Anterior segment Scheimpflug imaging for screening angle closure diseases Andrew Winegarner1,, Atsuya Miki1, Miho Kumoi1, Yuchiro Ishida1, Taku Wakabayashi1, Shinichi Usui1, Kenji Matsushita1, Kohji Nishida1 1Department of Ophthalmology Osaka University Graduate School of Medicine Introduction Results PACG affects approximately 0.75% of all adult Asians with rates doubling every decade, and affects 0.4% of all European-descent adults over the age of 40 Gonioscopic examination is the gold standard for the diagnosis of PACG. However, it requires a highly-trained ophthalmologist, direct contact with the eyeball, and results are not easily reproducible by unskilled examiners. Anterior segment Scheimpflug imaging offers a noninvasive means to quantitatively assess anterior chamber parameters in an automated and standardized manner. Technicians would require minimal training and be able to screen and refer suspected cases of PACG to an ophthalmologist for proper diagnosis. Normative data on anterior chamber parameters such as depth, volume, and angle have been generated from two previous studies and included in the Pentacam Scheimpflug imaging device. Patient’s individual data may be analyzed against the normative data directly on the device. We have used the normative data as screening tool on our own patient population to both further validate the normative data, and test the feasibility of establishing a screening protocol. We generated our own normative data for comparison with previous normative data. 2 Representative control case for Scheimpflug imaging data page Representative patient case for Scheimpflug imaging data page Normative Data Screen Methods & Materials 88 consecutive patients with gonioscopy-diagnosed angle closure diseases (PACS, PAC, and PACG) and Scheimpflug imaging data were retroactively surveyed. 35 healthy control subjects were analyzed via Scheimpflug imaging for comparison. The analyzing software of the Pentacam Scheimpflug imaging device provides threshold values (standard deviations) based on the normative data. We used 1 SD from the normative mean values (depth ≤ 2.37mm, volume ≤ 111 mm2, and angle ≤ 31degrees) as cut-off points for delineating between angle closure disease and those not at risk for PACG. The raw data from the present study was analyzed via ROC curves in order to generate new cut-off values to compare with previous studies’ sensitivity and specificity. Exclusion criteria included intraocular diseases such as a history of intraocular surgery, history of laser iridotomy, secondary glaucoma, and being over the age of 90 and under the age of 40. Cataract and epiretinal membrane cases were not excluded. Variables of age, axial length, spherical equivalent, ACD, ACV, and ACA were compared, with P-value less than 0.05 considered significant. ROC Curves TABLE 1. Clinical characteristics Total Angle Closure Control P Value Eyes / Subjects 122 / 122 87 / 87 35 / 35   Age, years (range) 72.1 ± 7.7 (49 – 87) 72.3 ± 7.7 (49 – 87) 71.6 ± 8 (56–87) 0.6403 Gender, female / male 80 / 42 62 / 25 18 / 17 0.037 Eye, right / left 64 /58 50 / 37 14 / 21 0.081 Axial Length, mm (range) 23.1 ± 1.5 (20.5 – 27.8) 22.5 ± 0.8 (20.5 – 24.4) 24.7 ± 1.6 (20.8 – 27.8) <0.001 Spherical equivalent refraction (range) -0.2 ± 3.1 (-10.6 – 5) 0.9 ± 1.9 (-5.4 – 5) -2.8 ± 4 (-10.6 – 4.4) Anterior chamber depth, mm (range) 2.12 ± 0.61 (1.26 – 3.97) 1.8 ± 0.27 (1.26 – 2.51) 2.92 ± 0.47 (1.97 – 3.97) Anterior chamber volume, mm2 (range) 88.8 ± 45.6 (29 – 244) 65.1 ± 17.3 (29 – 122) 147.7 ± 40.2 (75 – 244) Anterior chamber angle, degree (range) 25.0 ± 7.8 (9.2 – 45.7) 21.6 ± 5.7 (9.2 – 34.2) 33.7 ± 5.4 (20.8 – 45.7) Depth Volume  Table 2. Sensitivity and Specificity Sensitivity with 1 SD normative Specificity with ROC analysis Depth 97.7% 91.4% 95.4% 94.3% Volume 98.9% 71.4% Angle 88.5% 85.7% Angle Conclusions Previous studies’ normative data have been incorporated into the Pentacam Scheimpflug image analyzing software, so the technician may easily determine whether the values of the examined eyes fall within the normal limits (Fig. 1c). Technicians may noninvasively screen for angle closures with automated and standardized Scheimpflug imaging, which takes under 5 minutes per patient. Positive screens may be referred to an ophthalmologist for proper diagnosis via gonioscopy. In conclusion, our study clarified the excellent discriminative performance of the anterior segment Scheimpflug imaging parameters for angle closure diseases. Using the integrated thresholds generated from previous studies’ normative data, we accurately discriminated angle closure diseases from normal subjects. Our study confirmed the relevance of using these threshold