all scanners are equal, but some scanners are more equal than others zeiss stratus – 4.5% topcon...
TRANSCRIPT
All scanners are equal, but some scanners are more equal than others
• Zeiss Stratus– 4.5%
• Topcon OCT1000– 6.5%
• Heidelberg Spectralis– 8.7%
• Zeiss Cirrus– 11.8%
Relationship to patient features
• Older age– 68yrs cf 60
• Caucasian– 8.4% cf 3-4%
• Type 2 diabetes– 8.7% cf 3.9%
• Poorer vision– 5x more likely– If VA ≤ 6/9
• BUT NOT– Sex, glitazone, amblyopia
Relationship to Lesions
R Eye % L Eye %
No lesions
0.8 0.6
Ma/dot only
2.2 2.3
Blot no Exudate
10.2 11.2
Exudate 12.5 11.2
Other 1.1 1.1
Can we do any better?
• Three Grading Strategies Examined– Manual grading
• Presence/ absence of features• SDRGS 2007
– Computer-assisted manual annotation• All individual lesions ≤ 2DDr
– Fully automated annotation grading• Three versions
– Automated image analysis– +VA– +VA + Age+ Type DM + Sex
Manual Grading (features)
Manual Grading (features)
• Scotland– 59.5% sensitivity– 79.0% specificity
• England– 72.6% sensitivity– 66.8% specificity
• England plus– 73.3% sensitivity– 70.9% specificity
Computer Assisted, Manual Annotation, Grading• Best for sensitivity &
specificity• Time-consuming
procedure • Unlikely to be
considered for routine screening practice
In Years To Come
Marvin the Manically Depressed Autograder
""I think you ought to I think you ought to know…. I'm feeling very know…. I'm feeling very depressed ......nobody depressed ......nobody likes melikes me""
DRS in Scotland 2012
What will it cost?
• Cost per screen £33.13• Cost per OCT screen £31.96• Total cost for ?oedema £65.09
• Cost of attending ophthalmology £90.00
• (Cost of Slit lamp within DRS £27.29)
TABLE 30 Screening and referral cost per true case of macular oedema detected for 3,170 patients; Adjusted for expected frequency of different patient categories and based on Scottish screening and referral costs
* Reference strategy; a figures in table based on assumption that fully automated grading can be implemented at zero net increase in grading costs;++ Represents a cost saving per case missed relative to the reference strategy; d strategy more costly and less effective than an alternative strategy (dominated)
What does it mean?
• At present we spend £13,750,000 a year – 250,000 people @ £55– Screening + 1st visit to
ophthalmology– £2,337,500 on ? M2
• If we do nothing, other than introduce OCT into the screening pathway
• we save money
Should we grade differently?
Current Scottish Criteria + OCT is the most cost effective of all strategies
What if we do nothing? 20 year “M2” Markov Model• Only 5.6% of M2 at risk of visual loss• Repetitive nature of screening
– 12% of non-referred MO modelled to progress at 12 months cf 5% of referred (laser Rx)
• More sensitive strategies– More OCTs, more referrals
• Bilateral incidence 12%– QALY determined by VA in better seeing eye
• Additional cost per QALY going to strategy 16– £882,307 at 5 years– £353,927 at 20 years– (£20-30,00 UK threshold for “cost-effectiveness)
What should we do?
Cost-effectiveness acceptability curves for the alternative strategies based on a 20 year time horizon and using quality adjusted life years as the measure of effect
How should we manage M2s?Is this the answer?
• Photos graded as M2• Check VA• Do an OCT if VA 6/12 or worse?• Otherwise rescreen in 6 months?
Thank You
Modelled visual acuity changes for “CSMO”