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Glaucoma

Editor: Shane J. Havens Updated: 3/16/2024 3:47:32 AM

Introduction

Glaucoma is a complex eye condition characterized by elevated intraocular pressure (IOP) that may progress to vision loss over time. Glaucoma is the second leading cause of permanent blindness in the United States and occurs most often in older adults.[1] Glaucoma can be categorized into either primary or secondary types and further into open-angle or closed-angle variants within each type of glaucoma. Adult glaucoma includes primary open-angle glaucoma (POAG) and angle-closure glaucoma, as well as secondary open and angle-closure glaucoma,[2][3] with a specific focus on the most prevalent type, POAG.[4][5] 

Glaucoma is an acquired loss of retinal ganglion cells and axons within the optic nerve or optic neuropathy that results in a characteristic optic nerve head appearance and a corresponding progressive loss of vision.[6] This unique pattern of peripheral vision loss serves as a distinguishing feature from other types of vision impairment.[7] 

Patients with POAG are often asymptomatic until significant optic nerve damage occurs unless early signs of glaucoma are identified during routine eye examinations.[8] On the other hand, acute angle-closure glaucoma can develop suddenly and lead to a rapid decline in vision, accompanied by symptoms such as corneal edema, eye pain, headache, nausea, and emesis.[9][10] Secondary glaucoma often arises due to a previous eye injury or underlying medical conditions, resulting in elevated IOP and subsequent optic neuropathy. This category encompasses various subtypes, including congenital, pigmentary, neovascular, exfoliative, traumatic, and uveitic glaucoma.[11] Normal or low-tension type of glaucoma presents as an optic neuropathy with glaucomatous visual loss despite normal or unremarkable IOP readings.[12]

Although congenital, infantile, and developmental glaucoma, along with a juvenile variant of POAG, primarily affect younger individuals, most types of glaucoma are commonly diagnosed in individuals aged 40 and older. While IOP is often associated with glaucoma, a direct causal relationship has not been definitively established. Researchers are investigating genetic and environmental factors contributing to glaucoma development. Evidence from studies involving monozygotic twin pairs, who exhibit a higher concordance rate compared to dizygotic pairs, suggests that environmental factors also have a significant role in the disease's development.[13] 

Although the available treatments cannot cure existing optic nerve damage or reverse visual field loss, they can help control the disease progression through medication, laser treatment, or incisional glaucoma surgeries to prevent further vision loss. All therapeutic interventions are focused on lowering IOP and minimizing the impact of this vision-threatening condition. This approach aims to prevent the onset of glaucoma in patients with risk factors and to manage the condition effectively to limit its progression in affected individuals.

Etiology

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Etiology

The exact etiology of glaucoma is unknown, but a clear correlation with elevated eye pressure exists in most cases. High IOP is the primary risk factor for developing glaucoma and for the progression of the disease, and it is also the sole factor that current treatments can effectively address.[14]

Primary Open-Angle Glaucoma

POAG typically manifests as slow, painless damage to the optic nerve due to an ineffective drainage system in the eye. In glaucoma, the resistance to drainage of aqueous humor most commonly starts at the inner wall of Schlemm canal at the juxtacanalicular trabecular meshwork. This decreased outflow facility or increased resistance to aqueous outflow results in a gradual rise in IOP, leading to characteristic damage patterns in the visual field and the optic nerve ganglion cell nerve fiber layer.[15] Recent studies have highlighted that elevated IOP can also reduce blood flow to the optic nerve fibers, resulting in subtle ischemic damage (see Image. Glaucomatous Optic Nerve Head Showing Inferotemporal Retinal Nerve Fiber Layer Defect).[16]

POAG patients often have elevated IOP readings correlating with characteristic optic nerve damage and visual field defect patterns (see Image. Glaucoma Visual Field Changes in the Left Eye). As the disease progresses, a slow loss of peripheral vision in one or typically both eyes eventually leads to loss of central vision. Because of this loss pattern, affected persons do not notice a change in their vision until their loss is advanced and affects the central vision, in which case damage is permanent and irreversible.[7] 

