeing BCVA. Multivariate regression analysis was performed to investigate the relationship between clinical variables and the VFQ-25 composite score. The covariates tested were age, educational level, agent of injury, BCVA of the better- and the worse-seeing eye, the classification of both the less and the more severely injured eye, and whether correct irrigation was immediately performed after injury. To facilitate regression analysis, the noninjured eyes of monocularly injured patients were considered as the less severely injured ones and their classifications were recorded as zero. All tests were considered statistically significant at P < 0.05 (SPSS for Windows, version 13.0; SPSS, Inc., Chicago, IL). 

Results

A total of 142 eyes of 87 patients were enrolled in the study, including 55 patients suffering bilateral injuries. The demographics of these subjects are shown in Table 1. The mean age of enrolled subjects was 39.4 ± 11.6 years, with the majority being male (98.9%) and worker (77.0%). The average IOP of injured eyes was 15.99 ± 5.99 mm Hg, ranging from 6.7 to 32.5 mm Hg. 

Table 1.

 

Demographic Data of All Enrolled Subjects

Factor	Number of Patients
Sex
Male	86
Female	1
Age, y	39.4 ± 11.6
	Range: 16–63
Occupation
Factory worker	47
Construction worker	20
Peasant	7
Student	5
Other	8
Education
Illiteracy	2
Primary school	25
Middle school	51
University	7
Postgraduate	2
Location where injury occurred
Workplace	72
Laboratory	7
Home	6
Elsewhere	2

The mean scores of each VFQ-25 subscale are all listed in Table 2, ranging from 23.0 for role difficulties to 67.5 for color vision; the mean composite score was 40.4 ± 23.8. Since the missing rate of driving subscale was rather high (82/87, 94.3%), we omitted this subscale in the calculation of composite score and further analysis according to the suggestion of previous research. ²⁰  

Table 2.

 

Mean Scores for Each Subscale and Composite Scores of VFQ-25 in All Subjects

Subscale	n	Mean	SD	Median	Range
General health	87	47.2	28.5	50.0	0–100
General vision	87	33.7	18.9	40.0	0–80
Ocular pain	87	58.0	26.1	50.0	10–100
Near activity	87	47.6	36.0	50.0	0–100
Distance activity	87	49.9	35.4	56.3	0–100
Social function	87	57.6	38.0	62.5	0–100
Mental health	87	30.1	27.9	18.75	0–100
Role difficulties	87	23.0	28.1	12.5	0–100
Dependency	87	36.1	34.7	25.0	0–100
Driving	5	NA	NA	83.3	0–100
Color vision	87	67.5	38.9	75.0	0–100
Peripheral vision	87	59.7	32.7	50.0	0–100
Composite score	87	40.4	23.8	40.8	3.75–84.8

 NA, not applicable.

The analysis on each subscale score and composite score between the patients with monocular injury and binocular injury revealed that all scores in patients with binocular injury were significantly lower, except the scores for general health and ocular pain, as Table 3 shows. Further analysis showed that the differences in composite score and subscale scores, except those for general health and ocular pain, had statistical significance among groups divided by either clinical severity classification or BCVA in the better-seeing eye, with the lowest scores for a majority of the VFQ-25 subscales in bilaterally injured patients with either the less severely injured eye classified as grade III or IV, or BCVA worse than 20/80 in the better-seeing eye, as Tables 4 and 5 list. 

Table 3.

 

Analysis on Each Subscale and Composite Score between Patients with Monocular Injury and Binocular Injury

Subscale	Binocular Injury (n = 55)		Monocular Injury (n = 32)
	Mean (SD)	Median	Mean (SD)	Median
General health	43.8 (28.8)	50.0	53.1 (27.5)	50.0
General vision	26.2 (14.3)	20.0	46.9 (18.7)	60.0†
Ocular pain	54.9 (26.6)	50.0	63.5 (24.2)	62.5
Near activity	31.7 (31.4)	16.7	74.8 (25.5)	80.0†
Distance activity	33.7 (32.2)	18.8	77.8 (19.8)	87.5†
Social function	42.5 (37.2)	25.0	83.7 (21.9)	90.0†
Mental health	21.3 (25.9)	12.5	45.0 (25.2)	50.0†
Role difficulties	15.9 (23.4)	0.0	35.2 (31.7)	25.0*
Dependency	23.6 (31.8)	8.3	57.6 (28.8)	58.3†
Color vision	53.2 (40.6)	50.0	92.2 (18.4)	100.0†
Peripheral vision	51.1 (37.1)	50.0	79.5 (23.7)	75.0*
Composite score	33.0 (22.3)	26.2	63.1 (18.2)	64.8†

*   P < 0.01;

†   P < 0.001.

