Download Sheerer, E

Resident’s Day Poster Submission
First Author: Elsa Sheerer, OD*
Second Author: Noelda Fernandes, OD*
*Pediatric Optometry Resident, 2015-16, SUNY College of Optometry
Title (max 150 characters): Optometric examination and Management in Rett
Syndrome
Abstract (max 35 words): A nine year old Hispanic female with Rett Syndrome (RS)
presents to the University Eye Center. Responses to visual stimuli are inconsistent,
prompting electrodiagnostic testing to determine potential visual function. Ocular
Manifestations in RS are discussed.
I. Case History
Patient demographics: 9 year old Hispanic female with history of Rett Syndrome (RS)
Chief complaint: left visual field preference and prefers visually attending to real objects
rather than pictorial representations
Ocular history: bilateral eye muscle surgery for intermittent esotropia at age 6
Medical history:
(+) Rett Syndrome;
patient is non verbal and wheelchair bound. Exhibits continuous involuntary movement
of limbs, head, and trunk. Difficulty with eating due to constant movement
(+)seizures
Medications:
-- Trihexiphenidyl
-- Kepra
-- Triolepto
-- Clonidine
Allergies: none, No Known Medical Allergies
Other salient information:
Attending a school for children with Traumatic Brain Injury (TBI) for 1 year
receiving Speech Therapy, Physical Therapy, Occupational Therapy
receiving vision rehabilitation with an aid specializing in educational visual needs.
per aid, child can visually track bright, shiny objects.
per aid, child responds better to high contrast pictures
Child's visual needs include:
-- looking at Mayer-Johnson communication symbols used to communicate.
-- food for eating.
Developmental history:
-- Full term pregnancy
-- No complications during pregnancy or birth.
II. Pertinent findings
Clinical
Visual acuity OD/OS: fix and follow at times with transilluminator. Child does not pick
up fixation with any consistency. Eye movements are erratic.
Visual field: inconclusive OD/OS
EOMs: full, a lot of head movement
Pupils: PERRL (-)APD
Retinoscopy:
OD: +1.00 sph
OS: +1.00 sph
Hand held slit lamp biomicorosocpy:
Adnexa: normal OD/OS
Eye lids and lashes: normal, good apposition, OD/OS
Conjunctiva: white and quiet OD/OS
Cornea: clear, normal endothelial, epithelial, stroma and tear film OD/OS
Iris: flat and intact OD/OS
Anterior Chamber: deep and quiet OD/OS
Crystalline lens: clear capsule, cortex, and nucleus OD/OS
Digital intraocular pressure:
OD/OS: soft and equal
Time: 10:00AM
Dilated with 0.5% Trompicamide
Dilated Fundus Exam attempted but poor clinical views due to poor cooperation and
constant movement from patient
Ultrasound studies:
B-scan ultrasonography:
Retina is flat and intact OD/OS.
Physical
Child preferred leaning and turning head toward left side.
Trial Frame (TF):
OD: +1.00 sph 4 Prism Diopters Base Right
OS: +1.00 sph 4 Prism Diopters Base Right
Child appeared to have more straight head posture. However, it is unclear whether the
patient was responding to TF or simply changed her posture consistent with her erratic
movement.
Others
Visually Evoked Potential (VEP) Results: pending
III. Differential diagnosis
Primary/leading
Little to no visual function vs. unable to elicit visual response. Schedule next available
visually evoked potential to determine visual potential.
Others
Functional vision intact, suggested by VEP.
IV. Diagnosis and discussion
It has been suggest that because of the poor attention and lack of interest in behavioral
tests, visually evoked potentials provide the most useful test of visual acuity in Rett
Syndrome1. Despite some reports of successful visual acuity measurement by forced
preferential looking methods, those methods were not able to be used in this case. In
fact, no fix and follow response was consistently elicited. The severe motor decline of
the patient who elicited incessant large head and limb movements throughout the exam
must be taken into consideration, as the child may not have been able to motorically
respond to the clinical testing. However, since the literature supports functional vision in
the majority of Rett Syndrome, a visually evoked potential (VEP) is indicated, preferably
to include grating potentials to estimate the potential visual acuity. It is important to note
that a robust VEP response does not rule out cortical visual impairment2. If the VEP
proves to have promising visual function results, spectacles should be trialed for
improved behavioral results as reported by the parents and educational specialists. In
this case, the optometrist should consider prescribing based right prism because of the
child left visual field preference and left-leaning posture in order to possibly improve
posture and front-facing gaze. The hyperopia could be corrected for better visual clarity
in this case. Optometric evaluation of patients with Rett Syndrome, other developmental
delays, and those with severe motor and/or verbal deficits must consider
electrophysiological testing in cases where traditional clinical testing. Review of the
literature confirmed the need to establish visual functional potential in this patient.
