Vision screenings and community-based eye examinations can be done at relatively low cost.

The mean total time to complete each vision screening visit was 22.7 minutes, at a recurring cost of $7.78 in PTGDFS.⁵ The total cost for each participant who completed both a vision screening and confirmatory eye examination and was diagnosed with an ocular condition was $64.44 in PTGDFS.⁵ These costs exclude space shared by the local health centers as well as the more limited equipment costs associated with screening examinations as opposed to comprehensive ophthalmic testing.

If most participants are insured, institutions engaged in vision screening have the potential to capture revenue when conducting subsequent definitive examinations and surgeries for those that screen positive, reducing financial barriers to conducting screenings. The majority (93%) of screened participants from these two underserved settings were insured despite having low income levels (45% of participants in the SToP Glaucoma study had annual income <$10,000).³ This highlights the complex barriers to healthcare utilization, even after barriers to obtaining insurance are surpassed.

Unreadable fundus images captured during community-based vision screenings warrant referral for a complete eye examination, as rates of ocular pathology were high in this group.

A total of 65% of those with unreadable images were eventually diagnosed with at least one eye condition in the PTGDFS (most frequently cataracts, followed by glaucoma suspects and narrow angles).⁶

Participants with ungradable images in the SToPGS were less likely to have glaucoma but had similar prevalence of eye conditions compared to those referred for other reasons.³

The value of measuring intraocular pressure (IOP) during glaucoma screening is uncertain; optic nerve examination is more likely to detect glaucoma. That said, identifying participants with very high IOP can identify those at high risk for glaucoma.

In the PTGDFS, 1.7% of those screened had IOP >30 mmHg in at least one eye and were placed in the Fast Track protocol for treatment.⁷

18% of participants had IOP 22–29 mmHg in at least one eye.⁷ In the SToPGS, 13% of participants had IOP >22 mmHg.

Seven percent of participants were referred for follow-up eye examination based solely on IOP >21 mmHg or IOP > 22mH in at least one eye in the PTGDFS⁷ and SToPGS study³, respectively.

However, an initial IOP >21 mmHg in PTGDFS, without suspicious optic nerves, did not significantly increase the odds of being diagnosed with glaucoma at the follow-up eye examination (OR 1.17, 95% CI 0.29–4.16).

On the other hand, having an IOP >21 mmHg was associated with increased odds of being diagnosed with glaucoma in participants who also had suspicious nerves on fundus photography [OR 4.48, 95% CI, 1.50–13.93;P=0.007].

Screening for vision-threatening diseases carries more impact compared to screening for glaucoma alone.

These underserved populations had high rates of ocular pathology; 40% of participants in SToPGS and 60% in PTGDFS failed the vision screening.^{3, 4}

Screening for reduced visual acuity identified cataracts. Given that the at risk population was mostly insured, identifying and operating on visually significant cataracts can not only improve quality of life, but also offset costs of the screening itself.

Of the participants that completed a follow-up eye examination by an ophthalmologist in PTGDFS, 77% were diagnosed with cataracts, of which 14% had visually significant cataracts.⁸ Similarly 40% of participants referred for a definitive eye examination in the SToPGS had visually significant cataracts, of which 36% had subsequent cataract surgery in at least one eye.³

Signficant retinal disease and uncorrected refractive error can be identified without additional cost or equipment.

SToPGS identified diabetic retinopathy (1.1%), age-related macular degeneration (0.3%), and uncorrected refractive error (11.9%).³

PTGDFS identified diabetic retinopathy (11.3%), and other retinal abnormalities (7.5%).⁴

The disparity in the frequency of identification of other common pathologies amongst these studies highlights the importance of choosing methodology that fits screening goals. PTGDFS had greater rate of diabetic retinopathy likely related to higher rate of diabetes (58.7%) and inclusion of anyone >40 years old with a family history of glaucoma or diabetes. On the other hand, SToPGS identified significant refractive error due to methodology that specifically used an autorefractor when best-corrected visual acuity was worse than 20/40 and mailed prescription glasses to those that only screened positive for refractive error.

Screening without gonioscopy still allows many glaucoma suspects with narrow angles to be identified on follow-up complete eye examinations.

Gonioscopy can identify angle closure but is currently impractical in a vision screening protocol; it is recommended for those who fail screening.

Narrow angles were seen at higher rates than anticipated on confirmatory eye examinations in PTGDFS. Thirty-two participants (3.5%) were diagnosed with anatomically narrow angles during confirmatory examination that was recommended due to either solely IOP >21 mmHg or unreadable images. ^{6, 7} Untreated, these participants are at risk for acute or chronic angle closure glaucoma.

The Zhongshan Angle Closure Prevention (ZAP) trial⁹ suggests that narrow angles in the absence of other findings are unlikely to lead to substantial vision loss in 6 years in the vast majority of cases in a Chinese population; however it is unclear whether this remains true past 6 years or in other ethnicities.

Focus on improving adherence to follow-up eye examinations:

Shorter distance between the vision screening and follow-up site was associated with greater adherence to confirmatory eye examination in SToPGS.¹¹

Participants with vision impairment and/or abnormal macula on ocular photography were more likely to return for a follow-up examination in SToPGS.¹¹ This highlights the importance of educational interventions to improve awareness of the gravity of asymptomatic eye diseases.

Several strategies were employed during the second phase of SToPGS that contributed to significantly improved follow-up: pre-scheduled follow-up appointments soon after the screening, educational videos, multiple reminder calls, and the use of vouchers that stated the value of the examination. Despite this, 43% of invited participants did not return for a follow-up eye examination in SToPGS.

The PTGDF found that patient navigators and social workers improved timely attendance at the first followup after the confirmatory eye examination (74.4% vs. 39.0%; aRR=1.85; 95% CI 1.51–2.28; P<.001; data not published) ¹²,¹³