Table 4.

 

Analysis on Composite Score and Subscale Scores among Groups Divided by Clinical Severity Classification in the Less Severely Injured Eye

Subscale	Group A (n = 12)		Group B (n = 20)		Group C (n = 30)		Group D (n = 25)		Overall Z Value	Pairwise Comparison
	Mean (SD)	Median	Mean (SD)	Median	Mean (SD)	Median	Mean (SD)	Median
General health	52.1 (27.1)	50.0	53.8 (28.4)	50.0	47.8 (29.9)	50.0	40.2 (26.9)	25.0	3.025
General vision	48.3 (19.9)	40.0	46.0 (18.5)	40.0	33.3 (14.2)	40.0	18.3 (8.3)	20.0	34.173‡	b*,c‡, d†, e‡, f‡
Ocular pain	61.0 (15.2)	62.5	65.0 (28.5)	75.0	47.3 (25.4)	50.0	65.2 (26.1)	62.5	5.502
Near activity	87.5 (19.3)	100.0	67.3 (25.9)	66.7	48.1 (30.2)	50.0	11.9 (20.1)	0.0	45.119‡	a*, b‡, c‡, d*, e‡, f‡
Distance activity	85.4 (14.7)	93.8	73.3 (21.4)	75.0	49.2 (31.9)	50.0	14.8 (21.9)	6.25	43.033‡	b†, c‡, d†, e‡, f‡
Social function	93.7 (9.8)	100.0	77.6 (24.9)	87.5	61.3 (35.4)	62.5	20.1 (26.3)	12.5	37.758‡	b†, c‡, e‡, f‡
Mental health	59.4 (18.2)	56.2	36.4 (25.3)	43.8	26.8 (26.9)	18.8	16.0 (23.6)	6.3	22.620‡	a†, b‡, c‡, e†, f†
Role difficulties	40.6 (26.7)	37.5	31.9 (34.5)	25.0	24.6 (27.8)	25.0	6.0 (9.9)	0.0	18.603‡	c‡, e†, f†
Dependency	64.6 (21.7)	66.7	53.3 (32.2)	50.0	32.8 (34.5)	25.0	10.9 (19.4)	0.0	31.267‡	b†, c‡, d*, e‡, f†
Color vision	100.0 (0.0)	100.0	87.5 (22.2)	100.0	73.3 (34.7)	100.0	29.3 (35.1)	0.0	34.999‡	b*, c‡, e‡, f‡
Peripheral vision	89.6 (19.8)	100.0	73.5 (24.2)	75.0	65.8 (24.1)	50.0	26.9 (27.7)	25.0	35.270‡	b†, c‡, e‡, f‡
Composite score	71.4 (13.3)	76.9	58.2 (19.2)	61.8	44.0 (22.0)	30.3	20.4 (14.7)	16.6	40.221‡	b†, c‡, e‡, f‡

 Group A: unilateral eye injured with the classification as grade I or II; Group B: unilateral eye injured with the classification as grade III or IV; Group C: bilateral eyes involved with the less severely injured eye classified as grade I or II; Group D: bilateral eyes involved with the less severely injured eye classified as grade III or IV. a: group A versus group B; b: group A versus group C; c: group A versus group D; d: group B versus group C; e: group B versus group D; f: group C versus group D.

*   P < 0.05;

†   P < 0.01;

‡   P < 0.001.

Table 5.

