Ultrasound of eye - B scan

Presentation on Bscan -introduction, biophysics, technique, pathology

1. BSCAN - Dr Shruti laddha

2. INTRODUCTION B SCAN – b rightness scan N on invasive Provide qualitative and quantitative assessment of the globe and the orbit Image is formed by reflected sound signals from different tissues

3. ULTRASOUND –PAST AND PRESENT 1880-C urie brothers first demonstrated that difference in electric potential could be created by mechanically rubbing tourmaline crystals …this is called as piezoelectric effect . This was first applied in World war 2 for underwater sonar system .

4. 1949-L udwig used ultrasound to detect gallstones. 1956 –Hughes and Mundt – first ophthalmological use –A scan. Baum and Greenwood – two dimensional B mode imaging.

5. WHAT IS ULTRASOUND L ongitudinal sound waves G reater than the upper limit of human hearing that is 20,000Hz Alternate compressions and rarefactions. Just like sound waves – reflected and refracted.

6. PHYSICS Frequency of the wave is inversely proportional to its wavelength. Wavelength is directly proportional to its penetration. So larger the frequency ,less is the penetration and more is the resolution of the resultant echograph

7. Abdominal USG 1-5 MHz Ophthalmic USG (BSCAN ) 8-10 MHz Ultrasound Biomicroscopy (UBM) 20-50 MHz

8. Pulse echo system O phthalmic USG uses high frequency sound waves generated by piezoelectric effect T ransmitted from probe to the eye Strike the intraocular structure get reflected back to the probe Converted into electric signals Display on the monitior

9. Velocity D epends on medium. More denser is the media, faster is the velocity of sound transmission.

10. By Carl Ossoing Medium Velocity(m/sec) water 1480 Aqueous/Vitreous 1532 Soft tissue 1550 Crystalline lens/Cornea 1641 Bone 3500

11. reflectivity W hen sound travels from one medium to another medium of different density, part of the sound wave is reflected from the interface between those media, back into the probe. This is known as Echo . Greater the difference in the density at that interface ,the stronger the echo or the higher the reflectivity.

12. In A SCAN ultrasonography, a thin sound beam is emitted, which passes through the eye and images one small axis of the tissue, the echoes of which are represented as spikes arising from the baseline. The stronger the echo, higher the spike.

13. In BSCAN ultrasonography , an oscillating sound beam is emitted, passing through the eye and imaging a slice of tissue, the echoes of which are represented as multitude of dots that together form an image on the screen. Stronger the echo, brighter the dot. Example: the dots that form the posterior vitreous hyaloid membrane are not as bright as the dots that form the retina .Thus , we can differentiate between posterior vitreous detachment and retinal detachment.

14. ANGLE OF INCIDENCE W hen the probe tip is held perpendicular to the field of interest, more of the echo is reflected back to the probe tip and sent to the display screen. When the probe tip is held obliquely to the field of interest, some of the echo is reflected away from the probe tip, sending back less of it to the display screen.

15. Thus , more obliquely the probe held to the area of interest, more compromised would be the display image. On ASCAN, perpendicular the probe, more steeply rising spike and higher the spike. On BSCAN, perpendicular the probe, brighter the dots on the surface of interest.

16. ABSORPTION Ultrasound is absorbed by every media through which it passes. Higher the density of the media, more is the absorption. That’s why the density of solid lid structure compromises the image of posterior segment imaging as it absorbs a part of the sound wave.

17. Likewise, while performing an ultrasound on eye with denser cataract, more of the sound wave is absorbed, and lesser is able to pass through next media, thereby compromising the spike and the image formed on ASCAN and BSCAN . For this reason, the best image would be produced when the probe is in contact with the sclera rather than the cornea, as it would bypass the crystalline lens and intraocular lens.

18. RESOLUTION The ability to distinguish between adjacent echoes-both axial and lateral. This is enhanced by use of focused sound beam.

19. Axial resolution is related to frequency, piezoelectric crystal shape and dampening material attached to crystal. Shorter the pulse better the axial resolution. The concave shape of the crystal focuses the sound. The focused sound increases axial as well as lateral resolution.

20. AMPLIFICATION This is the important part of signal processing that occurs before the sound wave reached the display monitor. Three types Linear: limited range of echo densities, but can show minor difference within this range Logarithmic: wider range of echo densities ,but does not show minor difference between the echo intensity. S Curve: combine benefit of both the above .

