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.

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.

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.

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.

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 m 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.

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.

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.

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.

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.

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.

New superior modified fornix-based twin-site phacotrabeculectomy

Phacotrabeculectomy is the preferred surgical management of coexisting visually significant cataract and moderate to advanced glaucoma. We report the surgical technique of a new modified fornix-based separate-site phacotrabeculectomy, with mitomycin C (MMC) application, in both primary open angle and angle closure glaucoma. In this new separate-site technique, both phaco and filtration are accommodated superiorly, side by side, hence called twin-site. This was achieved in an efficacious and safe manner with sparing of limbal stem cells without compromising safety. It is not only MMC-compatible but also has a low incidence of wound leak. The technique has no adverse consequence on the survival of the bleb, and we achieved complete success in 79.2% and total success in 93.1% in 130 eyes of 117 patients, in the intermediate term. Furthermore, the time taken for this separate-site surgical technique is comparable to published one-site procedures.

Combination of Simple Diagnostic Tests to Detect Primary Angle Closure Disease in a Resource-constrained Region

Purpose: To report on diagnostic accuracy of van Herick (vH) technique performed by a vision technician (VT) as well as on efficacy of a combination of vH technique and central anterior chamber depth (ACD) in detection of primary angle closure disease.Methods: Data was obtained from two cohorts; rural clinic setting (n = 111), and rural population-based research setting (n = 888). Van Herick grading was performed by a VT in first cohort and a glaucoma specialist in second cohort. A reference standard four-mirror gonioscopy was performed by a glaucoma specialist in both cohorts. We did preferential sampling. Cut-off levels for vH technique and central ACD were grade 2 and 25^th percentile value, respectively. Data from one eye per participant was analyzed.Results: Three hundred and forty (34%) eyes were gonioscopically occludable. Area under receiver operating characteristic curve (95% confidence interval) for vH test was 0.83 (0.76, 0.9) and 0.81 (0.78, 0.84) in first and second cohorts, respectively. Simultaneous testing achieved sensitivity of 87.8% while sequential testing achieved specificity of 99.3%. Negative predictive value* of simultaneous testing was 98.3% compared to 96.6% of vH technique while positive predictive value* of sequential testing was 86% compared to 49.3% of vH technique. (*at 10% prevalence of gonioscopically occludable angle)Conclusions: Diagnostic accuracy of vH grading was similar when performed by a VT and a glaucoma specialist. While test combination was effective to rule in, vH technique may suffice to rule out the disease. Implications of these findings for resource-constrained regions are discussed.

Diagnostic Accuracy of Van Herick Technique to Detect Pre-Disease States of Primary Angle Closure Glaucoma in a Resource Constraint Region

OBJECTIVES

To critically evaluate diagnostic accuracy of the van Herick (vH) technique in detection of gonioscopically occludable angle in a rural population and to explore ways to improve accuracy of the technique Methods: The study cohort was formed by two-stage cluster random sampling. Peripheral anterior chamber depth grading was performed, using both traditional and modified (photographic comparison) vH techniques, under dark adapted and standard lighting conditions by a comprehensive ophthalmologist masked to the clinical features. The cut-off criterion for vH test was 25% of peripheral corneal thickness. The reference standard was dark room 4-mirror indentation gonioscopy performed by an experienced glaucoma specialist. This study adhered to the STARD guidelines for reporting diagnostic accuracy studies.

RESULTS

We studied 111 eyes of 111 participants. The median age was 62 years. The angle was occludable by gonioscopy in 69 (62%) eyes; 58 eyes were primary angle closure suspects and 11 were primary angle closure patients. The likelihood ratio (95% confidence interval (CI)) of the positive (LR+) and negative (LR‒) result by the traditional vH technique was 5.17 (2.43, 11) and 0.30 (0.20, 0.46), respectively. The LR+ by reducing and LR‒ by elevating the cut-off grade of the traditional vH technique were 9.4 (2.3, 37.4) and 0.08 (0.02, 0.31), respectively. The area under receiver operating characteristic curve did not differ significantly by photographic comparison or lighting condition (p = 0.13).

CONCLUSIONS

vH grading can be considered as a triage test before gonioscopy. The value of the vH technique to the diagnostic strategy is discussed.

Is Ahmed Glaucoma Valve Consistent in Performance?

Purpose

To investigate the mechanism of action and consistency in flow characteristics of the Ahmed glaucoma valve (AGV) under simulated physiological conditions in-vitro and to evaluate whether resistance during priming has any effect on performance of the device.

Methods

Each newly opened AGV device was connected to a digital manometer and was primed with normal saline. The device was then placed in a saline bath and connected to an open manometer, a digital manometer, and an infusion pump. Saline was infused at a rate of 3 μL/min for 24 hours. Digital manometer readings were recorded at 4 Hz.

Results

Data obtained from 9 devices are presented as medians (ranges). The priming pressure was 1130 (835, 1625) mm Hg. Pressure versus time curves showed two distinct phases; transient and steady phases. The transient phase peak pressure was 24 (13, 45) mm Hg. In the steady phase, opening and closing pressures were 13 (10, 17) and 7 (4, 9) mm Hg, respectively; the valve leaflets briefly opened every 73.9 (51, 76.6) minutes and the fluctuation of pressure (difference between opening and closing pressures) was 6 (3, 9) mm Hg. The Spearman correlation coefficient between priming and opening and priming and closing pressure was ρ = −0.13 (P = 0.72) and ρ = −0.36 (P = 0.33), respectively.

