An algorithm for glaucoma screening in clinical settings and its preliminary performance profile

Abstract

Purpose: To devise and evaluate a screening algorithm for glaucoma in clinical settings.

Methods: Screening included examination of the optic disc for vertical cupping (≥0.4) and asymmetry (≥0.15), Goldmann applanation tonometry (≥21 mmHg, adjusted or unadjusted for central corneal thickness), and automated perimetry. In the diagnostic step, retinal nerve fiber layer imaging was performed using scanning laser polarimetry. Performance of the screening protocol was assessed in an eye hospital-based program in which 124 non-physician personnel aged 40 years or above were examined. A single ophthalmologist carried out the examinations and in equivocal cases, a glaucoma subspecialist's opinion was sought.

Results: Glaucoma was diagnosed in six cases (prevalence 4.8%; 95% confidence interval, 0.01-0.09) of whom five were new. The likelihood of making a definite diagnosis of glaucoma for those who were screened positively was 8.5 times higher than the estimated baseline risk for the reference population; the positive predictive value of the screening protocol was 30%. Screening excluded 80% of the initial population.

Conclusion: Application of a formal screening protocol (such as our algorithm or its equivalent) in clinical settings can be helpful in detecting new cases of glaucoma. Preliminary performance assessment of the algorithm showed its applicability and effectiveness in detecting glaucoma among subjects without any visual complaint.

Keywords: Chronic Glaucoma; Clinical Setting Screening; Glaucoma Screening; Screening Algorithm; Screening Test Performance.

Figure 1

Screening and diagnostic algorithm for glaucoma; the algorithm consisted of serial and simultaneous combinations of tests. The authors did their best to objectify their approach but not all the clinical acumen can be incorporated in the form of an algorithm and clinicians should employ their intuition in practice. Note that there were 26 abnormal screening findings in 20 subjects. Gonioscopy was performed in the Diagnosis stage. CCT, central corneal thickness; IOP, intraocular pressure; cIOP, CCT-adjusted IOP; VCDR, vertical cup disc ratio; CDR, cup-disc ratio; SITA, Swedish Interactive Threshold Algorithm; OHT, ocular hypertension; NTG, normal tension glaucoma