Texas School for the Blind and Visually Impaired
Outreach Programs
www.tsbvi.edu |512-454-8631 | 1100 W. 45th St. | Austin, Texas 78756
2012-13 Texas Focus
Congenital Conditions Affecting Cones
March 31, 2013
10:30 AM -12:00 PM
Presented by
David Lewerenz, OD, FAAO
Assistant Professor, Chief of Low Vision Services,
Northeastern State University Oklahoma
College of Optometry
[email protected]
Developed for
Texas School for the Blind & Visually Impaired
Outreach Programs
Hereditary Cone Disorders
David Lewerenz, OD, FAAO
Northeastern State University
Oklahoma College of Optometry
Figure 1 Image of the retina.
Figure 2 Photo of boy using print magnifier.
Overview
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Rods, cones, vision and the ERG
Achromatopsia
Progressive cone dystrophy
Cone-rod dystrophy
Compare with other conditions
Stargardt disease
Retina
The retina is the light sensitive layer. Photoreceptors are one of the outer layers and point outwardly.
Figure 3 Drawing of the eye and its components.
The Normal Eye
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Normal fundus
o Uniform background
o Pinkish-orange optic nerve
o Small excavated, pale area at center of optic nerve
o Medium sized blood vessels
o Pigmented central, "macular" area
o Foveal reflex
Figure 4 Image of the normal fundus.
Layers of the Retina
Direction of light ↓
Figure 5 Image showing layers of the retina From Remington, Clinical Anatomy of the Visual System, 2005
Congenital Conditions Affecting Cones – Lewerenz, 2012 – 2012-13 Texas Focus
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Rods and Cones
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Contain visual photopigments that are activated by light, a process called phototransduction
Two types
o 5 million cones (not always cone shaped) increase in relative density toward the macula
and are more active in bright illumination: photopic
 Provide sharp, detailed vision and color vision
o 92 million rods increase in relative density toward a point about 15-20 degrees from the
fovea and are more sensitive to light, so they are more active in dim illumination:
scotopic
 Provide vision in the dark
Photoreceptor Morphology
Figure 6 Illustration of photoreceptor from Oyster, The Human Eye: Structure and Function,1999.
Photoreceptors
Large dots in image are cones, small dots are rods, except at
fovea.
One square mm of retina has 200,000 cones at the fovea!
Figure 7 Image showing photoreceptors from Oyster, The Human Eye: Structure and Function, 1999.
Congenital Conditions Affecting Cones – Lewerenz, 2012 – 2012-13 Texas Focus
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Congenital Conditions Affecting Cones – Lewerenz, 2012 – 2012-13 Texas Focus
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Creating a Composite Image
Figure 8 Image of sculpture and path of eye movements from Oyster, The Human Eye: Structure and Function, 1999.
We make many small, quick eye movements ("saccades") without realizing it, especially when
reading and examining an object for detail
Photoreceptors Function
Only 5-10%
of cones
Figure 9 Diagram showing the photorecptors function from Oyster, The Human Eye: Structure and Function, 1999. A series of waves
labled Blue cone 419, Rod 496, Green cone 531, and Red cone 558 appear. A box with the words,”Only 5-10% of cones” is connected
to the blue cone wave by an arrow.
Retinal Pigments
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Melanin
o Makes retinal pigment epithelium dark in color
o Same pigment that darkens tissue throughout the body
o Absorbs stray light
Xanthophylls
o Lutein and Zeathanthin make the macular area darker and provide protection from
degenerative changes
Lipofuscin
o Result of retinal metabolic processes
o Buildup can cause damage to the retina
Congenital Conditions Affecting Cones – Lewerenz, 2012 – 2012-13 Texas Focus
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Electroretinography
Figure 10 Two images showing an electroretinography.
