Blinding means more than just keeping the name of the treatment hidden. Patients may well see the treatment being given to patients in the other treatment group (s), and the appearance of the drug used in the study could give a clue to its identity.
What does it mean to be blind in a clinical trial?
Blinding in clinical trials and other studies. Blinding means more than just keeping the name of the treatment hidden. Patients may well see the treatment being given to patients in the other treatment group (s), and the appearance of the drug used in the study could give a clue to its identity.
What is legal blindness and how is it treated?
The government uses the term “legal blindness” to decide who can get certain benefits, like disability or job training. It is not the same as being totally blind. If you’re completely blind, you can’t see any light or form. Of the people with eye disorders, only about 15% can see nothing at all.
Is it possible to blind a patient to their treatment?
In some cases, while blinding would be useful, it is impossible or unethical. For example, it is not possible to blind a patient to their treatment in a physical therapy intervention. A good clinical protocol ensures that blinding is as effective as possible within ethical and practical constraints.
What is blindness?
Blindness is defined as the state of being sightless. A blind individual is unable to see. In a strict sense the word "blindness" denotes the inability of a person to distinguish darkness from bright light in either eye.
What does blinding mean in clinical trials?
Blinding refers to the concealment of group allocation from one or more individuals involved in a clinical research study, most commonly a randomized controlled trial (RCT).
What does it mean for a study to be blinded?
Listen to pronunciation. (BLINE-ded STUH-dee) A type of study in which the patients (single-blinded) or the patients and their doctors (double-blinded) do not know which drug or treatment is being given.
What is blinding and unblinding in clinical trials?
A clinical trial is called single blind when only one party is blinded, usually the participants....Types of blinding.TypeDescriptionUnblinded or open labelAll parties are aware of the treatment the participant receivesSingle blind or single-maskedOnly the participant is unaware of the treatment they receive2 more rows
What is meant by blinding and double blinding?
In medical trials, the term blinding, or double-blind, usually refers to the practice of keeping patients in the dark as to whether they are receiving a placebo or not. It can also refer to allocation concealment, which is used to avoid selection bias.
What does lack of blinding mean?
The lack of concealment of an intervention or control treatment received by participants in a clinical trial.
What is blinded assessment?
Blind outcome assessment refers to the process of concealing treatment group identity from outcome assessors, after their treatment assignment through randomization, to minimize the occurrence of biased assessments influencing research findings.
What is blinding and what is its purpose?
Blinding is used to prevent conscious or unconscious bias in the design of a clinical trial and how it is carried out. This is important because bias can affect recruitment and allocation, care, attitudes, assessments, etc.
What are the different types of blinding?
4. Types of BlindingTypeDescriptionSingle blind or single-maskedThe participants are blinded but no one else isDouble blind or double-maskedThe participants and clinicians / data collectors are blindedTriple blindThe participants, clinicians / data collectors and outcome adjudicators / data analysts are blinded1 more row
What does unblinding a patient mean?
Unblinding (Code-breaking) Unblinding occurs when that 'blind' is removed, and investigators and/or participants are informed which treatment the participant is receiving.
What is single-blind in psychology?
(SING-gul-blind STUH-dee) A type of clinical trial in which only the researcher doing the study knows which treatment or intervention the participant is receiving until the trial is over. A single-blind study makes results of the study less likely to be biased.
What is double-blind in psychology?
Listen to pronunciation. (DUH-bul-blind STUH-dee) A type of clinical trial in which neither the participants nor the researcher knows which treatment or intervention participants are receiving until the clinical trial is over. This makes results of the study less likely to be biased.
What is triple-blind?
Triple-blind (i.e., triple-masking) studies are randomized experiments in which the treatment or intervention is unknown to (a) the research participant, (b) the individual(s) who administer the treatment or intervention, and (c) the individual(s) who assess the outcomes.
What is blinding in clinical research?
Blinding refers to the concealment of group allocation from one or more individuals involved in a clinical research study, most commonly a randomized controlled trial (RCT). Although randomization minimizes differences between treatment groups at the outset of the trial, it does nothing to prevent differential treatment ...
Why is blinding important in RCTs?
