Spaceflight Associated Neuro-ocular Syndrome (SANS): Current Clinical Insight & Questions of Interest

Transcription

1 Spaceflight Associated Neuro-ocular Syndrome (SANS): Current Clinical Insight & Questions of Interest Tyson Brunstetter, OD, PhD, MBA, FAAO, FAsMA Captain, Medical Service Corps, U.S. Navy Deputy SANS Clinical Lead Space and Occupational Medicine Branch (SD3) NASA Johnson Space Center TRISH Red Risk School 05 April 2018 Page No. 1

2 William J. Tarver, MD, MPH 1 SANS Clinical Lead Michael Stenger, PhD 1 SANS Research Lead Page No. 2 Shehzad Batliwala, DO 2 Simon J. Clemett, PhD 3 Russell Derrick 4 C. Robert Gibson, OD 5 Steven Laurie, PhD 4 Brandon R. Macias 4 Thomas Mader, MD 4 Sara Mason 6 Mayra Nelman-Gonzalez 4 Clarence Sams, PhD 1 Caroline Schaefer, MPH 6 Wafa Taiym, MS 4 Mary Van Baalen, PhD 1 Julia Wells, RN, BSN 4 1. NASA Johnson Space Center Houston, TX 2. Dean McGee Eye Institute Oklahoma City, OK 3. Jacobs Technology, Inc. Houston, TX 4. KBRWyle Houston, TX 5. Coastal Eye Associates Webster, TX 6. MEI Technologies Houston, TX

3 Page No. 3 What s So Special About the Eye?

4 Only about 1 in diameter, but Provides ~80% of our sensory input Medical Emergency: Life, limb, or eyesight Presents tremendous amount of health information Neurological state (4-of-12 cranial nerves): via eye position, lid position, pupil size & reaction, visual performance Tumor, aneurysm, stroke, etc. Page No. 4

5 Only about 1 in diameter, but Provides ~80% of our sensory input Medical Emergency: Life, limb, or eyesight Presents tremendous amount of health information Neurological state (4-of-12 cranial nerves): via eye position, lid position, pupil size & reaction, visual performance Tumor, aneurysm, stroke, etc. Presence/severity of systemic disease High blood pressure; diabetes; impending stroke; high intracranial pressure; hyperthyroidism; etc. Normal view of eye s posterior pole: Retina; optic nerve head (optic disc); retinal blood vessels; macula Page No. 5

6 Only about 1 in diameter, but Provides ~80% of our sensory input Medical Emergency: Life, limb, or eyesight Presents tremendous amount of health information Neurological state (4-of-12 cranial nerves): via eye position, lid position, pupil size & reaction, visual performance Tumor, aneurysm, stroke, etc. Presence/severity of systemic disease High blood pressure; diabetes; impending stroke; high intracranial pressure; hyperthyroidism; etc. Window to the soul : Astronaut eyes have always been eval d pre/post-flight by NASA Page No. 6

7 Optic nerve, optic nerve head, and retina Central nervous system Behind blood-brain barrier Susceptible to permanent loss Page No. 7

8 Optic nerve, optic nerve head, and retina Central nervous system Behind blood-brain barrier Susceptible to permanent loss Optic nerve Connects eye to brain Bathed in cerebrospinal fluid (CSF) Optic nerve head (ONH) / Optic disc Where optic nerve meets eye Has intracranial pressure (ICP) on backside, intraocular pressure on frontside Optic Nerve Optic Disc Retina Page No. 8

9 Optic nerve, optic nerve head, and retina Retina Converts light energy into neural signals Sends signals through nerve fibers (via disc & optic nerve) brain vision Extremely high metabolism: High demands, low reserves Photorecepter mitochondria operate at ~70-80% capacity Requires reliable, sustained blood supply (O 2, glucose, etc.) Optical Coherence Tomography (OCT) Page No. 9

10 Page No. 10 SANS: Clinical Findings & Definition

11 * * Additional SANS signs not included: Optic nerve (ON) sheath distension, ON kinking/tortuosity, Retinal nerve fiber layer thickening, Retinal folds, Choroidal thickening. Data analysis ongoing Page No. 11

12 * Pre-flight - OD * Additional SANS signs not included: Optic nerve (ON) sheath distension, ON kinking/tortuosity, Retinal nerve fiber layer thickening, Retinal folds, Choroidal thickening. Data analysis ongoing Page No. 12

