Computer Vision Problems

Computer vision problems or Digital eye strain is a group of eye and vision problems. The problems can include eyes that itch and tear, and are dry and red. Your eyes may feel tired or uncomfortable. You may not be able to focus normally. These problems are caused by lots of computer or digital device use. Using e-readers and smartphones may also cause these problems.

These problems have been increasing in frequency over the past few decades. Many people have some symptoms if they use a computer or digital device for long periods. Most computer or digital device users have symptoms at least some of the time. Digital eye strain is very common in both children and adults.

What causes digital eye strain?

For many reasons, reading text on a computer screen or digital device is often harder for the eyes than reading printed text. This is why working on a computer for a few hours may cause symptoms of digital eye strain, but reading a book may not.

Several factors help to cause digital eye strain, such as:

Screen glare
Poor lighting
Poor posture while using a computer
Viewing a computer at the wrong distance and angle
Uncorrected vision problems
A combination of many of these factors

People often blink less when using a computer than when reading printed text. This can cause dry eye, This may contribute to digital eye strain.

Who is at risk for getting digital eye strain?

You may be at greater risk for digital eye strain if you:

Spend a few hours or more a day at a computer or on a digital device
Are too close to your computer or digital device screen
View your computer or digital device at the wrong angle
Have bad posture while using your computer or digital device
Have eye problems (even minor ones) not corrected with glasses or contact lenses
Have a pair of glasses that is not suitable for viewing the distance of your computer
Don’t take breaks while you are working

You may have an underlying problem with dry eye. This may make digital eye strain worse, or more likely to occur. Dry eye is more common in women than in men. It also becomes more common with age. Some medicines and health problems make dry eye more likely. For example, if you use antihistamines, you may be at greater risk of having dry eye. If you have thyroid disease or certain autoimmune diseases, you are also at greater risk of having dry eye.

What are the symptoms of digital eye strain?

Digital eye strain can cause many symptoms, including:

Blurred vision
Double vision
Dry eye
Eye discomfort
Eye fatigue
Eye itching
Eye redness
Eye tearing
Headaches
Neck and shoulder pain

Most of these symptoms are short-term (temporary). They often lessen or go away when you stop using your computer or device. But symptoms may continue for a longer time.

The severity of symptoms may vary depending on:

How long you have been using the computer or digital device
Your underlying eye problems
Other factors that cause digital eye strain.

Symptoms may get worse if you don’t resolve the problem.

Using a computer or digital device for a long time can also lead to other symptoms. This includes neck and shoulder pain. This is often due to poor alignment and posture when using the computer or digital device. Some healthcare providers call these symptoms part of digital eye strain as well.

How is digital eye strain diagnosed?

Your eye care provider will make a diagnosis with a health history and complete eye exam. They will assess if any health problems, medicines, or environmental factors might be adding to your symptoms.

Your eye care provider may test the sharpness of your vision and how well your eyes focus and work together. For a more detailed exam your provider may want to dilate (enlarge) your pupils. Then they will use a device (ophthalmoscope) to look at the back of your eye. In some cases, you may need to get follow-up blood tests for healthcare problems that might be helping to cause your digital eye strain.

How is digital eye strain treated?

Treatment includes creating a better work environment.

Rest your eyes at least 15 minutes after each 2 hours of computer or digital device use.
Every 20 minutes, look into the distance at least 20 feet away from the computer or digital device. Do this for at least 20 seconds.
Enlarge the text on your computer screen or digital device.
Reduce glare from the light sources in your environment.
Think about using a screen glare filter.
Place your screen so that the center of it is about 4 to 5 inches below eye level (about 15 to 20 degrees from the horizontal).
Place your screen about 20 to 28 inches from your eye.( About arm’s length.)
Remember to blink often.
Fix your chair height so your feet can rest comfortably on the floor. Don’t slump over the computer screen.

Making these changes may help eliminate digital eye strain in many people.

Your eye care provider will also need to treat any hidden health problems that may be adding to your digital eye strain. For instance, you might need a new pair of glasses. If you have an underlying dry eye problem, your eye care provider might advise the following:

Using lubricating drops
Treating allergies, if you have them
Creating a more humid work environment
Drinking more fluids (staying hydrated)
Taking a prescription medicine to increase tear production

What can I do to prevent digital eye strain?

