VISUAL FIELDS. Dr. Cesar Carrillo Sight For All

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2 VISUAL FIELDS Dr. Cesar Carrillo Sight For All **Disclaimer** The images contained in this presenta;on are not my own, they can be found on the web or ophthalmology books

3 VISUAL FIELDS The field of vision is defined as the area that is perceived simultaneously by a fixa;ng eye The limits are:! 60 superior field! 75 inferior field! 110 temporally! 60 nasally.

4 NORMAL VISUAL FIELD

5 NORMAL VISUAL FIELD

6 VISUAL FIELDS Traquair, described an island of vision in the sea of darkness The island represents the perceived field of vision, and the sea of darkness is the surrounding areas that are not seen In the light- adapted state, the island of vision has a steep central peak that corresponds to the fovea

7 VISUAL FIELDS

8 VISUAL FIELDS The hill of vision whose peak corresponded to the fovea and whose slopes represented the gradual reduc;on in sensi;vity towards the periphery of the re;na un;l the sea of blindness is reached

9 VISUAL FIELDS The contour of the island of vision relates to both the anatomy of the visual system and the level of re;nal adapta;on The highest concentra;on of cones is in the fovea, and most of these cones project to their own ganglion ceil This one- to- one ra;o between foveal cone and ganglion cell results in maximal resolu;on in the fovea.

10 VISUAL FIELDS Binocularly, the two monocular visual fields overlap, resul;ng in a stereoscopic zone which is approximately 120 degrees in the horizontal dimension The extreme temporal periphery of the binocular field is seen monocularly

11 VISUAL FIELDS The re;nal image of the visual field is upside down and back to front The projec;on of the visual field is such that the superior visual field corresponds to the inferior re;na and vice versa The temporal component of the visual field corresponds to the nasal re;na and vice versa

12 VISUAL FIELD ANALYSIS Gross perimetry (confronta;on) Central visual func;on (Amsler chart) Kine;c perimetry (Goldman) Sta;c perimetry (Automated)

13 CONFRONTATION FIELD TESTING Provides a gross assessment of the pa;ent s visual field using a comparison of the pa;ent s visual field with the examiner s field using simple targets such as a 15 mm diameter red or 4 mm white bead at the end of a s;ck or the examiner s fingers

14 CONFRONTATION FIELD TESTING One form of confronta;on involves the use of a target moved along an imaginary flat plane between and perpendicular to the gaze of the pa;ent and the prac;;oner This obviously will not allow the temporal extent of field to be measured, but will allow the prac;;oner to confirm that any areas they see can also be seen by the pa;ent

15 CONFRONTATION FIELD TESTING The pa;ent and examiner have corresponding eyes closed and the pa;ent looks at the examiner s nose The pa;ent s fields are checked against the examiner own Used by neurologists in inves;ga;ng possible neurological lesions

16 CONFRONTATION FIELD TESTING From a visual field screening point of view this test has been shown to be insensi;ve to all but gross field defects such as homonymous hemianopias when compared to automated perimetry If you suspect that a pa>ent may have a visual field defect you should refer for automated field tes>ng rather than relying on the results of a confronta>on test

17 CONFRONTATION FIELD TESTING Procedure: 1.Explain to the pt. (you are going to measure the area over which they can see rather than how well they can see) 2.Sit between 66 cm and 1 m, facing the pa;ent at the same height as the pa;ent 3.Ask the pt. to remove any glasses and occlude their le` eye with their palm 4.Occlude your right eye 5.Instructs the pa;ent to focus on the ;p of your nose, while you focuses on the pa;ent's nose

