Ce diaporama a bien été signalé.
Nous utilisons votre profil LinkedIn et vos données d’activité pour vous proposer des publicités personnalisées et pertinentes. Vous pouvez changer vos préférences de publicités à tout moment.
CONTRAST SENSITIVITY
PRESENTER; DR. LEENA VADHEL
MODERATOR: DR. MRUDULA BHAVE
Definition:
Contrast:- defined as the degree of blackness to
whiteness of target.
Contrast threshold:-is the smallest am...
WHAT IS CONTRAST SENSITIVITY
the ability to perceive slight changes in
luminance between regions which are not
separated ...
SNELLENS VISUAL ACUITY VERSUS
CONTRAST SENSITIVITY
Snellen’s charts test VA at a very high contrast
thus many patients ha...
CONTRAST SENSITIVITY CURVE
C .S is presented
as curve which
plots the lowest
contrast level a
patient can detect
for spec...
CONTRAST SENSITIVITY FUNCTION
 The contrast sensitivity function proposed
by Manos and Sakrison.
A plot of CS over a ran...
CONTRAST SENSITIVITY FUNCTION
Contrast sensitivity function (CSF) is a
subjective measurement of a person's ability
to de...
CONTRAST SENSITIVITY FUNCTION
CSF has a peak value
of approximately 1 to 8
cycles/ degree.
Distinction of high
frequenci...
CONTRAST SENSITIVITY FUNCTION
Neural and optical
attenuation limits
the high spatial
frequency CS.
Point where the
CSF c...
MICHELSON FORMULA:
L max- Lmin/Lmax+Lmin
Lmax = Luminance on the lighter surface
Lmin = Luminance on the darker surface...
low medium high
object:
100% 
contrast
image
spatial frequency
contrast
1
0
• The modulation transfer function (MTF) indicates the ability of an
optical system to reproduce (transfer) various levels...
MTF: Cutoff FrequencyMTF: Cutoff Frequency
0
0.5
1
0 50 100 150 200 250 300
1 mm
2 mm
4 mm
6 mm
8 mm
modulationtransfer
sp...
Gratings
One adjacent pair of light and dark bars
makes up one cycle.
The thickness of the grating is described by
their...
Gratings
Gratings are broader and are of low spatial
frequency.
Spatial phase defines its position.
Change in spatial p...
Sine wave gratings
These gratings are
lacking in sharp
borders.
Sinusoidal gratings
are used because
they are not subjec...
Square wave gratings
square-wave
gratings have
characteristics like
a square such as
sharp edges.
POSITION OF GRATINGS
TYPES OF CONTRAST SENSITIVITY:
1. Spatial contrast sensitivity
2. temporal contrast sensitivity
SPATIAL CONTRAST SENSITIVITY
Detection of striped pattern at various levels of
contrast and spatial frequency.
Sine wave...
 The spatial frequency
increases
exponentially from left
to right. The contrast
also varies
logarithmically from
100% at ...
TEMPORAL CONTRAST SENSITIVITY
Temporal contrast sensitivity is measured with
gratings that reverse contrast at various ra...
The shape of the contrast sensitivity function
varies with factors:
Luminance
Target size
Grating motion
Grating shape
Neural mechanism of contrast
sensitivity:
Campbell and Green gave the concepts of
different visual channels for handling
...
M and P------- pathways
Ganglion cells divded into
p- Cells :- small,slow
conducting axons that input
into parvocellular...
Channel theory
CSF is a function of several independent parallel
detecting mechanisms.
Each channel is highly sensitive ...
Channels
CSF channel could be due to a series of ganglion
cells that have receptive fields of different sizes so
that the...
SYMPTOMS OF CONTRAST SENSITIVITY
Have problems with night
driving, including inability to
see traffic lights
May require...
MEASUREMENT OF CONTRAST SENSITIVITY:
There are three variables in measurement of
contrast sensitivity:
1. Average amount ...
The various methods available to measure CS
include
 Pelli Robson test
 Bailey Lovie chart
 Vision contrast test syste...
