Low vision is a subspecialty within the professions of optometry Optometry is a health care profession concerned with eyes and related structures, as well as vision, visual systems, and vision information processing in humans and ophthalmology Ophthalmology is the branch of medicine which deals with the diseases and surgery of the visual pathways, including the eye, brain, and areas surrounding the eye, such as the lacrimal system and eyelids. By convention the term ophthalmologist is more restricted and implies a medically trained surgical specialist. Since ophthalmologists perform and opticianry dealing with individuals who have less than normal vision even with the most accurate conventional prescription available. It can be a result of either congenital or acquired factors. An example of the former is Leber's congenital amaurosis Amaurosis refers to a loss of vision not associated with a lesion, and congenital refers to a condition present from birth . However, beyond these general descriptions, the presentation of LCA can vary, because it is associated with multiple genes and of the latter age-related macular degeneration Macular degeneration is a medical condition usually of older adults which results in a loss of vision in the center of the visual field because of damage to the retina. It occurs in “dry” and “wet” forms. It is a major cause of blindness in the elderly (>50 years)[citation needed]. Macular degeneration can make it difficult or.

Contents

Classifying low vision

Anyone with noncorrectable reduced vision is considered to be visually impaired, and can have a wide range of causes. The World Health Organization uses the following classifications of visual impairment. When the vision in the better eye with best possible glasses correction is:

Legal blindness

There are also levels of visual impairment based on visual field loss (loss of peripheral vision).

Go to visual acuity VA is a quantitative measure of the ability to identify black symbols on a white background at a standardized distance as the size of the symbols is varied. It is the most common clinical measurement of visual function. In the term "20/20 vision" the numerator refers to the distance in feet from which a person can reliably distinguish a to consult an international visual acuity expression chart.

In the United States, any person with vision that cannot be corrected to better than 20/200 in the best eye, or who has 20 degrees (diameter) or less of visual field remaining, is considered to be "legally blind" or eligible for disability classification and possible inclusion in certain government sponsored programs.

Magnitude of visual impairment

Pathologies which may cause vision acuity loss

Since the estimates of the 1990s, new data based on the 2002 global population show a reduction in the number of people who are blind or visually impaired, and those who are blind from the effects of infectious diseases, but an increase in the number of people who are blind from conditions related to longer life spans. This new information underscores the need to modify the health care agenda to include the management of the diseases that are now becoming prevalent.[1]

Distribution of visual impairment

By age: Visual impairment is unequally distributed across age groups. More than 82% of all people who are blind are 50 years of age and older, although they represent only 19% of the world's population. Due to the expected number of years lived in blindness (blind years), childhood blindness remains a significant problem, with an estimated 1.4 million blind children below age 15.

By gender: Available studies consistently indicate that in every region of the world, and at all ages, females have a significantly higher risk of being visually impaired than males. Geographically: Visual impairment is not distributed uniformly throughout the world. More than 90% of the world's visually impaired live in developing countries.[1]

Low vision, its lifestyle implications and rehabilitation

Visual impairments may take many forms and be of varying degrees. Visual acuity alone is not always a good predictor of the degree of problems a person may have. Someone with relatively good acuity (e.g., 20/40) can have difficulty with daily functioning, while someone with worse acuity (e.g., 20/200) may function reasonably well if their visual demands are not great.

Some people who fall into this category can use their considerable residual vision - their remaining sight - to complete daily tasks without relying on alternative methods. The role of a low vision specialist (optometrist or ophthalmologist) is to maximize the functional level of a patient's vision by optical or non-optical means. Primarily, this is by use of magnification in the form of telescopic systems for distance vision and optical or electronic magnification for near tasks.

People with significantly reduced acuity may benefit from training conducted by individuals trained in the provision of technical aids. Rehabilitation professionals, some of whom are connected to an agency for the blind, can provide advice on lighting and contrast to maximize remaining vision. These professionals also have access to non-visual aids, and can instruct patients in their uses.

Once the emotional shock of the disability is overcome, if alternative techniques (basic rehabilitation) are learnt, good quality of life and an adjustment to the disability can be achieved, not only in the case of low vision, but also in the case of blindness.

