Eye Charts

• Classic Eye Chart: Joel Schneider's 3-page Snellen Chart plus near vision testing card
  
  • in PDF
  • PostScript source code
• Modern Standard: ETDRS charts based on those provided on the National Eye Institute's charts page. The following charts have correctly-labelled lines from 40ft to 2ft suitable for printing on letter sized paper, and feature vector graphics for a sharper image (unlike the maximum 300dpi, not-to-scale charts provided by the N.E.I.).
  
  • Chart R
  • Chart 1
  • Chart 2
• Interactive Eye Chart: Alejandro Saksida's Flash-based Ultimate Random Snellen Chart generator, version 3.1 (updated January 12, 2006):
  
  • Read Instructions.
  • Generate a Random Snellen Chart on the web.
  • Download a ZIP Archive of the generator for off-line use.
• Vision Training Charts from Ray Gottlieb, O.D., Ph.D., with instructions.
  
  • Presbyopia Reduction Chart (PDF) -- helps you read fine print by training convergence. Part of the Read Without Glasses Method, courtesy of the Cambridge Institute for Better Vision
  • String Of Pearls (PDF) -- for improving 3D perception
• Alex Eulenberg's 1-page Snellen Chart (20/20)
  
  • in GIF format (browser-viewable, also printable at 72 dpi)
  • in Macintosh PICT format (hi-resolution, downloadable & printable)
  • in Encapsulated PostScript (.eps) format (compatible with, among other programs, WordPerfect for Windows.)
  • in PDF format.
• Vic Cinc's Letter rows & grid of random tumbling E's
  
  • in PDF format
  • in PostScript format
• Vic Cinc's Astigmatic mirror
• Egidio Rizzi's Vision Charts for Eyesight Improvement -- 10 charts for practicing fusion, convergence, divergence, with notes on each exercise's applicability for nearsightedness, farsightedness, and astigmatism.

Make your own eye chart!

For those enterprising souls out there who would like to laserprint or draw by hand their own eye chart, or if you would like to verify that your printout is of the correct proportions, here are the specs:

Distance (feet)  70   60    50    40    30    20    15    10    7    4
letter ht (mm)   31   27    22    18    13     9     7     4    3    2
letter ht (pt)   88   76    63    50    38    25    19    13    9    5
font size (pt)  152  130   108    87    65    43    33    21   15    9

With the University at Buffalo's Interactive Visual Acuity Chart, you can display the letters or symbols for a specified Snellen line on your computer monitor at exactly the right size (note: you must follow the instructions for calibration).

Interpreting the table

"Distance" in the above table refers to the furthest distance from the chart at which a normal eye is able to read the letter. On a Snellen eye chart, rows of letters of a given size have the corresponding distance number next to them. Thus the row of 18mm letters is marked "40". The font must be Courier (or Courier Bold) in order for the "font size" in points to correspond to the indicated letter height. Courier Bold is the PostScript font that most closely approximates the official Snellen letters.

Visual Acuity

by Wendy Strouse Watt, O.D.
October 2003
A standard eye chart is necessary to make comparisons and to record people's visual acuity. The most common chart used in most doctors' offices is the Snellen eye chart. In 1862, a Dutch Ophthalmologist, Dr. Hermann Snellen, devised this eye chart. He determined that there was a relationship between the sizes of certain letters viewed at certain distances. A copy of the Snellen chart may be found here.
The Snellen eye chart has a series of letters or letters and numbers, with the largest at the top. As the person being tested reads down the chart, the letters gradually become smaller. Many other versions of this chart are used for people who cannot read the alphabet. The Tumbling E chart has the capital letter "E" facing in different directions and the person being tested must determine which direction the "E" is pointing, up, down, left, or right. A Broken Wheel vision test is one that can be used for children or those who cannot read the alphabet and the person being tested must tell which card has the broken wheels on the pictured car. Another type of eye chart that can be used is a picture chart with common pictures of different sizes. In research, another chart, the ETDRS chart, has become the standard. Originally, the chart was used in the Early Treatment of Diabetic Retinopathy Study.
The Snellen fractions, 20/20, 20/30, etc., are measures of sharpness of sight. They relate to the ability to identify small letters with high contrast at a specified distance. They give no information about seeing larger objects and objects with poor contrast (such as steps and curbs); it also does not inform us as to whether or not meaning is obtained from visual input, how much effort is needed to see clearly or singly, and whether or not vision is less efficient when using both eyes as opposed to each eye individually. In short, visual acuity measures only the smallest detail we can see; it does not represent the quality of vision in general.
August Colenbrander, M.D. (Smith-Kettlewell Eye research Institute and California Pacific Medical Center) offers a good explanation of acuity measurement. He says: "If a subject needs letters (or symbols) that are twice as large or twice as close as those that can just be seen by a standard eye, visual acuity is said to be 1/2 (or an equivalent fractional value, such as 20/40, 6/12, etc.). If the magnification need is 5x, visual acuity is 1/5 (20/100, 6/30, etc.), and so on."
Dr. Colenbrander also emphasizes that, contrary to popular belief, 20/20 is not actually normal or average, let alone perfect, acuity. Snellen, he says, established it is a reference standard. Normal acuity in healthy adults is one or two lines better. Average acuity in a population sample does not drop to the 20/20 level until age 60 or 70. This explains the existence of the two lines smaller than 20/20: 20/15 and 20/10.
When checking visual acuity, one eye is covered at a time and the vision of each eye is recorded separately, as well as both eyes together. In the Snellen fraction 20/20, the first number represents the test distance, 20 feet. The second number represents the distance that the average eye can see the letters on a certain line of the eye chart. So, 20/20 means that the eye being tested can read a certain size letter when it is 20 feet away. If a person sees 20/40, at 20 feet from the chart that person can read letters that a person with 20/20 vision could read from 40 feet away. The 20/40 letters are twice the size of 20/20 letters; however, it does not mean 50% vision since 20/20 sounds like it is one half of 20/40. If 20/20 is considered 100% visual effiency, 20/40 visual acuity is 85% efficient.
If a patient sees 20/200, the smallest letter that they can see at 20 feet could be seen by a normal eye at 200 feet. This is the Snellen Acuity (English). In Metric Acuity, 20/20 equals 6/6. The conversion is that 20 feet equals approximately 6 meters (actually 6.096).

