Ultrasound Biomicroscopic Assessment of Angles after Laser Peripheral Iridotomy in Primary Angle Closure and Primary Angle Closure Glaucoma Patients

INTRODUCTION: Glaucoma is the second leading cause of blindness worldwide & is especially common & morbidity causing among women and Asians. Glaucoma afflicts 12 million people in our country. Primary open angle glaucoma is more common in general population. However angle closure glaucoma tends to be more aggressive & visually debilitating. Inspite of being treated with iridotomy, medical & surgical management, it continues to produce excessive visual morbidity. Acute angle closure glaucoma which is vision threatening is a potentially preventable condition and hence early identification and treatment with laser peripheral iridotomy in susceptible patients is of utmost importance. AIMS AND OBJECTIVES: To study the angle morphology before and after laser peripheral iridotomy in patients with primary angle closure & primary angle closure glaucoma. METHODOLOGY: Prospective observational study to study the changes in anterior chamber angle structures before and after laser peripheral iridotomy using Ultrasound biomicroscopic technique. The study was conducted in patients presenting to the glaucoma clinic of the department of ophthalmology of Govt Rajaji Hospital, Madurai for the period of 6 months. A total of 50 patients were studied. Patients presenting with shallow angles were studied & their complete history, assessment of anterior segment which includes slit lamp examination, gonioscopy by Goldman 3 mirror goniolens, IOP measurement by applanation tonometry, fundus examination using +90D lens and standard perimetry was done. The patients were categorised as Primary angle closure or as Primary angle closure glaucoma depending on the clinical findings. Then Ultrasound biomicroscopic assessment was done prior to and after 2 weeks of laser peripheral iridotomy to measure central ACD (anterior chamber depth), AOD (angle opening distance), TIA (trabecular iris angle) & other angle parameters. Results were analysed statistically. RESULTS: Among the total studied population of 50 patients, 48% were diagnosed to have primary angle closure & remaining 52% had primary angle closure glaucoma. In the PAC group: There was a significant change in all the parameters measured. ACD (mm) changed from an average from 2.199±0.04 to2.32±0.00 with a p value of ˂ 0.001. AOD 500 (Angle opening distance mm) increased from an average of 0.106 ± 0.0 to 0.209 ± 0.0 with a p value of ˂ 0.001. Sup TIA (deg) increased from an average of 8.252±0.16 to 16.081±0.23 with a p value of ˂ 0.001. Inf TIA (deg) increased from an average of 9.125±0.04 to 16.118±0.24 with a p value of ˂ 0.001. TCPD (TRABECULAR CILIARY BODY DISTANCE mm) increased from an average of 0.745 ± 0.0 to 0.82 ± 0.01 with a p value of ˂ 0.001. IT (IRIS THICKNESS mm) increased from an average of 0.459 ± 0.01 to 0.487 ± 0.00 with a p value of ˂ 0.001 ILCD (IRIS LENS CONTACT DISTANCE mm) decreased from an average of 1.217 ± 0.05 to 1.162 ± 0.02 with a p value of ˂ 0.001. ILA (IRIS LENS ANGLE deg) ) increased from an average of 25.729 ± 0.52 to 27.754 ± 0.57 with a p value of ˂ 0.001. In the Primary angle closure glaucoma group: There was no significant change in any of the measured parameters. CONCLUSION: Among the studied population, observation in the angle characteristics showed that there was statistically significant change in the UBM parameters noted in the primary angle closure group, however no such significant change was noted in the primary angle closure glaucoma group. Hence effective strategies should be adopted in order to identify angle closure at an early stage so that they can be treated prior to development of irreversible angle closure glaucoma

Comparative study of anterior chamber depth pre and post prophylactic laser iridotomy in angle closure suspects

