CBS: Block III, Module 1, Case 1 Special Senses PDF

CBS: BLOCK III, MODULE 1, CASE 1 SPECIAL SENSES ANATOMY, EMBRYOLOGY AND PHYSIOLOGY IN Within the optic nerve the artery divides into superior and RELATION TO THE DEVELOPMENT AND PROGRESSION inferior papillary branches, and loses...

CBS: BLOCK III, MODULE 1, CASE 1 SPECIAL SENSES ANATOMY, EMBRYOLOGY AND PHYSIOLOGY IN Within the optic nerve the artery divides into superior and RELATION TO THE DEVELOPMENT AND PROGRESSION inferior papillary branches, and loses the muscularis coat. OF RETINOBLASTOMA The vessels within the eye are thus arterioles or capillaries. RETINA The papillary branches are divided into nasal and The investigation of the lateral optic vesicles in embryonic temporal branches that divided dichotomously to the life forms the double-walled, secondary optic vesicles or capillary level. optic cups. ○ The capillaries do not anastomose. The inner wall forms the light-sensitive sensory retina. Retinal vessels lack nervous control, and their constriction The outer wall thins to a single layer, the retinal pigment and dilation are in response to autoregulation epithelium. (intravascular reisance-pressure and partial pressure of The photopigment molecules located in the disks of the carbon dioxide [PCO2]. rod and cone outer segments absorb light that passes The endothelial cells lining the retinal vessels are not through the transparent inner portion of the sensory retina fenestrated and tightly joined. (inner, nearer the vitreous cavity; outer, near the These vessels provide a portion of the blood-retina barrier, coriocapillaris). which is similar to the blood-brain barrier. Light activates the molecules in the photopigment of the The retinal blood vessels are susceptible to the diseases rods and cones in the retinal outer segments, which as blood vessels elsewhere in the body, but because their initiates a cascade of reactions that are covered to graded intravascular pressure must exceed the intraocular electrical potentials. pressure to prevent collapse, they form a highly ○ These potentials are modulated and amplified by specialized vascular bed without counterpart elsewhere. bipolar, horizontal and amacrine cells. Retinal veins follow a course similar to that of the arteries The axons of ganglion cells transmit the graded potentials but do not parallel them exactly. to the lateral geniculate body as spike discharges. Generally the diameter of an artery is about two thirds to The rod and cone disks of the outer segments of the three quarters that of the corresponding vein. sensory retina are enmeshed in the microvilli of the retinal ○ The veins do not anastomose. pigment epithelium. At their crossings the arterioles and veins share a The disks of the outer segments are continuously common adventitial sheath, a factor in the genesis of renewed by their cell bodies, and clumps of the oldest venous sclerosis at arteriovenous crossing disks are phagocytized by the retinal pigment epithelium. ○ If this phagocytosis stops, the sensory retina OPTIC NERVE degenerates. The sensory retina may be divided into a central portion The optic nerve is a portion of a white fiber tract of the (macula) which contains the fovea centralis that functions CNS that consists of axons of retinal ganglion cells. in photopic vision, and into four peripheral quadrants that It extends from the optic disk at a level with the retina function in spatian orientation and in reduced light within the eye to the optic chiasm, where in normal (scotopic visions). humans, half of fibers decussate to the opposite side of The central retina, the macula, located between the brain in the optic chiasm. superior and inferior temporal vessels, extends Thereafter, crossed nasal fibers and uncrossed temporal temporarily from the optic disk to about 2 disk diameters fibers constitute the optic tract. lateral to the fovea centralis. The optic nerve is divided into four portions: It contains the Fovea centralis, a pit in the retina in which ○ (1) Introcular – 1 mm; the innermost layers of the sensory retina are displaced ○ (2) Orbital – 30 mm; so that light falls directly upon the cone photoreceptors ○ (3) Intracanalicular – 4-10 mm; without traversing the inner (retinal) layers. ○ (4) Intracranial – 10 mm. The faveola at the center of the fovea centralis contains The intraocular