Introduction

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  Intraocular pressure (IOP): this is determined by the balance between the rate of aqueous production and the rate of aqueous outflow. About 90% of the outflow is through the trabecular meshwork into the Schlemm canal and then into the episcleral veins ( Figs. 11.1A ) and 10% passes through the face of the ciliary body and iris (the uveoscleral route.) A reduction in outflow through the trabeculum causes a rise in IOP.

  
  

  
  

  
  

  

  
  

  
  

  (A) Routes of aqueous outflow: (a) trabecular, (b) uveoscleral, (c) iris, (B) distribution of IOP in the general population.

  
  

  (From Salmon JF, Kanski’s Clinical Ophthalmology: A Systematic Approach , 9th edition. Oxford, UK: Elsevier; 2020.)

  
  

Diagnosis

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  Normal IOP: mean IOP in the general population is 16 mm Hg; two standard deviations to either side of this gives a statistical ‘normal’ IOP range of 11–21 mm Hg ( Fig. 11.1B ). The upper range of normal is 23 mm Hg for individuals over 70 years.

  
  
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  Definition: 4–7% of individuals over the age of 40 years have an IOP >21 mm Hg without detectable glaucomatous damage; so-called ‘ocular hypertension’ (OHT).

  
  
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  Risk factors for conversion of OHT to glaucoma: (a) greater age, (b) higher IOP, (c) lower central corneal thickness, (d) larger C/D ratio, (e) higher ‘pattern standard deviation’ on perimetry.

Management

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  Most individuals with OHT do not require treatment: follow at yearly intervals.

  
  
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  Risk of conversion to POAG: after 5 years if untreated the risk is 9.5% and 4.4% if treated with an IOP-lowering eye-drop. Validated prediction models allow the risk for a given individual to be determined and expressed as a percentage.

  
  
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  Drug choice for those at high risk: as for primary open-angle glaucoma (see below).

  
  
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  Other considerations: (a) individual patient profile (e.g. age/life expectancy, patient preference and risk factors), (b) consider treating every patient with an IOP of ≥30 mm Hg.

Introduction

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  Definition: POAG is a chronic, progressive optic neuropathy of adult onset. It is characterized by: (a) retinal nerve fibre layer thinning, (b) glaucomatous optic neuropathy, (c) characteristic visual field loss as damage progresses, (d) an open anterior chamber angle, (e) absence of signs of secondary glaucoma, (f) IOP is a key modifiable risk factor.

  
  
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  Risk factors: (a) elevated IOP, (b) older age, (c) race (more common in black than white individuals), (d) family history of POAG (first-degree relatives), (e) myopia.

  
  
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  Epidemiology: glaucoma is the second commonest cause of blindness worldwide. Half of individuals with glaucoma are unaware that they have the condition.

  
  
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  Goal of treatment: to slow the rate of progression throughout the patient’s lifetime, in order to maintain visual function and a good quality of life.

Diagnosis

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  History: usually asymptomatic until damage is advanced: (a) past ophthalmic history including refractive status, (b) family history, (c) past medical history, (d) current medication.

  
  
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  General examination: (a) pupils, (b) slit lamp, (c) tonometry, (d) pachymetry for central corneal thickness (CCT), (e) gonioscopy, (f) optic disc examination with dilated pupils.

  
  
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  Perimetry : visual field defects include: (a) small paracentral depression (70% of early defects), (b) arcuate-shaped defect, (c) nasal step, (d) ring scotoma, (e) end-stage changes with a small residual island of central vision ( Fig. 11.2A–D ).

  
  

  
  

  
  

  

  
  

  
  

  Grey scale display showing progressive glaucomatous damage in different patients: (A) small paracentral defect, (B) nasal ‘step’, (C) extended arcuate defect, (D) ring scotoma.

  
  

  (From Salmon JF, Kanski’s Clinical Ophthalmology: A Systematic Approach , 9th edition. Oxford, UK: Elsevier; 2020.)

