The Ophthalmology Examinations Review - part 10 pot

Correct amblyopia Surgery Type of surgery Correct 1 overaction If ET is not corrected with spectacles Bilateral MR recession if deviation is greater for near Either bilateral MR recessio

Correct amblyopia

Surgery

Type of surgery

Correct 1 overaction

If ET is not corrected with spectacles

Bilateral MR recession if deviation is greater for near Either bilateral MR recession or recess-resect if deviation is same for near and distance Recess-resect if amblyopia in one eye

Other considerations

Correct V or A pattern

TOPIC 5 EXOTROPIA

W h a t a r e causes o f exotroDias?

“Exotropias are divergent misalignment of eyes.”

“The most common cause is intermittent XT.”

“Other causes include .”

111 CN palsy Myasthenia gravis Thyroid eye disease IN0

Consecutive XT (after correction for ET) Sensory XT (disruption of BSV in children e.g congenital cataract)

“Intermittent XT is a common divergent squint.”

“It can be divided into 3 types based on severity of XT for near versus far.”

“And into 3 phases ”

intermittent XT

1 Classification

Convergence insufficiency (worse for near, needs MR resection or recess-resect)

Divergence excess (worse for distance, needs LR recession)

Simulated excess (accommodative fusion controls deviation at near) True excess (diagnosed by adding “plus” 3D lens at near to control for accommodation) Basic (near and distance same, needs LR recession)

2 Phases

3 Clinical features

Goes through 3 phases

Phase 1 (intermittent XP at distance)

Phase 2 (XT at distance, XP at near)

Phase 3 (XT at distance and near)

Age of onset 2 years

Precipitated by illness, bright light, day-dreaming

Amblyopia not common

Correct refractive errors (myopia)

Correct amblyopia

Orthoptic treatment

Temporal retinal hemisuppression when eyes are deviated

ARC and eccentric fixation may be present

4 Management

Diplopia awareness

Indications (4 classic indications)

Fusional exercise (pencil pushups, base-out prism)

Surgery

Increase angle of XT

Decreasing stereopsis Abnormal head posture

Increase frequency of breakdown (i.e progressing from Phase 1 to 2)

TOPIC 6 VERTICAL SQUINTS

AND OTHER MOTILITY SYNDROMES

Congenital fibrosis syndrome

Double elevator palsy

Dissociated vertical deviation (DVD)

A and V patterns

3 Others (111 CN palsy, thyroid eye disease, blowout fracture)

T e l l m e about inferior oblique overaction

“10 overaction is a common vertical squint.”

“50% of patients with essential or congenital ET have 1 overaction.”

Inferior oblique overaction

1 Introduction

Clinical scenarios

With horizontal squints

Primary (uncommon) Significance of 10 overaction

Affects comesis Disruption of BSV

Bilateral, but may be asymmetrical

Paresis of one or both SO

Contribute to large angle ET

Upshoot of eye in adduction

Associated with SO underaction

Hypotropia of fellow eye (in DVD, only hypertropia of affected eye) Base up prism over fellow eye will neutralize hypotropia (in DVD, only base down prism over affected eye will correct hypotropia)

Grade+3

Grade+4

Marshall Park's point: 3mm lateral to lateral border of IR insertion + l m m behind Equivalent to 15mm of 10 recession

Can correct for DVD as well

HOW do you locate the 10 muscle durina surgery?

Localization of 1 0 during surgery

Isolate LR and IR

Tubular/worm like structure

10 is a pink tendon within white Tenon's

Pull 10 and feel tug at point of origin at orbital rim

Cannot be graded (all or none) Results less consistent

No benefit for DVD

"Duane's syndrome is an ocular motility disorder"

"The main clinical feature is retraction of the globe on attempted adduction "

"It can be classified into 3 types "

Section 9: Squints and Pediatric Eye Diseases 389

Usually orthophoric limitation in both adduction and abduction

2 Clinical features

Females more common

Left eye in 60%, bilateral in 20%

Retraction of globe on adduction (sine qua non)

Co-contraction of MR and LR Associated with narrowing of palpebral fissure

“What is the underlying pathogenesis?” Pontine dysgenesis with 111 CN innervating both MR and

LR

Ocular associations (8%)

Ptosis

Anisocoria Persistent hyaloid artery Myelinated nerve fibers Nystagmus

Agenesis of genitourinary system Bone (vertebral column abnormalities) CNS (epilepsy)

Upshoot or downshoot (lease phenomenon, do not mistake for 1 overaction!)