PELLI ROBSON CONTRAST SENSITIVITY
CHARTS
letters of the same
size but with
reducing contrast
two charts and two
scoring ...
The score of the
test is recorded by
the faintest triplet
out of which at
least 2 letters are
correctly
identified.
The ...
CAMBRIDGE LOW CONTRAST GRATING
 It is a rapid and simple screening test for
contrast sensitivity.
 Performed at a distan...
The plates are changed sequentially starting
from plate 1 till the patient fails to respond.
Then a new series is begun ...
BAILEY LOVIE CHART
Low contrast acuity testing & acuity testing in
presence of glare.
Each row has same no. of symbols &...
FUNCTIONAL ACUITY CONTRAST
TESTING(F.A.C.T)
FACT charts were developed by Dr. Arthur
Ginsburg.
FACT comprises of a chart...
And the spatial frequencies increase as one
move down the various columns from top to
bottom.
This test is performed at ...
THE ARDEN PLATE TEST
Introduced in 1978.
Consists of a booklet
containing several sine
wave gratings patterns
Each grat...
VISTECH CONTRAST SENSITIVITY TEST
These charts consist of sine wave gratings.
Each chart contains five rows and nine colu...
Two separate Vistech charts are available: the
VCTS-6500 for distance testing and the VCTS-
6000 for near testing.
A pro...
REGAN LOW CONTRAST LETTER CHARTS
Consists of three letter charts, printed on white
cardboard having contrast of 97%, 7% a...
It is widely used in the world
This test provides four rows
of sine-wave gratings
The test distant 2.5 meters,
these gr...
Use for screening refractive surgery patients
Used for in or out of office screening and for
cataract evaluation
Used to evaluate both contrast sensitivity and
low contrast acuity
Contain 3 contrast levels
Provided the same tests as standard CSV-
1000-S expect that acuity is presented in
landolt c format
Useful when patient ...
It is special test designed specifically for food
and drug administration clinical trials
FACTORS AFFECTING CONTRAST
SENSITIVITY
1. refractive errors.
2. age
3.cataract
4.contact lenses
5.refractive surgery.
6.gl...
Refractive errors:
Uncorrected refractive disorders manifest
themselves as a decline in contrast sensitivity
first at sma...
STUDY
 Measurements were made at distance (with
Vistech charts), at near (with Arden gratings),
and with a pinhole to con...
Age:
There occurs a definite decrease in contrast
sensitivity with increasing age.
 The pathogenesis of this decline in ...
As the aperture of lens increases the average
focal point move towards the lens so that a
larger pupil produces greater s...
Total wavefront aberration of the eye increases
more than threefold, between 20 to 70 years of
age.
 the aging lens lose...
STUDY
Monocular and binocular contrast sensitivity
function for a range of spatial frequencies was
measured in two groups...
Cataract:
Early cataracts generally cause contrast
sensitivity losses similar to refractive disorders
at higher spatial f...
STUDY
significant loss of contrast sensitivity at all
spatial frequencies with increasing cataract
severity. Contrast sen...
Contact lenses:
to ensure proper contact lens fit as well as
determining when replacement is necessary.
Uncorrected resi...
study concluded that those female professional
and collegiate tennis players wearing no
corrective lenses were significan...
STUDY
Glaucoma: Glaucoma can reduce contrast
sensitivity for all grating sizes, a number of studies
shown reduce contrast...
The low-spatial-frequency-sensitive channels of
both pathways, which are presumably mediated
by cells with larger recepti...
STUDY
IOLs
A study was carried out to evaluate the contrast
sensitivity at near and distance after MFIOL
implantation in...
CONTRAST
SENSITIVITY
MULTIFOCAL MONOFOCAL
CONTRAST
SENSITIVITY AT
DISTANCE(1 MONTH)
(3 MONTHS)
(6, 12 AND 18)
CONTRAST
SEN...
