Conditions Causing Low Vision

1. Conditions Causing Low Vision

2. Learning Objectives Understand pathology of major eye diseases and conditions causing low vision Visual functions affected Progression of disease or condition Medical management Risk factors Understand eye disease/condition�s affect on occupational performance

3. Conditions Causing Low Vision Low vision can result from Anomaly (usually congenital) Disease (inherited or acquired) Injury Conditions can be progressive or stable Affect different visual functions Can be acquired or congenital

4. Conditions Causing Reduction in Central Visual Function Decrease ability to see visual details including color Q: what functional problems would be expected in a person who is unable to see visual detail?

5. Common Refractive Disorders Cause reduced acuity ONLY if left uncorrected Common types Myopia Hyperopia Astigmatism Corrected with lenses or surgery

6. Progressive Myopia Refractive disorder causing low vision Presents with simple myopia Visual acuity progressively decreases Retina thins in vicinity of optic nerve Often experience vascular leakage Causes micro hemorrhages-scotomas Creates central and peripheral loss

7. Corneal Disorders Cornea provides almost 70% of total refractive power of the eye Must remain transparent and smooth to contribute to refraction Any condition that scars, dis-colors or reduces transparency will impair vision

8. Keratoconus Cone like bulge develops causing progressive thinning of cornea Generally progresses 5-10 yrs then stabilizes May cause scarring of cornea Not a common condition but not rare Undetermined etiology Usually shows up at puberty, late teens or middle age

9. Keratoconus continued� Associated with a number of other conditions Down�s syndrome Retinitis pigmentosa Marfan�s syndrome Medical treatment Contact lens (Boston sclera lens) About 10% require corneal transplant

10. Keratitis Results from wide variety of conditions Corneal infection Irritation Inflammation Because each condition is unique, accurate medical dx and tx is essential Initially causes a corneal ulcer Experience extreme pain and photophobia Can cause corneal scar

11. Corneal Transplant Eye banks in major cities collect healthy corneas from donors Probability for rejection is less than any other transplanted organ 95% success rate Will need optical correction even with best surgeon Lenses or contact lenses

12. Absent or Dysfunctional Iris Doesn�t directly cause vision loss but is associated with conditions that do Aniridia Absent or incompletely formed iris Genetic condition Often also has glaucoma and cataracts Coloboma Iris does not form completely or close Choroid may be affected In turn affecting retinal function

13. Lens Related Conditions Dislocated lens Associated with other conditions-Marfan�s Can be caused by trauma to eye Cataract Opacity in the lens Many causes congenital, infection, severe malnutrition Diabetes, trauma, aging

14. Cataract continued�. Can occur in different areas of lens Central and Posterior capsule Have greater effect on central vision Causes distortion, glare, decreased color Cortical (outer) Affects color discrimination Nuclear (central) Acuity improves with dilation Feels that he/she can see better in the dark

15. Cataract continued� Removal of the lens is the primary medical treatment Creates aphakia condition which must be corrected to get needed refraction For adults Intra-ocular lens procedure (IOL) Replace lens with an implant For children Removal is completed very early for congenital cataract (within 2 weeks) to prevent development of amblyopia Unable to to do IOL Replace with lenses or contact lens

16. Vitreous Opacities Clouding of media due to inflammation or trauma Inflammation creates inflammatory debris Trauma causes bleeding into vitreous Diabetic retinopathy can also cause bleeding Usually a temporary condition

17. Retinal Disorders Only a few result in just central vision loss-most cause of a mix of peripheral and central loss

18. Achromatopsia Complete lack of cone function Results in Extreme photophobia (light sensitivity) Nystagmus Reduced visual acuity Retain normal peripheral field Treatment Control of light, magnification

19. Ocular Albinism Hereditary condition Reduced visual acuity from under-development of macula and fovea Severe photophobia Frequently have nystagmus Severe astigmatism Medical treatment: Pinhole contact lenses, bifocals Because have moderate vision loss and a stable condition-often candidates for bioptic driving

20. Retinopathy of Prematurity Initially called retrolental fibroplasia Linked to administration of oxygen to premature infants Pathogenesis Initially ocular blood vessels constrict Followed by vascular dilation and fibrovascular proliferation into vitreous Causes retinal detachment

21. ROP continued Causes varying degrees of vision loss Both central and peripheral Often accompanied by other conditions Glaucoma, cataracts, corneal changes, nystagmus Treatment Early monitoring of high risk infant Cryotherapy to prevent proliferation

22. Degeneration of Macula

23. Macular Diseases Several diseases cause progressive loss of photoreceptor cells in macular/foveal area Create central scotomas Most common form is age related (AMD) There are also inherited forms Stargardts Always creates permanent vision loss but does not lead to blindness

24. Conditions Resulting in Restricted Peripheral Visual Fields Primarily involve damage to optic nerve or rod photoreceptor cells Q: What functional problems would be expected in a person with peripheral field restriction?

