Woman experiences myopic shift after blunt trauma
A 36-year-old woman was referred to the New England Eye Center, Tufts Medical Center, due to a persistent myopic shift in the left eye following trauma 3 months earlier.
She hooked her left upper lid on a plastic hook affixed to a wall. As she pulled away and toward the wall to unhook herself, she suffered blunt trauma to the posterior temporal side of the left globe. Medical and family histories were unremarkable. She was not taking any medication. Her previous refractive error was –1 D sphere in the right eye and –1.00 +0.75 × 150 in the left eye.
Source: Julia Ernst, MD, PhD, and Shilpa J. Desai, MD
On presentation, the patient’s best corrected visual acuity was 20/20 in the right eye and 20/200 in the left eye. Her new post-traumatic manifest refraction was unchanged in the right eye but changed to –3.75 +0.75 × 160 in the left eye. The pupils were equal and reactive to light and accommodation, and IOPs were within normal limits. The anterior segments were clinically normal.
Imaging
Dilated fundus examination showed myelinated fiber layers in both eyes and temporal choroidal bowing of contour in the left eye (Figure 1a). The fundus autofluorescence was normal (Figure 1b). OCT demonstrated temporal bowing of the sclera (Figure 2). B-scan confirmed temporal bowing of the left globe (Figure 3). MRI was negative for any orbital pathology except for relatively increased axial length on the left side. Axial length and refractive error of the left eye remained stable for 1.5 years after trauma with the following measurements: 25.95 mm at 5 months, 26.14 mm at 8 months, 26.05 mm at 13 months and 26.07 mm at 19 months.
What is your diagnosis?
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Myopic shift
Trauma to the eye can lead to myopia. It is ipsilateral and usually transient, resolving within weeks of injury. Transient traumatic myopia is thought to occur via several mechanisms involving ciliary spasm, anterior displacement of the lens-iris diaphragm, an increase in anteroposterior thickness of the crystalline lens and ciliochoroidal effusion (Ikeda and colleagues). Conversely, permanent or progressive myopic shift is reported due to axial length increase in children and young adults due to eye trauma, among other causes (Gradin and colleagues). The pathophysiology of this phenomenon in children is not well understood, and many factors might be involved. Reports on axial elongation following trauma in adults are scarce. We report a rare case of post-traumatic myopic shift associated with a unique change in the contour of the globe leading to axial elongation in an adult patient.
Discussion
Myopia is the most common eye disorder, yet its etiology remains elusive. It is hypothesized to result from the interplay between an individual’s genotype and environment (Cooper and colleagues). It usually stabilizes in adolescence, but it can also have onset in adulthood in which case it is commonly bilateral and associated with environmental risk factors such as near work (Al Messabi and colleagues).
Our patient developed an ipsilateral myopic shift following blunt trauma to her left eye. The refractive change was unlikely to be caused by anatomic changes in the ciliary body or crystalline lens, especially because these are usually transient and the anterior segment exam was unremarkable. Moreover, multimodal imaging revealed increased axial length in comparison to the unaffected eye and unique bowing of the sclera in the posterior pole. Axial length comprises anterior chamber depth, lens thickness and posterior chamber depth. Axial length is thought to be the main determining factor in refractive error. The patient’s fundus exam and imaging studies indicated that the elongation of the left eye was caused by anatomic changes in the posterior segment. They also demonstrated that the change in contour was not consistent with staphyloma.
Axial elongation of an eye due to trauma, surgery, aphakia or cataracts is well known in the pediatric population or young adults. The pathophysiology is hypothesized to be due to visual deprivation, IOP changes, laterality, amblyopia, multiple surgeries, IOL implantation or altered scleral rigidity (Vanathi and colleagues). Eye development is a complex and highly coordinated process that occurs mostly during the first 2 decades of life (Brown and colleagues). In our adult patient, ocular dimensions are not expected to be modified easily. Hence, it is likely that some other mechanism might be at play. Additionally, it appears that the axial length change occurred either immediately after blunt trauma to the globe or within the following 2 to 3 months, based on the patient’s records.
The timeline of events appears consistent with a traumatic break in Bruch’s membrane (BM) with a secondary axial length change. In the myopic eye, axial elongation occurs via a change of the eye shape from mostly spherical to ellipsoid prolate. It is accompanied by scleral and choroidal thinning, which is most marked in the subfoveal region. Interestingly, BM thickness remains stable while its surface and volume increase in the process (Jonas and colleagues). Hence, the BM grows during axial elongation in myopia in contrast to the sclera or choroid. Nevertheless, the sclera undergoes remodeling during our lifetime, which was demonstrated to influence the refractive properties and size of the eye. It is plausible that scleral remodeling could account for change in shape as well (Rada and colleagues). Axial elongation above 26 mm is associated with BM defects, which correspond to patchy areas of atrophy in myopic maculopathy, leading to retinal pigment epithelium changes and photoreceptor damage. It is worth mentioning that our patient’s retinal pigment epithelium, photoreceptors and retina appeared healthy and unaffected, based on multimodal imaging. There was also no gross evidence of a BM break. Another possible explanation for changes in the contour of the globe and its axial elongation could be a post-traumatic inflammatory process. It has recently been shown that there might be a connection between low-grade or subclinical inflammation and highly myopic eyes (Yuan and colleagues). In summary, in pathologic myopia, these phenomena are associated with nontraumatic axial length increase. Hence, arguably, they are not relevant to post-traumatic ocular size changes. However, what they imply is that the eye has the potential to remodel in response to many factors, including trauma.
There are only a few reports of axial length elongation in association with trauma in adults. Shekhar and colleagues studied the effects of penetrating and blunt trauma on ocular axial length. Whereas penetrating trauma can lead to significant axial elongation of the eye, blunt trauma has much smaller effects. Given the relative paucity of similar cases in the literature, we hope this case provides a useful example of axial length elongation after blunt trauma.
- References:
- Al Messabi SS, et al. Am J Ophthalmol Case Rep. 2020;doi:10.1016/j.ajoc.2020.100941.
- Brown DM, et al. Exp Eye Res. 2022;doi:10.1016/j.exer.2022.109071.
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- Gradin D, et al. J Cataract Refract Surg. 2008;doi:10.1016/j.jcrs.2008.05.035.
- Ikeda N, et al. Ophthalmology. 2002;doi:10.1016/s0161-6420(01)00995-2.
- Jonas JB, et al. J Clin Med. 2023;doi:10.3390/jcm12041317.
- Rada JA, et al. Exp Eye Res. 2006;doi:10.1016/j.exer.2005.08.009.
- Shekhar M, et al. TNOA J Ophthalmic Sci Res. 2019;doi:10.4103/tjosr.tjosr_116_18.
- Vanathi M, et al. J AAPOS. 2002;doi:10.1067/mpa.2002.123658.
- Yuan J, et al. Sci Rep. 2019;doi:10.1038/s41598-019-39652-x.
- For more information:
- Edited by William W. Binotti, MD, and Julia Ernst, MD, PhD, of New England Eye Center, Tufts University School of Medicine. They can be reached at william.binotti@tuftsmedicine.org and julia.ernst@tuftsmedicine.org.
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