I don’t see a lot of patients with glaucoma and epiphora, but the studies below discuss important issues relevant to all our everyday practices. Enjoy, and don’t forget I enjoy feedback, and questions!
Cheers
Malcolm


What do iridotomies really do?

Changes in Anterior Segment Morphology and Predictors of Angle Widening after Laser Iridotomy in South Indian Eyes

Zebardast N, Kavitha S, Krishnamurthy P, et al. Ophthalmol 2016; 123: 2519-2526

The purpose of this prospective observational study was to compare anterior segment optical coherence tomography (ASOCT) angle morphology before and after laser peripheral iridotomy (LPI) and to examine baseline parameters associated with angle widening in a cohort of 244 South Indian subjects. Subjects were aged >30 years with primary angle closure suspect (PACS) or primary angle closure/primary angle closure glaucoma (PAC/PACG) in at least 1 eye. The ASOCT images and angle gonioscopic grades were analysed for all subjects at baseline and 2 weeks after LPI. Multivariable linear and logistic regression models were used to determine predictors of angle widening (change in mean angle opening distance at 750µm [AOD750]) and angle opening (all 4 quadrants with trabecular meshwork [TM] visible on gonioscopy after LPI).

Results showed that LPI resulted in angle widening on ASOCT with significant increases in AOD750, angle recess area, and trabecular iris surface area (P < 0.05 for all). Gonioscopically, 44.7% of all subjects had open angles in all 4 quadrants after LPI with a greater percentage of angles open in the PACS group compared with the PAC/PACG group (52.4% vs 36.4%; P = 0.01). In multivariable regression analyses, greater postoperative angle widening as defined by change in AOD750 was associated with shorter baseline AOD750 and axial length, and greater baseline anterior chamber depth, iris curvature, and lens vault (P < 0.002 for all). Gonioscopic angle opening after LPI was more common with wider baseline angle width (modified Shaffer grade) and lower cup-to-disc ratio (P < 0.001 for both). The authors conclude that LPI results in significant anterior chamber angle widening in a South Indian population with PACS or PAC/PACG, seen on both ASOCT and gonioscopy. The authors note that approximately half of PACS eyes and two thirds of PAC/PACG eyes maintained some degree of persistent iridotrabecular contact seen with gonioscopy. The authors also noted that the greatest widening by ASOCT was observed in eyes with features most consistent with greater baseline pupillary block.

My comment:

Angle closure is common in India and much of what we know about this condition comes from studying this population. When I was training as an optometrist we were taught that LPIs created an emergency pathway for aqueous to access the trabecular meshwork if angle closure occurs (sometimes, lazily, we still use this analogy with patients). Training as an ophthalmologist I was often confused by the gonioscopy appearance of patients who had had a LPI. The angle seemed wide open; why had my colleague decided the patient needed laser? What I/we now know is that LPIs alter the physiology of the anterior segment. Connecting the anterior and posterior segments opens the angle, indeed to a greater degree in those patients with the narrowest angles.


The trap of colour coded OCT results.

Green Disease in Optical Coherence Tomography Diagnosis of Glaucoma

Sayed MS, Margolis M, Lee RK. Curr Opin Ophthalmol 2017; 28: 139-153

Optical coherence tomography (OCT) has become a key component in glaucoma diagnosis and monitoring. This review discusses “green disease”, conditions in which OCT colour coding may be falsely negative. For example, in early glaucoma when the retinal nerve fibre layer (RNFL) thickness and optic disc parameters may be asymmetric between the two eyes but still labelled green, resulting in glaucoma not being detected; progressive decreasing of the RNFL thickness in progressive glaucoma may be missed by the clinician due to green labelling. Coexisting glaucoma diagnosis may be difficult in the presence of other ocular conditions that can increase RNFL thickness. Progression analysis features of OCT have recently been introduced and may help detect green disease. The authors summarise that it is of paramount importance to recognise green disease when diagnosing and treating glaucoma. The limitations of imaging technologies must be understood and prompt clinical examination, serial OCT analyses, and structure-function correlation is important to avoid missing glaucoma requiring treatment.

My comment:

OCT is an essential piece of kit and has a multitude of uses in the diagnosis and monitoring of ocular diseases, including glaucoma. However, we can become reliant on the technology. OCT can make us more certain, but not right. A green “normal” result may sway decisions towards monitoring for example, when in fact treatment may be necessary based on the other clinical findings such as physical appearance of the optic nerve head, serial examinations, intraocular pressure and visual field analysis. It is important to remember that diagnosing glaucoma is like assembling a jigsaw puzzle, of which the OCT result is just one piece. Oh, and just important, watch out for “red disease” too!


Common medical conditions and glaucoma. Are they related?

Associations between Chronic Systemic Diseases and Primary Open Angle Glaucoma: an Epidemiological Perspective

Tham YC, Cheng CY. Clin Exp Ophthalmol 2017; 45: 24-32

This review article aims to summarise the current evidence on the association between some chronic systemic diseases such as hypertension, diabetes and obesity with primary open angle glaucoma (POAG). POAG affects 44.1 million individuals worldwide. Intraocular pressure elevation and impairment of the vascular supply to the optic nerve head are two key pathogenic processes in its development. Chronic systemic diseases may act as risk factors for POAG. The authors summarise and discuss the current evidence on the associations of chronic diseases with POAG to help further ascertain the risk factors for POAG in order to improve its early detection.