18 CONFRONTATION FIELD TESTING 6. Show the pt. the bead- on- a- s;ck and explain that you are going to move it inwards from outside the field of view and you want the pt. to indicate when they can first see the target. Explain that you will con;nue to move the target into the centre of their vision and you want them to indicate if it disappears or fades at any point 7. Hold the bead- on- a- s;ck in a plane equidistant between you and the pa;ent and outside your field of view along one of the eight principal radial meridians. Slowly move the bead inwards un;l the pa;ent reports it is just seen. Compare this point to the point when you first saw the target. Then slowly move the target towards fixa;on and ask the pa;ent to indicate if it disappears or becomes less dis;nct 8. Repeat this procedure for all eight radial meridians. Watch that the pt. does not lose fixa;on. 9. Repeat for the other eye

19 AMSLER CHARTS Is a rapid, qualita;ve technique designed to test the central 10 of the visual field Each square is 5mm subtending 1 at 30cm Pa;ents with AMD and taking chronic medica;ons

20 AMSLER CHARTS

21 AMSLER CHARTS

22 AMSLER CHARTS

23 AMSLER CHARTS

24 AMSLER CHARTS

25 AMSLER CHARTS

26 KINETIC PERIMETRY In kine;c perimetry, a s;mulus is moved from a nonseeing area of the visual field to a seeing area along a set meridian The procedure is repeated with the use of the same s;mulus along other meridians, usually spaced every 15

27 KINETIC PERIMETRY In kine;c perimetry, one ahempts to find loca;ons in the visual field of equal re;nal sensi;vity. By joining these areas of equal sensi;vity, an isopter is defined The luminance and the size of the target is changed to plot other isopters In kine;c perimetry, the island of vision is approached horizontally Isopters can be considered the outline of horizontal slices of the island of vision

28 GOLDMANN PERIMETER The most widely used instrument for manual perimetry It is a calibrated bowl projec;on instrument with a background intensity of 31.5 apos;lbs (asb), which is well within the photopic range The size and intensity of targets can be varied to plot different isopters kine;cally and determine local sta;c thresholds

29 GOLDMANN PERIMETRY

30 GOLDMANN PERIMETRY

31 STATIC PERIMETRY The size and loca;on of the test target remain constant The re;nal sensi;vity at a specific loca;on is determined by varying the brightness of the test target The shape of the island is defined by repea;ng the threshold measurement at various loca;ons in the field of vision

32 AUTOMATED PERIMETRY The introduc;on of computers and automa;on heralded a new era in perimetric tes;ng Sta;c tes;ng can be performed in an objec;ve and standardized fashion with minimal perimetrist bias A quan;ta;ve representa;on of the visual field can be obtained more rapidly than with manual tes;ng

33 AUTOMATED PERIMETRY The computer allows s;muli to be presented in a pseudorandom, unpredictable fashion Pa;ents do not know where the next s;mulus will appear, so fixa;on is improved, thereby increasing the reliability of the test Random presenta;ons also increase the speed with which perimetry can be performed by bypassing the problem of local re;nal adapta;on, which requires a 2- second interval between s;muli if adjacent loca;ons are tested

34 AUTOMATED PERIMETRY The differen>al light threshold Sta;c computerized perimetry measures re;nal sensi;vity at predetermined loca;ons in the visual field These perimeters measure the ability of the eye to detect a difference in contrast between a test target and the background luminance

35 AUTOMATED PERIMETRY The differen;al light threshold is designated as the dimmest target seen 50% of the ;me Suprathreshold s;muli are brighter than threshold s;muli, and they will be seen more than 50% of the ;me Infrathreshold s;muli are dimmer than threshold s;muli, and they will be seen less than 50% of the ;me

36 AUTOMATED PERIMETRY Threshold at a specific re;nal loca;on can be measured directly from a frequency- of- seeing curve The frequency- of- seeing curve is generated by tes;ng one re;nal loca;on mul;ple ;mes with different s;mulus intensi;es The frequency- of- seeing curve is the graph of the percentage of s;muli seen at each intensity level Threshold is read off the graph at the 50th percen;le

37 AUTOMATED PERIMETRY Frequency of seeing curve S;muli of varying intensi;es are presented mul;ple ;mes at one re;nal loca;on Threshold is designated as the dimmest s;mulus seen 50% of the ;me