Blinding is an important methodologic feature of RCTs to minimize bias and maximize the validity of the results. Researchers should strive to blind participants, surgeons, other practitioners, data collectors, outcome adjudicators, data analysts and any other individuals involved in the trial.
When data collectors or outcome adjudicators cannot be blinded, should they be?
When data collectors or outcome adjudicators cannot be blinded, researchers should ensure that the outcomes being measured are as objective as possible. Furthermore, the outcomes should be reliable (although reliable outcomes are preferable whether or not the assessors are blinded).
When patients or clinicians cannot be blinded, should trialists ensure that the 2 (or more) allocation
When patients or clinicians cannot be blinded, trialists should ensure that the 2 (or more) allocation groups are, apart from the intervention, treated as equally as possible. This may involve standardizing the care of participants such as cointerventions, frequency of follow-up and management of complications.
Is blinding more difficult to do in surgical trials?
Blinding is unequivocally more difficult to incorporate in trials of surgical interventions than in trials of medical therapie s.10–12Whereas medical trials usually incorporate placebo medications to achieve blinding, surgical treatments often result in incisions and scars that may differ between groups.
Is it harder to blind a surgical intervention?
Randomized controlled trials of surgical interventions are frequently more difficult to blind than RCTs of medications, which typically achieve blinding with placebos. However, imaginative techniques may make blinding more feasible in surgical trials than is commonly believed by many researchers.
Should researchers consider blinding each individual involved in a trial separately?
Researchers should consider methods to blind each individual involved in a trial separately and search for the simplest, least invasive technique of achieving blinding. Determining the feasibility of blinding patients is usually simple.
What are the criteria to be legally blind?
To be considered legally blind, you would have to meet one of two criteria for visual acuity (sharpness of vision) and visual field (the entire scope of what you can see without moving your eyes).
What causes legal blindness?
Age-related eye diseases that are the leading causes of low vision and blindness are: 6 . Eye trauma or injuries and genetic conditions, such as Usher syndrome, can also lead to legal blindness.
How far away can you see with 20/20 vision?
If you had visual acuity of 20/80, it would mean that you would be able to see details from 20 feet away the same as a person with 20/20, or normal, vision could see from 80 feet away. A legally blind person with 20/200 vision (with the best corrective lenses) would need to be 20 feet from an object in order to see it as well as someone ...
What is low vision?
Low vision is a visual acuity of 20/40 or worse while wearing corrective lenses. More than 4.2 million people over age 40 are legally blind or have low vision, according to the Centers for Disease Control and Prevention. 6 . Visual Acuity Testing.
How to treat glaucoma?
For example, the goal of treatment for glaucoma is to reduce eye pressure. This can be achieved with prescription eye drops or oral medications, laser procedures, and, in severe cases, surgeries to try to prevent further damage.
What is visual field testing?
Visual field testing often begins with a confrontational visual field test in which you an eye doctor has you cover one eye at a time and then holds up one or more fingers in different quadrants of the visual field to see if you can see them while keeping your eyes focused on a central point in front of you.
Can you get a driver's license if you are blind?
2 For safely reasons, people with legal blindness or low vision typically are not eligible for a driver's license.
What does it mean when you are completely blind?
A completely blind individual is unable to see at all . The word blindness, however, is commonly used as a relative term to signify visual impairment, or low vision, meaning that even with eyeglasses, contact lenses, medicine or surgery, a person does not see well. Vision impairment can range from mild to severe.
How can blindness be prevented?
Most traumatic causes of blindness can be prevented through eye protection. Nutritional causes of blindness are preventable through proper diet. Most cases of blindness from glaucoma are preventable through early detection and appropriate treatment.
Why do I get snow blind?
Snow blindness is usually temporary and is due to swelling of cells of the corneal surface. Even in the most severe cases of snow blindness, the individual is still able to see shapes and movement. People often say, "I am 'blind as a bat' without my glasses.".
Why are people blind in third world countries?
In third-world nations where many people have poor vision as a result of a refractive error, merely prescribing and giving glasses will alleviate the problem. Nutritional causes of blindness can be addressed by dietary changes. There are millions of people in the world who are blind from cataracts.
What causes blindness in older people?
Common causes of blindness include diabetes, macular degeneration, traumatic injuries, infections of the cornea or retina, glaucoma, and inability to obtain any glasses.