According to an article published by The Academy of Psychosomatics Medicine, in a sample of patients affected by progressive diabetic retinopathy, only those who had reached total blindness actually displayed a decrease in psychic symptomatology, through learning rehabilitation techniques. More marked distress remained in the subjects with persisting partial sight. Unfulfilled expectations probably increased frustration at daily defeats, coupled with fear of complete loss of residual sight. Acceptance of one's pathology and final outcome is the basis for approaching and acquiring new behavioral patterns and creating good mental, physical, and social equilibrium in those who become blind.

The subjects making the most use of rehabilitation instruments, who lived alone, and preserved their own mobility and occupation were the least depressed, with the lowest risk of suicide and the highest level of social integration.

Those with worsening sight and the prognosis of eventual blindness are at comparatively high risk of suicide and thus may be in need of supportive services. These observations advocate the establishment and extension of therapeutic and preventative programs to include patients with impending and current severe visual impairment who do not qualify for services for the blind. Ophthalmologists should be made aware of these potential consequences and incorporate a place for mental health professionals in their treatment of these types of patients, with a view to preventing the onset of depressive symptomatology, avoiding self-destructive behavior, and improving the quality of life of these patients. Such intervention should occur in the early stages of diagnosis, particularly as many studies have demonstrated how rapid acceptance of the serious visual handicap has led to a better, more productive compliance with rehabilitation programs. Moreover, psychological distress has been reported (and is exemplified by our psychological autopsy study) to be at its highest when sight loss is not complete, but the prognosis is unfavorable.10 Therefore, early intervention is imperative for enabling successful psychological adjustment.[2]

Experience tells that seeking the support of other people affected is a good therapy to overcome the disability, not only for the individual affected but for their families as well. There are associations that give this kind of support and can put the person in touch with professionals specialized in the collective's problems.

The low vision examination

It is critical that all patients be examined by an optometrist or ophthalmologist specializing in low vision care prior to other rehabilitation training to rule out potential medical or surgical correction for the problem and to establish a careful baseline refraction and prescription of both normal and low vision glasses and optical aids. Only a doctor is qualified to evaluate visual functioning of a compromised visual system effectively. American Optometric Association web site

Types of help available

Medical help aside, the main ones are, in first place, information; secondly, what help the administration offers; and finally the ones which facilitate personal rehabilitation, education, and work and social integration.

Information is fundamental: doctors and sanitary personnel must have this information to offer the patient when the moment is right. The desolation that doctors experience when they must tell a patient they can't do anything more is only surpassed by the loneliness and isolation the patient, who does not know where to go or what to do for help. Administrative aids are valuable allies, though sometimes they may lie hidden under a legal mess. Adaptation to the disability and psychological help are priority-one issues and must be confronted from the start. Not least =important and almost as urgent is the education of the patient and their family to confront the new situation. The adaptation of the work place (the one the person currently has or a different one) is regulated by laws and norms and there are interesting subventions for companies that make the necessary modifications to allow a person with disabilities into their work force; therefore the reluctance to hire visually handicapped people is an anti-economic prejudice, for the company and society. Lastly, social integration aids facilitate adapted leisure and cultural activities, and private and public initiatives tending to improve mobility and better access to information for everybody, including the visually impaired.

Optical aids

The vast majority of patients with low vision can be helped to function at a higher level with the use of low vision devices. Low vision specialists recommend appropriate low vision devices and counsel patients on how better to deal with their reduced vision in general. Many government and private organizations exist to aid the visually impaired.

In an article, Augusto Bruix Bayés[3] mentions that the main principle behind low vision is to magnify the image using various tools.

Improving far sight: works best with static objects

Improving near sight: the person must work closer to the object

Improving sensitivity to contrast: the person must use special optical filters

Other tools:

Effectivity of optical aids

In a study performed by this specialist on 1,000 patients, all subjects with a visual acuity above 0.02 decimal (20/1000 feet) significantly improved their vision. From this group, 48% were very satisfied with their visual aids, 44% were satisfied, 5% little satisfied and 3% unsatisfied. Adaptation process to visual aids In the patient's first visit, the most adequate options for their particular case are studied, taking into consideration their psychological, cultural, social and work factors, and the degree of improvement experienced with the selected aids, advising the patient on which aids will yield a better quality of life. After the specific adaptation, there is a follow up to ensure the patient is correctly using and taking the best advantage of the visual aids. In some cases (approx. 4%), the initial visual aids must be changed. Once the patient is released, a report on their first visit and follow up is given to their eye doctor or the professional who made the referral. We believe that low vision, as a complementary technique to ophthalmology, has a great future, due to the progress of science, the increase of life expectancy, and the increasing need people have to access information.