25. Retinitis Pigmentosa Inherited disease primarily affects males Pathogenesis Rod cells slowly destroyed and rest of retina atrophies Begins mid periphery (donut like loss) Progresses both centrally and peripherally Estimated 5% decline per year First symptom is night blindness Followed by tunnel vision and eventually blindness

26. Retinitis Pigmentosa cont� Visual function changes Significant sensitivity to light and glare Double vision (from tunnel vision) Cataracts Some forms are combined with hearing loss Usher�s syndrome

27. Retinal Detachment Side effect with many causes High myopia, diabetic retinopathy, trauma Pathogenesis Tear in retina occurs Allows vitreous to leak in behind it Separates retina from choroid If detached too long, tissue will die Peripheral tear can be reattached

28. Retinal Detachment cont�. Central tear is more difficult, more likely to cause vision loss First symptom often flashing light, sometimes sharp pain Treatment Bond retina to the choroid through Diathermy (high frequency current) Cryothermy (freeze bonding) Photocoagulation (laser bonding) All tx causes some scarring and scotoma

29. Optic Nerve Disorders and Diseases Multiple causes Compression lesions (from brain trauma) Vitamin B12 deficiency Alcohol and tobacco poisoning etc. Multiple sclerosis Creates optic atrophy Seen as changes in optic disc Permanent Experience visual field deficit and photophobia

30. Optic Nerve Hypoplasia Congenital malformation Optic nerve fails to develop due to pre-natal insult drug and alcohol abuse are prime causes Varies in degree from mild to severe

31. Hemianopsia and other VFD Result from damage along optic pathway posterior to chiasm Primary cause is brain injury Stroke (especially PCA) Tumor Traumatic brain injury

32. Age Related Visual Impairments Diseases that increase in incidence with age Major cause of vision loss in older adults Account for 90% of referrals for LVR Three primary diseases Age related macular degeneration Diabetic retinopathy Glaucoma

33. Age Related Macular Degeneration (AMD) Disease process attacks retinal cells themselves Two types Wet (exudative) Dry (senile) Both types cause macular scotomas, photophobia, fluctuating vision, slow dark/light adaptation

34. Wet Macular Degeneration Pathogenesis Neovascularization (new vessel growth) process begins due to unknown cause aka choroidal neovascular membrane (CNVM) New vessels are fragile and hemorrhage Blood smothers photoreceptor cells Usually bilateral Can be very aggressive

36. Dry Macular Degeneration Described as a �balding� of the retina Pathogenesis Retinal pigment epithelium cells (RPE) break down Drusen develops on surface of retina Outpouching of membrane separating choroid layer and retina Kills retinal tissue where it occurs Gradual progression-often unilateral Sometimes a precursor to wet type

37. Medical Evaluations Fluorescein angiography Detects bleeding in retina Indocyanine green test (ICG) Better at detecting occult lesions Scanning laser ophthalmoscope Detect scotomas less than 5 degrees Amsler grid Commonly used but shown to be ineffective

38. Medical Treatment of Wet AMD Laser photocoagulation stalls disease process-doesn�t improve vision Photodynamic therapy (PDT) Newest form of photocoagulation Inject Visudyne (photosensitive drug) intravenously Perfuses CNVM CNVM treated with non thermal laser light for 90 sec Activates Visudyne producing active form of O2 that coagulates/reduces growth of new blood vessels Stabilizes condition in 70% of patients Must be repeated 6x over two years to maintain stability

39. Medical Treatment cont� Transpupillary thermal therapy (TTT) Effective in treating occult CNV Infrared diode laser is applied to area of leakage (identified with angiography) Effective in 81% of patients Requires 1-2 treatments over 2yr period

40. Medical Treatment for Dry AMD Prophylactic treatment for age related macular degeneration (PTAMD) Only laser tx available for dry type Attempts to stop transformation to wet type Infrared laser is applied to drusen beneath the retinal layer without damaging healthy retina 48 laser dots placed in 4 concentric circles single treatment 78% effective in treated patients

41. Other Forms of Treatment Vitamins May play a preventative role by reducing damage from oxidation Vitamin E Zinc Lutein Surgical procedures Transplantation Relocation Retinal chip Stem cells

42. Risk Factors Smoking Excessive alcohol consumption Exposure of retina to UV rays Fair skin and light colored eyes High fat diet Heredity (in small percentage)

43. Glaucoma Second leading cause of low vision Pathogenesis Intraocular pressure (IOP)becomes sufficiently high to damage optic nerve Increase in IOP occurs from build up of aqueous humor in anterior chamber Only outlet for pressure is optic disc Builds up pressure along optic nerve and decreases blood flow