3 Ocular and systemic associations

Epibulbar dermoids (associated Goldenhar syndrome)

Systemic associations

Deafness (sensory neural deafness is the most common association, 16% of all Duane’s) Dermatological (cafe au lait spot)

Correct amblyopia

Indications for surgery

Wildervank’s syndrome (Duanes’s, deafness and Klippel-Fie1 anomaly of spine)

4 Management

Abnormal head posture Unacceptable upshoot or downshoot Squint in primary position

Liberal MR recession (may add LR recession)

“Brown’s syndrome IS an ocular motility disorder.”

“The main problem is pathology of the SO tendon.”

“It can be either congenital or acquired ” I:

Acromegaly Extraocular surgery (RD surgery)

Pathology: short SO tendon, tight trochlea, nodule on SO tendon Acquired

2 Clinical features

Classical triad of

Normal elevation in abduction Defective elevation in adduction (most important) Less severe defective elevation in midline

Vertical gaze triad

V pattern Hypotropia in primary position

Positive forced duction test Downshoot in adduction

No SO overaction (i.e not 10 palsy!)

Additional triad

Widening of palpebral fissure on adduction

3 Management

Correct amblyopia

Spontaneous recovery common

Indications for surgery

Steroids (oral or injection into trochlear area)

Abnormal head posture

Diplopia in downgaze

SO tenotomy or silicon expander

Squint (hypotropia) in primary position

Muscle sequalae Contraiateral SR overaction lpsilateral SO overaction

TOPIC 7 STRABISMUS SURGERY

I MCQ:

“In general, the indications of squint surgeries are ”

Indications of s q u i n t surgeries

1

2 Functional

Anatomical (largely a “cosmetic” indication)

Correct abnormal head posture

Treat diplopia and confusion

Correct misalignment (large angle, increase frequency of breakdown if intermittent)

Restore BSV (if child is young enough)

“The principles of squint surgeries are . ”

Principles o f squint surgeries

1

2

3

Recess or resect? Recession is more forgiving

MR or LR? If deviation at near > at distance, consider operation on MR If distance > near, consider LR What are the indications of recess - resect operation o n 1 eye?

Amblyopia in 1 eye

Constant squint in 1 eye

Previous surgery in 1 eye

Recess l m m = 2 prism D

Vertical muscle surgery l m m = 3 prism D

Resect l m m = 4 prism D

Recession of MR more effective than LR

4 How much to correct?

H O W d o v o u Derform a recession (resection) oeeration?

“In a simple case of a XT with deviation worse at distance, I would perform a bilateral LR recession.”

Recession operation

1 GA

2 U-shaped fornix-based conjunctival peritomy

3 Isolate LR

Dissect Tenon’s on either side of LR muscle with Weskott scissors

Isolate LR muscle with squint hook

Clear off fascia1 sheath and ligaments with sponge

Spread muscle using Stevens hook

4 Stitch 2 ends of muscle with 610 vicryl

1 partial and 2 full thickness bites dividing muscle into 3 parts

Clamp suture ends with bulldog

For resection, measured distance to resect from insertion

5

6 Measure distance of recession

7 Resuturing of LR

Cut muscle just anterior to stitches (for resection, cut muscle at the desired site)

Diathermise point of insertion to create ridge

Stitch each end of the muscle to sclera OR stitch to insertion stump using a hangback technique For resection, stitch end to insertion stump

8 Close conjunctiva with 8/0 vicryl

"In general, it is indicated in adult squints when a precise outcome is needed "

Adjustable squint surgeries

1 Indications

Adult squints

Best for rectus muscles Best with recession (principle: recess more than necessary and adjust postoperatively) Vertical squints

Thyroid eye disease

Blow out fractures

"The complications can be divided into intraoperative,

early and late postoperative complications I '

"The most dangerous intraoperative complications are

scleral perforation and malignant hyperthermia."

at the apex Slipped muscle

Slip within muscle capsule Prevented by adequate suture

Management similar to lost placement

muscle

N O E S

"How do you manage a lost muscle?"

