Eye exams: tests and examinations

Eye examination: the basic diagnostics

The physical examination is usually performed with the patient seated:

• Externally visible signs of illness  (inspection)  are, for example, redness, increased tears and corneal injuries.
• The doctor can evaluate foreign bodies or changes under the eyelid by folding the eyelid over with a spatula or cotton swab  .
• If there is a suspicion of an infection, he can take a  swab  (from the conjunctiva,  cornea  or vitreous body) with a cotton swab and have it examined for pathogens in the laboratory.
• In rare cases, a  blood test may also be  necessary.
• During the tactile examination  (palpation)  , the doctor presses his fingertips lightly on the closed eyeballs and can thus roughly check the intraocular pressure in a lateral comparison (which can be increased, for example, in the case of glaucoma  or  due to a  bruise  ).

functional tests of the eyes

Depending on the symptoms, vision, reaction, the shape and symmetry of the pupils, and the mobility of the eyes (and their muscles) can be examined. In the following, we will introduce you to the different types of eye examinations in more detail.

Eyesight test

This includes examining visual acuity (visual acuity test), the field of vision, i.e. the area that can be surveyed when looking in one direction, and color or dark vision.

• Vision test:  They are almost a symbol of the ophthalmologists – the boards with letters, numbers, ticks or pictures in different sizes. This can be used to determine short-sightedness or far-sightedness and their extent.
• Visual field test:  Doctor and patient sit opposite each other at the same height. Then the patient has to look in the doctor’s direction with both or one of his eyes (and cover the other) and determine the number of fingers held by him at different heights and directions or say when the finger is seen.
•  Color Vision: Color blindness and color vision  deficiency can be identified using certain charts on which brightly colored spots of color form patterns that only those who can see colors can recognize as numbers.

assessment of the pupil

The normal pupil narrows when there is light, even if it is not illuminated directly, but only the one on the opposite side. If this reflex does not work properly, this indicates certain diseases of the optic nerve, the brain or paralysis of the eye muscles.

Pupillary changes such as asymmetry, widening or narrowing can also be caused by inflammation, medication or other pathological causes. The pupil is assessed as part of the ophthalmoscope (see below).

Assessment of eye mobility

The position of the eyes in relation to one another, their mobility and the simultaneity of movements are functions that are examined particularly when squinting and seeing double images. To do this, the doctor first assesses whether the light reflections on the cornea are symmetrical, then performs a cover-and-reveal strabismus test (covering one eye and seeing how the other responds), and then has the patient look in nine different directions (by covering one finger there).

Ophthalmoscopy

During this important ophthalmological examination, the various inner and outer parts of the eye are examined using an ophthalmoscope with a lighted magnifying glass. If corneal injuries are suspected, fluorescent eye drops can be used, which collect at the site of the injury and can be easily identified with blue light.

In order to be able to see the back of the eye (fundus) with the retina, the optic nerve and the blood vessels particularly well, the eye is “dropped wide”, i.e. the pupil is widened with a certain medication so much that the doctor gets a particularly large “peephole”. .

Further examinations of the eyes

If the previous tests can also be carried out by an experienced general practitioner, for example, the more special examination techniques – which are necessary for certain questions – are reserved for the eye specialist. Below is a small selection:

• Slit lamp:  With this special microscope, light can be brought into the eye from the side and thus the cornea, iris and lens can be assessed particularly well. If additional lenses and glasses are put on, the vitreous body and retina are also clearly visible.
• Tonometry:  If there is a suspicion of an increase in pressure in the eye, the exact intraocular pressure can be determined with this special device (tonometer), which is usually placed on the cornea under local anesthesia.
• Perimetry:  With the help of this special device, the visual field can be determined more precisely than with the test described above. To do this, the patient stares into the perimeter with one eye and indicates when he sees small lights flashing in different places. These values ​​are converted graphically.
• Fluorescence angiography of the fundus:  With this method, even the smallest vascular changes can be visualized. For this purpose, a dye is injected into the arm vein as a contrast medium and made visible in the choroid and retinal vessels using blue light.
• Electrophysiological investigations:  The function of the optic nerve, visual pathway and retina can be checked using small electrodes that measure electrical activity.
• Imaging procedures:  Ultrasound examinations can be used to  diagnose retinal detachments  and vitreous detachments in particular, and to measure the longitudinal axis of the eye. The bony border of the eyeball (e.g. after an accident) can be shown particularly well using  computed tomography  (CT), the soft tissue (e.g. in the case of a suspected tumor) primarily using  magnetic resonance imaging  (MRI).

What the eye does every day

An estimated 40 percent of the information we take in is conveyed via colors and thus via our eyes. On their retina, 120 million rods for black and white vision and six million cones, which are sensitive to red, green and blue, enable humans to distinguish several hundred thousand color shades. The eye is therefore a complex system – this also explains the large number of different eye examinations.