My patient has just told me he was hit in his left eye by something when watching his work colleague hammering a steel ball bearing. He says it happened a few months ago but is vague and he did not seek a medical opinion because he could see well and the mild discomfort he felt at the time dissipated. My examination reveals that the left eye pupil is misshapen when compared to the right, posterior synechiae (patchy and intermittent adherence of the rear surface of the iris to the front surface of the crystalline lens) in the left eye and a reduction in foveal sensitivity in the left eye on visual fields testing; 27 dB right eye and 16 dB left eye with good reliability indicators. Best-corrected visual acuity is 6/6 in each eye. The external left eye is white and quiet and intraocular pressure is similar and in the normal range for each eye. What is going on?
Ocular trauma is one of the most commonly encountered eye issues with outcomes that range from decreased visual acuity to blindness and even enucleation. The incidence of ocular trauma has increased with global industrialisation. Ocular trauma is common despite the anatomic and functional protective mechanisms of the visual system. The orbital rim prevents many direct injuries from affecting the eye, and reflex closure of the lids aids in insulating the globe. The upward rotation of the eye in response to a sudden stimulus and the cushioning effect of the retrobulbar fat also acts as protection. In spite of these facts and the development of protective eyewear, the incidence of eye injuries remains high.
The key factors for this patient are the impact of a piece of or a whole ball bearing to his left eye, a distorted pupil, posterior synechiae (indicating a past or current inflammatory process), reduced foveal sensitivity (even though visual acuity is good) and that he has not been examined by an ophthalmologist. The real danger here is that a piece of the ball bearing may have entered the eye. Steel contains iron and iron inside the eye will eventually cause ocular siderosis.
In the eye, iron reacts with carbon dioxide to eventually form iron oxide. This can eventually lead to retinal degeneration. Other clinical features include cataract, rust-coloured anterior subcapsular deposits, iris heterochromia (affected side is darker), pupillary mydriasis. There is a potential for open-angle glaucoma. If the cataract and foreign body are removed and there is no macular trauma, the visual prognosis is excellent.
This patient deserves further investigation by an ophthalmologist (scleral indentation fundoscopy, CT scan and/or X-ray). It is likely that he has suffered a penetrating injury of the left eye and he is now in danger of ocular siderosis and the sequela that come with that condition.