21. gain It is used for increasing or decreasing the amplitude of echoes that are displayed on the screen. Measured in decibels. Does not change the frequency or velocity of the sound . Changes the sensitivity of the instrument’s display screen .

22. Higher gain display weaker echoes like vitreous opacities. Lower gain displays stronger echoes like retina and sclera Better resolution. Typically all examination begin with highest gain, so that no weaker signal is missed ,and then the gain is reduced as necessary for good resolution of stronger signals.

23. High gain Low gain

24. TIME GAIN COMPENSATION This technique is used to enhance the echoes returning from deeper structures by reducing those from the structures closer to the surface, which is typically utilized in studying the orbit.

25. DISPLAY OF SIGNALS The ultrasound signal that is received can be displayed in three ways : A mode , B mode or a combination of the above. Other modification includes three dimensional ultrasound a combination of colour doppler with the BSCAN.

26. A SCAN One dimensional time - amplitude display . The echoes represented by spikes from the baseline. Linear amplification. 10-12MHz Used for axial biometry.

27. Designed to scale acoustic density of retina -100 percent when sound is perpendicular Sclera and choroid also produce 100 percent. Allow tumour cells to be identified and differentiated. In combination with B scan, helps to differentiation of vitreo -retinal membranes

28. Ideally reclined position. • Display and patient’s head should be parallel and in close proximity • topical anaesthesia • methylcellulose-based gel as coupling agent • both eyes should be opened and gaze in the direction being imaged. • B-scans through closed eyelids 1. Ultrasound waves are attenuated due to the soft eyelid 2. Difficult to determine the exact position of the probe on eye. PATIENT PREPARATION

29. B scan Probe Thick with a mark. It as a transducer that moves rapidly back and forth. Emits a focused sound beam at frequency 10 MHz. Methylcellulose is used as a coupling agent. Can be placed over conjunctiva/cornea/lid. Area towards which the mark is directed appear at the top of the display screen.

30. B SCAN PROBE ORIENTATION Transverse Longitudinal Axial

31. Transverse Mark is kept parallel to the limbus Movement of transducer parallel to the limbus . Probe shifted from the limbus to the fornix and sideways. Produce a circumferential slice through several meridian. To detect lateral extent of lesion.

32. Remember, to scan the medial and lateral quadrants of the eye, the probe marker should point superiorly. For the T3 quadrant of the patient's right eye, instruct the patient to look left.  Place the probe on the temporal limbus (L). After obtaining an image of the retina and optic nerve, gently sweep the probe to the fornix (F) to complete evaluation of this quadrant. To view the T3 quadrant of the left eye, the patient should still gaze to the left, but the probe will be placed at the medial limbus, with the marker oriented superiorly. TRANSVERSE VIEW T 3 – QUADRANT CENTERED AT 3 O CLOCK

33. LONGITUDINAL SECTION Transducer kept perpendicular to the limbus. Probe marker kept towards the centre of cornea. Determine the anteroposterior limit of the lesion. Optic disc –lower part of the display screen.

34. Best – demonstration of insertion of the membrane to the optic disc.

35. The LMAC view allows for proper visualization of the macula and optic nerve. Gently place the probe on the nasal aspect of the eye with the patient's gaze directed temporally. Note: For this position, the marker of the probe should be directed  toward the pupil , instead of superiorly. A longitudinal scan is the only scan where this occurs! In this view, the optic nerve will be below the macula. Maneuver the probe to bring the macula into the center of the image to obtain the best resolution. LONGITUDINAL MACULA VIEW(LMAC)

36. AXIAL Patient fixates in primary gaze , probe is placed on the globe directly and directed axially. Easiest to understand as it display lens and optic nerve . Documentation of lesion and membrane in relation to the optic nerve. Hinder resolution of posterior portion of the globe (sound attenuation and refraction) due to crystalline lens and intraocular lens.

37. Depending on the clock hour location of the marker, axial horizontal , axial vertical and axial oblique pictures are obtained

38. Clock position Area screened 3-limbus 9-posterior 3-equator 9-equator 3-fornix 9-anterior 6-limbus 12-posterior 6-equator 12-equator 6-fornix 12-anterior

39. • Six scan screening - four transverse ,one axial and one longitudinal B-scan – the entire posterior segment can be well imaged.

