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Pathological Myopia Presented by: Dr. Mohammad Abdullah Bawtag • SankaraNethralay a– Chennai, India • 2014
Myopia- New Latin …… was derived from the original Greek word “mŭopia” … contracting or closing the eye. - 138–201 Galen was the first to use the term myopia - 1977 Brian J. Curtin Classification scheme for staphyloma PM- 1988 Takashi Tokoro…Definition of pathologic myopia Staphyloma - is a pathognomic feature of PM - 1801 Antonio ScarpaFirst anatomical description of posterior staphyloma, but did not make the link to myopia - 1856 Carl Ferdinand von ArltFirst connected staphyloma and myopic refraction
Pathological myopia Degenerative myopia Malignant myopia High degree myopia Progressive myopia Magna myopia
Clinically- refractive error > -6 D. Duke-Elder - Myopia with degenerative changes especially in the post. segment. Tokoro - Myopia caused by pathological axial elongation. A more specific - Myopic retinopathy, refers to the degeneration of chorioretinal tissue ass. with axial elongation of the eye.
Interesting facts Lengthening of the post. segment of the eye commences only during the period of active growth. The eye and the brain show precocious growth at the age of 4 years; the brain is 84% and the eye 78% and the rest of the body 21%. After this, both the eye and the brain increase slowly while the body grows more rapidly. However, when axial myopia continues to progress, it is interpreted as a precocious growth which has failed to get arrested…………….!!!!!!!!!! We do not as yet know what this influence is.
Etiology of Myopia is as diverse and controversial as one can imagine. Everything in medicine has been blamed as a cause of Myopia. Two types of theories are put forward: 1) Mechanical and Environmental 2) Biological
Mechanical theories - distension of normal sclera - Increased IOP caused by the action of EOMs or IOMs or by insidious chronic glaucoma. Others theories : weakening of the sclera - venous congestion, inflammation or dietary deficiency.
High Myopia is classified in a simple manner as: i) Simple ii) pathological Simple Myopia - not progressive, good vision- optical correction. Pathological Myopia - changesin the posterior segment, lengthening of AP axis of the globe.
Family studies and twin studies have revealed the heritability of myopia since the 1960s. In familial studies and twin studies, linkage analysis using microsatellite markers has identified 19 loci for myopia: MYP1 to MYP19. Common Myopia AD High Myopia AR High Myopia X-Linked High Myopia MYP7 MYP8 MYP9 MYP10 MYP14 MYP17 MYP1 MYP13 MYP2 MYP3 MYP4 MYP5 MYP11 MYP12 MYP15 MYP16 MYP17 MYP19 MYP18
Manifestations of Pathological Myopia Anatomical Manifestations Functional Manifestations Ocular Manifestations
Anatomical Manifestations Corneal astigmatism Tilted disc Deep AC Peripapillary detachment in PM Angle iris processes Temporal crescent or halo atrophy Zonulardehiscences Macular lacquer cracks Vitreous syneresis Pigment epithelial thinning Lattice retinal degeneration Choroidal attenuation Scleral expansion and thinning Fovealretinoschisis ↓ Ocular rigidity Post. staphyloma ↑ AL
Functional Manifestations Image minification Anisometropicamblyopia Subnormal visual acuity Visual field defects Impaired dark adaptation Abnormal color discrimination Suboptimal binocularity
Ocular Manifestations • Strabismus：exophoria／exotropia • Cataract. • Glaucoma.. pigmentary / normal-tension glaucoma • Tigroid, or blond fundus, with choroidal visible underneath • Tilted optic nerve with peripapillary atrophy • Peripapillary detachment • Chororetinal atrophy • PVD • RD • Lacquer cracks • Lattice degeneration (spontaneous breaks in Bruch's membrane) • Cobblestone degeneration • Fuch's spot (RPE hyperplasia in response to CNV) • Scleral thinning • Peripheral retinal holes • Macular holes causing RD • CNV
Complications of Pathological Myopia This review aims to provide an overview on some of the important complications associated with PM. Vitreous degeneration Myopic foveoschisis & Macular hole Peripheral retinal degenerations & RRD CNV in PM Lacquer cracks Post. Staphyloma
Vitreous degeneration • Syneresis • Vitreous liquefaction, fibril aggregation & condensation • Associated with floaters • Caused by myopia, senescence, trauma, inflammations, hereditary causes • PVD
Liquefaction of the vitreous gel Hole in the posterior hyaloid membrane Fluid tru defect into retrohyaloid space Vitreous gel collapses synchytic fluid in space Detachment of posterior vitreous from ILM Acute PVD
PVD with gel collapse • Without vitreous hage, 4% develop retinal breaks • With vitreous hage, 20% develop breaks • PVD without gel collapse • Associated with future retinal hole or vitreous hage • Scaffold for proliferative new vessels
Symptomatic PVD • Approx 10-15 % • Retinal breaks at first • assessment • Approx 90 % • uncomlicated at first • assessment • Low risk • break High risk break • 1.5-3.4% • Retinal breaks • At 4-6 weeks Approx 98 % uncomplicated At 4-6 weeks • Detachment • In 33-46% • Within 6 • weeks • Low risk of • detachment Flow chart illustrating the natural history of an acute PVD
Ultrasound picture showing PVD. Note that the vitreous is still attached at the optic disc and the oraserrata.
