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 Table of Contents  
ORIGINAL ARTICLE
Year : 2019  |  Volume : 57  |  Issue : 1  |  Page : 12-16

Ocular axial length changes following trauma: Blunt versus penetrating


Cataract and IOL Clinic, Aravind Eye Hospital and Post Graduate Institute of Ophthalmology, Madurai, Tamil Nadu, India

Date of Web Publication10-Jun-2019

Correspondence Address:
Dr. Hemant Sonawane
Aravind Eye Hospital and Post Graduate Institute of Ophthalmology, Madurai, Tamil Nadu
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/tjosr.tjosr_116_18

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  Abstract 


Aims: This study aims to analyze the effect of penetrating and blunt trauma on ocular axial length. Settings and Design: This is a retrospective study. Subjects and Methods: Seventy cases of unilateral ocular trauma visited between January 2012 and January 2015. Blunt and penetrating groups were formed based on the nature of injury. Mode, nature, age at injury, and presenting age were noted. Best-corrected visual acuity, axial length, keratometry, and biometric values of both eyes were documented. Factors statistically associated with changes in axial length in traumatic eyes were measured. Results: Mean axial length in penetrating trauma group was 25.31 mm (standard deviation [SD]: 1.75), and in blunt trauma group was 24.05 mm (SD: 1.13). Using regression analysis, if the axial length in control eye increases by 1 mm, then in the traumatic eye, it increases by 1.34 mm. Similarly, age at injury, penetrating trauma and longer duration between injury and presentation were statistically significant factors associated with increase in axial length in the traumatic eyes. Conclusions: Elongation of the eyeball is significantly greater in penetrating trauma than in blunt trauma. Trauma at a younger age; presentation at a later age and penetrating type of trauma are statistically significant factors associated with an increase in axial length in the traumatic eye.

Keywords: Axial length, blunt trauma, penetrating trauma


How to cite this article:
Shekhar M, Sonawane H, Aravind H. Ocular axial length changes following trauma: Blunt versus penetrating. TNOA J Ophthalmic Sci Res 2019;57:12-6

How to cite this URL:
Shekhar M, Sonawane H, Aravind H. Ocular axial length changes following trauma: Blunt versus penetrating. TNOA J Ophthalmic Sci Res [serial online] 2019 [cited 2019 Sep 15];57:12-6. Available from: http://www.tnoajosr.com/text.asp?2019/57/1/12/259874




  Introduction Top


The human eye is a very well programmed organ wherein the refractive elements within it exhibit a regulated growth pattern.[1] The developing eye adjusts the growth of its refractive components to achieve “emmetropization.” Animal studies have shown axial elongation following visual deprivation; with certain reservations, most authors believe it can help explain genesis of myopia in humans.[2],[3],[4],[5],[6],[7]

Many hypotheses have been proposed to explain transient myopia after blunt eye trauma, such as ciliary spasm, uveal (cilia-choroidal) effusion, anterior displacement of the lens–iris diaphragm, and an increase in anteroposterior thickness of the crystalline lens.[8] Few studies have been directed to examine the effect of surgical delay in young adults with chronic traumatic cataract and the effect of infantile traumatic cataract on axial elongation.[1],[2] A trend of increase in ocular axial length and myopic shift in refraction has been observed to occur following pediatric cataract extraction.[9],[10],[11],[12],[13],[14],[15]

Out of the various presumed factors responsible for the changes in the axial length of the human eye, posttraumatic changes in axial length is scarcely studied in younger and adult age groups.[2],[3],[4],[5],[6] Even though the true cause of axial elongation remains elusive, many factors such as trauma, visual deprivation, surgery at an early age, and multiple surgeries have been postulated. After reviewing the existing literature, we tried to study and correlate the long-term effects of trauma on axial length with the nature of trauma, taking a larger sample size relative to other studies. The analysis of two different ocular trauma groups was done by grouping cases according to their nature of trauma and doing intra- and inter-group comparisons. Our article thus purposes to study the effect of nature of trauma on axial length and its clinical relevance in the management of the same.


