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.

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 signifi cance map. Statistical Analysis: Diagnostic ability of SAR in glaucoma was compared against that of the standard parameters generated by the SDOCT soft ware using area under receiver operating characteristic curves (AUC) and sensitivities at fi xed specifi cities. Results: AUC of SAR (0.91) was statistically signifi cantly bett er than that of GCC average thickness (0.86, P = 0.001) and GCC global loss volume (GLV; 0.88, P = 0.01) in diff erentiating perimetric glaucoma from control eyes. In diff erentiating 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 specifi cities 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 bett er ability to diagnose perimetric glaucoma compared to the SDOCT soft ware provided global GCC parameters. However, in diagnosing preperimetric glaucoma, the ability of SAR was similar to that of soft ware provided global GCC parameters.

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.

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.

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.

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.