Create a better work environment to help prevent digital eye strain. If you use glasses or corrective lenses, see your eye care provider at least once a year or as advised for a checkup. Also see your healthcare provider regularly. This can help prevent and treat health problems that can help cause digital eye strain.

Key points about digital eye strain

Digital eye strain is a group of related eye and vision problems caused by extended computer or digital device use.
Symptoms include eye discomfort and fatigue, dry eye, blurry vision, and headaches.
Uncorrected vision problems are a major cause.
Sometimes hidden health problems help to cause it.
Having a better computer work environment may help improve symptoms.
Resting your eyes regularly is one of the best ways to prevent and treat digital eye strain.

Next steps

Tips to help you get the most from a visit to your healthcare provider:

Know the reason for your visit and what you want to happen.
Before your visit, write down questions you want answered.
Bring someone with you to help you ask questions and remember what your healthcare provider tells you.
At the visit, write down the name of a new diagnosis, and any new medicines, treatments, or tests. Also write down any new instructions your healthcare provider gives you.
Know why a new medicine or treatment is prescribed, and how it will help you. Also know what the side effects are.
Ask if your condition can be treated in other ways.
Know why a test or procedure is recommended and what the results could mean.
Know what to expect if you do not take the medicine or have the test or procedure.
If you have a follow-up appointment, write down the date, time, and purpose for that visit.
Know how you can contact your healthcare provider if you have questions.

July 19, 2021

Prosthetic Contact Lenses

Prosthetic contact lenses are prescribed to mask flaws and improve the appearance of an eye disfigured from a birth defect, trauma, or eye disease.

If certain structures of the injured or disfigured eye also fail to function properly, special prosthetic lenses can be designed to block excess light from reaching the back of the eye to reduce glare and increase comfort.

Your eye care practitioner can match prosthetic contact lenses to the appearance of a healthy eye by using a pre-made trial set or by ordering custom-painted contact lenses.

Like regular contact lenses, prosthetic contacts can be made of gas permeable or soft lens materials. And most prosthetic lenses can be cleaned and disinfected using the same multipurpose contact lens solutions recommended for conventional soft or gas permeable lenses.

Custom prosthetic lenses can be made in a wide variety of lens powers to correct nearsightedness, farsightedness and/or astigmatism, or they can be produced without corrective power to simply provide a more natural appearance to a blind or disfigured eye.

Eye Conditions That May Benefit From Prosthetic Contact Lenses

Many injuries, conditions and infections can lead to disfigurement of an eye and make an individual feel self-conscious about his or her appearance. Prosthetic lenses can be specially designed to match the appearance of the unaffected eye as closely as possible and make the disfigured eye less conspicuous.

Disfiguring conditions frequently treated with prosthetic contact lenses include incomplete formation of the pupil (aniridia), lack of pigment or color in the eye (albinism) and damage to the cornea from trauma.

People with albinism or other eye conditions creating light sensitivity (photophobia) can benefit from prosthetic lenses that reduce the amount of light entering the eye. Prosthetic lenses also are sometimes used to eliminate double vision (diplopia) caused by certain eye conditions.

Special prosthetic colored contact lenses sometimes are used to improve vision in cases of childhood amblyopia. Two identical-appearing colored contacts are worn, but one lens has an opaque pupil painted on it to block (occlude) light from entering the eye. This lens is worn on the eye with normal sight, forcing greater use of the amblyopic eye to improve vision development in the affected eye.

Occlusion therapy with prosthetic contact lenses can be more effective for treating amblyopia than the use of an eye patch, which children often resist or remove due to embarrassment. But amblyopia treatment with contacts is more expensive due to the cost of the prosthetic lenses.

How Prosthetic Contact Lenses Are Prescribed

The first step in being fit with prosthetic contact lenses is to have a comprehensive eye exam. During this exam, your optometrist or ophthalmologist will thoroughly examine your eyes to rule out conditions that might interfere with successful prosthetic contact lens wear.

The second step is to undergo a contact lens fitting. In addition to performing the steps in a normal contact lens exam and fitting, your eye doctor may also take close-up photographs of your eyes. These color photos are sent to the prosthetic contact lens manufacturer to help the company create a prosthetic lens that matches your natural eye color and appearance as closely as possible.

Some eye doctors who specialize in contacts for hard-to-fit eyes also may have fitting sets of sample prosthetic lenses on hand so you can get an immediate idea of how effectively the lenses can restore a natural appearance to your affected eye(s).

