The St Kitts Eye Study

The St Kitts Eye Study Paul H Artes, PhD Ophthalmology and Visual Sciences, Dalhousie University, International Health Office, Oct ‘09

Content

The Problem with Glaucoma Our Links with St Kitts Screening for Glaucoma – what we need to know Protocol of the St Kitts Eye Study What we have learned so far Where do we go from here

The Problem with Glaucoma

The Problem with Glaucoma

The Problem with Glaucoma

The Problem with Glaucoma

Federation of St Kitts and Nevis

St Kitts 5 km

168 sq.km 35,000 inhabitants (2001 census)

St Kitts and Halifax: Connections

St Kitts and Halifax: Connections 1991: Eye Centre of Joseph N France Hospital established, with help from Halifax 2001: first proposal for screening project 2003: funds from industry Alcon, Allergan, Merck, Pfizer 2005: it nearly happened 2007: it nearly happened (again) 2008: it really happened.

Glaucoma and black ancestry

Survey of Ophthalmology (2003)

St Lucia Study Ophthalmology (1989) Baltimore Eye Survey Am J Epidem (1991) The Barbados Eye Study Arch Ophth 1994)

Glaucoma and black ancestry

Survey of Ophthalmology (2003)

prevalence 3 - 6× higher than in Caucasians earlier onset & more rapid progression 5× larger prevalence of ocular hypertension (OHT) ↑ risk of progression from OHT to glaucoma ↑ rate of glaucoma-related blindness

Glaucoma in the Caribbean St Lucia Study Ophthalmology, 1989 Sep;96(9):1363-8 1679 individuals, aged 30+ years VA, IOP, C/D ratio 1/3 had supra-threshold screening fields on HFA positives underwent definitive exam, including threshold fields

Prevalence of 8.8% in the 30+y population.

What is Screening? Identify people who probably have a disease from those that probably do not.

Glaucoma screening: worthwhile? … an important health problem. … an accepted treatment. … natural history well understood. … a latent or early symptomatic stage. … a suitable screening test. … treatment should be available. … agreed policy on whom to treat as patients. … early treatment of benefit. … cost economical. … a continuing process. WHO criteria, after Wilson and Jungner (1968)

Glaucoma screening: worthwhile?

S Hatt, R Wormald, J Burr

Cochrane Database of Systematic Reviews 2008 Screening for prevention of optic nerve damage due to chronic open angle glaucoma

Glaucoma screening: worthwhile? S Hatt, R Wormald, J Burr

Cochrane Database of Systematic Reviews 2008 Screening for prevention of optic nerve damage due to chronic open angle glaucoma Main results

“As no trials were identified, no formal analysis was performed.”

Glaucoma screening: worthwhile? S Hatt, R Wormald, J Burr

Cochrane Database of Systematic Reviews 2008 Screening for prevention of optic nerve damage due to chronic open angle glaucoma Main results

“As no trials were identified, no formal analysis was performed.”

The Bottom Line •

Screening can be cost-effective in highrisk populations.

•

Most economic evaluations compare to current model of routine case-finding by optometrists, which does not exist in Caribbean.

•

Screening tests need very high specificity to be workable.

A good screening program… simple, cheap, and accessible in peripheral health centres rely on local expertise (nurses, assistants)

good sensitivity, and very high specificity false-positive rate <2% more false-positive cases – negative impact

Brain Teaser Sensitivity = 50% Specificity = 95% Prevalence = 0.3%

Brain Teaser Sensitivity = 50% Specificity = 95% Prevalence = 0.3% What is the probability that a patient with a positive test has the disease?

5% Doctors with an average of 14 yrs experience Answers ranged from 1% to 99% half of them estimating the probability as 50% Gigerenzer, BMJ 2003;327:741-744

Fagan Nomogram

Fagan Nomogram

Aim - St Kitts Eye Study

help establish a robust and effective screening program for St Kitts and wider Caribbean region

Questions - St Kitts Eye Study Which tests provide high specificity and good sensitivity, in a Caribbean population? Which combination of tests provides the best trade-off between performance and effort? Can new technologies (eg imaging) improve on the current standard of care?

Objectives – St Kitts Eye Study Examine a representative sample of 200 individuals >50 yrs with screening tests as well as “gold standard” protocol. Establish combination of screening tests that provides specificity >98%. Establish criteria for referral to Eye Centre.

Design – St Kitts Eye Study random sample of St Kitts residents (n=370) drawn from Social Security list. invited to participate by letter from Ministry of Health complete protocol of tests, including screeningand “gold standard” tests

Visual Fields Frequency Doubling (“Matrix”) Perimetry Moorfields Motion Displacement Perimetry Suprathreshold (white-on-white) Perimetry (all screening tests on one eye only)

Humphrey 24-2 Sita-Standard (both eyes)

Tonometry

EasyEye NCT (Keeler) Tonopen (Reichert) Goldmann Applanation Tonometry (GAT)

Imaging Heidelberg Retina Tomograph

Imaging

rim area

cup area

Initial Findings Invited: 373 individuals (169 women, 204 men) age range 50 – 87 yrs Participated: 172 individuals (46%) of those invited 44 individuals (opportunistic) 208 (96%) completed entire program

Initial Findings Prevalence of glaucoma 18/172 = 10.5% 8 previously unknown (44%) Prevalence of Ocular Hypertension 15/172 = 9% 12 previously unknown (80%)

Initial Findings Other conditions Pterygium: almost universal

Initial Findings Other conditions Cataract: ~25%

Online on www.pdfcoke.com

Where do we go from here? Investigate best combination of tests Report to Ministry of Health, St Kitts and Nevis, with suggested paradigm and cost estimates. Help local optometrists to implement opportunistic screening.

Younes Agoumi, Carol Beattie, Beulah & Terrela Byron, Balwantray Chauhan, Anthony Crouse, Stacey Durling, Marcelo Nicolela, Glen Sharpe