The following techniques and investigations are used in further assessment of the eye:
Fluorescein instillation
Fluorescein is an orange red dye that absorbs blue light and fluoresces green. It stains the tear film and only penetrates defects in the epithelium of the eye, making lesions such as corneal abrasions, foreign bodies and ulcers far more visible.
The most effective preparations for diagnostic purposes are either a 1% solution or a moistened floret [18].
Contact lenses must be removed prior to instillation as they may become permanently stained.
Local anaesthetic instillation
Examination may be made easier in the painful eye if a topical local anaesthetic is instilled. Commonly used agents include:
Unfortunately, instillation of local anaesthetic drops into the eye is painful. Attempts to reduce pain by adding sodium bicarbonate to tetracaine increased pain
scores [19]. Research has shown that proxymetacaine is the topical local anaesthetic of choice, as it produces the lowest pain scores with an equivalent clinical
efficiency [20].
Learning bite
Proxymetacaine is the least painful local anaesthetic agent when instilled into the eye.
Eyelid eversion
Eversion of the eyelid is a simple but essential investigation to look for foreign bodies and conjunctival inflammation.
This video link demonstrates the technique.
Fundoscopy
The skill of fundoscopy is a difficult one to master but an important part of the assessment of the eye.
This video link demonstrates the basic technique.
There is no doubt that fundoscopy is far easier if the pupil has been dilated – the sensitivity of detecting diabetic retinopathy is twice as high through a dilated than a non-dilated pupil [21]. Tropicamide is a short acting mydriatic but there is a commonly quoted risk of precipitating acute glaucoma. A systematic review found this risk to be approximately 1:20,000 [22]. Even in several studies in high risk populations with chronic glaucoma, not a single patient developed acute glaucoma [22].
Learning bite
Fundoscopy is more sensitive when the pupil is dilated and the risk of precipitating acute angle glaucoma with 0.5% tropicamide is extremely small.
It is important to make sure that patients who have driven to the ED are aware that their vision will remain blurred until the tropicamide wears off and that they make alternative arrangements for getting home.
Slit lamp
Of all the skills needed to assess the eye, use of the slit lamp is the most demanding. Familiarity with the complex equipment may take some time and practise is essential.
This video link describes a basic technique.
Tonometry
Although not a standard technique used in the ED, due to the difficulties associated with formal intra-ocular pressure measurement with an application tonometer, the development of hand held devices (e.g. Tono-Pen) make this measurement easier and more accessible to the Emergency Physician.