January 20, 2021

Transposition of ophthalmic lenses

Transposition

by Andrew Othuke Akpeli

Introduction / definition

According to Efe (2012) transposition as the process of changing a lens prescription from one form to another equivalent form without changing the value i.e. it is also to rewrite the expression of its power without actually changing its value. It can also be define as the act of converting the prescription of an ophthalmic lens form a sphere with minus cylinder form to a sphere with plus cylinder form or vice vise. Example – 3D sphere – 2D cylinder axis 180 transpose to – 5D sphere + 2D cylinder axis 90 prescription consists of the sphere, cylinder and the axis. The sphere correct hyperopic and myopia, the cylinder corrects the amount of astigmatism and the axis shows where the stigmatism correction is located.

Types of transposition

Flat Transposition

Toric transposition

Flat transposition: This is the process of transposition whereby the cylinder power and spherical power is separated by 90. The flat transposition is use in the dispensing laboratory.

Toric transposition: This is the process of transposition whereby the cylinder power and spherical power is not separated by 90. The toric transposition is use in the production laboratory.

Lens prescription

Lens prescription can be written in any of this form

Plano cylinder
Sphero cylinder
Cross cylinder

Plano cylinder: This has one surface plane and the other, either + or – cylinder eg (plano x 0.50DCx180)

Sphere cylinder: This has one surface spherical and the other cylindrical eg +0.75DS -1.00DC x 50

Cross cylinder: This has one surface a cylinder and other another cylinder eg +1.50DCx180/0.75DCx90

Rules of transposition

Transposition of sphero-cylindrical prescription from plus to minus cylinder (or vice versa)

Rules

Step 1: New spherical power: add the power of the sphere to the power of cylinder (algebraically) of a given prescription

Step 2: New cylindrical power: change the sign of the cylinder (plus or minus to the opposite sign) with same power.

Step 3: New axis: add or subtract 90 from the given axis (depending on which value is higher) i.e. if is below 90, add 90 to it but if is above 90 subtract 90. Let us now apply this rule to a specific sphero – cylindrical prescription.

Given + 1.00DS – 1.00DC x 90

From the on set, it is important to note that this prescription has been written in minus cylinder from. To convert it to plus cylinder form, we apply the rules as follows.

Rule 1: (new spherical power); (+1.00) + (1.00) = plano

Rule 2: (new cylindrical power) change the cylinder sign with same value = +1.00DC

Rule 3: (new axis) add or subtract 90 (depending on which value is greater) i.e if is below 90, add 90 to it but if it is above 90 subtract 90. 90 + 90 = 180. Therefore, the transposed plus cylindrical form of a given prescription is plano + 1.00DC x 180

Given -2.00DS + 1.50DC x 45

To transpose this prescription from plus to its minus cylindrical form we apply same rules as follows:

Rule 1: (new sphere power) – 2.00 + 1.50 = – 0.50DS

Rule 2: (new cylinder power) change the cylinder sight with the same power -1.50DC

Rules 3: (New axis) i.e if is below 90, add 90 to it but if is above 90 subtract 90 45 + 90 = 135

Thus, the transpose form of this prescription into its minus cylindrical form is equivalent to :- 0.50DS – 135

Transposition of sphero-cylinders into cross cylinders

A sphero-Cylindrical prescription can be broken down into two cross-cylinder that it was originally made of this form of. This form of transposition is also guided by its set of rules

Rules

Rule 1. (1^st Cross-Cylinder): Take the spherical power of a given sphero-cylinder prescription and write this as a cross cylinder with its axis 90 away from the axis of a given sphero-cylindrical prescription.

Rule 2. (2^nd cross-cylinder) add the spherical and cylindrical power of a given sphero-cylindrical prescription and write this as cross cylinder with its axis same as the axis of the sphero-cylindrical prescription.

Rules 3. (both cross-cylinder) combine the two cross cylinder obtain from rule 1 and rule 2 above as the equivalent cross cylinder for the sphero-cylindrical prescription.

