Copyright notice Abstract AIM—To introduce the "starlight" test which was devised to check binocular vision in normal conditions of seeing in a rapid, easy, and cost effective manner and to estimate the possibility of its clinical use in screening the binocular visual field of patients. Unlike the original Bagolini test, the starlight test uses three light sources in horizontal or vertical lines according to the testing purposes and the subject is asked to fixate upon the centre light. Through Bagolini glasses, the subject observes the resulting grid-like pattern and the state of binocular visual field of the subject can be roughly estimated. RESULTS—Normal subjects and patients with strabismus, visual field loss from intracranial diseases, glaucoma, retinitis pigmentosa, and functional visual loss were examined using the starlight test and findings from each case were discussed. It provides information about the state of binocular vision of patients in normal conditions of seeing.
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Eyes can be deviated inward esotropia , outward exotropia , upward hypertropia , downward hypotropia , intorted incyclotorsion , or extorted excylcotorsion. The examiner is looking at the corneal light reflex. If the light reflex is centered in both eyes, the patient does not have a manifest misalignment. If the light reflex is displaced, it shows a manifest misalignment.
For example, the light reflex at the pupillary margin is about 2mm from the center with a normal 4 mm pupil. If the light reflex is displaced nasally, the patient has an exotropia.
If the light reflex is displaced temporally, the patient is esotropic. It is important to note reflex is always slightly nasal, even in an orthophoric patient. It is also important to note that angle kappa can affect light reflex measurements. A positive angle kappa simulates an exotropia, a negative angle kappa simulates an esotropia.
A base-in BI prism is used to neutralize an exotropia, a base-out BO prism is used to neutralize an esotropia. Base-up BU is used to neutralize a hypertropia. Base-down BD is used to neutralize a hypotropia. Modified Krimsky — Prism over fixating eye. A cover-uncover test picks up small manifest deviations that are always present. A cover test verifies whether or not eyes are straight. The deviated eye only picks up fixation when the preferred eye is covered.
The non-preferred eye when covered and uncovered should not move. When a patient has an alternating tropia, either eye will move to re-fixate when the fellow eye is covered with an occluder.
When a patient is orthophoric, neither eye will move because each eye is fixating. A cover-uncover test is done before moving on to alternate cover testing. Prisms are used to neutralize these deviations. It is possible to have "ortho" eyes with cover-uncover and movement of eyes on alternate cover, these are called phorias. On both of these testing methods, it is important to occlude each eye long enough so the patient has time to take up fixation as the occluder is shifted back and forth.
This is especially true if one eye is amblyopic. An accurate way to measure strabismus correctly is to measure to reversal.
Figure 1. Titmus test on right polarized glasses above , Randot test on left. Titmus or Randot Introduction These tests are used the most often to quantify stereopsis, it can also be used to detect ARC abnormal retinal correspondence.
The level of dissociation is moderate. This test should be done on all patients who are bi-foveal and can be used as a quick screening to see if the patient is using two eyes together. One could also use this test to see if the patient is malingering. They are then shown a book with stereoscopic images 3-dimensional and 2-dimensional images.
The patient is asked to identify which pictures are stereoscopic. The book either has a titmus fly or a randot stereogram. The other side of the book has stereoscopic animals and circles. It is typical to ask the patient to identify the animals after the fly or shapes and the circles last. Some could argue that the titmus fly gives off monocular clues that allow patients with reduced stereo to able to identify the image.
One way to verify if the patient truly has stereopsis is to flip the book at a 90 degree angle, the image should appear 2-dimensional.
Falsely good stereopsis is very common when using the titmus fly because it is the most commonly used stereopscopic test. The level of dissociation is mild.
It can be used with patients who have decreased stereopsis but are orthophoric on cover testing. This test can also be used on patients with small to intermediate angle deviations, and with patients with Monofixation Syndrome.
A 4-BO prism is quickly placed over the right eye and the examiner observes the movement of the left eye. A sudden displacement of the image onto the parafovea will cause re-fixation if the image is falling on corresponding points on a normal retina. The test is repeated on the left eye and the examiner observes the movement of the right eye.
Interpretations When the test is negative, the patient is considered to be bifoveal. When the prism is over the right eye, the left eye moves out and in. When the prism is over the left eye the right eye goes out and in. There are two responses when there is a scotoma microtropia. There is a scotoma on the right eye if the prism is over the right eye and there is no response bilaterally, vice versa for the fellow eye.