38 AUTOMATED PERIMETRY It is imprac;cal to perform frequency- of- seeing curves at the large number of loca;ons required to assess the visual field accurately for glaucomatous damage Therefore, a staircase, or bracke;ng, strategy is used to es;mate threshold Most commonly, a 4-2 algorithm is employed

39 AUTOMATED PERIMETRY Tes;ng starts with either a suprathreshold or an infrathreshold s;mulus For a suprathreshold s;mulus, the intensity of the s;mulus is decreased in 4- db steps un;l the s;mulus is no longer seen (threshold is crossed) Threshold is crossed a second ;me by increasing the s;mulus intensity in 2- db steps un;l the s;mulus is seen again

40 AUTOMATED PERIMETRY The Octopus perimeter es;mates threshold as the average of the last seen and unseen s;mulus intensi;es The Humphrey perimeter uses the intensity of the last seen s;mulus as threshold

41 AUTOMATED PERIMETRY The 4-2 bracke>ng strategy to determine threshold The s;mulus intensity is varied so that threshold is crossed twice, first using 4- db steps and then 2- db steps The s;mulus intensity was decreased by 4 db The second s;mulus also was seen, so the intensity again was decreased by 4 db The third s;mulus crossed the threshold (first crossing) and was not seen The s;mulus intensity was increased by 2 db

42 AUTOMATED PERIMETRY The fourth s;mulus was not seen, so the intensity was increased by 2 db The fi`h s;mulus crossed the threshold (second crossing) and was seen Threshold is either the intensity of the last seen s;mulus (HFA) or the average of the last seen and unseen s;mulus (Octopus) The profile of the hill of vision is represented by the threshold at each loca;on

43 AUTOMATED PERIMETRY The 4-2 bracke>ng strategy to determine threshold

44 AUTOMATED PERIMETRY Apos>lbs and decibels In perimetry, the luminance of test targets is measured in apos;lbs An apos;lb is an absolute unit of luminance and is equal to candela/m2, or 0.1 mililambert The decibel scale is a rela;ve scale created by the manufacturers of automated perimeters to measure the sensi;vity of the island of vision

45 AUTOMATED PERIMETRY The decibel scale is an inverted logarithmic scale Zero decibels is set as the brightest s;mulus that the perimeter can produce The decibel scale is not standardized because the maximal luminance varies between instruments

46 AUTOMATED PERIMETRY

47 AUTOMATED PERIMETRY Sensi>vity vs threshold As one ascends the hill of vision toward the fovea, the sensi;vity of the re;na increases, dimmer targets will become visible, and the brightness of the target at threshold will decrease Therefore, as re;nal sensi;vity increases, the differen;al light threshold measured in apos;lbs decreases

48 AUTOMATED PERIMETRY This inverse rela;onship between re;nal sensi;vity and threshold holds true throughout most of visual psychophysics In automated perimetry, however, threshold is recorded in the inverted decibel scale, and dimmer targets have higher decibel values Therefore, threshold in decibels is directly propor>onal to re>nal sensi>vity

49 AUTOMATED PERIMETRY Single- Level Suprathreshold Test A s;mulus that is 2 to 6 db brighter (suprathreshold) than the expected hill of vision is used to test mul;ple loca;ons in the visual field Results are recorded simply as seen (normal) or not seen (defect) On the Humphrey perimeter, this is called the threshold- related strategy

50 AUTOMATED PERIMETRY Two- Level Suprathreshold Test These tests o`en are referred to as three- zone tests because the visual field is classified into three categories: normal, rela;ve defect, and absolute defect

51 AUTOMATED PERIMETRY Threshold programs Most pa;ents with glaucoma should undergo tests that measure the differen;al light threshold The following strategies are available on the Humphrey Fields Analizer (HFA): Full Threshold (Normal Strategy)

52 AUTOMATED PERIMETRY Full Threshold (Normal Strategy) The differen;al light threshold is determined at every point in the visual field with the use of the 4-2 bracke;ng algorithm This strategy is the most accurate way of evalua;ng and following glaucomatous visual field defects. However, it is the most ;me- consuming method

