# Presentation: 460887

## P050034The Implantable Miniature Telescope (IMTTM)

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

## 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.

## The proposed indication reads:

- The IMTTM 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

## 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**

## 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.

**Notes:**
The sponsor conducted a prospective, multicenter clinical evaluation of the use of the AMD implant in subjects with bilateral, stable, untreatable moderate to profound central vision impairment due to age-related macular degeneration and have cataracts.  The study was conducted in the U.S. under an approved IDE.  A total of 218 consecutive patients were enrolled and 206 patients were implanted and evaluated at 28 clinical sites followed over a 24-month period .  At the time of database closure, 194 eyes had reached the 12-month follow-up, 180 eyes had reached the 18-month follow-up examination and 148 eyes had reached 24-month follow-up. 

## Effectiveness Endpoints

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

**Notes:**
The primary effectiveness endpoint is defined as an improvement of (READ Slide)

Quality of Life Surveys are secondary measurements of procedure success.

## 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.

**Notes:**
Read the ECD stuff in the first bullet

Preservation of best corrected visual acuity, i.e., no more than 10% of implanted eyes were to experience a loss of more than 2 lines of either near or distance BCVA without a corresponding improvement (gain of 2 lines or more) in BCVA (a gain of 2 or more lines of near BCVA in eyes with loss of more than 2 lines distance BCVA, and vice versa). 

## Clinical Safety 

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

**Notes:**
Key study outcomes will be discussed in this presentation so that the panel will be able to make recommendations regarding the safety of the IMT with respect to the minimum preoperative ECD of prospective IMT patients, the minimum anterior chamber depth, and, subsequently, the relationship of preoperative ECD levels with respect to minimum age qualifications for selection. 

## 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 <1000 cells/mm2
- 90th percentile @ 2 years (10% with greatest loss) was:
- ·         60% ECD loss - IMT-implanted eyes
- ·         12% ECD loss - fellow eyes.

**Notes:**
AT 1 year postop, IMT implanted eyes demonstrated a 25.3% mean decrease in ECD, at 2 years, this mean rate of loss rose to 28.2%.  

Also at 2 years postop, we can see that 12.5% of implanted IMT eyes demonstrated ECD counts of <1000 cells/mm2

For the 10% of eyes with the greatest loss, the 90th percentile:
                     There was a 60% loss of ECD for IMT implanted eyes as compared to 12.5% of fellow eyes. 

## Endothelial Cell Density Loss

**Notes:**
This slide presents the proportion of eyes with ECD losses greater than 20% over time for IMT implanted eyes in comparison to the fellow eyes.
3 months -   40%
12 & 18 months ~ 50%
And at 2 years, ~ 60% 
Across all time periods, the fellow eyes demonstrate a relatively constant level of ECD counts. 

## 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 < 3mm had the greatest losses 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

**Notes:**
Many factors have been identified as contributing to the ECD outcomes of this study. The panel should take into consideration in their deliberations that there was no morphometric data presented by the sponsor; the issue of surgical order, ACDs of <3 mm as well as surgeon specialty when making recommendations for defining the indications and labeling for the IMT, if approved. 

## 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

**Notes:**
United States Life Tables 2002[1]
	Life expectancy for a person 60 years old is 22 additional years.  And for a person 90 years of age an additional 5 years of life. One can easily see that age is an important consideration in patient selection. 
FDA requested an analysis of the number of eyes that would progress to an ECD of ≤ 1000 cells/mm2 since the potential for corneal edema occurs at ECD’s of ≤800 cells/mm2. The next slide presents the results of that analysis. 

[1]Arias E.  United States Life Tables, 2002.  National Vital Statistics Reports, Vol. 53, No. 6.  Hyattsville, Maryland:  National Center for Health Statistics, 2004.
[2] Lane SS, Kuppermann BD.  The implantable miniature telescope for macular degeneration.  Current Opinion in Ophthalmology.  2006;17:94-98.
[3] Lane SS, Kuppermann BD.  The implantable miniature telescope for macular degeneration.  Current Opinion in Ophthalmology.  2006;17:94-98.