Glaucoma can manifest at different ages, with the age of onset often characterizing its presentation. Although POAG is typically associated with adulthood, it can also affect younger individuals and children, suggesting a significant genetic component. Primary congenital glaucoma is diagnosed in newborns aged up to 1 month, often suspected when there is eye enlargement at birth.[17] Infantile glaucoma affects individuals between the ages of 1 and 36 months,[18] while juvenile glaucoma is used to indicate individuals diagnosed with glaucoma between the ages of 3 and 40.[19] Juvenile open-angle glaucoma shares similarities with POAG in terms of IOP leading to optic nerve damage, but it occurs in a younger age group with higher IOP levels and potentially more severe visual field defects.[20]

Low-Tension or Normal-Tension Glaucoma

This type of glaucoma resembles POAG in terms of characteristic optic disc cupping and peripheral visual-field loss findings.[16] However, what sets it apart is that IOP readings are consistently normal, typically measuring less than 21 mmHg.[12] Theories suggest that patients with this type of glaucoma may have an optic nerve that is abnormally sensitive to pressure or may experience intermittent ischemic changes due to atherosclerosis or vascular insufficiency. These patients often exhibit a higher prevalence of migraines, Raynaud phenomenon, autoimmune diseases, ischemic vascular diseases, and coagulopathies. This observation may suggest the involvement of a vascular autoregulatory defect in the pathogenesis of the disease.[21][22][23][24] In addition, these patients tend to have a greater frequency of nerve fiber layer hemorrhages and a neuroretinal rim that is thinner inferiorly and inferotemporal than those with POAG. Visual field defects in this type of glaucoma are typically more focal, deeper, and closer to fixation rather than following the classic arcuate scotoma pattern seen in open-angle glaucoma.[25]

Angle-Closure Glaucoma

Angle-closure glaucoma is classified based on ocular anatomy and can manifest as a medical emergency in the acute setting or as a chronic condition.[26] In the acute form, this type of glaucoma occurs when the eye's drainage system is abruptly blocked due to the closure of the angle formed between the cornea and the iris.[27] Typically, this blockage arises from age-related lens thickening, leading to a gradual increase in a relative pupillary block that pushes the iris anteriorly. This anteriorly displaced iris, coupled with a natural anatomical variation such as a smaller angle seen in hypermetropia or specific ethnic groups, predisposes easier blockage of the outflow tract.[28]

A pupillary block is considered the underlying cause in the majority of cases.[29] When sudden pupil dilation occurs due to certain stimuli, darkness, or drugs, the iris is thick enough in its contracted state or anteriorly displaced by pupillary block to block fluid drainage via the trabecular meshwork. The pressure rapidly increases within the eye. This rapid change in IOP can cause central and/or peripheral vision loss within a few days of onset without intervention and very high IOP. A significantly elevated IOP and acute angle closure can lead to complications such as retinal vascular occlusion, ischemic optic neuropathy, or glaucomatous optic nerve damage. However, it is important to note that only about 10% of glaucoma cases fall into the acute angle-closure type category.[30]

Angle-closure glaucoma can also occur as a secondary condition due to various causes. Examples include lens subluxation in Marfan syndrome,[31] lens dislocation,[32] and lens-induced glaucoma.[33] The displacement of the lens into the pupil or anterior chamber can lead to an acute pupillary block.[34] Plateau iris configuration can also cause an acute pupillary block and chronic angle closure, attributed to elongated or anteriorly positioned ciliary processes pushing the iris edges forward.[35][36] In iridocorneal endothelial syndrome, irregular corneal endothelium migration onto the trabecular meshwork and peripheral iris can lead to high peripheral anterior synechiae, closing the angle and hindering outflow.[37][38]

