Vision problems are a frequent cause for pilot groundings and waivers. While there is no way of knowing exactly how many pilots glaucoma grounds we do know that more than 2000 with glaucoma are able to retain active flying status with a medical certificate.
CFR 67 states that a pilot may have, “No acute or chronic pathological condition of either eye that interferes with the proper function of an eye, that may reasonably be expected to progress or that may reasonably be expected to be aggravated by flying.”
The solution is two-fold-early detection and communication. Early detection requires a comprehensive eye exam by an eye care professional. Communication should occur initially between the pilot and a professional eye care provider-ideally one who knows aviation and FARS.
An eye care professional’s responsibility is to document the status of the glaucoma using FAA form 8500-14 Ophthalmological Evaluation for Glaucoma. This will help facilitate the smooth processing of the next flight physical.
Successful management of glaucoma hinges on health education. Presenting facts about glaucoma in an understandable manner is the first step.
Glaucoma: a brief explanation
Glaucoma is one of the most common diseases of the optic nerve and it ultimately leads to loss of vision. There are several types of glaucoma but the one that is of greatest concern to the pilot is Open Angle Glaucoma. There are no symptoms for this type of glaucoma but in more advanced stages a pilot will start developing blind spots in his field of vision. Glaucoma typically involves an increase of eye pressure called intraocular pressure (IOP). Unlike the gel in the back of the eye, the fluid in the front chamber of the eye (aqueous) is produced continuously and is drained off through channels at the base of the color part of the eye (iris). The fluid must be drained so that new fluid can replace it. When drainage is prevented there is a resultant increase in IOP. Some glaucoma patients have high IOP but most patients with high IOP do not have glaucoma. So, contrary to common belief, high pressure in the eye does not necessarily mean that a person has glaucoma. The most common glaucoma indicator is damage to the optic nerve. Therefore, an eye care specialist directs treatment at decreasing this damage. A decrease is accomplished by either reducing fluid formation or facilitating drainage by opening channels in the eye.
Although IOP does not necessarily indicate glaucoma, it is a useful predictor for the risk of visual loss. For example, the normal range for IOP is 12-21 mm of mercury (hg). If IOP is consistently measured in the range of 21-25 mm hg the risk of developing glaucoma in 5-10 years is 2.5%. However, if the pressure is measured greater than 30mm hg the risk jumps to 40%. There are also other factors that pose a greater risk for developing glaucoma. These include age (over 65), family history and race. African Americans tend to develop more severe glaucoma and do not respond as effectively to some of the glaucoma medicines. Therefore, for high risk groups regular screenings and monitoring are particularly important.
If a pilot has a risk factor for glaucoma, it does not necessarily mean he has glaucoma. The diagnosis is confirmed by a variety of tests. These include the appearance of the optic nerve through examination (can be visually inspected by the eye specialist) and the field of vision (visual field) to determine if there are blind spots. These tests plus IOP are relied on by the doctor to make the diagnosis. The risk factors provide an indicator of how frequently a patient should see a specialist.
Doctors base treatment on the potential impact that a medicine will have on IOP. The expectation is that lowering pressure will lower the rate of damage. The ultimate goal is to preserve visual function for as long as the patient lives. Initial treatment involves a wide choice of glaucoma medicines and potential laser treatment. However, if these means cannot control optic nerve damage, then glaucoma surgery offers a final alternative.
Treatment options
Doctors must find the optimal balance of treatment with side effect while considering the special needs of the pilot. Resultant side effects must be considered.
First line defense: beta-blockers
Timoptic’ is the most common drug of choice. It comes from a class of drugs called beta-blockers, which act on specific sites in the eye. When a drug of this type stimulates these sites it triggers an increase or decrease of activity. Timoptic’s action reduces the production of fluid in the eye’s front chamber thereby decreasing IOP. Timoptic is an eye drop, which is usually given twice per day. Some patients experience as much as a 25% reduction in eye pressure. It is not recommended for use in patients that have lung problems (e.g. asthma) or in patients that have heart disease. Other less common side effects may include depression, lethargy, fatigue and sexual dysfunction. While this medicine is considered a first choice drug for the general population, it may not be the choice for aviators because of the complexity of aviation tasks as well as strict guidelines that limit what medications pilots may take. There are at least four other beta-blocker eye drops Betimol, Betagan, Ocupress, OptiPranolol – which doctors prescribe when a patient requires a different dose or an alternative drug choice. Finally, in this category, there is a drug selectively formulated so that it may be used with asthma patients. The drug is Betoptic and it lowers eye pressure without side effects in patients who have lung problems.
