The eyes are a complex system that allows us to see shapes, colors and much more. But in about half of the population, vision is impaired. If so, various methods of examination can help determine the causes. What are the options for eye examination and when to use which method?
Visual disturbances, itching and redness: when to the ophthalmologist?
A number of complaints can lead to a visit to the ophthalmologist. Often these are acute symptoms such as tearing and redness, photophobia, itching or pain, but dryness and sudden or gradual visual disturbances are also common. In children, strabismus is one of the main causes for visiting the ophthalmologist. Diseases of the eye include inflammations and infections, changes in the vessels or retina, tumors, injuries and involvement of the eyes in other diseases such as high blood pressure. In many cases, the causes can already be narrowed down through targeted questioning. It is important to know whether one or both eyes are affected, when and how often the complaints occur, whether they started suddenly and whether other symptoms are present. Other diseases such as allergies or diabetes as well as medications taken can also be of importance, as can diseases in the family. Recognize eye diseases: These pictures help!
Eye examination: the basic diagnostics.
The physical examination is usually performed on a seated patient:
- Externally visible signs of disease (inspection) include redness, increased lacrimation, and corneal lesions.
- Foreign bodies or changes under the eyelid can be assessed by the doctor by folding the eyelid with the help of a spatula or cotton swab.
- If there is a suspicion of infection, he can take a swab (from the conjunctiva, cornea or vitreous) with a cotton swab and have it examined in the laboratory for pathogens.
- In rare cases, a blood test may also be necessary.
- During the palpation examination (palpation), the doctor presses lightly with his fingertips on the closed eyeballs and can thus roughly check the intraocular pressure in a side-by-side comparison (which may be elevated, for example, in glaucoma or due to a hematoma).
Function tests of the eyes
Depending on the complaint, vision, reaction, shape and symmetry of the pupils, as well as the mobility of the eyes (and their muscles) can be examined. Below, we introduce the different types of eye examinations in more detail.
Vision examination
These include examination of visual acuity (visual acuity testing), visual field, which is the area that can be surveyed when looking in one direction, and color or dark vision.
- Visual acuity testing: they are almost a landmark of ophthalmologists – the boards with letters, numbers, hooks or pictures in different sizes. With them, short-sightedness or long-sightedness, as well as their extent, can be determined.
- Visual field test: this involves the doctor and patient sitting opposite each other at the same height. Then the patient must look with both or one of the eyes (and cover the other) in the direction of the doctor and determine the number of fingers held by the doctor at different heights and directions, or say from when the finger is seen.
- Color vision: Color blindness and color vision deficiency can be detected with the help of certain boards on which colorful spots of color form patterns that are recognized as a number only by color vision.
Assessment of the pupil
The normal pupil narrows when exposed to light, even when it is not directly illuminated, but only the one on the opposite side. If this reflex does not function properly, it indicates certain diseases of the optic nerve, brain, or paralysis eye muscle. Pupil changes such as asymmetries, widening or narrowing can also be caused by inflammation, medication or other pathological causes. The pupil is evaluated during ophthalmoscopy (see below).
Assessment of ocular motility
The position of the eyes relative to each other, their mobility, and the simultaneity of their movements are functions that are examined, especially in strabismus and double vision.To do this, the doctor first assesses whether the light reflections on the cornea are symmetrical, then does a cover and uncover test to check strabismus (covering one eye and checking how the other reacts), and then has the patient look in nine different directions (by holding a finger there).
Ophthalmoscopy.
This important ophthalmic examination uses an ophthalmoscope, which has an illuminated magnifying glass, to examine the various external and internal portions of the eye. If corneal injury is suspected, fluorescent eye drops can be introduced, which accumulate at the site of injury and are easily seen with blue light. To get a particularly good view of the back of the eye (fundus) with the retina, optic nerve and blood vessels, the eye is “dropped wide”, i.e. the pupil is dilated so much with a certain medication that the doctor gets a particularly large “peephole”.
Other examinations of the eyes
If the previous tests, for example, can also be performed by an experienced general practitioner, the more specialized examination techniques – necessary for certain questions – are reserved for the eye specialist. The following is a small selection:
- Slit lamp: this special microscope allows light to be introduced into the side of the eye for particularly good assessment of the cornea, iris and crystalline lens. If further lenses and glasses are put on, the vitreous body and retina can also be seen well.
- 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), usually placed on the cornea under local anesthesia.
- Perimetry: with the help of this special device, the visual field can be determined more accurately than with the test described above. To do this, the patient looks rigidly into the perimeter with one eye and indicates when he sees small lights flashing in different places. These values are converted graphically.
- Fluorescein angiography of the fundus: this method can be used to visualize even the smallest vascular changes. For this purpose, a dye is injected into the arm vein as a contrast agent and made visible by means of blue light in the choroidal and retinal vessels.
- Electrophysiological examinations: The function of the optic nerve, visual pathway and retina can be checked using small electrodes that measure electrical activity.
- Imaging procedures: Ultrasonography can be used to diagnose retinal detachments and vitreous detachments in particular, and to measure the longitudinal axis of the eye. The bony outline of the eyeball (for example, after an accident) can be particularly well represented by computed tomography (CT), the soft tissues (for example, in the case of suspected tumors) mainly with magnetic resonance imaging (MRI).
What the eye does every day
It is estimated that 40 percent of our ingested information is conveyed through colors and therefore through our eyes. On their retinas, 120 million rods for black and white vision and six million cones sensitive to red, green and blue allow humans to distinguish several hundred thousand shades of color. The eye is therefore a complex system – this also explains the large number of different eye tests. Color blindness: image test for red-green deficiency and co.