  
  
  
  
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  Imaging: (a) stereo disc photography, (b) confocal scanning laser tomography (e.g. Heidelberg retinal tomography), (c) scanning laser polarimetry (e.g. GDx) and especially (d) optical coherence tomography (OCT) ( Fig. 11.3 ).

  
  

  
  

  
  

  

  
  

  
  

  OCT of the optic disc showing infero-temporal thinning of the right RNFL and extensive thinning of the left RNFL.

  
  

  (From Salmon JF, Kanski’s Clinical Ophthalmology: A Systematic Approach , 9th edition. Oxford, UK: Elsevier; 2020.)

  
  

Management:

lowering IOP is the only proven method of slowing progression. A target IOP should be set with subsequent monitoring and target resetting if progression occurs.

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  Initial medical therapy: with one drug in its lowest concentration, instilled as infrequently as possible consistent with the desired effect (see later in this chapter).

  
  
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  Review: after 4–8 weeks, when response is assessed against target IOP. If satisfactory response, review in 3–6 months.

  
  
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  Causes of failure: (a) poor adherence (25% of patients), (b) inadequate instillation technique, (c) inappropriate target pressure, (d) IOP fluctuations including wide diurnal variation.

  
  
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  Ongoing monitoring: IOP, optic disc assessment, perimetry (annually in most low–moderate risk cases).

  
  
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  Laser trabeculoplasty: selective laser trabeculoplasty (SLT) or argon laser trabeculoplasty (ALT) can be used to replace or supplement medical treatment. Indications include: (a) patient preference, (b) intolerance of medical therapy, (c) avoidance of polypharmacy or surgery.

  
  
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  Indications for surgery: (a) failed medical therapy, (b) intolerance of medical therapy, (c) avoidance of polypharmacy, (d) progressive deterioration despite seemingly adequate IOP control, (e) as primary therapy in some patients.

  
  
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  Trabeculectomy: is the most common surgical procedure, although nonpenetrating surgery is also widely performed. If significant lens opacity is present, phacoemulsification alone may be associated with a fall in IOP; alternatively, it can be combined with a filtration procedure (e.g. phacotrabeculectomy). Mitomycin C is often used at the time of surgery to reduce the risk of postoperative bleb scarring.

  
  
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  MIGS: minimally invasive glaucoma surgery is commonly combined with cataract surgery and is not suitable for all forms of glaucoma. Current procedures can be divided into: (a) surgery that bypasses or manipulates the canal of Schlemm and (b) implants that result in the formation of a bleb (see later).

Introduction

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  Definition: This is a variant of primary open-angle glaucoma that features an IOP that is within the normal range. It is characterized by: (a) glaucomatous optic neuropathy, (b) characteristic visual field loss, (c) IOP consistently ≤21 mm Hg on diurnal testing, (d) open angle, (e) absence of signs of secondary glaucoma.

  
  
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  Distinction between NTG and POAG: this is an arbitrary division based on an epidemiologically derived range of normal IOP that may not have significant clinical value.

  
  
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  Risk factors: (a) age (older than in POAG), (b) race (particularly prevalent in Japan), (c) family history of glaucoma, (d) CCT (thinner than in POAG), (e) systemic hypotension including nocturnal blood pressure dips, (f) possibly abnormal vasoregulation (e.g. migraine, Raynaud phenomenon), (g) low CSF pressure.

  
  
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  Differential diagnosis: (a) nocturnal IOP spikes, (b) previous secondary raised IOP (trauma, uveitis, steroids, resolved pigmentary glaucoma), (c) masking of elevated IOP by systemic treatment with a beta-blocker, (d) previous acute optic nerve insult (e.g. anterior ischaemic optic neuropathy), (e) hypovolaemic or septicaemic shock, (f) progressive retinal nerve fibre defects not due to glaucoma (e.g. myopic degeneration, disc drusen), (g) congenital disc anomalies (e.g. disc pits, coloboma), (h) chiasmal or optic nerve compression.

