Lecture 1 - Epidemiology, Terminology and Classification

The international classification of diseases II classifies vision impairement into 2 groups: ________ and ________ presenting vision impairment

Distance and near

In total (distance and near) it's estimated ___________ people have a vision impairment

2.2 billion

According to WHO, what are the presenting VAs to classify mild, moderate, severe, and blind

Mild: worse than 20/40
Moderate: worse than 20/160
Severe: worse than 20/200
Blindness: worse than 20/400

How many people globally have distance vision impairments? How many are blind?

285 million; 36 million blind

What VA is considered a near visual impairment?

20/50

How many people globally have near vision impairment simply because they do not own a pair of spectacles?

1.1 billion

___% of the World's visually impaired live in developing countries, and most are older than ____ years old

90%; 60 years old

List some possible causes of global blindness

1. Uncorrected refractive error
2. Cataracts
3. Glaucoma
4. Trachoma
5. Corneal opacification
6. DR
7. AMD

_____% of visual impairment is avoidable

75%

What is the estimated number of children blind globally?

1.4 million

What are the leading causes of childhood blindness?

1. Congenital cataracts (undeveloped countries)
2. Optic atrophy
3. Albinism
4. Retinopathy of prematurity (developed countries)
5. Genetic diseases (retinal)

_______ million children have a sight condition that requires treatment, with many unable to access affordable, available eye care

450 million

Children in low and middle income countries with vision loss are _____x less likely to be in school

2-5x

How is visual impairment and blindness defined in the US (based on VA)

Visual Impairment = 20/40 to 20/200
Blindness = >/= 20/200

In 2015, ________ people in the US were visually impaired, in 2050, it is estimated to rise to _______ people

3.22 million; 6.95 million

In 2015, ________ people in the US were legally blind, in 2050, it is estimated to rise to ______ people

1.02 million; 2.01 million

In the US, ___% of people with low vision are over the age of _____

90%; 65 years old

Both blindness and visual impairment are projected to _____ by 2050 in the US

Double

Currently, the highest prevalence of visually impaired and blind individuals is among which ethnic population and gender in the US?

Non-Hispanic white women

Which states have the highest per capita rates of visual impairment? The lowest?

Highest:
1. District of Columbia
2. Florida
3. Mississippi
4. Hawaii
5. Pennsylvania

Lowest:
1. Alaska
2. Utah
3. Colorado
4. Nevada
5. Washington

What is the gold standard classification system for categorizing vision impairment and blindness?

International Classification of Diseases 11th Edition (ICD-11)

(Established by WHO)

True or false: ICD-11 defines legal blindness in the US

False; it does not

What is legal blindness? (Definition)

"Legal blindness", or statutory blindness, is a definition used by the US government to determine eligibility for vocational training, rehabilitation, schooling, disability benefits, low vision devices, and tax exemption programs

It is NOT a functional definition and doesn't explain very much at all about what a person can and cannot see

True or false: there is a difference between statutory blindness and qualifying for disability

True

Who determines legal blindness? (Organizations)

1. The Social Security Act
2. Individual states can adopt additional registration allowance for patients with functional loss of vision without measurable outcome
3. State governments are responsible for the registration and distribution of eligible state benefits

True or false: state registries are always connected to the Registry of Motor Vehicles

False; usually but not always

List the various benefits of statutory blindness

1. Monthly income-disability income payments
2. Supplemental Security Income
3. Health coverage through Medicare
4. Deductions on income tax, automobile excise tax, real estate tax, and medical deductions
5. Vocational rehab services and job training programs
6. Free public transportation and regional transportation assistance
7. Free mailing, telephone directory, library and other public services
8. Services and possibly income support from Veterans Administration for eligible veterans

Who registers patients as legally blind?

You do!! When a patient meets the requirements during an eye exam, depending on what state the OD is practicing, the OD may be legally obligate to register the patient (ex. Massachusetts Commission for the Blind)

What is the criteria for legal/statutory blindness in the US?

1. BCVA 20/200 or less in the better eye
OR
2. VF has 20 degree or less at widest diameter with Goldmann III4e, regardless of VA

True or false: if a patient can identify any letter on the 20/100 line then they are NOT legally blind

True

Snellen charts do not have optotypes between 20/100 and 20/200

When testing for function, ________ can be used. When testing for legal purposes/legal blindness, _______ must be used

Eccentric viewing, central fixation

Your patient reads 20/200 before refraction. Assuming they have a full VF, are they legally blind?