  Subjects and Methods Top


This retrospective study was carried out at the Cataract Clinic, Aravind eye hospital, Madurai. The study protocol was conducted according to the principles described in the Declaration of Helsinki, and Institutional Review Board/Ethics Committee approval was obtained. The selection was done from outpatient cases visited between January 2012 and January 2015. Based on the relevant history and medical records, 70 cases with presumed healthy eyes before trauma were selected retrospectively. The contralateral normal eye served as a control for the study eye. Patients with only unilateral axial length record, duration of trauma <1 year and those with bilateral trauma and congenital cataract were excluded from the study. Two groups were formed based on the nature of injury (blunt or penetrating). Birmingham Eye Trauma Terminology System was used to define blunt and penetrating trauma.[16] A penetrating trauma was defined as laceration by a sharp object (there is only an entrance wound and no exit wound), for example, thorn, nail, and pen. A blunt trauma was defined as a closed globe injury caused by a blunt object (there is no entrance or exit wound), for example, cricket ball and closed fist.

In each case, details of history including age at injury, mode, nature, and interval since the injury was documented and previous medical records were properly analyzed. Parameters including best-corrected visual acuity (BCVA), refractive error, intraocular pressure (IOP), keratometry and biometric values (IOLMaster 500, Carl Zeiss Meditec) of both eyes were documented. Detailed anterior and posterior segment examination findings were noted.

Statistical analysis

Mean (standard deviation [SD]) or Frequency [Percentage]) was used to describe summary data. Student's t-test or Mann–Whitney U-test was used to compare means between groups. Chi-square test was used to assess the association between categorical variables. P < 0.05 is considered as statistically significant. All statistical analysis was done in STATA 11.1 (Texas, USA). Multiple regression analysis was used to determine factors associated with increasing axial length in traumatic eyes. Fellow eye axial length (in mm), age at injury, type of injury, and duration of presentation since trauma were included in the analysis. All variables were significantly associated in the univariate and multivariate model.


  Results Top


Of the 70 cases, 47 were in penetrating trauma group (27 males and 20 females) and 23 (19 males and 4 females) in blunt trauma group. Mean age in penetrating trauma group was 34.17 years (SD: 13.47) and blunt trauma was 34.70 (SD: 16.75) [Table 1]. Of the 70 cases, 14 presented with traumatic cataract, 43 with pseudophakia, and 13 patients with aphakia; 14 (20%) patients were amblyopic. Twenty-four cases (34%) presented with BCVA <6/18 which was due to traumatic cataract, corneal scars, and fundus pathology. The duration between trauma and presentation ranged between 1 and 53 years. Forty seven cases suffered penetrating trauma, 23 cases suffered blunt trauma. The difference in two groups was not statistically significant considering both age (P = 0.888) and gender (P = 0.037). The difference between mean K1 and K2 was more in the penetrating group − 2.36D (SD: 1.82) as compared to blunt trauma group − 0.82D (SD: 0.28). There was no statistical difference between two trauma groups in both K1 (P = 0.5593) and K2 (P = 0.0983) readings.
Table 1: Demographic distribution of cases among trauma groups

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The mean axial length of the traumatic eye was 25.31 mm (SD: 1.75) and 24.05 mm (SD: 1.14) in penetrating trauma group and blunt trauma group, respectively. In both groups, axial length was found to be more in the traumatic eyes compared to control eye (penetrating trauma: P < 0.001 and blunt trauma: P = 0.0123). The difference in axial length between traumatic eyes of two groups (penetrating > blunt) was statistically significant (P = 0.0006). Comparing age at injury with axial length; mean axial length in penetrating trauma group ≤15 years was 25.81 mm (SD: 1.78) and in >15 years, it was 24.19 mm (SD: 1.38) (P = 0.0061); while in blunt trauma group ≤15 years was 24.24 mm (SD: 1.43) and in >15 years was 23.86 mm (SD: 0.98) (P = 0.465). Overall 36 (51.42%) patients suffered trauma at ≤15 years of age and 27 (38.57%) at >15 years of age. In the remaining 7 (10%) patients, trauma occurred early in life, but the exact age at injury was not known [Table 2]. The earlier the age at injury, greater the axial length in the injured eye (penetrating trauma > blunt trauma) (P = 0.0003). The longer the duration between injury and presentation, greater the axial length in the traumatic eye, as well as the difference in axial length between two eyes (penetrating trauma > blunt trauma) [Figure 1]a and [Figure 1]b.
Table 2: Distribution of axial length in traumatic eye according to age at injury

