Appendix C: Illustrative Cases and Treatment

Nystagmus in infancy and childhood outlines the understanding, evaluation, and treatments of nystagmus in infancy and childhood. Aligning this condition with advanced concepts of developmental brain-eye diseases and summarizing novel treatment paradigms, the authors provide an authoritative resource for both clinicians and scientists in the care of infants and children with nystagmus. The chapters comprised here offer valuable coverage in all relevant areas related to nystagmus: algorithms for examination; descriptions of diagnostic techniques; medical, surgical, and alternative treatments of the visual system in infants and children; methodologies for investigation, including analysis software, models of the ocular motor system, and current hypotheses on the pathophysiology of ocular motor oscillations. Unlike earlier works on this topic, emphasis is placed on the motor mechanisms that cause the various types of nystagmus rather than the diagnosis or treatment of the afferent visual deficits that may accompany them. The study of each type of nystagmus using accurate eye-movement recordings serves as the foundation for differential diagnosis and treatment options. Each chapter summarizes the results of ocular motor research in a narrative manner, identifying the important ideas and observations that point to underlying neurophysiological mechanisms. Based on insights from the authors' combined 75 years of clinical experience, Nystagmus in Infancy and Childhood is a valuable clinical reference for ophthalmologists, neurologists, and other specialists in the treatment of this condition.

OUP UNCORRECTED PROOF – REVISES, 09/06/12, NEWGEN appendix c illustrative cases and treatment C.1 INFANTILE NYSTAGMUS SYNDROME 281 C.1.1 Gaze-Angle Null Only 281 C.1.1.1 Version Prisms 281 C.1.1.2 Soft Contact Lenses 281 C.1.1.3 Four-Muscle Resection, Recession, and Tenotomy and Reattachment 281 C.1.1.3.1 Fine Tuning with Prisms 281 C.1.1.3.2 Soft Contact Lenses 281 C.1.2 Convergence Null Only 281 C.1.2.1 Vergence Prisms with Negative Spheres 282 C.1.2.2 Soft Contact Lenses 282 C.1.2.3 Bimedial Recession 282 C.1.3 Both Gaze-Angle and Convergence Nulls 282 C.1.3.1 Convergence > Gaze-Angle 282 C.1.3.1.1 Composite Prisms and Negative Spheres 282 C.1.3.1.2 Base-Out Prisms and Negative Spheres 283 C.1.3.1.3 Soft Contact Lenses 283 C.1.3.1.4 Bimedial Recession 283 C.1.3.2 Gaze-Angle > Convergence 283 C.1.3.2.1 Version Prisms 283 C.1.3.2.2 Soft Contact Lenses 283 C.1.3.2.3 Four-Muscle Resection, Recession, and Tenotomy and Reattachment 283 C.1.4 No Nulls 283 C.1.4.1 Soft ContacWt Lenses 283 280 C.1.4.2 Four-Muscle Tenotomy and Reattachment 283 C.1.4.2.1 Tenotomy and Reattachment with Augmented Tendon Suture 284 C.1.4.2.2 Augmented Tendon Suture Procedure sans Tenotomy and Reattachment 284 C.1.4.3 Faden 284 C.2 INFANTILE NYSTAGMUS PLUS STRA BISMUS 284 C.2.1 Gaze-Angle Null Only 284 C.2.1.1 Four-Muscle Resection, Recession, and Tenotomy and Reattachment 284 C.2.2 Vertical and Torsional Nulls 284 C.2.3 No Nulls 286 C.2.3.1 Four-Muscle Tenotomy and Reattachment and Strabismus 286 C.3 FUSION MALDEVELOPMENT NYSTAGMUS SYNDROME 286 C.3.1 Uniocular Fixation 286 C.3.2 Alternating Fixation 286 C.3.3 Alexander’s Law Th reshold 286 C.4 NYSTAGMUS BLOCKAGE SYNDROME 287 C.4.1 Bimedial Recession (Plus Tenotomy and Reattachment) 287 C.4.2 Recession and Resection Plus Tenotomy and Reattachment 287 C.4.3 Four-Muscle Tenotomy and Reattachment 287 • 12_Hertle_Appendix_C.indd 280 9/6/2012 9:49:45 PM OUP UNCORRECTED PROOF – REVISES, 09/06/12, NEWGEN C.1 INFANTILE NYSTAGMUS SYNDROME Th is section contains examples of optical and surgical nystagmus therapies for patients with infantile nystagmus syndrome (INS) whose characteristics determine which is the most effective therapy. C.1.1 Gaze-Angle Null Only The therapeutic options for an INS patient with a gaze-angle null (i.e., an eccentric eXpanded nystagmus acuity function [NAFX] peak) depend on three things: the eccentricity, the depth, and the breadth of the null, as discussed in Chapter 2. If nystagmus surgery is indicated, the amount necessary is determined by the eccentricity. C .1.1.1 V E R S I O N P R I S M S If the null is close to primary position (e.g., < 5° = 8.75 PD) and is broad (e.g., > 25°), version prisms may be used to center it, however. At larger eccentricities, the required prism would be too great, causing both chromatic aberration and diminished acuity. At narrower breadths, a therapy that broadens the null (version prisms do not) is more suitable. In the example shown in Figure