13 * Pre-flight - OD Post * Additional SANS signs not included: Optic nerve (ON) sheath distension, ON kinking/tortuosity, Retinal nerve fiber layer thickening, Retinal folds, Choroidal thickening. Data analysis ongoing Page No. 13

14 Edema: Accumulation of excess fluid; swelling. Indicates an underlying abnormal condition (pathology) Terrestrially -- Disc edema typically associated w/: Unilateral: Optic neuritis/neuropathy, retinal artery occlusion, extreme hypertension Bilateral: Increase in ICP e.g., Idiopathic intracranial hypertension (IIH) Typically causes symptoms (e.g., for IIH: severe headaches, transient vision loss, double vision, enlarged blind spot, color vision impairment) Edematous CNS neurons can atrophy, lost permanently, depending on severity & duration Good News: So far, no obvious loss of ocular nerve tissue detected in astronauts Fundoscopic image of optic disc OD, R+10 days. Arrows indicate C shaped halo of edema Page No. 14

15 OD OS Pre-flight fundoscopic images of the optic discs OD OS Post-flight images of optic discs, showing: Grade 3 edema OD Grade 1 edema OS 360 o 270 o <x<360 o Page No. 15

16 SANS case definition Diagnosis currently based solely on: Optic disc edema of Frisen grade of 1 (i.e., edema extending 270 o around ONH) as evaluated via retinal photography (fundoscopy) Page No. 16

17 SANS case definition Diagnosis currently based solely on: Optic disc edema of Frisen grade of 1 (i.e., edema extending 270 o around ONH) as evaluated via retinal photography (fundoscopy) SANS Case Range Page No. 17

18 SANS case definition Diagnosis currently based solely on: Optic disc edema of Frisen grade of 1 (i.e., edema extending 270 o around ONH) as evaluated via retinal photography (fundoscopy) Limitations: Ignores other SANS signs & diagnostic tech / Subjective / Binary Page No. 18

19 SANS case definition Diagnosis currently based solely on: Optic disc edema of Frisen grade of 1 (i.e., edema extending 270 o around ONH) as evaluated via retinal photography (fundoscopy) Limitations: Ignores other SANS signs & diagnostic tech / Subjective / Binary 0 Page No. 19

20 * * Additional SANS signs not included: Optic nerve (ON) sheath distension, ON kinking/tortuosity, Retinal nerve fiber layer thickening, Retinal folds, Choroidal thickening. Data analysis ongoing Page No. 20

21 OD Post-flight OS SANS cases: Choroidal thickening due to vessel engorgement induces choroidal (and sometimes retinal) folds Pre-flight OD Post-flight OD Fovea Retina Choroid Page No. 21

22 Retina OD Post-flight OS Pre-flight OD Post-flight OD Fovea Choroid SANS cases: Choroidal thickening due to vessel engorgement induces choroidal (and sometimes retinal) folds Usually run horizontally Can resolve post-flight or persist (for 12+ yrs) So far, no significant impact on best-corrected visual acuity (BCVA) Terrestrially: Assoc. w/ choroidal or orbital tumors, scleritis, IIH Page No. 22

23 * * Additional SANS signs not included: Optic nerve (ON) sheath distension, ON kinking/tortuosity, Retinal nerve fiber layer thickening, Retinal folds, Choroidal thickening. Data analysis ongoing Page No. 23

24 Can resolve post-flight or can persist (for 7+ yrs) Case Example: MRI Pre-flight Page No. 24

25 Can resolve post-flight or can persist (for 7+ yrs) Case Example: 6 days post-flight MRI Page No. 25

26 Can resolve post-flight or can persist (for 7+ yrs) Case Example: ssociated w/ increased intracranial pressure (e.g., IIH); almost always bilateral 1 year post-flight MRI Page No. 26

27 Post-flight questionnaires ( ): 29% of short- & 60% of long-duration mission astronauts report a degradation in vision (especially at near distances) Provided Space Anticipation Glasses Mostly attributable to globe flattening Pre-to-post-flight change Up to +1.75D Like globe flattening, can rebound or persist (7+ years) No loss in BCVA (i.e., 20/20 or better) 6 days post-flight MRI Page No. 27