portion of the optic nerve includes the only cone. optic disk and the portion of the optic nerve within the ○ The clinical and anatomic names for these areas are posterior scleral foramen. sometimes used interchangeably. The optic disk is located at a 3 mm nasal to and about 0.8 The fovea centralis functions in bright illumination mm above the foveola. (photopic vision), form vision, and color vision. ○ It is composed of axons of ganglion cells. Rod photoreceptors are most common in the peripheral The choroid and all layers of the retina, except the nerve quadrants and function in dim illumination (scotopic fiber layer, terminate at optic disk margin. vision). ○ Because the photosensitive rods and codes are Blood Supply to the retina in humans is derived from two absent, this area is blind (the blind spot of Mariotte in sources: visual field testing). ○ Choriocapillaris, which nurtures the retinal pigment The optic nerve exits from the eye through the posterior epithelium and the outer portion of the sensory retina scleral foramen bridged with the lamina cribrosa that is adjacent to the choroid; and formed by fibrous tissue from the sclera, elastic tissue of ○ Branches of the central retinal artery which supply the choroid and Bruch membrane, and astroglia derived the inner half of the retina. from the septal system of the nerve. The border between the retinal and choroidal blood supply Posterior to the optic disk the nerve fibers are myelinated. is at the junction of the outer ine third and the middle one The portion of the optic nerve visible within the eye is third of the outer plexiform layer of the retina. about 1.5 mm in diameter (The optic disk is not elevated Normal retinal function requires both systems. above the surrounding retina and the term “optic papilla” is The central retinal artery is the first branch of the a misnomer. ophthalmic artery within the orbit. Nonetheless, the central retinal artery divides into It is a medium-sized artery, 0.20 to 0.30 mm in diameter, papillary branches. The fundus surrounding the disk is which has well-developed intimal, muscularis and called peripapillary, and edema of the disk is papilledema). adventitial layers. The orbital portion of the optic nerve has an S-shaped Within the optic nerve the adventitial layer is augmented curve to permit movements of the eye. by a pia meter. It is sheathed with a dense outer dura mater, a middle The artery enters the eye through the lamina cribrosa and arachnoid mater and an innermost pia mater. ascends the nasal portion of the optic cup in company These extend from the optic foramen to the globe, where with the central retinal vein that is located temporally. the dura mater and arachnoid sheaths blend into the sclera. 1  Near the globe the long and short ciliary arteries and OPTIC TRACT nerves are arranged about its circumference. The optic tract extends from the chiasm to the lateral The central retinal artery and vein penetrate the optic geniculate body. nerve 12 mm behind the globe. It is composed of axons from ganglion cells of the nasal At the apex of the orbit, the optic nerve is surrounded by retina of the opposite side and the temporal retina on the the tendinous origin of the recti muscles, the ligament of same side. Zinn. These axons sweep laterally, encircle the hypothalamus In its intracanalicular portion, the optic nerve passes posteriorly (in the ventral wall of the third ventricle), and through the optic foramen together with the ophthalmic wind around the ventrolateral aspect of the pes pedunculi artery and the sympathetic nerves accompany this artery. (the ventral portion of the midbrain). At the anterior margin of the optic foramen the dura mater The majority of axons terminate in the lateral geniculate covering the nerve divides so that one portion continues body. as the periosteum of the orbit and the other continues as A smaller number continue in the superior quadrigeminal the dural sheath of the optic nerve. brachium to the superior colliculi (reflex ocular Within the optic canal, the dura mater is adherent to bone, movements) and to the pretectal area (pupillary reflexes). arachnoid, and pia mater so that the nerve is firmly fixed. Other fibers enter the hypothalamus and terminate in the The intracranial portion of the optic nerve passes medially supraoptic nucleus and the medial