Examenul campului vizual

Visual field examination - when is it important to do it and what does it show?

Examenul câmpului vizual, cunoscut și sub denumirea de camp vizual test, este un instrument crucial în diagnosticarea afecțiunilor oculare. Acest examen se concentrează pe evaluarea periferiei vizuale a pacienților și identificarea eventualelor pierderi sau deteriorări ale câmpului vizual. Prin intermediul acestui proces precis și non-invaziv, medicii oftalmologi pot detecta semne timpurii ale unor condiții medicale grave, cum ar fi glaucomul sau tulburările neurologice. Articolul de față explorează importanța examenului câmpului vizual și relevanța sa în menținerea unei sănătăți oculare optime.

Introducere

The visual field is the totality of points in space that can be perceived by your eye when you look straight ahead.

For example, if you stare HERE, how much of the rest of the room you are in can you perceive?

Normally, the limits of the human visual field are 50° superior, 60° nasal, 70° inferior and 90° temporal. Many diseases can affect the visual field, causing scotozoites (blind spots), narrowing or complete amputation of half or a quarter of the vision.

1. What conditions require visual field testing?

The main conditions requiring visual field testing are:

Glaucoma- if in the early stages we observe a widening of the blind spot (physiological scotoma) and a slight narrowing of the visual field, in advanced stages glaucoma can induce a tubular vision, with a visual field limited to 5-10°.
Stroke- depending on the location and extent of the stroke, visual field changes can range from scotozotopes (blind spots) to the complete absence of one half of the visual field

Multiple sclerosis- changes in the visual field caused by multiple sclerosis are variable depending on the location of the demyelinating foci, but a common sign is the arcuate scotoma

Brain tumours- changes in the visual field can be systematized into hemianopsia (amputation of half of the visual field) or quadranopsis (amputation of a quarter of the visual field), bilateral or contralateral, and can guide us with great precision to the location of the tumour

Intracranial hypertension (Pseudotumor cerebri)- generally causes changes in the nasal visual field of both eyes, i.e. a binaural hemianopsia

Pituitary tumours- classically causes bitemporal hemianopsia, i.e. amputation of the visual field of both eyes in the temporal (outer) region

Thyroid ophthalmopathy (Graves' disease)- Compressive optic neuropathy in Graves' disease can cause central, cecocentral and paracentral scototomes in the visual field

Pigmentary retinopathy- causes concentric narrowing of the visual field in the periphery with the appearance of tubular vision in advanced stages

Autoimmune diseases treated with hydroxychloroquine (Plaquenil)- macular damage after prolonged treatment with high doses of hydroxychloroquine causes central and paracentral scotozotopes in the visual field

The Visual Analyser works as an optical system similar to a landline telephone with cable and switchboard. The eye, as an organ, picks up visual information from the outside just as the telephone picks up sounds, transmits them via optical pathways, the 'cable', to the brain, the equivalent of the 'switchboard', which analyses and 'understands' them.

For your ophthalmologist, visual field testing is important in the analysis of retinal function, optic pathways and cortical centres, so the 'cable' and the 'central'. This is why the visual field examination is an essential investigation in both ophthalmology and neurology when vision impairment is caused by a brain disorder.

2. When should I go to the doctor?

Warning signs that should immediately refer you to an ophthalmologist or neurologist are :

A double view recently established (diplopia)
Eyelid drooping (palpebral ptosis), unilateral or bilateral, occurring suddenly
A stain that obstructs your vision (scotom)
Straight lines that look distorted to you or distorted images (metamorphopsii)
Involuntary, uncontrolled eye movements (nystagmus)
Lack of eye alignment, with deviation of one eye from the other, recently developed (strabismus)
Facial asymmetry sudden onset (facial hemiparesis)
Loss of word comprehension written or spoken and inability to pronounce words or link coherent sentences (aphasia)
Intense headachesthat do not respond to the usual painkillers or anti-inflammatories

3. What is the procedure for visual field testing?

Pentru testarea câmpului vizual folosim un aparat numit computerized perimeter. It uses a bright fixation point that remains constantly displayed in the centre, corresponding to the fixation, and a bright, moving point displayed in different areas of the field of view. Perimetry can be kinetic or static, where the bright spots appear at different intensities at fixed locations until they are detected by the patient.

To perform this examination, the patient is placed on a machine with a semi-spherical dome. He has to look forward, inside the dome, at the fixation point. Each eye is tested separately, wearing the appropriate optical correction, and the other eye is covered with an occluder. Small lights will appear in different places inside the dome as bright dots. The patient must press a button on a joystick whenever they can see these dots. The device tracks and analyses the responses given and provides a topographical map of the visual field which your ophthalmologist then interprets in a clinical context. The whole test can take between 5 and 10 minutes.

4. How can the field of vision be affected?

The visual field may be affected totally or zonally. The ophthalmologist will look especially for the presence of black or grey spots (scototocas), which signify a significant decrease or even absence of light perception in that area. These scotoas may be various shades of grey to black, depending on the severity of the loss of perception, which the perimetry machine analyses according to the statistical normal values for the patient's age category. Visual field defects may have different shapes and distributions, may be single or multiple, may be the result of actual defects, or may arise from visual field errors.

Attention! The visual field examination relies on the patient's careful collaboration and gives us a subjective final answer. Therefore, at least 3 visual fields performed are necessary for the patient to reach the maximum level and accuracy in performing this analysis, and for the information about the vision to be true.

At the Prof. Dr. Munteanu Ophthalmology Centre, we use the two worldwide reference perimeters for glaucoma follow-up, Zeiss Humphrey Flied Analyzer 3 and neurological defects, Optopol Projection Perimeter PTS.

Descoperiți mai multe informații valoroase despre oftalmologie și sănătatea ochilor vizionând materialele realizate de experți în domeniu de pe canalul nostru de YouTube.

Articles - 10th February 2023

Visual field examination