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Electroretinogram (ERG) is a response to light from the cells in the retina
Recorded by an electrode in a contact lens or foil on surface of the eye
Electroretinography
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Can isolate the cones in a photopic ERG
o In a light adapted retina and with a bright flash the rods are washed out and do not
respond
o A light that flickers on and off 30 times per second will also stimulate the cones
selectively (rods respond only up to 20 Hz)
Can isolate the rods in a scotopic ERG
o After dark adapting for 30 minutes and using a dim flash the rods are stimulated
exclusively
Color Vision Deficiency
Figure 11 Two images showing color vision screening tests.
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X-linked recessive
Otherwise visually normally sighted individuals
Two levels of severity – both 20/20
o Dichromacy – More severe
 One cone type not functional
 2% of males
o Trichromacy – Less severe
 One cone type not fully functional
 6% of males
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Hereditary Cone Disorders
Common Characteristics
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Bilateral
Reduced visual acuity
Poor color vision
Light sensitivity (“photophobia”)
Light adaptation problems
Better vision at dusk/night
Temporal optic nerve pallor
Nystagmus can occur if early onset
Achromatopsia
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Poor/no cone function; Present at birth, non-progressive
Reduced visual acuity, poor color vision, light sensitive
Rod Monochromatism
o No cone function
o Autosomal recessive
 Complete
 ~20/200
 Incomplete
 ~20/100
Blue Cone Achromatopsia
o 1 cone type present
o X-Linked recessive
Achromatopsia
All Types
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Decreased or absent cone function at or near birth
o Cones appear to be present, but not functional
May be assumed at first to have congenital nystagmus or (because lightly pigmented fundus in
many cases) ocular albinism if ERG not done
o Not progressive
 May even improve slightly over time
No treatments in clinical trials per www.clinicaltrials.gov
Profoundly impaired cone (photopic) ERG, normal rod (scotopic) ERG
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Achromatopsia ERGs
Figure 12 Image showing ERGs including Scotopic (Rods), Max, 30 Hz Flicker (Cones) and Phototopic (Cones) information from Taylor
and Hoyt, Pediatric Ophthalmology and Strabismus, 2005..
Achromatopsia
All Types
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Nystagmus – typically rapid frequency and low amplitude
May decrease by age ten and may become latent
Light adaptation problems
Photophobia - Light sensitivity
Day blindness – poor vision in bright light
Poor to no color vision
Two major types
o Rod monochromatism
o Blue cone achromatopsia
Congenital Conditions Affecting Cones – Lewerenz, 2012 – 2012-13 Texas Focus
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Achromatopsia
All Types
Figure 13 Images showing retina of 9-year-old with achromatopsia with subtle foveal atrophy and temporal optic nerve pallor. From
Albert Jakobec’s Principles and Practice of Ophthalmology, 3rd edition, Ed. by Albert and Miller, Saunders, 2008.
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Reduced foveal reflex
May have pigment mottling in central and/or mid peripheral retina
May have temporal disc pallor
Nerve Fiber Layer
Figure 14 Image of the nerve fiber layer. from Oyster, The Human Eye: Structure and Function, 1999.
Papillomacular bundle is reason for temporal optic nerve pallor.
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Achromatopsia
Figure 15 Two photographs of people reading.
Rod Monochromatism
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All cones have reduced or no function
High hyperopia is often present
Affects about 1 in 30,000 to 50,000 people
Two forms
o Complete
o Incomplete
Achromatopsia
Figure 16 Toddler wearing glasses looks at a child's picture book.
Rod Monochromatism – 2 Types
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Complete Rod Monochromatism
o Visual acuity ~20/200
o Little or no color vision
o Severe photophobia
Incomplete Rod Monochromatism
o Visual acuity ~20/80 to 20/200
o Moderate loss of color vision
o Moderate photophobia
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Achromatopsia
Figure 17 Image of genetic material.
