Exotropias: A Brief Review Leila M. Khazaeni, MD November 2, 2008
Exotropia Myths Myth #1 He/she will grow out of it FALSE 75% of XTs show progression over a 3 year period Myth #2 The only treatment choice is surgery FALSE observation and convergence exercises are an option for some cases Myth #3 It can only be fixed surgically before age 5 5 FALSE surgical correction is possible at any time; level of control dictates surgical timing
Case 1 4 year old boy presents with : ZZZ zzzz his right eye has been LAZY for 1 year according to mom.
The Lazy Eye Very vague complaint Amblyopia?? (Poor vision in an eye that cannot be attributed to structural pathology) Esotropia?? (Turning in) Exotropia? (Turning out) Hypertropia?? (Turning up) Ptosis? (Droopy eyelid)
Intermittent Exotropia An outward drifting of either eye interspersed with periods of good alignment of the eyes Appears during age 1-21 2 in 30 % of cases Begins as a latent deviation ( Phoria) (Phoria 75% will show progression over 3 year period
Classification of Intermittent Exotropia Basic, intermittent XT Divergence excess XT Pseudodivergence excess XT Convergence Insufficiency
Classification of Intermittent Exotropia Basic, intermittent XT Distance and near deviation are within 10 Δ Divergence excess XT Distance deviation > Near deviation by 10 Δ Pseudodivergence excess XT initial Distance deviation > Near deviation by 10 Δ Convergence Insufficiency Near Deviation > Distance deviation by 10 Δ
Case 1 4 year old boy presents with 1 year history of right eye wanders out Stereoacuity +Fly, 3/3 animals, 7/9 circles 20/25 OD, 20/25 OS 30 Δ X(T) at near and distance Cycloplegic refraction +1.00 OD, +1.25 OS Pupils, Motility, Ant segment, Fundus exams normal
Diagnosis? 30 Δ X(T) at near and distance Visual Acuity is symmetric, cyclo refraction minimal, remainder of exam normal Basic Intermittent Exotropia
What are the key elements of the STEREOPSIS should be measured FIRST!!! (BEFORE VISUAL ACUITY) exam?
Visual Acuity Visual Acuity should be checked carefully to rule out amblyopia. Patch each eye to prevent little ones from peeking Use crowding bars or check vision using a line of optotypes
Extraocular Motility Assess extraocular motility carefully A motility deficit might indicate a cranial nerve palsy, strabismus syndrome or thyroid eye disease
Strabismus Measurement Cover Testing Cover/Uncover differentiates phoria from tropia Alternate Cover measures sum total of phoria and tropia by preventing binocularity These require central fixation and should be performed at near and distance If central fixation not possible, use Krimsky or Hirschberg methods This may indicate a sensory XT
Hirschberg 1 mm = 7 degrees = 15 prism diopters 2 mm = 30 prism diopters Inside edge of pupil 3 mm = 45 prism diopters Middle of iris 4 mm = 60 prism diopters Outer edge of iris
Assessing Control Level of control can be determined based on frequency, duration and speed of recovery from a manifest to a latent deviation Examiner Assessment of control: Good Control deviation only present after cover testing Fair Control BLINK or refixation movement required to regain control Poor Control deviation spontaneously manifests
Assessment of Control Parents may assess control at home by observing: Excellent Control Present < 10 % of waking hrs, only at distance or when sleepy/daydreaming Good Control Present < 5 times per day, and only at distance Fair Control Present > 5 times per day, and only at distance Poor Control Present > 50 % of time at distance and at near
Assessment of Control Role of stereoacuity Distance control deteriorates before near control deteriorates. Exotropia at distance has deteriorated to a significant degree by the time near stereoacuity is affected. If stereo testing at distance is available, it can help indicate early loss of control If stereoacuity at near is deteriorating, this is an important sign that it is late in the game
Late in the Game Spontaneously Manifest XTs. Everyone agrees these patients need surgery. The trick is to catch these patients earlier.
Case 1 revisited 4 year old boy presents with 1 year history of right eye wanders out Stereoacuity +Fly, 3/3 animals, 7/9 circles 20/25 OD, 20/25 OS 30 Δ X(T) at near and distance Cycloplegic refraction +1.00 OD, +1.25 OS Pupils, Motility, Ant segment, Fundus exams normal Dx: Basic Intermittent XT
Management? Prescribe glasses? Start Patching? Prescribe glasses and start patching? Refer for surgical evaluation?