Other aids

For the totally blind, there are books in braille, audio-books, machines and computer programs which transform text files into sound. Low vision people can, of course, make use of these tools as well.

Computers are, precisely, fundamental tools of integration for the visually impaired person. They allow, using standard or specific programs, screen magnification and conversion of text into sound or touch (Braille line), and are useful for all levels of visual handicap. OCR Optical character recognition, usually abbreviated to OCR, is the mechanical or electronic translation of images of handwritten, typewritten or printed text into machine-editable text scanners can, in conjunction with text-to-speech software, read the contents of books and documents aloud via computer. Vendors also build closed-circuit televisions that electronically magnify paper, and even change its contrast and color, for visually impaired users. For more information, consult Assistive technology Assistive technology is a generic term that includes assistive, adaptive, and rehabilitative devices for people with disabilities and includes the process used in selecting, locating, and using them.

Conclusions

An ever-increasing number of people are at risk of visual impairment as populations grow and demographic shifts move towards the predominance of older age groups. Potentially blinding eye conditions such as age-related macular degeneration (AMD), diabetic retinopathy and glaucoma are increasing as the number of people affected grows. These are non-communicable chronic eye diseases to which the principles of long-term care including issues of cost of treatment and compliance (adherence) apply. Additionally, more programmes for those with low vision will need to be made available.[1]

References

  1. ^ a b c d World Health Organization
  2. ^ de Leo et al.: Blindness, Fear of Sight Loss, and Suicide,Psychosomatics 1999; 40:339–344
  3. ^ Baja Visión, 1999

See also

External links

Eye disease The World Health Organization publishes a classification of known diseases and injuries called the International Statistical Classification of Diseases and Related Health Problems or ICD-10. This list uses that classification · pathology Pathology is the study and diagnosis of disease through examination of organs, tissues, bodily fluids, and whole bodies (autopsies). The term also encompasses the related scientific study of disease processes, called General pathology of the eye Eyes are organs that detect light, and send signals along the optic nerve to the visual and other areas of the brain[citation needed]. Complex optical systems with resolving power have come in ten fundamentally different forms, and 96% of animal species possess a complex optical system. Image-resolving eyes are present in cnidaria, molluscs, (H00-H59 lacrimal system: Dacryoadenitis · Epiphora · Dacryocystitis, 360-379 lacrimal system: Dacryoadenitis · Epiphora · Dacryocystitis)
Adnexa cervix/neck eyelid An eyelid is a thin fold of skin that covers and protects an eye. With the exception of the prepuce and the labia minora, it has the thinnest skin of the whole body. The levator palpebrae superioris muscle retracts the eyelid to "open" the eye. This can be either voluntarily or involuntarily. The human eyelid features a row of eyelashes: inflammation (Stye An external stye or hordeolum (/hɔrˈdiːələm/) is an infection of the sebaceous glands of Zeis at the base of the eyelashes, or an infection of the apocrine sweat glands of Moll. External styes form on the outside of the lids and can be seen as small red bumps. Internal styes are infections of the meibomiam sebacious