nuclei of the tuber to form the chiasm. cinereum. The significance and extent of this distribution in humans STRUCTURE is not known. The optic nerve contains between 1.1 and 1.3 million The superior colliculi are sensitive to moving visual stimuli afferent axons of ganglion cells subserving vision, and may direct the eyes and the head toward a visual pupillary reflex and ocular movements. stimulus. Axons from the ganglion cells of the fovea centralis may provide up to 90% of the axons of the optic nerve. LATERAL GENICULATE BODY The nerve is composed of bundles of nerve fibers The axons of retinal ganglion cells that carry visual separated by septa that are continuous with the pia mater impulses synapse in the lateral geniculate body. and carry minute blood vessels to the nerve. This is located in the diencephalon lateral to the medial As in the brain nerve fibers are supported by astroglia and geniculate body and consists of a dorsal and oligodendroglia derived from the neural ectoderm and by inconspicuous (in humans) ventral nucleus. mesenchymal microglia that have a phagocytic function. In primates the dorsal nucleus is composed of six cellular Myelinization of the optic nerve begins at the chiasm at layers, numbered 1 to 6, beginning at the hilus and about the twenty-fourth week of fetal life and, at birth has continuing toward the dorsal portion of the nucleus. reached a point just behind the lamina cribrosa. Cells in the ventral layers 1 and 2 (magnocellular laminae) Oligodendrocytes are associated with the synthesis of are larger and more uniform in size and shape than cells metabolism of myelin; these cells are more numerous in the remaining four layers (parvocellular laminae). behind the lamina cribosa. Axons from the temporal retina (uncrossed) on the same Astrocytes provide a skeletal framework on the intraocular side synapse in layers 2,3 and 5. surface of the optic nerve and are important in providing Axons from the nasal one half of the retina of the opposite mechanical support as nerve fibers make the right angle eye decussate in the chiasm and terminate in layers 1,4, turn from the retina. and 6. The axons from the lower one half of the retina synapse in BLOOD SUPPLY the lateral portion of the lateral geniculate body; those The blood supply of the optic nerve is derived from from the upper one half in the medial portion. several sources. Foveal axons are located posteriorly. The intraocular portion is supplied by the short posterior Central visual fibers are represented in all six layers, ciliary arteries that as they penetrate the sclera, give off whereas peripheral axons are represented in the two branches to form the anastomic partial circle of magnocellular layers and in two paracellular layers. Haller-Zinn. In addition to visual fibers, the lateral geniculate body The central retinal artery does not furnish branches to the receives input from the visual cortex, oculomotor centers optic nerve in this region. in the brain stem, and from the brain stem reticular Much attention has been focused on the blood supply to formation. this area because of involvement of the optic disk in The lateral geniculate body modulates the strength and glaucoma. the pattern of the retinal input and may play a fundamental The intraorbital portion of the nerve has peripheral and role in color vision stereoscopic vision. possibly an axial blood supply. The peripheral vessels originate from those of the pia OPTIC RADIATION mater and are derived form the neighboring blood vessels. The optic radiation (geniculocalcarine tract) extends from The axial vessels are derived from the central retinal the lateral geniculate body to the superior and inferior lips artery, a branch of the ophthalmic artery. of the calcarine fissure (area striata;area 17) of the The axial vascular systems nurtures the central retinal occipital lobe. fibers. Axons from cell located in the lateral aspect of the lateral The intracanalicular and intracranial portions of the optic geniculate body representing the inferior retinal quadrants nerve are nurtured by the pial fibrovascular meshwork (superior visual field quadrants) pass anteriorly around the from branches of the internal carotid artery. tip of the temporal horn of the lateral ventricle to form the temporal loop of Fiechsig-Archmabault-Meyer. OPTIC CHIASM Damage to the