C.1, the null is >20° to the right and the four-muscle resection and recess procedure is used. In the example shown in Figure C.2, the null is <20° to the right and the two-muscle recession plus two-muscle T&R procedure is used to center and broaden the null. C.1.1.3.1 Fine Tuning with Prisms. It used to be thought that if the surgery to center the null was insufficient, postoperative fi ne-tuning with the use of version prisms could achieve the desired result. However, the use of eye-movement data (to determine the surgical rotation needed) plus documentation of the null-broadening effects of the surgery itself have precluded the need for postoperative prisms in most cases. C.1.1.3.2 Soft Contact Lenses. Just as soft contact lenses improve INS before surgery, they can be used postoperatively in lieu of eyeglasses. The extent of further improvement has not been studied and may be idiosyncratic. C.1.2 Convergence Null Only The therapeutic options for an INS patient with a convergence null (i.e., an NAFX peak at C .1.1. 2 S O F T CO N TA C T L E N S E S If the null is in primary position and is narrow, soft contact lenses may be used to improve the range of gaze angles with best-corrected visual acuity (i.e., broaden the null); they may also improve the peak acuity. C .1.1.3 F O U R- M US C L E R E S EC T I O N , R EC E SS I O N , A N D T E N OT O M Y A N D R E AT TA C H M E N T If the null is at any eccentricity >10° and is of any breadth, the four-muscle resection and recession procedure or the two-muscle recession plus tenotomy and reattachment (T&R) of the other two muscles may be used. These nystagmus surgeries both center and broaden the null. FIGURE C.1 Operation 1—Bilateral horizontal rectus recession and resection to improve a horizontal head posture and the nystagmus associated with a moderate to large horizontal eccentric-gaze null. The percentage indicates the incidence of this procedure. The operation number reflects the order of these incidences. LR, lateral rectus; MR, medial rectus. Nystagmus in Infancy and Childhood • 281 12_Hertle_Appendix_C.indd 281 9/6/2012 9:49:45 PM OUP UNCORRECTED PROOF – REVISES, 09/06/12, NEWGEN C.1.2.2 Soft Contact Lenses Soft contact lenses can also be used to broaden the null when the base-out prisms are not in use, such as for some sports where eyeglasses would interfere, or socially if preferred by the patient. C.1.2.3 Bimedial Recession FIGURE C.2 Operation 1B—Bilateral horizontal rectus recession and tenotomy + reatt achment to improve a horizontal head posture and the nystagmus associated with a small horizontal eccentric-gaze null. The percentage indicates the incidence of this procedure. The operation number reflects the order of these incidences. LR, lateral rectus; MR, medial rectus. near) depend on only one thing: the absence of strabismus. Whether through the use of base-out prisms or bilateral medial rectus recessions, convergence-induced foveation improvement and null broadening is the most therapeutically beneficial method currently available. When both gaze-angle and convergence nulls are present, the latter is almost always greater. The bimedial recession operation is the most therapeutically powerful nystagmus surgery for INS. Originally, the addition of bilateral lateral rectus T&R to the bimedial recessions was advocated to achieve the maximal benefits of four-muscle T&R. However, research has shown that convergence alone (e.g., fi xation on a near target or through the use of base-out prisms) achieves the maximal improvements in NAFX values and negates the need for the addition of the T&R of the lateral rectus muscles. Th is is the only nystagmus surgery where operating on two muscles will provide foveation improvements that are equivalent to operating on all four. Because the bimedial recession nystagmus surgery for binocular INS patients induces convergence, it has different therapeutic benefits than the same strabismus surgery for esotropic patients, where it does not induce convergence. The patient in Figure C.3 has INS that damps with convergence and has no strabismus. The artificial divergence produced by the bimedial recessions induces the convergence necessary to improve the INS foveation quality at distance. C.1.2.1 Vergence Prisms with Negative Spheres C.1.3 Both Gaze-Angle and Convergence Nulls Although the NAFX continues to increase as the eyes converge by as much as 60 PD, the use of base-out prisms to improve the foveation quality at distance is accomplished by 7 PD base-out OU (i.e., a total of 14 PD of convergence) with the addition of –1.0 S OU to negate the vergence-induced accommodation in children and young adults. Th is allows for further convergence at middle-distance and near targets without loss of fusion and the resulting diplopia. At the onset of presbyopia, these added negative spheres must be removed from the prescription. 