The diagnostic criteria that leads me to suspect glaucoma as a possible diagnosis includes the examination of the optic nerve head and its retinal nerve fiber layer since it is fundamental to all aspects of glaucoma diagnosis and evaluation. All forms of glaucoma have in common a potentially progressive and characteristic optic neuropathy which is associated with visual field loss as damage progresses. Consequently, a reliable and reproducible visual field analysis is necessary as a representation of the patient’s functional status. Intraocular pressure (IOP) determination is important since the prevalence of glaucoma increases as the level of IOP increases. In spite of the relationship between the level of IOP and glaucoma, there is great interindividual variation in the susceptibility of the optic nerve to IOP- related damage. Suggesting that an IOP level of greater than 21-22 mmHg is an arbitrarily defined level and highlights the poor value of utilizing a specific IOP cutoff as a measure for screening and diagnosing glaucoma.
Other important risk factors associated with glaucoma are as follows:
- Older age
- Family history of glaucoma
- Ancestry / Race
- Thinner central corneal
- Lower corneal hysteresis (an assessment of the cornea’s ability to absorb and dissipate energy)
- Low ocular perfusion pressures
- Lower blood pressure
- Optic disc hemorrhage(s)
- Diabetes mellitus
- Genetic mutations (there is little value for routine genetic testing to diagnose or predict the development of glaucoma at the current time)
- Migraine headache
- Peripheral vasospam
- Reduction of estrogen production in post-menopausal women
- Obstructive sleep apnea
Testing for glaucoma is indicated when certain ocular, systemic, and general factors are found during periodic comprehensive eye examinations which thereby increase the risk and/or probability of glaucoma.
My methodology and evaluation of a glaucoma suspect may include, but is not limited to, the following:
- Visual acuity
- Pupil evaluation (Utilizing NPi – 100 Pupillometer)
- Blood pressure
- Biomicroscopy (Slit Lamp)
- Ultrasound Biomicroscopy (UBM to ascertain underlying cause(s) of any Angle Closure)
- IOP measurement (diurnal / asymmetry)
- Central corneal thickness (Pachymetry)
- Corneal hysteresis
- Optic nerve assessment (neuroretinal rim, optic disc size, cup-disc ratio)
- Nerve fiber layer assessment
- PERG and PhNR testing can be very useful, but are not substitutes for standard automated perimetry (SAP), nor are they substitutes for optical coherence tomography (OCT) imaging
- Fundus Photography (sterescopic optic nerve photos)
- Visual fields (before accepting VF defects as real, they must be confirmed on two consecutive exams (excluding the initial one) and ideally obtain 6 VF’s in 2 years to identify the rate of progression).
Why Are There So Many Diagnostic Exams for Glaucoma?
Diagnosing glaucoma is not always easy, and careful structural and functional evaluation of the optic nerve continues to be essential to diagnosis and treatment. The most important concern is protecting, preserving and optimizing your sight. Doctor Rouse looks at many factors before making decisions about your treatment. If your condition is particularly difficult to diagnose or treat, you may be referred for a second opinion.