Visual impairments
Michael Horvat, Ronald V. Croce, Caterina Pesce, Ashley Fallaize in Developmental and Adapted Physical Education, 2019
According to Holbrook (2006), one-tenth of 1% of all school-aged children are visually impaired, and approximately 85% of these children have some usable vision. The primary causes of visual impairment can be tracked to defects in development with the ocular mechanism, birth defects, disease, and injuries. Other causes cannot be traced and are classified as idiopathic. To understand the basic mechanism of vision, think of the eye as a camera that relays messages to the brain. Light enters the eye through the “camera’s” outer layer (cornea) and passes through the pupil. The eye is protected by the eyelids and bony socket of the skull, which is filled with fat to absorb shock and allow eye movement. Four rectus muscles allow motion of the eye upward, downward, inward, and outward, while the two oblique muscles add upward and downward movement.
The ophthalmic patient
Mary E. Shaw, Agnes Lee in Ophthalmic Nursing, 2018
The actual visual impairment experienced by the patient will vary with the eye condition. With many conditions there is no, or only slight, visual impairment and this may be temporary. Other conditions cause gross visual loss that may have occurred suddenly or gradually over the years. This visual loss may be untreatable and permanent, may be progressive, or sight may be restored. Some patients will have only one eye affected and others both eyes, probably to different degrees. Some will have blurred vision; some will only be able to make out movements. Others will be able to differentiate only between light and dark, or will see nothing at all. Some will have lost their central vision, others their peripheral vision. A number of patients will see better in bright light than dim light, and vice versa. Some degree of visual loss can be very upsetting to the patient and can prove to be a severe impairment to daily living. All patients experiencing severe visual loss will require practical and emotional help in coming to terms with their loss, regardless of the cause and the course it has taken.
History and physical examination
Alistair Burns, Michael A Horan, John E Clague, Gillian McLean in Geriatric Medicine for Old-Age Psychiatrists, 2005
Next, look at the eyes. Do they appear symmetrical? Do the eyelids droop? Is the conjunctiva inflamed or unusually pal�? Is there an ectropion or an entropion? Is the sclera white, red or yellow? Check near visi�n by getting the patient to read something. Check distance visi�n by having the patient describe something > 10m away. Check visual fields (hemianopia): this can be done conveniently by holding up a piece of string horizontally and asking the patient to touch the middle. Patients with a hemianopia indi- cate the midpoint of the intact field of view which will appear eccentrically placed to the examiner. If there is visual impairment, the lens and retina should be examined. An ophthalmoscope is a diff�cult instrument to use: ophthalmologists hardly ever use it other than as a light source. The easiest disorder to detect is cataract (impaired red reflex). Examining the retina is much more difficult, especially in older people with small pupils; if you do not know how to interpret what you find, there is little point to dilating the pupils. If there is evidence of a hearing impairment, this is a good time to examine the ear with an otoscope (mainly to look for ear wax, foreign bod- ies or perforations of the ear drum). Next, examine the neck. You should at least check for carotid bruits and enlarged lymph nodes. Remember, absence of carotid bruits does not rule out significant carotid artery athero- ma. Assessing the jugular venous pressure is not easy, and to enable you to do it properly, the patient must be undressed and in the correct position.
Common systemic medications that every optometrist should know
Published in Clinical and Experimental Optometry, 2022
A number of case studies have reported ocular complications associated with PPI use. Six reports detailed findings of irreversible anterior ischaemic optic neuropathy with PPI use.77 However, a large retrospective cohort study of 94,063 subjects showed a minimal association between inflammatory and vascular disorders of the eye and omeprazole or histamine H2-receptor antagonists.78 However, when the data was analysed dividing the patients into separate medication groups, researchers discovered an increased risk of visual impairment in the treatment group using PPIs. Visual impairment included incidence of visual disturbance, blurred vision, unilateral or bilateral blindness, transient blindness, night blindness, visual field defect, or sudden vision loss. This large-scale data analysis provides reinforcement to the case studies reporting ocular side effects of PPI use and this medication side effect should be considered as part of the work up of patients with newly reported visual impairment.79 Discontinuation of the medication may be necessary in order to determine whether the ocular symptoms are linked to GERD medication use.
Developing a stroke-vision care pathway: a consensus study
Published in Disability and Rehabilitation, 2022
Fiona J. Rowe, Lauren R. Hepworth, Claire Howard, Kerry L. Hanna, Brinton Helliwell
Visual impairment may be the sole presenting sign of stroke – approximately 90% of occipital lobe stroke lesions have no other neurological signs [6]. More commonly, however, visual impairment is one of a number of presenting signs and symptoms of stroke [7]. Visual impairment can be complex encompassing many types of visual conditions with a wide range of impacts. Visual impairment may give rise to symptoms that are noted immediately on the occurrence of the stroke or, indeed, visual symptoms may only become apparent some weeks or months after stroke onset. Thus, presentation of visual symptoms by stroke survivors can be expected at any stage from stroke onset through to chronic post-stroke stages. Furthermore, transient visual impairment is also recognised as a precursor symptom of stroke with such symptoms being hallmarks of transient ischaemic attack (TIA) [8]. Recognition of visual impairment as a common sequela of stroke is slowly increasing [1,9]. However, it remains under-reported and poorly identified in stroke survivors because many visual conditions cannot be detected by merely observing the eyes [10]. Careful questioning alongside specific testing of visual function is required for the accurate and reliable detection of visual impairment [9,11].
Rationale, Design, Methodology and Baseline Data of Fushun Diabetic Retinopathy Cohort Study (FS-DIRECT)
Published in Ophthalmic Epidemiology, 2020
Yu Wang, Zhong Lin, Liang Wen, Shi Song Rong, Xiao Xia Ding, Dong Li, Ke Mi Feng, Feng Hua Wang, Yuan Bo Liang, Gang Zhai
Because there is no universally accepted definition of visual impairment, and we wanted to compare our visual impairment prevalence data to those of other population-based studies, two definitions of visual impairment were used in this study. Visual impairment definition 1 (World Health Organization definition): low visual definition was 20/400≤ BCVA <20/60; blindness definition was BCVA <20/400 in the better-seeing eye. Visual impairment definition 2 (US standard and in most population-based studies of eye disease): visual impairment was categorized as mild (20/40≤ BCVA ≤20/63), moderate (20/80≤ BCVA ≤20/160), or severe (BCVA ≤20/200). The severe visual impairment definition was also the blindness definition in the US standard. The second definition was calculated for both the better-seeing eye and the worse-seeing eye. Causes of visual impairment and blindness were determined by two ophthalmologists based on the clinical examination and reported history. For cases where two ophthalmologists disagreed, a third senior ophthalmologist adjudicated the decision.
Related Knowledge Centers
- Astigmatism
- Cataract
- Glaucoma
- Macular Degeneration
- Presbyopia
- Refractive Error
- Visual Perception
- Amaurosis Fugax
- Near-Sightedness
- Far-Sightedness