The prevalence of Primary Open Angle Glaucoma increases with age and the disease is extremely uncommon in patients prior to the age of 40. While more and more women become pregnant in the 4th or 5th decade of their life due to advances in in vitro fertilization we may encounter childbearing women with glaucoma.
Management of glaucoma in pregnant women and in those who try to conceive remains a challenge because of the potential side effects of commonly used glaucoma medications and due to the risks of filtering glaucoma procedures. It is however possible to encounter a reduction in the eye pressure during pregnancy without further interventions.
INTRAOCULAR PRESSURE & PREGNANCY
The precise effect of pregnancy on intraocular pressure and on Primary Open Angle Glaucoma has not been fully elucidated. Studies on healthy controls have demonstrated a statistically significant reduction in intraocular pressure by about 10% throughout pregnancy especially during the 3rd trimester. In a study of women with ocular hypertension a modest reduction in intraocular pressure was noted. This reduction was more noteworthy in the 3rd trimester of gestation and was accompanied by reduced diurnal eye pressure fluctuations as well. Qureshi et al. also report that this eye pressure reduction was more substantial in multigravida compared to primigravida mothers and they attributed this difference to the stress of mothers bearing their first child and to stress-related hormones such as epinephrine and norepinephrine.
This eye pressure reduction has been attributed to:
1. Enhancement of uveoscleral outflow due to hormonic changes (estrogens, progesterone, β-HCG).
2. Oxidative stress during pregnancy that may cause reduced aqueous humor production.
3. Reduction in episcleral venous pressure.
4. Finally, it is possible that this recorded intraocular pressure reduction is not real. Our measurements may underestimate the eye pressure secondary to reduction in the corneoscleral rigidity because of hormonic influences.
Despite the fact that the literature agrees that pregnancy is associated with a reduction in intraocular pressure the disease can progress during that period of time. Brauner et al. have shown that 36% of pregnant women with glaucoma progress and may even have elevated eye pressure as a result of decreased compliance with medications or due to their inability to use some of them out of safety concerns for the fetus.
LABOR IN PATIENTS WITH GLAUCOMA
In women with angle closure, labor can precipitate an acute angle closure crisis. A study that recorded eye pressures during labor documented a statistically significant average rise in eye pressure by 1.4mmHg during labor followed by an average drop by 3.4mmHg immediately after labor and a return back to baseline 72 hours later. We assume that the increase of oxytocin levels during labor causes vasoconstriction and reduction in trabecular outflow of aqueous humor and that a Valsava mechanism is responsible for increased intraocular pressure during contractions. Furthermore, a possible blood loss may cause temporary systemic hypotension which may lead to decrease optic nerve perfusion and tissue damage.
GLAUCOMA TREATMENT DURING PREGNANCY
Glaucoma management during pregnancy requires a fine balance between benefits and risks for the mother and the fetus. 80% of the volume of an eyedrop instilled in the eye follows the nasolacrimal duct and is being absorbed through the nasal mucosa into the systemic circulation. Moreover, eyedrops bypass hepatic clearance and enter the systemic circulation of the fetus through the placenta unmetabolized.
Organogenesis occurs during the first 12 weeks of gestation and a possible harmful effect of medications can be detrimental during that period of time. Teratogenesis has never been documented with any of the glaucoma medication currently in use but these have not been adequately studied in this regard. We can only infer safety from studies performed on Guinea pigs and such data are only available for brimonidine.
CONCLUSIONS
1. Pregnancy with concurrent glaucoma occurs very infrequently. Intraocular pressure may decrease during pregnancy and surgical interventions are seldom necessary. Most glaucoma medications belong to category C which implies that we are unaware of effects on the fetus. We should not anticipate relevant clinical studies any time soon due to ethical concerns.
2. Only brimonidine belongs to category B which means it has been studied in pregnant animals without any documented teratogenic effects. Brimonidine is contraindicated during lactation because it is secreted in breast milk and can cause central nervous depression in infants and young children.
3. Laser Trabeculoplasty is a safe and effective alternative to medication during pregnancy.
4. Surgical interventions can be performed under topical anesthesia but should be performed without the use of antimetabolites.
5. When medical treatment is mandated during pregnancy the safest agent on the smallest possible dose should be employed after an honest discussion with the patient’s family about risks and benefits.
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Dr. Theodoros Filippopoulos, MD
Ophthalmic Surgeon