Development and evaluation of Order of Magnitude (OM): a virtual reality-based visual field analyzer for glaucoma detection.

PURPOSE: This study introduces the Order of Magnitude (OM), a cost-effective, indigenous, virtual reality-based visual field analyzer designed for detecting glaucomatous visual field loss. METHODS: The OM test employs a two-step supra-thresholding algorithm utilizing stimuli of 0.43°diameter (equivalent to Goldmann size III) at low and high thresholds. A comparative analysis was conducted against the Humphrey visual field (HVF) test, considered the gold standard in clinical practice. Participants, including those with glaucoma and normal individuals, underwent comprehensive eye examinations alongside the OM and HVF tests between April and October 2019. Diagnostic sensitivity and specificity of the OM test were assessed against clinical diagnoses made by specialists. RESULTS: We studied 157 eyes (74 glaucomatous, 83 control) of 152 participants. Results demonstrated a high level of reliability for both OM and HVF tests, with no significant difference observed (P = 0.19, Chi-square test). The sensitivity and specificity of the OM test were found to be 93% (95% CI 86-100%) and 83% (95% CI 72.4-93%), respectively, while the HVF test showed sensitivity and specificity of 98% (95% CI 93.9-100%) and 83% (95% CI 73.9-92.8%), respectively. CONCLUSION: These findings suggest that the OM test is non-inferior to the reference standard HVF test in identifying glaucomatous visual field loss.

Comparison of Scleral Tono-Pen Intraocular Pressure Measurements with Goldmann Applanation Tonometry.

SIGNIFICANCE: Measuring the intraocular pressure (IOP) on the sclera can be an alternative to conventional corneal measurement in eyes with scarred corneas. However, these measurements have to be evaluated prior in normal eyes. Our study aimed to evaluate scleral IOP using Tono-Pen and compared it with corneal Goldmann applanation measurements. PURPOSE: The aim of this study was to evaluate the ability of limbal and scleral Tono-Pen IOP readings to predict central corneal Goldmann applanation tonometry (GAT) readings in eyes with normal corneas. METHODS: In a cross-sectional study, 115 eyes of 115 patients attending a tertiary eye care center underwent GAT on the central cornea followed by Tono-Pen readings at the central cornea, at the limbus, and at the sclera. Bland-Altman plots were used to determine the agreement between different methods of IOP measurement. RESULTS: The median IOP (interquartile range) by GAT performed on the central cornea was 18 (16, 24) mmHg, and the IOP ranged from 10 to 54 mmHg. The median IOPs (interquartile range) by Tono-Pen obtained at central cornea, limbus, and sclera were 16 (13, 23), 23 (17, 28), and 33 (27, 44) mmHg, respectively. The Pearson correlation coefficient and the 95% limits of agreement between GAT readings and Tono-Pen readings at the central cornea were 0.9 (P < .001) and -4.9 to 8.74 mmHg, respectively. The correlation coefficient between GAT readings and Tono-Pen readings at the limbus and GAT readings and Tono-Pen readings at the sclera was 0.46 (P < .001) and 0.23 (P = .01), respectively. The 95% limits of agreement between these pairs of readings were -20.55 to 13.66 and -44.02 to 13.37 mmHg, respectively. CONCLUSIONS: This study showed limited ability of Tono-Pen readings obtained at the limbus and sclera to predict the central corneal GAT IOP readings in eyes with normal corneas at various IOP ranges.

Six-year incidence of visually significant age-related cataract: the Chennai eye disease incidence study.

BACKGROUND: The aim of this study is to report the 6-year incidence of age-related cataract in a population-based study. DESIGN: The design used is a population-based cohort study. PARTICIPANTS: A cohort of 2484 phakic subjects, aged 40 years and above at baseline, from a south Indian population was included in the study. METHODS: Bilateral phakics with visual acuity of 6/12 or better and cataract less than N2, C2 and P2 on the Lens Opacities Classification System II at baseline were included. Subjects with glaucoma and corneal or retinal diseases were excluded. Incident visually significant cataract was defined as visual acuity of less than 6/18 with a corresponding one grade or greater change in Lens Opacities Classification System II or history of having undergone cataract surgery with evidence of pseudophakia or aphakia at the 6-year follow-up. MAIN OUTCOME MEASURES: Six-year incidence of visually significant cataract and associated risk factors data were collected. RESULTS: Incident visually significant cataract at 6 years was seen in 158 subjects (6.36%, 95% CI: 5.40-7.32, phakics:pseudophakics/aphakics 70:88). Incidence was higher in the rural cohort as compared with the urban cohort (P < 0.001). Incidence increased with age and was highest in the ≥70 years age group (odds ratio (OR):31.23, 95% CI: 15.20-64.16, P < 0.001). Other associated risk factors included illiteracy (OR 1.75, 95% CI: 1.17-2.61, P = 0.007) and smoking (OR 1.77, 95% CI: 1.08-2.88, P = 0.02). CONCLUSIONS: A significant proportion of the population developed visually significant age-related cataract at 6 years. Incident visually significant cataract was significantly greater for the rural cohort between 50 and 69 years old.