Neovascularization can cause angle closure in neovascular glaucoma by forming a fibrovascular membrane that flattens and displaces the iris anteriorly. This process, along with new vessel formation in the iris and angle in rubeosis iridis, can lead to total synechial closure of the angle.[39] The most common etiologies of neovascular glaucoma are central retinal or branch retinal vein occlusion, proliferative diabetic retinopathy, and ocular ischemic syndrome.[40] Angle-closure glaucoma can also occur post-ophthalmic surgery due to factors such as ciliary body edema, scleral buckle placement, fibrin deposition, gas, or silicone oil used in retinal surgery.[41] Additionally, sulfa drugs such as topiramate can induce angle closure by causing ciliochoroidal effusion, which compresses the lens-iris diaphragm and anteriorly displaces it, resulting in angle closure.[42]

Secondary Open-Angle Glaucoma

Secondary open-angle glaucoma can result from various factors such as eye injury, eye disease, and occasionally eye surgery. These conditions can elevate IOP, leading to optic nerve damage and functional defects similar to those seen in primary open-angle glaucoma. One notable mechanism of secondary open-angle glaucoma arises from laser surgery, which can trigger pigment release, inflammatory cell accumulation, debris deposition, and mechanical deformation. These factors can collectively obstruct the trabecular meshwork, contributing to elevated IOP levels (see Image. Hypermature Morgagnian Cataract).

Pseudoexfoliation Glaucoma 

Pseudoexfoliation syndrome (PEX) is a type of glaucoma characterized by the presence of flaky material within the anterior chamber of the eye that collects in the angle. This material can clog the trabecular meshwork, leading to increased resistance to aqueous outflow and elevated IOP.[43] PEX syndrome is a systemic disorder affecting the extracellular matrix, with ocular manifestations such as white deposits on the pupil's margin and the anterior capsule of the lens, which can occur in one or both eyes.[44] This secondary form of open-angle glaucoma poses additional risks during cataract surgery, including zonular dialysis, capsular bag rupture, and vitreous loss. These risks are attributed to eyes with unstable lens zonules and poor pupillary dilation associated with PEX syndrome.[45]

Individuals with pigment dispersion syndrome (PDS) are at an increased risk of elevated IOP.[46] Ocular manifestations of PDS share similarities with PEX syndrome, except that in PDS, the debris consists of pigment granules from the posterior iris surface. These granules can detach and obstruct the trabecular meshwork, especially in myopic or near-sighted eyes, due to contact with the peripheral lens capsule and zonules.[47] Features of PDS include anterior chamber pigment dispersion, spoke-like iris defects on trans-illumination, central corneal endothelial deposits (known as the Krukenberg spindle), and increased pigmentation in the iridocorneal angle.[48] Some individuals may progress to pigment dispersion glaucoma or pigmentary glaucoma characterized by elevated IOP levels, glaucomatous optic neuropathy, and/or visual field defects.[49]

Steroid-Induced Glaucoma

Steroid-induced glaucoma can occur in susceptible individuals undergoing cortisone therapy due to glucocorticoid's effects. Glucocorticoids can upregulate receptors on cells within the trabecular meshwork, leading to increased outflow resistance. Additionally, the accumulation of glycosaminoglycans in the meshwork pores contributes to this resistance.[50] Steroids can also suppress phagocytic activity, which decreases debris deposition removal from the meshwork and stimulates the expression of extracellular matrix proteins.[51]

Another form of secondary glaucoma is a carotid-cavernous fistula, characterized by an abnormal connection between the cavernous sinus and the carotid artery.[52] This condition causes arterial flow and venous engorgement, leading to elevated episcleral venous pressure. The consequent dilation of retinal veins and swelling of the optic disc can cause concurrent damage to optic nerve fibers.[53]

Secondary glaucoma can also result from posttraumatic or postoperative conditions, elevated episcleral venous pressure, and tumor-related factors.[54] Ellingson syndrome, also known as uveitis-glaucoma-hyphema syndrome, is a complication that can cause elevated IOP following the implantation of an intraocular lens. This elevation in IOP can occur either immediately after surgery or manifest years later as a complication.[55]

