Glaucoma Suspects

Many people who are at high risk of developing POAG currently do not manifest optic nerve or visual field damage. These people, generally referred to as POAG suspects, should be identified early and observed at regular intervals for possible progression to POAG. With the development of sophisticated nerve fiber layer

Table 10.4 AAO-Recommended Guidelines for Visual Field Testing

Target IOP

Progression

Duration of

Follow-up

Achieved

of Damage

Control

Interval

Yes

No

<6 months

6 to 18 months

Yes

No

>6 months

6 to 24 months

Yes

Yes

1 to 6 months

No

Yes/no

1 to 6 months

analyzers, eventually, it may be possible to detect glaucomatous damage prior to optic nerve or visual field changes.

The AAO uses several criteria to identify glaucoma suspects.79 These people can have an abnormal-appearing optic nerve suggestive of glaucoma as indicated by a large cup-to-disk ratio, narrowed neuroretinal rim tissue, asymmetric cupping, focal abnormalities of the neuroretinal rim (e.g., notching or hemorrhage), and abnormalities of the nerve fiber layer. Borderline visual fields and elevated IOP also identify glaucoma suspects. These people have normal open angles and no secondary cause for elevated IOP. Their risk for developing POAG can be further stratified by assessing the number of additional risk factors present and the degree of IOP elevation if present. People with definite evidence of optic nerve, nerve fiber layer, or visual field changes should be considered as having POAG.

As with diagnosed POAG patients, an adequate baseline evaluation of POAG suspects is essential. Individuals considered at high risk are those with elevated IOP, thin corneas, age greater than 50 years, African American or Hispanic ancestry, family history of glaucoma, and optic nerve findings consistent with early glauco-matous damage.

The OHTS9,15 is an excellent resource for managing glaucoma suspects with elevated IOP. In multivariate analysis, risk factors for development of glaucoma are increasing age, larger vertical or horizontal cup-to-disk ratio, higher IOP, greater pattern standard deviation, and thinner central corneal measurement. Clearly, extrapolating individual patient outcomes from data obtained from clinical trials can be difficult. Patients should be stratified according to their individual risk profiles. For example, a patient with an IOP less than 24 mm Hg and a corneal thickness greater than 588 mm has a 2% risk of glaucoma development over 6 years, whereas a patient with an IOP greater than 26 mm Hg and a corneal thickness less than 555 mm has a 36% risk of glaucoma development. A recently introduced risk calculator has been created using the OHTS data. This may prove helpful as a guide to determine the need for treatment in patients at risk of progression to glaucoma.39

The risk of glaucoma development combined with the potential benefits of early intervention versus the cost and risk of early treatment in a normally slowly progressive disease process should be carefully discussed with the patient. If the clinician feels the risk of glaucoma damage outweighs the downsides of early treatment, therapeutic intervention should be recommended.

If a high-risk glaucoma suspect is to be treated, the same protocol used in treating POAG should be followed. A target IOP should be set, although it is generally not as low as that in POAG because preexisting damage, if present, is not detectable. A 20% reduction in IOP is a reasonable initial target. Generally, only medical therapy is instituted in the absence of optic nerve damage unless IOP is extremely high; however, in select cases, trabeculoplasty may also be appropriate. As with POAG, follow-up is very important. AAO guidelines state that untreated low-risk glaucoma suspects with stable optic nerves and IOP should be observed every 6 to 24 months, with a complete eye examination and visual fields. Untreated high-risk glaucoma suspects with stable optic nerves and IOP should be observed every 3 to 12 months. Treated high-risk patients with controlled IOP should be seen every 3 to 12 months, after which visits can be slowly extended if optic nerve and visual field stability has been clearly documented. Treated high-risk patients with uncontrolled IOP should be seen at least every 4 months until the target IOP has been achieved.

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