Six-Year Incidence and Baseline Risk Factors for Pseudoexfoliation in a South Indian Population: The Chennai Eye Disease Incidence Study.

OBJECTIVE: To estimate the 6-year incidence of pseudoexfoliation and its risk factors in a South Indian population. DESIGN: Longitudinal population-based study. PARTICIPANTS: Subjects 40 years of age or older without pseudoexfoliation at baseline. METHODS: Participants were examined at baseline and after a 6-year interval. The presence of pseudoexfoliation was looked for after pupillary dilation in either or both eyes at 1 or more locations. Glaucoma was defined using the International Society of Geographical and Epidemiological Ophthalmology Classification. Logistic regression was performed to identify the baseline risk factors that could predict the incident pseudoexfoliation. MAIN OUTCOME MEASURES: Six-year incidence, associated risk factors, and rural-versus-urban differences. RESULTS: From the study cohort of 4228 subjects, 87 subjects (male-to-female ratio, 48:39; rural-to-urban ratio, 69:18) demonstrated incident pseudoexfoliation (2.03%; 95% confidence interval [CI], 1.6-2.5; rural: -2.86%; 95% CI, 1.6-2.5; urban: 0.96%; 95% CI, 0.5-1.4). Pseudoexfoliation was associated with glaucoma in 1 subject (1.1%), with primary angle-closure suspicion in 10 subjects (11.5%), and with ocular hypertension in 2 subjects (2.2%). Significant predictive baseline risk factors were older age (P < 0.001), rural residence (P < 0.001), illiteracy (P = 0.02), pseudophakia (P = 0.04), and nuclear cataract (P = 0.05). With reference to the 40-to-49-year age group, the risk of incidence increased from 4.7 (95% CI, 2.4-9.4) for the 50-to-59-year age group to 12.9 (95% CI, 6.1-27.2) for 70 years of age and older group. CONCLUSIONS: In 6 years, pseudoexfoliation developed in 2.03% of the population. Rural and urban incidence was significantly different.

Predictors for incidence of primary open-angle glaucoma in a South Indian population: the Chennai eye disease incidence study.

OBJECTIVE: To determine the 6-year incidence of primary open-angle glaucoma (POAG) and its associated predictors. DESIGN: Population-based cohort study. PARTICIPANTS: A total of 4316 subjects without POAG at baseline who were 40 years of age and older from a south Indian population. METHODS: Participants were examined at baseline and after a 6-year interval. Detailed ophthalmic examination included applanation tonometry, gonioscopy, pachymetry, optic disc evaluation, and automated perimetry. Glaucoma was defined using the International Society of Geographical and Epidemiological Ophthalmology Classification. Multivariable logistic regression was performed to identify the baseline risk factors that could predict the incident POAG. MAIN OUTCOME MEASURES: Six-year incidence of POAG and its associated risk factors. RESULTS: In 6 years, incident POAG developed in 129 subjects (2.9%; 95% confidence interval [CI], 2.4-3.4; male-to-female ratio, 65:64). Baseline age was a risk factor. In reference to the group 40 to 49 years of age, the incidence increased from 2.3 (95% CI, 1.4-3.7) for the group 50 to 59 years of age to 3.5 (95% CI, 2.2-5.7) for the group 60 to 69 years of age (P<0.001). Other baseline risk predictors were urban residence (odds ratio [OR], 1.6; 95% CI, 1.1-2.2; P = 0.01), higher intraocular pressure (IOP; OR, 2.0; 95% CI, 1.5-2.6 per 10 mmHg; P<0.001), myopia (OR, 1.7; 95%, CI, 1.1-2.5; P<0.001), and axial length (OR, 1.5; 95% CI, 1.0-2.2 per millimeter; P = 0.03). Thinner corneas with higher IOP at baseline had the highest incidence of POAG. In 80% of the urban population and 100% of the rural population, incident glaucoma was previously undetected. CONCLUSIONS: A significant proportion of this population demonstrated incident POAG. The baseline risk factors could help in identifying those at highest risk of disease.