53 AUTOMATED PERIMETRY How can test >me be minimized? The closer the ini;al s;mulus is to the actual threshold, the faster the test will be Humphrey and Octopus use a "region growing" technique to determine the star;ng level for each point The threshold is measured at one spot in each quadrant Adjacent loca;ons are tested with appropriate star;ng thresholds

54 HUMPHREY PERIMETER Projec;on type automated sta;c perimeter Most popular, consistency of basic hardware, constant up grada;on of the so`ware on the basis of clinical feedback from the ophthalmologists Viewing distance- 33cms Background illumina;on- 31.5asb Sta;c mode, newer models - kine;c

55 HUMPHREY PERIMETER Data storage: STATPAC: computerised sta;s;cal package Comparison of pa;ents results with age matched normal data Pa;ents own baseline with follow up data Newer HFA series: database of stable glaucoma pa;ents for glaucoma change probability analysis

56 HUMPHREY PERIMETER On the Humphrey perimeter, if thresholds are more than 5 db from expected values, the loca;on is retested. The second result is printed below the first in parentheses

57 HUMPHREY PERIMETER Fastpac Full Threshold The differen;al light threshold is determined at every point in the visual field; however, the 4-2 bracke;ng strategy is not used Instead, threshold is measured using 3 db steps, and the threshold is crossed one ;me only The accuracy and reliability of the Fastpac strategy is currently under inves;ga;on

58 HUMPHREY PERIMETER Standard automated perimetry is usually performed with one of four similar threshold measuring test: 30-2 SITA Standard 24-2 SITA Standard 30-2 SITA Fast 24-2 SITA Fast

59 HUMPHREY PERIMETER 30-2 payern: "76 test point loca;ons "Cover de central 30 field "Grid of points 6 apart 24-2 payern: "54 test point loca;ons "Central field out to 24 (except nasally 30 )

60 HUMPHREY PERIMETER SITA Standard Offers very high accuracy Rela;vely short test ;me (4-8 per eye) SITA Fast Very fast threshold test (2-6 per eye) Diagnos;c sensi;vity similar to that of the Full Threshold test

61 GLOBAL INDICES Mean devia>on (MD) Reflects the overall depression or eleva;on of the visual field The devia;on from the age- matched normal value is calculated at each loca;on in the visual field The mean devia;on is simply the weighted average of the devia;on values for all loca;ons tested Like the mean sensi;vity, the mean devia;on is most sensi;ve to diffuse changes and is less sensi;ve to small localized scotomas

62 GLOBAL INDICES PaYern standard devia>on (PSD) Such irregulari;es can be due to a localized visual field defect or to pa;ent variability The corrected loss variance or corrected pahern standard devia;on provides a measure of the irregularity of the contour of the hill of vision that is not accounted for by pa;ent variability (short- term fluctua;on) It is increased when localized defects are present

63 GLAUCOMATOUS VISUAL FIELD DEFECTS Early defect: Neither extensive nor near fixa;on Mean devia;on index (MD) beher than - 6dB On PD plot: 1.<25%(18) points are below 5% level 2.< 10 points below 1% level Central 5 - no points having less than 15dB sensi;vity

64 GLAUCOMATOUS VISUAL FIELD DEFECTS

65 GLAUCOMATOUS VISUAL FIELD DEFECTS

66 GLAUCOMATOUS VISUAL FIELD DEFECTS Moderate defect: MD<- 12dB 1.PD- <50%( 37) points < 5% and < 20 points <1% Central 5 - no points with 0dB Only one hemifield may have a point in central 5 with <15dB sensi;vity