282 Some INS patients exhibit both gaze-angle and convergence nulls. Th is allows for several approaches, although one is the most effective. C.1.3.1 Convergence > Gaze-Angle C.1.3.1.1 Composite Prisms and Negative Spheres. It used to be thought that in cases with both types of nulls, a combination of version and vergence prisms (i.e., composite prisms) would provide the greatest improvement in foveation quality. However, research has shown that • ILLUSTR ATI V E CASES A ND TR E ATM ENT 12_Hertle_Appendix_C.indd 282 9/6/2012 9:49:46 PM OUP UNCORRECTED PROOF – REVISES, 09/06/12, NEWGEN these cases, the same therapies recommended for gaze-angle-only cases apply. C.1.3.2.1 Version Prisms. If the null is close to primary position (e.g., < 5° = 8.75 PD) and is broad (e.g., > 25°), version prisms may be used to center it. At larger eccentricities, the required prism would be too great, causing both chromatic aberration and diminished acuity. At narrower breadths, a therapy that broadens the null is more suitable. FIGURE C.3 Operation 8—Bilateral medial rectus recession with bilateral horizontal rectus tenotomy and reatt achment (T&R) to induce vergence and improve the nystagmus. Subsequent research indicates that the addition of the bilateral T&R is unnecessary. The percentage indicates the incidence of this procedure. The operation number reflects the order of these incidences. LR, lateral rectus; MR, medial rectus. because of the large broadening of the gaze-angle range of highest NAFX caused by the convergence, gaze angle becomes inconsequential and the need for composite prisms is negated. The negative spheres are still required for pre-presbyopic patients (e.g., children and young adults). C.1.3.1.2 Base-Out Prisms and Negative Spheres. Because of the aforementioned fi ndings, the same base-out prisms with negative spheres are used in these cases as in those with only convergence damping. C.1.3.1.3 Soft Contact Lenses. As in the aforementioned cases, soft contact lenses can also be used to broaden the null when the baseout prisms are not in use. C.1.3.1.4 Bimedial Recession. The bimedial recession nystagmus procedure described earlier is the recommended therapy for these cases. C.1.3.2.2 Soft Contact Lenses. If the null is in primary position and is narrow, soft contact lenses may be used to improve the range of gaze angles with best-corrected visual acuity and may improve peak acuity. C.1.3.2.3 Four-Muscle Resection, Recession, and Tenotomy and Reattachment. If the null is at any eccentricity >10° and is of any breadth, the four-muscle resection and recession procedure or the two-muscle recession plus T&R of the other two muscles may be used to center and broaden the null. In these rare cases, the bimedial recession nystagmus surgery may be combined with this surgery in an attempt to maximize the foveation improvements. C.1.4 No Nulls There are some patients with INS who have no null or whose null is in primary position. Prior to the discovery of the beneficial effects of the fourmuscle T&R nystagmus surgery, these patients had no therapy available to improve their foveation quality. C.1.4.1 Soft Contact Lenses As in the aforementioned cases, soft contact lenses can also be used to further damp the INS. C.1.3.2 Gaze-Angle > Convergence C.1.4.2 Four-Muscle Tenotomy and Reattachment There are very rare cases where eye-movement data show that the gaze-angle improvements in foveation may exceed those of convergence. For The patient in Figure C.4 had no INS nulls. The therapy of choice was the four-muscle T&R procedure. Nystagmus in Infancy and Childhood • 283 12_Hertle_Appendix_C.indd 283 9/6/2012 9:49:46 PM OUP UNCORRECTED PROOF – REVISES, 09/06/12, NEWGEN C.2 INFANTILE NYSTAGMUS PLUS STRABISMUS C.2.1 Gaze-Angle Null Only Many INS patients also have strabismus. Their treatment mimics those described earlier with the additional recessions or resections needed to correct the strabismus. FIGURE C.4 Operation 6—Bilateral horizontal rectus tenotomy and reatt achment alone to improve the nystagmus. The percentage indicates the incidence of this procedure. The operation number reflects the order of these incidences. C.1.4.2.1 Tenotomy and Reatt achment with Augmented Tendon Suture. It has been hypothesized that adding a suture or two to each tendon undergoing a T&R might result in