## Percentage of Eyes with Predicted ECD ≤1000

**Notes:**
These data were generated by FDA statisticians, and they will be presenting you with the details of their analyses following the clinical presentation. 

              IMT eyes          Fellow eyes
2 years   (11.1%)             (0.5%)
3 years   (17.6%)             (0.9%)
4 years   (22.7%)             (1.4%)

This chart clearly shows that the number of IMT eyes whose ECD falls to 1000 or less increases with each advancing postop time interval out to 4 years as compared to fellow eyes. 

## ECD Loss Stratified by ACD

**Notes:**
Anterior chamber depth is related to the ECD loss sustained by IMT patients. The length of the IMT (4.4mm) in conjunction with shallower anterior chambers may induce endothelial cell loss by the increased potential for surgical trauma and by the proximity of the IMT to the endothelium post implantation .
Anterior chamber depth is reported by the sponsor to have a major impact on ECD loss rates reported in the first 6 months postop.  While these related losses do not appear to contribute to the chronic rate of loss, they are permanent and thus have the potential to impact corneal physiology.  The next slide will present data related to the various strata of ACDs represented in the IMT clinical trial as analyzed by FDA.  

## Slide 15

| Postop Interval | Anterior Chamber Depth  |  |  |
| --- | --- | --- | --- |
|  | 3.00mm
Mean loss | >3.00-3.50mm
(∆ Mean loss as compared to ACD 3.00mm)
 | >3.50mm
(∆ Mean loss
as compared to ACD 3.00mm) |
| 3 months | 22.1% | 19.3%
(2.8% less) | 16.2% 
(5.9% less) |
| 6 months | 26.3% | 20% 
(6.3% less) | 18.8% 
(7.5% less) |
| 12 months | 27.0% | -25.0% 
(2.0% less)
 | 22.3% 
(4.7% less) |
| 24 months | 31.7% | 26.9%
(4.8% less) | 24%
(7.7% less) |

**Notes:**
Eyes with ACDs of <3mm had the greatest losses at all time periods and especially at 24 months, where approximately 1/3 of ECD has been lost. 
ACDs ranging from >3.0mm - 3.50mm showed clinically significant less ECD loss than those with ACDs of 3.0mm or less
These losses ranged from 2.8% to 6.3% less  than ACDs of ≤3.0 mm.

Likewise, eyes with ACDs of >3.5mm showed clinically significant less ECD loss than eyes with ACDs  of 3.0mm or less. 
These losses ranged from 4.7% to 7.7% less than the losses of eyes with ACDs of 3.0 or less.
It is also noteworthy, that both of the patients who experienced corneal decompensation and subsequent transplant, had ACDs of less than 3.0 mm.

## 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

**Notes:**
The IMT is designed for a 2mm corneal endothelial clearance. The study selection criteria utilized a minimum ACD of 2.5mm
No substudies were performed or data presented to establish suitability of the proposed minimum ACD for the established minimum clearance of 2.0mm.

## Haptic Placement

|  |  | N | % |
| --- | --- | --- | --- |
| Superior Loop
 | Bag | 198 | 96.1 |
|  | Sulcus | 8 | 3.9 |
| Inferior Loop
 | Bag | 201 | 97.6 |
|  | Sulcus | 5 | 2.4 |

**Notes:**
The average anterior chamber depth was 3.15 mm +/- 0.37 . It has been published in IMT literature that placing the IMT in the sulcus as opposed to completely in the bag, moves the device anteriorly and increases the risk of corneal touch. Taking the mean ACD represented in this study, the percentage of sulcus placed devices ranging from approximately 2.5 to 4 percent, and the rates of surgical and chronic loss of ECD into account, the panel should weigh the importance of ACD and IMT carefully. 

## Posterior Capsular Opacification 

- 1/174 (0.6%) @18 months
- 2/147 (1.4%) @ 24 months.
- Zero (0) YAG Capsulotomies
-  Needling
- 		- two patients with visually     	significant PCO.