28 Page No. 28 Common Characteristics of the Cases

29 Common Characteristics of the Cases Almost all were long duration ISS mission crewmembers Is severity related to flight duration?? [If so, what about a 3-yr Mars mission??] Healthy individuals w/ normal medical history & normal pre-flight eye exams Negative for uncontrolled systemic disease ISS cabin Elevated CO 2 : 8-10x terrestrial levels (~ % avg) CO 2 is a potent vasodilator A potential SANS contributor?? None experienced loss in visual performance (e.g., BCVA, color vision, or depth perception) None complained of classic symptoms of idiopathic intracranial hypertension (IIH) (e.g., Severe headaches, transient vision loss/obscurations, double vision, pulsatile tinnitus, etc.) Page No. 29

30 Common Characteristics of the Cases Recent Findings Optic disc changes w/ long-duration spaceflight David Brown, MD SANS Research & Clinical Advisory Panel (RCAP); Retinal specialist, Retinal Consultants of Houston Analyzed 14 crewmembers having complete pre-flight & on-orbit OCT data, ALL showed signs of: Choroidal thickening Venous engorgement Optic disc edema And optic discs tend to expand forward and backward (opposite to IIH) Edema findings also reported by others (e.g., Nimesh Patel, OD, PhD; Brandon Macias, PhD; Steven Laurie, PhD) Page No. 30

31 Source: Mayra Nelman & Simon Clemett

32 Source: Mayra Nelman & Simon Clemett Non-Case w/ subclinical edema

33 Source: Mayra Nelman & Simon Clemett Non-Case w/ subclinical edema

34 Page No. 34 Why is this Happening?

35 Why is this Happening? Microgravity Cephalad fluid shift Cerebral venous congestion (i.e., overfilling & distension) Confounding variables: Resistive exercise / Sodium intake / CO 2 levels / Pharmaceuticals?? Page No. 35

36 Why is this Happening? Microgravity Cephalad fluid shift Cerebral venous congestion (i.e., overfilling & distension)?? SANS Hypothesis #1: Increased intracranial pressure (ICP) Enough to cause an imbalance between ICP & intraocular pressure (i.e., a translaminar pressure gradient) Due to an overall increase in ICP or localized to optic nerve (e.g., Compartmentalization of perioptic subarchnoid spaces local increase in ICP) Hypothesis #2: Venous congestion alters local physiology and/or places direct pressure on retinal axons Hypothesis #3: Individual anatomical/genetic factors e.g., Altered folate-dependent 1-carbon metabolism? Confounding variables: Resistive exercise / Sodium intake / CO 2 levels / Pharmaceuticals?? Page No. 36

37 Page No. 37 SANS Questions of Interest

38 SANS Questions of Interest Is SANS a Male-Only Syndrome? No Only men have been officially diagnosed w/ SANS, but Only 11 USOS women flown in Expeditions 1-53 (i.e., a tiny n ) Female long-duration crewmembers have shown ocular changes Optic disc edema (of some amount) Thickened choroid Globe flattening Refractive error shift Better questions would be: Is SANS prevalence equal btwn males & females (but is being masked by a small female sample size)?? Or, if not equal Are females less severely affected by SANS than males?? Page No. 38

39 Probably Not SANS Questions of Interest Is SANS Less Prevalent in Space-Naïve Astronauts? Page No. 39 All Crew Space Naïve D Edema 15% 17% CWS 10% 11% Scotoma 1.5% 0% R Heme 4% 17% Chor Folds 23% 11% G Flattening 23% 11% Ref Error Δ 19% 11% * Additional SANS signs not included: Optic nerve (ON) sheath distension, ON kinking/tortuosity, Retinal nerve fiber layer thickening, Retinal folds, Choroidal thickening. Data analysis ongoing

40 Probably Not SANS Questions of Interest Is IIH an Adequate Terrestrial Analogue for SANS? Page No. 40

41 SANS Questions of Interest Is IIH an Adequate Terrestrial Analogue for SANS? IIH SANS ONH/Disc Edema YES YES Intracranial Pressure Increased TBD; inconclusive evidence Female : Male 9 : 1 TBD; no females officially diagnosed (0 : 10) ( but changes seen in both sexes!) BMI Obese (>90%) Normal to highly athletic Symptoms Chronic headaches (94%); Transient vision obscuration (68%) None besides near vision complaints Side Bias < 4% unilateral TBD; but gross signs have been right-biased ONH Displacement Gross movement forward Expands forward & backward Retinal : Choroidal Folds >5 : 1; Retinal folds occur first 1 : >5; Choroidal folds occur first Fold Pattern Typically concentric around ONH Typically linear Post-flight MRI Brains displaces downward; no change in size of lateral ventricles Brain displaces upward; lateral ventricles enlarge Page No. 41