 

Analysis on Composite Score and Subscale Scores among Groups Divided by BCVA in the Better-Seeing Eye

Subscale	Group A (n = 10)		Group B (n = 22)		Group C (n = 28)		Group D (n = 27)		Overall Z Value	Pairwise Comparison
	Mean (SD)	Median	Mean (SD)	Median	Mean (SD)	Median	Mean (SD)	Median
General health	46.9 (24.8)	50.0	55.2 (28.5)	75.0	41.0 (26.3)	50.0	46.9 (30.3)	50.0	2.615
General vision	60.0 (15.1)	60.0	42.5 (18.0)	40.0	37.1 (14.5)	40.0	20.0 (8.8)	40.0	40.075‡	a*, b†, c‡, e‡, f‡
Ocular pain	61.9 (12.8)	62.5	64.1 (27.1)	62.5	49.7 (25.8)	50.0	58.6 (27.6)	62.5	4.606
Near activity	91.7 (13.4)	100.0	69.2 (26.2)	75.0	57.5 (29.8)	58.3	15.9 (20.1)	8.3	47.701‡	a*, b‡, c‡, e‡, f‡
Distance activity	82.0 (15.1)	87.5	76.4 (21.3)	87.5	58.6 (30.5)	56.3	18.2 (22.8)	12.5	45.808‡	b†, c‡, d*, e‡, f‡
Social function	90.6 (14.6)	100.0	81.4 (23.6)	50.0	73.8 (31.6)	87.5	23.4 (23.3)	12.5	43.185‡	c‡, e‡, f‡
Mental health	60.2 (23.6)	62.5	40.0 (24.2)	50.0	33.8 (29.2)	31.3	14.4 (20.4)	6.3	24.290‡	a*, b†, c‡, e‡, f*
Role difficulties	46.9 (29.7)	37.5	31.3 (31.9)	25.0	31.6 (30.0)	25.0	6.7 (10.0)	0.0	22.525†	c‡, e†, f†
Dependency	69.8 (22.2)	75.0	53.5 (29.9)	50.0	38.9 (34.3)	33.3	10.9 (18.6)	0.0	37.859‡	b†, c‡, d*, e‡, f‡
Color vision	100.0 (0.0)	100.0	89.6 (20.7)	100.0	77.4 (32.5)	100.0	39.1 (39.1)	25.0	31.767‡	c‡, e‡, f†
Peripheral vision	93.8 (11.6)	100.0	74.8 (24.9)	75.0	75.0 (22.4)	75.0	39.8 (38.6)	25.0	21.484‡	b*, c†, e†, f†
Composite score	71.5 (12.5)	67.9	57.5 (17.6)	59.7	49.3 (20.9)	48.2	22.6 (13.0)	18.9	34.861‡	b†, c‡, e‡, f‡

 Group A: unilateral eye injured with BCVA better than 20/80 in the better-seeing eye; Group B: unilateral eye injured with BCVA worse than 20/80 in the better-seeing eye; Group C: bilateral eyes involved with BCVA better than 20/80 in the better-seeing eye; Group D: bilateral eyes involved with BCVA worse than 20/80 in the better-seeing eye. a: group A versus group B; b: group A versus group C; c: group A versus group D; d: group B versus group C; e: group B versus group D; f: group C versus group D.

*   P < 0.05;

†   P < 0.01;

‡   P < 0.001.

Table 6 presents the correlations between the NEI VFQ-25 scores and BCVA for the better- and the worse-seeing eyes. The NEI VFQ-25 composite score correlated strongly with the BCVA of the better-seeing eye and the worse-seeing eye (ρ = 0.664 and 0.498, respectively, both P < 0.001). Overall, stronger correlations were observed between the NEI VFQ-25 subscale scores and the BCVA of the better-seeing than the worse-seeing eye. All correlations between the NEI VFQ-25 subscale scores and BCVA in the better-seeing eyes were significant, except those for general health and ocular pain. The correlations between NEI VFQ-25 subscale scores and BCVA in the worse-seeing eyes were also significant, with the exception of general health. 

Table 6.