Role Of Adaptive Optics In Early Diagnosis Of Glaucoma From A Clinician's Perspective.

BACKGROUND: Glaucoma is one of the leading causes of irreversible blindness across the world. Early detection is important to minimize the loss of visual function. The diagnostic tools, optical coherence tomography (OCT) and standard automated perimetry (SAP) form the keystones of the diagnosis and monitoring of the condition. However, the ability of these tools to diagnose early forms of glaucoma is limited. Adaptive optics (AO) is a technology that could help to overcome this limitation. AO technology can detect slightest changes occurring at the cellular level by compensating for ocular aberrations. METHODS: We searched PubMed for publications between 2002 and 2019 on adaptive optics in Ophthalmology. The key words were adaptive optics, lamina cribrosa, retinal nerve fiber layer defects, scanning laser ophthalmoscope and OCT. RESULTS: Out of 38 publications, 17 original articles or case series with relevance to glaucoma, and written in English were selected and reviewed. CONCLUSIONS: The AO technology, combined with various platforms such as fundus photography, scanning laser ophthalmoscopy and OCT, has been used in glaucoma patients to study the lamina cribrosa, retinal nerve fiber layer (RNFL), retinal photoreceptors as well as ocular circulation in minute detail. Imaging the subtle changes in morphology and reflectivity of RNFL at the preclinical stage may lead to early detection of glaucoma. Longitudinal monitoring of RNFL alterations in glaucoma patients is possible. At present, the technology is expensive with limited availability, and has several limitations.

Regional variation in the incidence of pseudo-exfoliation in the Andhra Pradesh Eye Disease Study (APEDS).

BACKGROUND: To report the 15-year incidence rate of pseudo-exfoliation (PXF),  PXF glaucoma and regional variation among rural participants in the Andhra Pradesh Eye Disease Study (APEDS) III. METHODS: This population-based longitudinal study was carried out at three rural study sites. Individuals of all ages who participated at baseline with a mean 15-year follow-up visit were included. Detailed Comprehensive ophthalmic examination was performed on all participants. The main outcome measure was development of PXF during the follow-up period in participants who were phakic in one or both eyes without PXF at baseline. RESULTS: Among 5395 participants, 5108 (94.6%) met the inclusion criteria. There were 93 (1.82%; 95% confidence interval (CI), 1.47-2.22) cases of incident PXF. Their median baseline age (1st, 3rd quartiles) was 51 (44, 59) years and the male: female ratio was 1.3:1. There was no case of incident PXF in participants aged <30 years at baseline. The incidence rate per 100 person years (95% CI) among all ages and those aged ≥30 years at baseline was 1.73 (1.64-1.82) and 3.73 (3.53-3.93), respectively. PXF material was located on iris as well as anterior surface of lens and it was often bilateral. Participants living in two study sites and increasing age were associated with the incidence of PXF. The 15-year incidence of PXF glaucoma (95% CI) in participants ≥30 years of age at baseline was 0.33% (0.14-0.66). CONCLUSION: There is significant regional variation in incidence of PXF in south India which warrants further investigation.

Incidence of primary open angle glaucoma in the Andhra Pradesh Eye Disease Study (APEDS).