Glaucomatocyclitic crisis, also known as Posner-Schlossman syndrome, presents with recurrent acute episodes of elevated IOP that typically resolve spontaneously without treatment. However, repeated episodes have been associated with glaucomatous damage to the optic nerve over time (see Image. Advanced Glaucomatous Damage to the Optic Nerve).[56][57][58]

Epidemiology

Glaucoma is a condition marked by the gradual loss of peripheral vision and irreversible damage to the optic nerve and retinal ganglion cells, making it a significant public health concern. Its multifactorial etiology involves anatomical, genetic, vascular, and immune factors. Glaucoma is a fundamental public health concern, considering that, after cataracts, it is the second cause of irreversible blindness. Currently affecting over 60 million individuals worldwide, this number is expected to surpass 110 million by 2040.[59] POAG is the most prevalent type, affecting approximately 2% to 4% of individuals aged 40 and older and around 10% of those aged 75 and older.[60]

The African population exhibits the highest prevalence of open-angle glaucoma. Individuals of African descent face up to a 15-fold increased risk of blindness from open-angle glaucoma compared to other population groups.[7] On the other hand, the Inuit population has the highest prevalence of angle-closure glaucoma. Women are more commonly affected than men in this group, along with individuals of Asian descent, who generally have a shallower anterior chamber, contributing to the higher rates of angle closure.[61] The normal-tension type of glaucoma is most prevalent in Japanese populations.

Age represents a significant risk factor in the progressive loss of retinal ganglion cells across all types of glaucoma. Additionally, other risk factors for developing glaucoma include a family history of the condition in a primary relative (mother, father, brother, sister, or children) and medical conditions such as diabetes, high blood pressure, and heart disease. Eye trauma, anatomical differences such as thinner corneas, a history of retinal detachment, eye tumors or inflammation, and prolonged use of corticosteroids are also associated with an increased risk of glaucoma.[62]

Pathophysiology

The optic nerve carries over 1 million nerve fibers that transmit visual signals from the photoreceptors in the outer retina to the visual processing areas of the occipital lobe. Damage to the retinal nerve fiber layer occurs in various types of glaucoma. Aqueous humor, the fluid in the anterior chamber of the eye, is crucial in maintaining intraocular pressure and nourishing ocular tissues. Aqueous humor is produced by the non-pigmented epithelial cells of the ciliary body processes and follows a circadian production pattern.[63] Aqueous humor drains continuously through the pupil, then via the trabecular meshwork anterior to the scleral spur and iris insertion, into Schlemm canal, and finally into the episcleral venous system, larger orbital venous system, and systemic venous circulation. The trabecular meshwork consists of multiple layers of connective tissue and the endothelium of Schlemm canal, forming the primary drainage pathway for aqueous humor.[64] 

The conventional outflow pathway regulates fluid drainage from the eye in a pressure-dependent manner, acting as a one-way valve for aqueous humor drainage. In contrast, the uveoscleral outflow pathway allows pressure-independent passage of aqueous humor through the ciliary muscle and iris root into the supraciliary and suprachoroidal space.[65] This pathway is believed to experience reduced outflow with age. Over time, there is a decline in aqueous humor drainage through the trabecular meshwork, while the production of aqueous humor by the ciliary body decreases slightly. This imbalance between outflow and aqueous production leads to elevated average IOP and larger diurnal fluctuations in IOP, which are common features in patients with glaucoma.[66] 

Prolonged elevation of IOP leads to the death and atrophy of nerve fibers, resulting in a "cupped" or curved appearance of the optic nerve head observed during fundoscopy. [67] The normal range of IOP is approximately 16±3 mmHg, with values typically falling between 12 and 21 mmHg.[68] However, IOP fluctuates throughout the day due to various factors including heart rate, respiration, exercise, hydration status, systemic medications, time of day, alcohol intake, patient posture, and use of topical medications.