Individuals aged above 40 years and females are at more risk for the angle closure disease. • Ocular risk factors for angle closure are hyperopia, short axial length and shallow anterior chamber depth. • Van Herick's method although subjective is reliable when done by experienced person. The peripheral anterior chamber depth shows an increase following laser iridotomy. • Gonioscopy is reliable and equally effective in grading the anterior chamber angle and aids in identifying those at risk of angle closure. • Ultrasound biomicroscopy can measure the exact central anterior chamber depth. There is only a minimal increase in the central anterior chamber depth following peripheral iridotomy. • With a 50 MHz UBM, a quantitative assessment of the iris curvature and degree of angle opening can be identified.It can also be used to find the trabecular iris angle, trabecular-ciliary process distance, iris-ciliary process distance and iris-lens contact distance which can help in detailed evaluation of the anterior chamber angle. • Laser peripheral iridotomy proves to be a boon for the eyes with angle closure disease in its early stages. • Since visual loss resulting from PACG is potentially preventable, careful surveillance for risk factors of angle closure, widespread use of gonioscopy to identify occludable angles and peripheral iridotomy performed at an early stage can reduce the morbidity resulting from PACG. CONCLUSION: Van Herick’s method is useful in primary screening of the peripheral anterior chamber depth. • Gonioscopy helps in identifying angle closure suspects. • UBM helps in the exact measurement of central anterior chamber depth. • Laser peripheral iridotomy prevents angle closure in angle closure suspects

Glaucoma

This book addresses the basic and clinical science of glaucomas, a group of diseases that affect the optic nerve and visual fields and is usually accompanied by increased intraocular pressure. The book incorporates the latest development as well as future perspectives in glaucoma, since it has expedited publication. It is aimed for specialists in glaucoma, researchers, general ophthalmologists and trainees to increase knowledge and encourage further progress in understanding and managing these complicated diseases

A prospective study of visual outcome in lens induced glaucomas following surgery

INTRODUCTION Cataract and glaucoma are the leading causes of blindness through out the world. Of the total 45 million blind persons (Visual acuity < 3/60) in the world, 7 million are in India. Glaucoma accounts for 5.8% of all types of blindness in India with a prevalence of 4% in population aged 30 years and above. Glaucoma is not a single disease process. It is a group of disorders characterized by widely different clinical and histopathological manifestation. These disorders share characteristic changes in visual field, optic nerve head and usually have increase in Intra ocular pressure. Intraocular pressure is only a risk factor. There are many etiologies of glaucoma lens induced glaucoma is one of them. AIM OF THE STUDY: To determine the frequency and types of lens – induced glaucoma and outcome of current management. METHODS: Prospective case series of 413 patients / eyes with lens induced. Glaucoma over a 12 month period in 1998 ; 311 of these patients underwent cataract surgery. Visual acuity and intraocular pressure were pre and post operatively assessed. CONCLUSION: In our study mean age of presentation is 60 years Female : Male ratio is 1.4 : 1 Higher incidence of phacomorphic than phacolytic glaucoma There is no relation between final visual acuity and type of surgery. Increased incidence of complications in both groups. Visual prognosis is almost similar in both groups after surgery Post operative visual status and duration of attack had significant association and not the height of IOP. Preoperative faulty projection of light need not defer definitive cataract surgery. These results highlight the importance of early diagnosis and treatment of mature cataract. There is a need to educate both the patients and the cataract surgeon of the dangers of lens induced. Glaucoma and of the poor outcome if treatment is delayed

Prevalence and clinical characteristics of primary angle closure in adult Chinese in Liwan District, Guangzhou.

In 2003, a population survey was carried out in Guangzhou, a large city in southern China, to investigate the prevalence and clinical characteristics of glaucoma in a representative sample of people in one city district. Standard laser iridotomy was performed in one randomly selected eye of the subjects with suspected angle-closure (those with occludable angles but without raised intraocular pressure or peripheral anterior synechiae). Clinical ocular and ultrasound biomicroscopic examination were carried out before and 2 weeks after laser treatment. Among 1,405 people aged 50 years and over examined (at a 75.3% response rate), crude prevalence of all glaucomatous optic neuropathy was 3.8% (95%CI: 2.8-4.8%), increasing from 1.1% in the 50-59 age group to 5.5% in those aged 70 years and older. The ratio of PACG / POAG cases was 21/29. Prevalences of occludable angles and primary angle closure were found to be 10.2% (95%CI: 8.6-11.8%) and 2.4% (95%CI: 1.6-3.1%) respectively. Seventy-four subjects in underwent laser iridotomy on one randomly selected eye. The mean IOP before laser was close to the population mean, and fell by an average of 3 mm Hg after laser. Mean ACD, lens thickness and axial length did not change after treatment. UBM quantitative analysis suggested mean drainage angle width increased by 2.6 times in superior quadrant. The iris curvature radius increased from 5.02 mm to 13.31 mm after treatment suggesting marked flattening of the iris. Distance between ciliary body to trabecular meshwork increased from 0.537mm to 0.561mm (PO.0001) suggesting the backward movement of the ciliary body. Iris thickness at 750 micro m location increased after laser suggesting flattening and a reduction of tension on the iris after pupil block had been eradicated. About one-fifth (14/74) of the treated eyes remained "gonioscopically occludable" even after a patent peripheral iridotomy (PI) had been created. The UBM characteristics of those remaining occludable included: anterior rotation of the ciliary body, angulated or anterior location of the iris insertion and thickening of peripheral iris. This study suggests that the prevalence of primary angle closure was comparable to that found in Singapore and Mongolia. Pupil-block was a significant mechanism in 80% of cases of angle-closure