Stop operation (do not frantically dig around) Microscopic exploration (look for suture ends within Tenon's)

Irrigate with saline and adrenaline (Tenon's usually appears more white)

Watch for oculocardiac reflex when struc- tures are pulled

If muscle cannot be found, abandon search Postoperatively, can try CT scan localization May consider reoperationlrnuscle transposi- tion surgery

Section 9: Squints and Pediatric Eye Diseases 393

Scleral perforation

Management

Thinnest part of sclera (< 0.3mm just posterior to insertion) Potential sequalae: RD, endopthalmitis, vitreous hemorrhage Usually end up with chorioretinal scar

Refer to retinal surgeon

Stop operation and examine fundus Consider cryotherapy at site of scar

2 Early postoperative (“A) . .

Alignment

Most common complication Under- or over-correction Late misalignment caused by scarring, poor fusion, poor vision, altered accommodation

Operate on 3 or more recti

Tenon’s capsule is violated

Anterior segment ischemia

Adherance syndrome

Allergic reaction

Infection

Mild conjunctivitis Preseptal cellulites/orbital cellulites Endophthalmitis (missed perforation)

3 Late postoperative ( “ D )

Diplopia

Scenarios Can be early or late

Prisms Diplopia awareness Reoperation (adjustable surgery)

In children, diplopia resolves because of new suppression scotoma or of fusion

In adults, diplopia usually persists if squint is acquired after 10 years of age Management

Droopy lids (ptosis)

Dellen and conjunctival cysts

HO W d o YOU m a n a q e m a l i g n a n t hvperthermia?

“Malignant hyperthermia is a medical emergency and requires immediate

recognition and management.”

Malignant hyperthermia

1 Mechanism of action

Acute metabolic condition characterized by extreme heat production

Inhalation anesthetics (e.g halothane) and muscle relaxants (succinlycholine) trigger following chain of events

Increase free intracellular calcium Excess calcium binding to skeletal muscles initiates and maintains contraction Muscle contraction leads to anerobic metabolism, metabolic acidosis, lactate accumulation, heat production and cell breakdown

2 Clinical features

More common in children

Early signs

Isolated case or family history (AD inheritance)

Tachycardia is earliest sign Unstable BP

Tachypnea Cyanosis

Dark urine Trismus Elevated carbon dioxide levels Electrolyte imbalance Renal failure Cardiac failure and arrest Disseminated intravascular coagulation

3 Management

Hyperventilate with 100% oxygen

Muscle relaxant (dantrolene)

Iced lavage of stomach, bladder, rectum Surface cool with ice blanket

Treat complications

Te/Le a b o u t botulinum t o x i n

“Botulinum toxin or botox is a toxin used for chemodenervation.”

“The mechanism is believed to be ”

“The indications in ophthalmology include either squint or lid disorders ”

Essential blepharospasm Hemifacial spasm

Purified botulinum toxin A from Clostridium botulinum

Permanent blockage of acetylcholine release from nerve terminals

After injection, botox bound and internalized within 24-48 hours

Paralysis of muscle within 48-72 hours

Recovery by sprouting of new nerve terminals, paralysis recovers in 2 (squint) to 3 months (lid)

2 Indications

VI CN palsy (weakening of antagonistic MR to prevent contracture)

Assess possibility of postoperative diplopia before squint operation in adults

Lid disorders

3 Complications

Intraoperative

Scleral perforation Retrobulbar hemorrhage

Temporary ptosis (common) Vertical squints

Diplopia Mydriasis Postoperative

TOPIC 8 RETINOBLASTOMA

O p e n i n g q , e s t i o n NO I: Tell me about retinoblastoma (RBI

"RB is a tumor of the primative retinal cells."

RB is most common primary, malignant, intraocular tumor of childhood

8Ih most common childhood cancer

2nd most common intraocular tumor (after choroidal melanoma)

Incidence is 1 in 20,000 births (range 1 in 14,000 to 1 in 34,000)

No sexual or racial variation

Maps to chromosome 13 q14 (13 associated with bad luck)

Produces RB protein (pRB) that binds various cellular proteins to suppress cell growth

RB1 is a recessive oncogene at cellular level

Mutations of RB1 alleles result in cancer only in the developing retina; other cell types die by apoptosis in the absence of RB1

Primitive retinal cells disappear within first few years of life so RB is seldom seen after 3 or 4 years of age

2 Knudson's 2 hit hypothesis

Both alleles must be knocked out for tumor to develop

3 Hereditary RB

The patient inherits 1 mutant allele from parents and 1 normal allele which undergoes subsequent new

mutation after conception (one of Knudson's 2 hits occur prior to conception)

40% of RB is hereditary type of RB

The risk of the Knudson's second hitlnew mutation is extremely high (therefore RB is inherited as AD trait with 90% penetrance)

There is risk of bilateral RB (as all cells have inherited 1 mutant allele)

There is risk of nonocular malignancies elsewhere (as all cells have 1 mutant allele)

Age of presentation: 1 year

Both alleles are normal after fertilisation, but 2 or more subsequent spontaneous mutations inactivate both

alleles (both of Knudson's 2 hits occur after conception)

60% of RB is nonhereditarv tvDe of RB

No risk of bilateral RB

4 Nonhereditary RB

No risk of nonocular malignancies elsewhere

Age of presentation: 2 years

25-30% of nonfamilial cases are still hereditary RB (The rate of new mutation

is high) Therefore a negative family history does not rule out hereditary RB

HO Wdo you counsel parents with a c h i l d w i t h RB?

