P050034 The Implantable Miniature Telescope IMT

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P050034The Implantable Miniature Telescope
(IMT)

• Presented by
• Bernard P. Lepri, OD, MS, MEd
• FDA/CDRH/ODE/DOED
• July 14, 2006

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Special Thanks!

• Gene Hilmantel, OD, MS the Rosetta Stone of
  biostatistics
  
• Bruce Drum, PhD the walking guide to visual
  science and contributor of the visual science
  slides of this presentation today.

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The proposed indication reads

• The IMT is indicated for use in adult patients
  with bilateral, stable, untreatable, moderate to
  profound central vision impairment due to macular
  degeneration as determined by fluorescein
  angiography, and cataract in patients who

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Indications (continued)

• are 55 years of age or older
• Have BCDVA of 20/80 to 20/800
• Have Adequate peripheral vision in the
  nonoperative eye and
  
• Demonstrate a minimum 5 letter improvement on
  ETDRS chart with an external telescope
  

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Study Design

• prospective, multicenter clinical trial
• 28 clinical sites
• conducted in the U.S. under IDE
• 218 consecutive patients were enrolled
• 206 patients were implanted and evaluated
• Mean age was 75.4 years 7.2
• followed over a 24-month period
• 1 day, 1 wk, 1-, 3-, 6-, 9-, 12-, 18- and
  24-month postoperatively.
  

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Effectiveness Endpoints

• 2 lines BCDVA/BCNVA in 50 of eyes _at_ 12 mos.
  Postop primary endpoint.
  
• Quality of Life surveys (ADL and VFQ-25) -
  secondary measurements of procedure success.
  

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Safety Endpoints

• Endothelial cell loss Mean ECD loss 17 at
  1yr. postop primary
  
• average ECD loss large-incision cataract
  surgery reported in literature
  
• 10 eyes lose 2 lines BCDVA or BCNVA without a
  gain of 2 lines in BCVA secondary
  
• Adverse events and complications no preset
  targets.
  

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Clinical Safety

• Preop ECD 1600 Cells/mm2
• Minimum ACD 2.5mm
• Minimum Age 55

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Mean Decrease in ECD (overall cohort)

• 25.3 at 1 year
• 28.2 at 2 years.
• 12.5 (CI 7.6 to 19.0) of eyes available at 2
  years had ECD counts of
• 90th percentile _at_ 2 years (10 with greatest
  loss) was
  
•          60 ECD loss - IMT-implanted eyes
•          12 ECD loss - fellow eyes.  

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Endothelial Cell Density Loss
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ECD Considerations

• No morphometric data on ECD was presented by the
  sponsor.
  
• High ACD loss due surgical order first three
  cases
  
• Eyes with ACDs of at all time periods and especially at 24 months,
  where approximately 1/3 of ECD has been lost.
  
• Surgical specialty corneal surgeons had the
  lowest surgical loss rates

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ECD Considerations (continued)

• 60 years old - 22 more years (82 years old)
• 90 years old - 5 more years (95 years old)
• Minimum acceptable level of ECD for future
  cataract surgery is 1500 cells/mm²
  
• 800 cells/mm² - potential corneal edema

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Percentage of Eyes with Predicted ECD 1000
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ECD Loss Stratified by ACD
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ACD Corneal Clearance

• IMT is designed for a 2mm corneal endothelial
  clearance
  
• Minimum ACD was 2.5mm
• No substudies or data presented to establish
  suitability of minimum ACD for the established
  minimum clearance

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Haptic Placement
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Posterior Capsular Opacification

• 1/174 (0.6) _at_18 months
• 2/147 (1.4) _at_ 24 months.
• Zero (0) YAG Capsulotomies
• Needling
• - two patients with visually significant
  PCO.
  

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PCO Management

• YAG capsulotomy can damage the IMT lenses.
• Capsulotomy through the periphery of the
  telescope
  
• No patient data available
• Rabbit studies performed

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Potential Problems with YAG Procedures

• Can only be done around the periphery of the IMT
• Increases the of bursts and total amount of
  energy delivered to the eye
  
• Increases risk of Retinal Detachment
• Posterior movement of the IMT

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Clinical Effectiveness

• Visual Acuity
• Quality of Life

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Categories of Vision Loss

• Visual impairment
• BCDVA 20/40 but better than 20/200.
• Legal blindness
• BCDVA 20/200
• visual field diameter
• Low vision

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Preop VA Values - IMT

• The preoperative Acuity range was 20/80 - 20/800
• mean preop BCDVA - 20/312
• mean preop BCNVA
• _at_ 8 inches - 20/315
• _at_ 16 inches was 20/262

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Implantation profile

• 115 eyes were implanted with the 2.2X
• 91 eyes were implanted with the 3.0X

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Improvement in Vision

• Improvement of 2 lines BCDVA or BSNVA 85 to
  90
  
• Improvement of 2 lines BCDVA and BSNVA 67 to
  73
  
• 52.8 (102/193) gained 3 lines BCDVA and BCNVA

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VA Improvements 2 lines

• 90.1 of implanted eyes were reported to have had
  an improvement of 2 lines in either BCDVA or
  BCNVA at 12-months postop.
  