Cost-Effectiveness of Selective Laser Trabeculoplasty (SLT) versus Argon Laser Trabeculoplasty (ALT) in Uncontrolled Open Angle Glaucoma Patients having at least One Full Previous SLT: An Economic Evaluation Alongside an Ongoing Randomized Controlled Clinical Trial

Background and objective: ALT and SLT are both safe and effective for glaucoma treatment. We performed a cost-effectiveness analysis (CEA) of SLT versus ALT for a six-month follow-up period in uncontrolled open angle glaucoma patients having at least one full previous SLT from an ongoing RCT. Methods: Trial based treatment costing and IOP reduction at 6-month follow-up from baseline for both intervention arms were calculated. A decision tree model was developed considering possible clinical pathways of patients undergoing repeat laser trabeculoplasty. CEA among ALT and SLT was done, and ICERs were calculated from both societal and ministry perspective. One way sensitivity analysis was done for cost and effectiveness parameters. Results: From Societal perspective, expected cost/effectiveness for ALT and SLT was $458/0.143 mmHg vs$448/0.123 mmHg respectively and from ministry perspective, $467/0.154 mmHg vs$446/0.122 mmHg, respectively. To switch from SLT to ALT, it would cost $356.49 for each extra unit IOP reduction from societal perspective and from ministry perspective, the same would cost$ 649.71. This ICERs were much higher in comparison to ICERS of other IOP lowering medications in similar situations. Conclusion: Neither ALT nor SLT strategies were clearly dominated by any other. ALT is slightly more effective and slightly costly over SLT. Sensitivity analysis with effectiveness variables showed dominance of SLT over ALT for some instances. SLT has the theoretical plausibility of repeatability and is also easier to perform than ALT. All these factors should be considered when opting between ALT and SLT strategies

An investigation into anterior segment anatomy and genetics of pigment dispersion syndrome

Pigment dispersion syndrome (PDS) is an ocular condition predisposing to glaucomatous optic neuropathy in patients at a relatively young age. Concavity of the iris is considered to be important in the pathogenesis of PDS, however, it is also appears to be a feature of non-PDS eyes, particularly in young myopes. Much of the current understanding of anterior segment anatomy is derived from studies using ultrasound biomicroscopy, a relatively invasive imaging modality that involves direct ocular contact. Anterior-segment optical coherence tomography (AS-OCT) allows imaging of the anterior segment with the patient in the upright position without the need for contact with the ocular surface. AS-OCT may allow a more physiological assessment of anterior segment anatomy as well as being better suited to paediatric subjects. AS-OCT was used to conduct a case-control study of anterior segment anatomy in PDS subjects and age-, sex- and refraction- matched controls to determine which features of anterior segment anatomy best discriminated between the 2 groups. In addition AS-OCT was used to assess anterior segment anatomy, with particular emphasis on iris curvature, in a cohort of 10-12 year old school children and explore correlations with ocular biometry and parameters reflecting corneal biomechanical properties. Longitudinal data was collected through re-visiting the cohort 2 years later. Chromosomal susceptibility loci for PDS have been described, although no causative gene has been identified. Two approaches were used to identify novel disease susceptibility loci: 1) linkage analysis was used in a 3-generation family segregating for PDS/pigmentary glaucoma, and, 2) DNA from a large cohort of unrelated PDS probands was collected and sent for genotyping with a view to conducting a pilot genome-wide association study. Finally a candidate gene, GPNMB, the human homologue of a causative gene in a mouse model of pigmentary glaucoma was sequenced in a panel of 96 unrelated PDS/pigmentary glaucoma subjects