Retinal Examination

Retinal examination refers to the examination of the retina, optic disc, and retinal blood vessels. A basic assessment of the central fundus is part of the general ophthalmological examination. During this, the ophthalmologist evaluates the deeper structures of the eye—those not directly visible to the naked eye—using various magnifying instruments.

However, to fully examine the fundus and view the details in three dimensions, the pupil must first be dilated with eye drops. For an even more detailed assessment, the examination is supplemented with OCT imaging. The purpose of all this is the early detection of changes affecting the sensitive tissues of the fundus and the establishment of an appropriate treatment plan.

What is the fundus?

The fundus refers to the inner layer of the posterior two-thirds of the eyeball. The fundus includes the retina, the blood vessels running through it, and the optic disc (papilla). The retina is only 0.3 mm thick and consists of 10 layers stacked upon one another.

The retina contains the photoreceptor cells responsible for vision; its central part is the macula, responsible for sharp vision and color perception.

From here, the photoreceptor cells transmit visual information via nerve fibers toward the brain.

The nerve fibers, together with the blood vessels, bundle together to form the optic nerve, the very first part of which is visible on the fundus and is called the optic disc.

What is the procedure for retinal examination?

Pupil Dilation

We can only examine the retina in detail if the pupil is dilated. Without pupil dilation, the examination is like trying to assess objects in a dark room by looking through a keyhole. In such cases, the lack of three-dimensional vision and illumination prevents us from evaluating fine details and peripheral areas. However, by dilating the pupil, we achieve an effect as if we had opened the door, the room became bright, and we could look around perceiving the fine details of objects in three dimensions.

Pupil dilation is achieved by administering eye drops, which temporarily dilate the narrow pupil to more than double its size and prevent it from constricting in response to light during the examination.

Pupil dilation is painless; the effect of the drops reaches its maximum 30 minutes after administration and usually wears off after 2–3 hours. While the dilating drops are in effect, vision is blurred, reading small print is not possible, and driving is contraindicated. Pupil dilation and the examination are harmless and can be repeated any number of times. However, in cases of narrow-angle glaucoma or predisposition to it, dilation is recommended only after laser iridotomy to prevent the onset of an acute glaucoma attack.

Slit-Lamp Biomicroscopy

Retinal examination with pupil dilation can be performed in several ways, but it is most commonly done at the standard ophthalmic examination instrument, the slit lamp, and takes a few minutes. Before the retinal examination, we always perform a general ophthalmological examination as well.

During the retinal examination, we shine the slit lamp into the eye and use a special 90-diopter lens to examine different areas of the magnified image of the fundus. With this method, we cannot precisely distinguish the layers of the retina, but we can generally determine whether the changes are visible in the lower, middle, or upper layers.

To examine the outermost parts of the retina, we ask the patient to look in different directions. During the examination, we do not need to touch the eyeball, so the examination is completely painless, although some may find the bright light slightly uncomfortable. After the examination, vision may be worse for a short time and light phenomena may also be perceived.

OCT Examination

Optical coherence tomography (OCT) is a modern imaging technique that provides detailed, cross-sectional images of the different layers of the retina. With this method, all 10 layers can be identified, and early pathological changes that are not visible to the naked eye can also be detected.

During the examination, the device emits light waves into the eye, and based on their reflection, it creates an extremely precise map of the tissues. The resulting image enables early detection of minute changes in the retina and optic nerve, making treatment more effective for conditions such as macular degeneration, diabetic retinopathy, or glaucoma.

During the OCT examination, you will not feel any pain or discomfort. The measurement is harmless to the eye and can be repeated any number of times. Thanks to this, we regularly use OCT to monitor eye diseases and verify the effectiveness of treatments.

Other Examination Options (Ophthalmoscopy, Fundus Camera)

Ophthalmoscopy is another option for examining the fundus, which can be performed in several ways. In these cases, we use a handheld instrument or a headlamp and magnifying lens. Due to certain limitations of these procedures, we mostly use them only at the bedside or when examining young children.