No! You haven't done refraction yet and legal blindness is best corrected VA!

You refract and your patient is still 20/200. Are they legally blind?

Yes!

What if someone's BCVA is 20/125, are they legally blind?

Yes. As long as they do not read ANY letters on the 20/100 line they are considered legally blind

What is their vision improves to 20/100 but they are using eccentric viewing?

Yes, they are still legally blind because they are using eccentric viewing and not central viewing

A patient has entering acuity of 20/200, and pinholes to 20/100 but during refraction you can only get them to read 20/125. Are they legally blind?

Yes! Pinhole does not count as best corrected VA

Your patient has BCVA 20/200 with glasses and 20/80 with contacts, but they have tried learning how to take them out and they just can't do it so they've decided to wear glasses full time. Are they legally blind?

Yes. CLs are only allowed to be considered if the patient shows ability to use them on a sustained basis

BCVA is 20/200 but with a 3x telescope they can read 20/80. Are they legally blind?

Yes! Telescopes cannot be used to determine best corrected acuity

Legal blindness is determined as VF of ______ degrees or less at widest diameter in the _______ eye (with Goldman III4e white stimulus)

20 degrees; better eye

Your patient reads 20/20 but has 20 degrees of VF in the right eye and 30 degrees of central field in the left eye. Are they legally blind?

No!

Your patient has 10 degrees of central VF in the right eye and 10 degrees of central VF in the left eye. Are they legally blind?

Yes!

In automated static threshold perimetry, the _______ of the stimulus varies

Intensity

To determine legal/statutory blindness, we measure teh extent of visual field loss by determining the portion of the VF in which the individual can see _________ stimulus

White III4e

What do the Roman numerals mean in the "III4e stimulus"

Refers to the standard Goldmann test stimulus size III

What do the Arabic numeral and letter mean in the "III4e stimulus"?

Refers to the standard Goldmann filters used to determine the intensity of the stimulus

How many degrees are the temporal, nasal, superior, and inferior fields?

Temporal = 90 degrees
Nasal = 60 degrees
Superior = 60 degrees
Inferior = 70 degrees

Each hash mark on the x and y axis of the VF corresponds to ____ degrees of VF

10 degrees

The blind spot is ______ degrees temporal where the optic nerve leaves the eye

15 degrees

The average blind spot is ______ degrees in diameter, vertically centered ________ degrees below the horizontal meridian

7.5 degrees; 1.5 degrees

Each point on a HVF is _______ degrees apart horizontally or vertically from any adjacent point

6 degrees

Any tested point adjacent to an axis is ______ degrees from that axis

3 degrees

The 4 tested points immediately surrounding the point of fixation are each _____ degrees horizontally and vertically from the point of fixation

3 degrees

The _______ numbers are a measure of the patient's ability to see dim stimuli

Decibel (dB)

What is the expected decibel norm on a HVF?

30

0-20 dB on a HVF indicates what?

Indicates low sensitivity and significant field loss

What does >40 dB on a HVF indicate?

Hypersensitivity; patient may be trigger happy, usually indicating unreliable results

What does it mean if 2 dB values are present in one test location on a HVF?

This point was retested. The higher value of the two should be used

_____dB threshold with Humphrey is equivalent to a 4e intensity on Goldman

10dB

review image on slide 49

How do we measure the widest diameter of the VF?

We create a "pseudoisopter" to designate the seeing area from the non-seeing area.

The diameter must go through the point of fixation and is drawn midway between any 2 adjacent tested points when one threshold is 10dB or greater and the other threshold is less than 10dB

A monocular patient (due to traumatic injury) has a VA of 20/30- and a VF of 120 degrees horizontally in the seeing eye. Are they legally blind?

No!

What is visual efficiency?

What is visual acuity efficiency?

Combination of VA efficiency and VF efficiency expressed as a %

Percentage that corresponds to BCVA in the better eye

What is VF efficiency?

Percentage that corresponds to VF in the better eye using kinetic perimetry

True or false: functional vision = measurable vision

False; common misconception

Visually impaired patients can experience functional impairments as a result of what 5 things?

1. Reduced VA
2. Decreased CS
3. Discomfort and disability glare
4. Loss of or relative reduction of either central or peripheral VF
5. Cortical processing of visual input