Diagnosis

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  Specific points in the history: (a) migraine and Raynaud phenomenon, (b) an episode of hypovolaemic shock, (c) headache and other neurological symptoms, (d) intermittent use of topical and systemic steroids, (e) systemic beta-blockers.

  
  
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  Specific points in the examination: (a) IOP is usually in the high teens but may be lower, (b) glaucomatous cupping is similar to POAG, although focal neuroretinal notching is more common, (b) peripapillary atrophic changes and disc splinter haemorrhages are more frequent than in POAG.

  
  
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  Field defects : may be closer to fixation and more localized than in POAG.

  
  
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  Other investigations: as for POAG, but in certain patients consider assessment of: (a) systemic vascular risk factors, (b) 24-hour ambulatory blood pressure monitoring to exclude nocturnal systemic hypotension, (c) blood tests for other causes of nonglaucomatous optic neuropathy, (d) cranial MRI.

  
  
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  Indications for neuroimaging: (a) loss of VA out of proportion to cupping, (b) loss of colour vision on Ishihara testing, (c) visual field loss not consistent with retinal nerve fibre layer drop-out, (d) pallor of the neuroretinal rim, (f) rapid progression despite normal IOP.

Treatment

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  Indications: visual fields are stable in 50% over 5 years without treatment. In mild cases it may be appropriate to demonstrate progression before treating. IOP reduction is effective in reducing progression in many patients.

  
  
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  Topical: may include betaxolol (possibly by increasing optic nerve blood flow). Beware of using topical beta-blockers at bedtime (drop in nocturnal BP).

  
  
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  Surgery (or laser trabeculoplasty): if progression occurs despite reduced IOP.

  
  
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  Systemic: (a) control of systemic vascular disease, (b) calcium channel blockers to counter vasospasm, (c) if significant nocturnal dips in BP are detected, consider reducing antihypertensive medication (especially bedtime dosing), (d) sleep with the head of the bed elevated (IOP increases with supine positioning).

Introduction

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  Definition: ‘angle closure’ refers to occlusion of the trabecular meshwork by the peripheral iris–iridotrabecular contact (ITC), obstructing aqueous outflow. The condition is responsible for up to half of all cases of glaucoma globally and is typically associated with greater visual morbidity than POAG.

  
  
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  ‘Occludable angle’: where the pigmented trabecular meshwork is not visible in 3 out of 4 quadrants using a Goldmann lens, with the patient looking straight ahead in a dark room.

  
  
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  Grading of angle width: the Shaffer system is commonly used. The slit beam converges at the Schwalbe line ( Fig. 11.5 ). (a) Grade 4 (35–45°) wide open with ciliary body visible, (b) Grade 3 (25–35°) open angle with scleral spur visible, (c) Grade 2 (20°) trabeculum is visible, (d) Grade 1 (10°) only Schwalbe line is visible, (e) Grade 0 (0°) is closed due to iridocorneal contact

  
  

  
  

  
  

  

  
  

  
  

  Grading of angle width according to number of visible structures (see text). The slit beam converges at the Schwalbe line.

  
  

  (From Salmon JF, Kanski’s Clinical Ophthalmology: A Systematic Approach , 9th edition. Oxford, UK: Elsevier; 2020.)

  
  
  
  
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  Mechanisms: (a) pupillary block – failure of aqueous flow through the pupil leading to anterior bowing of the iris ( Fig. 11.6A ) is relieved by peripheral iridotomy, (b) non-pupillary block secondary to plateau iris, which is due to anteriorly positioned ciliary processes in the presence of a normal or slightly shallow central anterior chamber depth ( Fig. 11.6B ). A thick peripheral iris may be important in the pathogenesis in Asians.