values as screening tools in a large patient population, distinct from the one used in the normative data’s creation. Additionally, cut-off points generated from our own raw data yielded even better sensitivity and specificity. Our data strongly support the use of Scheimpflug imaging for screening angle closure diseases. References Study was undertaken to assess the discriminative power of anterior chamber parameters obtained with the anterior segment Scheimpflug imaging in screening angle closure diseases. Using 1 SD from the mean anterior chamber depth in normative data, angle closure patients were screened with a 97.7% sensitivity, and a 91.4% specificity. This study provides a larger population of patients with angle closure diseases than previous studies using anterior segment Scheimpflug imaging. It is the first study to validate the incorporated normative data with a separate patient population. Study’s limitation is all patients were taken from a university hospital setting, but we still believe these numbers to sufficient for screening purposes, especially given that the cut-off points used were not generated from the population being screened, excluding the possibility of an over-fitting. 1. S. Glaucoma is the second leading cause of blindness globally. Bull World Health Organ. 2004 Nov;82 (11): 887-8 2. Kingman Gupta P, Zhao D, Guallar E, et al. Prevelance of Glaucoma in the United States: The 2005-2008 National Health and Nutrition Examination Survey. Invest Ophthalmol Vis Sci. 2016 May; 57(6): 2577-2585 3. Cheng J, Zong Y, Zeng Y, et al. The Prevalence of Primary Angle Closure Glaucoma in Adult Asians: A Systematic Review and Meta-Analysis. Ed. Ted S. Acott. PLoS ONE. 2014 Jul 24;9(7) 4. Day A, Baio G, Gazzard G, et al. The prevalence of primary angle closure glaucoma in European derived populations: a systemic review. Br J Ophthalmol. 2012 Sep; 96(9):1162-7 5. Aung T, Friedman DS, Chew PT et al. Long-term outcomes in Asians after acute primary angle closure. Ophthalmology. 2004;111: 1464–1469 6. Weinreb RN, Healey PR, Topouzis F. Glaucoma Screening. World Glaucoma Association WGA Concensus series 5. 2008. 7. Foster PJ, Buhrmann R, Quigley HA, et al. The definition and classification of glaucoma in prevalence surveys. Br J Ophthalmol. 2002 Feb;86(2):238-42. 8. Thomas R, George R, Parikh R, et al. Five year risk of progression of primary angle closure suspects to primary angle closure: a population based study. Br J Ophthalmol. 2003;87:450–454. 9. Thomas R, Parikh R, Muliyil J, et al. Five-year risk of progression of primary angle closure to primary angle closure glaucoma: a population-based study. Acta Ophthalmol Scand. 2003;81:480–485. 10. Jain R, Grewal SPS. Pentacam: Principle and Clinical Application. J Curr Glaucoma Pract. 2009; 3(2):20-32 11. Georgios L, Maria G, Andreas K, et al. Anterior chamber volume measurements with Visante optical coherence tomography and Pentacam: repeatability and level of agreement. Clin Experiment Ophthalmol. 2009;37:772–774. 12. Shankar H, Taranath D, Santhirathelagan CT, et al. Anterior segment biometry with the Pentacam: comprehensive assessment of repeatability of automated measurements. J Cataract Refract Surg. 2008;34:103–113 13. Kurita N, Mayama C, Tomidokoro A, et al. Potential of the pentacam in screening for primary angle closure and primary angle closure suspect. J Glaucoma. 2009 Sep; 18(7): 506-12 14. Hong S, Yi J, Kang SY, et al. Detection of Occludable Angles with the Pentacam and the Anterior Segment Optical Coherence Tomography. Yonsei Med J. 2009 Aug 31: 50(4): 525-528 15. Grewal DS, Brar GS, Jain R, et al. Comparison of Scheimpflug imaging and spectral domain anterior segment optical coherence tomography for detection of narrow anterior chamber angles. Eye (Lond). 2011 May; 25(5): 603-11 16. Koç M, Özülken K, Ayar O, et al. Measurement of the anterior chamber angle according to quadrants and age groups using Pentacam Scheimpflug camera. J Glaucoma. 2013 Mar; 22(3): 226-9 17. Dabasia PL, Edgar DF, Murdoch IE, et al. Noncontact Screening Methods for the Detection of Narrow Anterior Chamber Angles. Invest Ophthalmo Vis Sci. 2015 Jun; 56 (6): 3929-35 18. Rabsilber TM, Khoramnia R, Auffarth GU. Anterior chamber measurement using Pentacam rotating Scheimpflug camera. J Cataract Refract Surg. 2006 Mar;32(3): 456-9 19. Pakravan M, Sharifipour F, Yazdani S, et al. Scheimpflug imaging criteria for identifying eyes at high risk of acute angle closure. J Ophthalmic Vis Res. 2012 Apr; 7(2): 111-7 20. R Core Team (2016). R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. URL https://www.R-project.org/. 21. Herman C. What makes a screening exam “good”?. Virtual Mentor 2006 Jan 1;8(1): 34-7