40. INDICATIONS OF BSCAN Media opacity Corneal opacity Hyphaema Small pupil Pupillary membrane Dense cataract Dense vitreous hemorrhage Dense vitreous exudates

41. Differentiation of solid from cystic and homogenous from heterogeneous masses. Examination of retrobulbar soft tissue masses and normally present orbital structures (to differentiate proptosis from exophthalmos). Identification, localization of foreign bodies. Assessment of collateral damage in trauma cases.

42. EVALUATION vi Vitreous Retina Choroid Optic nerve

43. DIFFERENTIATION OF OCULAR LESIONS

44. TOPOGRAPIC ULTRASONOGRAPHY Transverse Scan for lateral extent. Longitudinal Scan for anteroposterior extent. Axial scan useful to establish the lesion’s location in relationship to the optic nerve.

45. Reflectivity is graded by the height of the spike on A-Scan. Internal Structure - Homogeneous cell architecture- Little variation in spikes. Heterogeneous cell architecture- Marked variation. Sound attenuation or acoustic shadowing refers to the diminished or extinguished echo pattern resulting from a strongly reflective or attenuating structure. Calcification of lesions, foreign bodies and bones are among the structures that cause sound attenuation. QUANTITATIVE ULTRASONOGRAPHY

46. Mobility - Movement of a membrane or opacity following a change in gaze. Vascularity- Fast, low-amplitude Blood flow within an flickering intraocular solid lesion. Convection Movement- Slow, continuous movement of blood, layered inflammatory cells, or cholesterol debris. Occurs secondary to convection currents. Seen in eyes with long-standing vitreous haemorrhage. KINETIC ULTRASONOGRAPHY

47. Simultaneously allows Bscan and evaluation of blood flow. The red end of the spectrum-blood moving towards the, transducer. The blue end of the spectrum – flow is moving away. Effective in detecting ocular and orbital tumour vasculature, carotid disease, central retinal artery and vein occlusion neuropathy . COLOUR DOPPLER ULTRASONOGRAPHY

48. 3D ULTRASONOGRAPHY Multiple consecutive Bscan are utilized to create 3 D block. The transducer rotates. Useful in evaluating volume of intraocular lesions and for evaluation of retrobulbar optic nerve.

49. Done using the B-Scan Probe with an immersion scleral shell or a small water filled balloon. Contact B-scan is of little use in evaluating anterior eye structures because there is a 5-mm area directly in front of the probe known as the “dead zone” Patient is asked to fixate in primary gaze when doing axial scan. It allows display of cornea, anterior chamber, iris, lens and retrolental space along the visual axis. BSCAN IMMERSION TECHNIQUE

50. Using scleral shell Latex glove

51. ULTRASOUND BIOMICRSCOPY 35-100 MHz Anatomy of anterior segment, as well as associated pathologies, including angle closure glaucoma, ciliary body cysts, cyclodialysis , foreign bodies in angle neoplasm and angle trauma.

52. vitreous

53. VITREOUS HAEMORRHAGE Most common causes posterior vitreous detachment with or without retinal tear proliferative diabetic retinopathy ocular trauma neovascularisation secondary to retinal vein occlusion.

54. Fresh vitreous h’age appears as diffuse opacities of medium to low reflectivity, with low intensity spikes on A scan

55. As the blood organises, it forms a pseudomembranous surface on B scan ,corresponding to slightly higher intensity spike of A scan .

56. Fresh vitre o u s h e m o rrha g e showi n g di f fuse lo w t o m e di u m ech o es P seu d o m e m br a n e re p resen t ing the or g a n izati o n o f bl o od m o d e rat e l y d e ns e vitre o us h e m o rrha g e

57. Sub h yaloid h e m o rrh a ge L a yered vitre o u s h e m o rrha g e mi m ic s r e ti n a l d e tach m e n t

58. V itr e o u s h e m o rrha g e i n a vitrecto m ize d ey e i n hi g h g ai n In vitrectomised eye, blood remains in liquefied state and often requires use of high gain setting.

59. MIMICKING CONDITIONS Asteroid hylosis - echoluscent gap between echoes and posterior globe wall. Inflammatory echoes- other signs present such as retinochoroidal thickening, exudative RD, optic disc elevation or Tenons space widening seen.