MONOFOCAL
(ALCON
ACRYSOF)
ACCOMOD
ATING
(HUMAN
OPTICS)
DIFFRACTIVE
MFIOL
(TECNIS)
REFRACTIVE
MFIOL
(AMO
REZOOM)
NEAR
VISUA...
multifocal In patients with unilateral cataract,
monofocal, accommodating and partially diffractive
multifocal IOL provid...
Diabetic retinopathy:
In diabetic retinopathy patients, contrast
sensitivity loss may occur for all grating sizes.
a stu...
RESULTS:
Letter CS was able to distinguish those
participants with and without macular oedema
and those with no or minima...
Optic neuropathies:
A variety of optic neuropathies including
afferent pupillary defect, optic neuritis, and
multiple scl...
Pituitary adenoma:
Pituitary adenoma has been shown to cause
contrast sensitivity loss at the middle grating
sizes.
STUDY
Cases report was made by
neuroophthalmological examination in two
patients with parasellar pituitary adenoma
before...
The presented cases indicate that the low
contrast acuity tests in patients with parasellar
pituitary adenoma are sensiti...
Toxic Chemicals:
Several occupational studies have indicated
that chronic, airborne exposure adversely
affects neurobehav...
CONTRAST SENSTIVITY AND LASIK
Why refractive surgery can affect the quality of
vision.
there are other factors in the eye...
Examples of the change in contrast sensitivity
with lasik refractive surgery:
The graphs show the pretreatment level of
c...
the patient contrast sensitivity does not recover to the
presurgery levels. The following graph shows an
example of this r...
Several surgeons have noted that some patients with high levels
of myopia (> - 9 diopters) actually improve contrast sensi...
Low contrast acuity after lasik
glare testing, which shines a bright light in the
patient's eye, reduces pupil size and typically causes
vision to improve...
With glare, the yellow filter also improved
contrast sensitivity in LASIK patients, but not
significantly. 
J Refract sur...
Contrast sensitivity
Contrast sensitivity
Contrast sensitivity
Contrast sensitivity
Contrast sensitivity
Contrast sensitivity
Contrast sensitivity
Contrast sensitivity
Contrast sensitivity
Prochain SlideShare
Chargement dans…5
×

Contrast sensitivity

Contrast sensitivity

  • Identifiez-vous pour voir les commentaires

Contrast sensitivity

  1. 1. CONTRAST SENSITIVITY PRESENTER; DR. LEENA VADHEL MODERATOR: DR. MRUDULA BHAVE
  2. 2. Definition: Contrast:- defined as the degree of blackness to whiteness of target. Contrast threshold:-is the smallest amount of contrast required to be able to see the target. Contrast sensitivity:- is the reciprocal of the contrast threshold.
  3. 3. WHAT IS CONTRAST SENSITIVITY the ability to perceive slight changes in luminance between regions which are not separated by definite borders and is just as important as the ability to perceive sharp outlines of relatively small objects.
  4. 4. SNELLENS VISUAL ACUITY VERSUS CONTRAST SENSITIVITY Snellen’s charts test VA at a very high contrast thus many patients have a good snellens VA but they may be visually handicapped in real life situations. The VA drops in the situations with low contrast and the quality of vision is not good. It provides the information that cannot be obtained from visual acuity, and it is often a better predictor of visual performance then VA.
  5. 5. CONTRAST SENSITIVITY CURVE C .S is presented as curve which plots the lowest contrast level a patient can detect for specific size target. The x-axis curve is for spatial frequency, y-axis is for contrast sensitivity.
  6. 6. CONTRAST SENSITIVITY FUNCTION  The contrast sensitivity function proposed by Manos and Sakrison. A plot of CS over a range of spatial frequencies gives the contrast sensitivity function(CSF). Contrast sensitivity depends on spatial frequency. Spatial frequency of visual stimuli is given in cycles per degree.  