Rod Monochromatism
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Autosomal recessive inheritance
Three genes responsible for most cases
CNGA3 – 20-30%
CNGB3 – 40-50%, also linked
o to progressive cone dystrophy
o Location within the gene
 can determine severity and
 even the type of condition
GNAT2 - Rare
Oligocone Trichromacy
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All three cone types are present, but function is poor in all the cones
o Like a very incomplete form of rod monochromatism
 Mild visual acuity loss – 20/40 to 20/80
 Mild photophobia
 Normal looking retinas
 No nystagmus
 Normal color vision
 Occurrence is extremely rare
 Autosomal recessive
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Achromatopsia
Blue Cone Achromatopsia
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Blue cone achromatopsia has rods plus the "S" cones that are maximally sensitive to blue light
o Only 5-10% of cones are S cones
o There are no blue ("S") cones in the fovea
o The "M" cones (maximally sensitive to green) and the "L" cones (maximally sensitive to
red) are non functional
 Unable to prove this histologically
o A form of incomplete achromatopsia
o X-Linked Recessive ("XLR Incomplete A.")
Distribution and Number of Blue ("S") Cones
Figure 18 Observed fraction of cone separations from Hafer H, Carroll J, Neitz J, Neitz M, Williams DR, Organization of the Human
Trichromatic Cone Mosaic, The Journal of Neuroscience, Oct. 19, 2005, 25(42): 96669-9679.
Achromatopsia
Blue Cone Achromatopsia
Figure 19 Photo of the Blue cone monochromatism: pale tilted optic dic with myopic fundus from Taylor and Hoyt, Pediatric
Ophthalmology and Strabismus, 2005.
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Achromatopsia
Blue Cone Achromatopsia
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Clinical picture is similar to rod monochromatism, except
o Less loss of visual acuity and color vision than in rod monochromatism
o Vision can be as good as 20/60, can be worse
o Often myopia is present
o Macular changes often progress after age 40, especially if better than 20/100 as a child
o Occurrence is rare, < 1 in 100,000 people
Achromatopsia
How to Tell Type
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Blue Cone A. can be distinguished from rod monochromatism by
o Blue Cone A. occurrence is mostly in males
o Blue Cone A. often myopic, Rod Monochromatism often hyperopic
o Special ERG using blue flash stimulus against yellow background
o Special color vision test (Berson test)
 Problem with cone dystrophy
o OCT – People with Blue Cone A. have thin foveal area
o Genetic testing
Achromatopsia
Well known achromats
Rachel Scdoris
Figure 20 Two photographs of Rachel Scdoris: as an adult and as a child.
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Legally blind from achromatopsia
Completed Iditarod 1,200 mile Alaska dog sled race in 2006
Congenital Conditions Affecting Cones – Lewerenz, 2012 – 2012-13 Texas Focus
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John Kay
Figure 21 Pictures of John Kay and the Steppenwolf album cover for Born to Be Wild.
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Founder and lead singer of Steppenwolf
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Progressive Cone Dystrophy
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Overall decline of cone function throughout the retina
Not limited to the macula/fovea
Develops in childhood or early adulthood
Fine or no nystagmus
Amount of vision loss varies greatly, but usually results in worse than 20/200
Profoundly reduced light adapted (“photopic”) ERG and nearly normal dark adapted
(“scotopic”) ERG
Progressive Cone Dystrophy ERG
Cone Dystrophy - Normal
Scotopic (Rods)
Max
30 Hz Flicker (Cones)
Photopic (Cones)
Pattern ERG (Cones)
Figure 22 ERG comparing Cone Dystrophy (left sets) and Normal vision (right sets). Sets of pictures from top to bottom show:
Scotopic (Rods), Max, 30 Hz Flicker (Cones), Photopic (Cones), and Pattern ERG (Cones) from Taylor and Hoyt, Pediatric
Ophthalmology and Strabismus, 2005.