Conclusions

The device showed functionality like a valve. The resistance during priming did not affect opening and closing pressures of the AGV. This study showed variable in vitro performance of the AGV.

Translational Relevance

These laboratory findings might, at least partly, explain the variability in the clinical outcome of the device.

Understanding practice patterns of glaucoma sub-specialists in India

AIM

To obtain information on the prevailing practice patterns of glaucoma specialists in India.

METHODS

Glaucoma specialists attending the Annual Conference of the Glaucoma Society of India (GSI) were surveyed. This survey, conducted in 2013, was based on an interactive audience response system.

RESULTS

The information was obtained from 146 glaucoma specialists. Approximately half (n=83; 57%) had ≥10y of experience in managing glaucoma and were in institutional practice (n=74, 51%). Goldmann applanation tonometry was preferred by 103 (72%) specialists whilst n=25 (17.4%) used non-contact tonometer. Indentation gonioscopy was favoured by two-thirds (n=90, 66%) whereas stereoscopic optic disc examination and visual fields using Humphrey perimeter was performed by a majority of the specialists surveyed (n=115, 86% and n=114; 83% respectively). Nearly three quarter specialists (n=96; 72%) preferred optical coherence tomography for imaging. The primary choice for treatment of angle closure disease and primary open angle glaucoma was laser (iridotomy, n=117; 93%) and medical management (prostaglandin analogue, n=104; 78%), respectively. Approximately only a third of the specialists surveyed (n=37; 28%) were performing both trabeculectomy and implantation of a glaucoma drainage device and about half (n=64; 47%) were not operating on congenital glaucoma at all.

CONCLUSION

This survey has found conformance with preferred practice patterns in several areas of diagnosis and management of glaucoma, but there was diversity in a few areas. The information is a significant step towards improvement of glaucoma care in India, including planning for future strategies.

Glaucoma associated with iridocorneal endothelial syndrome in 203 Indian subjects

Purpose

To report the demographic profile, clinical features, and prevalence of glaucoma and its management in patients with Iridocorneal endothelial (ICE) syndrome.

Methods

Retrospective review of 203 consecutive subjects with ICE syndrome at a tertiary eye care centre between January 1988 and June 2013.

Results

ICE syndrome was present in 223 eyes of 203 subjects, 124 (61%) were female and 79 (39%) were male. The median age at presentation was 43 years (1^st (Q₁) and 3^rd (Q₃) quartile; 34, 51 years). ICE syndrome was unilateral in 183 (90%) subjects, and bilateral in 20 (10%) subjects. The most common clinical variant was progressive iris atrophy (PIA, 115; 52% eyes), followed by Chandler syndrome (CS, 87; 39% eyes) and Cogan-Reese syndrome (CRS, 21; 9% eyes). Glaucoma was found in 156 eyes (70%) at presentation and the median (Q₁, Q₃) intraocular pressure in eyes with glaucoma was 24 (16, 38) mm Hg. Seven eyes developed glaucoma during the follow-up period, increasing the percentage of eyes with glaucoma to 73%. Intraocular pressure was managed medically in 81 eyes (50%) and the other 82 eyes (50%) required surgical intervention. Corneal edema was present in 124 eyes (56%) of which, 32 eyes (14%) required keratoplasty.

Conclusions

In our study on ICE syndrome in Indian population, the presentation was predominantly uniocular and more common in middle aged women. Progressive iris atrophy was the most common clinical variant. ICE syndrome was associated with glaucoma in over 70% of the eyes and half of the eyes had corneal edema.

Surgical management of malignant glaucoma: a retrospective analysis of fifty eight eyes

PurposeTo assess outcomes of surgical management of malignant glaucoma in terms of re-formation of anterior chamberMethodsThis was a retrospective analysis of consecutive patients who underwent surgical treatment for malignant glaucoma between January 1995 and December 2013 at a tertiary care ophthalmic institute, with a minimum follow up of 2 months.ResultsFifty eight eyes of 58 patients were included. Fifty two (89.7%) patients had primary angle closure glaucoma. The majority had undergone glaucoma filtration surgery earlier (n=53, 91.4%). Lensectomy and anterior vitrectomy was performed in 15 (25.9%) eyes (Group 1). Vitrectomy and anterior chamber re-formation was performed in 27 (46.6%) eyes (Group 2). Vitrectomy-phacoemulsification-vitrectomy was performed in 16 (27.6%) eyes (Group 3). Communication between the two segments of eye through anterior hyaloid, lens capsule complex and/or iris was achieved in all groups. The median follow-up (Inter-quartile range) was 30 (71.5) months. Anterior chamber re-formation was achieved in 56 (96.5%) eyes at final visit. The improvement in mean±SD LogMAR visual acuity (1.1±1 to 0.7±0.8) and reduction in number ±SD of anti-glaucoma medications (2.1±1.1 to 1±1.6) between onset and final visit were significant (P=0.02 and <0.01, respectively). The intraocular pressure (mm Hg) at onset and at final visit was 30.7±17.4 and 14±6.2, 32.8±12.6 and 15.3±7.4, and 27.2±14 and 10.9±3 in groups 1-3, respectively (all P<0.01).ConclusionOur anatomical success rate was high. The key element in achieving this outcome was the establishment of a patent communication between the vitreous cavity and the anterior chamber.