glands lining the inside, Chalazion A chalazion pronounced /kəˈleɪziən/ , also known as a meibomian gland lipogranuloma, is a cyst in the eyelid that is caused by inflammation of a blocked meibomian gland, usually on the upper eyelid. Chalazions differ from styes (hordeolums) in that they are usually painless apart from the tenderness caused when they swell up, and in size (, Blepharitis Blepharitis is an ocular disease characterized by inflammation of the eyelid margins. Blepharitis may cause redness of the eyes, itching and irritation of the eyelids in one or both eyes. Its appearance is often confused with conjunctivitis and due to its recurring nature it is the most common cause of "recurrent conjunctivitis" in older) · Entropion Entropion is a medical condition in which the eyelids fold inward. It is very uncomfortable, as the eyelashes rub against the cornea constantly. Entropion is usually caused by genetic factors and may be congenital. Trachoma infection may cause scarring of the inner eyelid, which may cause entropion · Ectropion Ectropion is a medical condition in which the lower eyelid turns outwards. It is one of the notable aspects of newborns exhibiting Harlequin type ichthyosis. The condition can be repaired surgically. Ectropion is also found in dogs as a genetic disorder in certain breeds · Lagophthalmos Blinking covers the eye with a thin layer of tear fluid, thereby promoting a moist environment necessary for the cells of the exterior part of the eye. The tears also flush out foreign bodies and wash them away. This is crucial to maintain lubrication and proper eye health. If this process is impaired, as in lagophthalmos, the eye can suffer · Blepharochalasis Blepharochalasis is an inflammation of the eyelid that is characterized by exacerbations and remissions of eyelid edema, which results in a stretching and subsequent atrophy of the eyelid tissue. It typically affects only the upper eyelids, and may be unilateral as well as bilateral. In blepharochalasis the eyelid skin becomes lax and falls in · Ptosis Ptosis is an abnormally low position of the upper eyelid. The drooping may be worse after being awake longer, when the individual's muscles are tired. This condition is sometimes called "lazy eye", but that term normally refers to amblyopia. If severe enough and left untreated, the drooping eyelid can cause other conditions, like · Blepharophimosis Blepharophimosis is a condition where the patient has bilateral ptosis with reduced lid size, vertically and horizontally. The nasal bridge is flat and there is hypoplastic orbital rim. Both the vertical and horizontal palpebral fissures are shortened. Vignes (1889) probably first described this entity, a dysplasia of the eyelids · Xanthelasma Xanthelasma is a sharply demarcated yellowish collection of cholesterol underneath the skin, usually on or around the eyelids. Although not harmful or painful, these minor growths may be disfiguring and can be removed. The plural is "xanthelasmata". They are common in people of Asian origin and those from the Mediterranean region · Trichiasis Trichiasis is a medical term for abnormally positioned eyelashes that grow back toward the eye, touching the cornea or conjunctiva. This can be caused by infection, inflammation, autoimmune conditions, and trauma such as burns or eyelid injury · Madarosis Madarosis is derived from the ancient Greek word "madaros" meaning "bald" and is defined as hair loss of the eyebrows or loss of eyelashes (ciliary madarosis). Loss of eyelashes is also known as milphosis. In addition to the obvious cosmetic blemish for which the patient usually presents to dermatologists or ophthalmologists,