axons in this loop, produces superior The optic chiasm is about 13mm wide. homonymous quadrantic fields defects. It is attached by the pia mater and the arachnoid to the The axons of the temporal loop continue posterior to dorsal surface of the diencephalon and it forms a portion terminate in the ventral (inferior) lip of the calcarine of the floor of the third ventricle. fissure. Its posterior surface is in close contact with the tuber Axons from cells located in the medial portion of the cinereum from which extends the infundibulum or stalk of lateral geniculate body, representing the superior retinal the pituitary gland (hypophysis cerebri). quadrants (inferior visual field quadrants), pass nearly The chiasm is superior to the tuberculum sellae turcicae directly posterior through the parietal lobe to terminate in and the diaphragm sellae and is usually posterior to the the dorsal (superior) lip of the calcarine fissure. optic groove of the sphenoid bone. It is closely related to the internal carotid arteries laterally and to the anterior cerebral arteries and anterior communicating artery anteriorly. 2 VISUAL CORTEX ○ Middle vessel layer (of Sattler), which consists of The axons of cells located in the lateral geniculate body medium-sized veins and some arterioles and which terminate along the superior and inferior lips of the contains a loose, collagenous stroma with numerous calcarine fissure. elastic fibers, fibroblasts and melanocytes; This areas is often called the striate cortex (area 17 of ○ Choriocapillaris, which consists of large fenestrated Brodmann) because of the prominent bad of capillaries that form a dense, flat network extending geniculocalcarine fibers (striae of Gennari). from the optic disk to the ora serrate. The upper one half of each retina is represented on the The choriocapillaris has a distinct lobular structure with a dorsal (superior) part of each occipital cortex, the lower feeding arteriole in the center and draining venules at the one half covers the ventral (inferior part). lobular periphery. Fibers representing the central retina terminate at the tip The lamina basalis choroideae (Brunch membrane) is of the posterior pole and more peripheral portions of the about 7 µm thick and separates the choriocapillaris from retina are represented more anteriorly. the retinal pigment epithelium. The visual cortex is composed of six cell layers typical of It is composed of layers contributed by both the cortex, most axons from the lateral geniculate body choriocapillaris and retinal pigment epithelium. terminate in layer IV (lamina granularis interna of The outer layer, nearest the choroid, is composed of Brodmannn) that is divided (in monkeys) into three major basement membrane of the endothelial cells of the layers. choriocapillaris. Adjacent to this is a fine layer of collagen fibers. OPTIC PATHWAYS Centrally, layer of elastic tissue fibers extends outward to The retina, as discussed previously, is divided into a form the supporting structure of the choriocapillaris. central portion (mainly cones), used in the form vision and The inner (cuticular) layer originates from the retinal color vision, and a peripheral portion (mainly rods) used in pigment epithelium and is composed of collagen fibers dark adaptation and in the detection of movement. surrounded by glycosaminoglycans. In the distribution of nerve impulses in the visual Resting upon this layer is the thin basement membrane of pathways, the retina is divided into four quadrants by the retinal pigment epithelium. horizontal and vertical lines that intersect at the fovea The Brunch Membrane stops abruptly at the optic nerve centralis. as does the retinal pigment epithelium ○ (Note that the fovea centralis and not the optic nerve is the point of division) Thus each retina is divided BLOOD SUPPLY into superior, inferior, temporal and nasal portion, The blood supply of the choroid is derived from the short which in turn may be divided into peripheral and posterior ciliary arteries, the two long posterior ciliary central portions. arteries and the seven anterior ciliary arteries. All axons coming from the nasal half of each retina The short posterior ciliary arteries originate as two or three decussate to the opposite side at the chiasm end join branches of the ophthalmic artery. uncrossed temporal fibers to form