Correction: Etiology and Management of Raised Intraocular Pressure following Posterior Chamber Phakic Intraocular Lens Implantation in Myopic Eyes

[This corrects the article DOI: 10.1371/journal.pone.0165469.].

Etiology and Management of Raised Intraocular Pressure following Posterior Chamber Phakic Intraocular Lens Implantation in Myopic Eyes

AIM

To evaluate the etiology and management of elevated intraocular pressure (IOP) following posterior chamber phakic implantable collamer lens (ICL) surgery.

METHODS

Between 2009 and 2015, 638 eyes of 359 subjects with refractive myopia, underwent V4b and V4c (CentraFLOW) model ICL implantation. Ocular hypertension (OHT) was defined as IOP of ≥ 22 mm Hg on two separate occasions and elevated IOP with corresponding optic disc or visual field damage was defined as glaucoma.

RESULTS

Elevated IOP ≥ 22 mm Hg was noted in 33 eyes of 30 subjects (33/638; 5.17%). Median age of subjects with raised IOP was 26 years (Inter quartile range (IQR):22, 29) and median refarctive error was -16 diopters (-19.5, -13). The median follow up was 7.8 months (IQR:0.3, 17.6) and median time for postoperative IOP rise was 12 days, (IQR:2, 24). The various etiologies for elevated IOP were steroid response in 21 eyes (64%; 10 eyes with V4b, 11 eyes with V4c), retained viscoelastic in 5 eyes (15%) (3 with V4b, 2 with V4c), pupillary block in four eyes (12%; 3 with V4b, 1 with V4c), malignant glaucoma in one eye (3%, V4b), and missed pre-existing Juvenile open angle glaucoma (JOAG) in two eyes (6% with V4b). Elevated IOP in 31 eyes resolved with conservative management. One eye (centraFLOW design) with central aquaport block by viscoelastic, needed AC wash and one eye with malignant glaucoma needed parsplana vitrectomy and hyaloidotomy. Ten eyes required longterm (>2 months) antiglaucoma medications (AGM) for IOP control. Except the two eyes with JOAG, none had disc and field damage.

CONCLUSION

In our series, OHT was seen in 4.85% and glaucoma in 0.3% eyes that underwent V4b and V4c model ICL implantation. Multiple etiologies were noted and steroid induced ocular hypertension was the most common cause of elevated IOP followed by retained viscoelastic and pupillary block. One third of these eyes required longterm AGM for IOP control.

Diurnal intraocular pressure fluctuation and its risk factors in angle-closure and open-angle glaucoma

PURPOSE

To evaluate intraocular pressure (IOP) fluctuation during office hours and its predictive factors in untreated primary angle-closure suspects (PACS); post-iridotomy primary angle closure (PAC) and primary angle-closure glaucoma (PACG) eyes with or without IOP-lowering medication(s) as appropriate and medically treated primary open-angle glaucoma (POAG) eyes.

METHODS

One-hundred seventeen eyes (29 PACS, 30 PAC, 28 PACG, and 30 POAG) of 117 patients were included in this cross-sectional study. The subjects underwent hourly IOP measurements with Goldmann tonometer from 0800 to 1700 hours. Subjects with PAC and PACG had laser peripheral iridotomy at least 2 weeks prior to the inclusion. SD of office-hour IOP readings was the main outcome measure.

RESULTS

IOP fluctuation differed between the groups (P=0.01; Kruskal-Wallis Test). Post hoc Mann-Whitney U-tests showed significantly less IOP fluctuation in PACS compared with PACG (P<0.01). Peak office-hour IOP was observed in the morning in untreated subjects and in the early afternoon in treated subjects. A stepwise linear regression model identified the presence of peripheral anterior synechiae (PAS), thickness of lens, large vertical cup-to-disc ratio (VCDR), and PAC category as significant predictive factors associated with office-hour IOP fluctuation.

CONCLUSIONS

Diurnal IOP fluctuation in asymptomatic PACSs was less than that in treated PACG subjects and was at least comparable to that in treated PAC and POAG subjects. The greater the amount of PAS, the thicker the lens, the larger the VCDR, the greater was the IOP fluctuation during office hours.

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.

The ISNT rule in glaucoma: revisiting with spectral domain optical coherence tomography

PURPOSE

To evaluate the ability of the neuroretinal rim (NRR) rules determined using spectral domain optical coherence tomography (SDOCT) in diagnosing glaucoma and to study the effect of optic disc size and disease severity on the diagnostic ability of these rules.

METHODS

In a cross-sectional study, 125 eyes of 96 glaucoma patients and 96 eyes of 72 control subjects underwent optic nerve head (ONH) imaging with SDOCT. Inferior (I), superior (S), nasal (N) and temporal (T) NRR areas were automatically determined by the sdoct software. Diagnostic abilities of ISNT (I > S > N > T), IT (I > T) and ST (S > T) rules in glaucoma were evaluated using sensitivity, specificity and likelihood ratios (LR). Effect of optic disc size and disease severity [based on mean deviation (MD) on visual fields] on the diagnostic ability of the NRR rules was evaluated using regression models.

RESULTS

Sensitivities of ISNT, IT and ST rules were 80.8%, 60.0% and 29.6%, respectively, and the specificities were 32.3%, 84.4% and 93.8%, respectively. Positive LRs of ISNT, IT and ST rules were 1.19, 3.84 and 4.74, respectively, and negative LRs were 0.60, 0.47 and 0.75, respectively. Sensitivities of ISNT (coefficient: -1.06, p = 0.02) and IT (-0.71, 0.05) rules decreased with increasing disc size. Positive LR of IT rule increased significantly (-0.01, 0.04) with decreasing MD, and negative LR of IT rule decreased (got better) significantly (0.26, 0.05) with decreasing disc size.