Congenital Conditions Affecting Cones – Lewerenz, 2012 – 2012-13 Texas Focus
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Progressive Cone Dystrophy
Figure 23 Image of the retina from Basic and Clinical Science Course: Retina and Vitreous, AAO, 2008
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Affects about 1 in 30,000 people
No treatments in clinical trials per www.clinicaltrials.gov
Retina appears normal early
o Loss of foveal reflex
o Foveal atrophy
o Bull's eye maculopathy late
In some cases there can be a glistening green appearance to the retina
Progressive Cone Dystrophy
Figure 24 Four images of the retina from upper left showing early pigment mottling, upper right golden sheen in XLR, lower left Bull's
Eye maculopathy, and bottom right geographic atrophy from Kanski and Bowling, Clinical Ophthalmology: A systematic approach, 7th
ed., 2011
Congenital Conditions Affecting Cones – Lewerenz, 2012 – 2012-13 Texas Focus
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Progressive Cone Dystrophy
Figure 25 Two images of the retina showing a baseline and "after 3 hrs. DA" from Basic and Clinical Science Course: Retina and
Vitreous, AAO, 2008
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Appearance of retinal sheen may change in dark adaptation (Mizuo-Nakamura phenomenon)
in X-linked form
Color vision defect (usually red-green) will sometimes precede loss of visual acuity
Peripheral visual fields are normal
Often rods affected later, resembling cone-rod dystrophy
Progressive Cone Dystrophy
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Inheritance can be variable
o Autosomal dominant – GUGA1A gene
o Autosomal recessive – RDH5 gene
o X-Linked recessive – RPGR and COD2 genes
o It is not known why mutations in some of these genes, which encode proteins in both
rods and cones, affect cones only
o There is no family history in many cases
Cone-Rod Dystrophy
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Sometimes described as an atypical form of retinitis pigmentosa (RP)
Should not be confused with those forms of RP (usually syndromal) that affect cones along
with rods
Difference from achromatopsia
o Not present at birth – Occurs from childhood to age 20
o Progressive loss of vision
Affects about 1 in 40,000 people
Congenital Conditions Affecting Cones – Lewerenz, 2012 – 2012-13 Texas Focus
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Cone-Rod Dystrophy
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Symptoms
o Reduced visual acuity
o Light sensitivity (“photophobia”)
o Reduced color vision
o Reduced night vision later
There is a wide variety of expression, from mild to very severe
Cone-Rod Dystrophy
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Signs
o Retina can appear normal early in the disease
o Macular degeneration, sometimes bulls eye maculopathy
o Attenuation of retinal arterioles
o Bone spicule pigmentation in some cases, resembling retinitis pigmentosa
ERG is profoundly reduced in cones and moderately reduced in rods
Cone-Rod Dystrophy
Figure 26 Three images of retinas from left two show moderate Cone-Rod Dystrophy and Right advanced Cone-Rod Dystrophy.
Cone-Rod Dystrophy
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Inheritance can be variable
o Autosomal dominant
o Autosomal recessive
o X-Linked recessive
Many genes have been linked
The ABCA4 gene (autosomal recessive) is also linked to Stargardt disease, progressive cone
dystrophy and retinitis pigmentosa
Congenital Conditions Affecting Cones – Lewerenz, 2012 – 2012-13 Texas Focus
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Differential Diagnosis
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Can be difficult to distinguish between
o Cone-rod dystrophy
o Cone dystrophy
o Subset of retinitis pigmentosa that affects cones along with rods (often syndromal)
 Worst prognosis for retaining useful peripheral vision
ERG can be important
Following changes over time helps identify the condition
o Especially visual fields
Genetic testing
Confusing Terminology
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Some sources categorize cone dystrophy and cone-rod dystrophy together
Achromatopsia sometimes called a stationary cone dystrophy
Rod-cone dystrophy is a term applied to retinitis pigmentosa and Leber's congenital amaurosis
Some forms of retinitis pigmentosa (mostly syndromal) affect cones equally with rods and are
sometimes referred to as cone-rod dystrophy
Stargardt Disease
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"Juvenile Macular Degeneration"
Not specifically a cone disorder, but the macula is affected, where there is a high density of
cones
o Since cones are not targeted, photophobia is less of a problem than in the other
conditions discussed
The most common inherited macular degeneration – about 1 in 10,000 people
Congenital Conditions Affecting Cones – Lewerenz, 2012 – 2012-13 Texas Focus
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Stargardt Disease
Figure 27 Image of the retina from Basic and Clinical Science Course: Retina and Vitreous, AAO, 2008.