Furthermore, the use of spectacles to correct refractive error and the use of prisms to
correct posture or field preference must be considered for optimal visual function of
patients with developmental disorders.
Elaborate on the condition
Rett syndrome is a neurodevelopmental disorder that affects females nearly
exclusively in a ration of 1:10,000 to 1:22,000 live female births3. The syndrome is
characterized by normal development until around 6 months of age followed by a
slowing of developmental progress. Skills such as feeding, walking, and talking may be
achieved which reach their peak around age 12 months. Shortly after, a period of
regression in which speech and fine motor control are lost. Eventually, those affected
lose nearly all function off their hands and become profoundly physically and mentally
disabled. At this point, the condition stabilizes.
The most common genetic mutation implicated in classic RS is a mutation of the
methyl CpG binding protein 2, or MECP2 gene on the X chromosome4. The MeCP2
protein is responsible for gene expression during early development leading to the
improper refinement of cortical circuits5. Interestingly, the MECP2 expression is very
limited in the afferent visual pathway in normals and Rett Syndrome6. This corresponds
to clinical findings of usually intact visual function in Rett Syndrome patients. Other
mutations on the X chromosome in atypical RS are CDKL5 and WDR45. A mutation in
FOXG1 on chromosome 14 has been identified in a congenital variant of RS. Recently,
specific mutations in RS have been linked to specific functional outcomes in RS, such
as hand use and ambulation7. Genetic testing for these mutations is now available,
however diagnosis is based on the clinical phenotype.
Rett Syndrome has a distinct profile of visual function, refractive error, and
binocular status. Cortical visual impairment (CVI) has also been reported in those with
Rett Syndrome8. CVI is defined as all visual dysfunctions caused by damage to, or
malfunctioning of, the retrochiasmic pathways in the absence of any major ocular
disease9. Despite demonstrating varying degrees of CVI, visual function is one of the
few faculties that remain intact in RS. Visual acuity measured with forced preferential
looking and visually evoked potential suggest that nearly all with Rett Syndrome
maintain functional vision. Additionally, fix and follow function is retained 86-94% in
RS10. Interestingly, a high incidence of nystagmus and strabismus seems to spare Rett
Syndrome, unlike the majority of other neurodevelopmental disorders. However, there
does seem to be a higher incidence of significant refractive error in Rett Syndrome
compared to the normal population1,11. A distinctive feature and supporting diagnostic
criteria of variant Rett Syndrome is intense fixed gaze and using eye-pointing, the latter
of which has been reported as a method of communication 1,12,13,14,15. Prolonged gaze or
staring has been linked to lower cognitive function in contrast to those who have a more
active gaze11.
Most cognitive testing relies on a motor or verbal response. Because visual
function remains while motor and verbal abilities deteriorate, eye movement tracking
technologies are now being used to test cognitive function instead of traditional
methods16.
Expound on unique features
1. Strabismus is unusual in Rett Syndrome: in one clinical study, only 1 in 11
patients with Rett Syndrome had strabismus and it was exotropic in nature1; in
this case, per the report history, the child had esotropic strabismus and corrective
eye muscle surgery.
2. Fixed gaze and eye-pointing have been reported as distinct features of the
syndrome12,13,14,15 However, this patient did not exhibit those features.
3. There are conflicting reports of using forced preferential looking visual acuity
methods successfully in Rett Syndrome Patients1,11; forced preferential looking
was not able to be used in this case.
4. Flash and grating VEPs demonstrate potential for usable vision in RS1,17,18.
Results pending from VEP and there is a possibility of an abnormal VEP
compared to those of others with RS.
5. Fix and Follow skills are retained in 86%-94% of those with RS10 . This patient
did not retain Fix and follow skills
V. Treatment, management
Electrodiagnostic testing is essential to the management of this patient’s visual function.
If the VEP results indicate potential for functional vision, spectacle should be trialed for
possible behavior improvements. If the VEP results indicate poor potential for functional
vision, the parents and educational specialists need to be advised to focus on using
other senses, such as auditory and touch, for learning and rehabilitation. Because
patients with limited communication and cognitive ability cannot communicate when
something is wrong or changes with their eyes or vision, these patients need to be
examined regularly by an optometrist to monitor visual function and ocular health.
VI. Conclusion
This case does not fit the visual function profile of Rett Syndrome, but highlights
important considerations in the management of patients with limited communication and
motor abilities.
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