greater improvement. These additional sutures are placed in the tendons alone, not to the globe. If the data confi rm this hypothesis, the augmented suture technique would be recommended. C.1.4.2.2 Augmented Tendon Suture Procedure sans Tenotomy and Reattachment. A related hypothesis has also been advanced. Simply placing a suture or two to each tendon (again, not to the globe) without performing a T&R might also result in improvement, greater than or equal to the T&R. Again, if the data confirm this, the augmented suture technique sans T&R would be recommended; it is both simpler and safer than suturing to the globe. C.2.1.1 Four-Muscle Resection, Recession, and Tenotomy and Reattachment Many patients have strabismus and nystagmus with an eccentric gaze null (i.e., either INS or FMNS). The operation shown in Figure C.5 corrects the strabismus and improves the nystagmus. The INS patient in Figure C.6 had a left ward null position and an esotropia. The nystagmus plus strabismus surgical procedure employed combined the necessary recessions and resections to improve both the INS foveation quality and the ocular alignment. C.2.2 Vertical and Torsional Nulls Many INS patients have nulls in the vertical or torsional plane, despite the horizontal C.1.4.3 Faden The Faden procedure has not been studied using the eye-movement, data-based analysis techniques described in Chapter 2; therefore, its potential benefits as a nystagmus surgery used instead of, or in concert with, the surgeries presented in this appendix cannot be assessed at this time. 284 FIGURE C.5 Operation 3—Bilateral horizontal rectus (BLR) and bimedial horizontal rectus (BMR) recession (RES), resection (REC), or tenotomy (T) to improve the strabismus, anomalous head posture, and the nystagmus associated with an eccentric-gaze null. The percentage indicates the incidence of this procedure. The operation number reflects the order of these incidences. • ILLUSTR ATI V E CASES A ND TR E ATM ENT 12_Hertle_Appendix_C.indd 284 9/6/2012 9:49:47 PM OUP UNCORRECTED PROOF – REVISES, 09/06/12, NEWGEN FIGURE C.6 Operation 4—Bilateral horizontal rectus recession and resection to improve the strabismus and the nystagmus associated with a primary position null. The percentage indicates the incidence of this procedure. The operation number reflects the order of these incidences. ET, esotropia; LE, left eye; LR, lateral rectus; MR, medial rectus. predominance of the nystagmus. The same principles embodied in nystagmus surgery of the horizontal rectus muscles must be applied to the vertical rectus and oblique muscles. Patients like the one in the Figure C.7 have a vertical null (in upgaze) with or without FIGURE C.7 Operation 2—Bilateral superior rectus recession and inferior oblique myectomy with bilateral single horizontal recti tenotomy with reatt achment or recession to improve a chin-down head posture and the nystagmus +/- strabismus associated with a vertically upward eccentric-gaze null. The percentage indicates the incidence of this procedure. The operation number reflects the order of these incidences. BIO, bilateral inferior oblique; BS, bilateral superior rectus. strabismus. A bilateral superior rectus recession and bilateral inferior oblique myectomy is used to center the vertical null plus either a bilateral medial or lateral rectus T&R (if no strabismus) or a bilateral medial or lateral rectus recession (if strabismus). Patients like the one in Figure C.8 have a vertical null (in downgaze) with or without strabismus. The surgical procedure combines the necessary recessions and resections to improve both the INS foveation quality and eye alignment, if strabismus is present. Patients like the one in Figure C.9 have a multiplanar null position (here, torsionally counterclockwise and to the left); they may or may not have strabismus. The surgical procedure combines the necessary nystagmus surgery to improve the INS foveation quality and addition of strabismus surgery to improve eye alignment, if strabismus is present. Patients like the one in Figure C.10 have a torsional null position; the patient has a counterclockwise INS null. The nystagmus surgical procedure corrects the torsional null. FIGUR E C.8 Operation 5—Bilateral inferior rectus recession and superior oblique tenectomy with bilateral single horizontal recti tenotomy with reattachment or recession to improve a chin-up head posture and the nystagmus +/- strabismus associated with a vertically downward eccentric-gaze null. The percentage indicates the incidence of this procedure. The operation number ref lects the order of these