67 GLAUCOMATOUS VISUAL FIELD DEFECTS

68 GLAUCOMATOUS VISUAL FIELD DEFECTS

69 GLAUCOMATOUS VISUAL FIELD DEFECTS Severe defect: Any of the following: 1.MD plot >- 12dB 2.PDplot: >37 points depressed below<5% >20 points depressed below 1% Any point in central 5 has sensi;vity of 0dB Central 5 - points <15dB in both hemispheres

70 GLAUCOMATOUS VISUAL FIELD DEFECTS

71 GLAUCOMATOUS VISUAL FIELD DEFECTS

72 GLAUCOMATOUS VISUAL FIELD DEFECTS Any clinically or sta;s;cally significant devia;on from the normal shape of the hill of vision can be considered a visual field defect In glaucoma, these defects are either diffuse depressions of the visual field or localized defects that conform to nerve fiber bundle paherns

73 GLAUCOMATOUS VISUAL FIELD DEFECTS Diffuse depression Results from an overall or widespread sinking of the island of vision and may reflect diffuse loss of nerve fibers of the re;na Diffuse depression is a nonspecific sign that can be caused by many e;ologies other than glaucoma

74 GLAUCOMATOUS VISUAL FIELD DEFECTS By far the most common reason for a diffuse depression is lens opacity Other factors include other media opaci;es, miosis, improper refrac;on, pa;ent fa;gue, inahen;veness or inexperience with the examina;on, ocular anomalies, and age It is difficult to ahribute diffuse depression specifically to a glaucomatous process

75 GLAUCOMATOUS VISUAL FIELD DEFECTS In automated perimetry, diffuse depression results in rela;ve defects across the en;re visual field Early diffuse depression o`en is difficult to detect because thresholds may remain within the normal range, but they may be depressed from previous examina;ons or the baseline status

76 GLAUCOMATOUS VISUAL FIELD DEFECTS Localized visual field bundle defects In glaucoma result from damage to the re;nal nerve fiber bundles Because of the unique anatomy of the re;nal nerve fiber layer, axonal damage causes characteris;c paherns of visual field damage

77 GLAUCOMATOUS VISUAL FIELD DEFECTS The superior and inferior poles of the op;c nerve head are most vulnerable to glaucomatous damage It has been postulated that these areas may be watershed areas at the junc;on of the vascular supply from adjacent ciliary vessels Ultrastructural examina;on of the lamina cribrosa shows that the pores in the superotemporal and inferotemporal areas are larger The large pores may make these regions more vulnerable to compression

78 GLAUCOMATOUS VISUAL FIELD DEFECTS

79 GLAUCOMATOUS VISUAL FIELD DEFECTS Paracentral defects Circumscribed paracentral defects are an early sign of localized glaucomatous damage The defects may be absolute when first discovered, or they may have deep nuclei surrounded by areas of less dense involvement The dense nuclei o`en are numerous along the course of the nerve fiber bundle

80 GLAUCOMATOUS VISUAL FIELD DEFECTS

81 GLAUCOMATOUS VISUAL FIELD DEFECTS Arcuate scotoma More advanced loss of arcuate nerve fibers leads to a scotoma that starts at or near the blind spot, arches around the point of fixa;on, and terminates abruptly at the nasal horizontal meridian An arcuate scotoma may be rela;ve or absolute

82 GLAUCOMATOUS VISUAL FIELD DEFECTS Arcuate scotoma In the temporal por;on of the field, it is narrow because all of the nerve fiber bundles converge onto the op;c nerve The scotoma spreads out on the nasal side and may be very wide along the horizontal meridian

83 GLAUCOMATOUS VISUAL FIELD DEFECTS

84 DIFFERENTIAL DIAGNOSIS OF ARCUATE SCOTOMAS

85 GLAUCOMATOUS VISUAL FIELD DEFECTS

86 GLAUCOMATOUS VISUAL FIELD DEFECTS Because of the anatomy of the horizontal raphe, all complete arcuate scotomas end at the nasal horizontal meridian A steplike defect along the horizontal meridian results from asymmetric loss of nerve fiber bundles in the superior and inferior hemifields

