KEEP UP YOUR HEAD !   --Wrong glasses may endanger this.

DIRECTION OF VISION, DIRECTION OF EYES, POSITION OF HEAD AND INFLUENCE OF VISUAL AIDS    Herluf Skovsgaard, dentist, consultant in ergonomics.

In all examples the direction of vision is 45 degrees downwards. This inclination of direction of vision may be accomplished by most persons only by inclining the eyes.

When the direction of vision is even more vertical (often the case) you first incline your eyes as much as comfortable and then add inclination of head (about 15 degrees) and then finally add bending the cervical part of columna.

Bad

This dentist (or assistant) is not inclinating the eyes downwards, so he has to bend head and neck very much, especially when looking steeper down than 45 Degrees.

Unfortunately the head alone can only be inclinated a little downwards. All

further inclination is made in the cervical spine, and if done much and often the intervertebral discs may degenerate.

Good

The eyes are inclinated 45 degrees downwards, and therefore the head

does not need to be bend down in order to look 45 degrees downwards. If it is necessary to look more steep downwards than 45 degrees, the head and neck must also be bend.  

The inclination of eyes should be no more than it feel comfortable.

Bad

Glasses must allow the dentist to look downwards. This is not possibly because the lower margin of the glasses is placed much too high. The glasses causes a bad or very bad sitting position.

Good

Lower margin of glasses are places in contact or very close to the chin and choose a frame for the glasses allowing this. Than the dentist is able to look downwards in order to keep up the head.  Glasses with this design are very important for allowing the dentist to work in fine workingpositions.

The optical center should be placed 30 to 35 degrees below horizontal.

Bad

If the power of the glasses is more than about 1,5 dioptries,  one should not position the glasses so it is necessary to look inclined through the margin of the glasses. This will result in a distorsion  of the visual field (chromatic and speric abberation). An anisotropic correction (correction of eye linse "errors") will make the result even more bad.

Looking inclined through stronger glasses will too result in a distorsion of the visual field (spheric and chromatic aberration)

Good

If the power of the glasses is more than 1,5 dioptries, and if there is made astigmatic corrections (eye-lens error corrections) it is essential that the direction of vision for dentists precisionwork is close to the optic centeraxis, perpendicular to the lens.

The optic center is placed about 35 degrees below horisontal plane, and the glasses are inclined 35 degrees.

Choose a framework of ex titanium thread so ear supports can bent to achieve this.

GLASSES WITH PROGRESSIVE POWER.

These glasses have the optical force increasing when the eyes are inclined downwards.

The force of the lenses of the glasses is deciding the minimal distance of wiew.

This means (a short explanation) that if the dentist is inclining the eyes 45 degrees downwards the head should be /could be closer to the object (the tooth)  than when inclining the eyes less downwards.

The direction of vision is deciding the head position, which is very uncomfortable, and stressing for the neck-muscles.

The choise, when more than one lens power is necessary due to decreased flexibility of the eye lens, is therefore absolutely GLASSES WITH TWO POWERs.  (Bifocal glasses) The visual field downwards, marked with blue is very large and covers half of the glasses. The optical center of the lower part is marked.

If your glasses are very strong more than say 3 dioptries with konvex (+) or espically negative (-) force., a skilfull optician can make this solution for you, cutting two glasses and glue them together.  

This enables you to be able to keep up your head also when using strong glasses. Choose a frame only supporting upper part of the glasses.Please look at illustrations. The optical center of the lower part of the glasses are marked.

For all glasses average working distance is about 33 cm + / - about 8 cm. Tell that to your optician.

Bad

Use of loupe may as wrong constructed glasses be a major reason for serious troubles with headposition causing muscular tensions, headace, and longterm destruction of shape and vitality of spine and intervertebral discs.

Also using loupe you should KEEP UP your head.

Loupes placed horizontal according to head (Frankfurter horizontal plane) should never be used.

Good

Loupes are inclined 45 degrees so dentist can keep up his head when working.

This is possible for some loupes supported by head band, among others Zeiss with head band support.

Loupes  placed into the glasses  (and glued there) are mostly inappropriate, becauses they cannot be inclined enough,  except for if the glasses supporting them is inclined at least 20 to 25 degrees downwards.

Choose loupes with working distance, and enlargement 2,5.

I do only know two types of loupes mounted on frames of glasses so they can be inclined downwards.  Merident from Finnland,   www.merident.com and

Surgitel from USA   www.surgitel.com  . Go on internet and find who is selling them in your country.