the optic tract. ○ These branches subdivide into 10 to 20 branches Visual axons synapse in the lateral geniculate body and that perforate the sclera around the circumference of then pas to the optic radiation as the geniculocalcarine the optic nerve. tract. ○ The majority pass at once into the choroid and communicate directly with the choriocapillaris layer. THE CHOROID The two long posterior ciliary arteries perforate the sclera just medial and lateral to the optic nerve. The choroid is the vascular sheet that provides the blood ○ They extend forward in the suprachoroidal space on supply for the retinal pigment epithelium and the outer the medial and lateral sides of the globe to the ciliary one-half of the sensory retina adjacent to it. body. It is composed of an inner layer of fenestrated, ○ There each divides into two branches that extend large-diameter capillaries (21 µm), the choriocapillaris, circumferentially to form the major arterial circle of and successively larger collecting veins approximately the iris that is located in the ciliary body. arranged in layers. ○ Branches extend anteriorly to the iris. The choroid extends from the optic nerve posteriorly to the Recurrent choroidal branches extend posteriorly to ciliary body anteriorly. terminate in the choriocapillaris. It is thickest (0.25 mm) at the posterior pole and gradually The anterior ciliary arteries are the terminal branches of thins anteriorly (0.10 mm). the two muscular arteries of each rectus muscle (except It is attached firmly to the sclera in the region of the optic the lateral rectus muscle), which has but one muscular nerve where the posterior ciliary arteries enter the eye and artery). at the points of exit of the vertex veins. The anterior ciliary arteries bifurcate into vessels that penetrate the sclera and nonpentrating vessels that STRUCTURE extend toward the cornea. The three layers of blood vessels of the choroid have The penetrating vessels provide the blood supply to the supporting structures on other side: ciliary body and send recurrent branches to the anterior ○ the suprachoroid (lamina fusca) on the outer side extremity of the choriocapillaris and to the major arterial and circle of the iris. ○ the basal lamina (Brunch membrane) on the inner The nonpenetrating vessels extend forward in the side. episclera as anterior conjunctival arteries, anastomose ○ The outermost layer, the suprachoroid (lamina fusca) with posterior conjunctival arteries, and terminate in the is made up of lamellae composed of elastic and superficial (conjunctival) and deep (episcleral) pericorneal collagenous fibers to form a syncytium that is dense plexus. posteriorly and becomes looser anteriorly. Venous blood from the choroid, ciliary body, and iris is Melanocytes (fibroblast that contain pigment are abundant collected by a series of veins of increasingly larger in this layer and decrease in number in the vascular diameter layers. These lead to four or more large vortex veins located Found in this layer are smooth muscle fibers, fibroblasts, behind the equator of the globe. endothelial cells, long and short posterior ciliary arteries The vortex veins empty into the superior and inferior and veins. ophthalmic veins, each of which drains into the cavernous The short posterior ciliary arteries have but a short course sinus. in the suprachoroid and extend directly to the choriocapillaris layer. NERVE SUPPLY The blood vessel layer has three components: The choroid is innervated mainly by sympathetic nerves ○ Outer (nearest the sclera) vessel layer (of Haller), that pass through the ciliary ganglion without synapses which consists of large veins that lead to the vortex and are distributed through the short ciliary nerves. veins and have no valves; 3  As they enter the suprachoroid, they lose their myelin into the infraorbital foramen through which the artery and sheath and branch repeatedly to form a plexus. nerve emerge on the face. There are many adrenergcis vesicles, and nerve endings The medial wall is quadrilateral. It is formed mainly by the contact pigment cells and smooth muscles in the walls of orbital plate of the ethmoid bone, but it has sutures arterioles. anteriorly with the lacrimal bone and posteriorly with the body of the sphenoid bone. The lamina papyracea of the ethmoid bone is extremely ORBIT thin, and the sinus