BACKGROUND: To report 15-year incidence rate of primary open angle glaucoma (POAG) in the Andhra Pradesh Eye Disease Study (APEDS). METHODS: A population-based longitudinal study was carried out at three rural study sites. Phakic participants aged ≥40 years who participated at baseline (APEDS I) and the mean 15-year follow-up visit (APEDS III) were included. A comprehensive ophthalmic examination was performed on all participants. Mean intraocular pressure (IOP) was average of IOPs of right and left eyes. The definition of glaucoma was based on the International Society of Geographical and Epidemiological Ophthalmology (ISGEO) classification. The main outcome measure was incidence of POAG during the follow-up period in participants without glaucoma or suspicion of glaucoma at baseline. RESULTS: Data from the available and eligible participants from the original cohort (1241/2790; 44.4%) were analysed. The mean age (standard deviation) of participants at baseline was 50.2 (8.1) years; 580 (46.7%) were men. Thirty-six participants developed POAG [bilateral in 17 (47.2%)] over 15 years. The incidence rate of POAG per 100-person years (95% confidence interval) was 2.83 (2.6, 3.08). Compared to baseline, the reduction in mean IOP [median (range) mm Hg] was -0.75 (-7.5, 9) in participants with incident POAG and -2.5 (-14.5, 14.5) in those without. The inter-visit difference in mean IOP was a significant risk factor on logistic regression analysis. CONCLUSION: We report the long-term incidence of POAG in rural India. A longitudinal change in IOP, specifically a less pronounced reduction in IOP with increasing age, was a novel risk factor.

Outcomes of Descemet-Stripping Endothelial Keratoplasty in 52 Eyes With Iridocorneal Endothelial Syndrome.

PURPOSE: To evaluate the long-term outcomes of Descemet-stripping endothelial keratoplasty (DSEK) in 52 eyes with iridocorneal endothelial (ICE) syndrome. METHODS: Retrospective study of 52 eyes of 52 patients who were diagnosed with ICE syndrome and underwent DSEK between January 2010 and December 2019 with a follow-up of at least 6 months. RESULTS: The mean age was 48.8 ± 10.8 years. Female patients (n = 33) constituted 63.5%. The median duration of follow-up was 2.4 years (range, 0.5-9.1 yrs). The mean best-corrected visual acuity improved significantly after surgery and remained stable (∼20/50) through 5 years. The mean endothelial cell loss was 28%, 37.9%, 43.6%, and 56.9% at 6 months and at 1, 2, and 3 years, respectively. Graft rejection was noted in 5 eyes (9.6%). Postoperatively, increased intraocular pressure (IOP) was seen in 17 eyes (32.7%), and 10 eyes (19.2%) underwent glaucoma surgeries. Fourteen eyes (26.9%) had secondary graft failures. The estimates of graft success were 93.6% ± 3.6% at 1 year, 85.6% ± 5.5% at 2 years, 79.3% ± 6.7% at 3 years, 69.0% ± 8.9% at 4 years, and 59.1% ± 11.9% at 5 years. Postoperative increased IOP was found to be the only significant (P = 0.05) risk factor (hazard ratio 8.92) associated with graft failure. The clinical variant of ICE syndrome did not seem to influence the graft survival (P = 0.68). CONCLUSIONS: In this study, DSEK had a success rate of ∼60% at 5 years. Increased IOP post-DSEK is a significant risk factor for graft failure. Graft survival is not affected by the clinical variant of ICE syndrome.

Estimation of Goldmann applanation tonometer intraocular pressure (IOP) from scleral Schiotz IOP values in eyes with type-1 keratoprostheses.

PURPOSE: To validate estimation of Goldmann applanation tonometer (GAT) intraocular pressure (IOP) from scleral Schiotz IOP measurements using a regression model in normal eyes and eyes with type-1 keratoprostheses. METHODS: In this prospective cross-sectional study, cohort-1 had 253 normal anterior segment eyes, and cohort-2 had 100 eyes with type-1 keratoprostheses. Scleral Schiotz IOP measurements were used (in a non-linear model) to predict GAT IOP values for these eyes. Accuracy of predicted GAT IOP values was assessed using actual GAT IOP values for normal eyes, while for type-1 keratoprosthetic eyes, finger tension (FT) IOP assessments by an experienced glaucoma specialist were used. Primary outcome was agreement between FT IOP (assessed by an experienced glaucoma specialist) and predicted GAT IOP-derived clusters. RESULTS: The actual values of GAT IOP measurements in normal eyes (n=253; mean age ±SD, 51.35±15.56 years) ranged between 6 mm Hg and 62 mm Hg (mean=22±10.05 mm Hg). Estimated and actual GAT IOP values for normal eyes were very similar (mean difference=0.05 mm Hg with limits of agreement: -5.39 to 5.5 by Bland-Altman plot). Of the 100 eyes with type-1 keratoprostheses, 68 were classified as having digitally normal IOP, 28 as borderline and 4 as high. The agreement between classification by FT assessment and model-predicted GAT IOP values was substantial (Kappa=0.81, 95% CI 0.69 to 0.93). The accuracy of the model in assessing IOP was found to be 91% (95% CI 0.84 to 0.96). CONCLUSION: Scleral Schiotz IOP values along with our predictive model can be an alternative objective method to FT IOP in assessing IOP in eyes with type-1 keratoprostheses.