87 GLAUCOMATOUS VISUAL FIELD DEFECTS Nasal step defects may be evident in some isopters but not in others, depending on which nerve fiber bundles are damaged The width of the nasal step also varies Nasal steps frequently occur in associa;on with arcuate and paracentral scotomas, but a nasal step also may occur in isola;on Approximately 7% of ini;al visual field defects are peripheral nasal step defects

88 GLAUCOMATOUS VISUAL FIELD DEFECTS Temporal wedge defects Damage to nerve fibers on the nasal side of the op;c disc may result in temporal wedge- shaped defects These defects are much less common than defects in the arcuate distribu;on Occasionally, they are seen as the sole visual field defect Temporal wedge defects do not respect the horizontal meridian

89 GLAUCOMATOUS VISUAL FIELD DEFECTS

90 GLAUCOMATOUS VISUAL FIELD DEFECTS Ini>al localized visual field defects may be either rela>ve or absolute scotomas with a nasal step isolated paracentral defects isolated nasal steps sector defects paracentral or arcuate scotomas arcuate blind spot enlargement temporal defects

91 GLAUCOMATOUS VISUAL FIELD DEFECTS Blind spot changes Enlargement Ver;cal elonga;on of the blind spot may occur with the development of a Siedel scotoma, an early arcuate defect that connects with the blind spot Peripapillary atrophy, which frequently accompanies glaucomatous damage, par;cularly in elderly pa;ents, also may cause enlargement of the blind spot Baring

92 GLAUCOMATOUS VISUAL FIELD DEFECTS Baring of the blind spot may be physiologic or pathologic Physiologic baring of the blind spot is an ar;fact of kine;c perimetry The inferior re;na is less sensi;ve than the superior re;na, so an isopter plohed at threshold in the inferior central re;na may result in superior baring of the blind spot Physiologic baring of the blind spot usually is confined to a single central isopter in the superior visual field

93 ARTIFACTS Lid Lens rim- too far or the eye is not centered Refrac;ve error Learning effect Pupillary size Rapid fa;gue

94 REFRACTIVE ERRORS Uncorrected refrac;ve errors cause defocusing of the test target and apparent depression of re;nal sensi;vity Each diopter of uncorrected refrac;on causes a db depression of re;nal sensi;vity The proper near add refrac;on, as determined by the pa;ent's age and the diameter of the perimeter's cupola, must be used This lens must be posi;oned properly to prevent ar;factual defects caused by the rim of the lens

95 MEDIA OPACITIES Media opaci;es, such as cataracts, can cause generalized depression of the visual field As cataracts become more dense, visual field defects may appear to worsen It is important to check for changing acuity, worsening of cataracts, and other media opaci;es when analyzing visual fields for progression

96 ASSESSING RELIABILITY False- Posi>ve (FP) A sound cue is given before each s;mulus is presented in automated tests Periodically, the sound cue is given but no test s;mulus is presented A false- posi;ve result occurs if the pa;ent responds to the sound cue alone

97 ASSESSING RELIABILITY False- Nega>ve (FN) A false- nega;ve catch trial is recorded if a pa;ent does not respond at a loca;on that had a measurable threshold earlier in the examina;on A high number of false- nega;ve catch trials may indicate pa;ent inahen;veness and an unreliable visual field The false- nega;ve response rate is higher in eyes with extensive visual field defects than in those with normal visual fields

98 ASSESSING RELIABILITY Fixation losses (FL) Not all fixation losses represent true loss of fixation High fixation loss may indicate, centre of blind spot was slightly mislocated If FP, FN rates and STF are low, then the high FL can be discounted If two baseline fields are similar it can again be discounted Mislocation of the blind spot Macular disease

99 INTER- EYE COMPARISONS The difference in the mean sensi;vity between a pa;ent's two eyes is less than 1 db 95% of the ;me and less than 1.4 db 99% of the ;me Intereye differences greater than these values are suspicious if they are unexplained by nonglaucomatous factors, such as unilateral cataract or miosis

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