**Notes:**
During the course of the clinical trial, 1 eye was reported to have PCO at 18 months and 2 eyes at 24 months. 

The sponsor claims that they utilized specific design objectives to minimize the occurrence of posterior capsular opacification. The primary elements  included the biocompatibility of the material used, the geometry of the device and its alignment with the capsular bag 

YAG Capsulotomies for visually significant PCO were not performed during the IMT clinical trial. However, due to 2 cases of visually significant PCO, the sponsor utilized the Needling procedure to address the events. 

## PCO Management 

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

**Notes:**
YAG capsulotomies were not performed because the sponsor has identified that the lenses contained within the IMT telescope can be damaged by the laser. 
The sponsor has proposed labeling to provide instruction to the physician regarding the performance of YAG capsulotomy through the periphery of the telescope as well as recommending the needling procedure. YAG capsulotomy was successfully performed in 8 rabbit eyes implanted with the IMT. The results of this study were reported in the Journal of Cataract and Refractive Surgery (2003). 

## 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

**Notes:**
Performing a YAG capsulotomy as recommended by the sponsor can only be done around the periphery of the IMT.
This would require a significant increases in the # of bursts required to achieve the capsulotomy and increase the total amount of energy delivered to the eye. Subsequently, there is an increased risk of Retinal Detachment.  

And finally, because the apposition of the IMT against the posterior aspect of the capsular bag is so important, it is unknown what effect a YAG will have on this positioning. The sponsor has not provided any information regarding this issue. 

## Clinical Effectiveness 

- Visual Acuity
- Quality of Life

**Notes:**
The panel will be asked to evaluate various data on clinical effectiveness based upon improvement of both BCDVA and BCNVA as well as improvements in Quality of Life measures. 

## Categories of Vision Loss

*Visual impairment –*
- BCDVA ≤ 20/40 but better than 20/200.
*Legal blindness *
-  BCDVA ≤ 20/200
-  visual field diameter < 10 degrees.
*Low vision <* 20/60 in the better eye.

**Notes:**
In the discussion of the effectiveness outcomes of the IMT, it is important to establish the various categories of vision loss represented in the study population.  

## Preop VA  Values - IMT

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

**Notes:**
 The mean preoperative visual acuity data for both distance and near for the IMT clinical trial indicates that most of the subjects in this clinical trial were categorized as legally blind. 

## Implantation profile

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

**Notes:**
READ THE SLIDE

## 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

**Notes:**
As one can see from this slide, there is a large proportion of eyes reported to have had significant improvements in acuity,  but can patients actually see and do more? 
In light of significant fluctuation in repeated measures of acuity in macular degeneration patients, the panel will be asked to decide if the reported proportions of acuity improvements ≥2 lines from preop provide sufficient benefit with respect to the safety risks of the IMT.

## 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

**Notes:**
For IMT implanted eyes, 90.1% of implanted eyes were reported to have had an improvement of ≥2 lines in either BCDVA or BCNVA at 12-months postop. 

For refractive lasers and phakic IOLs a change of ≥2 lines denotes a clinically significant change in visual function. These eyes are not diseased or considered low vision or legally blind. The panel should weigh the value of evaluating successful outcomes for the IMT with respect to the criterion of improvement in lines of visual acuity.

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

|  | HCVA logMAR | LCVA logMAR | PRC 
log contrast units | MET
log contrast units |
| --- | --- | --- | --- | --- |
| Young Normal | .07 |  | 0.15 |  |
| Normal Uncorrected | 0.17 | 0.15 |  |  |
| Normal Optically degraded | 0.17-0.27 | 0.18-0.34 | 0.22-0.36 |  |
| Moderate Ocular Disease | 0.09-0.19 | 0.19 | 0.39 |  |
| LV in Laboratory | 0.17 |  |  |  |
| LV in Clinic | 0.29 | 0.25 | 0.38 | 0.38 |

**Notes:**
The fluctuation of VA mentioned has been substantiated by  Russell Woods and Jan Lovie-Kitchin of the Centre for Eye Research, School of Optometry, Queensland University ofTechnology. This table shows that previously reported repeatability coefficients for young normal subjects are significantly smaller than those found in a study of low vision subjects and uncorrected normal vision subjects. This is consistent with the repeatability coefficients reported for subjects with moderate ocular disease and subjects with optically degraded vision. It is also consistent with the suggestion that the repeatability coefficient increases as the average visual performance of the group reduces as shown in this table.