Bagolini striated Lenses Bagolini Glasses Introduction Bagolini glasses do not have dioptric power but have narrow striations running parallel in one meridian.
This test is used to determine the direction of a pseudofovea, abnormal retinal correspondence ARC , and suppression. This test also is able to tell the examiner if the patient has periphery-sensory fusion. This test is mildly dissociating so it will detect small ARC even in large angle strabismus. The Bagolini glasses also simulate life-like testing conditions, which makes it the least dissociating. A disadvantage to this test is that it is difficult for young children to appreciate because it requires reliable subjective responses.
Patient is asked to look at muscle light or pen light. Interpretation When a patient sees only one line at a time, the patient is suppressing. You may offset the deviation with a prism and if the patient reports an X this confirms NRC. Double Maddox Rod Introduction This test is used to determine the presence of a cyclo deviation. This test is very dissociating.
Clinically, it is useful to use this on patients who have a suspected 4th Nerve Palsy, or Thyroid Eye Disease. For a 4th Nerve Palsy, it could be helpful to put the red rod on the eye that is paretic.
Interpretation If the line is completely parallel, there are 0 degrees of cyclotorsion. The patient should be able use the knob to rotate the line until it is parallel line. If the rod has to be rotated inward, the patient has incyclotorsion. If the rod has to be rotated outward, the patient has excyclotorsion.
The trial frame has an axis marked, so the examiner can determine the amount of torsion. Figure 5. Worth 4 Dot and the red-green filtered glasses. The level of dissociation is high. This test can be used for any verbal child with any angle of strabismus especially with reduced stereopsis.
With the lights off, the depth of suppression can be measured. Place the red-green glasses on the patient, with the red glass on the right eye. Note: With the right eye patient should see two red lights and with the left eye, patient should see three green lights. The examiner can also measure the boundary of suppression by testing the patient at the end of the room and walking closer to the patient.
Fusion is only possible when the patient is bifoveal, which implies normal retinal correspondence. Suppression at near and distance: Patient sees 3 or 2 lights. Suppressing the right eye means the patient is not seeing the lights with the red glass; therefore they will report seeing 3 green lights. Suppressing the left eye means the patient is not seeing the lights with the green glass; therefore they will report seeing 2 red lights.
Fusion at near, but suppression at distance: this is the classic response for Monofixation Syndrome, but this can also happen with patients who have a large deviation. Diplopia: Patient reports 5 lights. It is important to ask if the red and green lights are there at the same time. Patients can rapidly alternate suppression which can give a false diplopic response.
If a deviation is off set by a prism, and the patient still reports diplopia, this would indicate ARC. It can also be used to detect suppression, determine retinal correspondence, and to confirm the type of diplopia a patient has crossed or uncrossed. This is a moderately disassociating test. Clinically, it is most useful to use this test on adults who complain of diplopia who seem orthophoric on cover testing. It is also a good way to fit adults with prisms. Testing children with the red filter can be difficult.
The examiner directs the patient to fixate on the white circle. The patient will give answers of suppression, fusion, or diplopia. This is why it is important that the patient is able to distinguish the red circle as seen through the filter only as opposed to a red circle on top of a white circle when they are fused.
Patients who have alternating suppression should see the red and white light alternating. If the patient sees one red circle and one white circle simultaneously, they are diplopic. The location of the red circle in relation to the white circle will tell the examiner the type of strabismus or diplopia the patient has. For example, the exotropia patient has the red filter on the right eye and reports the red circle is to their left, this denotes crossed diplopia. An esotropic patient will report the red circle to their right, which is uncrossed diplopia.
A possible microtropia response Possible manifest strabismus responses When interpreting results, the line associated with each eye is the line perpendicular to the lens in front of that eye. If the lens in front of the right eye is at degrees, then the line on the results representing the right eye will be at 45 degrees. One light: If the patient sees one light, that means that either they have fused the two images from each eye together, or are suppressing of one of the images. Two lights: If the patient sees two lights, this is indicative of diplopia as the patient has an image from each eye but is unable to fuse the two. One line: If only one line is seen, this means one eye is suppressing. The eye that is suppressing is the eye which the corresponding line is not seen.