CONCLUSIONS

Neuroretinal rim rules, as determined by SDOCT, do not allow robust differentiation of glaucomatous from non-glaucomatous discs.

Fibrin sealant-assisted revision of the exposed Ahmed tube

Tube exposure is a known complication of Ahmed glaucoma valve (AGV) implantation. Repair of the exposed tube is not easy. A 42-year-old monocular aphakic male had undergone retinal detachment repair with placement of an episcleral-encircling band followed by implantation of AGV. He presented to the clinic on routine review with exposure of the shunt tube. The complication was managed by placing scleral and conjunctival grafts over the exposed tube using a fibrin adhesive (Tisseel kit; Baxter AG, Vienna, Austria). The novel use of the fibrin sealant in the repair of AGV tube exposure was for better graft-integration.

Role of visual field reliability indices in ruling out glaucoma

IMPORTANCE

Standard automated perimetry is the current criterion standard for assessment of visual field (VF) loss in glaucoma. The 3 commonly used reliability indices to judge the quality of standard automated perimetry results are fixation losses (FLs) and false-positive (FP) and false-negative (FN) response rates. However, the influence of reliability indices, when within the manufacturer-recommended limits, on VF classification has been sparsely studied.

OBJECTIVE

To evaluate the role of VF reliability indices in ruling out glaucoma.

DESIGN, SETTING, AND PARTICIPANTS

A cross-sectional study of 291 eyes of 291 participants referred to a tertiary eye care facility by general ophthalmologists. The participants were suspected to have glaucoma based on optic disc appearance, but the eyes were judged to be normal with physiological cupping by glaucoma experts on masked evaluation of optic disc photographs. All participants underwent VF testing with the Swedish interactive threshold algorithm standard 24-2 program.

MAIN OUTCOMES AND MEASURES

Logistic regression models were used to evaluate the associations between reliability indices and FP classifications on VF testing (glaucoma hemifield test as outside normal limits and pattern standard deviation with P < .05).

RESULTS

Median FL, FP, and FN response rates were 7%, 1%, and 2%, respectively. Among the 241 participants with reliable VF results (FL <20% and FP response rate <15%), the VF classification was normal in 188 (78.0%) and glaucoma (FP) in 53 (22.0%). Probability of FP VF classification was associated with FN response rates (odds ratio [OR], 1.36; 95% CI, 1.25-1.48, P < .001) but did not appear to be associated with FLs (OR, 0.96; 95% CI, 0.90-1.03, P = .30) or FP response rates (OR, 0.96; 95% CI, 0.83-1.12, P = .64). Predicted probability of FP VF classification was 9% (95% CI, 6%-14%), 40% (32%-49%), and 82% (68%-91%) at FN response rates of 0%, 8%, and 16%, respectively.

CONCLUSIONS AND RELEVANCE

This study suggests that FN response rates have an effect on the ability of automated VF assessments to rule out glaucoma. Since FN response rates are ignored by the manufacturer while flagging a test as unreliable, clinicians and researchers may benefit by realizing that FN response rates can lead to FP VF classification, even when their frequencies are small.

Atypical birefringence pattern and the diagnostic ability of scanning laser polarimetry with enhanced corneal compensation in glaucoma

PURPOSE

To evaluate the effect of typical scan score (TSS), when within the acceptable limits, on the diagnostic performance of retinal nerve fibre layer (RNFL) parameters with the enhanced corneal compensation (ECC) protocol of scanning laser polarimetry (SLP) in glaucoma.

METHODS

In a cross-sectional study, 203 eyes of 160 glaucoma patients and 140 eyes of 104 control subjects underwent RNFL imaging with the ECC protocol of SLP. TSS was used to quantify atypical birefringence pattern (ABP) images. Influence of TSS on the diagnostic ability of SLP parameters was evaluated by receiver operating characteristic (ROC) regression models after adjusting for the effect of disease severity [based on mean deviation (MD)] on standard automated perimetry).

RESULTS

Diagnostic abilities of all RNFL parameters of SLP increased when the TSS values were higher. This effect was statistically significant for TSNIT (coefficient: 0.08, p<0.001) and inferior average parameters (coefficient: 0.06, p=0.002) but not for nerve fibre indicator (NFI, coefficient: 0.03, p=0.21). In early glaucoma (MD of -5 dB), predicted area under ROC curve (AUC) for TSNIT average parameter improved from 0.642 at a TSS of 90 to 0.845 at a TSS of 100. In advanced glaucoma (MD of -15 dB), AUC for TSNIT average improved from 0.832 at a TSS of 90 to 0.947 at 100.

CONCLUSION

Diagnostic performances of TSNIT and inferior average RNFL parameters with ECC protocol of SLP were significantly influenced by TSS even when the TSS values were within the acceptable limits. Diagnostic ability of NFI was unaffected by TSS values.

Rectifying calibration error of Goldmann applanation tonometer is easy!

Purpose:

Goldmann applanation tonometer (GAT) is the current Gold standard tonometer. However, its calibration error is common and can go unnoticed in clinics. Its company repair has limitations. The purpose of this report is to describe a self-taught technique of rectifying calibration error of GAT.