Hypertension: There may be an association. Epidemiological studies have reported conflicting findings regarding the association between hypertension and POAG. Several mechanisms of association have been suggested. First, hypertension may lead to microvascular impairment in the retina and optic nerve head (ONH) region, which may in turn reduce the blood flow to the anterior ONH. Second, hypertension may impair the autoregulation of posterior ciliary circulation, which is the main source of blood supply to the ONH. Third, antihypertensive treatment could induce hypotensive episodes or excessive nocturnal dipping of blood pressure, leading to lower ocular perfusion of the ONH. Finally hypertension may also lead to retinal vascular narrowing, which may also affect blood supply to the ONH.

Diabetes: Again, epidemiological studies have reported conflicting findings regarding the association between diabetes and POAG. Diabetes may cause microvascular damage and impair vascular autoregulation of the retina and optic nerve. Diabetes may also affect the metabolism of retinal neuronal cells, such as the retinal ganglion cells, potentially increasing susceptibility to POAG. It has also been suggested that hyperglycaemia is associated with depletion of trabecular meshwork cells, thus impairing the aqueous humour outflow system and potentially resulting in IOP elevation.

Obesity: It has been suggested that lower body mass index (BMI) may be associated with POAG due to less optimal nutritional state, or the association may be indirect as lower BMI is correlated to lower cerebrospinal fluid pressure, which has been reported as a potential risk for POAG. Other studies report that higher BMI was associated with higher IOP, which is a main risk factor for POAG. The association between BMI and POAG, and between BMI and IOP, are counterintuitive. Further evaluation is warranted.

My comment:

The first lesson, and one we keep forgetting, is that it can take many studies before we get to the truth. In all three of these conditions, the evidence for an association with glaucoma is contradictory. Further large studies are required to gather more data and shed some light on these potential associations with POAG. So what do we do, and what do we tell our patients? Well, it’s never a bad idea to more thoroughly examine patients with systemic conditions such as these for early signs of glaucoma. You could even outline that there may be a link between diabetes, obesity, hypertension, and glaucoma. Anything to encourage patients to take care of themselves is a good thing. Just don’t be too sure or hung up on the risks.


Is DCR worth the risk in elderly patients?

Dacryocystorhinostomy for Acquired Nasolacrimal Duct Stenosis in the Elderly (> 80 Years of Age)

Tooley AA, Klingler KN, Bartley GB, et al. Ophthalmol 2017; 124: 263-267

The purpose of this retrospective cohort study was to examine surgical outcomes and complication rates of dacryocystorhinostomy (DCR) in an elderly population. The incidence of acquired nasolacrimal duct obstruction (NLDO) increases with age. Its definitive treatment, DCR, has a high success rate (80%-100%) with a low complication rate (1%-6%), but surgical outcomes specifically for elderly patients have not been previously reported. Patients 80 years of age or older who underwent external DCR at the Mayo Clinic between January 1, 1990, and December 31, 2010 (42 DCRs in 32 patients), were compared with a matched control group of younger patients (40-79 years of age) who underwent external DCR by the same surgeons (73 DCRs in 63 patients). The medical charts of those patients were reviewed. Data included symptomatic relief and complications such as tube protrusion, infection, persistent bleeding, and return to operating room. Statistical analysis included a 2-sample t test to compare continuous variables, chi-square testing for categorical comparisons, and the generalised estimating equation model to control for nonidependence. The main outcome measure was symptomatic improvement at last follow-up. Secondary end points included anatomic patency, adverse event rate, and return to operating room within 1 month of surgery.

Results showed that resolution of symptom rate at last follow-up was 64% in the elderly group vs 86% in the younger cohort (P = 0.02). There was no difference between groups with respect to common postoperative complications, although there was a higher rate of predefined serious complications in the elderly group (5 events vs 1 event; P = 0.01). There was no difference between groups regarding the need for additional eyelid surgery (P = 0.30).

The authors conclude that although most elderly patients experience symptom resolution after DCR, the rate of symptom resolution was lower than that of younger patients. The risk of routine complications was similar between the groups. However, the risk of serious complications was higher in the elderly group.

My comment:

Nasolacrimal duct obstruction is common in the elderly. Although tear production also drops, disabling epiphora is often a problem. This study reinforces however that DCR should be approached with caution in older patients. Increasing age is an independent risk factor for perioperative complications and postoperative mortality. With an ageing population, the effect of age on surgical outcomes is becoming more relevant. In the case of DCRs in everyday practice, it is important to consider the risks vs benefits for elderly patients given that the symptom resolution rate is lower compared to younger patients and the risk of serious complications is higher. Put bluntly, having a cardiac event or stroke is worse than having epiphora. Older patients need more careful counselling prior to undertaking a DCR and surgery under local anesthesia should be considered.