  7. 7. CONTRAST SENSITIVITY FUNCTION Contrast sensitivity function (CSF) is a subjective measurement of a person's ability to detect a low contrast pattern stimuli, usually vertical stripes of decreasing shades of black to grey. The resulting measurement is said to give a more accurate representation of the eyes' visual performance.
  8. 8. CONTRAST SENSITIVITY FUNCTION CSF has a peak value of approximately 1 to 8 cycles/ degree. Distinction of high frequencies not possible because of limited number of photoreceptors.
  9. 9. CONTRAST SENSITIVITY FUNCTION Neural and optical attenuation limits the high spatial frequency CS. Point where the CSF cuts the x axis is called cut off frequency.
  10. 10. MICHELSON FORMULA: L max- Lmin/Lmax+Lmin Lmax = Luminance on the lighter surface Lmin = Luminance on the darker surface WEBERS FORMULA: Defined as ( Lb – Lt ) / Lb Lb & Lt are the luminance of the background and target respectively. Weber contrast used in calculating the contrast of letters.
  11. 11. low medium high object: 100%  contrast image spatial frequency contrast 1 0
  12. 12. • The modulation transfer function (MTF) indicates the ability of an optical system to reproduce (transfer) various levels of detail (spatial frequencies) from the object to the image. • Its units are the ratio of image contrast over the object contrast as a function of spatial frequency. • It is the optical contribution to the contrast sensitivity function (CSF).
  13. 13. MTF: Cutoff FrequencyMTF: Cutoff Frequency 0 0.5 1 0 50 100 150 200 250 300 1 mm 2 mm 4 mm 6 mm 8 mm modulationtransfer spatial frequency (c/deg) cut-off frequency 57.3 cutoff a f λ = ⋅ Rule of thumb: cutoff frequency increases by ~30 c/d for each mm increase in pupil size
  14. 14. Gratings One adjacent pair of light and dark bars makes up one cycle. The thickness of the grating is described by their spatial frequency in cycles per degree of the visual angle at the eye.. Large number of grating can fit with in a degree of visual angle
  15. 15. Gratings Gratings are broader and are of low spatial frequency. Spatial phase defines its position. Change in spatial phase by 180 degrees indicates that the grating is displaced by half a cycle.
  16. 16. Sine wave gratings These gratings are lacking in sharp borders. Sinusoidal gratings are used because they are not subject to defocus, aberration,diffraction, light scatter.  Only the contrast and spatial position are affected.
  17. 17. Square wave gratings square-wave gratings have characteristics like a square such as sharp edges.
  18. 18. POSITION OF GRATINGS
  19. 19. TYPES OF CONTRAST SENSITIVITY: 1. Spatial contrast sensitivity 2. temporal contrast sensitivity
  20. 20. SPATIAL CONTRAST SENSITIVITY Detection of striped pattern at various levels of contrast and spatial frequency. Sine wave gratings of parallel light and dark bands. Measured with stationary gratings width of the bar is defined as spatial frequency High spatial frequency- narrow bars. low spatial frequency- wide bars.
  21. 21.  The spatial frequency increases exponentially from left to right. The contrast also varies logarithmically from 100% at the bottom to about 0.5% at the top
  22. 22. TEMPORAL CONTRAST SENSITIVITY Temporal contrast sensitivity is measured with gratings that reverse contrast at various rates over time.  here contrast sensitivity function is generated for the time related processing in the visual system by presenting a uniform target field modulated sinusoidal in time. Both the system provides more complete and systemic data on the status of visual performance.
  23. 23. The shape of the contrast sensitivity function varies with factors: Luminance Target size Grating motion Grating shape
  24. 24. Neural mechanism of contrast sensitivity: Campbell and Green gave the concepts of different visual channels for handling information about bands of spatial frequencies.  This concept indicates that the retina is not uniform. Fovea is specialized for high acuity and is responsible for high spatial frequencies.  In the retinal periphery, only low frequency channels are represented.
