Pseudo-Gaze Deviation Resulting From Positive Angle Kappa and Esotropia

Photo and Video Essay Section Editors: Melissa W. Ko, MD Dean M. Cestari, MD Peter Quiros, MD Pseudo-Gaze Deviation Resulting From Positive Angle Kappa and Esotropia Maxence Rateaux, MSc, Marie-Andrée Espinasse-Berrod, MD, Chloé Couret, MD, Dominique Bremond-Gignac, MD, PhD, Matthieu P. Robert, MD, PhD FIG. 1. A. Binocular photography (fixation with the right eye; left eye in 23° esotropia). B. Monocular fixation of the right eye (angle Kappa = 17.6°). C. Monocular fixation of the left eye (angle Kappa = 18.1°). Abstract: A 6-year-old boy was referred for constant right gaze deviation. Rather than a gaze deviation, he constantly seemed to look on the left side of any displayed target. Examination revealed the association of a highly positive angle Kappa and an esotropia of equal values. He also exhibited signs of ocular albinism with no associated infantile nystagmus syndrome. The X-linked ocular albinism was confirmed genetically, explaining the presence of a positive angle Kappa. A highly positive angle Kappa can be associated with a convergent strabismus; in case both values offset each other, this can result in a constant “sidelooking,” which should not be confused with a gaze deviation. Ophthalmology Department (MR, M-AE-B, DB-G, MPR), Necker– Enfants Malades University Hospital, Paris, France; Borelli Centre (MR, MPR), UMR 9010 CNRS—SSA—ENS Paris Saclay, Université de Paris, Paris, France; and Ophthalmology Department (CC), HôtelDieu University, Nantes, France. The authors report no conflicts of interest. Journal of Neuro-Ophthalmology 2021;41:e234–236 doi: 10.1097/WNO.0000000000001068 © 2020 by North American Neuro-Ophthalmology Society Address correspondence to Maxence Rateaux, MSc, Ophthalmology Department, Necker–Enfants Malades University Hospital, 149 rue de Sèvres, 75015 Paris, France; E-mail: [e-mail] e234 A 6-year-old boy was referred for constant right gaze deviation. While fixating a straight target with both eyes open (primary position of gaze), he actually seemed Rateaux et al: J Neuro-Ophthalmol 2021; 41: e234-e236 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. Photo and Video Essay to look away, on the right side of the target. On right monocular fixation, the position of the right eye was unchanged, whereas on left monocular fixation, he seemed to look on the left side of the target (Fig. 1). Such a monocular fixation is typical of a bilateral highly positive angle Kappa. A unilateral cover test showed a 17° esotropia in far vision and 23° esotropia in near vision, with a fixating right eye. Angle Kappa was quantified semiautomatically by using a digital pictures method (Software Optiview; Seelab, Nantes, France) (1). This angle was 17.6° in the right eye and 18.1° in the left eye (normal range = 3–6°). Specific signs of infantile esotropia were also present, including dissociated vertical deviation, fusion maldevelopment nystagmus syndrome, and optokinetic nystagmus asymmetry. The best-corrected visual acuity was +0.3 logarithm of minimum angle of resolution in the right and left eyes and refraction was +6.50 (21.50 5°)/+5.50 (21.00 160°). Ophthalmological examination revealed a peripheral hypopigmentation (2) of the fundus (Fig. 2A), a grade IV foveal hypoplasia (3) on spectral domain optical coherence tomography (Fig. 2B), and an iris transillumination Sjödell (4) grade III (Fig. 2C). Dermatological examination was unremarkable. The child’s mother’s fundus exhibited typical hypopigmentation in splotches and streaks (Fig. 2D), strengthening the hypothesis of an X-linked ocular albinism. Molecular testing confirmed the diagnosis of ocular albinism type 1, by identifying a pathogenic mutation in the GPR143 gene in the patient, inherited from his mother. In this situation, no surgical solution was considered satisfactory; considering the context of infantile esotropia and lack of normal retinal correspondence, the best surgical outcome would be a microtropia, which here would look like an exotropia of the right fixating eye, with no certainty to get any significant functional benefit. The angle Kappa is the angle formed by the pupillary axis (center of the pupil) and the visual axis (line between the fovea and the fixation point). In the healthy population, this angle ranges between +1.91° ± 0.14° and +5.73° ± 0.10° (5). Highly positive angle Kappa can be the main expression of an ocular albinism; in albinism, positive angle Kappa results from the increased chiasmatic decussation, causing a temporal displacement of the hypoplastic fovea (6). A highly positive angle Kappa associated with a convergent strabismus, if both values offset each other, can therefore result in a constant “sidelooking,” which should not be confused with a gaze deviation (Fig. 3). FIG. 2. A. Fundus hypopigmentation (high-angle retinophotography). B. Thomas grade IV foveal hypoplasia (optical coherence tomography). C. Sjödell grade III iris transillumination (split-lamp photography). D. Splotches and streaks hypopigmentation of the child’s mother’s fundus. Rateaux et al: J Neuro-Ophthalmol 2021; 41: e234-e236 STATEMENT OF AUTHORSHIP Category 1: a. Conception and design: M. Rateaux and M. Robert; b. Acquisition of data: M. Rateaux, M.-A. Espinasse-Berrod, and M. Robert; c. Analysis and interpretation of data: M. Rateaux, e235 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. Photo and Video Essay FIG. 3. Schematic representation of positive angle Kappa and esotropia. A. Normal orthophoric subject: both visual axes converge to the fixation target; the physiological angle Kappa is slightly positive. B. Patient with a highly positive, bilateral 17° angle Kappa and no strabismus. The patient seems to exhibit a divergent strabismus while he is orthophoric. C. Patient with a highly positive, bilateral 17° angle Kappa and a 17° right eye esotropia. The patient seems to have no strabismus, and to look to the left of the target, while his left eye is looking at the target. F, left eye fovea; F9 , right eye fovea; Star, fixation target; Full lines, visual axes; Dotted lines, pupillary axes. M.-A. Espinasse-Berrod, and M. Robert. Category 2: a. Drafting the manuscript: M. Rateaux and M. Robert; b. Revising it for intellectual content: M.-A. Espinasse-Berrod, C. Couret, and D. BremondGignac. Category 3: a. Final approval of the completed manuscript: M.-A. Espinasse-Berrod and M. Robert. REFERENCES 1. Couret CC, Lebranchu PP, Le Meur GG, Pechereau AA. Semiautomatic measurement of horizontal angle of strabismus using digital pictures. J AAPOS. 2018;22:e19. 2. Summers CG. Vision in albinism. Trans Am Ophthalmol Soc. 1996;94:1095–1155. e236 3. Thomas MG, Kumar A, Mohammad S, Proudlock FA, Engle EC, Andrews C, Chan WM, Thomas A, Gottlob I. Structural grading of foveal hypoplasia using spectral-domain optical coherence tomography a predictor of visual acuity? Ophthalmology. 2011;118:1653–1660. 4. Sjödell L, Sjöström A, Abrahamsson M. Transillumination of iris and subnormal visual acuity—ocular albinism? Br J Ophthalmol. 1996;80:617–623. 5. Basmak H, Sahin A, Yildirim N, Papakostas TD, Kanellopoulos AJ. Measurement of angle kappa with synoptophore and Orbscan II in a normal population. J Refract Surg. 2007;23:456–460. 6. Merrill KS, Lavoie JD, King RA, Summers CG. Positive angle kappa in albinism. J AAPOS. 2004;8:237–239. Rateaux et al: J Neuro-Ophthalmol 2021; 41: e234-e236 Copyright © North American Neuro-Ophthalmology Society. 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