Materials and Methods:

Twenty-nine slit-lamp-mounted Haag-Streit Goldmann tonometers (Model AT 900 C/M; Haag-Streit, Switzerland) were included in this cross-sectional interventional pilot study. The technique of rectification of calibration error of the tonometer involved cleaning and lubrication of the instrument followed by alignment of weights when lubrication alone didn’t suffice. We followed the South East Asia Glaucoma Interest Group's definition of calibration error tolerance (acceptable GAT calibration error within ±2, ±3 and ±4 mm Hg at the 0, 20 and 60-mm Hg testing levels, respectively).

Results:

Twelve out of 29 (41.3%) GATs were out of calibration. The range of positive and negative calibration error at the clinically most important 20-mm Hg testing level was 0.5 to 20 mm Hg and -0.5 to -18 mm Hg, respectively. Cleaning and lubrication alone sufficed to rectify calibration error of 11 (91.6%) faulty instruments. Only one (8.3%) faulty GAT required alignment of the counter-weight.

Conclusions:

Rectification of calibration error of GAT is possible in-house. Cleaning and lubrication of GAT can be carried out even by eye care professionals and may suffice to rectify calibration error in the majority of faulty instruments. Such an exercise may drastically reduce the downtime of the Gold standard tonometer.

Six-year incidence of ocular hypertension in a South Indian population: the Chennai eye disease incidence study

AIMS

To report the 6-year incidence and risk factors for ocular hypertension (OHT) in a population-based study in southern India.

METHODS

6 years after baseline evaluation, 56.9% subjects (participants:non-participants, 4421:3353) were re-examined at the base hospital. Incident OHT was defined as an intraocular pressure above the 97.5th centile for the population with no evidence of glaucoma in the 2852 phakic subjects, 40 years or older. Subjects with trauma, laser or incisional surgery at baseline or follow-up were excluded (total exclusions: 1569).

RESULTS

Incidence of OHT at 6 years was 62/2852 subjects (2.17% (95% CI 1.64% to 2.71%, men:women, 36:26)). Incidence was higher in the rural cohort as compared with the urban cohort (80.6% vs 19.4%, p<0.001). A higher baseline intraocular pressure (with increasing OR: 16-18 mm Hg (OR 4.0, 95% CI 2.1 to 7.9), 19-21 mm Hg (OR 11.4, 95% CI 5.7 to 22.9), 22-24 mm Hg (OR 42.6, 95% CI 11.0 to 164.8, in the urban cohort)) and increasing age (50-59 years (OR 1.9, 95% CI 1.1 to 3.3), 70 years and above (OR 3.6, 95% CI 1.2 to 10.6)) were significantly associated risk factors for incident OHT.

CONCLUSIONS

A significant proportion of this normal population converted to OHT. A higher incidence of conversion was seen in the rural population.

Peripapillary retinal nerve fiber layer assessment of spectral domain optical coherence tomography and scanning laser polarimetry to diagnose preperimetric glaucoma

Purpose

To compare the abilities of peripapillary retinal nerve fiber layer (RNFL) parameters of spectral domain optical coherence tomograph (SDOCT) and scanning laser polarimeter (GDx enhanced corneal compensation; ECC) in detecting preperimetric glaucoma.

Methods

In a cross-sectional study, 35 preperimetric glaucoma eyes (32 subjects) and 94 control eyes (74 subjects) underwent digital optic disc photography and RNFL imaging with SDOCT and GDx ECC. Ability of RNFL parameters of SDOCT and GDx ECC to discriminate preperimetric glaucoma eyes from control eyes was compared using area under receiver operating characteristic curves (AUC), sensitivities at fixed specificities and likelihood ratios (LR).

Results

AUC of the global average RNFL thickness of SDOCT (0.786) was significantly greater (p<0.001) than that of GDx ECC (0.627). Sensitivities at 95% specificity of the corresponding parameters were 20% and 8.6% respectively. AUCs of the inferior, superior and temporal quadrant RNFL thickness parameters of SDOCT were also significantly (p<0.05) greater than the respective RNFL parameters of GDx ECC. LRs of outside normal limits category of SDOCT parameters ranged between 3.3 and 4.0 while the same of GDx ECC parameters ranged between 1.2 and 2.1. LRs of within normal limits category of SDOCT parameters ranged between 0.4 and 0.7 while the same of GDx ECC parameters ranged between 0.7 and 1.0.

Conclusions

Abilities of the RNFL parameters of SDOCT and GDx ECC to diagnose preperimetric glaucoma were only moderate. Diagnostic abilities of the RNFL parameters of SDOCT were significantly better than that of GDx ECC in preperimetric glaucoma.

Scanning the macula for detecting glaucoma

Background:

With the advent of spectral domain optical coherence tomography (SDOCT), there has been a renewed interest in macular region for detection of glaucoma. However, most macular SDOCT parameters currently are thickness parameters which evaluate thinning of the macular layers but do not quantify the extent of area over which the thinning has occurred. We therefore calculated a new macular parameter, ganglion cell complex surface abnormality ratio (GCC SAR) that represented the surface area over which the macular thickness was decreased.

Purpose:

To evaluate the ability of SAR in detecting perimetric and preperimetric glaucoma.

Design:

Retrospective image analysis.

Materials and Methods:

68 eyes with perimetric glaucoma, 62 eyes with preperimetric glaucoma and 165 control eyes underwent GCC imaging with SDOCT. SAR was calculated as the ratio of the abnormal to total area on the GCC significance map.