Two conditions or one?
1. Fundus flavimaculatis: White-yellow irregular flecks scattered throughout the retina
2. Atrophy of macula: Slightly oval bulls-eye pattern, later may resemble "beaten bronze"
appearance and later still pigmentary degeneration
 These often occur together, but can have either or both
 Disagreement about classification into two disorders or one
Stargardt Disease
Figure 28 Four images of the retina show in upper left early pigment mottling, upper right "Snail Slime" macula + flecks, lower left Bull's
Eye maculopathy, and lower right Fundus flavimaculatus from Kanski and Bowling, Clinical Ophthalmology: A systematic approach, 7th
ed., 2011.
Congenital Conditions Affecting Cones – Lewerenz, 2012 – 2012-13 Texas Focus
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Stargardt Disease
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Loss of visual acuity in both eyes during teens
o Sometimes there are no visible changes in the retina when vision loss begins, resulting
in accusation of malingering
o Visual acuity often declines from 20/40 to 20/100 in about 5 years and stabilizes at
about 20/200
o No nystagmus, since later onset
Stargardt Disease
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There is a buildup of lipofuscin in the retina pigment epithelium
o This not only damages the retina, but blocks light from going through it, resulting in
"dark retina" in fluorescein angiography
Central blind spot ("scotoma") results
Red-green color vision deficiency sometimes develops
Full field ERG often normal
o May be reduced in fundus flavimaculatis
o Foveal ("multifocal") ERG abnormal
Stargardt Disease
Figure 29 Three images showing retina (middle image of “dark choroid”) from Basic and Clinical Science Course: Retina and Vitreous,
AAO, 2008.
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One clinical finding that indicates Stargardt disease is a "dark choroid" on fluorescein
angiography
o Present in at least 80% of Stargardt cases
o Brightness of the choroid background is masked by lipofuscin
Congenital Conditions Affecting Cones – Lewerenz, 2012 – 2012-13 Texas Focus
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Stargardt Disease
Figure 30 Two images of the retina with the one on the right showing the "dark choroid with window defects" from Taylor and Hoyt,
Pediatric Ophthalmology and Strabismus, 2005.
Stargardt Disease
Figure 31 Image of the retina from Yanoff and Duker, Ophthalmology, 2008.
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Usually autosomal recessive
o ABCA4 gene is one of at least three genes that may be the cause
 Also implicated in autosomal recessive forms of cone-rod dystrophy and retinitis
pigmentosa
A rare autosomal dominant form has been described
Stargardt Disease
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Treatments in clinical trials
o Portland, OR and Paris, France: Gene transfer,, Phase I/II, Oxford BioMedica
o Los Angeles, Philadelphia, UK: Transplant of human embryonic stem cells, Phase I/II,
Advanced Cell Technology
o Italy: Saffron supplementation
Completed or closed clinical trials
o 4-Methylpyrazole, which inhibits dark adaptation, completed 2006, results not promising
o DHA supplementation – one completed, one closed
Congenital Conditions Affecting Cones – Lewerenz, 2012 – 2012-13 Texas Focus
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Best Disease
Figure 32 Two images of the retina with upper image showing “Adult Onset Disease” from Kanski and Bowling, Clinical Ophthalmology:
A systematic approach, 7th ed., 2011
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Also called vitelliform (egg-like) macular dystrophy
Like Stargardt disease, not a disease of cones, but a disease of the macula, which is where