Adaptive optics scanning laser ophthalmoscopy may support early diagnosis of glaucoma.

Purpose: To compare image characteristics of retinal nerve fiber layer (RNFL) between glaucoma patients and healthy controls using adaptive optics scanning laser ophthalmoscopy (AOSLO). Methods: This was a cross-sectional pilot study with two groups: a glaucoma group with patients with moderate or severe glaucoma as per the Hodapp-Parrish-Anderson classification system and a control group with healthy individuals. The optic nerve damage in moderate glaucoma was predominantly located in only one hemisphere; the other hemisphere was un- or minimally affected on optical coherence tomography and automated perimetry and is referred to as early glaucoma. The structure of RNFL bundles and gain (%) in RNFL images with mean pixel values between 15 and 35 were analyzed. Imaging was performed one degree away from the optic disc margin at two and four cardinal clock positions in the glaucoma and control groups, respectively. The field of view was 1.3° at 2.3 µ resolution. We studied one eye per participant. Results: There were 11 glaucoma patients and 7 healthy controls. Imaging was successful at 88% of the locations in controls and early glaucoma; the reflectivity differed significantly (0.51 and 0.56, respectively, P < 0.001) but not the structure of RNFL bundles (Cohen's Kappa 0.11) between them. In patients with moderate and severe glaucoma, imaging was successful only at 46% of the locations; RNFL bundles were not discernible, and RNFL reflectivity did not differ from those with early glaucoma (P < 0.11). Conclusion: The recorded gain (%) of RNFL images obtained using AOSLO could be an objective indicator of early glaucoma.

Clinical and Specular microscopy characteristics and corelation in Iridocorneal endothelial syndrome without corneal edema.

PURPOSE: To investigate endothelial imaging patterns in ICE syndrome and correlate these with the observed clinical features in the affected eye. METHODS: Of the 70 patients of ICE syndrome referred from the glaucoma clinic between 2017 and 18, 17 patients had a clear cornea for reliable endothelial imaging were included in the study. RESULTS: Mean age was 47(range 29-63) years; 9 males and 8 females. The right eye was involved in 10 and left eye in 7 patients. Mean best corrected visual acuity was 20/30 (20/20-20/80) in the affected eye. All 17 patients had clear and compact central cornea and reasonably good vision at the time of specular microscopy. Those with best corrected visual acuity <20/20 had cataract as a co-morbidity. Endothelial abnormalities were noted in all patients and were documented using Hirst and modified Sherrard's classification system. As per the modified Sherrard's classification system, 9 eyes were categorised into total ICE, 5 eyes into subtotal ICE, in 3 eyes grading could not be applied. Of the 4 subtotal ICE, 1 was subtotal ICE (+) and 3 were subtotal ICE (-). 12/17 patients had glaucomatous disc. CONCLUSIONS: Specular microscopy provides information on the various morphological pattern of endothelial abnormalities and helps in mapping out the areas with abnormal/diseased endothelium. These have implications in the management of ICE syndrome.

Modifications to Combined Trabeculectomy and Manual Small Incision Cataract Surgery: Outcomes and Adaptability in Resource-constrained Areas.

PRECIS: We describe standardization and simplification of classic trabeculectomy combined with manual small incision cataract surgery (MSICS) to effectively manage the 2 leading and often coexisting causes of blindness and vision impairment in resource-constrained areas. PURPOSE: The purpose of this study was to describe modifications to trabeculectomy combined with MSICS and report on the outcomes of this technique. The modifications consist of standardization and simplification of the surgical steps. METHODS: Data obtained from adult patients who underwent described surgical technique at rural eye care centers across 3 Indian states between January 2018 and May 2019 were analyzed retrospectively. Complete success was intraocular pressure between 6 and 18 mm Hg without supplementary medication. Qualified success allowed up to 3 topical medication(s). Data are presented as median (first and third quartiles). RESULTS: We analyzed data of 70 eyes of 70 patients. Ophthalmology fellows performed 27 (38.5%) surgeries, whereas an experienced glaucoma specialist performed 43 (61.4%) surgeries. Patients were 63 (56, 67) years old. The preoperative intraocular pressure was 20 (16, 26) mm Hg on treatment with 3 (2, 3) antiglaucoma medications. Glaucoma was advanced by optic disc structural criteria in 58 (82.8%) eyes. Intraoperative mitomycin C was used in 5 (7.1%) eyes. Follow-up was 12.5 (6, 18) months. At 1 year, complete success (95% confidence interval) achieved was 55% (41-67), whereas qualified success was 83% (68-92) with 0 (0, 1) topical medications. The complete and qualified success rates did not differ between ophthalmology fellows and the glaucoma specialist (P=0.75 and 0.44, respectively). CONCLUSIONS: We present a straightforward, yet effective technique of combined cataract and glaucoma surgery. The technique has a potential for wider applicability, especially in the underserved regions of the world.

