THE OTAGO DENTAL LOOKOVER
Information for Eyecare Specialists:
The Otago Lookover is a multi focal occupational lens which is ideal for dentists who do not need a distance correction within the surgery. It gives a near point as close as 30 cm with a very wide field at 70 cm for instrument tray, X-ray viewer and patient observation. These are connected by a progressive zone large enough to be used for all dental purposes.
In reality the Otago Lookover is a 'cut down' progressive bifocal in which the regular distance portion of a progressive lens is surfaced to the power required for the instrument tray, about 70 cm. The progressive addition changes this power to the power required to give a near point of 33 cm or less. The addition power will be half, or slightly less than half, the total addition. A soft style progressive lens is used to maximise progression width and give easy adaptation.
A lookover frame with a lens depth of at least 28 mm is required to provide adequate near area and eye protection. The fitting cross is placed 4 or 5 mm below the top of the lens and at the true distance interpupillary distance.
For example:
Refraction R +0.50 L +0.75/-0.50 +180 Add +2.75 gives a near point of 30 cms. Distance p.d. 64mm
Prescribe Distance correction plus +1.50D, and remainder of add in progression (+1.25D)
Order R +2.00 L +2.25/-0.50 x 180 Add +1.25 SOLA XL. Fit cross 4mm below
lens top. Fit cross p.d. 64 mm
In this example , a SOLA XL lens has been chosen but any similar soft lens such as a Rodenstock Progressive "R" or Hoyalux Soft can be used.
Information for dentists:
It is essential that you discuss your requirements with your eye-care specialist/spectacle maker. All eyeglasses are compromises and none will restore the flexibility of youth. These glasses are lookovers; a clear view of distant objects (i.e. beyond a meter or so), which is not usually vital in the dental surgery, is gained by looking over the top of the lenses. The focal point of an Otago Lookover is usually set at 30 cm or 33 cm, well inside that used for reading glasses. This will allow clear vision for inspection to about 28 cm. The top part of the lens is designed so that objects up to about 90 cm away are in focus. In the middle section of the lens the focus changes gradually to allow a normal operating focal length of about 35-40 cm.
We are continuing with this study at the School of Dentistry, University of Otago. The comments of fitters and dentists using these lenses would be greatly appreciated.
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