there is a high density of cones
Usually occurs in childhood or early adulthood
o Sometimes not present until middle age
Best Disease
33 Two images of the retina from From Basic and Clinical Science Course: Retina and Vitreous, AAO, 2008.
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Four stages
1. Previtelliform – Near normal retinal appearance and vision
2. Vitelliform – Macula resembles egg yolk, visual acuity has mild decrease
3. Pseudohypopyon – Yellow egg yolk appearance concentrates in lower portion of macular
lesion
4. Scrambled egg appearance – Scattered yellow areas, possible fibrosis and
neovascularization
Yellow "egg yolk" material is lipofuscin
Visual acuity usually better than expected from retinal appearance
Congenital Conditions Affecting Cones – Lewerenz, 2012 – 2012-13 Texas Focus
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Best Disease
34 Six Images of the retina: top left Vitelliform stage II, top right Blocked choroidal background, mid left Material in RPE, mid right
Multifocal disease, bottom left Pseudohypopyon III, bottom right Vitelliruptive stage IV from Kanski and Bowling, Clinical
Ophthalmology: A systematic approach, 7th ed., 2011.
Prevalence = 1 to 9 out of 100,000 people, per www.orpha.net
Best Disease
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Mild to moderate vision loss
88% will have at least one eye with 20/40 or better
Only 4% will have visual acuity worse than 20/200
Electro-oculogram (EOG) light/dark (Arden) ratio is reduced
o Sometimes EOG is normal
o Full-field ERG usually normal
o Foveal (multifocal) ERG is usually reduced
Often hyperopic
Autosomal dominant inheritance – VMD2 gene
No treatments in clinical trials per www.clinicaltrials.gov
Congenital Conditions Affecting Cones – Lewerenz, 2012 – 2012-13 Texas Focus
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Relative Prevalence
Disorder
1 in
Texas
United States
Aniridia
70,000
375
4,200
Ocular Albinism
50,000
500
5,900
Achromatopsia
40,000
650
7,500
Cone-Rod Dystrophy
40,000
650
7,500
Leber's Congenital Amaurosis
40,000
650
7,500
Progressive Cone Dystrophy
30,000
850
9,800
Best Disease (approximate)
22,000
1,300
15,000
Oculocutaneous Albinism
17,000
1,500
18,000
Optic Nerve Hypoplasia
10,000
2,600
30,000
Stargardt Disease
10,000
2,600
30,000
Retinitis Pigmentosa
3,750
7,400
85,000
Rehabilitation – Core Needs
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Magnification for detailed vision
o Near vision
o Distance vision
Photophobia & glare management
o Outdoors – sunlight
o Indoors – artificial lighting
Coping with color vision loss
Congenital Conditions Affecting Cones – Lewerenz, 2012 – 2012-13 Texas Focus
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Mobility
General support
Magnification at Near
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Three ways to magnify at near, such as reading
o Make the print larger
 Relative size magnification
o Use a magnifier
 Angular magnification
o Bring the print closer
 Relative distance magnification
Making the Print Larger
Normal print might require magnification to make reading comfortable or even possible, but may lead
to greater independence
Large print is usually about twice the size as normal print.
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Advantages
o Easy
Disadvantages
o Large print books are large, heavy and expensive
o Few large print resources may be available after student leaves school
o Limited magnification
Making the Print Larger
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From the Council for Exceptional Children, "The voice and vision of special education"
o Division on Visual Impairments position paper, "Access to Print"
http://www.cecdvi.org/Postion%20Papers/low_vision_print.htm
"It is recommended that individuals with visual impairments resulting in low vision use standard
rather than large print whenever possible and when appropriate to the task and ease of use."
This position has been maintained and rewritten since 1984
Congenital Conditions Affecting Cones – Lewerenz, 2012 – 2012-13 Texas Focus
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Using a Magnifier
Figure 35 Two photos showing students using magnifiers.
Figure 36 Four pictures of different kinds of magnifiers
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Advantages
o Makes everything large print
o Available in many powers
Disadvantages
o Must carry with you
o Small field of view
o Lots of misunderstanding
Congenital Conditions Affecting Cones – Lewerenz, 2012 – 2012-13 Texas Focus
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Bring the Print Closer
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Advantages
o Wide field
o Portability
o Minimizes effect of scotoma
Disadvantages
o May require glasses with bifocal to relieve focusing fatigue
Minimizing Effect of Scotoma
By using relative distance magnification
(The presenter created a complex drawing to show how magnification can minimize the effect of
scotoma).