Agreement of Intraocular Pressure Measurement of Icare ic200 with Goldmann Applanation Tonometer in Adult Eyes with Normal Cornea.

PURPOSE: To study the agreement between the Icare ic200 (ICare Finland Oy, Helsinki, Finland) and the Goldmann Applanation Tonometer (GAT) in the measurement of intraocular pressure (IOP) in adult eyes. DESIGN: Noninterventional, cross-sectional study. PARTICIPANTS: A total of 156 eyes of 156 adult participants with clear corneas were included. METHODS: The IOP measurements were obtained with the Icare ic200 by 1 observer followed by GAT readings by a second masked observer. The central corneal thickness (CCT) and biometry of all subjects were recorded. MAIN OUTCOME MEASURES: The agreement between Icare ic200 and GAT was measured using the Bland-Altman plot. RESULTS: The mean age ± standard deviation of subjects was 55.3 ± 13.7 years. The GAT IOP ranged from 6 to 50 mmHg with a mean IOP of 19.5 ± 8.8 mmHg. The Icare ic200 IOP ranged from 7.4 to 50 mmHg with a mean IOP of 20.8 ± 9.3 mmHg. The mean difference between the IOP measurement of GAT and Icare ic200 was -1.27 mmHg with the 95% limits of agreement (LoA) ranging from -3.4 to 0.9 mmHg for all ranges of IOP. The mean difference (95% LoA) between the IOP measurement of GAT and Icare ic200 was -1 mmHg (-3 to 1 mmHg) and -1.8 mmHg (-4 to 0.2 mmHg) for a GAT IOP ≤21 mmHg and >21 mmHg, respectively. The CCT, axial length, age, and gender did not significantly affect the difference in measurement of IOP between the 2 tonometers. However, for every 1-mmHg increase in GAT IOP, the difference between the 2 tonometers increased by 0.04 mmHg (P < 0.001). CONCLUSIONS: In our study, the Icare ic200 overestimated the IOP. The overestimation increased as the baseline IOP increased. The agreement between the IOP measurement by GAT and Icare ic200 was <2 mmHg at all ranges of IOP. The narrow LoA between the tonometers for an IOP <21 mmHg makes it a useful alternative to GAT in this pressure range.

Agreement of Intraocular Pressure Measurement of Icare ic200 with Goldmann Applanation Tonometer in Adult Eyes with Normal Cornea.

PURPOSE: To study the agreement between the Icare ic200 (ICare Finland Oy, Helsinki, Finland) and the Goldmann Applanation Tonometer (GAT) in the measurement of intraocular pressure (IOP) in adult eyes. DESIGN: Noninterventional, cross-sectional study. PARTICIPANTS: A total of 156 eyes of 156 adult participants with clear corneas were included. METHODS: The IOP measurements were obtained with the Icare ic200 by 1 observer followed by GAT readings by a second masked observer. The central corneal thickness (CCT) and biometry of all subjects were recorded. MAIN OUTCOME MEASURES: The agreement between Icare ic200 and GAT was measured using the Bland-Altman plot. RESULTS: The mean age ± standard deviation of subjects was 55.3 ± 13.7 years. The GAT IOP ranged from 6 to 50 mmHg with a mean IOP of 19.5 ± 8.8 mmHg. The Icare ic200 IOP ranged from 7.4 to 50 mmHg with a mean IOP of 20.8 ± 9.3 mmHg. The mean difference between the IOP measurement of GAT and Icare ic200 was -1.27 mmHg with the 95% limits of agreement (LoA) ranging from -3.4 to 0.9 mmHg for all ranges of IOP. The mean difference (95% LoA) between the IOP measurement of GAT and Icare ic200 was -1 mmHg (-3 to 1 mmHg) and -1.8 mmHg (-4 to 0.2 mmHg) for a GAT IOP ≤21 mmHg and >21 mmHg, respectively. The CCT, axial length, age, and gender did not significantly affect the difference in measurement of IOP between the 2 tonometers. However, for every 1-mmHg increase in GAT IOP, the difference between the 2 tonometers increased by 0.04 mmHg (P < 0.001). CONCLUSIONS: In our study, the Icare ic200 overestimated the IOP. The overestimation increased as the baseline IOP increased. The agreement between the IOP measurement by GAT and Icare ic200 was <2 mmHg at all ranges of IOP. The narrow LoA between the tonometers for an IOP <21 mmHg makes it a useful alternative to GAT in this pressure range.