  25. 25. M and P------- pathways Ganglion cells divded into p- Cells :- small,slow conducting axons that input into parvocellular layers of the lateral geniculate body. P-Cells have higher spatial resolution. m-Cells :- large ,fast conducting axons that input into the magnocellular layers. M- Cells have higher contrast sensitivity and temporal resolution and lower spatial resolution.
  26. 26. Channel theory CSF is a function of several independent parallel detecting mechanisms. Each channel is highly sensitive to some particular spatial frequency  Visual world is broken into its separate spatial frequency components and this information is then passed in separate channels to the cortex,where it reconstructed. Visual system consists of 4 to 6 spatial frequency channels
  27. 27. Channels CSF channel could be due to a series of ganglion cells that have receptive fields of different sizes so that they are maximally sensitive to different spatial frequencies. Stimuli smaller than the center receptive field only produce a partial response from the ganglion cell. Stimuli larger than the center receptive field also stimulate the surrounding area so that the overall response from ganglion cell is reduced.
  28. 28. SYMPTOMS OF CONTRAST SENSITIVITY Have problems with night driving, including inability to see traffic lights May require extra light to read Their eyes may become tired when they read or watch television  Not being able to see spots on clothes, counters, or dishes Missing facial gestures
  29. 29. MEASUREMENT OF CONTRAST SENSITIVITY: There are three variables in measurement of contrast sensitivity: 1. Average amount of light reflected depends on illumination of paper and darkness of ink. 2.Degree of blackness in relation to white background that is contrast. 3. The distance between the grating periods of cycles per degree of visual angle.
  30. 30. The various methods available to measure CS include  Pelli Robson test  Bailey Lovie chart  Vision contrast test system (VCTS) by Vistech  Cambridge low contrast grating  Regan charts  FACT charts
  31. 31. PELLI ROBSON CONTRAST SENSITIVITY CHARTS letters of the same size but with reducing contrast two charts and two scoring pads. Each chart has 6 letters in each row organized into two triplets of varying contrast. illumination of the chart is 85 cd/mm2 1 meter distance
  32. 32. The score of the test is recorded by the faintest triplet out of which at least 2 letters are correctly identified. The log CS value for this triplet is given by the number on the scoring pad.
  33. 33. CAMBRIDGE LOW CONTRAST GRATING  It is a rapid and simple screening test for contrast sensitivity.  Performed at a distance of 6m.  It comprises of 12 pair of plates consisting of stripes of varying contrast.  First one is for demonstration and rest are for the proper testing and are numbered from 1-10.
  34. 34. The plates are changed sequentially starting from plate 1 till the patient fails to respond. Then a new series is begun starting 4 plates prior to where the patient failed to respond. Four such series are completed and the score of each series is noted (numbered as per the number of plate read) and added. The final total value is converted into contrast sensitivity from the provided table.
  35. 35. BAILEY LOVIE CHART Low contrast acuity testing & acuity testing in presence of glare. Each row has same no. of symbols & constant spacing is used between rows & letters. Chart is logarithmic based & visual acuity is based on log of minimum angle of resolution or logMAR. Berkely Glare Test provides 10% of contrast & is provided with glare source
  36. 36. FUNCTIONAL ACUITY CONTRAST TESTING(F.A.C.T) FACT charts were developed by Dr. Arthur Ginsburg. FACT comprises of a chart with sine-wave gratings of varying frequencies. The chart tests five spatial frequencies (sizes) and nine levels of contrast The Contrast varies in a row, decrease from left to right
  37. 37. And the spatial frequencies increase as one move down the various columns from top to bottom. This test is performed at a distance of 10 feet. The patient determines the last grating seen for each row (A, B, C, D and E) and reports the orientation of the grating: right, up or left. The last correct grating seen for each spatial frequency is plotted on a contrast sensitivity curve.
  38. 38. THE ARDEN PLATE TEST Introduced in 1978. Consists of a booklet containing several sine wave gratings patterns Each grating is oriented vertically The contrast varies from the top to the bottom of the grating, lowest at the top and highest at the bottom.