60. Posterior Vitreous Detachment   PVD appears as a thin, smooth membrane that may retain its attachment to the retina at sites of retinal tears, areas of neovascularisation, the optic disc, or the vitreous base. PVD demonstrates significant movement and aftermovements on dynamic B-scan.

61. Asteroid Hyalosis Multiple small spheres of calcium and phospholipid suspended in the vitreous framework and act as distinctive sound reflectors. B scan – diffuse and focal points of high reflective sources with a clear vitreous between asteroid bodies and retina

62. RETINA

63. T ot a l o p e n f u n n e l RD . B-s c a n a t lo w g a i n shows o p e n f u n n el con f i g ur a ti o n a n d o p tic d i sc a t t a chm e n t . A -scan shows 1 0% p e a k correspo n di n g to the R D S – s c ler a , V – vitre o us , R – ret i n a .

64. Retinal echoe-100% spike on A scan. Reflectivity remain equal in all part of membrane as long as the probe is perpendicular to it. Restricted after movements. In case of PVR ,retina loses its mobility and assumes triangular or funnel shaped configuration which can range from open to tightly closed.

65. Mu l ti p l e i n t r a r e ti n al mac r oc y s ts i n a ch r oni c r e ti n al d e t a c hme n t.

66. Arrow shows thin posterior PVD adherent to tent like tractional RD (arrow head). TRD has a tent like configuration that does not extend to ora serrata. Also it exhibits less mobility as compared to RRD due to traction on retina.

67. Diabetic TRD – along disc and vascular arcades. Vascular TRD – equator or anterior to equator.

68. Exudative RD –Smooth , convex surface Shifting SRF in dependent part .

69. In exudative RD caused by photocoagulation –peripheral detachment or isolated pockets, choroidal detachment may also be present. Inflammatory etiology – retinochoroidal thickening Look for tumour mass or granuloma.

70. F E A TURES CH O R OID D E T A C HM E N T RETIN A L D E T A C HM E N T P VD S HA P E D O ME LI N EAR - L O C A TI ON P ERI P HE R Y V ARIA B LE V ARIA B LE A T T A C H MENT T O ONH NO YES V ARIA B LE O THER FINDINGS KIS S ING C H O R OI D AL S F OLDS, B REAKS, P VR C H A N GES P R O MIN E NT INFERIOR L Y A SCA N S P IKE % 90-100 8 0-100 40-90 M O BILI T Y MINIMAL M O DE R A TE MA R KED AFTER M O VEME N T - MINIMAL MA R KED

71. B - s c an s h o w s P V D (ar r ow) , cho r o i da l d e t achme n t (ar r owhea d ) , and vit r eous he m orrha g e ( V H) . A - s c an s h o w s the cha r ac t eri s t i c dou b le pea k o n i n it i al sp i k e Th e p r ob e mu s t b e pe r pend i cu l ar t o se e the doub le peak

72. Se r ou s ch o r o i da l d e t a c hme n t. T w o cho r o i d al d e t a c hme n ts with echo luce n t su b cho r o i d al se r ou s f l u i d (SF). Hemorrhag ic cho r o i d al d e t a c hme n t . “kiss i n g ” cho r o i d al d e t a c hme n t with den s e opa c i t i es i n the su p r a c ho r o i d al spac e i n d i ca t i v e o f hemo r r h a g e (SH).

73. Retinoschisis- B scan- thin ,dome shaped membrane A scan –thin 100 % spike seen just anterior to retina

74. POST SURGICAL CHANGES

75. Scleral buckle- Bscan showing scleral indentation. Produce convex indentation of ocular wall and strong sound attenuation due to extremely high reflectivity of buckling material.

76. E chog r aph i c el o n g a ti o n o f t h e v i t r eous c a v i ty b y s i l i c on e o i l and l i m i t ed v is i b i l i ty o f po s t er io r ocu lar s tr u ctu r es – acoustic elongation F o ll o wi n g r em o v al o f s i l i c on e o il . f e w d r op l e ts o f o il th a t r ema i n i n the e y e a r e v is i b l e as hi ghly r e flecti v e s u r f a c es ( ar r owheads) B – sc le r al b uckle

77. BSCAN-arrow head shows probable meniscus of gas. No structures are seen behind the bubble due to extensive shadowing.