Elevated pressure readings during screening, surpassing 21 mmHg, indicate pressures beyond normal physiological levels and raise concerns about potential future damage to the optic nerve due to glaucoma. However, it is challenging to determine if patients experience transient spikes in pressure during the day, leading to damage that remains undetected during screening. Consequently, elevated screening pressure serves only as a risk factor for developing glaucoma and is not sufficient for a glaucoma diagnosis. Continuous monitoring of IOP throughout the day (diurnal pressure monitoring) may aid in identifying individuals at risk in this patient population.[69]

Patients diagnosed with normal-tension glaucoma often exhibit systemic vascular conditions such as the Raynaud phenomenon, migraines, sleep apnea, carotid artery disease, and significant nocturnal blood pressure fluctuations.[70][71] In acute angle-closure glaucoma, the trabecular meshwork drainage pathway becomes obstructed due to the iris being pushed forward from pressure, such as an anteriorly displaced lens, or by fibrous tissue pulling the iris forward. The most common cause is a pupillary block, where the iris dilates to a mid-position, bows anteriorly upon contact with the lens, and obstructs the trabecular meshwork, thereby impeding aqueous outflow. Secondary glaucoma, as mentioned earlier, can arise from various causes such as surgery or neovascularization, leading to blockage of the outflow tracts and subsequent elevation of IOP, potentially resulting in glaucomatous optic nerve damage if left untreated.

History and Physical

Many patients with glaucoma, especially early in the disease, are unaware they have this condition until it is detected during a routine eye examination. Numerous meta-analyses and systematic reviews have indicated that the prevalence of undetected glaucoma in adults exceeds 50% globally, with higher rates observed in Asia and Africa.[72] Individuals typically experience a gradual loss of peripheral vision while retaining central vision until the disease progresses significantly. This can manifest as a classic arcuate pattern on Humphrey visual field testing. During a comprehensive eye examination, optic nerves may exhibit a focally notched neural retinal rim or diffuse cup enlargement, a reduction in peripheral vision detected through visual field testing, and, although not necessary for diagnosis, an elevated IOP reading on tonometry. Usually, changes are observed bilaterally but may progress asymmetrically, leading to an asymmetric optic nerve cup. A cup-to-disc ratio greater than 0.5 is often associated with glaucoma, with initial loss typically observed in the inferotemporal and superotemporal poles of the optic disc (see Image. Optic Nerve Cup-to-Disc Ratio of 0.75).[73]

Patients with normal-tension glaucoma will typically be asymptomatic and have an IOP of less than 21 mmHg, making it challenging to detect and often leading to underdiagnosis due to the normal IOP values. Slit-lamp examination reveals changes in the optic disc, such as an increased cup-to-disc ratio, along with possible disc hemorrhage in the nerve fiber layer.[74] Patients may also have a medical history that includes vasospasm, coagulopathies, nocturnal hypotension, autoimmune diseases, vascular diseases, thyroid dysfunction, or sleep apnea.

In acute angle-closure glaucoma, patients usually experience sudden severe ocular pain, redness, blurry vision or decreased visual acuity, headache, nausea, and vomiting, as well as may report seeing halos of light. On examination, patients have an unresponsive mid-dilated pupil and a firm feeling of eyeball upon palpation. These attacks are often triggered by pupillary dilation from weak mydriatic or dilating drops. IOP is typically significantly elevated and ranges from 30 to 50 mmHg. Predisposing risk factors for acute angle-closure glaucoma include elevated hypermetropia, an angle between the iris and the cornea around 20° or less observed during gonioscopy, and/or an anterior chamber depth of less than 2.5 mm.[75] Patients with these reports should be advised to avoid dilating medications to reduce their risk of experiencing an acute attack. On slit-lamp examination, signs such as a large optic cup with narrowing of the neuroretinal rim and splinter hemorrhages may also be present.[76] 

Patients with secondary glaucoma typically have a history of recent ophthalmic procedures, trauma, or underlying health conditions causing neovascularization, such as diabetic retinopathy or previous retinal vascular occlusions. Patients may sometimes not recall a specific precipitating factor, but subtle clinical examination findings can point to the cause of elevated IOP. Examination findings may include exfoliative material on the anterior lens capsule, pigment deposition on the corneal endothelial cells, flare in the anterior chamber indicative of uveitis, abnormal blood vessels on the iris, or signs of trauma, depending on the underlying etiology.