may rupture into the orbit when The eyes rest in the anterior portion of two bony cavities, inflamed or when fractured and allow air to enter the orbit. the orbit, located on either side of the nose. Although each In the anterior portion of the orbit, the fossa of the lacrimal orbit appears to be positioned directly forward, only the sac is located between the anterior lacrimal chest of the medial walls are parallel, and the lateral walls diverge at frontal process of the maxilla and the posterior lacrimal an angle of about 45 degrees. crest of the lacrimal bone. The posterior openings of each orbit, the optic foramen The lacrimal sac occupies this fossa and extends and the superior orbital fissure, are located medial to the downward through the nasal lacrimal duct into the nose. eye, so that the optic nerve, blood vessels, and ocular The two leaves of the medial canthal ligament insert into muscles must pass laterally, a factor in ocular rotations. the anterior and posterior lacrimal crests. The anterior two thirds of the orbit are roughly the shape The posterior portion of the medial wall of the orbit of a truncated quadrilateral pyramid with a base of about formed by the body of the sphenoid bone contains the 35 to 40 mm. The posterior third narrows to the shape of a optic foramen. triangular pyramid. The adult orbit usually considered to be approximately 40 mm in height, width and depth, and its volume is about 29 EPIDEMIOLOGY OF RETINOBLASTOMA mL. AGE STRUCTURE GENDER The anterior margin of the orbit is thickened and provides Retinoblastoma is the most common, primary, malignant, protections for the eye. intraocular tumor of childhood, and the second most The zygomatic bone and the zygomatic process of the common of all age groups. frontal bond from the sturdy lateral margin. Still it is rare (incidence 1/20,000 births). There is no The superior margin is formed entirely by the frontal bone. sexual or racial predilection. The medial angular process of the frontal bone and the Average age at diagnosis is 18 months. frontal process of the maxilla form the medial margin, One of three cases is bilateral (simultaneous or which is poorly defined because of the fossa for the consecutive) lacrimal sac. The inferior margin is formed by the zygoma and the body INHERITANCE PATTERNS of the maxilla. Each wall of the orbit, except the medial, is approximately Familial cases are autosomal dominant with a 90-95% triangular with the base directed forward. penetrance and 50% risk of transmission to progeny; Two bones form the lateral wall: however, less than 10% have a positive family history. ○ the Zygoma anteriorly and Familial cases have an early onset, usually bilateral ○ the greater wing of the sphenoid posteriorly. involvement, and are predisposed to develop second The zygomatic portion of the lateral wall is composed of non-ocular malignancies including pinealoblastoma dense bone that separates the orbit from the fossa of the (trilateral retinoblastoma) and osteogenic sarcoma. temporalis muscle. The tumor suppressor gene (RPE1) that predisposes to The lateral orbital tubercle is situated on the anterior retinoblastoma is on the long arm of chromomose 13 margin of the lateral wall. (chromosomal band 13q14) To it is attached the aponeurosis of the levator palpebrae Sporadic cases are more common (60%) and may be superioris muscle, the suspensory ligament of the globe bilateral or unilateral. (ligament of Lockwood), the check ligament of the lateral Bilateral non-familial cases are similar to familial cases in rectus muscle, and the lateral palpebral ligament. both clinical findings and risk for non-ocular malignancies. The greater wing of the sphenoid bone forms the posterior two thirds of the lateral wall. NATURAL DISEASE COURSE This posterior portion is extremely thin, and it separates OCULAR MANIFESTATIONS AND COMPLICATIONS OF the orbit from the temporal lobe of the brain. RETINOBLASTOMA The roof of the orbit is mainly formed by the orbital plate of the frontal bone. Mass effect The lesser wing of the sphenoid bone contributes slightly ○ Endophytic tumors project from the retina into the to the apex. vitreous cavity, appearing as a white cottage Laterally, the orbital roof is adjacent to the zygoma cheese-like mass with surface blood vessels anteriorly and to the greater wing of the sphenoid ○ Exophytic tumors grow in the subretinal space and posteriorly. give rise to retinal detachment, these may be difficult The fossa for the lacrimal gland is located in its anterior to visualize if there is significant subretinal fluid. lateral portion. Retinal detachment Medially, the roof is adjacent to the lacrimal bone ○ More commonly associated with exophytic tumors. anteriorly and the ethmoid bone posteriorly. Secondary glaucoma Medially, near the anterior margin is the trochlea, a fibrous ○ a rare result of congestion or infiltration of the tissue that forms a pulley for the tendon of the superior trabecular meshwork by inflammatory or malignant oblique muscle. cells, neovascularization of the anterior chamber Immediately above the orbital roof is the frontal sinus angle, or angle closure from the mass effect of a anteriorly and the frontal lobe posteriorly. large tumor behind the iris. The orbital floor does not extend to the apex. Leukocoria The floor is formed mainly by the orbital plate of the ○ the most common presentation (60-70%). This is a maxilla. white pupillary reflex. Leukocoria from cataract The orbital surface of the zygoma extends laterally, and formation is rare. the orbital process of the palatine bone extends medially. Hyphema Posteriorly, the infraorbital sulcus extends across the floor ○ a sign of neovascularization of the iris or anterior of the orbit from the intraorbital fissure. It contains the chamber angles infraorbital artery and maxillary nerve. At about its Strabismus midpoint, the sulcus becomes a canal that opens into the ○ the second most common presentation (20-30%). This is more commonly caused by poor vision in the 4  affected eye, and rarely by extraocular involvement 7Exenteration, or the surgical removal of the entire orbital of extraocular muscles or their nerves. contents, is warranted as a debulking procedure for orbital Ocular inflammation metastasis, often in combination with chemotherapy, and ○ presenting as a red, painful eye (pseudouveitis sometimes followed by external beam radiation therapy. and/or pseudohypopyon) is rare; however, Radiation may be applied to the eye via plaque therapy (a retinoblastoma should be included in the differential form of brachytherapy), thereby concentrating and limiting for chronic ocular inflammation in children. the area of exposure to the tumor area. This is done for ○ Orbital inflammation similar to orbital cellulitis is small tumors in order to preserve the normal gross ocular common in advanced cases with extraocular spread, anatomy. Infection, radiation retinopathy and/or optic but it does not necessarily imply extraocular neuropathy are possible complications. External beam extension, such as with necrotic tumors radiation is used for orbital spread but is generally avoided Metastasis due to the risk of cosmetic deformity, cataract formation, ○ Orbital metastasis is due to direct tumor extension and radiation retinopathy and/or neuropathy. ○ Extra-orbital metastasis to regional lymph nodes or Chemotherapy is indicated for advanced intraocular brain occurs when early signs and symptoms are tumors and for metastatic tumors. It is often initiated to ignored or neglected. shrink tumor size prior to surgical or radiation treatment. Non-metastatic tumors Drugs used are carboplatin, vincristine, and etoposide. ○ “Trilateral retinoblastoma” is a second non-ocular malignancy of the pineal gland (pinealoblastoma) THE STAGING AND THE VISUL AND SYSTEMIC associated with familial cases of retinoblastoma. PROGNOSIS FOR PATIENTS WITH RETINOBLASTOMA ○ Up to 90% of retinoblastoma survivors are estimated to be at risk for osteosarcoma and other tumors. INTERNATIONAL STAGING OF RETINOBLASTOMA ○ Secondary tumors may also develop after radiation The Reese Ellsworth Classification was devised in the treatment. 