incidences. BI, bilateral inferior rectus; BSO, bilateral superior oblique. Nystagmus in Infancy and Childhood • 285 12_Hertle_Appendix_C.indd 285 9/6/2012 9:49:48 PM OUP UNCORRECTED PROOF – REVISES, 09/06/12, NEWGEN surgery with the addition of whatever recessions or resections are needed to correct the misalignment of the eyes. C.3 FUSION MALDEVELOPMENT NYSTAGMUS SYNDROME FIGURE C.9 Operation 7—Bilateral horizontal rectus muscle transposition with or without associated resection/recession to improve a multiplanar head posture, the nystagmus +/- strabismus associated with multiplanar eccentric-gaze null. The percentage indicates the incidence of this procedure. The operation number reflects the order of these incidences. LR, lateral rectus; MR, medial rectus; REC, resection; RES, recession; TR, transposition. Patients with fusion maldevelopment nystagmus syndrome (FMNS) all have strabismus. Their surgical therapy will require strabismus surgery (to correct eye alignment) and may also require the T&R nystagmus surgery applied to horizontal rectus muscles not recessed or resected (to improve nystagmus foveation). C.3.1 Uniocular Fixation C.2.3.1 Four-Muscle Tenotomy and Reattachment and Strabismus Some FMNS patients always fixate with their preferred eye, regardless of gaze angle. For them, eye-muscle surgery combines operating on the nonpreferred eye plus T&R of the remaining horizontal rectus muscles. This may produce fusion damping in addition to the nystagmus damping from the surgery itself. INS patients with no nulls plus strabismus require the four-muscle T&R nystagmus C.3.2 Alternating Fixation C.2.3 No Nulls Some FMNS patients alternate their fixating eye, depending on gaze angle. In these cases, recessions of the two medial rectus muscles and T&R of the two lateral rectus muscles is recommended for small deviations. For exotropia, recessions of the two lateral rectus muscles and T&R of the two medial rectus muscles is recommended (again for small deviations). For large deviations, recessions and resections of all four horizontal rectus muscles sufficient to align the eyes is recommended. FIGURE C.10 Operation 9—Bilateral vertical rectus muscle transposition to improve a torsional/ tilt head posture and the nystagmus associated with a torsional gaze null. The percentage indicates the incidence of this procedure. The operation number reflects the order of these incidences. IR, inferior rectus; SR, superior rectus; TRA NS, transposition. 286 C.3.3 Alexander’s Law Threshold The amount and type of eye-muscle surgery may be affected by the preoperative intensity of the Alexander’s law threshold and slope (i.e., the gaze angles at which the FMN begins to increase and the rate of that increase). • ILLUSTR ATI V E CASES A ND TR E ATM ENT 12_Hertle_Appendix_C.indd 286 9/6/2012 9:49:50 PM OUP UNCORRECTED PROOF – REVISES, 09/06/12, NEWGEN C.4 NYSTAGMUS BLOCKAGE SYNDROME Nystagmus surgery for patients with the nystagmus blockage syndrome (NBS) is determined by the characteristics of the baseline INS (i.e., null angle depth and breadth) with no purposive esotropia. The variable esotropia with either eye fi xing is amenable to surgical correction, although the procedure is less well defi ned. The suggestions that follow apply to both types of the NBS (see Chapter 4). However, eye-movement data that could confi rm the efficacy of these suggestions are lacking. C.4.1 Bimedial Recession (Plus Tenotomy and Reattachment) If there is good binocular function, bimedial recession will result in improved baseline foveation due to convergence. If there is a static esotropia to which the purposive esotropia is added to improve foveation, a bimedial recession strabismus surgery to correct the maximum esotropia plus a T&R of the two lateral rectus muscles is recommended to improve both convergence and baseline foveation. C.4.2 Recession and Resection Plus Tenotomy and Reattachment If the purposive esotropia added to improve foveation, and is always in one eye, a head turn toward that eye results. In these cases, recession and resection to move the adopted eccentric position to primary position plus a T&R of the horizontal rectus muscles of the other eye may improve both foveation quality and reduce/ eliminate the head turn. The preferred eye drives the head. C.4.3 Four-Muscle Tenotomy and Reattachment If the eyes are aligned before the purposive esotropia is added to improve foveation and there is poor binocular fusion, a four-muscle T&R is recommended to improve baseline foveation. Nystagmus in Infancy and Childhood • 287 12_Hertle_Appendix_C.indd 287 9/6/2012 9:49:51 PM