Evaluation

Assessment includes a fundoscopic examination, visual field testing, tonometry, optical coherence tomography (OCT), and gonioscopy. Of these, IOP is the greatest risk factor, thereby making tonometry of utmost importance.[77] Goldmann applanation tonometry is the gold standard for patients with risk factors, elevated IOP, and glaucoma, although several other types of tonometers are available.[78][79][80] Alternative tonometers can be considered when Goldmann applanation tonometry is impractical, including bedridden patients, noncollaborative individuals, children, or those allergic to anesthetic drops.[81][82]

Additional helpful tests in glaucoma evaluation include assessing visual acuity to determine any impact on vision, pachymetry to measure corneal thickness, and retinal scans to monitor progressive changes in the retinal nerve fiber layer. Regular visual field testing using full-threshold strategies is crucial for individuals with risk factors, ocular hypertension, and those undergoing glaucoma treatment.[83][84][85] OCT is valuable for monitoring morphological changes in the optic nerve and retinal nerve fiber layer, especially in patients with ocular hypertension and early-to-moderate glaucoma.[86]

Glaucoma diagnosis relies on identifying progressive optic neuropathy and/or visual field defects, often in conjunction with elevated IOP. Ocular hypertension is diagnosed in individuals with IOP levels exceeding 21 mmHg without signs of glaucomatous optic neuropathy or functional visual field defects. Research indicates that around 20% of people with ocular hypertension may progress to glaucoma, highlighting the importance of regular testing, tonometry, and comprehensive eye examinations to initiate appropriate treatment aimed at reducing IOP in the presence of initial glaucomatous damage.[87] 

A single gold standard test does not exist for diagnosing glaucoma. Typically, glaucoma is diagnosed during routine eye examinations, as the disease is often asymptomatic without noticeable vision loss. Clinicians rely on recognizing the characteristic appearance of the optic nerve, assessing risk factors, and interpreting ancillary test results to establish an accurate diagnosis and stage of glaucoma.[88] Currently, the American Academy of Ophthalmology recommends routine comprehensive eye examinations for individuals with glaucoma risk factors, with the examination frequency tailored to factors such as age, race, family history, and specific risk factors.[89]

Treatment / Management

Managing glaucoma involves personalized strategies based on the type and severity of the condition. Available treatments cannot reverse vision loss; they aim to lower IOP, a key risk factor, to prevent further damage and vision loss. Therapeutic options such as eye drops, laser procedures, and surgeries are focused on reducing IOP. Monitoring disease progression involves using tools like tonometry, visual field tests, OCT, and vision loss mapping.

Open-angle glaucoma is typically managed initially with medications aimed at reducing eye pressure. Common medication classes include prostaglandin analogs, β-blockers, carbonic anhydrase inhibitors, α-2 agonists, miotic agents, and more recently, Rho-kinase inhibitors and nitric oxide-donating medications.[90][91] Laser trabeculoplasty, such as argon laser trabeculoplasty, selective laser trabeculoplasty, and multipulse laser trabeculoplasty, may also be considered in certain cases. However, the benefits of lowering IOP with laser trabeculoplasty often last several months, and retreatments are commonly necessary.[92] (A1)

If medical and/or laser management is unsuccessful, procedures such as trabeculectomy, deep sclerectomy, canaloplasty, insertion of a drainage valve/tube shunt, and laser treatment to the ciliary body to reduce aqueous production can help achieve better control of IOP.[93][94][95] Minimally invasive glaucoma surgery (MIGS) is an emerging option for individuals with mild-to-moderate glaucoma.[96] Compared to traditional trabeculectomy and tube shunts, MIGS offers a more favorable safety profile, quicker recovery time, and effective reduction of IOP to the mid-high teens. Studies also indicate that MIGS placement can decrease the number of pressure-lowering medications needed to maintain target IOP levels.[97](A1)