  39. 39. VISTECH CONTRAST SENSITIVITY TEST These charts consist of sine wave gratings. Each chart contains five rows and nine columns of circular photographic plates (disc) on gray background. Each row has different spatial frequency (1.5 to 18 c.p.d. at three meters) and contrast within the row reduces from left to right. The gratings are presented in three orientations: vertical 90 degrees, 15 degrees clockwise or anticlockwise.
  40. 40. Two separate Vistech charts are available: the VCTS-6500 for distance testing and the VCTS- 6000 for near testing. A projector slide the VCTS-500S is also available.  A luminance of between 103 and 240cd/m2 is recommended.  It can be used to document the performance of low vision patients.
  41. 41. REGAN LOW CONTRAST LETTER CHARTS Consists of three letter charts, printed on white cardboard having contrast of 97%, 7% and 4% 3 meter with eight letters in each line Patients are instructed to start at the top and to continue reading until they can correctly identify no letters on a line. For one chart letter size goes on reducing and contrast remains constant Regan in 1988 suggested there chief role in detecting early visual loss in diabetes and glaucoma.
  42. 42. It is widely used in the world This test provides four rows of sine-wave gratings The test distant 2.5 meters, these gratings test the spatial frequencies of 3,7,12,and 18 cycles/degree Good for evaluation eye disease
  43. 43. Use for screening refractive surgery patients
  44. 44. Used for in or out of office screening and for cataract evaluation
  45. 45. Used to evaluate both contrast sensitivity and low contrast acuity Contain 3 contrast levels
  46. 46. Provided the same tests as standard CSV- 1000-S expect that acuity is presented in landolt c format Useful when patient cant read English alphabet
  47. 47. It is special test designed specifically for food and drug administration clinical trials
  48. 48. FACTORS AFFECTING CONTRAST SENSITIVITY 1. refractive errors. 2. age 3.cataract 4.contact lenses 5.refractive surgery. 6.glaucoma. 7.diabetic retinopathy. 8.optic neruopathies 9.pituitary adenoma. 10.drugs. 11.toxic chemicals
  49. 49. Refractive errors: Uncorrected refractive disorders manifest themselves as a decline in contrast sensitivity first at smaller grating sizes or higher spatial frequencies for mild refractive disorders.  As the degree of refractive disorder increases, contrast sensitivity declines at the middle and then larger grating sizes (middle to lower spatial frequencies).
  50. 50. STUDY  Measurements were made at distance (with Vistech charts), at near (with Arden gratings), and with a pinhole to control pupil size.  Under all conditions, when visual acuity was reduced by spherical lenses, there was a loss of contrast sensitivity over a broad range of spatial frequencies. Ophthalmology 1988 Jan;95(1):139-43. Eeffectof visual blur on contrast sensitivity. Clinical implication Marmor MF, Gawande A
  51. 51. Age: There occurs a definite decrease in contrast sensitivity with increasing age.  The pathogenesis of this decline in vision is likely involves changes in the spherical aberration of the crystalline lens
  52. 52. As the aperture of lens increases the average focal point move towards the lens so that a larger pupil produces greater spherical aberration  Spherical aberration of cornea changes little with the age of the people.
  53. 53. Total wavefront aberration of the eye increases more than threefold, between 20 to 70 years of age.  the aging lens loses its balance with the cornea, because both the magnitude and sign of its spherical aberration change significantly. A loss of balance between corneal and lenticular spherical aberration causes the degradation of optical quality in the aging eye.
  54. 54. STUDY Monocular and binocular contrast sensitivity function for a range of spatial frequencies was measured in two groups of subjects with normal vision.  In the age range 50-87 years there was a linear decline in contrast sensitivity with age for medium and high spatial frequencies, but sensitivity for low spatial frequencies was independent of age. Effect of age on contrast sensitivity function: uniocular and binocular findings  J E Ross D D Clarke and A J Bron.