1950s to predict survival of the eye with retinoblastoma, not patient survival. At that time, external beam radiation was the only widely available conservative modality to EXAMINATION TECHIQUES AND UNDERLYING PRINCIPLES IN A SUSPECTED RETINOBLASTOMA save the eye. PATIENT ○ Group 1 (very favorable for saving [or preserving] the eye) Determine if visual acuity is normal or decreased. Visual 1A: solitary tumor, smaller than 4 disc potential will be a major factor in deciding the modes of diameters (DD), at or behind the equator treatment 1B: multiple tumors, none over 4 DD, all at or External eye exam can show ocular congestion, behind the equator leukocoria, a sluggish pupil reaction, a relative afferent ○ Group 2 (favorable for saving [or preserving] the eye) papillary defect, proptosis, ptosis, or blood or tumor in the 2A: solitary tumor, 4 - 10 DD, at or behind the anterior chamber equator Motility exam may reveal full extraocular movements in a 2B: multiple tumors, 4 - 10 DD, and all at or patient with sensory strabismus or limited ocular motility behind the equator with extraocular tumor spread ○ Group 3 (doubtful for saving [or preserving] the eye) Tonometry can show raised intraocular pressure 3A: any tumor anterior to the equator Funduscopy can reveal an intraocular retinal mass, retinal 3B: solitary tumor, larger than 10 DD, behind detachment, and vitreitis. the equator ○ Group 4 (unfavorable for saving [or preserving] the COMMON DIFFERENTIAL DIAGNOSES FOR eye) RETINOBLASTOMA 4A: multiple tumors, some larger than 10 DD Cataract 4B: any tumor extending to the ora serrata Coat’s disease (front edge of the retina) Persistent hyperplastic primary vitreous (PHPV) ○ Group 5 (very unfavorable for saving [or preserving] Accommodative the eye) Esotropia 5A: massive tumors involving more than half of Congenital/developmental glaucoma the retina Uveitis 5B: vitreous seeding (spread of tumors into the Orbital cellulitis jelly-like material that fills the eye) ○ If the fundus cannot be adequately examined, The international (ABC) Classification is a more recent ancillary procedures can help rule out classification that has gained wide use with the advent of retinoblastoma. newer conservative treatment modalities; however, it also does not predict patient survival. ANCILLARY DIAGNOSTIC PROCEDURES AND THEIR ○ Group A EXPECTED FINDINGS Small tumors confined to the retina Ultrasound is useful for confirming tumor presence, None larger than 3 mm detecting calcification, and measuring tumor size. None less than 2 disc diameters from the CT Scan is more sensitive than ultrasound for detecting fovea or 1 DD from the optic nerve calcification. It can also detect gross involvement of the No vitreous seeding or retinal detachment optic nerve, orbital and CNS extension and ○ Group B pinealoblastoma tumors confined to the retina MRI does not show calcification, however it is superior to any location CT for imaging the optic nerve and revealing No vitreous seeding pinealoblastoma. No retinal detachment more than 5 mm from tumor base ○ Group C MODALITIES USED IN THE TREATMENT OF Fine diffuse or localized vitreous seeding RETINOBLASTOMA Retinal detachment more than Group B to total Xenon arc laster photocoagulation may be applicable for Retinal detachment small tumors as a globe-saving treatment measure. No vitreous/subretinal “snowballs” or masses Cryotherapy may also be used as a globe-saving ○ Group D treatment measure for small anterior tumors Massive vitreous/subretinal seeding - 7Enucleation involves removal of the globe, while sparing Vitreous or subretinal snowballs/masses - the extraocular orbital contents. It is necessary for large or Retinal detachment more than Group B to total multifocal tumors that are not treatable by more retinal detachment conservative methods. ○ Group E 5  no visual potential, OR presence of at least one: Tumor in ciliary body/anterior segment Neovascular glaucoma Vitreous haemorrhage Phthisical/pre-phthisical eye Hyphema/corneal staining Orbital cellulitis-like presentation Tumor anterior to anterior hyaloid PROGNOSIS FOR SURVIVAL Overall mortality rate is 2-5% but is dependent on early detection and treatment. The best prognosis is seen with small posterior tumors that are well-differentiated with abundant FlexnerWintersteiner rosettes, which are indicative of photoreceptor differentiation. Prognosis is worse for larger tumors, highly undifferentiated tumors, and tumors with optic nerve, choroid, or extrascleral involvement. VISUAL PROGNOSIS When the globe is left intact after tumor treatment, the best visual prognosis is seen with small tumors that have not involved the macula. GENETIC COUNSELING The risk of transmission in familial cases is 50%. Unaffected parents of a child with bilateral retinoblastoma with no family history have a 40% chance of producing another affected child. 6