The Role of the Method in a Standard Examination
Visometry is never performed in isolation. Determining visual acuity is part of a strictly regulated standard examination scope during an initial ophthalmological consultation.
In addition to assessing the minimum visual angle, the basic diagnostic complex strictly includes three other procedures:
- Measurement of intraocular pressure (ophthalmotonometry).
- Examination of the anterior segment of the eyeball (biomicroscopy).
- Study of fundus structures (ophthalmoscopy).
When the standard scope is insufficient for accurate verification of the diagnosis, the physician resorts to additional high-tech methods. The patient may be prescribed optical coherence tomography (OCT) of the retina and optic nerve, computerized visual field assessment (perimetry), fluorescein angiography (FA), ultrasound of the eyeball, and color Doppler imaging of ocular vessels.
Historical Evolution of Vision Science
The development of the chart method by Snellen in 1882 was the culmination of centuries of accumulated knowledge in optics. The foundation of the clinical picture of eye diseases was laid by Ibn Sina (Avicenna) at the beginning of the 2nd millennium AD. In his principal work, "The Canon of Medicine," he systematically summarized the knowledge of the era as comprehensively as possible. The work remained the primary guide for physicians for five centuries, was translated into Latin, and after the advent of printing, went through more than thirty editions.
By 1604, Johannes Kepler had laid the foundations of experimental optics. He was the first to view the eye as a complex optical system that forms an inverted and reduced image of objects on the retina. Kepler defined the essence of nearsightedness (myopia) and farsightedness (hyperopia), and also explained the principle of action of corrective lenses.
In 1851, Hermann von Helmholtz developed the basis of physiological optics: he invented the first ophthalmoscope and ophthalmometer, and created the classical theories of accommodation and color perception. In 1864, Frans Donders structured the doctrine of refractive errors.
Albrecht von Graefe made a crucial contribution to the establishment of clinical ophthalmology starting in 1854. At the age of 26, he founded the first specialized journal, introduced perimetry into clinical practice, created the doctrine of ocular muscles, invented surgical instruments, and successfully performed surgery for an acute glaucoma attack.
Visometry in Toxic Nervous System Disorders
Vision testing is critically important for patients with toxic encephalopathies and acute chemical poisonings. The main goal of an ophthalmologist's consultation in such cases is the preservation of the visual organ (level of evidence LUE — C, QED — 5). A toxicologist and, in the event of Korsakoff's syndrome, a psychiatrist are also involved in the comprehensive assessment.
The examination can be routine if a patient with a history of toxic injury exhibits visual impairment of any degree of severity. A special category consists of patients with optic atrophy (OA). Their management is carried out on an outpatient basis or in a day hospital. Strict regulations for dispensary follow-up require examinations at least every 6 months during the first 2 years from the time of diagnosis.
An emergency initial ophthalmological consultation is indicated for life-threatening conditions: if the toxic injury is accompanied by rapidly progressive visual acuity loss or sudden blindness.
The Role of Visometry in Targeted Pharmacotherapy
Regular assessment of visual acuity serves as a mandatory safety monitoring tool during treatment with specific drugs. A striking example is therapy with the combination of ivacaftor and lumacaftor.
Administration of these drugs is associated with the risk of cataract development. Therefore, a mandatory baseline examination of the visual organ (including visometry, ophthalmoscopy, and biomicroscopy) is performed before starting therapy. Subsequently, monitoring is carried out every 3 months during the first year of treatment, and then once a year.
Detection of cataracts at any stage is an absolute criterion for discontinuing therapy (a STOP signal). Other reasons for discontinuation include severe hepatic impairment: an increase in liver transaminases (ALT/AST) to more than 5 times the upper limit of normal (ULN), or more than 3 times with a rise in total bilirubin above 2 ULN.
If therapy shows no effect after 6 months (no reduction in exacerbation rate, no improvement in body mass index, spirometry, and sweat test parameters, persistent need for antibiotic therapy), patients undergo a forskolin test and additional genetic testing — CFTR gene sequencing to search for complex resistance alleles (e.g., the L467F variant).
To memorize the basic ophthalmological examination, use the acronym "VOOBrazhenie": Visometry, Ophthalmotonometry, Ophthalmoscopy, Biomicroscopy.
Class and exam questions
Who developed the chart method of visometry, and when?
The method was proposed by Snellen in 1882. It is based on the physiological principle of assessing the minimum visual angle.
Is visometry performed in isolation during an initial consultation?
No, it is part of the mandatory standard along with tonometry, biomicroscopy of the anterior segment, and fundus ophthalmoscopy.
In what cases of toxic nervous system injury is emergency visometry necessary?
An emergency ophthalmological examination is performed in cases of sudden blindness or rapidly progressive decline in visual functions.
How often is vision checked during therapy with ivacaftor and lumacaftor?
Before starting treatment, then every 3 months during the first year, and thereafter once a year for the timely detection of cataracts.
What else to study on this topic
- Additional instrumental research methods in ophthalmology (OCT, FA, computer perimetry).
- Albrecht von Graefe's contribution to the development of clinical surgery and glaucoma treatment.
- Tactics for dispensary management of patients with toxic optic atrophy.
- Efficacy criteria and STOP signals during therapy with targeted drugs (ivacaftor + lumacaftor).
- Basics of physiological optics and the doctrine of ocular refractive errors.
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