  55. 55. Cataract: Early cataracts generally cause contrast sensitivity losses similar to refractive disorders at higher spatial frequencies. The addition of glare source will exacerbate the results for patients with cataract, producing lower contrast sensitivity at some or all grating sizes
  56. 56. STUDY significant loss of contrast sensitivity at all spatial frequencies with increasing cataract severity. Contrast sensitivity was significantly reduced at high spatial frequency (18 cpd) in cortical cataracts in the presence of glare in day light and at low spatial frequency (3 cpd) in night light. Contrast sensitivity scores may offer additional information over standard VA tests in patients with early age-related cataracts.   Ophthalmic Vis Res. 2011 January; 6(1): 26–31.  Effect of Cataract Type and Severity on Visual Acuity and Contrast Sensitivity Javad Heravian Shandiz MSc, PhD,1 Akbar Derakhshan MD,2
  57. 57. Contact lenses: to ensure proper contact lens fit as well as determining when replacement is necessary. Uncorrected residual astigmatism from soft contact lens can result in decrease contrast sensitivity at the middle and higher spatial frequencies when compared to hard contact lenses.
  58. 58. study concluded that those female professional and collegiate tennis players wearing no corrective lenses were significantly higher in CS at intermittent and high spatial frequencies than those who wore daily-wear soft contact lenses in competition. Kluka, D.A. and Love, P.A. “Effects of Daily – Wear Contact Lenses Upon Contrast Sensitivity in Selected Professional and Collegiate Female Tennis Players,” UBA at Birmingham
  59. 59. STUDY Glaucoma: Glaucoma can reduce contrast sensitivity for all grating sizes, a number of studies shown reduce contrast sensitivity mostly at the middle spatial frequencies.  study was carried out to explore the effects of glaucoma on low-spatial-frequency contrast sensitivity by using tests designed to assess performance of either the magnocellular (M) or parvocellular (P) visual pathways. Sensitivity was reduced foveally and in the midperiphery across the spatial frequency range. In the area of early visual field loss, the glaucoma group demonstrated further sensitivity reduction across the spatial frequency range.
  60. 60. The low-spatial-frequency-sensitive channels of both pathways, which are presumably mediated by cells with larger receptive fields, are approximately equivalently impaired in glaucoma.  Contrast sensitivity changes due to glaucoma and normal aging: low-spatial- frequency losses in both magnocellular and parvocellular pathways.  McKendrick AM Sampson GP, Walland MJ, Badcock DR  Invest Ophthalmol Vis Sci.2007 May;48(5):2115-22
  61. 61. STUDY IOLs A study was carried out to evaluate the contrast sensitivity at near and distance after MFIOL implantation in 21 patients. A control group with monofocal iol was also studied. CS measured after 1,3,6,12,and 18 months after IOL.
  62. 62. CONTRAST SENSITIVITY MULTIFOCAL MONOFOCAL CONTRAST SENSITIVITY AT DISTANCE(1 MONTH) (3 MONTHS) (6, 12 AND 18) CONTRAST SENSITIVITY AT NEAR L Cataract refractive surgery.2003apr;29(4):703-11 Montes mico R
  63. 63. MONOFOCAL (ALCON ACRYSOF) ACCOMOD ATING (HUMAN OPTICS) DIFFRACTIVE MFIOL (TECNIS) REFRACTIVE MFIOL (AMO REZOOM) NEAR VISUAL ACUITY - - BETTER - DIST. CS HIGH HIGH - LOW NEAR CS HIGH SF MONOCUL AR AND BINOCULAR CS HIGH HIGH HIGH HIGH HIGH LOW LOW LOW
  64. 64. multifocal In patients with unilateral cataract, monofocal, accommodating and partially diffractive multifocal IOL provided higher CS scores when compared with refractive IOL. Clinical and experimental ophthalmology Differences in contrast sensitivity between monofocal, multifocal and accommodatingintraocular lenses: long-term results Cem Mesci MD, Hasan H Erbil MD, Ali Olgun MD, Nihat Aydin MD, Article first published online: 3 NOV 2010 DOI: 10.1111/j.1442- 9071.2010.02357.