Normal-tension glaucoma can be managed with medications to reduce IOP and address any underlying medical conditions. Treatment options include prostaglandin analogs, α-2 agonists, carbonic anhydrase inhibitors, and miotics. The use of β-blockers is debated due to concerns about reduced optic nerve head perfusion, particularly regarding the potential exacerbation of the early morning nadir in blood pressure. If medical therapy proves ineffective, laser trabeculoplasty or filtration surgery may be necessary, especially in cases of progressive vision loss. The collaborative normal-tension glaucoma study demonstrated that patients with this condition can slow or stabilize their field loss after achieving a 30% reduction in IOP.[98](B3)

Angle-closure glaucoma is considered a medical emergency due to the potential for elevated pressures leading to glaucomatous optic nerve damage, ischemic nerve damage, or retinal vascular occlusion. Patients can take medications to reduce eye pressure as quickly as possible but usually require a laser procedure called laser peripheral iridotomy. This procedure involves creating a small hole in the iris to alleviate pupillary blockage. By equalizing the pressure gradient between the posterior and anterior chambers, laser iridotomy resolves the iris bombe and opens up the drainage angle in the anterior chamber, relieving the condition. The peripheral iris can be flattened with laser iridoplasty and, less commonly, with laser pupilloplasty.

A decrease in IOP does not always indicate that the angle has reopened. Ischemic damage to the ciliary body during an attack can reduce aqueous humor production for several weeks. Therefore, it is crucial to perform a follow-up gonioscopy to confirm angle patency. This evaluation also helps assess the percentage of the angle with peripheral anterior synechia from acute or prior subacute attacks. After resolving the acute crisis, patients are at a high risk of experiencing an attack in the contralateral eye. Therefore, they should undergo gonioscopy to assess the angle and consider prophylactic iridotomy in the other eye if the angle is narrow.[99] Treatment for secondary glaucoma should focus on addressing the underlying cause along with the possible inclusion of medications to reduce IOP.[100]

Differential Diagnosis

When diagnosing POAG, it is crucial to rule out other conditions that can cause optic neuropathy. Differential diagnoses to consider include previous ischemic optic neuropathy, optic atrophy, and compressive non-glaucomatous optic neuropathy, as they can exhibit similar visual field loss patterns and, in some cases, lead to "pseudo-cupping" of the optic nerve.[101] If elevated IOP or characteristic glaucomatous optic nerve changes are observed, performing a gonioscopy is essential to assess the anterior chamber's status (open, narrow, or closed). Moreover, clinicians should be vigilant for subtle signs of various secondary glaucomas, review the patient's medication history for potential idiosyncratic drug reactions or steroid responses, and gather a comprehensive history of prior ocular trauma and surgeries.

With an acute presentation resembling acute angle-closure glaucoma, clinicians should also consider other potential diagnoses such as iritis, traumatic hyphema, conjunctivitis, episcleritis, migraine, cluster headache, subconjunctival hemorrhage, corneal abrasion, endophthalmitis, orbital compartment syndrome, corneal ulcer, periorbital infections, and infectious keratitis. A thorough history-taking and detailed slit-lamp examination are crucial for narrowing down the differentials and arranging appropriate examinations or referrals as needed.[102][103][104]

Prognosis

Glaucoma is not a benign disorder, and if left untreated, it can lead to permanent vision loss. The higher the pressure and the duration of elevated IOP, the greater the risk of damaging the optic nerve. Timely diagnosis plays a critical role in mitigating glaucomatous damage, and early intervention is crucial in preventing and slowing down vision loss progression. Effective treatment, especially in maintaining low IOP levels, can often lead to positive outcomes, preserving visual field integrity and halting disease advancement.