78. INTRAOCULAR TUMOURS

79. R e t inoblas t om a Sol i d t u mo r ar i sing f r om the r etinal l a y er obl i t e r ating the vit r eous c a vi t y . Calc i f icati o n within the t u mo r mas s i s typ i ca l of r etinobl a s t oma shad o wing ef f ect behin d the lesion i n the o r bita l mas s . C o n c om i tant R D m a y b e p r esent. A sca n - hi g h r e f lect i vi t y , v ascularity and absen c e of af t er m o v ements

80. D i f f e r e n tial d iagn o s is o f w h i t e r e f l e x

81. PERSISTENT FETAL VASCULATURE First few weeks of life Unilateral Associated ocular anomalies - microphthalmos, shallow AC, axial length shortening Retrolental fibrovascular mass that cause ciliary body process to rotate inwards But unlike retinoblastoma, no discrete mass visualised.

82. P e r s i s t e n t f e t al v as c ul a tu r e (PFV) . T aut, th ic k ened v i t r eous ban d adhe r e n t t o the s l i g h tly el e v at ed o p tic disc

83. Coat’s Disease Young males 4-10 years of age Early stage- localised focal retinal detachments Advanced stage-total exudative retinal detachment. Yellow cholesterol deposition in subretinal space - xanthocoria , much less reflective than calcium crystals .

84. Coat’s Disease Unlike retinoblastoma ,no distinct mass seen below the retinal detachment.

85. UVEAL MELANOMA

86. Cho r o i d al melanom a . C l i ni c al pho t o g r aph sh o wi n g l a r g e, p art i al l y amelanot i c dome -sha p ed cho r o i d al mass. B -s c an r e v eals a mu sh r oom -s hape d cho r o i d al mass th a t has b r o k en th r ough Bruch ’ s memb r ane (ar r o w s) t ouchi n g the po s t er i or sur f a c e o f the l e n s

87. A s t r oc y t i c hamar t oma . C l i n i c al p h o t og r aph o f per i p ap i l la r y c al cif i e d a s t r oc y t i c hamar t om a . B -s c an demon s t r a ti n g c alci f i ca ti o n nea r o p tic dis c ( ar r o w).

88. Ocula r I n flamm a t o r y Diseases

89. A n t. V i tr i tis - Mi ld t o mode r at ely dens e v i t r eous opa c i t i es a nt er io r t o t h e po s t er ior v i t r eous d e t a c hme n t ( ar r o w s ) a n d v ery mi l d sub h y al o id opa c i t i es

90. B -s c an demon s t r a ti n g mar k ed, di f fuse th ic k en i n g o f the po s t er i o r fu n d us and sc le r a ( ar r o w s ) with a th i n ban d o f l o w r e flect i v i ty i n T enon ’ s spac e (b lack ar r o w s ) i nd i ca ti v e o f po s t er io r sc ler i ti s . D iagno s tic A -s c an sh o wi n g hi ghly r e f l ecti v e t h i c k en in g o f the po s t er ior fundu s and sc le r a

91. “ T -si g n” in p o steri o r scl e riti s. A x i a l B -scan sh o w s p o steri o r scl e ral thick e n i n g a n d l o w refl e ctive i n filtrate b e h i n d the pe ri p ap i l l a ry sc le ra an d o p tic ne rve cre a ti n g the cl a ss i c a l “ T - si g n ” ( a rr o w s). A x i a l B - sc a n s ho w i n g m a rk e d th i ck en i n g o f th e sclera w it h o n l y a v e ry thin b a n d o f l o w refl e ctivity b e h i n d the p e ri p a p i l l a ry scl e ra (arr o w s ).

92. OCULAR TOXOCARIASIS Characteristic pseudocystic degeneration of peripheral vitreous. Mild to moderately elevated granulomatous lesions, that can be calcified. Vitreous membrane extending from granulomatous lesion to posterior pole. Posterior tractional retinal detachment .

93. OCULAR TOXOPLASMOSIS Intravitreal punctiform echoes. Thickening of posterior hyloid . Partial or total PVD. Focal retinochoroidal thickening.

94. T o x opl asmosi s . Mar k ed v i t r eous ha z e w i th t o x opl asmosis l e s i o n s o f the fu n du s . B- s c an a t a l o w g ain de m on s t r a ti n g a po s t er io r v i t r eous d e t a c hme n t ( ar r o whead) and a dom e -sha p ed, e l e v at ed l e s i o n o f the fu n d us (ar r o w ).