 

Correlations Analysis between the NEI VFQ-25 Scores and BCVA for Better- and Worse-Seeing Eyes

VFQ-25 Subscale/Composite Score	VA (Better-Seeing Eye)		VA (Worse-Seeing Eye)
	ρ	P	ρ	P
General health	0.078	0.565	−0.027	0.846
General vision	0.601	0.000	0.391	0.003
Ocular pain	0.128	0.384	0.294	0.028
Near activity	0.700	0.000	0.505	0.000
Distance activity	0.669	0.000	0.482	0.000
Social function	0.630	0.000	0.440	0.001
Mental health	0.565	0.000	0.476	0.000
Role difficulties	0.551	0.000	0.361	0.006
Dependency	0.689	0.000	0.462	0.000
Color vision	0.628	0.000	0.359	0.007
Peripheral vision	0.651	0.000	0.507	0.000
Composite score	0.664	0.000	0.498	0.000

Table 7 summarizes results of multivariate regression analysis on the relation between the VFQ-25 composite score and several clinical variables. It was shown that the VFQ-25 composite score correlated significantly with the following independent variables: BCVA of the better-seeing eye and the worse-seeing eye, the injury classification of the less severely injury eye, and correct and immediate irrigation after injury as well. 

Table 7.

 

Multivariate Regression Analysis on the Relation between the VFQ-25 Composite Score and Clinical Variables

Variable	Standardized β	t	P
BCVA of better-seeing eye	−0.403	−3.86	0.0003
BCVA of worse-seeing eye	−0.191	−2.54	0.0129
Classification of less severely injured eye	−0.273	−3.42	0.001
Correct and immediate irrigation after injury	−0.254	2.19	0.0311

 The analysis also included age, educational level, agent of injury, and the classification of more severely injured eye, all of which were excluded in the final model.

Discussion

Severe ocular chemical injury accounted for a small but significant part of corneal blindness in China, ⁷ most of which took place in the workplace. An overwhelming majority of chemical injury victims were young men, who were the main labor force and contributed to the majority income of the family. The injuries not only caused visual impairment, but also affected their ability to perform various activities in daily life and working capacity. Therefore, it is of great significance to explore the vision-related functioning in patients with chemical burns by a reliable and valid method, such as the NEI VFQ-25. ^9,20,21  

The present study showed that the NEI VFQ-25 composite scores in patients with chemical burns were significantly lower than those reported in other ocular diseases such as age-related macular degeneration, ¹⁷ central retinal vein occlusion, ¹¹ rhegmatogenous retinal detachment, ¹³ proliferative diabetic retinopathy, ¹² Behçet uveitis, ²³ and dry eye syndrome. ²³ Since chemical burns usually cause severe damage to all ocular surface tissues and bilateral injury occurred frequently, it caused more limitation in mobility and daily activity compared with that in other ocular disorders, as well as more negative impact on victims' well-being and vision-related QOL. 

The present study showed that the score for each VFQ-25 subscale, except that for general health, was significantly lower in patients with binocular injury than that in patients with monocular injury. The finding was in agreement with a previous study, ²⁴ which demonstrated that patients with bilateral visual impairment reported greater difficulty in performing vision-dependent daily activities and poorer vision-related QOL, compared with those with unilateral visual impairment. In the present study, most victims of ocular chemical injury were young men, who did not have severe ocular disorders causing visual acuity impairment before the injury. Since NEI VFQ-25 subscales were correlated with the visual acuity of the better-seeing eye, ^15,17 it is reasonable to deduce that monocularly injured subjects, with a relative healthy eye, had better visual-related function and health-related QOL than those of subjects with binocularly injured eyes. 

Further analysis on VFQ-25 composite and subscale scores among groups divided by either injury classification or BCVA of the better-seeing eye revealed that the subscale and composite score decreased significantly with increased severity of injury or decreased BCVA in the better-seeing eye, except those for general health and ocular pain. It was in agreement with previous reports studying the NEI VFQ-25 scores in patients with disorders involving either unilateral or bilateral eyes such as age-related macular degeneration. ^17,24 The binocularly injured patients, either with the less severely injured eye classified as grade III or IV, or with the BCVA worse than 20/80 in the better-seeing eye, reported the lowest composite and subscale scores compared with those of other less severely injured groups. The higher burn classification usually means greater severity of injury and worse visual outcome, even after treatment, which are associated with higher mean impairment of NEI VFQ-25 subscales. Moreover, the scores for near activity, distance activity, role difficulties, dependency, and mental health were extremely low among all subscales in most severely injured subjects, meaning that the impairment on the visual function caused not only a weakening capacity to perform daily activities, but also poorer mental health of the patients. It should also be taken into account that ocular chemical injuries sometimes cause significant facial disfigurement simultaneously, probably leading to impairment of mental health. In view of this, the importance of mental care should be highlighted in the treatment for chemical injury victims. 