“Risk of RB depends on presence or absence of family history and whether tumor is unilateral or bilateral.”

“If there is a positive family history, the risk to the next child is 40%.”

“If there is no family history, but the tumor is bilateral, the risk to the next child is 6%.”

“If there is no family history and the tumor is unilateral, the risk to the next child is only 1%.”

Genetic c o u n s e l l i n g

Chance of following people to have a baby with RB:

Parent Affected child (patient) Normal sibling

”RB IS a tumor of the primative retinal cells.”

“Pathological it has distinct gross and microscopic features.”

Section 9: Squints and Pediatric Eye Diseases 397

0 Arrangement (Homer Wright rosettes, Flexner Wintersteiner rosettes and fleurettes)

arrangements

Homer Wright Neurobastic differentiation Single row of columnar cells surrounding a central lumen

Central lumen is tangle of neural filaments Can be seen in neuroblastoma and medulloblastoma

Flexner 0 Early retinal differentiation Single row of columnar cells surrounding a central lumen with a

Cilia projects into lumen Central lumen is subretinal space Refractile lining is external limiting membrane Can be seen in retinocytoma and pinealoblastoma

Fleurettes Photoreceptor differentiation Two rows of curvilinear cells

Inner cluster represents rod and cone inner segments Outer cluster represents outer segment

“Retinocytoma can be considered a benign variant of RB.”

“Pathological and genetically it shares many characteristics of RD.”

Retinocytorna

1 Originates from neuroretina

2 Same genetic implications

Arrangement (Flexner Wintersteiner rosettes and fleurettes)

Howdo you manage a patient with retinoblastorna?

“The aims of management of RB are ”

“This depends on a team approach involving ”

“The different modalities available include I ’

“Factors to consider are ”

External beam radiotherapy

Chemotherapy (eg chemoreduction, systemic chemotherapy, subconjunctival chemoreduction, intrathecal cytosine arabinoside)

Focal therapy (eg laser, cryotherapy, radioactive plaque, thermotherapy)

Orbital exenteration

4 Trends

1st goal to save life

2nd goal to save eye

3rd goal to maximise vision

Paediatric oncologist and radiation oncologist

Medical social worker and RB support group

In the past, enucleation was the standard treatment for small tumors within the globe and external beam radiotherapy was the standard for large tumors extending out of globe

Trend towards more conservative treatment for small to medium size tumors

Increasing use of chemotherapy followed by focal therapy for small tumors and plaque radiotherapy for medium size tumors

Tumor size and location

Bilateral or unilateral disease

Visual potential of affected eye

Visual potential of unaffected eye

Associated ocular problems (e.g RD, vitreous hemorrhage, iris neovascularization, secondary glaucoma) Age and general health of child

Personal preferences of parents

5 Factors to consider

6 FOIIOW-UP

Patients with treated RB and siblings at risk need to be followed indefinitely

After initial treatment, re-examine patient 3-6 weeks later

Active tumor on treatment requires follow-up every 3 weeks

If tumor is obliterated, follow-up 6-12 weeks later

Location (most important factor)

3-monthly until 2 years post treatment, then 6 monthly until 6 years of age, then yearly for life

Risk of new RB decreases rapidly after 4 years of age to negligible risk after 7 years of age

Risk of recurrence of treated RB negligible after 2 years of completed treatment (unrelated to patient’s age)

7 Risk of new or recurrent retinoblastoma

8 Prognosis

95% 5 year survival if intraocular tumor

5% 5 year survival with extraocular extension/optic nerve involvement Tumor size and grade

Iris rubeosis

Bilateral tumors (risk of second malignancy)

Age of patient (older worse)

“Enucleation remains the treatment of choice for large tumors.”

“And in eyes with little or no potential vision.”