What is temporary blindness?
Temporary blindness differs in causes from permanent blindness. The diagnosis of blindness is made by examination of all parts of the eye by an ophthalmologist. The universal symptom of blindness or visual impairment is difficulty with seeing.
How many people are blind in the world?
Worldwide, between 300 million-400 million people are visually impaired due to various causes. Of this group, approximately 50 million people are totally blind. Approximately 80% of blindness occurs in people over 50 years of age.
What is blinding in a trial?
It is a tenet of randomised controlled trials that the treatment allocation for each patient is not revealed until the patient has irrevocably been entered into the trial, to avoid selection bias.
Why is blinding important in epidemiology?
Blinding is important in other types of research too. For example, in studies to evaluate the performance of a diagnostic test those perform ing the test must be unaware of the true diagnosis.
What is double blinding in clinical trials?
In controlled trials the term blinding, and in particular “double blind,” usually refers to keeping study participants, those involved with their management, and those collecting and analysing clinical data unaware of the assigned treatment, so that they should not be influenced by that knowledge.
Can patients see the treatment being given to patients in the other treatment group?
Patients may well see the treatment being given to patients in the other treatment group (s), and the appearance of the drug used in the study could give a clue to its identity. Differences in taste, smell, or mode of delivery may also influence efficacy, so these aspects should be identical for each treatment group.
Is blinding always possible?
Blinding is certainly not always easy or possible. Single blind trials (where either only the investigator or only the patient is blind to the allocation) are sometimes unavoidable, as are open (non-blind) trials. In trials of different styles of patient management, surgical procedures, or alternative therapies, full blinding is often impossible.
What does it mean to be legally blind?
Being classified as legally blind means you are unable to drive in any state. Talk to your doctor about your concerns. You can't diagnose yourself with the condition. Your doctor has to make that call, so let them know if you're having eye trouble.
How far can you see if you are blind?
That means you can clearly see an object 20 feet away. If you’re legally blind, your vision is 20/200 or less in your better eye or your field of vision is less than 20 degrees. That means if an object is 200 feet away, you have to stand 20 feet from it in order to see it clearly.
Is Uncle Sam blind?
You might be surprised to learn that it’s Uncle Sam, not the doctor, who defines whether you’re legally blind. The government uses the term “legal blindness” to decide who can get certain benefits, like disability or job training. It is not the same as being totally blind. If you’re completely blind, you can’t see any light or form.
What is legal blindness?
Legal blindness, that level which would qualify the patient for social and government purposes and benefits as “blind”, is usually determined to be 20/200 or below. With that level of vision a person may not be able to read, or drive, or recognize faces very well, but can still get around the house and in society at a level which many folks would ...
How many people are legally blind?
Fortunately, perhaps as few as 10 or 15% of all people who qualify as “blind” are absolutely blind The rest have levels of sight which range from the ability to perceive light up to levels which would qualify as “legally blind”.
What are the two aspects of vision that determine legal blindness?
There are two different aspects of vision that determine legal blindness: decreased visual acuity (sharpness) and an extremely narrow field of vision. You can have perfect visual acuity but a narrow field of vision (or a normal field of vision with low visual acuity) and still be considered legally blind.
What is visual acuity?
Visual acuity is how far you can see clearly. This is measured with the Snellen Visual Acuity Test, which is the traditional eye chart that features letters of different sizes.
Why is blinding important?
In some fields, such as medicine, it is considered essential. In clinical research, a trial that is not a blinded trial is called an open trial .
What is unblinding in pharmacology?
Unblinding is common in blinded experiments , particularly in pharmacological trials. In particular, trials on pain medication and antidepressants are poorly blinded. Unblinding that occurs before the conclusion of a study is a source of experimental error, as the bias that was eliminated by blinding is re-introduced.
Why is unblinding a common cause?
A common cause for unblinding is the presence of side effects (or effects) in the treatment group. In pharmacological trials, premature unblinding can be reduced with the use of an active placebo, which conceals treatment allocation by ensuring the presence of side effects in both groups.
When does unblinding occur?
Unblinding occurs in a blinded experiment when information becomes available to one from whom it has been masked. In clinical studies, unblinding may occur unintentionally when a patient deduces their treatment group. Unblinding that occurs before the conclusion of an experiment is a source of bias.