Statistical Analysis:

Diagnostic ability of SAR in glaucoma was compared against that of the standard parameters generated by the SDOCT software using area under receiver operating characteristic curves (AUC) and sensitivities at fixed specificities.

Results:

AUC of SAR (0.91) was statistically significantly better than that of GCC average thickness (0.86, P= 0.001) and GCC global loss volume (GLV; 0.88, P= 0.01) in differentiating perimetric glaucoma from control eyes. In differentiating preperimetric glaucoma from control eyes, AUC of SAR (0.72) was comparable to that of GCC average thickness (0.70, P> 0.05) and GLV (0.72, P> 0.05). Sensitivities at specificities of 80% and 95% of SAR were comparable (P > 0.05 for all comparisons) to that of GCC average thickness and GLV in diagnosing perimetric and preperimetric glaucoma.

Conclusion:

GCC SAR had a better ability to diagnose perimetric glaucoma compared to the SDOCT software provided global GCC parameters. However, in diagnosing preperimetric glaucoma, the ability of SAR was similar to that of software provided global GCC parameters.

Baseline risk factors for incidence of blindness in a South Indian population: the chennai eye disease incidence study

PURPOSE

To report the baseline risk factors and causes for incident blindness.

METHODS

Six years after the baseline study, 4419 subjects from the cohort underwent a detailed examination at the base hospital. Incident blindness was defined by World Health Organization criteria as visual acuity of less than 6/120 (3/60) and/or a visual field of less than 10° in the better-seeing eye at the 6-year follow-up, provided that the eye had a visual acuity of better than or equal to 6/120 (3/60) and visual field greater than 10° at baseline. For incident monocular blindness, both eyes should have visual acuity of more than 6/120 (3/60) at baseline and developed visual acuity of less than 6/120 (3/60) in one eye at 6-year follow-up.

RESULTS

For incident blindness, 21 participants (0.48%, 95% confidence interval [CI], 0.3-0.7) became blind; significant baseline risk factors were increasing age (P = 0.001), smokeless tobacco use (P < 0.001), and no history of cataract surgery (P = 0.02). Incident monocular blindness was found in 132 participants (3.8%, 95% CI, 3.7-3.8); it was significantly more (P < 0.001) in the rural population (5.4%, 95% CI, 5.4-5.5) than in the urban population (1.9%, 95% CI, 1.8-1.9). Baseline risk factors (P < 0.001) were increasing age and rural residence, and no history of cataract surgery was a protective factor (P = 0.03).

CONCLUSIONS

Increasing age was a significant risk factor for blindness and monocular blindness. No history of cataract surgery was a risk factor for blindness and a protective factor for monocular blindness.

Long-term change in central corneal thickness from a glaucoma perspective

AIM

To investigate the longitudinal change in central corneal thickness (CCT) over 3 years in patients with glaucoma.

MATERIALS AND METHODS

The Chennai Glaucoma Follow-up Study, an offshoot of the Chennai Glaucoma Study, was designed to evaluate the progression of glaucoma. A cohort of participants in the Chennai Glaucoma Study that were suffering from glaucoma or were at a higher risk for glaucoma underwent comprehensive ophthalmic evaluation at the base hospital at 6-month intervals during the years 2004 to 2007. The CCT (average of 10 readings) was measured between 11 am and 1 pm on any given day using an ultrasonic pachymeter. Patients with a history of ocular surgery, corneal disease and usage of topical carbonic anhydrase inhibitor were excluded. No patient was a contact lens wearer.

RESULTS

One hundred and ninety-six patients (84 male, 112 female) met the inclusion criteria. We analyzed data from the right eye. The mean age of the patients was 59.97 ± 9.06 years. Fifty-nine (30.1%) of the patients were diabetic. The mean change in CCT (CCT at first patient visit--CCT at last patient visit) was 3.46 ± 7.63 μm. The mean change in CCT was 0.75 μm per year (R² = 0.00). Age, gender, intraocular pressure at the first patient visit and diabetic status had no significant influence on the magnitude of change in CCT.

CONCLUSION

A carefully obtained CCT reading by a trained examiner need not be repeated for at least 3 years as long as the ocular and systemic factors known to affect the measurement of CCT are constant.

Intra-bleb hematoma and hyphema following digital ocular compression

We report successful outcome of a huge post- trabeculectomy intra-bleb hematoma and hyphema that occurred following digital ocular compression. The patient was a 64-year-old lady suffering from bilateral primary angle closure glaucoma and cataract. She was on anti-platelet therapy. She underwent single-site phacoemulsification, intra-ocular lens implantation and trabeculectomy with mitomycin C in the right eye. The trabeculectomy was under-filtering. She was asked to perform digital ocular compression thrice daily. On 15^th post-operative day, she presented with a huge intra-bleb hematoma and hyphema. The hematoma did not respond to conservative measures and was drained to prevent bleb failure. We recommend caution in the consideration of digital ocular compression in patients on prophylactic anti-coagulation.

Retinal nerve fiber layer evaluation of spectral domain optical coherence tomograph and scanning laser polarimeter to diagnose glaucoma

PURPOSE

To compare the abilities of retinal nerve fiber layer (RNFL) parameters of spectral domain optical coherence tomograph (SDOCT) and scanning laser polarimeter (GDx enhanced corneal compensation; ECC) in detecting glaucoma.