95. V o g t – K o y ana g i – Ha r ada s y n d r ome . Axial B -s c an sh o wi n g mar k ed cho r o i d al th i c k en i n g ( ar r o w) a n d a se r ou s r e ti n al d e t a c hme n t ( ar r o whead).

96. Axial B -s c an a t a l o w g ain sh o wi ng mar k ed th i c k en i n g o f t h e po s t er ior fu n du s ( ar r o w s ). T r an s v e r s e B -s c an a t a hi gh g ain sh o wi ng den s e, cl um p ed v i t r eous opa c i t i es adjace n t t o the thic k ened cho r o id ( ar r o w s)

97. ENDOPHTHALMITIS Low reflective vitreous echoes- dot or cobweb shaped. More severe cases- thick membrane like echoes. PVD may or may not be present. As PVD develops in eye with endophthalmitis, TRD like picture may develop - this is due to thickened inflamed posterior hyaloid.

98. Endop h thal m i t i s . T r an s v e r s e B -s c an sh o wi n g mar k ed mem b r ane f orm a ti on ( ar r o w) th r oughou t the v i t r eous spac e and mar k ed, i r r egular fu n du s th i c k en i ng (sma l l a r r o w s)

99. O p ti c Ne r v e Diseases

100. Normal r e t r obulb a r o p tic ne r v e m e asu r e m e n ts M easu r ed in t w o l o ca t i ons 3 mm po s t eri o r t o the ne r v e hea d and as cl os e as poss i b le t o the orb i t al ap e x Nor m al - 2 . 2 t o 3.3 mm in diameter - v ari a t i o n c an occur A d i f f e r ence o f ≥0.5 mm between two eyes m a y indi c a t e an abnormal th i ckne s s in one eye.

101. 30 ° t e s t Inc r eas e d suba r achno i d f l u id c an b e d i f f e r e n t ia t ed f r o m thic k en in g of the pa r enc h yma or per i n eu r al she a ths Optic nerve per i neu r al sh e a ths mea s u r ed a n t eri o r ly and po st eri o r ly I n pr i m a r y g a z e 30 ° l a t e r al g a z e

102. When eye fixates laterally, the optic nerve sheath are stretched and subarachnoid fluid is spread over larger area. A dec r e a s e i n d iame t er of > 1 % i n l a t e r al g a z e is a p os i t i v e 3 ° test which is due to increased subarachnoid fluid.

103. P os it i v e 30° t e s t with di agno s tic A-s c an wh ile the e y e i s i n pr i ma r y g a z e with an en l a r g ed r e t r ob u l b ar o p t i c ne r v e (4.8 mm ) W h en the e y e i s f i x at ed 30° l a t e r al l y , a mar k ed dec r ease i n the s i z e o f the r e t r obulba r o p tic ne r v e (3.5 mm) 4.8 3.5

104. Bur i ed o p tic ne r v e hea d dr u se n . Fun d u s pho t og r aph sh ow s o p tic ne r v e head e l e v a t i o n and a b se n ce o f o p t i c cup m i m i cki n g pap i l lede m a. B -s c an sh o w s hi ghly c alci fied, r oun d dr u se n a t the with shad o wi ng . P seudopapill e dema 3 .2

105. D i agno s tic A - s c an sh ow s norma l r e t r obulba r o p tic ne r v e d iam e t er measur i n g 3.2 mm

106. O p tic dis c c o l obom a . Fun d u s pho t og r aph and Long itu d i n al B -s c an. No t e v i t r eous hemorrha g e, a sha l l o w r e ti n al d e t a c hme n t ( ar r o w) a n d c o l obom a a t the i n f er io r portio n o f the o p tic ne r v e hea d ( ar r o whead)

107. Fu n d us p h o t og r aph sh o wi n g c on g e s t i o n and e l e v a t i o n o f the r i g h t o p t i c d i sc Nor m al c o n t r al at e r al l e f t o p tic disc

108. D i agno s tic A-s c an sh ow s th i c k en i ng o f rig h t o p tic ne r v e w i th r e t r obulbar diam e t er o f 4.50 mm. 3 ° t e s t w as ne g a t i v e f o r su ba r achno i d f l u i d A -s c an o f norma l l e f t o p tic ne r v e w i th r e t r obulba r diam e t er o f 2.32 mm 4.5 2.3

109. THANK YOU