## Slide 28

| BCDVA
Change from Baseline
 | Moderate Impairment(20/80 to 20/160) |  | Severe Impairment(20/161 to 20/400) |  | Profound Impairment(Worse than 20/400) |  |
| --- | --- | --- | --- | --- | --- | --- |
|  | n | % | n | % | n | % |
| Gain 3 lines |   4 |  23.5% |  46 |  55.4% |  36 |  76.6% |
| Gain 2 lines but <3 lines |   4 |  23.5% |  13 |  15.7% |   5 |  10.6% |
| Gain 1 line but <2 lines |   2 |  11.8% |  10 |  12.0% |   4 |   8.5% |
| Other |   7 |  41.2% |  14 |  16.9% |   2 |   4.3% |
| Gain 2 lines |   8 |  47.1% |  59 |  71.1% |  41 |  87.2% |
| N |  17 |  |  83 |  |  47 |  |
| Not reported/IMT removal |   0 |  |   1 |  |   0 |  |
| Total |  17 |  |  84 |  |  47 |  |

**Notes:**
The data on this chart, taken from the PMA application, indicate that those subjects with severe and profound vision loss, representing the largest proportion of subjects within the cohort, show greater than 3 lines of improvement in visual acuity.  Technically, the  acuity predicted from the magnified post-operative retinal image should result in acuity increases of 3 lines, or 0.3 logMAR, relative to preoperative acuity at the most. 

## Predicted EffectivenessDistance Visual Acuity

| IMT Model | Mean Preop BCDVA | Predicted Postop BCDVA | 24 Months Postop |
| --- | --- | --- | --- |
| 3X (2.7X) | 20/312 | ~20/115
(~3 line improvement) | Mean BCDVA  20/150 |
| 2.2X | 20/312 | ~20/142
(~3 line improvement) |  |

**Notes:**
The predicted postop acuities for the mean preop BCDVA of 20/312 with the 3X IMT having a nominal magnification of 2.7 would be approximately 20/115. With the 2.2X IMT, the predicted postop BCDVA would be approximately 20/115.  The mean BCDVA at 24 months postop was 20/150. ~52% of the available cohort achieved an ~3 line improvement in BCDVA by year 2. 
The safety and effectiveness for visual acuity are based on unadjusted baseline acuity and not on acuity predicted from the magnified postoperative retinal image. 

## Predicted EffectivenessNear Visual Acuity

| Near Distance | Mean Preop BCNVA | Predicted Postop BCDVA | Mean BCNVA @ 24 Months Postop |
| --- | --- | --- | --- |
| 8 inches | 20/315 | ~20/105
(~3 line improvement) | 
20/190.2 |
| 16 inches | 20/262 | ~20/87
(~3 line improvement) | 
20/157.6 |

**Notes:**
The predicted postop acuities for the mean preop BCNVA of 20/315 @ 8 inches  assuming an average improvement of approximately 3 lines of acuity would be 20/105. At 16 inches, the predicted acuity would be 20/87.  In actuality, the mean acuities achieved by 24 months postop were 20/190 at the 8 inch test distance and 20/157.6 at 16 inches. 
The safety and effectiveness for visual acuity are based on unadjusted baseline acuity and not on acuity predicted from the magnified postoperative retinal image. There is no data showing how much acuity improved as a result of the cataract removal alone. 

## 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 <1.4 or 2.3 = a ***loss*** of >2 lines

**Notes:**
preoperative acuity measurements were not adjusted for magnification at  baseline. 
If the IMT performs its intended optical function of magnifying the retinal image by either 2.2 or 2.7 times, without affecting corneal or retinal function, measured acuity will increase by 3.4 or 4.3 lines, respectively.
A measured 2 line loss is really 5.4 (or 6.3) lines from a retinal standpoint, and an apparent improvement of <1.4 (or <2.3) lines is really a loss of >2 lines from a retinal standpoint.
The panel will be asked to determine  whether the unadjusted preop acuity baseline is acceptable for evaluation of safety and efficacy of this device. 