Conversion of Flow-restrictive Ahmed Glaucoma Valve to a Nonrestrictive Drainage Implant by Slicing the Valve Leaflets: An In Vitro Study.

PRECIS: With a newly designed blade, slicing of the Ahmed glaucoma valve (AGV) leaflets helped to convert the flow-restrictive AGV into a non-flow-restrictive device. Flow characteristics by our in-vitro study confirmed the loss of resistance of AGV valve leaflets. PURPOSE: To describe a new blade to destroy the valve leaflets of AGV and to report the in-vitro flow characteristics of AGV after valve destruction. METHODS: All the newly opened AGV implants and the Aurolab aqueous drainage implants (AADI, used as controls) were tested by connecting to a 27-G cannula, open manometer, digital manometer, and automated infusion pump. Data logging was done using a digital manometer at 4 Hz using computerized software. When the AGV's flow characterization reached the steady phase, their valve functionality was destroyed by disrupting the valve leaflets, using a specially designed blade. The flow characteristics after valve slicing were compared with that of AADI. RESULTS: A total of 5 FP7 AGVs and 2 AADIs were tested. After initial resistance to flow (5, 8 mm Hg) observed in the case of AADI for 1 to 3 hours, it dropped to 1 mm Hg in both the implants. The flow-restrictive AGV showed 3 distinct phases in the flow characterization. The first phase included the transient phase followed by the steady phase wherein the pressure was 11.2±2.6 (min 7, max 14) mm Hg. The pressure resistance of the AGV dropped significantly (P<0.001) to a mean of 0.4±0.54 mm Hg (1 mm Hg in 2 devices and 0 mm Hg in 3 devices) after the valve functionality was destroyed. The average time taken for this drop in pressure resistance after valve slicing was 10.2±3.0 minutes (min 7, max 15). CONCLUSIONS: It was possible to convert the flow-restrictive AGV into a non-flow-restrictive device by destroying the functionality of the valve leaflets. The pressure of the AGVs was similar to AADI after destroying its valve functionality.

Fifteen-Year Incidence Rate of Primary Angle Closure Disease in the Andhra Pradesh Eye Disease Study.

PURPOSE: To report on the 15-year incidence of primary angle closure disease (PACD) among participants aged ≥40 years in rural southern India DESIGN: Population-based longitudinal incidence rate study METHODS: Setting: 3 rural study centres. STUDY POPULATION: Phakic participants aged ≥40 years who participated in both examination time points. OBSERVATION PROCEDURES: All participants at the baseline and at the mean 15-year follow-up visit underwent a detailed interview, anthropometry, blood pressure measurement, and comprehensive eye examination. Automated perimetry was attempted based on predefined criteria. Main outcome measures included development of any form of PACD, as defined by the International Society for Geographical and Epidemiological Ophthalmology (ISGEO), during the follow-up period in phakic participants, who did not have the disease at baseline. RESULTS: We analyzed data obtained from 1,197 (81.4% out of available 1,470) participants to calculate the incidence of the disease. The mean age (standard deviation) of the study participants at the baseline was 50.2 (8.1) years, with 670 male (45.5%) and 800 female (54.4%) participants. The incidence rate per 100 person-years (95% confidence interval) for primary angle closure suspect, primary angle closure, and primary angle closure glaucoma was 8.8 (8.4, 9.2), 6.2 (5.9, 6.6), and 1.6 (1.4, 1.8), respectively. Thus, the incidence of all forms of PACD was 16.4 (15.9, 17) per 100 person-years. On logistic regression analysis, female gender was a significant risk factor whereas presence of myopia was protective. CONCLUSIONS: This study reports long-term incidence of PACD from rural India. It has implications for eye health care policies, strategies, and planning.