Case 1: Management Observe, follow every 4 months to monitor stereoacuity,, visual acuity. Consider surgery when : Happening >50% of time Happening when not sick or tired Decreasing control in clinic (easily dissociated, slow to recover, does not recover with a blink) Decrease in stereopsis
A Slight Variation on Case 1 4 year old boy presents with 1 year history of right eye wanders out - occasional at first, but now happening more often Stereoacuity +Fly, 3/3 animals, 7/9 circles 20/50 OD,, 20/25 OS 30 Δ X(T) at near and distance Cycloplegic refraction +1.00+1.50 x 90 OD +1.25 OS Pupils, Motility, Ant segment, Fundus exams normal
Case 1.5 Management? Diagnosis Exotropia AND Amblyopia! Treatment TREAT AMBLYOPIA FIRST!!! Prescribe glasses plano +1.50 x 90 OD and plano OS May need to begin patching OS 2-42 4 hours /day F/U every 2 months while patching to monitor Va Consider surgery when vision is symmetric
Surgery for Exotropia Choices BLR bilateral lateral rectus recession BMR resect bilateral medial rectus resection Monocular Recess/Resect Resect procedure If it s s a REALLY big XT, BLR and unilateral BMR resect,, or BLR and BMR resect
Case 2 7 year old boy presents with 3 year history of eyes wandering out Eyes wandering out for 3-43 4 years Stereo +fly, 2/3 animals, 4/9 cirlces Va 20/20, 20/20 X(T) = 40 Δ,, X(T) = 10 Δ After 30 minute patch test, X(T) = X(T) = 40 Δ
Divergence Excess XT Divergence Excess XT After 30 minute patch test, near deviation does NOT increase (or with use of +3.00) lens)
Pseudodivergence Excess XT After 30 minute patch test or use of +3.00 lenses, near deviation increases to within 10 Δ of distance deviation Normal AC/A ratio & Tenacious proximal fusion High AC/A ratio Normal AC/A ratio, pseudo-high AC/A ratio & Tenacious proximal fusion
Surgical Treatment In cases of True, or Pseudo Divergence Excess Exotropia, Medial Rectus Resections should be avoided BLR is the treatment of choice
Case 3 8 year old girl presents with difficulty reading - referred by school for evaluation Va 20/20 OD, 20/20 OS EOM full 10 Δ X(T) at near Near point of convergence 10 cm Cycloplegic refraction +1.50 OU
Convergence Insufficiency Near deviation exceeds distance deviation by > 10 Δ May present as reading fatigue, asthenopia, blurred vision, intermittent diplopia at near Treatment may include convergence exercises if deviation is less than 10 Δ
Treatment Convergence Insufficiency Exotropia is best corrected surgically by Medial Rectus Resections Often, convergence exercises such as pencil push-ups ups may help
Summary: Intermittent Exotropia Subtypes Basic Intermittent XT Divergence Excess, Pseudodivergence Excess XT Convergence Insufficiency Management Maximize vision first Consider surgery when deteriorating control Surgery is tailored to the clinical subtype
Other XT s Sensory XT Thyroid Eye Disease 3 rd Nerve Palsy Scleral Buckle
Case 4 20 year old man presents with left eye has wandered out for 2 years Va 20/20 OD, 20/400 OS LXT = 40 Δ at near and distance by Krimsky
Sensory Exotropia XT due to very poor vision in one eye WHY??? Must do thorough exam to find cause of poor vision Retinal detachment, Retinal pathology, Optic nerve pathology Congenital defect (colobomas( colobomas,, untreated cataract, optic nerve hypoplasia) These patients have poor fixation and are monocular: Monocular precautions (polycarbonate glasses) No/poor stereoacuity expected Use Krimsky or Hirschberg to measure
Treatment Sensory XT Elucidate underlying pathology MONOCULAR PRECAUTIONS Surgical options Recess/Resect Resect procedure preferred Monocular surgery performed on poor eye Surgical risk limited to poor eye Is treatment purely cosmetic? Social implications When asked, these patients often have peripheral diplopia
Exotropia: The Future Are children with exotropia doomed to become adults with exotropia? Is there certain decompensation and need for reoperation by age 30?
summary
To quote country music Know when to hold em and know when to fold em Kenny Rogers, The Gambler
Know when to hold em Intermittent XT (Basic, DE or Pseudo-DE) with good control and good stereopsis Convergence Insufficiency XT doing well on a regimen of convergence exercises Intermittent XT with amblyopia who is undergoing amblyopia treatment with good results
And Know when to fold em (When to refer ) 1. Intermittent Exotropia with deteriorating control 2. Any Sensory Exotropia 3. Exotropia associated with ptosis 4. Exotropia associated with motility deficit
Remember Pearls 75% of intermittent XTs will progress To check stereoacuity BEFORE visual acuity That when near stereoacuity deteriorates, control is already lost To treat amblyopia before strabismus To look for other findings ptosis, motility deficits That everyone will agree when its too late to operate its much harder to catch these pts on the brink of losing control.