  
  

  
  

  
  

  

  
  

  
  

  Mechanism of angle closure: (A) pupillary block, (B) plateau iris configuration using UBM (showing anteriorly rotated ciliary processes and slit-like angle).

  
  

  (From Salmon JF, Kanski’s Clinical Ophthalmology: A Systematic Approach , 9th edition. Oxford, UK: Elsevier; 2020.)

  
  
  
  
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  Risk factors: (a) age (usually over 60 years), (b) gender (female > male), (c) race (high Asian prevalence), (d) family history, (e) hypermetropia, (f) short axial length, (g) shallow anterior chamber dimensions, associated with a relatively forward lens position.

Diagnosis

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  Primary angle closure suspect (PACS): (a) shallow anterior chamber ( Fig. 11.7A ), (b) gonioscopy shows an ‘occludable angle’: ITC in three or more quadrants but no peripheral anterior synechiae (PAS), (c) narrow angle on dark-room anterior segment OCT ( Fig. 11.7B ), (d) normal IOP, discs and fields.

  
  

  
  

  
  

  

  
  

  
  

  Primary angle closure: (A) shallow anterior chamber, (B) very narrow angle on anterior segment OCT, (C) gonioscopic appearance on indentation showing PAS (arrow), (D) acute closure showing corneal oedema and a mid-dilated pupil.

  
  

  (From Salmon JF, Kanski’s Clinical Ophthalmology: A Systematic Approach , 9th edition. Oxford, UK: Elsevier; 2020.)

  
  
  
  
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  Primary angle closure (PAC): (a) gonioscopy shows three or more quadrants of ITC (b) raised IOP and/or PAS ( Fig. 11.7C ), (c) normal discs and fields.

  
  
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  Primary angle-closure glaucoma (PACG): (a) gonioscopy shows ITC in three or more quadrants, (b) glaucomatous optic neuropathy.

Clinical presentation

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  Acute congestive angle closure: acute onset of blurring and haloes, ocular pain and headache, sometimes malaise and gastrointestinal symptoms. (a) VA usually 6/60-HM, (b) IOP very high (50–80 mm Hg), (c) corneal oedema ( Fig. 11.7D ), (d) ciliary injection, (e) shallow anterior chamber, (f) unreactive mid-dilated vertically oval pupil, (g) fellow eye shows an occludable angle.

  
  
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  Resolved acute primary angle closure: (a) early signs (low IOP, Descemet membrane folds, optic nerve head congestion) ( Fig. 11.8A ), (b) late signs (iris atrophy, glaukomflecken, optic disc pallor) ( Fig. 11.8B ).

  
  

  
  

  
  

  

  
  

  
  

  Resolved acute primary angle closure: (A) Descemet membrane folds, (B) iris atrophy with irregular pupil.

  
  

  (From Salmon JF, Kanski’s Clinical Ophthalmology: A Systematic Approach , 9th edition. Oxford, UK: Elsevier; 2020.)

  
  
  
  
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  Subacute presentation: (a) intermittent ocular pain and headache, (b) intermittent IOP elevation, (c) occludable angle.

  
  
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  Chronic presentation: (a) asymptomatic although episodic mild blurring may be present, (b) PAS may be broad (‘creeping’) or discrete (‘sawtooth’), (c) optic nerve head appearance depends on the severity of the damage.

Treatment

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  PACS: prophylactic laser iridotomy ( Fig. 11.9A ). If significant ITC persists, options include: observation (most cases), laser iridoplasty ( Fig. 11.9B ) and lens extraction.

  
  

  
  

  
  

  

  
  

  
  

  Treatment: (A) laser peripheral iridotomy, (B) laser iridoplasty.

  
  

  (From Salmon JF, Kanski’s Clinical Ophthalmology: A Systematic Approach , 9th edition. Oxford, UK: Elsevier; 2020.)