Magnification at Near
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Choosing a magnification device is not a trial and error process
Recommendation of magnification devices should be made by people who understand their
optics
o They need to listen to and respond to the feedback of educators, parents, and vision
rehab. professionals concerning students' needs and the performance of recommended
devices
No magnification device works best for all people
No magnification device works best for all tasks
Magnification at Distance
Figure 38 A woman
uses a spectacle
mounted magnifier.
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Figure 37 A young boy uses and hand
held telescope.
Telescopes are the only optical devices that can magnify at a distance
Types
o Handheld
o Spectacle mounted
Congenital Conditions Affecting Cones – Lewerenz, 2012 – 2012-13 Texas Focus
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
Bioptic
Magnification at Distance
Figure 39 A young woman adjusts a telescope.
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Telescopes are used for spotting
Telescopes extend the "visual reach"
Telescopes require training
Nystagmus does not preclude the use of telescopes
Powers: 2X to 10X
In general field of view decreases as telescope power increases
Magnification at Near & Distance
Many electronic devices available
Electronic books offer large print and speech options
Figure 40 Six pictures of various print enlargement devices for reading.
Congenital Conditions Affecting Cones – Lewerenz, 2012 – 2012-13 Texas Focus
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Magnification at Near & Distance
Figure 41 Photo of a Kindle
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Figure 42 Photo of IPad
Kindle – less glare
IPad – better contrast
Photophobia & Glare
Figure 43 Two photos: one showing a little boy wearing dark glasses and another showing two pairs of glasses with yellow and dark
amber lenses.
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No firm guidelines for filter selection
Often gray or brown for outdoors
Often yellow or orange for indoors
Plum used by many
Red contact lenses have found success*
Don't forget importance of hat or visor
*Park WL, Sunness JS. Red contact lenses for alleviation of photophobia in patients with cone
disorders. Am J Ophthalmol 2004; 137:774-5.
Congenital Conditions Affecting Cones – Lewerenz, 2012 – 2012-13 Texas Focus
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Color Vision Loss
Figure 45 X-Chrome
contact lens
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Figure 44 Electronic color
identification tool
Limited treatment options
X-Chrome contact lens
Electronic color identification tool
Color identification app
o Color ID 2 by GreenGar
Mobility
Figure 46 Photo of a woman and her O&M instructor traveling a city street.
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Not needed in all cases, but…
Don't neglect just because there might not be peripheral visual field loss
Congenital Conditions Affecting Cones – Lewerenz, 2012 – 2012-13 Texas Focus
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General Support
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Medical eye care
Parental education
Support organizations
Educational consultation
School for the blind and visually impaired
Mainstream school
Educational / Rehabilitation services
Driving / Transportation advice
o Bioptics legal in the state?
General Support
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Counseling
o Importance of a peer group
o "Passing"
Post-secondary education options
Career counseling
Genetic counseling
Thanks for your attention!
David Lewerenz, OD, FAAO
Northeastern State University
Oklahoma College of Optometry
[email protected]
918-444-4090
Figure 47 Two images showing Northeastern State University,
Oklahoma College of Optometry and logo.
Congenital Conditions Affecting Cones – Lewerenz, 2012 – 2012-13 Texas Focus
Figure 48 Two images showing statue and
Northeastern State University logo.
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Texas School for the Blind & Visually Impaired
Outreach Programs
Figure 24 TSBVI logo.
"This project is supported by the U.S. Department of Education, Office of Special
Education Programs (OSEP). Opinions expressed herein are those of the authors and do
Congenital Conditions Affecting Cones – Lewerenz, 2012 – 2012-13 Texas Focus
33
not necessarily represent the position of the U.S. Department of Education.
Figure 25 IDEA logo
Congenital Conditions Affecting Cones – Lewerenz, 2012 – 2012-13 Texas Focus
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Cone-Rod Dystrophy - Texas School for the Blind and Visually