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Today, keratoplasty is one of the world's most widely practiced human organ and tissue transplantation methods. Compared with the adult's cornea, the child's cornea is thinner, less rigid and more elastic, presenting a wide range of challenges preoperatively, intraoperatively, and postoperatively.1 Both rejections and complications are more commonly seen in pediatric keratoplasty,2 leading to a higher failure rate. Prior to 1970, corneal transplantation was considered to be contraindicated3-5 because of a less firm sclera and the forward displacement of the lens-iris diaphragm in pediatric anterior segment surgery.
With the improvement of surgery techniques in the last 20 years, the success rate of pediatric keratoplasty has increased tremendously. However, to the best of our knowledge, only a few studies using pediatric penetrating keratoplasty have been performed in China which has the largest population in the world.
The present multicenter study retrospectively analyzed the records of 156 pediatric keratoplasties performed in Shanghai from January 1st, 2003 to January 1st, 2007, in order to discuss the characteristics of corneal transplantation in Chinese children.
METHODS
Patients
In this longitudinal, retrospective study, the records of all cases of pediatric penetrating keratoplasty were reviewed. The patients underwent surgery in four tertiary ophthalmic units with the authority of the eye bank in Shanghai. Patient and surgical information was collected from surgeons at the appropriate times.
Survey methods
By reviewing the patients' medical records, information of the history, clinical examinations, clinical and pathological diagnosis, and outcome of keratoplasty of each patient was gathered. Follow-up data were collected until 1 year postoperatively. The indications for pediatric keratoplasty are presented in Table 1. The diagnostic classification system developed by Stulting et al3 was used as a comparison with other published reports. Indications were classified into three groups: congenital, acquired non-traumatic, and acquired traumatic conditions.
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Table 1. Age and sex distribution by indication for each diagnostic group |
Statistical analysis
The SPSS13.0 software package (SPSS Inc., Chicago, USA) was used to analyze the data. A chi-square test or non-parametric test was used to compare the differences between two groups. The level of statistical significance was P <0.05.
RESULTS
Patients' data
A total of 156 eyes from 149 pediatric patients up to 15 years of age underwent penetrating keratoplasty, and were enrolled in this 5-year study. The median age at surgery was 9 years with an interval quartile range of 6-12 years. Patients' age ranged from 16 days to 14 years. Both eyes were operated in seven cases only. The sex distribution involved 62% (n=97) boys and 38% (n=59) girls, which was similar to the report by Sharma et al.6
Indications for pediatric penetrating keratoplasty
The classification by Stulting et al3 was used to group the participants into non-traumatic, acquired traumatic, and congenital indications. The acquired non-traumatic group included 45.5% (n=71) of patients while 30.8% (n=48) of patients contributed to the acquired traumatic group, and the congenital group included 23.7% (n=37) of participants. These groups were further subdivided into specific indication groups as shown in Table 1. The indications for different age groups (using stratified 5 year intervals) are shown in Table 2. Scarring after keratitis (29.5% of the total number of cases, n=46) was the most common indication in the acquired non-traumatic group, traumatic corneal scar (19.2% of the total number of cases, n=30) was the most common in the acquired traumatic group, and congenital corneal opacity (19.2% of the total number of cases, n=30) was the most common in the congenital group. Interestingly, 8 cases underwent corneal transplantation due to graft rejection.
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Table 2. Indications for Pediatric penetrating keratoplasty for different age groups |
Distribution of age and sex by indications for penetrating keratoplasty
The age and sex distribution for each diagnostic group are presented in Table 1. Most patients were 7 to 14 years old. There was no significant association between preoperative diagnosis and sex. The chi-square value of the test performed between the congenial group and the total number of cases was 0.827 (P=0.363). Moreover, that between the acquired non-traumatic group and the total number of cases was 0.402 (P=0.526); and was 2.659 (P=0.103) for the acquired traumatic group.