LVPEI Glaucoma Epidemiology and Molecular Genetic Study: teleophthalmology screening for angle-closure disease in an underserved region.

OBJECTIVES: To assess the ability of teleophthalmoscopic grading of peripheral anterior chamber depth (PACD) using the van Herick (vH) technique in detecting gonioscopically occludable angle; and to determine whether combining results from vH grading and ocular biometry can improve the accuracy to diagnose gonioscopically occludable angle METHODS: This cross-sectional study was an offshoot of a rural population-based study, Glaucoma Epidemiology and Molecular Genetic Study (GLEAMS). A masked urban ophthalmologist graded digital slit lamp photographs of PACD by vH technique. Sussman four-mirror lens was used to perform dark room indentation gonioscopy. Cutoff values of the tests were, vH technique: grade ≤ 2, central anterior chamber depth (ACD), as well as axial length: ≤ 25th percentile and lens thickness ≥ 75th percentile value of the study population. RESULTS: We studied 1965 eyes of 1029 adult participants. The vH grade was ≤2 in 188 (9.5%) eyes. The angle was occludable by gonioscopy in 101 (5.1%) eyes. The performance of the vH test to rule out gonioscopically occludable angle was good [negative predictive value (NPV): 97.3%], despite low sensitivity (52.5%), while its efficacy to rule in the condition was low [positive predictive value (PPV): 28.2%] despite high specificity (92.8%). However, test combination strategy increased the PPV nearly twofold (53.8%). The calculated PPV at 10% prevalence of gonioscopically occludable angle was even higher (70.5%). CONCLUSIONS: Van Herick technique can be incorporated into a teleophthalmology program by means of slit lamp photographs of PACD. Combined vH grading and ocular biometry improved the predictability of a gonioscopically occludable angle.

Measurement of Goldmann applanation tonometer calibration error.

OBJECTIVE: To determine the frequency and possible origins of calibration errors of the Goldmann applanation tonometer and to investigate intraobserver and interobserver agreement in the measurement of such calibration errors. DESIGN: Evaluation of diagnostic test or technology. PARTICIPANTS: One hundred thirty-two slit-lamp-mounted Haag-Streit Goldmann tonometers (Model AT 900 C/M; Haag-Streit, Bern, Switzerland). METHODS: Calibration error testing was performed using the standard calibration error check weight bar. A single observer tested 25 instruments on 2 consecutive days. Two observers independently measured calibration errors of another 40 instruments. A single observer performed prospective testing of the remaining Haag-Streit Goldmann tonometers, 6 months after their annual calibration by the bioengineering department of the hospital. Four months later, the same observer retested the instruments that were found to be faulty earlier. MAIN OUTCOME MEASURE: Goldmann applanation tonometer calibration error. RESULTS: Only 4% of Goldmann tonometers were found to be within the manufacturer's recommended calibration error tolerance (+/-0.5 mmHg) at 20 mmHg. Twenty-eight percent of instruments had calibration errors of more than +/-2 mmHg at the 20-mmHg testing level. An additional 12.12% had calibration errors of more than +/-2 mmHg at the 0- or 60-mmHg testing levels, or both. Four months after the initial testing and repair of the 53 faulty instruments, 20.75% again were found to have calibration errors of more than +/-2 mmHg at any one or more testing level(s). Intraclass correlation coefficients for intraobserver agreement at 20 mmHg were 0.57 (95% confidence interval [CI], 0.25-0.78) for positive error, 0.82 (95% CI, 0.65-0.92) for negative error, and for interobserver agreement at 20 mmHg, 0.83 (95% CI, 0.70-0.90) for positive error and 0.83 (95% CI, 0.70-0.90) for negative error. CONCLUSIONS: The authors found good agreement in measurement of Goldmann applanation tonometer calibration error. A significant number of instruments had clinically unacceptable calibration errors. A more frequent calibration error testing and automation of calibration error check is desirable. FINANCIAL DISCLOSURE(S): The authors have no proprietary or commercial interest in any materials discussed in this article.