METHODS

In a cross-sectional study, 215 eyes of 165 subjects (106 eyes of 79 glaucoma patients and 109 eyes of 86 controls) referred by general ophthalmologists for glaucoma evaluation underwent RNFL imaging with SDOCT and GDx ECC. Ability of RNFL parameters of SDOCT to discriminate glaucoma eyes from control eyes was compared with that of GDx ECC using area under operating characteristic curves (AUCs), sensitivities at fixed specificities, and likelihood ratios (LRs).

RESULTS

AUC of the average RNFL thickness of SDOCT to differentiate glaucoma from control eyes (0.868) was comparable (P=0.32) to that of GDx ECC (0.855). Sensitivity at 95% specificity was 63.2% for average RNFL thickness of SDOCT and 48.1% for the average RNFL measurement of GDx ECC. LRs of outside normal limits category of SDOCT parameters ranged between 5.6 and 7.7 while the same of GDx ECC parameters ranged between 3.1 and 3.7. LRs of within normal limits category of SDOCT parameters ranged between 0.18 and 0.24 while the same of GDx ECC parameters ranged between 0.20 and 0.32.

CONCLUSION

Though AUCs and sensitivities at fixed specificities were comparable between the RNFL parameters of SDOCT and GDx ECC in diagnosing glaucoma, LRs indicated that the RNFL parameters of SDOCT were better in 'ruling in' glaucoma.

Six-year incidence of angle-closure disease in a South Indian population: the Chennai Eye Disease Incidence Study

PURPOSE

To estimate the 6-year incidence of primary angle-closure (PAC) disease among adult population aged 40 years and older from rural and urban south India.

DESIGN

Population-based longitudinal study.

METHODS

A complete ophthalmologic examination, including applanation tonometry, gonioscopy, biometry, stereoscopic fundus examination, and automated perimetry was performed at both baseline and at the 6-year follow up at base hospital. Incident PAC disease was defined as the development of PAC disease during the 6-year follow-up in phakic subjects without PAC disease at baseline. Diagnosis was made using the International Society Geographical and Epidemiological Ophthalmology classification.

RESULTS

The data were analyzed for 3350 subjects (mean age, 56.4 ± 8.9 years; 1547 males, 1803 females) for a diagnosis of PAC disease at baseline and at follow-up examinations. The incidence of PAC disease was identified in 134 subjects (6-year incidence rate, 4.0%; 95% confidence interval (CI), 3.3-4.7). Among the 134 subjects, 88 subjects (2.6%, 95% CI, 2.1-3.2) were primary angle-closure suspects; 37 subjects (1.1%, 95% CI, 0.7-1.5) had primary angle closure, and 9 subjects (0.3%, 95% CI, 0.1-0.4) had primary angle-closure glaucoma. There was an inverse relationship between the incidence of PAC disease and the cataract surgery rates. Significant risk factors for PAC disease on logistic regressions were higher intraocular pressure, increased lens thickness, shorter axial length, shallow anterior chamber depth, anteriorly positioned lens, and hyperopia.

CONCLUSIONS

The average incidence of PAC disease per year was 0.7%. All biometric parameters were found to be strong predictors for the incidence of PAC disease.

Our experience of fibrin sealant-assisted implantation of Ahmed glaucoma valve

Aim:

To report our experience with the fibrin sealant as a suture substitute for securing the human scleral patch graft during implantation of Ahmed glaucoma valve (AGV).

Materials and Methods:

A retrospective, non-comparative study of 12 eyes of 12 patients who underwent an AGV implantation with fibrin sealant for part of the procedure during June 2009 to September 2010.

Results:

The mean patient age was 21.5 ± 20.6 years. Male: Female ratio was 2 : 1. Seven (58.3%) patients were monocular. The indications for AGV were varied. The mean number of intra-ocular surgeries prior to an implantation of AGV was 1.8. The mean follow-up duration was 24.5 ± 17.9 weeks. There was a statistically significant reduction in the mean IOP and in the mean number of anti-glaucoma medications at the final visit compared to the pre-operative values (P < 0.01, paired t test). Conjunctival retraction was seen in 1 (8.3%) case. The scleral patch graft was retracted posteriorly in another (8.3%) case. There was no case of AGV tube exposure, tube-cornea touch, or conjunctival erosion. Vision threatening complication viz. late post-operative rhegmatogenous retinal detachment, unlikely to be related to the use of the fibrin sealant, occurred in 2 (16.6%) eyes.

Conclusion:

The fibrin sealant offers the advantages of safety and convenience to the placement of a scleral patch graft during an AGV implantation.

Ability of different scanning protocols of spectral domain optical coherence tomography to diagnose preperimetric glaucoma

PURPOSE

To evaluate the ability of the optic nerve head (ONH), retinal nerve fiber layer (RNFL), and ganglion cell complex (GCC) parameters of spectral domain optical coherence tomograph (SDOCT) in detecting preperimetric glaucoma.

METHODS

In a cross-sectional study, 34 preperimetric glaucoma eyes (34 patients) and 72 control eyes (72 subjects) with large physiologic optic disc cupping underwent ONH, RNFL, and GCC imaging with SDOCT. Preperimetric glaucoma was diagnosed in the presence of glaucomatous optic neuropathy on masked evaluation of optic disc photographs by two glaucoma experts and normal visual fields. The ability of SDOCT parameters to discriminate preperimetric glaucoma eyes from eyes with large physiologic cups was evaluated by areas under the receiver operating characteristic curves (AUC), sensitivities at fixed specificities, and likelihood ratios (LR).