## Safety & Effectiveness 

- Vision Rehabilitation
- Functional Vision
- Orientation & Mobility
- Reading

**Notes:**
The panel will be asked to address not only the objective Visual Acuity data, but the functional safety and effectiveness of the IMT as addressed by the vision rehabilitation program utilized in the clinical trial. 

## 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.

**Notes:**
While the entire VFQ- 25 assesses visual function by self-report, these specific items are strongly related to the areas of visual difficulty for macular degeneration patients. 

## VFQ-25

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

**Notes:**
The sponsor presented the mean scores and mean changes in scores for both the NEI-VFQ and ADL Questionnaires. FDA requested that the sponsor provide FDA with the frequency analyses for each rating within each category assessed in the NEI-VFQ and ADL questionnaires for both the scores and change in score analyses. FDA requested this because the mean does not tell the whole story. 

## 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.

**Notes:**
The frequency analyses for each rating within each category assessed in the NEI-VFQ show that (READ the Slide!)

## VisionCare’s 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.***

**Notes:**
IMT patients were given written directions, and with assistance from family members, were to practice many demanding tasks such as walking, reading, and associated tasks of daily living.  The program did not utilize any direct performance measures of the pre and post-implantation skills of the study patients.  Family members directed the home training program and were responsible for making environmental modifications. At their scheduled visits,  optometrists and ophthalmic technicians many of whom had low vision training, checked on the progress of the rehabilitation program and provided additional instruction. The IMT patients were not professionally instructed on safe mobility and navigation in their home environments and did not have reading instruction by low vision reading instructors.  

## 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.

**Notes:**
Massof from the Wilmer Eye Institute defines success in low vision rehabilitation (read the slide now).

## Is professional vision rehab necessary? 

- Failure rate decreased from 22% to 3% with training according to Langman et al. 1944
- A survey (@ 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

**Notes:**

Numerious studies verify that vision rehabilitation with specific targeted goals, directed by vision rehabilitation specialists yields a high rate of success that is sustained over time. 

Langmann A, Linder S, Kollegger E. Low vision training for better usage of 
 magnifying visual aids. Ophthalmologica 1944;208(2):92-4.Watson GR, De l’Aune W, Stelmack J, Maino J, Long S. National survey of the impact of low vision device among veterans. Optom Vis Sci 1997 May;74(5):249-59. 
 Van Rens GH, Chmielowski RJ, Lemmens WA. Results obtained with low vision aids. A retrospective study. Doc Ophthalmol 1991;78(3-4):205-10.
4. Fletcher DC, Shindell S, Hindman T, Schaffrath M. Low vision rehabilitation. Finding capable people behind damaged eyeballs. West J Med 1991;154:554-556.
5. Fletcher DC. Low vision: the physician’s role in rehabilitation and referral. Geriatrics 1994;49:50-53.

## 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 < 20/25
- 4.4% with normal visual acuity had experienced a fall in the prior year.

**Notes:**
Annually, 25% to 35% of older persons fall and >40% result in hospitalization.

Nevitt et al reported a threefold risk for multiple falls with poor vision and, 

The Beaver Dam Eye Study reported that for individuals ≥60 years of age ω acuity < 20/25, 11% suffered injurious falls every year as compared to only 4.4% of those with normal visual acuity. 

## Adverse events - Falls

- 8 non-ocular adverse events occurred during this trial

**Notes:**
During the course of the clinical trial, 8 non-ocular adverse events occurred. These occurred after implantation and consisted of 4 fractures, 1 contusion, and other forms of injury related to falls. 					

## 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

**Notes:**
Magnification alters proprioceptive senses & creates a safety issue for the newly implanted IMT patient. Training by low vision specialists should be a requirement of this device. However, since most physicians will not have direct access to Mobility and orientation training specialists They will need to make referrals to agencies for these services. 

State associations for the blind and visually impaired are mandated in every state in addition to other agencies serving the needs of the visually impaired. 

## Central & Peripheral Vision

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

**Notes:**
The patients were to practice exercises for learning to suppress central vision in the IMT eye when performing visually demanding tasks such as walking, requiring the use of peripheral vision. The program was directed by family members and did not utilize any direct performance measures of the subjects’ ability to voluntarily shift binocular suppression from one eye to the other. 