Metric 6/3 6/4.5 6/6 6/7.5 6/9 6/12 6/15 6/30 6/60

Snellen 20/10 20/15 20/20 20/25 20/30 20/40 20/50 20/100 20/200

For people who have worse than 20/400 vision, a different eye chart can be used that measures beyond 20/400 vision, or, for the most accurate measurements, a Low Vision Chart can be moved closer to the patient to measure the smallest letter that they can see at a lesser distance. It is common to record vision worse than 20/400 as Count Fingers (CF at a certain number of feet), Hand Motion (HM at a certain number of feet), Light Perception (LP), or No Light Perception (NLP). The conversion of Snellen Acuity to Count Fingers Acuity is as follows:

20/800 20/1000 20/1143 20/1333 20/1600 20/2000 20/2666 20/4000 20/8000

CF10' (Count Fingers at ten feet) CF 8' CF 7' CF 6' CF 5' CF 4' CF 3' CF 2' CF 1'

Prescriptions for eyeglasses are measured in diopters. The measurement starts at zero ("plano"), with four quarters to a diopter: 0.25 (a quarter diopter), 0.50 (one half a diopter), 0.75 (3/4 of a diopter), and 1.00 (one diopter). The higher the numbers, the higher (stronger) the prescription.Here are estimates for the approximate correction needed for each line seen on the Snellen chart:

Snellen 20/10 20/15 20/20 20/30 20/40 20/50 20/100 20/200

Estimated prescription Plano (zero) Plano Plano to -0.25 -0.50 -0.75 -1.00 to -1.25 -1.75 to -2.00 -2.00 to -2.50

This estimation works best for myopia (nearsightedness) because hyperopic (farsighted) people can focus and compensate for a certain amount of their prescription. The Snellen fractions cannot be used for ordering a pair of glasses or contacts that will correct a person's vision.
Legal Blindness is when a person's best-corrected vision is 20/200 or worse. If a person is legally blind, they can qualify for tax breaks and certain federal and state social services, such as help in purchasing magnifiers and other low vision aids.

Snellen charts 
This is the same chart that your doctor uses to determine your visual acuity. The normal height for the letter A is 88 mm, and the viewing distance is 6 meters.
To properly view the chart on your monitor:

• Measure the height of the letter A in millimeters.
• Divide by 88.
• Multiply by 6.

The final number is the distance (in meters) that you should stand from the monitor. For information on using the chart to determine your visual acuity, see "How Visual Acuity Is Measured" in the MD Support Library.

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The Optometric Oath

With full deliberation I freely and solemnly pledge that: I will practice the art and science of optometry faithfully and conscientiously, and to the fullest scope of my competence. I will uphold and honorably promote by example and action the highest standards, ethics and ideals of my chosen profession and the honor of the degree, Doctor of Optometry, which has been granted me.

I will provide professional care for those who seek my services, with concern, with compassion and with due regard for their human rights and dignity.

I will place the treatment of those who seek my care above personal gain and strive to see that none shall lack for proper care.

I will hold as privileged and inviolable all information entrusted to me in confidence by my patients.

I will advise my patients fully and honestly of all which may serve to restore, maintain or enhance their vision and general health.

I will strive continuously to broaden my knowledge and skills so that my patients may benefit from all new and efficacious means to enhance the care of human vision.

I will share information cordially and unselfishly with my fellow optometrists and other professionals for the benefit of patients and the advancement of human knowledge and welfare. I will do my utmost to serve my community, my country and humankind as a citizen as well as an optometrist.

I hereby commit myself to be steadfast in the performance of this my solemn oath and obligation.

