Glaucoma

Glaucoma is a group of eye diseases that are characterized by progressive damage to the optic nerve resulting in impaired vision and sometimes blindness if left untreated (1,2)

The disease is charcterised by:

• visual field loss - arcuate scotomas, nasal steps, altitudinal scotomas, focal defects e.g. paracentral scotomas
• optic disc changes - localised or generalised thinning of the neuroretinal rim, enlargement of the optic cup and increased cup to disc ratio (1)
• nerve fiber layer defects (3)

Although in most cases there is an increase in intraocular pressure (IOP) which is sufficient to cause damage to the optic nerve head and changes in the visual field, the disease may be seen even in patients with normal IOP (5)

• the mean value for intraocular pressure is 15-16 mm Hg with a standard deviation of +/- 2.5. The upper limit of normal is considered to be 21 mm Hg.
• about 2% of adults have an intraocular pressure over 21 mmHg with no evidence of glaucoma (6)

Glaucoma can be described according to the:

• cause - as primary (without an underlying cause) or secondary (due to another eye or systemic condition, trauma, or by certain medication)
• anatomy of the anterior chamber angle of the eye – as either open angle glaucoma or angle closure glaucoma (3,4)
  • open-angle glaucoma
    • accounts for more than 90% of cases of glaucoma, and it occurs when fluid in the eye is unable to drain properly
    • most people with open-angle glaucoma are initially asymptomatic
    • as the disease progresses, patients can develop problems with peripheral vision and, sometimes, central vision, causing difficulty with reading, walking, and driving
  • chronic angle-closure glaucoma
    • characterized by slow, progressive obstruction of fluid drainage from the eye
    • patients can have periodic visual symptoms, but are often asymptomatic until the condition worsens, and then develop visual symptoms similar to open-angle glaucoma
  • acute angle-closure glaucoma
    • due to acute obstruction of fluid drainage from the eye, leading to blurry vision, halos around lights, eye pain, nausea, vomiting, and rapid vision loss
    • this type of glaucoma requires emergency treatment to decrease intraocular pressure and prevent rapid onset of blindness

Notes:

• the NICE committee agreed that the key outcome for adults with ocular hypertension (OHT) or chronic open angle glaucoma (COAG) was visual field progression that, in the long-term, could affect people's vision (2)
  • intraocular pressure (IOP) was considered to be a relevant surrogate outcome because lowering IOP can prevent the risk of optic nerve damage and sight loss
  • high-quality evidence showed that there is no meaningful difference between 360 degrees selective laser trabeculoplasty (SLT) and eye drops in achieving a target IOP, health-related quality of life, risk of total adverse events, and treatment adherence
  • highlighted that there are rare complications associated with SLT
    • while rare events were not highlighted in the evidence, corneal failure is possible after SLT procedures
  • in people who have first-line treatment with eye drops compared with first-line 360 degrees SLT, more people used eye drops and more people have more than 1 eye drop medication at 12 months
  • cost-effectiveness evidence showed that first-line treatment with 360 degrees SLT was more effective and less costly compared with eye drops, with at least 90% probability of being the more cost-effective option
  • based on this evidence and their clinical experience, the committee recommended 360 degrees SLT as first-line treatment for people with newly diagnosed OHT or newly diagnosed COAG
    • recommendation excludes cases associated with pigment dispersion syndrome
      • was because there was no evidence on the use of 360 degrees SLT in people with pigment dispersion syndrome and the committee agreed that eye drop treatment is more suitable for those people
• a review of a study (n=453) comparing outcomes in patients that underwent a trabeculectomy with patients treated with eye drops (7)
  • study showed that surgery was associated with lower intraocular pressure and that 17% of eyedrop treated patients needed surgery within 2 years
  • study supports current NICE Guidance that trabeculectomy should be viewed as a first treatment for people with advanced glaucoma

Reference:

• (1) Burr JM et al. The clinical effectiveness and cost-effectiveness of screening for open angle glaucoma: a systematic review and economic evaluation. Health Technol Assess. 2007;11(41):iii-iv, ix-x, 1-190
• (2) NICE (January 2022).Glaucoma: diagnosis and management
• (4) Voelker R. What Is Glaucoma? JAMA. 2023;330(16):1594. doi:10.1001/jama.2023.16311
• (3) Americal Optometric Association (AAO) 2010. Optometric clinical practice guideline. Care of the patient with open angle glaucoma
• (5) Liesegang TJ. Glaucoma: changing concepts and future directions. Mayo Clin Proc. 1996;71(7):689-94
• (6) GP magazine (August 2nd 2004):33-4s
• (7) King AJ, and others. Primary trabeculectomy versus primary glaucoma eye drops for newly diagnosed advanced glaucoma: TAGS RCT. Health Technology Assessment 2021;25:72