RESULTS

All SDOCT parameters were significantly different (P < 0.05) between the two groups. The ONH, RNFL, and GCC parameters with best AUCs to differentiate preperimetric glaucoma from eyes with large physiologic cups were vertical cup to disc ratio (0.76), inferior quadrant RNFL thickness (0.76), and inferior quadrant GCC thickness (0.75), respectively. Sensitivities at 95% specificity of SDOCT parameters ranged between 15% and 29%. Likelihood ratios of outside normal limits category of parameters ranged between 3 and 11, and within normal limits category between 0.5 and 0.8.

CONCLUSIONS

Diagnostic abilities of ONH, RNFL, and GCC parameters of SDOCT to differentiate preperimetric glaucoma eyes from control eyes with large physiologic cupping were only moderate.

Inadvertent rupture of iridociliary cyst following transscleral Diode laser

Primary iridociliary cysts can induce plateau iris configuration and angle closure glaucoma. We report a patient with bilateral, primary, ring-shaped, solitary iridociliary cysts. The right eye displayed normal intraocular pressure, oppositional iridocorneal angle closure, and healthy optic nerve head. The left eye had advanced chronic angle closure glaucoma. The management strategy varied between eyes and is discussed. This, to the best of our knowledge, is the first report of transscleral Diode laser application in an eye with a large iridociliary cyst.

Tonometry and Care of Tonometers

Intraocular pressure (IOP) remains the only modifiable risk factor in the management of glaucoma. Hence, IOP and its appropriate measurement deserve our ongoing interest. Over the years, not only has our understanding of glaucoma changed but also has changed our approach to the measurement of the IOP. This review is an attempt to elucidate the commonly techniques of tonometry, and critically evaluate each of them, in current glaucoma practice.

How to cite this article: Maheshwari R, Choudhari NS, Singh MD. Tonometry and Care of Tonometers. J Current Glau Prac 2012;6(3):124-130.

Effect of spectrum bias on the diagnostic accuracy of spectral-domain optical coherence tomography in glaucoma

PURPOSE

To evaluate the influence of a control group on the diagnostic accuracy of spectral-domain optical coherence tomography (SD-OCT) in early glaucoma.

METHODS

In a diagnostic, case-control study, 119 eyes of 60 normal subjects with no findings suspicious for glaucoma (control cohort 1); 76 eyes of 41 subjects referred by general ophthalmologists as glaucoma suspects based on optic disc morphology, but found by glaucoma experts to be normal but with physiological variations in their optic nerves (control cohort 2); and 65 eyes of 46 early-glaucoma patients (cases) underwent imaging of the optic nerve head (ONH), retinal nerve fiber layer (RNFL), and ganglion cell complex (GCC) by SD-OCT.

RESULTS

Areas under the receiver operating characteristic curves (AUC) of ONH parameters discriminating glaucomatous eyes from normal eyes of control cohort 2 were significantly lesser (P < 0.001) than those discriminating glaucomatous eyes from normal eyes of control cohort 1. AUCs of RNFL parameters discriminating glaucomatous eyes from normal eyes of control cohorts 2 and 1 were comparable. Although the AUCs of GCC thickness parameters were comparable, AUCs of GCC focal and global loss volume in control cohort 2 (0.684 and 0.671. respectively) were significantly less (P < 0.05) than in control cohort 1 (0.881 and 0.841, respectively).

CONCLUSIONS

The effectiveness of most SD-OCT parameters in detecting glaucoma significantly decreased when evaluated against a clinically relevant control group with suspicious-looking optic nerves compared with that against a control group consisting of normal subjects with no findings suspicious for glaucoma.

Cupped disc with normal intraocular pressure: the long road to avoid misdiagnosis

We present a series of six patients who had been receiving treatment for normal tension glaucoma (NTG; five patients) or primary open angle glaucoma (one patient). All of them were found to have optic neuropathy secondary to compression of the anterior visual pathway. Even though uncommon, compression of the anterior visual pathway is an important differential diagnosis of NTG. Diagnosis of NTG should be by exclusion. Here the possible causes of misdiagnosis are discussed. We present an approach to distinguish glaucomatous from nonglaucomatous optic neuropathy. The article also emphasizes how important it is for the clinicians to consider the total clinical picture, and not merely the optic disc morphology, to avoid the mismanagement of glaucoma, especially the NTG.

Anterior ischemic optic neuropathy precipitated by acute primary angle closure

A 59-year-old man with a history of longstanding systemic hypotension developed asymmetric non-arteritic anterior ischemic optic neuropathy (NAION) apparently precipitated by bilateral sequential acute primary angle closure. NAION is very rarely reported in association with raised intraocular pressure. In contrast to optical coherence tomography, the failure of scanning laser polarimetry to detect axonal swelling was another interesting finding. Possible reasoning for these observations is discussed.

Intravitreal cysticercosis presenting as neovascular glaucoma

We report two cases of intraocular cysticercosis which showed a peculiar presentation of neovascular glaucoma which is hitherto unreported. Two young adults presented with symptoms of raised intraocular pressure due to neovascular glaucoma. On dilated fundus examination both were found to have dead intravitreal cysticercosis. The cysts were removed by a three-port vitrectomy and intracameral injection of bevacizumab was given to help in the regression of rubeosis. Trabeculectomy had to be combined in one case. The intraocular pressure returned to normal. No recurrence of rubeosis was seen even after one year.