  
  
  
  
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  PAC and PACG: (a) as for PACS, although subsequent medical treatment (as for POAG) is often required, or (b) lens extraction with IOL implantation should be considered in patients with PAC and IOP >29 mm Hg and in those with PACG.

  
  
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  Initial treatment of acute and subacute presentation: (a) intravenous acetazolamide 500 mg, (b) topical apraclonidine 1%, timolol 0.5%, prednisolone 1%, or dexamethasone 0.1% to the affected eye, (c) pilocarpine 2%–4% one drop to the affected eye, repeated after 30 min, with one drop of 1% as prophylaxis to the fellow eye; it is only effective once the IOP begins to fall, (d) place patient in a supine position.

  
  
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  Subsequent treatment of acute and subacute presentation: (a) pilocarpine 2% four times daily to the affected eye and 1% to the fellow eye, (b) ongoing treatment according to IOP with timolol 0.5% twice daily, apraclonidine 1% three times daily and oral acetazolamide 250 mg four times daily. Once the cornea is clear, bilateral laser iridotomy is performed and medical treatment tapered.

  
  
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  Options in unresponsive acute cases: (a) intravenous mannitol or oral glycerol, (b) corneal indentation, (c) laser iridotomy or iridoplasty (clear oedema with glycerol 50% first), (d) cyclodiode laser treatment, (e) paracentesis, (f) surgery (peripheral iridectomy, lens extraction, trabeculectomy).

Differential diagnosis of acute IOP elevation:

consider alternatives to angle closure, particularly if the fellow eye has an open angle.

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  Lens-induced angle closure: due to an intumescent or subluxated lens.

  
  
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  ‘Malignant glaucoma’: especially if intraocular surgery has recently taken place causing aqueous misdirection.

  
  
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  Other causes of secondary angle closure with or without pupillary block: (a) topiramate (epilepsy and migraine drug) causing ciliochoroidal effusion, (b) neovascular glaucoma sometimes presents acutely, (c) inflammation with an open angle, e.g. iridocyclitis/trabeculitis, glaucomatocyclitic crisis (Posner–Schlossman syndrome), (d) scleritis without angle closure, (e) pigment dispersion syndrome, (f) pseudoexfoliation syndrome, (g) orbital/retro-orbital lesions (e.g. inflammation, retrobulbar haemorrhage).

Pathogenesis:

grey-white fibrillary material is produced by abnormal basement membranes of ageing intraocular epithelial cells and deposited in structures including the trabeculum; particularly common in Scandinavia. Single nucleotide polymorphisms in the LOX ₁ gene on chromosome 15 predisposes to the condition.

Diagnosis

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  Cornea: pseudoexfoliation (PXF) material and pigment may be seen on the endothelium.

  
  
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  Iris: PXF on the pupillary margin and ‘moth-eaten’ sphincter atrophy.

  
  
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  Anterior lens surface: central disc and peripheral band of PXF, with a clear zone between ( Fig. 11. 10A ), which may be seen only with pupillary dilatation.

  
  

  
  

  
  

  

  
  

  
  

  Pseudoexfoliation syndrome: (A) pseudoexfoliation material on lens, more obvious on pupillary dilatation, (B) gonioscopy showing patchy hyperpigmentation and a Sampaolesi line.

  
  

  (From Salmon JF, Kanski’s Clinical Ophthalmology: A Systematic Approach , 9th edition. Oxford, UK: Elsevier; 2020.)

  
  
  
  
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  Gonioscopy: (a) trabecular hyperpigmentation and a band running on or anterior to the Schwalbe line (Sampaolesi line; Fig. 11.10B ); (b) dandruff-like PXF particles may be seen, (c) there is an increased risk of angle closure, probably due to zonular laxity.

  
  
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  Inner ear: high tone hearing loss.

Treatment:

observation at 12-monthly intervals to detect elevation of IOP.