42 SANS Questions of Interest Is IIH an Adequate Terrestrial Analogue for SANS? IIH SANS ONH/Disc Edema YES YES Intracranial Pressure Increased TBD; inconclusive evidence Female : Male 9 : 1 TBD; no females officially diagnosed (0 : 10) ( but changes seen in both sexes!) BMI Obese (>90%) Normal to highly athletic Symptoms Chronic headaches (94%); Transient vision obscuration (68%) None besides near vision complaints Side Bias < 4% unilateral TBD; but gross signs have been right-biased ONH Displacement Gross movement forward Expands forward & backward Retinal : Choroidal Folds >5 : 1; Retinal folds occur first 1 : >5; Choroidal folds occur first Fold Pattern Typically concentric around ONH Typically linear Post-flight MRI Brains displaces downward; no change in size of lateral ventricles Brain displaces upward; lateral ventricles enlarge Page No. 42

43 SANS Questions of Interest Is IIH an Adequate Terrestrial Analogue for SANS? IIH SANS ONH/Disc Edema YES YES Intracranial Pressure Increased TBD; inconclusive evidence Female : Male 9 : 1 TBD; no females officially diagnosed (0 : 10) ( but changes seen in both sexes!) BMI Obese (>90%) Normal to highly athletic Symptoms Chronic headaches (94%); Transient vision obscuration (68%) None besides near vision complaints Side Bias < 4% unilateral TBD; but gross signs have been right-biased ONH Displacement Gross movement forward Expands forward & backward Retinal : Choroidal Folds >5 : 1; Retinal folds occur first 1 : >5; Choroidal folds occur first Fold Pattern Typically concentric around ONH Typically linear Post-flight MRI Brains displaces downward; no change in size of lateral ventricles Brain displaces upward; lateral ventricles enlarge Page No. 43

44 SANS Questions of Interest Is IIH an Adequate Terrestrial Analogue for SANS? IIH SANS ONH/Disc Edema YES YES Intracranial Pressure Increased TBD; inconclusive evidence Female : Male 9 : 1 TBD; no females officially diagnosed (0 : 10) ( but changes seen in both sexes!) BMI Obese (>90%) Normal to highly athletic Symptoms Chronic headaches (94%); Transient vision obscuration (68%) None besides near vision complaints Side Bias < 4% unilateral TBD; but gross signs have been right-biased ONH Displacement Gross movement forward Expands forward & backward Retinal : Choroidal Folds >5 : 1; Retinal folds occur first 1 : >5; Choroidal folds occur first Fold Pattern Typically concentric around ONH Typically linear Post-flight MRI Brains displaces downward; no change in size of lateral ventricles Brain displaces upward; lateral ventricles enlarge Page No. 44

45 SANS Questions of Interest Is IIH an Adequate Terrestrial Analogue for SANS? IIH SANS ONH/Disc Edema YES YES Intracranial Pressure Increased TBD; inconclusive evidence Female : Male 9 : 1 TBD; no females officially diagnosed (0 : 10) ( but changes seen in both sexes!) BMI Obese (>90%) Normal to highly athletic Symptoms Chronic headaches (94%); Transient vision obscuration (68%) None besides near vision complaints Side Bias < 4% unilateral TBD; but gross signs have been right-biased ONH Displacement Gross movement forward Expands forward & backward Retinal : Choroidal Folds >5 : 1; Retinal folds occur first 1 : >5; Choroidal folds occur first Fold Pattern Typically concentric around ONH Typically linear Post-flight MRI Brains displaces downward; no change in size of lateral ventricles Brain displaces upward; lateral ventricles enlarge Page No. 45

46 SANS Questions of Interest Is IIH an Adequate Terrestrial Analogue for SANS? IIH SANS ONH/Disc Edema YES YES Intracranial Pressure Increased TBD; inconclusive evidence Female : Male 9 : 1 TBD; no females officially diagnosed (0 : 10) ( but changes seen in both sexes!) BMI Obese (>90%) Normal to highly athletic Symptoms Chronic headaches (94%); Transient vision obscuration (68%) None besides near vision complaints Side Bias < 4% unilateral TBD; but gross signs have been right-biased ONH Displacement Gross movement forward Expands forward & backward Retinal : Choroidal Folds >5 : 1; Retinal folds occur first 1 : >5; Choroidal folds occur first Fold Pattern Typically concentric around ONH Typically linear Post-flight MRI Brains displaces downward; no change in size of lateral ventricles Brain displaces upward; lateral ventricles enlarge Page No. 46

