Diagnostic Accuracy of Nonmydriatic Fundus Photography for the Detection of Glaucoma in Diabetic Patients

Evaluating the outcome of screening for glaucoma using colour fundus photography-based referral criteria in a teleophthalmology screening programme for diabetic retinopathy

AIMS

To evaluate the effectiveness of glaucoma screening using glaucoma suspect (GS) referral criteria assessed on colour fundus photographs in Singapore's Integrated Diabetic Retinopathy Programme (SiDRP).

METHODS

A case-control study. This study included diabetic subjects who were referred from SiDRP with and without GS between January 2017 and December 2018 and reviewed at Singapore National Eye Centre. The GS referral criteria were based on the presence of a vertical cup-to-disc ratio (VCDR) of ≥0.65 and other GS features. The final glaucoma diagnosis confirmed from electronic medical records was retrospectively matched with GS status. The sensitivity, specificity and positive predictive value (PPV) of the test were evaluated.

RESULTS

Of 5023 patients (2625 with GS and 2398 without GS) reviewed for glaucoma, 451 (9.0%, 95% CI 8.2% to 9.8%) were confirmed as glaucoma. The average follow-up time was 21.5±10.2 months. Using our current GS referral criteria, the sensitivity, specificity and PPV were 81.6% (95% CI 77.7% to 85.1%), 50.6% (95% CI 49.2% to 52.1%) and 14.0% (95% CI 13.4% to 14.7%), respectively, resulting in 2257 false positive cases. Increasing the VCDR cut-off for referral to ≥0.80, the specificity increased to 93.9% (95% CI 93.1% to 94.5%) but the sensitivity decreased to 11.3% (95% CI 8.5% to 14.6%), with a PPV of 15.4% (95% CI 12.0% to 19.4%).

CONCLUSIONS

Opportunistic screening for glaucoma in a lower VCDR group could result in a high number of unnecessary referrals. If healthcare infrastructures are limited, targeting case findings on a larger VCDR group with high specificity will still be beneficial.

Validation of a portable, non-mydriatic fundus camera compared to gold standard dilated fundus examination using slit lamp biomicroscopy for assessing the optic disc for glaucoma

Purpose

To evaluate the sensitivity and specificity of a portable non-mydriatic fundus camera to assess the optic disc for glaucoma.

Methods

We conducted a single-site, cross-sectional, observational, instrument validation study. Non-mydriatic fundus photographs centred at the optic disc were obtained from 276 eyes of 68 glaucoma and 70 normal patients, using a portable fundus camera (Smartscope, Optomed, Oulu, Finland). A senior Glaucoma consultant, masked to the patient’s study participation, performed a gold standard dilated fundus examination to make the diagnosis of glaucoma. Following this, a mydriatic photograph was taken by a standard table-top fundus camera. All the images were digitalized and de-identified by an independent investigator and presented to two remote graders, masked to the patients, their diagnoses, and photographic modality. Based on individual disc characteristics, a diagnosis of screening positive or negative for glaucoma was made. In the end, the independent investigator re-identified the images. Sensitivity and specificity to detect glaucoma with the undilated Smartscope camera was calculated compared to dilated fundus examination.

Results

Grading remote images taken with the portable non-mydriatic fundus camera showed a sensitivity of 96.3% (95% confidence interval (CI): 91.6–98.8%) and 94.8% (95% CI: 89.7–97.9%) and a specificity of 98.5% (95% CI: 94.9–99.8%) and 97.8% (95% CI: 93.9–99.6%) for the two graders respectively as compared to gold standard dilated fundus examination.

Conclusion

The non-mydriatic Smartscope fundus images have high sensitivity and specificity for diagnosing glaucoma remotely and thus may be an effective tool for use in community outreach programs.

Evolution of optic nerve photography for glaucoma screening: a review

Visual evaluation of the optic nerve has been one of the earliest and most widely used methods to evaluate patients for glaucoma. Photography has proven very useful for documentation of the nerve's appearance at a given time, allowing more detailed scrutiny then, and later comparison for change. Photography serves as the basis for real-time or non-simultaneous review in telemedicine and screening events allowing fundus and optic nerve evaluation by experts elsewhere. Expert evaluation of disc photographs has shown diagnostic performance similar to other methods of optic nerve evaluation for glaucoma. Newer technology has made optic nerve photography simpler, cheaper and more portable creating opportunities for broader utilization in screening in underserved populations by non-physicians. Recent investigations suggest that non-physicians or software algorithms for disc photograph evaluation have promise to allow more screening to be done with fewer experts.

Validity of code based algorithms to identify primary open angle glaucoma (POAG) in Veterans Affairs (VA) administrative databases

PURPOSE

The validity of the International Classification of Diseases, 9th revision, Clinical Modification (ICD-9) code for primary open angle glaucoma (POAG) in the Department of Veterans Affairs (VA) electronic medical record has not been examined. We determined the accuracy of the ICD-9 code for POAG and developed diagnostic algorithms for the detection of POAG.

METHODS

We conducted a retrospective study of abstracted data from the Michael E. DeBakey VA Medical Center's medical records of 334 unique patients with at least one visit to the Eye Clinic between 1999 and 2013. Algorithms were developed to validly identify POAG using ICD-9 codes and pharmacy data. The positive predictive value (PPV), negative predictive value (NPV), sensitivity, specificity and percent agreement of the various algorithms were calculated.

RESULTS

For the ICD-9 code 365.1x, the PPV was 65.9%, NPV was 95.2%, sensitivity was 100%, specificity was 82.6%, and percent agreement was 87.8%. The algorithm with the highest PPV was 76.3%, using pharmacy data in conjunction with two or more ICD-9 codes for POAG, but this algorithm also had the lowest NPV at 88.2%.

CONCLUSIONS

Various algorithms for identifying POAG in the VA administrative databases have variable validity. Depending on the type of research being done, the ICD-9 code 365.1x can be used for epidemiologic or health services database research.

Evidence for Telemedicine for Diabetic Retinal Disease

According to current projections, the number of Americans with diabetes mellitus will increase from 27.8 million in 2007 to 60.7 million in 2030. With the increasing gap between demand for eye care and supply of ophthalmologists and optometrists, and the non-uniform distribution of eye care providers in US counties, barriers to eye examinations will likely increase. Telemedicine assessment of diabetic retinal disease through remote retinal imaging and diagnosis has the potential to meet these growing demands. To establish evidence for a telemedicine program as an effective modality for diabetic retinopathy (DR) assessment, the interpretation of teleretinal images should compare favorably with Early Treatment Diabetic Retinopathy Study film or digital photographs. We review the current evidence on the critical features and characteristics of ocular telehealth programs for DR in the following categories: image gradability, mydriasis, sensitivity and specificity, cost-effectiveness, long-term effectiveness, patient comfort and satisfaction, and improvement of patient related outcomes.