The IRISO System
Front or side light?
Bernard Jensen created the first iriscope ensuring that its illumination would not create reflections within the iris area. To achieve this he chose a frontal light that would be reflected inside the pupil. This ingenious system continues to be applied as a standard in many modern iriscopes, although it presents serious problems:
- being frontal the light falls on the most sensitive part of the retina called fovea, causing discomfort or even pain
- the amount of light that can be applied frontally is limited for the reason previously explained, and although it may still work when photographing clear eyes, it will be insufficient for dark eyes that require a greater amount of light, resulting in a lack of sharpness. Considering a clear-eyed American clientele, this may have been a minor inconvenience for Bernard Jensen, not so in modern racial plurality.
What is the fovea?
The fovea is the small part of the retina that corresponds to the central point of our vision. As can be seen in the upper graphs, the fovea is populated by a huge amount of photoreceptors called cones, very sensitive to light and color, which due to their quantity capture images of great clarity and color shades. It so sensitive that staring at an intense light will be uncomfortable and even hurt, like looking straight at the sun, an eclipse or a welder working.
Surrounding is another intense region in photoreceptors called rods, much less sensitive and that only distinguish changes in light intensity, as if it were black and white, mixed with small amounts of cones that capture minimal information about colors. The number of rods gradually decreases towards the edge, until being so few that only very vague movements or forms are distinguished. This region corresponds to the peripheral vision, so insensitive that seeing the sun sideways does not bother.
In IRISO we use side lighting with LEDs intense enough to capture sharp images of dark irises without causing any discomfort to the patient.
The IRISO System
Using side instead of front lights brings the following advantages:
- no inconvenience for the patient, the session can be prolonged without disturbing
- a high power illumination can be used for dark irides and low power for clear ones
- the lateral light generates shadows that give an appreciation of the reliefs, important in the reading of many signs linked to the conformation of the fibers and not perceived with frontal illumination
- four different lights can be selected around the eye, changing the shadows and generating a dynamic reading similar to the exploration by turning the lamp around the eye
- changing lights means reflections are moved around, allowing all the areas of the iris to be seen
As a result is the IRISO System, a unique combination of four lights that can be selected individually or in opposite pairs operating a single rotating or sliding switch. Resulting lights is as follows:
- horizontal pair, its homogenous illumination is preferred for a general diagnosis
- the vertical pair facilitates the evaluation of the sclera and discovers the hidden places under reflections from the horizontal pair
- single texture light at 12:00
- single texture light at 3:00
- single texture light at 6:00
- single texture light at 9:00
These changing four lights (two in the case of Iricell) move the projected shadows and highlights, enhancing the perception of surface variations in fibers. Some important signals can be apparent under one illumination and hidden by another, making the changes of light indispensable. They also help to evaluate crypts and lagoons since light alternately crosses or penetrates to the bottom of them. Also in case of milky clouds due to circulatory problems, the illumination will penetrate below at a certain angle while causing dazzling reflections at another. The sum of the variations is the secret of the richly detailed evaluation of an IRISO iriscope.
IRISO products and their respective lighting system:
- Xpert: IRISO System with four lateral lights
- Iricell: IRISO System with two lateral lights
- Miniris: one frontal light
In conclusion, the frontal illumination certainly allows to elaborate the file with a single image, but at the cost of wasting a great amount of information and causing serious discomfort to the patient with the intense front light. Dark irides usually do not photograph well under that light. IRISO's lateral illumination System generates a variety of images that make up a dynamic exploration, loaded with a larger amount of information than a flat front light would show.
Following is a complete series of the six variations on a same eye taken with a professional Xpert iriscope, plus some interesting details of other iris. Your comments and observations on this subject are welcome, write us at firstname.lastname@example.org