A fundus camera can also be used for screening, which is capable of capturing images of the central area of the fundus even without pupil dilation, which the physician evaluates later. However, if disease is suspected, the examination must be repeated with pupil dilation. The fundus camera can be a useful supplementary tool for opticians during eyeglass prescriptions, and it is the best method for documentation and long-term monitoring of certain diseases (e.g., fundus nevi, macular and optic disc abnormalities).

When is fundus examination indicated?

Retinal examination without pupil dilation is part of the general ophthalmological examination. In such cases, the central part of the fundus can be examined and more advanced stages of diseases can be detected, but the precise or early changes of diseases cannot be meaningfully assessed.

If symptoms suggest a disease, we must perform pupil dilation so that we can thoroughly examine all parts of the fundus. In such cases, we can already see the central parts of the fundus in three dimensions, which ensures a more detailed examination. However, even this is not sufficient for early diagnosis of fundus diseases, which is why we perform an OCT examination that enables cellular-level analysis of the tissues.

Generally, when we speak of retinal examination, we mean retinal examination with pupil dilation performed as part of a comprehensive ophthalmological examination. It is also worth knowing that the diameter of the pupil becomes progressively narrower with advancing age, and thus retinal examination without pupil dilation may become unfeasible.

For which symptoms is retinal examination recommended?

Based on certain ophthalmological symptoms, it is possible to infer which part of the eye is affected by the change, but there are also conditions where diseases of different parts of the eye cause the same symptoms. In such cases, we must systematically rule out changes in different parts of the eye, including fundus abnormalities.

Which conditions particularly warrant retinal examination?

There are certain systemic diseases that frequently lead to fundus changes, so in such cases, retinal examination with pupil dilation is regularly recommended.

Certain eye diseases similarly require pupil dilation, primarily because the change is located on the fundus itself, and this area can only be examined in rich detail in this manner.

Secondly, the other, similarly deep-lying tissues of the eye besides the fundus cannot be thoroughly examined if the pupil is narrow, such as the lens or the vitreous body.

It also occurs that retinal examination is necessary because changes in the surrounding tissues affect the retina, so we must also assess and treat it.

Is fundus examination worthwhile during routine eye screening?

During screening, we also examine the retina as a matter of course. With a normally dilated pupil, we can only partially examine the optic disc and the macular area. In older age, as the pupil becomes progressively narrower, it may happen that even these parts cannot be assessed. In such cases, we must perform pupil dilation, since ruling out the most common vision-impairing diseases is not possible with a narrow pupil, yet it may give the patient a false sense of security.

Examination of the retina is recommended even during screening after dilating the pupil with drops. Examination performed without dilation may leave initially asymptomatic but severe and rapidly progressive diseases undetected. In such cases, the goal of treatment may only be to prevent further vision deterioration. More rarely, we may also discover life-threatening fundus tumors (choroidal melanoma) during the otherwise asymptomatic screening of young adults.

In all cases of suspected vitreous and fundus disease, fundus examination with pupil dilation is required; we only exceptionally deviate from this.

What diseases can be diagnosed after retinal examination?

After fundus examination, we most commonly obtain answers regarding the following abnormalities:

• Macular diseases: macular degeneration, macular edema, macular hemorrhage
• Optic disc diseases: glaucoma, optic disc edema, optic neuritis, optic disc drusen
• Fundus vascular changes: atherosclerosis, vascular occlusion, neovascularization
• Changes in the peripheral retina: retinal tear, retinal detachment, peripheral retinal degeneration
• Hereditary, degenerative, developmental, and congenital abnormalities of the macula and optic disc
• Benign and malignant tumors of the retina, choroid, and optic disc
• Drug-induced retinal and optic nerve damage
• Injuries and other damage affecting the deeper parts of the eye

Abnormalities discovered during examination of the retina and optic nerve sometimes exceed the competence of the general ophthalmologist; in such cases, the patient must be referred to a specialist.