Outcome of pediatric penetrating keratoplasty
In children, vision assessment can be difficult. Documentation of the changes in best-corrected snellen visual acuity (BCSVA) on an E-chart was the preferred method of assessment if the child was cooperative. If vision assessment was not possible because the child could not resist closing his/her better eye, or increased ambulation, and reached out for things, subjective methods were used. Because 21 patients were uncooperative and 23 patients were lost during follow-up, BCSVA was reported in 72% (n=112) of cases only, and the outcomes for postoperative visual acuity in this series of pediatric penetrating keratoplasties are shown in Table 3. Vision outcome was significantly better for keratoplasty 1 year postoperatively compared to preoperative visual acuity (P<0.001). Of all patients, 13% (n=14) achieved a BCSVA of 6/18 or better. The relationship between the indications and vision outcomes was unavailable because most uncooperative patients' etiology involved congenital corneal opacity. Therefore, graft survival for each diagnostic group was used for analysis, and is presented in Table 4. None of the indications was associated with a higher rate of failure after 1 year follow-up (Table 4).
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Table 3. Outcomes of pediatric penetrating keratoplasty |
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Table 4. Relationship between indications and graft survival |
DISCUSSION
The cornea in children is more flexible and less rigid than in adults. Examinations before and after operation, medical treatments, and nursing procedures are all more difficult in children than in adults. Because of the anatomical and physical characteristics of a child's sclera, the crimpling of the eyeball during operation, forward displacement of the lens and iris diaphragm, as well as synechia often occur in pediatric keratoplasty.7 It should be emphasized that the majority of infants and young children are hyperopic, have a shallow anterior chamber, and a narrow and undeveloped iridocorneal angle. Furthermore, congenital corneal opacities are occasionally concomitant with a smaller eyeball and cornea.8,9 Therefore, iris anterior synechia and intraocular pressure elevation, both being high-risk factors of graft rejection, occur more frequently after pediatric keratoplasty.10,11
In the present study, 156 consecutive cases in eastern China were included in a 5-year multicenter cooperation study. Analysis of these patients provided an accurate representation of corneal diseases and keratoplasty in Chinese children. To the best of our knowledge, this study is the first multiple centre study in China. However, the present series of the participating patients who were managed with keratoplasty to improve visual acuity was limited in number; therefore, it cannot directly provide accurate outcome predictions for pediatric keratoplasty. On the other hand, this study provided follow-up data for a number of different indications. Eight grafts have been lost due to irreversible rejection. This indicates that dedicated parental involvement and intense ophthalmic care are essential for the maintenance of pediatric corneal grafts.
Congenital corneal opacity and corneal dystrophies are the major indications for pediatric keratoplasty in developed countries.12-16 However, scarring after keratitis and perforation caused by trauma were the leading reasons for performing penetrating keratoplasty in children in our study. This difference was probably caused by the lack of adequate management at the primary health care level, resulting in continuous exacerbation of the disease.
Various indications for pediatric keratoplasty have been reported by different literatures.1,6,14 Table 5 provides a comparison between the present study and other several important reports published in the 21st century. All studies presented used an age criterion of 14 years or younger. The proportion of keratoplasties which was performed for congenital indications was 16%–34%, 46%–74% for acquired non-traumatic, and for acquired traumatic 10%–31% indications. Here, in particular, the proportion of keratoplasties performed for acquired non-traumatic indications (46%) was significantly lower than that in other reports. However, that of acquired traumatic indications was much higher than that in most previously published reports.
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Table 5. Indications for pediatric keratoplasty reported from different literatures |
The results of this study were mostly obtained from school-age children, particularly boys, who are more active and curious. In addition, boys tend to have poorer self-protection skills, and less awareness of danger. These may be among the main reasons for corneal injury. Therefore, more attention should be paid to health education for school-age children.
Scarring after keratitis was the most common acquired non-traumatic indication in this study, accounting for 30% of all keratoplasties. This was notably higher than that of other published reports.17,18 More emphasis should be taken on aggressive antibiotics medications, appropriate surgery time, and proper treatment of postoperative complications.19,20 The use of medications in children, especially those without a clear pathogen diagnosis, should be considered thoroughly. Our study also highlighted the importance of infectious keratitis, which is not only the most common indication but also causes most of the graft failures in children in China.
In the current study, there was no significant difference in graft survival rate among the groups. More importantly, vision outcome after corneal transplantation was significantly better. Our series showed that prolonged corneal graft survival can be achieved in childhood.
In conclusion, our study provided valuable information in relation to pediatric keratoplasty in Shanghai. In addition, we highlighted the importance of scarring after keratitis and traumatic corneal scars in children corneal blindness. We also found that vision outcome after corneal transplantation in Chinese children is significantly better than pre-operation status. Overall, corneal graft survival can be achieved in childhood.
REFERENCES
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