47 IIH SANS ONH/Disc Edema YES YES Intracranial Pressure Increased TBD; inconclusive evidence Female : Male 9 : 1 SANS Questions of Interest Is IIH an Adequate Terrestrial Analogue for SANS? TBD; no females officially diagnosed (but changes seen in both sexes!) BMI Obese (>90%) Normal to highly athletic Symptoms Chronic headaches (94%); Transient vision obscuration (68%) None besides near vision complaints Side Bias < 4% unilateral TBD; but gross signs have been right-biased ONH Displacement Gross movement forward Expands forward & backward Retinal : Choroidal Folds >5 : 1; Retinal folds occur first 1 : >5; Choroidal folds occur first Fold Pattern Typically concentric around ONH Typically linear Post-flight MRI Brains displaces downward; no change in size of lateral ventricles Brain displaces upward; lateral ventricles enlarge Page No. 47

48 IIH SANS ONH/Disc Edema YES YES Intracranial Pressure Increased TBD; inconclusive evidence Female : Male 9 : 1 TBD; no females officially diagnosed (but changes seen in both sexes!) BMI Obese (>90%) Normal to highly athletic Symptoms Chronic headaches (94%); Transient vision obscuration (68%) None besides near vision complaints Side Bias < 4% unilateral TBD; but gross signs have been right-biased ONH Displacement Gross movement forward Expands forward & backward Retinal : Choroidal Folds >5 : 1; Retinal folds occur first 1 : >5; Choroidal folds occur first Fold Pattern Typically concentric around ONH Typically linear Post-flight MRI SANS Questions of Interest Is IIH an Adequate Terrestrial Analogue for SANS? Brains displaces downward; no change in size of lateral ventricles Post-flight OD #1 #2 Brain displaces upward; lateral ventricles enlarge Page No. 48

49 IIH SANS ONH/Disc Edema YES YES Intracranial Pressure Increased TBD; inconclusive evidence Female : Male 9 : 1 SANS Questions of Interest Is IIH an Adequate Terrestrial Analogue for SANS? TBD; no females officially diagnosed (but changes seen in both sexes!) BMI Obese (>90%) Normal to highly athletic Symptoms Chronic headaches (94%); Transient vision obscuration (68%) None besides near vision complaints Side Bias < 4% TBD; but gross signs have been right-biased ONH Displacement Gross movement forward Expands forward & backward Retinal : Choroidal Folds >5 : 1; Retinal folds occur first 1 : >5; Choroidal folds occur first Fold Pattern Typically concentric around ONH Typically linear Post-flight MRI Brains displaces downward; no change in size of lateral ventricles Brain displaces upward; lateral ventricles enlarge Page No. 49

50 IIH SANS Source: ONH/Disc Roberts DR, Edema et al. Effects of Spaceflight on YES Astronaut Brain YES Structure Intracranial as Indicated Pressure on MRI. N Engl J Med 2017 Increased 377: TBD; inconclusive evidence ( TBD; no females officially diagnosed Female : Male 9 : 1 (but changes seen in both sexes!) BMI Obese (>90%) Normal to highly athletic Symptoms Chronic headaches (94%); Transient vision obscuration (68%) None besides near vision complaints Side Bias < 4% unilateral TBD; but gross signs have been right-biased ONH Displacement Gross movement forward Expands forward & backward Retinal : Choroidal Folds >5 : 1; Retinal folds occur first 1 : >5; Choroidal folds occur first Fold Pattern Typically concentric around ONH Typically linear Post-flight MRI SANS Questions of Interest Is IIH an Adequate Terrestrial Analogue for SANS? Brains displaces downward; no change in size of lateral ventricles Brain displaces upward; lateral ventricles enlarge Page No. 50