Why do symphony orchestras have blind tests?
Blind tests can also be used to compare the quality of musical instruments.
How many blinded trials are there for acupuncture?
While the possibility of blinded trials on acupuncture is controversial, a 2003 review of 47 randomized controlled trials found no fewer than four methods of blinding patients to acupuncture treatment: 1) superficial needling of true acupuncture points, 2) use of acupuncture points which are not indicated for the condition being treated, 3) insertion of needles outside of true acupuncture points, and 4) the use of placebo needles which are designed not to penetrate the skin. The authors concluded that there was "no clear association between type of sham intervention used and the results of the trials."
What is a blinded experiment?
Experiment in which information about the test is masked to reduce bias. In a blind or blinded experiment, information which may influence the participants of the experiment is withheld (masked or blinded) until after the experiment is complete. Good blinding can reduce or eliminate experimental biases that arise from a participants' expectations, ...
What is color blindness?
Color blindness, or color vision deficiency, refers to the inability of a person to correctly distinguish certain colors. Color vision problems range from the inability to see different shades of a color to not being able to see certain colors at all.
How to tell if you are color blind?
The most common test for diagnosing color blindness is the Ishihara test. This quick and simple test consists of a series of pictures made up of colored dots. Among the dots is a figure, usually a number, made up of dots of a different color. A person with normal color vision will be able to see the number, but a color blind person will see a different number or no number at all.
What percentage of people are color blind?
About eight percent of men and one percent of women are color vision deficient. More males are affected by the disorder than females. Occasionally, certain eye diseases cause color blindness, referred to as "acquired color blindness.". Aging can also cause the disorder; as the lens darkens with age, older people may find it difficult ...
Is it rare to be color blind?
Many people mistakenly believe that to be color blind is to view the world in only black and white, but complete color blindness is rare. A color blind person usually has problems distinguishing between the colors red and green, mistaking them for the same color. A less common type of color blindness involves the colors blue and yellow.
Can a color blind person see a number?
A person with normal color vision will be able to see the number, but a color blind person will see a different number or no number at all. Another test used to diagnose color blindness is called an arrangement test, in which the patient is asked to arrange a group of colored chips in a particular order.
Meaning
Diagnosis
- An eye doctor measures visual acuity and visual field to determine if a person is legally blind, and whether wearing glasses or contact lenses could improve their vision. A common test for visual acuity is the Snellen eye chart. Someone who is legally blind would be able to read only the top line of the chart (a capital E) while wearing corrective lenses. The line below the big E is the line f…
Causes
- There are many conditions that can lead to legal blindness, but the most common ones are age-related. In many cases, early diagnosis and treatment for these can prevent blindness. They include:6 1. Age-related macular degeneration 2. Cataracts(cloudiness of the clear lens of the eye) 3. Diabetic retinopathy (a complication of diabetes) 4. Glaucoma Eye trauma or injuries an…
Treatment
- Treatments for legal blindness vary depending on the cause and the stage of the disease that has caused the loss of vision. For age-related eye diseases, treatments typically involve prescription medications or eye procedures to try to delay or keep the vision from worsening. The goal of treatment for glaucoma is to reduce eye pressure. This can be...
Prevention
- The best way to prevent vision loss is to take care of your overall health (including your eyes). Seeing your healthcare provider regularly and getting your eyes examined can help alert you to conditions, like diabetes, that could impact your sight. Other steps you can take to safeguard your sight include maintaining a healthy weight (which could put you at risk of developing diabetes), …
Summary
- Most people who are legally blind have some vision. And to be deemed "legally blind," their vision must be bad enough that they meet one of two standards: They must have a visual acuity of 20/200 or less in the eye they can see out of best (while wearing corrective glasses or contacts) or have a visual field of no more than 20 degrees. Ophthalmologists have several tests at their di…
A Word from Verywell
- Low vision or legal blindness can be limiting, but there are many resources and assistive devices to help you live your life with a spirit of independence. Depending on the cause of your vision loss, you may be able to benefit from eye exercises and strategies for participating in everyday activities. You may also find that using a cane, talking calculator, special computer software, or …