  65. 65. Diabetic retinopathy: In diabetic retinopathy patients, contrast sensitivity loss may occur for all grating sizes. a study was carried out to evaluate contrast sensitivity (CS) and visual acuity (VA) in detecting functional losses in participants with type 2 diabetes. LogMAR VA and letter CS were measured on 20 type 2 diabetic and 24 age-matched control participants. The diabetic participants were sub-grouped according to the level of retinopathy present.
  66. 66. RESULTS: Letter CS was able to distinguish those participants with and without macular oedema and those with no or minimal diabetic retinopathy from the control group, whereas VA was not. Clinical optom 2003 May;86(3):152-6 Letter contrast sensitivity changes in early diabetic retinopathy Stavrou EP, Wood JM
  67. 67. Optic neuropathies: A variety of optic neuropathies including afferent pupillary defect, optic neuritis, and multiple sclerosis will affect contrast sensitivity losses over some or all grating sizes. Multiple sclerosis can sometimes affect only middle sizes.
  68. 68. Pituitary adenoma: Pituitary adenoma has been shown to cause contrast sensitivity loss at the middle grating sizes.
  69. 69. STUDY Cases report was made by neuroophthalmological examination in two patients with parasellar pituitary adenoma before and after surgery. The twelve months follow-up of visual dysfunction includes standard Snellen visual acuity and low contrast number visual acuity.
  70. 70. The presented cases indicate that the low contrast acuity tests in patients with parasellar pituitary adenoma are sensitive indicators. The loss of low contrast visual acuity improved after surgery as did other visual measures, except in cases with significant low contrast deficit at 1.5% contrast. Kruzer, A.R. (1986) “ Contrast Sensitivity Signals Pitutary Adenoma,” Rev. Of.Opt. 123(4), 119
  71. 71. Toxic Chemicals: Several occupational studies have indicated that chronic, airborne exposure adversely affects neurobehavioral functions in workers, particularly visual color discrimination and tasks dependent on rapid visual-information processing Frenette, B.,Mergler, D. And Bowler, R.(1991) “Contrast Sensitivity Loss in Group of Former Microelectronics Workers with Normal Visual Acuity,” Opt. and Sci.,68(7),.
  72. 72. CONTRAST SENSTIVITY AND LASIK Why refractive surgery can affect the quality of vision. there are other factors in the eye, which affect vision quality, that are unrelated to eye focus. These factors can cause the quality of vision to vary greatly, even when a patient has 20/20 or better acuity. Contrast sensitivity is the best method for quantifying the quality of vision
  73. 73. Examples of the change in contrast sensitivity with lasik refractive surgery: The graphs show the pretreatment level of contrast sensitivity (with the patient wearing his or her glasses) and the contrast sensitivity after 1 day, 1 week and 1 month of surgery (with the patient wearing the best correction).
  74. 74. the patient contrast sensitivity does not recover to the presurgery levels. The following graph shows an example of this response in vision quality
  75. 75. Several surgeons have noted that some patients with high levels of myopia (> - 9 diopters) actually improve contrast sensitivity after LASIK surgery. The graph below shows an example. The reason for this improvement in the quality of vision is not completely understood, but it is thought to be due to the poor quality of vision that some patients have through their glasses or contact lenses before LASIK.
  76. 76. Low contrast acuity after lasik
  77. 77. glare testing, which shines a bright light in the patient's eye, reduces pupil size and typically causes vision to improve. The graph below shows the results of a patient tested for contrast sensitivity in darkness and then again with glare. the glare condition dramatically improves the contrast sensitivity
  78. 78. With glare, the yellow filter also improved contrast sensitivity in LASIK patients, but not significantly.  J Refract surgery2005 Mar-Apr;21(2):158-65. Effect of a yellow filter on contrast sensitivity and disability glare after laser in situ keratomileusis under mesopic and photopic conditions. Pérez-Carrasco MJ, Puell MC, Sánchez-Ramos C, López-Castro A, Langa A.

×