Ensuring patients get the best possible visual outcomes is a main focus of day-to-day practices for eye care professionals of all stripes.
Indeed, the best possible outcome is often generalized as “20/20 vision.” However, this is somewhat misleading. In fact, 20/20 vision is a term used to express normal visual acuity (VA), or the clarity and sharpness of vision, measured at a distance of 20 feet. It’s one of several factors that influence vision; other attributes like peripheral vision, eye coordination, depth perception, focusing ability and color vision, contribute to overall visual ability too.1
There are, of course, many conditions that can lower VA, including myopia, presbyopia and hyperopia. It can also result from another condition or disease. The segment of the optometry industry focused on improving VA is worth billions of dollars; however, despite its lion share of the market, research into the best visual acuity management practices exists to a lesser degree compared with other ophthalmological issues.
The challenge of achieving best corrected visual acuity (BCVA) in patients is one optometrists and ophthalmologists face on a day to day basis, and refers to the measurement of the best vision correction that can be achieved with lenses. If an individual’s vision is 20/40 without glasses, but 20/20 with them, their BCVA is said to be 20/20.
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The basic guidelines for achieving BCVA are similar worldwide.
First, before examining a patient for any ocular complaint — and especially in an emergency setting — testing and recording VA before treatment is imperative. Visual acuity recorded in this setting can prevent future ambiguity regarding the time and cause of visual loss. In most instances, either a standard printed Snellen eye chart is used with the patient 20 feet (6m) away or a reading card with a reduced eye chart is used at 14 inches (35cm).2 Based on the results of the examination, the patient is offered lenses or corrective treatment to achieve BCVA.
Central VA can be thought of as the vital sign of ocular function. When it’s found to be 20/20, a great deal of information is obtained: the eye is properly refracted, the ocular media are clear, the foveal region of the retina is functioning, and the optic nerve and visual cortex are generally intact. Taken together with confrontation visual field testing and pupillary function, the measured level of VA can be used to corroborate or question a patient’s complaint of decreased vision.2
Naturally, the importance of VA, and the challenge of achieving BCVA, is not lost on the Asia Optometric Congress (AOC), one of the largest and most visible groups dedicated to optometry in the world. The AOC held an online conference last November (eAOC 2020) and covered a wide array of topics related to optometry. Naturally, the impact of the COVID-19 pandemic was featured heavily, but other issues, including the proper management of visual acuity, were covered too.
As part of the online conference, Dr. Soe Min Aung, a senior eye consultant at the North Okkalapa General and Teaching Hospital, Yangon, Myanmar, presented The Challenges of Achieving Best Corrected Visual Activity. His presentation was a concise and highly informative examination of the best practices one can employ to achieve best corrected visual acuity (BCVA). Dr. Aung drew primarily on his own experience of treating patients within an underdeveloped healthcare infrastructure in Myanmar.
Optometrists: Know Your Enemy
Dr. Aung’s presentation on the nature of astigmatism, where the eye is not roundly shaped, should prove particularly beneficial to new clinicians. There are two forms of the condition he said, corneal and lenticular, caused by mishapement in the cornea and lens respectively. This should be particularly important to pediatric clinicians as untreated myopia and astigmatism may go on to develop into keratoconus, a progressive disorder in which the cornea assumes a protruding cone shape.
The doctor said clinicians should be vigilant for risk factors including a family history of keratoconus and lenticonus, corneal scarring, excessive myopia, and a history of eye surgery. Symptoms include blurred vision, eye strain and headaches; he recommended using devices like the phoropter, keratomer, topographer and autorefractor during diagnosis. Like many conditions, both ocular and otherwise, Dr. Aung emphasized that early diagnosis is the key to good patient management and outcomes.
Understanding the Importance of Risk Factors in Diagnosis
Dr. Aung also spoke about the importance of lifestyle factors in causing ocular conditions, and that they should be factors taken into consideration by clinicians. Age-related macular degeneration (AMD), for example, has risk factors including smoking and poor diet, as does diabetic retinopathy, which he said often causes no symptoms in the early stages of the disease. Linked to both these conditions he said, is macular edema, with risk factors including diabetes, AMD and eye surgery, too.
Though Dr. Aung says conditions like astigmatism and keratoconus are some of the most common threats to visual acuity, he also spoke about the dangers of central vision loss. Conditions such as diabetic retinopathy, AMD and macular edema can have a significant impact on VA, as much as (or even more than) myopia and presbyopia. He emphasized that doctors must exercise constant vigilance for their patients and recommends frequent vision check-ups.
According to Dr. Aung, there are several key things optometrists can do to ensure that BCVA is achieved on a regular basis. First, patients with astigmatism should be required to wear glasses or contact lenses. Second, low vision aids should be provided for patients suffering from AMD. Finally, serious eye problems should be immediately referred to an ophthalmologist as early as possible to maintain or improve vision.
Ultimately, a main takeaway of Dr. Aung’s presentation is to always act and always check — if a vision issue appears, check it as soon as possible; in some cases, damage and vision loss can be prevented if treated quickly enough. His experience of working on the frontlines will no doubt be of particular benefit to optometrists and we hope to view more presentations on this subject in 2021.
Editor’s Note: The Asia Optometric Conference (eAOC 2020) was held from November 18 to 19, 2020. Reporting for this story took place during the meeting.
- The American Optometric Association. Visual Acuity. Available at https://www.aoa.org/healthy-eyes/vision-and-vision-correction/visual-acuity?sso=y Accessed on January 31, 2021.
- Walker KH, Hall WD, Hurst JW. Clinical Methods: The History, Physical, and Laboratory Examinations. 3rd edition. Boston: Butterworths; 1990.