Vitreous changes in PM • Vitreous liquefaction • Early PVD Presence of CPVD • Larger posterior precortical vitreous pocket • Residual posterior cortex in CPVD
Myopic Foveoschisis • Prevalence – 9% to 34% • Pathogenesis : 1. Attachment of Contracted vitreous cortex to retinal surface 2. ERM 3. Retinal vascular traction 4. Rigidity of ILM 5. Progression of posterior staphyloma
Natural history: Varied course with diverse visual outcomes- stable to development of macular holes Eyes with anterior traction had worst prognosis Progressive disease with poor outcomes • Treatment: • PPV+ILM peeling(traditional/foveal sparing) +/- tamponade – useful to relieve internal surface anterior traction • Scleral buckling – Addresses disparity between retina and elongated sclera • Suprachoroidal buckling – hyaluronic acid injected through a catheter into suprachoroidal space in the area of staphyloma to indent choroid • Complications: Choroidal hemorrhage and hyperpigmentation around area of indentation.
Macular hole Myopic macular hole may occur, but the exact mechanism is unknown. Whether attenuation of the neural retina and its supportive pigment epithelium and choroid are responsible is speculative.
Various surgical procedures have been performed for macular hole with or without RD and they include : • PPV with gas or silicone oil tamponade • Macular buckling • Scleral shortening surgeries.
Myopic macular chorioretinopathy • DEF: is a rare, genetic eye disorder that causes vision loss. • Grading(shih et al) • MO - Normal post pole • M1 - Tesselation & choroidal pallor • M2 - M1+post staphyloma • M3 - M2+lacker cracks • M4 - M3+ focal deep choroidal atrophy • M5 - M4+geographic atrophy, CNV • M3>- myopic maculopathy
Peripheral retinal degenerations & RRD • “Lattice degeneration is a common retinal degeneration.” • 1. Epidemiology • 8-10% of general population (but 20-40% of RD) • More commonly in moderate myopesand is the most important degeneration directly related to RD • Location: Commonly -temporal superiorly fundus Between equator and oraserrata • 2. Pathology • Discontinuity of internal limiting membrane • Atrophy of inner layers of retina • Overlying pocket of liquefied vitreous • Adherence of vitreous to edge of lattice (posterior edge) • Sclerosis of retinal vessels
Lattice degeneration - predispose to RRD Retinal tears - posterior and lateral margins of the lattice degeneration Role of prophylactic Laser photocoagulation: History of RD in the fellow eye Family history of RD Prior to ocular surgeries Symptomatic pt
In eyes with RD, laser photocoagulation alone is insufficient to treat the condition and V-R surgery is required. Surgical modalities for RRD - pneumatic retinopexy, SB surgery with cryopexy, and PPV+BB+EL+ C3F8/ SIO. CLINICAL PEARLS Lattice degeneration both with and without atrophic holes is generally benign and does not require prophylactic treatment, as the complications of treatment are more severe than the natural history of the untreated condition.
Myopic RD • Incidence of RD in general population range between 0.005 and 0.01 % . • RD occurs far more frequently in patients with myopia. • Disease Case-control study Group found that subjects with sepherical equivalent refractive error of -1 to -3 diopters had a fourfold greater risk of RD then a nonmyopic individual. • For refractive errors greater than -3 diopters the risk was tenfold greater • More than half of nontraumatic RRD occurs in myopic eyes.
CNV in Pathological Myopia Among various lesions associated with high myopia, macular CNV is one of the most vision threatening complications. It develops in around 5 to 10% of eyes with high myopia and is the commonest cause of CNV in young individuals and accounts for around 60% of CNV in young patients aged 50 years or younger. Macular hage ass. with CNV in high myopia
Develops from laquer cracks. • Smaller, less exudation. • - Type 1 (severe myopic degeneration)- Leakage does not extend beyond initial CNVM border- Quiescent scar. • - Type2( Minimal degeneration)- Leakage beyond CNVM borders- Fibrovascular scarring.
The mechanism of CNV formation in myopic CNV is still unclear. • A possible explanation includes, certainly, the induced hypoxia in the outer retina, which is a large source of VEGF secretion. Chorioretinal stretching, lacquer crack formation, choroidal thinning, choroidal flow disturbance with reduced flow, choroidal filling delay, RPE and overlying retina atrophy, loss of photoreceptors, all of them can be involved in growth factor release and myopic CNV formation. The role of each of these features and the interconnections between them remain unclear
Treatment of myopic CNV More recently, the use of anti-VEGF agents The most commonly used currently is PDT with verteporfin. A combination therapy of PDT with anti-VEGF agents appears efficacious in the treatment of eyes with CNV secondary to pathological myopia, and may afford better visual outcomes as compared to PDT monotherapy • Laser photocoagulation of …. no longer performed. • Other treatment modalities • Submacular surgery • Macular translocation surgery
Features of choroid in PM • Stretched choroid without additional vasculature • Thinner choroid • Choriocapillaries and larger ch.vessel have decreased lumen • Choriocapillaries have loss of fenestrations • Increased number of vortex veins(>4) • Posterior vortex veins(ciliovaginal veins) • Reduction of choroidal thickness is proportional to age and refractive status • Per diopter myopia caused 8µm reduction in choroidal thickness • Per decade causing 12-15µm reduction in choroidal thickness • Intrachoroidalcavitation – the expansion of distance between inner wall of sclera and posterior surface of bruch’s membrane • Attenuated choroid to absent choroid – myopic chorioretinal atrophy
Lacquer cracks Spontaneous ruptures in the Bruch's membrane . Small hages may develop within the lacquer cracks. Lacquer cracks predispose - macular CNV Small ingrowth of fibrovascular tissue may also give rise to small elevated pigmented circular lesions and are known as Fuchs‘ spots.