## 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

**Notes:**

The implantation of the IMT is proposed to be used both binocularly and monocularly.  This presents significant conerns regarding binocular performance.  Among these are (READ THE SLIDE). 

## Normal Monocular Field (OD)

**Inferior**

**Superior**

**Left**

**Right**

**Notes:**
The monocular field extends greatly to the temporal aspect and is curtailed nasally with the superior and inferior fields being somewhat equal. 
(NEXT SLIDE)

## Normal Monocular Field (OS)

**Inferior**

**Superior**

**Left**

**Right**

**10°**

**20°**

**30°**

**40°**

**50°**

**60°**

**70°**

**80°**

**90°**

**Notes:**
NEXT SLIDE)

## Normal Binocular Field

**Inferior**

**Superior**

**Left**

**Right**

**10°**

**20°**

**30°**

**40°**

**50°**

**60°**

**70°**

**80°**

**90°**

**Notes:**
The binocular field is simply the combination of the two monocular fields which results in an area of overlap that supports stereoscopic binocular vision.
(NEXT SLIDE)

## Binocular Field for Macular Degeneration Patients

**Inferior**

**Superior**

**SC**

**Notes:**
For macular degeneration patients, a dense scotoma extends out to about 4 to 5 degrees of eccentricity, but the entire peripheral field beyond the central scotoma remains normal.
(NEXT SLIDE)

## Subjective Field of IMT Eye

**Subjective Field of IMT Eye**

**Inferior**

**Superior**

**SC**

**Notes:**
However, when the IMT is implanted, all visual stimulation is permanently blocked outside the telescopic field of view.  This plot shows the subjective IMT field of about 54 degrees diameter, minus the central scotoma.  The outer boundary is similar to the area covered by a conventional Humphrey 24-2 visual field test.

## Objective Field of IMT Eye

**Objective Field of IMT Eye**

**Inferior**

**Superior**

**Notes:**
In terms of the information from the environment, however, this field covers only 20 to 24 degrees in diameter, depending on the IMT magnification.  The effective central scotoma is decreased proportionally to the amount of magnification of the telescope. 

## Monocular Field - Fellow Eye

**Monocular Field - Fellow Eye**

**Inferior**

**Superior**

**SC**

**Notes:**
The monocular field of the fellow eye is of course unaffected by IMT implantation. 

## Objective IMT Binocular Field

**Objective IMT Binocular Field**

**Inferior**

**Superior**

**Left**

**Right**

**Notes:**
If an IMT patient were able to optimally use the information to both eyes, the combined field would exclude stereopsis, but would otherwise be equivalent to the fellow eye field with improved central acuity and a reduced central scotoma.
(NEXT SLIDE)

## IMT Objective Binocular Field Fellow Eye Overlap Suppressed

**IMT Objective Binocular Field Fellow Eye Overlap Suppressed**

**Inferior**

**Superior**

**Left**

**Right**

**Notes:**
When the IMT eye suppresses the overlapping part of the fellow eye field, however, neither eye receives information about the annular region from 10 to 27 degrees of eccentricity.
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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.

**Notes:**
Motion is a powerful stimulus for focusing attention. For IMT patients, retinal images move proportionally farther and faster in the magnified IMT field than in the fellow eye peripheral field in the case of: (read first four bullets)

Discordant motion information can cause disorientation, vertigo, and/or motion sickness if both moving images are seen together. No such symptoms were reported for IMT subjects.  
This suggests suppression of either the IMT image, or 
the entire fellow eye image.  
Vision Care has provided no data regarding this issue.

Since the IMT eye receives the more prominent motion stimulus, the second possibility seems more likely.  (NEXT SLIDE)

## IMT Binocular Field with Entire Fellow Eye Suppressed

**IMT Binocular Field with Entire Fellow Eye Suppressed**

**Inferior**

**Superior**

**Left**

**Right**

**Notes:**
As this slide illustrates, this would leave the IMT patient receiving effective visual input to only the central 20 or 24 degrees of field. The possibility exists that at least some IMT patients could experience this effect without noticing that their visual field is severely constricted.
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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. .