Correlation between clinic-measured intraocular pressure (IOP) and disease progression in primary angle closure glaucoma (PACG)

Participants will attend a study visit every 6 months for 5 years, in addition to their usual follow-up at Hong Kong Eye Hospital. The following information will be collected for each patient: - Hospital number (No Hong Kong ID number will be collected) - Date of birth - Date of diagnosis of PACG - Date of any previous acute primary angle closure (APAC) - Date of any previous argon laser peripheral iridoplasty (ALPI) - Date of laser peripheral iridotomy (PI) - Date of any previous cataract surgery - Date of any previous glaucoma surgery - Any co-existing cataract, diabetic retinopathy / maculopathy, age-related macular degeneration, or other eye diseases that may affect visual acuity or visual field A systemic medical history is taken, with specific reference to history of: - Hypertension (HT) - Diabetes mellitus (DM) - Hyperlipidemia (HL) - Ischemic heart disease (IHD) - Cerebrovascular accident (CVA) - Cancer - Smoking - Number of cigarettes per day - Number of years of smoking - Number of years since quitting smoking - Any secondary smoking - Any family history of PACG / glaucoma Ophthalmic examinations and investigations at recruitment by trained research personnel and optometrists: - Date of study examination - Best-corrected Snellen visual acuity and spherical refractive error - Clinic-measured intraocular pressure (IOP) - measured with a Goldmann applanation tonometer on a slit-lamp biomicroscope. The reading in mm Hg is rounded to the next higher integer. Each measurement is repeated, and if the two readings differ by 3 mm Hg or more, a third measurement is taken. The median of the two or three measurements becomes the IOP determination. - The number of IOP-lowering drugs (topical and systemic) - Central corneal thickness and axial length by ultrasonography - Central corneal endothelial cell count by specular microscopy (SM) - Gonioscopic examination of angle structures, and grading by the Shaffer system - Anterior segment imaging by Anterior Segment Optical Coherence Tomography (AS-OCT) using the Visante™ OCT (Carl Zeiss Meditec, Dublin, California, USA). The Irido-Corneal Tools Module of the Visante™ OCT will be used to document the following drainage angle parameters: Angle Opening Distance (AOD), the Trabecular Iris Space Area (TISA), the Angle Recess Area (ARA), the Scleral Spur Angle and the Trabecular Iris Contact Length (TICL). - Vertical cup-to-disc ratio, and other optic disc changes suggestive of glaucoma - Optic disc imaging by Cirrus™ Spectral Domain HD-OCT (Carl Zeiss Meditec, Dublin, California, USA) - Automated perimetry using the Humphrey Field Analyzer II (Carl Zeiss Meditec, California, USA) (central 24-2 threshold test, Sita standard strategy, size III white stimulus, with the foveal threshold test turned on) - Retinal nerve fiber layer thickness measurement by Optical Coherence Tomography III (OCT III) imaging system (Stratus OCT, Carl Zeiss Meditec, Dublin, California, USA) Data collection at follow up All recruited patients will be followed up in the Glaucoma Clinics at Hong Kong Eye Hospital and Prince of Wales Hospital for 5 years. Gonioscopy for angle assessment and documentation of optic nerve head appearances (including vertical cup-to-disk ratios) will be performed at least once a year as per hospital protocol. During follow up, patients will be prescribed IOP-lowering drugs, and advised surgery (phacoemulsification, trabeculectomy, or combined phaco-trabeculectomy), as clinically indicated. The goal of IOP-lowering treatment is to achieve an IOP of 21 mmHg or below, as per hospital protocol. Documentation of IOP All recruited PACG patients will be seen 3-monthly in the HKEH Glaucoma Clinic, with documentation of bilateral IOP. IOP is measured with a Goldmann applanation tonometer on a slit-lamp biomicroscope. The reading in mm Hg is rounded to the next higher integer. Each measurement is repeated, and if the two readings differ by 3 mm Hg or more, a third measurement is taken. The median of the two or three measurements becomes the IOP determination. Documentation of disease progression All recruited PACG patients will attend 6-monthly study visits. Although patients may be seen between study visits, data from these examinations were not routinely collected. Examinations and investigations at each study visit will include: 1. Documentation of optic nerve head appearance, in particular the vertical cup-to-disc ratio (VCDR) 2. Automated perimetry using the Humphrey Field Analyzer II (Carl Zeiss Meditec, Dublin, California, USA) (central 24-2 threshold test, Sita standard strategy, size III white stimulus, with the foveal threshold test turned on) 3. Retinal nerve fiber layer thickness measurement by Optical Coherence Tomography III (OCT III) imaging system (Stratus OCT, Carl Zeiss Meditec, Dublin, California, USA) All these examinations and investigations are non-invasive, and are standard follow-up routines for all glaucoma patients. Participation in this study would require performance of visual field examination and retinal nerve fiber layer thickness scan at slightly higher frequency than normally required for clinical management. In routine clinical management, such investigations are usually performed at least once a year, and often more frequently in advanced or unstable patients. Performing these investigations more frequently may allow earlier detection and confirmation of glaucomatous progression. Three strategies will be employed to detect disease progression: 1. Structural assessment - Retinal nerve fiber layer thickness measurement by Optical Coherence Tomography III (OCT III) imaging system (Stratus OCT, Carl Zeiss Meditec, Dublin, California, USA) The GPA™ Advanced Serial Analysis software (Advanced Analysis Package of Stratus OCT™ Software Version 5.0) in the Stratus OCT will be used to quantify the progressive thinning of the retinal nerve fiber layer thickness, and also for analysis of statistical significance. 2. Functional assessment 1 – Automated perimetry using the Humphrey Field Analyzer II (Carl Zeiss Meditec, Dublin, California, USA) (central 24-2 threshold test, Sita standard strategy) with Visual Field Defect Scoring (VFDS) Visual Field Defect Scoring (VFDS), as defined and used in the Advanced Glaucoma Intervention Study (AGIS) for POAG, will be used to score Humphrey Field Analyzer II (Carl Zeiss Meditec, Dublin, California, USA) printouts (central 24-2 threstold test, Sita standard strategy, size III white stimulus, with the foveal threshold test turned on). VFDS range from 0 (no defect) to 20 (end-stage). If an eye has insufficient vision for a patient to count fingers at 30 cm, the visual field defect score is recorded as 20.The method of analysis used in AGIS will be repeated to compare the correlations between IOP and disease progression in POAG and PACG. 3. Functional assessment 2 – Automated perimetry using the Humphrey Field Analyzer II (Carl Zeiss Meditec, Dublin, California, USA) (central 24-2 threshold test, Sita standard strategy) with Guided Progression Analysis (GPA™) software (Carl Zeiss Meditec, Dublin, California, USA) The Humphrey Guided Progression Analysis (GPA™) software in the Humphrey Field Analyzer II (Carl Zeiss Meditec, Dublin, California, USA) is derived from the analysis used in the EMGT study. The GPA software uses the pattern deviation plot, point-by-point, to detect progression. It will be used in this study to quantify the progressive deterioration in visual field / retinal sensitivity to light, and also for analysis of statistical significance.