The follow are some examples to illustrate the application of the rules

Given -4.00DS – 0.50DC x 90

Rule 1. (1^st cross-cylinder) -4.00DC x 180

Rule 2. (2^nd cross-cylinder) -4.50DC x 90

Rule 3. (3^rd cross-cylinder) +4.00DC x 180/-4.50DC x 90

Given: -1.50DS + 0.75DC x 45

Rule 1. (1^st cross-cylinder) -1.00DC x 135

Rule 2. (2^nd cross-cylinder) -0.75DC x 45

Rule 3. (3^rd cross-cylinder) +1.50DC x 135/-075DC x 45

Transposition of 2 cross-cylinder into sphero cylinder

Rule 1: (sphere power) take either power of the 2 cross-cylinders as spherical power of the new sphero-cylinders as spherical power of the new sphero-cylinderical prescription.

Rule 2: (cylindrical power) subtract the power of the cylindrical chosen as sphere from the power of the second cross-cylinder and make this the cylinder of the new sphero-cylinder

Rule 3: (axis) take the axis of the cross-cylinder that was not chosen as sphere power as axis of the new sphero-cylinderical prescription

The following are some examples to illustrate application of the rule

Given: +2.00DS x 180/+1.00DC x 90

Rule 1. (sphere power) + 2.00DS

Rule 2. (cylindrical power) +1.00 – (+2.00) = -1.00DC

Rule 3. (axis): 90

Therefore, the sphero-cylindrical prescription is: +2.00DC – 1.00DC x 90

Given: -1.00DC x 135/-3.00DCx45

Rule 1. (sphere power) -3.00DS

Rule 2. (cylindrical power) -1.00 – (-3.00)

-1.00 + 3.00 = +2.00

Rule 3. (axis): 135

Therefore. The sphero-cylindrical prescription is: -3.00DC + 2.00DC x 135

Toric transposition

A toric lens is practical same as a cylindrical lens. By these design the surfaces of toric lenses are more curved (or bent) than the surfaces of cylindrical lenses. But unlike the flat cylindrical lens prescription, the toxic prescription will indicate the various curves that have been incorporated during the process of production to arrive at a particular prescription. This explain why a toric lens prescription have the following three parts

The base curve (BC)
The cross curve (CC)
The sphere curve (SC)

To produce a particular prescription from a lens blanks these three components with their different powers will be generated in the factory. This process is called surfacing

Since most of the physical properties of toric lenses are similar to cylindrical lens and vice versa. This means that given a specific toric lens prescription, the sphero-cylindrical prescription of equivalent power can be deduced from it by applying the following rules.Related Topic procreteconstruction 3 people Job Vacancy in Australia

Rule 1 (sphere power) = base curve + sphere curve

Rule 2 (cylinder power) = cross curve – base curve

Rule 3 (axis) same as axis of cross curve

The following example is meant to illustrate the application of those rules:

Rule 1 (sphere power): +2.00 + (-3.00) = -1.00DS

Rule 2 (cylinder power) +4.00 – 2.00 = +2.00DC

Rules 3 (axis) = 180

Sphero-cylindrical prescription: -1.00DS + 2.00DC x 180

Importance of transposition

After an optometrist has done a refraction for a patient, the optometrist takes the prescription to the optician and the lens prescription is given to be + 1.00DS-2.00DC x 180 and the optician check the stocks of lens available and founds that (+1.00DS – 2.00DC x 180) prescription is not in stock, what the optician need to do is to transpose the prescription.

+1.00DS – 2.00DC x 180

– 1.00DS + 2.00DC x 90.

So instead of the optician finding it as a problem of getting + 1.00DS-2.00DC x 180 the optician simply go for -1.00DS + 2.00DC x90 it makes dispensing cylindrical lenses easy instead of keeping your patient waiting or ordering for more lenses when unknowing to you it is your stock.

Conclusion

In conclusion, transposition is important because it helps and optician to get an equivalent (same) prescription for a given prescription. It is also important for an optician to be acquitted with the knowledge of transposition. An optician should not be ignorant of keeping a patient waiting or placing an order for a cylindrical lens prescription when there is an alternative form of that prescription in stock, all you need to do is to transpose.

References

Efe Odjimogho, O.D. FNCO (2012). In laboratory manual, senior lecturer optometry department faulty of life science, university of Benin.

Mr. Nsubuisi Igboekwe (2013). Ophthalmic workshop dispensing lab ii

San Francisco, American Academy of ophthalmology 2011-2012

Allied Health on the job training kit 2011

Dallas American Health Association Academy of ophthalmology 2011 (Revised as appropriate)Facebook Twitter Email WhatsApp Pinterest

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Tag: ophthalmic