Katarzyna Pikulska
Medical University of Warsaw
OCULAR CONCUSSION
Etiology
Concussion cataract. It occurs mainly due to imbibition of aqueous and partly due to direct mechanical effects of the injury on lens fibres.
Concussion changes at macula. Traumatic macular oedema is usually followed by pigmentary degeneration. Sometimes, a macular cyst is formed, which on rupture may be converted into a lamellar or full thickness macular hole.
Characteristical signs
It may assume any of the following shapes:
- discrete subepithelial opacities are of most common occurrence.
- early rosette cataract (punctate). It is the most typical form of concussion cataract. It appears as feathery lines of opacities along the star-shaped suture lines; usually in the posterior cortex.
- late rosette cataract. It develops in the posterior cortex 1 to 2 years after the injury. Its sutural extensions are shorter and more compact than the early rosette cataract.
- traumatic zonular cataract. It may also occur in some cases, though rarely.
- diffuse (total) concussion cataract. It is of frequent occurrence.
- early maturation of senile cataract may follow blunt truma.
The opacity may reduce the visual acuity directly or produce an uneven change in the refractive index of the lens causing irregular astigmatism with light scatter and sometimes monocular diplopia not correctable by spectacles. Patients may benefit from wearing a peaked cap in bright sunlight in order to minimize disability from glare. These symptoms may precede any obvious opacity and a progressive change in refractive error (typically an increase in myopia in the case of nuclear sclerosis which gradually advances to become a brownish nuclear cataract) may suggest incipient cataract. Colour vision sensitivity and discrimination may be reduced.
Work-up
A blurred fundus view with the direct ophthalmoscope is a useful indicator of clinically significant cataract. Greyish white opacities can be seen in oblique illumination by a torch or by a slit lamp in optical section. They are visible as dark areas in silhouette against the red reflex in the pupillary area when viewed with the ophthalmoscope at a distance of about 15 cm. These opacities are also revealed during retinoscopy.
Differential diagnose
Senile cataract, choroidal rupture, ectopia lentis, angle recession in glaucoma, hyphema, corneoscleral laceration, sudden visual loss.
Other problems to be considered: globe rupture, orbital fractures, retinal detachment, secondary glaucoma, traumatic optic neuropathy
Treatment
Principles of cataract surgery
The removal of the opaque lens is termed a cataract extraction and this renders the eye aphakic.
Pre-operative assessment
Projection to light. In the presence of a dense cataract with a limited view of the fundus, a guide to the integrity of the visual pathways is obtained by testing 'projection to light'. The patient is asked to point to the source of light when a beam is shone on the eye from different directions. Even when the projection to light is poor, cataract extraction may be indicated in some circumstances, and very exceptionally even if light perception is absent, to prevent the complications of hypermaturity. Prior to dilating the pupils it is important to assess pupil reflexes. A relative afferent pupillary defect is indicative of optic nerve dysfunction or extensive retinal disease.
Surgical techniques
Cataract extraction is carried out using an operating microscope either by the extracapsular method in which all the lens capsule remains intact except a central anterior capsular disc, or by the intracapsular method by removal of the entire lens including its capsule. Certain complicated cataracts may require lensectomy .
The great advantage of the extracapsular technique is that the posterior capsule and the zonule not only support the vitreous but the capsular bag will usually contain the posterior chamber lens implant. While the main disadvantage of the extracapsular method was originally the opacification of the posterior part of the capsule which then required surgical discussion or "needling" (incision with a needle type of knife), this is now treated with a brief high energy pulse of the Nd YAG laser with the patient sitting at the slit lamp microscope, although in the case of particularly thick capsules, it may still be necessary to carry out a surgical posterior capsulectomy. However, the risk of posterior capsule opacification is now rarer, particularly when using certain types of lens implant.
In the intracapsular operation there is always a risk of a capsular tear or vitreous loss. In addition, although anterior chamber implants were sometimes used, they were subject to complications and do not compare with posterior chamber implants in the capsular bag. The most highly developed technique of extracapsular extraction will here be first described but the earlier extracapsular methods and the intracapsular technique are subsequently outlined because they may have practical advantages where surgical facilities are less developed as they do not require such refined equipment.
Follow up
Cataract extraction, athough exacting, is now one of the most successful forms of surgical intervention. Possible complications however include vitreous loss due to per-operative posterior capsule rupture, haemorrhage, infection, uveitis, raised intraocular pressure, flat anterior chamber, macular oedema, retinal detachment and corneal oedema.
Retinal haemorrhages. These are quite common following concussion trauma. Multiple haemorrhages including flame-shaped and preretinal (subhyaloid) D-shaped haemorrhage may be associated with traumatic retinopathy.
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