• Refractive devices baseline 20/40

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Reliability of Low Vision Measures - Russell
Woods and Jan Lovie-Kitchin

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Predicted EffectivenessDistance Visual Acuity
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Predicted EffectivenessNear Visual Acuity
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Adjusted vs. Actual Acuities?

• IMT measured acuity will theoretically increase
  by 3.4 or 4.3 lines, respectively for the 2.2
  3.0X
  
• 2 line loss 5.4 or 6.3 lines
• improvement of 2 lines

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Safety Effectiveness

• Vision Rehabilitation
• Functional Vision
• Orientation Mobility
• Reading

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VFQ-25 - Items 5, 6, 7, 8, and 9

• Independent mobility,
• Reading street signs and names of stores,
• Negotiating steps and curbs, and
• Reading ordinary print in newspapers.

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VFQ-25

• PMA reports mean scores and mean changes
• FDA requested a frequency analysis for each
  rating within each category.

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Summary of Frequency Analysis of Items 5, 6, 7,
8 9

• Subjects reporting extreme difficulty with the
  items pertaining to visual function decreased in
  number by one year postop.
  
• Subjects reporting little and moderate levels of
  difficulty increased at one year.
  
• It is unclear from the data reported whether some
  of the subjects who initially reported extreme
  difficulty subsequently reported moderate
  difficulty.

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VisionCares Rehab Program

• Implemented by the patient with assistance from
  the family
  
• Professionally directed Orientation and Mobility
  - not provided.
  
• LV Reading Specialist Training not provided.
• No validated methods of measuring the outcomes of
  training.

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What is successful rehabilitation?

• A reduction in the level of difficulty in
  performing a particular task or goal, or the
  reduction in the importance of that task by
  teaching the patient alternative strategies to
  achieve the goal.
• Massof,RW. A system model for low vision
  rehabilitation. I. Basic concepts. Optom Vis
  Sci. 1995 Oct 72(10) 72-36.

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Is professional vision rehab necessary?

• Failure rate decreased from 22 to 3 with
  training according to Langman et al. 1944
  
• A survey (_at_ 12 and 24 months) of 200 veterans
  using 740 low vision aids found that 85.4 of
  devices were still in use.
  
• 85.4 of 200 Veterans were found to still be
  using their optical assistive devices 2 years
  later - Watson et al. 1997
  
• 77 of 261 cases used optical devices
  successfully - Van Rens et al. 1991
  
• Improves patient independence, performance of
  ADLs, and quality of life Fletcher et al. 1991,
  1994

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VISUAL LOSS AND FALLS

• Nevitt et al reported a threefold risk for
  multiple falls with poor vision.
  
• 25 to 35 annually of older persons fall
• 40 result in hospitalization.
• Beaver Dam Eye Study
• 60 years of age
• 11 (943) of 2365 with acuity
• 4.4 with normal visual acuity had experienced a
  fall in the prior year.
  

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Adverse events - Falls

• 8 non-ocular adverse events occurred during this
  trial
  

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Effects of Magnification

• magnification alters proprioceptive senses
• judgment of relative distances
• location objects in the visual space
• ability to walk and to read
• judgment of depth of steps and curbs

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Central Peripheral Vision

• IMT implanted eyes Central
• Fellow eye Peripheral
• No direct performance measures for shifting
  binocular suppression from one eye to the other.

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Binocular Performance

• Non-correspondence of overlapping fields forces
  binocular rivalry and suppression
  
• Severe visual field restriction in the (dominant)
  IMT eye
  
• Motion discrepancies in magnified and unmagnified
  fields
  
• Possible suppression of entire fellow eye

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Normal Monocular Field (OD)
Superior
Left
Right
Inferior
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Normal Monocular Field (OS)
Superior
Left
Right
10
20
30
40
50
60
70
80
90
Inferior
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Normal Binocular Field
Superior
Left
Right
10
20
30
40
50
60
70
80
90
Inferior
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Binocular Field for Macular Degeneration Patients
Superior
SC
Inferior
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Subjective Field of IMT Eye
Superior
SC
Inferior
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Objective Field of IMT Eye
Superior
Inferior
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Monocular Field - Fellow Eye
Superior
SC
Inferior
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Objective IMT Binocular Field
Superior
Left
Right
Inferior
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IMT Objective Binocular Field Fellow Eye Overlap
Suppressed
Superior
Left
Right
Inferior
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Motion Discrepancies Magnified/ Unmagnified
Fields

• Object motion
• Head motion
• Consensual eye movements
• Motion through the environment
• No symptoms were reported for IMT subjects.
• Suggests suppression
• the IMT image, or
• the entire fellow eye image.

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IMT Binocular Field with Entire Fellow Eye
Suppressed
Superior
Left
Right
Inferior
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Risks vs. Benefits

• The discussion of this device warrants
  careful consideration of the reported
  improvements in visual acuity with respect to the
  postoperative risks of ECD loss, potential
  perceptual adjustment problems and unknown
  problems with examination and treatment of an IMT
  implanted eye. .