6. Evaluation of a case of strabismus - Part 2

SENSORY TEST. 1. [image] Orbit Eye Center for Pediatrics & Oculoplasty.

1. Worth Four Lights. This is a dissociation test which can be used with both distance & near fixation to differentiate b/w BSV, ARC & suppression. Results can only be interpreted if the presence or absence of a manifest squint is known at time of testing..

Worth Four Lights. Apparatus: It consist of four circular lights two green one red and one white which are viewed through complementary red and green goggles. The red light is seen through the red filter and the green lights through the green filter, the white light is common to both eyes..

Worth Four Lights. Procedure: • A patient wears a red green goggles with the red lens in front of the right eye, which filters out all colors except red ,and a green lens in front of the left eye, which filter out all colors except green . • The patient then views a box with four lights , one red, two green and one white..

Worth Four Lights. Results If BSV is present all four lights are seen If all four lights are seen in the presence of a manifest strabismus, ARC If two red lights are seen, left suppression is present If three green lights are seen, right suppression is present 5 dots, 2 Red in the left eye, 3 Green in the right eye, Uncrossed Diplopia. 5 dots, 3 Green dots in the left eye, 2 Red dots in the right eye-Crossed Diplopia, If the red and green lights are seen alternatively, alternating suppression is present.

Bagolini Striated Glasses. This is the test for detecting BSV, ARC Or suppression. The test can be used at 6m, 33cm.

Bagolini Striated Glasses. 7. The apparatus consists of a pair of Plano glasses, marked with fine parallel striations at 45° on one glass & 135° on the other. When a spotlight is viewed through the glasses each produces a line image at 90°to the axis of the striation.

Bagolini Striated Glasses. Procedure : The two lenses are placed at 45°& 135°in front of each eye & patient fixates a small light source Each eye perceives an oblique line of light , perpendicular to that perceived by the fellow eye Dissimilar images are thus presented to each eye under binocular viewing conditions..

Bagolini Striated Glasses. Results: • If the two streaks intersects at their centers in the form of an oblique cross the patient has straight eyes with BSV or squint with ARC • If the lines do not cross in center, the patient has squint with NRC and diplopia • If only one streak is seen there is no simultaneous perception and suppression is present •If a small gap is seen in one of the streaks, a central suppression scotoma (as found in microtropia) is present.

Purpose To confirm or rule out the presence of a small central scotoma..

A small central suppression zone should be suspected in a patient with 1. A slight reduction in visual acuity (20/25 to 20/40) in one eye 2. Mildly reduced stereopsis (30 to 80 seconds of arc). 3. Monofixation syndrome secondary to a small angle strabismus. 4. Macular diseases affecting the foveal area will create a similar clinical presentation..

> Loose 4Δprism. > A distance visual acuity chart that can isolate letters..

13. Mechanism of 4Δ BASE OUT TEST. Place 4Δ in front of one eye and observe the presence of a biphasic corrective movement of the other eye..

14. [image]. [image]. inward rotation of Right eye to re-fixate on fovea,.

15. 115). Result: - No foveal suppression in both the eyes.

16. Case 2. Place 4Δ in front of one eye and observe the presence of a biphasic corrective movement of the other eye.

17. No movement of left eye indicating presence of foveal suppression in right eye.

TITMUS FLY TEST /RANDOM DOTSTEREBUTTERFLY. It is based on the principle of linear polarization. Polaroid filters are worn, and a vertical image of a light source is seen through one filter and a horizontal image of light is seen through the other filter. The target are presented as vectographs The disparity produced by either eye results in stereopsis.

TITMUS FLY TEST /RANDOM DOTSTEREO BUTTERFLY. One plate contains the image of a fly The second plate consists of nine boxes each containing four circles and three rows of animals One circle is displaced to produce disparity The image of one animal in each row also appears to stand out.

A black and white sign with white text Description automatically generated.

After-image test. When using the afterimage test, a vertical bright light is directed at the left fovea and a horizontal bright light at the right fovea for 15 seconds each. The patient is then asked to draw the position of the afterimages. Perception of the afterimages is easiest when the patient closes their eyes or looks at a blank screen..

22. Lea eF NRC NRC eye ate Patert•s. The results are interpreted as follows: Normal Retinal Correspondence: The patient will draw a cross (Fig.B). Right Esotropic Patient with Anomalous Retinal Correspondence (ARC): The patient will draw the vertical image to the left of the horizontal image (Fig.C). Right Exotropic Patient with ARC: The patient will draw the vertical image to the right of the horizontal image (Fig.D). ARC and Eccentric Fixation: In exotropia: The images will be in a crossed position (Fig.E). In esotropia: The images will be in an uncrossed position (Fig.F). Suppression: Left suppression: The patient may only draw the vertical image. Right suppression: The patient may only draw the horizontal image. Alternate suppression: The patient sees vertical and horizontal lines alternately..

23. Disadvantages: The afterimage test is the most un physiologic of all the tests for ARC, as afterimages and normal visual stimulation are so different that they cannot be easily compared. Small children often do not understand what they are supposed to observe..

28. Reference. Leela Ahuja - Manual of Squint (2008) Pradeep Sharma MD FAMS / Sherwin Isenberg - Strabismus Simplified - 2nd Edition (2016) Sameera Irfan - Understanding Strabismus ( 2014) A.K. Khurana - Theory and Practice of Squint and Orthoptics 3rd Edition (2018) Dr. Subhash Dadeya /Dr. Savleen Kaur - Basic Examination of Strabismus.