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Figure 1: (a) Scatter plot comparing axial length with the duration between injury and presentation. (b) Scatter plot comparing difference in axial length between traumatic and control eye with the duration between injury and presentation

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Using regression analysis of the data, if the axial length in control eye increases by 1 mm then in traumatic eye, it increases by 1.34 mm (β =1.34, 95% confidence interval [CI]: 0.96–1.76, P < 0.001) when other variables held constant. Similarly, age at injury ≤15 years (β = 0.88, 95% CI: 0.34–1.42, P = 0.002), penetrating trauma (β = 0.90, 95% CI: 0.33–1.47, P = 0.002), and duration from injury to presentation (β = 0.98, 95% CI: 0.42–1.53, P = 0.001) were statistically significant factors associated with increase in axial length in the traumatic eye [Table 3].
Table 3: Factors associated with increase in axial length in trauma cases

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  Discussion Top


In our study, overall 47 (67.14%) patients had more than 1 mm elongation in their injured eye compared to the other (control) eye. The mean difference between the injured eye and fellow eye was 0.72 mm [SD: 0.744] (−0.18–2.91 mm) in blunt trauma group and 2.23 mm [SD: 1.62] (−2.19–6.97 mm) in penetrating trauma group. Elongation of the eyeball is significantly greater in penetrating trauma than in blunt trauma. There are various studies that report axial elongation following visual deprivation due to various causes.[2],[6],[10],[13],[17],[18] The comparative evaluation of our data with previously published data is shown in [Table 4]. The findings in our study are consistent with other studies showing that there is a significant elongation of the eye following trauma.
Table 4: Comparative evaluation of data with previous studies

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Multiple mechanisms could be possible for progressive ipsilateral elongation. These include trauma, age at surgery, duration and severity of visual deprivation, amblyopia, IOP changes, change in scleral rigidity and multiple surgeries.[13] In our study, it is possible that both trauma and vision deprivation are confounding factors for axial elongation. Despite the association of various factors with axial elongation in adult eyes, the actual cause remains elusive. Our study also reflects that younger the age, the greater the magnitude of axial length elongation [Table 2] and [Figure 1]a and [Figure 1]b.

Furthermore, the induction of traumatic cataract usually requires a very forceful blow to the eye, and it may be the trauma itself that starts the elongation process of the globe, or it may be complementary to visual deprivation.[6] The existence of certain growth factors which may modulate the growth of the adult eyeball after trauma has also been postulated.[19],[20],[21] We tried to reliably extract the data regarding the interval from the injury to the time of presentation/surgery in most of the cases using clinical history and medical records. In addition, regression analysis of the data proved that increase in axial length in the traumatic eye is greater compared to the normal (control) eye. Hence, we were able to establish a correlation between the degree of elongation and the interval between trauma and surgery statistically. Certain studies depict that there is no direct linear correlation between the onset of trauma and degree of elongation of an eye.[6] However, the assumption that the inter-ocular axial length difference was zero before trauma may not be valid in all cases.

