How to Determine the Optimal Target Value of Intraocular Pressure in Glaucoma Treatment?

General Principles of Glaucoma Treatment

The goal of therapy is to preserve the visual field and quality of life for patients. A significant portion of patients (over 10%) lose a large part of their visual field or become completely blind during their lifetime. Risk factors for blindness include the severity of the disease at the time of diagnosis, bilateral disease, and younger age. Currently, the only way to preserve the visual field in patients with glaucoma is by reducing intraocular pressure. The risk of quality of life loss should determine the target IOP, the intensity of treatment, and the frequency of check-ups for each patient.

Determining the Target Value of IOP

The target IOP is the upper limit that is still compatible with the treatment goal for a given patient. It should be re-evaluated at regular intervals and always with disease progression or the emergence of new ocular or systemic comorbidities. There is no single target IOP suitable for every patient; this value needs to be set individually for each eye of each patient.

The target is set as a specific IOP level or as a percentage reduction in IOP. For newly diagnosed patients, we set the target IOP based on the stage of the disease and the initial IOP value. Generally, a lower target IOP level, i.e., a greater percentage reduction, is necessary for appropriate slowing of disease progression in more advanced stages.

Assessing the Rate of Progression Through Regular Monitoring

The most important predictor of vision loss is the rate at which the visual field narrows. For a newly diagnosed patient, the rate of progression is unknown, and we set the target IOP based on risk factors such as older age, higher initial IOP, the presence of optic nerve head hemorrhage, and lower central corneal thickness.

After sufficient monitoring time with an adequate number of visual field evaluations (usually about 2–3 years with examinations approx. 3 times a year), it is necessary to consider the observed rate of disease progression and adjust the target IOP. If the visual field worsens at a rate that could threaten the patient's quality of life during the expected lifespan, it is essential to lower the target IOP and adjust the treatment.

Factors to Consider When Setting the Target Value:

• Stage of Glaucoma: The greater the pre-existing damage, the lower the target IOP should be.
• Age and Expected Lifespan: While younger age implies a longer lifespan, older age carries the risk of faster progression.
• IOP Without Treatment: The lower the IOP before starting treatment, the lower its target value should be during treatment.
• Corneal Thickness: IOP measured by Goldmann applanation tonometry depends on corneal thickness (lower IOP values are measured in individuals with thinner corneas).
• Rate of Disease Progression during monitoring: The faster the progression, the lower the target IOP should be.
• Other Risk Factors: For example, pseudoexfoliative glaucoma.
• Side Effects of treatment.
• Patient's Preferences and Family History.
• Condition of the Other Eye.

Summary and Conclusion

The goal of glaucoma therapy is to slow down the gradual reduction of the visual field range so that the quality of patients' lives is maintained. There is not enough evidence available to establish a definitive algorithm for determining the optimal target IOP value. Therefore, we set the target IOP for each patient individually, considering the risk factors and the rate of disease progression.

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Source: European Glaucoma Society terminology and guidelines for glaucoma, 5^th edition. Br J Ophthalmol 2021; 105 (Suppl. 1): 1–169, doi: 10.1136/bjophthalmol-2021-egsguidelines.