Pathogenesis:

trabecular obstruction and damage by PXF material and pigment. The cumulative risk of glaucoma in eyes with PXF is approximately 5% at 5 years and 15% at 10 years. A patient with unilateral pseudoexfoliation glaucoma and only PXF in the fellow eye has a 50% 5-year risk of glaucoma in the fellow eye, but only a low risk if there is no PXF.

Diagnosis

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  Presentation: in 7th decade with chronic unilateral elevation of IOP. An acute elevation may occasionally occur.

  
  
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  Signs: PXF and glaucomatous optic neuropathy.

  
  
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  Prognosis: worse than in POAG because the IOP is often significantly elevated and may also exhibit great fluctuation. Severe damage may therefore develop relatively rapidly.

Treatment

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  Medical: same as for POAG but with a greater likelihood of requiring laser or surgery.

  
  
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  Laser trabeculoplasty: effective in the short term, but IOP may increase significantly at around two years post treatment.

  
  
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  Surgery: same success rate as in POAG.

  
  
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  Trabecular aspiration: performed at the same time as cataract surgery or trabeculectomy confers a short-term benefit.

Pathogenesis:

liberation of pigment granules from the iris pigment epithelium due to ‘reverse pupil block,’ with resultant posterior bowing of the iris and iridozonular touch ( Fig. 11.11A ). Pigment is deposited throughout the anterior segment. The condition primarily affects white individuals with myopia; males more than females.

Pigment dispersion syndrome: (A) UBM showing backward bowing of the iris, (B) Krukenberg spindle, (C) radial spoke-like iris transillumination defects, (D) heavily pigmented angle.

(From Salmon JF, Kanski’s Clinical Ophthalmology: A Systematic Approach , 9th edition. Oxford, UK: Elsevier; 2020.)

Diagnosis

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  Presentation: usually asymptomatic, although corneal oedema with blurring and haloes may occasionally occur in response to an IOP spike. In some patients, this may be precipitated by exercise.

  
  
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  Cornea: pigment deposition on the endothelium in a vertical spindle-shaped distribution (Krukenberg spindle; Fig. 11.11B ).

  
  
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  Anterior chamber: usually very deep.

  
  
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  Iris: radial slit-like transillumination defects ( Fig. 11.11C ) and fine surface pigment granules.

  
  
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  Gonioscopy: very wide angle with mid-peripheral iris concavity and homogeneous trabecular hyperpigmentation in all four quadrants ( Fig. 11.11D ). Pigment may also be seen on or anterior to Schwalbe line.

Treatment:

observation at 6- to 12-monthly intervals to detect elevation of IOP.

Pathogenesis:

approximately 15% of patients with pigment dispersion syndrome (PDS) develop OHT or chronic open-angle glaucoma after 15 years. Elevation of IOP appears to be caused by both pigmentary obstruction of the intertrabecular spaces and secondary damage to the trabeculum; men are affected twice as frequently as women.

Diagnosis

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  Presentation: in 3rd and 4th decades, usually with chronic glaucoma.

  
  
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  Signs: those of PDS, together with glaucomatous optic neuropathy. IOP may be unstable and asymmetric disease is common.

  
  
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  Differential diagnosis: (a) POAG with a heavily pigmented trabeculum, (b) pseudoexfoliation, (c) pseudophakic pigmentary glaucoma, (d) sequelae of uveitis, (e) subacute angle-closure glaucoma.

Treatment

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  Medical: similar to that of POAG, but monitor at 4-monthly intervals because the combination of high IOP and myopia can cause a rapid deterioration in vision.

  
  
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  Laser trabeculoplasty: often initially effective. Use the lowest laser settings and only treat 2 quadrants to prevent a spike in IOP.

  
  
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  Trabeculectomy: more commonly performed than in POAG.

Diagnosis

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  Tiny dilated capillary tufts or red spots at the pupillary margin ( Fig. 11.12A ). New vessels grow radially over the surface of the iris toward the angle.

  
  

  
  

  
  

  

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