Optometry

What is optometry?

Optometry is the examination of the eye and its related structures to detect visual impairments and prescribe appropriate lenses or other visual aids or eye exercises to compensate for vision deficiencies. Given the wide scope of the field of optometry, the Persian equivalent of optometry, which is actually a word-for-word translation of optometry, does not seem to be the correct equivalent. As one of the primary health care providers, an optometrist examines and identifies vision problems of individuals with the help of available tools and devices. After diagnosing the type and extent of the clients’ vision problems, they help their visual system to function more efficiently by prescribing vision aids such as glasses, contact lenses, performing a series of eye exercises and exercises, and giving the necessary health advice and instructions (non-drug and non-surgical treatments). In addition, during detailed eye examinations, if there is any disorder or disease that requires medical treatment, the optometrist refers patients to other doctors such as ophthalmologists, neurologists, internal medicine specialists, etc. The optometrist is also able to manufacture and provide the prescription glasses he prescribes, in accordance with scientific principles.After diagnosing the type and extent of the patients’ vision problems, he helps their visual system to function more efficiently by prescribing visual aids such as glasses, contact lenses, performing a series of eye exercises and exercises, and giving the necessary health advice and instructions (non-drug and non-surgical treatments). In addition, during detailed eye examinations, if there is any disorder or disease that requires medical treatment, the optometrist refers patients to other doctors such as ophthalmologists, neurologists, internal medicine specialists, etc. The optometrist is also able to manufacture and provide the prescription glasses he prescribes, in accordance with scientific principles. Therefore, an eye patient should initially be examined by an optometrist. If he/she has refractive errors, binocular vision disorders, eye refractive muscle deviations, and the like, he/she will be treated by the optometrist, and otherwise he/she will be referred to other surgeons.

What symptoms should you see an optometrist for?

  • Avoidance or lack of interest or drowsiness when doing tasks that require close vision (reading, drawing, etc.) or distance vision (driving, watching TV, etc.)
  • Unusual burning and tearing when working on the computer, reading, or watching TV
  • Watching TV from a close distance, or holding a book close when reading
  • Seeing objects twice, losing lines, and not correctly recognizing distances
  • Excessive rubbing of the eyes while performing eye tasks
  • Occasional or persistent blurred vision at near or far distances
  • Tilting your head or squinting your eyes to see better
  • Complaints of headaches and eye strain
  • Eye pain and bloodshot eyes
  • Eye fatigue and blinking
  • Extreme sensitivity to light
  • Deviation of the eyes

Types of vision tests in occupational examinations  

Vision tests commonly used in occupational examinations include visual acuity, depth perception, and color vision, which are explained below.

Visual acuity (visual acuity)
Visual acuity is most often measured by Snellen charts (usually the letter E screen), which are designed to measure distance and near vision, and the result is given as a fraction. For example, 40/20 vision means that the smallest image the person tested can distinguish is twice the standard size. In other words, the line in question can be distinguished by a person with normal vision at a distance of 40 feet (12 meters), while the person tested can read it at a distance of 20 feet (6 meters).Visual acuity is considered the primary indicator of a person’s visual acuity, but it should be noted that visual acuity only assesses central vision and does not indicate other conditions that involve the peripheral parts of the retina. Therefore, visual acuity is only one indicator and should not be used to assess the overall health of the eye and vision.

Depth vision
The human eye can use monocular and binocular cues to determine the distance between objects. Given the different images of each object in the eye, when these images are combined in the brain, depth perception is achieved.

Color vision
The natural eye with natural color vision can distinguish millions of different colors, but for absolute judgment only about 30 colors can be reliably determined. Color recognition depends on the following factors:

  • Retina Matching Mode
  • Network intensity trigger area
  • Simultaneous contrast (color recognition under the influence of background color)
  • Sequential contrast (color recognition under the influence of the color of the previously seen object)

Color vision impairment usually occurs in two forms: congenital and acquired. The congenital type is more prevalent than the acquired type (8% of men and 0.5% of women) and is bilateral, but the acquired type is seen as a result of exposure to substances such as organic solvents and mercury or diseases of the choroid, retina, or optic nerve, and may be unilateral.

Field of vision
The normal eye, when stationary, is able to see a visual stimulus in an area that is 60 degrees above, 70 degrees below, 95 degrees temporally (externally), and 60 degrees nasally (internally). The total horizontal field of view extends to 190 degrees.The most common causes of visual field limitation include cataracts, glaucoma, retinal disorders, and age. The prevalence of visual field reduction is about 3-3.5% in people aged 16-60 years, while it increases to 13% in people over the age of 65. Most patients with peripheral and visual field impairment maintain adequate central vision.

The place of optometry testing in occupational medicine

  • Examining the status of the visual system is of particular importance in maintaining and promoting occupational health.
  • In all occupations, impairment in any of the capabilities of the visual system can lead to fatal accidents or financial losses or affect the quality of the employee’s work. Therefore, measuring visual acuity, assessing visual fields, color vision, and depth perception are very important.
  • Improving vision improves efficiency and productivity, reduces accidents, and consequently reduces costs and absenteeism.
  • Recording the details of a worker’s vision at the beginning of employment is a basis for evaluating problems after accidents or occupational illnesses, which is widely used in the issue of paying blood money and compensation.
  • Pre-employment and periodic assessment of individuals for visual adequacy allows individuals with incurable visual impairments to be placed in jobs that are commensurate with their abilities.
  • Visual impairments usually worsen over time, and periodic examinations, detection of these issues, and establishing a fit between the individual and the work can improve the efficiency of the individual and the system.