What should you do when faced with ocular hypertension?

Ocular hypertension (OHT) patients pre-sent with an IOP greater than 21 mmHg in one or both eyes with no clinical evidence of pathology, such as VF defects, that explain the high IOP.

The decision to treat or delay treatment is not an easy one. The O.D. should generate — in his mind, or through a “risk calculator” (for example: http://bit.ly/2nX9IbF ) — the degree of risk in converting to primary open-angle glaucoma (POAG). The risk profile helps to create consistency for the O.D. regarding treatment recommendations. In general, the greater the check marks on the risk profile, the more likely treatment should be initiated.

The Ocular Hypertension Treatment Study (OHTS) provides a template to help O.D.s assess the risk of conversion. Here’s a look at this template, clinical tests that can aid in determining risk and a patient case.

TEMPLATE

1. Age. The older a patient, the greater the risk of conversion.
2. Central corneal thickness. If it’s less than 555 μm, the patient has a 3.4% annual increased risk of converting to POAG.
3. IOP. The higher the IOP, the greater the risk of conversion.
4. Pattern standard deviation. The higher its value, the greater the risk of conversion.
5. Race. Glaucoma is the No. 1 cause of blindness among African Americans.
6. Vertical cup-to-disc ratio. If higher than 0.50, there is a greater risk of developing POAG.
7. Lack of intervention. A study patient with an IOP of 24 mmHg or higher who did not obtain treatment had a 9.5% overall risk of developing glaucoma through a five-year period vs. 4.4% of study patients who received treatment.
8. IOP and CCT connection. A total of 36% of study patients with IOPs greater than 25.75 mmHg and corneas 555 μm or thinner developed glaucoma vs. 2% of patients with IOPs of 23.75 mmHg or below and corneas thicker than 588 μm.

CLINICAL TESTS

• Corneal hysteresis (CH). This test reveals the ability of the cornea to absorb and dissipate energy. CH is reflective of overall ocular tissue properties and associated with optic nerve head changes. The average CH in normal eyes in the United States is 10.5 mmHg. A 2018 prospective longitudinal study, published in the American Journal of Ophthalmology, followed 287 glaucoma suspect eyes for an average of 3.9 years. The study revealed 54 (19% of) eyes developed a repeatable VF defect during follow-up. Of those that developed a VF defect, the baseline CH measurement was significantly lower than those who did not (9.5 +/- 1.5 mmHg vs. 10.2 +/- 10.2). Each 1 mmHg lower CH was associated with an increase of 21% in glaucoma development risk during the follow-up.
• PERG. This shows retinal ganglion cell function. Damage to them has been shown to precede optic nerve head and retinal nerve fiber layer (RNFL) structural changes. OHT patients who have abnormal PERG amplitudes have a higher risk and rate of RNFL thinning vs. those who do not.

PATIENT CASE

A 61-year-old, Caucasian female has an IOP of 27 mmHg, a CCT of 530 μm, a vertical cup-to-disc ratio of 0.65, normal VF, normal RNFL on OCT, open angles with gonioscopy, a CH of 8.5 mmHg and abnormal PERG amplitudes. Her risk of converting is high. Thus, a discussion on IOP-lowering medications or a selective laser trabeculoplasty should be discussed. OM

DR. SCHWEITZER specializes in advanced glaucoma, refractive surgical clinical care and anterior segment pathology at Vance Thompson Vision. He has had multiple articles published and has delivered lectures on glaucoma, anterior segment pathology, refractive surgical clinical care and surgical management. Email him at justin.schweitzer@vancethompsonvision.com.