Complications

Complications of glaucoma include visual field loss and can lead to eventual complete blindness, with a progression to no light perception vision in the affected eye.[105]

Deterrence and Patient Education

Standard screening during a complete eye examination includes checking the IOP of both eyes. Alongside tonometry, periodic eye examinations should encompass a thorough anterior segment evaluation and a fundoscopic exam, with special attention to the optic nerve. These initial screening tests are crucial for identifying glaucoma suspects early in the disease course. High-risk glaucoma suspects require further diagnostic testing such as visual field examination, OCT, pachymetry, and gonioscopy to confirm the diagnosis.

Patients should be educated about the causes, risk factors, and treatment for glaucoma. They should understand that most cases of glaucoma result in slow, progressive vision loss that often goes unnoticed until a significant portion of the visual field is affected. Therefore, regular eye exams are highly recommended to identify high-risk patients promptly and prevent irreversible vision loss.

Enhancing Healthcare Team Outcomes

Glaucoma represents a chronic and severe condition that may lead to irreversible vision loss if detected late in its progression. Effective management of the condition involves an interprofessional team focused on addressing patients' visual health concerns. A crucial aspect of treatment lies in patient education. Pharmacists should emphasize the importance of medication compliance and the necessity of regular follow-ups with the eye specialist. Ophthalmic technicians must collaborate closely with clinicians to oversee scheduled visual field and OCT assessments. Ophthalmic nurses are responsible for monitoring IOP and communicating these findings promptly to the ophthalmologist for further evaluation and management. This collaborative approach ensures comprehensive care and better outcomes for patients with glaucoma.

Regular eye appointments and compliance with medication are vital to lessening disease progression in glaucoma patients. Given its hereditary nature, educating family members about the increased risk of developing glaucoma is important, prompting them to undergo regular screenings for early detection. Notably, healthcare team members must consult the ophthalmologist before making any changes to medication dosage or frequency. Effective communication among healthcare providers is essential to reduce the morbidity associated with glaucoma.[106]

Media


(Click Image to Enlarge)
<p>Glaucomatous Optic Nerve Head Showing Inferotemporal Retinal Nerve Fiber Layer Defect

Glaucomatous Optic Nerve Head Showing Inferotemporal Retinal Nerve Fiber Layer Defect. Increased intraocular pressure can result in reduced blood supply to the optic nerve fibers, resulting in subtle ischemic injury.


Contributed by K Tripathy, MD


(Click Image to Enlarge)
<p>Glaucomatous Visual Field Changes in the Left Eye

Glaucomatous Visual Field Changes in the Left Eye. This image displays the results of a visual field test indicating characteristic changes associated with glaucoma in the left eye, as observed on perimetry.


Contributed by S Shah, MBBS


(Click Image to Enlarge)
<p>Optic Nerve Cup-to-Disc Ratio of 0

Optic Nerve Cup-to-Disc Ratio of 0.75. A cup-to-disc ratio greater than 0.5 is often associated with glaucoma, and initial loss is typically observed in the inferotemporal and superotemporal poles of the optic disc.


Contributed by AS Huang, MD


(Click Image to Enlarge)
<p>Hypermature Morgagnian Cataract

Hypermature Morgagnian Cataract.  This image captures the outcome of treatment for an older male patient who initially presented with severe corneal edema, congestion, and elevated intraocular pressure. Following the administration of antiglaucoma medications and topical steroids, a remarkable reduction in corneal edema was observed, exposing a hypermature Morgagnian cataract.


Sridhar U. Cornea Illustrated: A Guide to Clinical Diagnosis. Kolkata, West Bengal, India: New Central Book Agency; 2017.


(Click Image to Enlarge)
<p>Advanced Glaucomatous Damage to the Optic Nerve

Advanced Glaucomatous Damage to the Optic Nerve. This image illustrates the severe and advanced glaucomatous damage to the optic nerve observed in a patient with high myopia.


Contributed by K Tripathy, MD

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