It was revealed that both the better-seeing and the worse-seeing BCVA correlated significantly with the NEI VFQ-25 composite score and a majority of the VFQ-25 subscales. Moreover, stronger correlations were observed between the NEI VFQ-25 subscales and the BCVA of the better-seeing than the worse-seeing eye, in line with previous reports. ^15,17 In patients with chemical burn, especially those with binocular injury, the mean visual acuity in the better-seeing eye deteriorated more or less, and the difference between the better- and worse-seeing eyes was relative small. This slight difference seems to be the reason that the VFQ-25 score correlated with the visual function not only in the better-seeing eye but also in the worse-seeing eye. 

By multiple regression analysis, we found that BCVA in both the better- and the worse-seeing eye, injury classification of less severely injured eye, and immediate irrigation after injury were independent factors relevant to VR-QOL in the patients with chemical burn, whereas age, educational level, agent of injury, and the classification of the more severely injured eye were not relevant factors. Although it is generally accepted that alkaline burn usually causes more severe injury than acid, the present study confirmed that the VR-QOL had a strong correlation to the visual acuity outcome caused by the injury rather than the agent of injury itself. Moreover, immediate and correct irrigation after injury would be helpful to alleviate the damage to the ocular surface and reduce the injury severity, contributing to a better visual outcome and higher VFQ-25 scores. The findings of the present study reconfirmed the importance of immediate and correct irrigation in the first aid and emergency treatment of chemical burns. 

The present study showed that age and education were not relevant to the NEI VFQ-25 composite score after chemical injury. In previous research studying the VR-QOL in patients with Behçet uveitis, significant reductions in visual functioning were observed in relation to age and educational level, ²² with the possible reason that younger and better-educated people are more aware of access to better health care and have better compliance with treatment. We considered the disparity was possibly attributed to the lower number of either old or well-educated subjects in chemical burn victims. Chemical burns frequently occurred in young men, especially in a developing country such as China, and most of them get only a 9-year compulsory education, or even did not finish it, just as the present study showed. Among all 87 participants in this study, only 11 patients were 50 years of age and older, and the number of subjects with university or postgraduate education was only 9. Uneven data distribution would affect the result of regression analysis, which could be resolved by further study with a larger sample size. 

Some limitations in this study should be addressed. First, a degree of underascertainment is hard to avoid, and selection bias of the patients may have occurred because this was a single-center study. Second, we did not evaluate preoperative NEI VFQ-25 scores in patients undergoing ocular surgery to treat injury, since many subjects had had surgical treatment before they came to our hospital. Moreover, the impact of single or multiple surgeries on VFQ-25 was not explored. Thus we cannot evaluate the effect of surgery on the VR-QOL in chemical injury victims, especially those with multiple surgeries. This shortcoming could be resolved by further prospective investigation with a longer postoperative follow-up. 

In summary, chemical burn, a common ocular injury in China, has a significant and extensive impact on patients' visual function outcomes and vision-related QOL. Based on the results of the present study, the NEI VFQ-25 represents a useful and valid approach to evaluating vision function and vision-related QOL, which had correlation with BCVA in both the better- and the worse-seeing eye, injury classification of the less severely injured eye, and immediate irrigation after injury. It is of great significance to translate the visual acuity outcomes into areas of functioning and well-being that are more meaningful to patients, their families, and ophthalmologists. 

The authors thank Jian Gao for assistance in statistical analysis. 

Footnotes

 Supported in part by National Natural Science Research Grants 30872815 and 30901633, Key Clinic Medical Research Program, the Health Ministry of China (2010–2012), and Shanghai Excellent Leading Scholars Program, Science and Technology Commission of Shanghai Municipality Grant 10XD1401100.

Footnotes

 Disclosure: Q. Le, None; Y. Chen, None; X. Wang, None; Y. Li, None; J. Hong, None; J. Xu, None