Among the cases, despite IOL implantation at an early age (seven cases) with good visual recovery, there was significant axial myopia. Therefore, we can deduce that the nature and the age at injury are strongly related to the axial elongation along with visual deprivation. Similarly, Vanathi et al. reported the occurrence of unilateral progressive axial myopia ipsilaterally in a retrospective analysis of 12 children (age group 4–14 years) following uniocular cataract surgery, postulating trauma or multiple ocular surgeries as predisposing factors.[13] Sorkin and Lambert studied longitudinal changes in axial length in pseudophakic children (3–9 years) and concluded that eyes with traumatic cataracts experienced more axial elongation than eyes with developmental/congenital cataracts (0.97 vs. −0.01 mm; P = 0.03).[15] Leiba et al. demonstrated a tendency toward greater axial lengthening in pseudophakic eyes of children when compared with their nonoperated eyes without any significant difference between traumatic and congenital cataracts.[12] Similarly, Crouch et al. showed that there is no statistically significant difference in refractive change when comparing amblyopic to nonamblyopic eyes or traumatic to nontraumatic cataracts.[21]

Hoevenaars et al. studied children <12 months of age and experienced higher myopic shifts and a larger mean rate of refractive change per year compared with older children proving that age at surgery and laterality are factors to consider when deciding which IOL power to implant in children.[22] Enyedi et al. demonstrated an increasing trend towards postoperative myopia in pediatric patients undergoing intraocular lens implantation.[11] This myopic shift was being greatest in younger age groups and persistent until at least 8 years of age, further showing that there is much variability in the postoperative refractive changes, and predicting exactly when refraction will stabilize for an individual patient is difficult.

Griener et al. showed that cataract extraction and IOL implantation may reduce axial growth in infantile eyes.[23] Similarly, Lambert et al. studied axial elongation following cataract surgery during the 1st year of life in the Infant Aphakia Treatment Study and concluded that at baseline, eyes with cataracts were shorter than fellow eyes.[24] The change in AL was smaller in operated eyes treated with a CL than in operated eyes treated with an IOL but was not significantly related to age at surgery.

VanderVeen et al. reported in Infant Aphakia Treatment Study that short axial length (<18 mm) correlates with higher predictive errors (PE) after IOL placement in infants.[25] They reported that Holladay 1 and SRK/T formulae gave good results and had the best predictive value for infant's eyes, highlighting the importance of axial length and proper IOL formulae for calculations. It is, therefore, important to consider age, proper formulae, and biometry to calculate IOL power with minimal PE in infants and young patients with penetrating trauma.

One of the limitations of the present study is the assumption that the two eyes of each patient were similar before the injury. It may be possible that the injured eye was myopic before the injury hence more susceptible to injury due to poor vision caused by nuclear cataract or myopia itself.[26],[27] We could not find any correlation between IOP with axial length elongation as the study is retrospective and IOP at the time of injury was not available. The time interval between the age at which injury occurred to the time of presentation was not accurately available in all cases. There is much variability in the postoperative refractive changes and predicting exactly when and where the refraction will stabilize for an individual patient is difficult; hence, predicting the appropriate IOL power with any degree of accuracy is quite difficult.


  Conclusions Top


Trauma leading to visual deprivation may cause unilateral axial elongation. Younger the patient when trauma occurred, greater the magnitude of axial length elongation. Longer the duration between age at trauma and time of presentation, greater the axial length of the traumatic eye. Elongation of the eyeball is significantly greater in penetrating trauma than in blunt trauma. Rapid rehabilitation of injured eyes is absolutely essential to minimize the duration of visual deprivation. It is difficult to predict exactly the amount of axial length elongation following trauma and or cataract surgery hence regular follow-up with proper refractive correction will help to prevent amblyopia in such cases.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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2.
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Zhang Z, Li S. The visual deprivation and increase in axial length in patients with cataracts. Yan Ke Xue Bao 1996;12:135-7.  Back to cited text no. 10
    
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13.
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Sorkin JA, Lambert SR. Longitudinal changes in axial length in pseudophakic children. J Cataract Refract Surg 1997;23 Suppl 1:624-8.  Back to cited text no. 15
    
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Lambert SR, Lynn MJ, DuBois LG, Cotsonis GA, Hartmann EE, Wilson ME, et al. Axial elongation following cataract surgery during the first year of life in the infant aphakia treatment study. Invest Ophthalmol Vis Sci 2012;53:7539-45.  Back to cited text no. 24
    
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    Figures

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    Tables

  [Table 1], [Table 2], [Table 3], [Table 4]



 

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