Section 9: Squints and Pediatric Eye Diseases

Indications f o r enucleation for RB

1 Large unilateral tumor

Massive vitreous seeds

Total retinal detachment

Iris neovascularization

Ciliary body involvment

Large unilateral RB occupying more than 1/2 of globe

Large unilateral RB with no visual potential

2 Associated complications

3 Failure of other treatment

“The indications for chemotherapy in RB are ”

“The current drugs under investigations include ”

Chemoreduction for small and medium size tumors Vitreous/subretinal seeds (isolated local therapy is not good enough)

Tumor cells crossed lamina cribrosdextraocular extension Palliative

VEC (vincristine, etoposide, carboplatin )

VTC (tenoposide instead of etoposide)

Small to medium size tumors, 4-10 disc diameters, < 4mm thick

Larger tumors, vitreous seeds, RD, bone marrow or orbital involvement

4 Response to chemotherapy

80% remission at 3 years

RB tumors frequently become “multi-drug resistant” and regrow after initial response

Related to expression of P-glycoprotein (P170) (note: this is a relatively “hot” topic!)

Increased P170 correlated with therapeutic failure in other tumors (neuroblastoma, rhabdomyo- sarcoma, leukaemia, myeloma, lymphoma)

Considerable shrinkage after 2 cycles

Reduced vascularization or avascular tumor Calcification (cottage-cheese appearance) Disappearance or significant clearance of vitreous seeds Resolution of extensive RD

Unfavorable response to chemotherapy

Little shrinkage or calcification

Unchanged vitreous seeds

Favorable response to chemotherapy

Remains vascular or translucent (fish-flesh appearance)

Te// m e a b o u t s e c o n d cancers in retinoblastoma

“Second cancers are leading causes of death in patients with the hereditary type of RB.”

“The incidence is ‘ I

“The common tumors include , ,”

S e c o n d cancers in RB patients

1 Incidence

2 Type of tumors

Hereditary RB: 6% over lifetime

Hereditary RB with external beam radiotherapy: incidence 1% per year in field of radiation (i.e 30% in 30

years, 50% in 50 years)

Average age of diagnosis: 13 years (note: remember that RB gene is on chromosome 13!)

Osteogenic sarcoma is the most common cancer

Pineoblastoma, ectopic intracanial RB (trilateral RB) is common up to 2 years after diagnosis of RB Beyond 2 years after diagnosis of RB

Neuroblastoma, medulloblastoma, leukaemia

Bony and soft tissue sarcomas (Ewing’s tumor, chondrosarcoma, rhabdomyosarcoma) Skin tumors (malignant melanoma, sebaceous cell CA, squamous cell CA)

“Refers to a classification which relates to VISUAL prognosis (not mortality).”

“Based on size, number, location of tumor and vitreous involvement.”

Multiple, some larger than 10 DD

Massive tumours involving 1/2 of retina

HOW do y o u manage a c h i l d w i t h leukocoria?

“In a child with leuokcoria, the most important diagnosis to exclude

is retinoblastoma.”

“However, the other common diagnoses for leukocoria are ”

“The management involves a complete history, ocular and systemic

examination and appropriate investigations.”

Section 9: Squints and Pediatric Diseases

Toxocara (15%) Congenital cataract

ROP lncontinentia pigmenti CongenitaVdevelopmentaI anomalies

Large coloboma Retinal dysplasia Juvenile retinoschisis Norrie’s disease

Medulloepithelioma Retinal astrocytoma

Preschool (Coat’s, toxocara)

Female (incontinentia pigmenti)

Gestational age (ROP) Maternal health (TORCH syndromes)

Unilateral (RB, PHPV, Coat’s, toxocara and cataract)

Bilateral (RB, ROP, cataract, Norrie’s, incontinentia pigmenti)

Normal size eye and no cataract (RB)

Microophthalmia or concomitant cataract (PHPV)

Acoustically solid tumor with high internal reflectivity (RB)

CTscans

Optic nerve, orbital and CNS involvement (RB) MRI

§ection I 0

MISCELLANEOUS

TOPIC I OCULAR TRAUMA

ocular trauma?

“The ocular manifestations can be divided into orbit, antenor

and posterior segment and neurological manifestation.”

Blunt ocular trauma

1 Orbital fracture

2 Anterior segment

Hyphema

Iris and angles

Traumatic mydriasis, miosis Angle recession, iridodialysis, cyclodialysis

Traumatic cataract (Vossius ring) Lens subluxation

Lens

3 Posterior segment

Vitreous hemorrhage

Commotio retinae

Vitreous base avulsion

Retinal breaks and detachment

Retinal dialysis

Giant retinal tear Macular hole Choroidal rupture

Signs of penetrating ocular trauma

1 Suggestive signs

Deep lid laceration

Conjunctiva

Hemorrhage, laceration Chemosis

lridocorneal adhesion Iris defect

Iris and AC