Examination of the Eyes
Examination of the eyes involves looking at the external aspect, such as the lids, lashes, sclera, conjunctiva and cornea for a healthy appearance.
- The lids should be symmetrical and move normally, up and down.
- The lashes should not turn inwards and scratch the eye.
- The sclera and conjunctiva should be white and not inflamed.
- The cornea should not be scratched or ulcerated (this will show up as a green stain with a 1% fluorescein dye).
- The anterior chamber should be clear.
- The pupils should be equal and react, and, with a normal lens, the pupil should appear black.
Ophthalmoscopy
An ophthalmoscope is a hand held instrument (with a magnifying light source), which enables the examiner to look at the eye from the cornea, at the front, through the pupil, lens, and vitreous, to the retina at the back. In examining the retina, the condition of the retina itself, the blood vessel supply, the optic disc and the macula (the point of sharpest vision) can be seen. Many changes due to disease can be visualised, for instance, diabetes, high blood pressure (hypertension) macular degeneration, retinitis pigmentosa, tumour involving the eye, haemorrhage and detached retina.
Ideally, the ophthalmoscope is used in a darkened room with the facility to dilate the pupils, if necessary. The retina may not be easily seen, if a cataract is present.
Tonometry
Tonometry measures the “eye pressure” or pressure of the aqueous humour in the anterior segment of the eye. This is important in the detection and treatment of glaucoma. It can be done in three ways:
- Usually at the optician’s an “air - puff tonometer” (non - contact with the eye surface) is used, and all the patient feels is a puff of air on the white of the eye.
- The ordinary tonometer involves the use of a hand - held measuring instrument (tonometer), which is gently put onto the surface of the anaesthetised eye (using drops of local anaesthetic to numb the surface of the eye).
- Applanation tonometry is used in conjunction with a slit - lamp and the cornea is visualised at the same time as a tonometer is placed on the anaesthetised cornea.
The normal eye pressure is 8-12 mm Hg (millimetres of mercury).
Ultrasound
Ultrasound examination of the eye is useful when the retina cannot be easily visualised for instance, if there is a cataract or haemorrhage blocking the visual access. It is also used to demonstrate the presence of tumours, the blood supply to the eye and the thickness of the cornea. Ultrasound is non - invasive and works by painlessly bouncing sound waves off the internal structure of the eye.