51 IIH SANS ONH/Disc Edema YES YES Intracranial Pressure Increased TBD; inconclusive evidence Female : Male 9 : 1 SANS Questions of Interest Is IIH an Adequate Terrestrial Analogue for SANS? TBD; no females officially diagnosed (0 : 10) ( but changes seen in both sexes!) BMI Obese (>90%) Normal to highly athletic Symptoms Chronic headaches (94%); Transient vision obscuration (68%) None besides near vision complaints ONH Displacement Gross movement forward Expands forward & backward Side Bias < 4% unilateral TBD; but gross signs have been right-biased Retinal : Choroidal Folds >5 : 1; Retinal folds occur first 1 : >5; Choroidal folds occur first Fold Pattern Typically concentric around ONH Typically linear Post-flight MRI Brains displaces downward; no change in size of lateral ventricles Brain displaces upward; lateral ventricles enlarge Page No. 51

52 Is There a Way to Predict Who will be Diagnosed? Not Really, but SANS Questions of Interest Repeat Offenders might give best indication: Those previously diagnosed w/ SANS findings often present findings again during follow-on, long-duration flights ( but n is small ) Recent finding: ONH cup volume may be associated w/ SANS diagnosis Page No. 52

53 An Association Between ONH Cup Volume & SANS? * SANS Case * Subject 1 * * * Subject 2 Subject 3 Subject 4 * Non-Case w/ subclinical edema * * * Subject 5 Subject 6 Subject 7 Subject 8 * Source: Mayra Nelman & Simon Clemett Subject 9 Subject 10 Subject 11 Subject 12

54 SANS Questions of Interest An Association Between ONH Cup Volume & SANS? Appears that ONH edema (which occurs to some extent in most/all long-duration crewmembers): 1. Engorges neurons w/in ONH 2. Edematous neurons fill cup (i.e., empty space) 3. If occupies enough volume, spills out of ONH 4. SANS diagnosed if edema extends 270 o around disc (as visualized via fundoscopy) Source: Mayra Nelman & Simon Clemett So are large ONH cups protective against SANS?? Or, is SANS being under-diagnosed in crew w/ large ONH cups? Are they just as susceptible to potential edema-induced vision loss? Page No. 54

55 SANS Questions of Interest Why was the Syndrome s name changed? Vision Impairment Intracranial Pressure (VIIP) Vision Impairment: Defined as the best-corrected visual acuity worse than 20/40 in the better-seeing eye (National Institutes of Health) Not applicable to long-duration astronauts; all correctable to 20/20 or better Intracranial Pressure: Not conclusively tied to astronaut vision issues Spaceflight Associated Neuro-ocular Syndrome (SANS) More accurate, given current evidence More general; includes wider range of pathogenesis possibilities Page No. 55

56 Page No. 56 Take-Home Messages

57 Top SANS-related risk: Optic disc edema Part of CNS Susceptible to permanent loss, depending on severity & duration Currently, no evidence of true vision impairment in long-duration astronauts Most/all ISS astronauts have ocular changes in-flight, including disc edema Cannot yet predict impact of SANS during expeditionary spaceflight SANS case definition requires an update Based on 2D photographs (fundoscopy); subjective interpretation; binary results Should include objective testing (OCT); be measured on continuous scale SANS affects female astronauts, too Space-naïve astronauts present SANS signs at approx. same rate as veterans IIH is an imperfect terrestrial analogue for SANS ( but is there anything better??) Is a large ONH cup volume protective against SANS or does it mask SANS? Small sample sizes & confounding variables hamper definitive conclusions Page No. 57

58 Optical Coherence Tomography (OCT) technology is / will be critical in diagnosing, tracking mitigation, and determining SANS pathogenesis Source: Mayra Nelman & Simon Clemett Page No. 58

59 Questions? CAPT Tyson Brunstetter, MSC (AsO), USN COM: William J. Tarver, MD, MPH 1 SANS Clinical Lead Michael Stenger, PhD 1 SANS Research Lead Shehzad Batliwala, DO 2 Simon J. Clemett, PhD 3 Russell Derrick 4 C. Robert Gibson, OD 5 Steven Laurie, PhD 4 Brandon R. Macias 4 Thomas Mader, MD 4 Sara Mason 6 Mayra Nelman-Gonzalez 4 Clarence Sams, PhD 1 Caroline Schaefer, MPH 6 Wafa Taiym, MS 4 Mary Van Baalen, PhD 1 Julia Wells, RN, BSN 4 Page No NASA Johnson Space Center Houston, TX 2. Dean McGee Eye Institute Oklahoma City, OK 3. Jacobs Technology, Inc. Houston, TX 4. KBRWyle Houston, TX 5. Coastal Eye Associates Webster, TX 6. MEI Technologies Houston, TX