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New handheld fixation device

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					                                           New handheld fixation device

                                       Anna Soproni, MD. Budapest, Hungary

Purpose: Presentation of a new handheld fixation device
Method: In the direct method of the fundus examination of the patients with bad compliance I urge the eye for
fixation by an optically placed at infinity red flashing ledlamp that I put directly in front of the fellow eye
Key words: fixation device, fundus examination


The good cooperation between the examiner and the patient is essential in most medical examination procedures.
In many cases difficulties in cooperation can be overcome with the help of a good resource. In this way further
intervention (e.g. general anaesthesia) in order to set up a more precise diagnosis can be avoided, that might be
expensive or means a certain risk for the patient or claims more staff. This is even more so in the case of
children. Numerous ophthalmological examinations necessitate that the examined person should be able to fixate
to a given point permanently. In the fundus examination quite often it brings also a problem up: the unability of
the sustained concentration of the patients. For example in the direct ophthalmoscopy people with bad
compliance the concern is, that the object showed by the examiner to the patient aimed to grip the interest for
getting a fixed eye position or to aim for the following of the eye to a given gaze position, is covered by the
examiner’s head.

Methods
For the distance cover test the patient needs to fixate ordinarily a continuous light source or movable object, for
the near cover test he or she needs to fixate a small picture, a point of a pencil or optotyp 1,2. There are more
complicated equipments that work with electrical amenable, movable figures, light emissing or that give sound.
Sometimes the examiner uses slide projector1.
Lang1 made a suggestion for a special fixation device for the distance cover test to complete to the former ones
that worked on continuous light. He achieved more effective concentration of the attention by a music box
maintained with changing color flashing light.

The new device
The device designed by myself in most of all cases can eliminate „the lap” mentioned in the introduction.
          The new device is a led-lamp (Figure 1) which works with an inner power source (accumulator) giving
a flashing, red light („Bunny Eye”) with low intensity, that with the help of its little size we may it place directly
in front of the either eye (Figure 2). Thus the attention of examined person can be aroused and drawn to a certain
point, so the other eye can be examined making good use of the synkinesis of the two eyes.

          This fixation lamp is a pencil-like roll a little longer and thicker (lenght 215mm, diameter17mm). The
light comes from an aperture in the upper third of the device (Figure1). The ligth source gives the picture as it
would be projected from a distance, as the divergent rays optically are made parallel. With this help the so-colled
„instrument convergence” or „proximal convergence” 3 may be decreased significantly. The intensity of the light
is reduced so much, that for its effect no afterimage is created, but the „pulse” of the led-lamp provides sufficient
preference over the continuous and sharp light of the ophthalmoscope used for examination of the other eye. So
the eye will pay attention to the slight flashing light rather than the sharp still one. The physiological basis of this
common experience is that the threshold of the stimulus of the eye arised by the effect of the continuous light
presenting a monotone stimulus, thus the sight will dislike that. So it is easier to pay attention to a flashing light
rather than a continuous one’s.
          The end of the device getting closer to the eye is rounded, thus the device itself can be held by the child
examined without any risk of damage or harm. Giving the device in the hand of the children we encourage them
to participate in the examination. But of course the lamp can also be held by the doctor, assistant or the joint
person of the child. (For in-patents we can carry the direct ophthalmoscopy out so that the device may lean on
the edge of the orbita, and thus we urge the patient to fixate.) The device can be hung in the examined patient’s
neck with the help of a ribbon thus avoiding dropping it.

Discussion
         Recently world-wide scale the indirect binocular ophthalmoscopy increasingly gains ground for the
fundus examination. However in spite of the doubtless advantage (wider field of view) of the indirect method
because of the disadvantages (too high intensity of the illumination, inverted virtual image of the retina, claim of
the additional plus lens, smaller magnification, more expensive price) the indirect ophthalmoscopy probably will
not displace the direct method from the everyday practice for a long time.
Conclusion
         As for the resolution of the mentioned in the introductory problem (the fixation target is covered by the
examiner’s head) of the direct ophthalmoscopy I did not find any data in the literature, I’d like to recommend
this new device designed by myself and used with success more than one year for all who principally deals with
the children or with the patients with bad compliance, or with in-patients, for those colleagues who deal with
fundus examination or deal with the examination of eyemovement. The lamp worked on slight intensity allows
too of an approximate assessment for the visual acuity of a child who can not speak. It may be useful for the
representatives of the associate professions as for the optometrists or for paediatricians.

1.   Figure. The handheld fixation lamp




2.   Figure. A child helds the device in his hand in front of his right eye. The red ligth of the LED-lamp at the
     moment of the flash glints on the cornea. During that time the doctor examines the left eye of the patient.




References

1.   Lang J.: Fixationseinrichtungen für den Abdecktest. Klin. Mbl. Augenheilk 1975; 167: 308-311.
2.   Noorden G.K. von, Helveston E.M.: Strabismus: A Decision Making Approach. I st ed., Mosby Co. St.
     Louis, 1994; p.1.
3.   Noorden G. K. von, Campos E. C.: Binocular Vision and Ocular Motility. Theory and Management of
     Strabismus. VI th ed. Mosby Co. London, 2001; p. 98.


Mail address:
Soproni, Anna M.D.
1142. Budapest, Sarkoz u. 7/c, Hungary
e-mail: sopronia@t-online.hu

				
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posted:3/24/2012
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