lacrimal system The lacrimal apparatus is the physiologic system containing the orbital structures for tear production and drainage: Dacryoadenitis Dacryoadenitis is inflammation of the lacrimal glands . Also described as a blocked tear duct · Epiphora Epiphora is overflow of tears onto the face. A clinical sign or condition that constitutes insufficient tear film drainage from the eyes in that tears will drain down the face rather than through the nasolacrimal system · Dacryocystitis Dacryocystitis is an infection of the nasolacrimal sac, frequently caused by nasolacrimal duct obstruction. The term derives from the Greek dákryon , cyst (sac), and -itis (inflammation). It causes pain, redness, and swelling over the inner aspect of the lower eyelid and epiphora. When nasolacrimal duct obstruction is secondary to a congenital

orbit In anatomy, the orbital bone is the cavity or socket of the skull in which the eye and its appendages are situated: Exophthalmos Exophthalmos is a bulging of the eye anteriorly out of the orbit. Exophthalmos can be either bilateral (as is often seen in Graves' Disease) or unilateral (as is often seen in an orbital tumor). Measurement of the degree of exophthalmos is performed using an exophthalmometer. Complete or partial dislocation from the orbit is also possible from · Enophthalmos It may be a congenital anomaly, or be acquired as a result of trauma, Horner's syndrome, silent sinus syndrome, or phthisis bulbi
Eyeball Eyes are organs that detect light, and send signals along the optic nerve to the visual and other areas of the brain[citation needed]. Complex optical systems with resolving power have come in ten fundamentally different forms, and 96% of animal species possess a complex optical system. Image-resolving eyes are present in cnidaria, molluscs,
Conjunctiva The conjunctiva is a clear mucous membrane consisting of cells and underlying basement membrane that covers the sclera and lines the inside of the eyelids. It is made of epithelial tissue Conjunctivitis Conjunctivitis is an inflammation of the conjunctiva (the outermost layer of the eye and the inner surface of the eyelids), most commonly due to an allergic reaction or an infection (usually viral, but sometimes bacterial). While this article relates generally to humans, animals such as canines (dogs) can experience this condition (Allergic conjunctivitis Allergic conjunctivitis is inflammation of the conjunctiva due to allergy. Although allergens differ between patients, the most common cause is hay fever. Symptoms consist of redness (mainly due to vasodilation of the peripheral small blood vessels), oedema of the conjunctiva, itching and increased lacrimation (production of tears). If this is) · Pterygium Pterygium usually refers to a benign growth of the conjunctiva. A pterygium commonly grows from the nasal side of the sclera. It is associated with, and thought to be caused by ultraviolet-light exposure , low humidity, and dust. The predominance of pterygia on the nasal side is possibly a result of the sun's rays passing laterally through the · Pinguecula It is seen as a yellow- white deposit on the conjunctiva adjacent to the limbus . It is to be distinguished clinically from pterygium, which is a wedge shaped area of fibrosis that appears to grow into the cornea. It is most prevalent in tropical climates and is in direct correlation with UV exposure · Subconjunctival hemorrhage
Fibrous tunic sclera: Scleritis cornea: Keratitis (Herpetic keratitis, Acanthamoeba keratitis, Fungal keratitis) · Corneal ulcer · Snow blindness · Thygeson's superficial punctate keratopathy · Corneal dystrophy (Fuchs', Meesmann) · Keratoconus · Keratoconjunctivitis sicca · Arc eye · Keratoconjunctivitis · Corneal neovascularization · Kayser-Fleischer ring · Arcus senilis · Band keratopathy
Iris and ciliary body Iritis · Uveitis (Intermediate uveitis) · Iridocyclitis · Hyphema · Rubeosis iridis · Persistent pupillary membrane · Iridodialysis · Synechia
Lens Cataract · Aphakia · Ectopia lentis
Choroid Choroideremia · Choroiditis (Chorioretinitis)
Retina Retinitis (Chorioretinitis, Cytomegalovirus retinitis) · Retinal detachment · Retinoschisis · Retinopathy (Bietti's crystalline dystrophy, Coats disease, Diabetic retinopathy, Hypertensive retinopathy, Retinopathy of prematurity) · Macular degeneration · Retinitis pigmentosa · Retinal haemorrhage · Central serous retinopathy · Macular edema · Epiretinal membrane · Macular pucker · Vitelliform macular dystrophy · Leber's congenital amaurosis · Birdshot chorioretinopathy
Optic nerve and visual pathways Optic neuritis · Papilledema · Optic atrophy · Leber's hereditary optic neuropathy · Dominant optic atrophy · Optic disc drusen · Glaucoma · Toxic and nutritional optic neuropathy · Anterior ischemic optic neuropathy
Ocular muscles, binocular movement, accommodation and refraction Paralytic strabismus: Ophthalmoparesis · Progressive external ophthalmoplegia · Palsy (III, IV, VI) · Kearns-Sayre syndrome

Other strabismus: Esotropia/Exotropia · Hypertropia · Heterophoria (Esophoria, Exophoria) · Brown's syndrome · Duane syndrome Other binocular: Conjugate gaze palsy · Convergence insufficiency · Internuclear ophthalmoplegia · One and a half syndrome

Refractive error: Hyperopia/Myopia · Astigmatism · Anisometropia/Aniseikonia · Presbyopia
Visual disturbances and blindness Amblyopia · Leber's congenital amaurosis · Subjective (Asthenopia, Hemeralopia, Photophobia, Scintillating scotoma) · Diplopia · Scotoma · Anopsia (Binasal hemianopsia, Bitemporal hemianopsia, Homonymous hemianopsia, Quadrantanopia) · Color blindness (Achromatopsia, Dichromacy, Monochromacy) · Nyctalopia (Oguchi disease) · Blindness/Low vision
Pupil Anisocoria · Argyll Robertson pupil · Marcus Gunn pupil · Adie syndrome · Miosis · Mydriasis · Cycloplegia
Eye infections Trachoma · Onchocerciasis
Other Nystagmus · Glaucoma/Ocular hypertension · Floater · Leber's hereditary optic neuropathy · Red eye · Keratomycosis · Xerophthalmia · Phthisis bulbi
See also

Categories: Ophthalmology | Optometry

 

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