45. Glaucoma continued�.. Causes Over-secretion of aqueous by ciliary body Exceeds capacity of trabecular meshwork in Canal of Schlemm Anatomical aberration resulting in narrow angle between iris and cornea preventing efficient drainage of aqueous Scar tissue from inflammatory process or surgery obstructs the drainage of the aqueous

46. Glaucoma continued�. Most common form is chronic open angle Impediment in drainage of aqueous due to microscopic changes in trabecular meshwork Painless condition Starts in peripheral field progressing to pie shaped or arcuate macular field loss Can lead to blindness

47. Medical Treatment Eye drops Reduce production rate of aqueous and facilitate drainage Up to 4 types of drops may be used simultaneously All have side effects Fatigue, gastrointestinal disturbance, altered taste, stinging, burning, blurred vision, itching Strict compliance is necessary

48. Medical Treatment cont�. Argon laser trabeculoplasty (ALT) Can be used early on in place of eye drops but generally not done Creates a series of drainage holes (about 40) in the trabecular meshwork Surgical trabeculectomy Cut out small segment of trabecular meshwork Create external opening to drain fluid Problems with flap scarring over and development of cataract-generally only used as last resort

49. Diabetic Retinopathy Diabetes can cause a variety of eye problems Cataracts, glaucoma, paralytic strabismus, premature presbyopia, fluctuating refractive errors 40% of diabetics have retinopathy after 5 years of onset

50. Background Diabetic Retinopathy Pathogenesis of BDR High glucose destroys pericytes that maintain integrity of blood vessel wall Blood vessels in eyes balloon outward and begin to leak fluid and lipids onto surface of retina in macular area Retinal changes occur �dot and blot� hemorrhages Microaneursyms (outpouching of capillaries) Hard exudates-drusin deposits Macular edema develops Retina becomes increasingly deprived of oxygen

52. Proliferative Diabetic Retinopathy Involves entire eye Pathogenesis Oxygen deprivation leads to neovascularization New blood vessels grow along vitreous using it like a trellis May cover optic disc New blood vessels rupture-bleed into vitreous Blood collects preventing light from passing through or giving reddish tint to vision Following hemorrhage BV contract and scar, eventually pull vitreous away from retina and causing detachment Tractional retinal detachment

54. Medical Treatment Left untreated can cause blindness Leading cause of blindness in adults 24-65 Best treatment is prevention Diabetes Control and Complications Trial published in 1993 Maintain blood glucose levels at 125 Requires strict monitoring 3-4x daily

55. Medical Treatment cont� Once damage occurs, use laser surgery to attempt to stabilize vision to prevent further loss Focal laser treatment (for early BDR) Reduce edema, seal off leaking blood vessels Pan-retinal photocoagulation (for early PDR) Laser a grid pattern over midsection staying away from fovea to kill off O2 deprived retina and stop trigger for neovascularization Patient will lose some para-central vision

56. Medical Treatment cont� Vitrectomy Last resort Performed when there is a lot of blood or debris in vitreous or if vitreous is tugging at retina and threatening to detach it Ophthalmologist removes blood, scar tissue and vitreous Replaces vitreous with clear saline

57. Miscellaneous Conditions

58. Nystagmus Involuntary, rhythmical, repeated movement of one or both eyes Can be horizontal, vertical or torsional Visual acuity is reduced due to poor gaze stability Most persons view objects as stationary Cause is unknown

59. Nystagmus continued� Rarely seen by itself Appears in conjunction with any thing that disrupts foveal vision albinism, cataract, optic atrophy Conditions that affect vestibular system and cerebellum brain injuries May be accompanied by rhythmic head movement in children with congenital form Some persons may be able to achieve null point with head positioning

60. Strabismus and Amblyopia Strabismus in children Eyes are not aligned with one another Creates double vision Can be congenital or acquired Children exercise sensory suppression to eliminate double image CNS shuts down image from one eye Leads to AMBLYOPIA

61. Amblyopia Functional blindness in central field created by sensory suppression Can significantly reduce visual acuity Impairs binocular vision

62. Strabismus Can express itself as a phoria or tropia Phoria Deviation of eye held in check by fusion Expressed only when fixation is blocked But creates visual stress Tropia Observable constant deviation of eye Creates amblyopia

63. Types Esotropia or Esophoria Eye turns inward Cross eyed Exotropia or Exophoria Eye turns outward Wall eyed Hypotropia or Hypophoria Eye turns down Hypertropia or hyperphoria Eye turns up

64. Treatment Occlusion/surgery/orthoptics In children to prevent amblyopia and improve binocular function Most effective before age 1 Less effective by age 5 Generally not effective after age 5 In adults done only to eliminate double image, does not improve binocular function

65. Monocularity Various causes Trauma to eye Enucleation Injury to optic nerve If other eye has normal function Lose stereopsis for near images 30 degree restriction in peripheral field More problematic if dominant eye is lost

66. A Singular View Frank Brady