--
Tanvir Akhtar
BS(Hons) Optometry
Pakistan

Code of Ethics

• PDF Version

It shall be the ideal, resolve, and duty of all optometrists:

TO KEEP their patients' eye, vision, and general health paramount at all times;

TO RESPECT the rights and dignity of patients regarding their health care decisions;

TO ADVISE their patients whenever consultation with, or referral to another optometrist or other health professional is appropriate;

TO ENSURE confidentiality and privacy of patients' protected health and other personal information;

TO STRIVE to ensure that all persons have access to eye, vision, and general health care;

TO ADVANCE their professional knowledge and proficiency to maintain and expand competence to benefit their patients;

TO MAINTAIN their practices in accordance with professional health care standards;

TO PROMOTE ethical and cordial relationships with all members of the health care community;

TO RECOGNIZE their obligation to protect the health and welfare of society; and

TO CONDUCT themselves as exemplary citizens and professionals with honesty, integrity, fairness, kindness and compassion

Adopted by the House of Delegates as:
Substantive Motion M-1944-1, June 1944; Modified June 2005; Repealed June 2007
Modified and Adopted as Resolution #1969, June 2007

--
Tanvir Akhtar
BS(Hons) Optometry
Pakistan

Job Descriptions

Job Descriptions approved by the National Steering Committee for the prevention and control of blindness in Pakistan.


Ophthalmic Technician (Level I)
Minimum of one year time training in an accredited institution.
should make an important team member with the ophthalmologist;
note down the presenting complaints of the patients;
Ask the patient about common systemic diseases like diabetes, hypertension;
Ask the patient about the family history of common eye and systemic disease
(cataract, glaucoma, corneal, diabetes and hypertension)
Ask the patient about the use of any drug and allergy or hyper-sensitivity to any drug;
Detection and referral of common causes of blindness and visual impairment;
Health education and counseling;
Prescribe Vitamin A capsule/drops and Tetracycline, as appropriate;
Can use mydratics and local anesthetic with caution and responsibility
as advised by ophthalmologist;
Can remove superficial conjunctival foreign bodies
Can assess visual acuity for near and far, use pinhole, measure IOP,
and use of auto-refract meter;
Assist the Ophthalmologist in the operation theater and out-patient department;
Basic care and maintenance of ophthalmic equipments;
Maintain the record of ophthalmic unit manually and computerized;
Participation in community based eye health programs like school eye health,
trachoma control program, prevention of childhood blindness program etc.

Refractionist (Level II)
Minimum of two years full time training in an accredited institution
Can perform all the functions of level I;
Carry out refraction of all patients whose visual acuity improves with pinhole;
Assess the refractive state of a child 3 years and above using cycloplegic agent;
Basic vision function assessment including assessment of visual fields, contrast
and binocular visual function; contrast sensitivity
Screening of ocular pathologies at out patient department/ field and referral to
appropriate specialist;
Be able to carry out basic fundus examination using a direct Ophthalmoscope.
Performs any other relative assignment by the department;
Maintain records of ophthalmic unit and reporting;
Supervise school and community eye health screening programmes;
Coordinate and impart training to primary health workers and teachers;
Contribute to the eye health promotion activities;
Contribute to eye health and blindness surveys;
Carry out basic low vision assessment and prescribe LVDs from a defined range.

Optometrist (Level III)
Minimum of four year's full time training leading to
a university degree in an accredited institution
World Council of Optometry (WCO) defines optometrist as follows:
Optometrists are the primary health care practitioners of the eye and
visual system who provide comprehensive eye and vision care, which
includes refraction and dispensing detection/diagnosis and management of
diseases in the eye, and the rehabilitation of conditions of the visual system."
In the light of the above, the following job description is recommended for Pakistan.
Can perform all the functions of level II
Can perform the additional skills acquired:
Advanced refraction including refraction of all children
Low vision assessment
Prescribe hard and soft contact lens
Carry out advance visual function assessment
Detection/diagnosis and referral of diseases of eye
Can act as faculty member and trainer for level I and I
and other relevant cadres
Engage in operational and field research;
manage record keeping, analysis, and reporting;
Participate and lead on various eye campaigns.

Orthoptists (Level III)
Orthoptic assessment and non surgical management;
Visual function assessment especially in children;
Pediatric refraction / assessment including cycloplegic refraction;
Engage in research related to BSV anomalies;
Performs any other relevant field of expertise;
Record keeping and reporting.

Ophthalmic Technologist (Level III)
Assist ophthalmologist in LASER;
Perform the Diagnostic procedures like FFA (in presence of a doctor), A& B-Scan
Biometry, Perimetry Electrophysiological test and any other non-invasie advanced diagnostic procedures.
Maintenance of instrument & equipments.
Engage in operational and field research;
Teaching and training in the relevant field;
Perform any other relevant assignment by the department;
Record keeping an


Muhammad Rashid
Optometrist
Contact Lens Clinic
Al-Shifa Trust Eye Hospital
Rawalpindi
Pakistan
+923332645162