Prostaglandins – drugs that are gaining in popularity
If a single medicine does not achieve the desired decrease in IOP then the doctor will consider adding an additional medicine. A drug that is gaining popularity because it is one of the systematically safest drugs for the treatment of glaucoma and it can be used as an additive drug to all but one of the other glaucoma drugs is Xalatan. The dosage is one drop (typically before bedtime) and it acts to decrease pressure by improving uveoscleral outflow. The drug’s downside is its cost-about $1 per day. In about one-third of the patients with hazel eye color Xalatan may cause their eye color to get darker. The irises may actually turn brown. There are some cases where patients eye lashes became thicker and increased in size. Neither of these side effects may be offensive to patients but they should be made aware of these potential changes. Xalatan is a prostaglandin drug. The action of Prostaglandins is to reduce inflammation. Depending on the dosage, Prostaglandins can reduce inflammation in other parts of the body; however, in the eye they open drainage channels and promote the normal outflow of fluid.
0ptic nerve damage can be reduced but not reversed
Doctors direct treatment of glaucoma at reducing (we cannot reverse) the extent and speed of destruction of the optic nerve tissue. Continuous measurement of IOP is the best measure. The use of medicine can reduce IOP two ways-by decreasing the amount of fluid produced inside the eye and/or facilitating the outflow of that fluid. Decreasing eye pressure does not guarantee that the nerve will be undamaged. The only effective means of assuring that the medicine is producing the desired result is by regularly monitoring the visual fields (the visual fields reflect the amount of nerve damage). It is therefore advisable that pilots over 40 establish at least one visual field as a normal baseline to compare with glaucoma or other vision threatening conditions. This is a conservative strategy for the general population. However, for pilots who are required to take recurring medicals, the renewal of their medical may hinge on the eye doctor’s ability to document any damage and assure the FAA that the condition is under control (stable) on treatment. The visual field is a safety net to assure that those factors can be documented.
Oral medications may be used instead of eye drops
Some of the earlier drugs that doctors prescribed for glaucoma treatment are rapidly being displaced but may still be of use to some patients. One such drug is Propine which is derived from a powerful “fight or flight” drug called epinephrine and acts like adrenaline These drugs decrease pressure in the eye. However, researchers also find that the drug dilates the pupil and increases the risk of another kind of glaucoma (angle closure). Some patients also experience allergic reactions. Another drawback to Propine is that it must be used every 12 hrs and may take up to three months to reach its full treatment potential.
A newer drug in this category is lopidine which is derived from a high blood pressure edication. This drug was originally approved in a higher concentration to reduce IOP immediately after laser surgery. In weaker strength the drug may help chronic glaucoma but 20-30% of patients still experience allergic reactions. Dilation of the pupil may also result. Alphagan is a more recent drug in the same class and shares the side effects of lopidine – dry mouth and fatigue. However, if a drug of this class is called for, Alphagan is the drug of choice.
If the target IOP is not met with the first-line options such as Timoptic, Xalatan or Alphagan your doctor may choose a drug that has historically been used in acute glaucoma attacks by oral administration. Carbonic Anhydrase Inhibitors are available in drop (topical) form. These drops are particularly useful if the patient has asthma (a contraindication of Timoptic). Oral medicines significantly reduce side effects. However, they may produce numbness and tingling of the fingers and toes. This may impair a pilots ability to manage flight controls. If a doctor prescribes an oral medication, the patient’s condition must be carefully monitored.
The drugs in this group include Trusopt and Azopt. There is also a new drug that combines Timoptic and Trusopt called Cosopt. This drug is administered twice per day and has the benefit of two medicines in one drop. Oral medicines that may be included from this group include Diamox and Naptazane. These drugs may be used in chronic treatment if drops do not produce the desired effect. However, they are typically used in acute glaucoma attacks.
Other medications
Pilocarpine is the time-honored medication of choice. It acts by making the pupil smaller and opening the eye’s internal drainage channels. Pilots under 40 and those with cataracts should exercise caution when using the drug. Spasms in the eye, painful aching above the eyebrow and blurring of near print are just a few side effects to watch for. Also, the drug must be administered four times a day which makes compliance difficult for a pilot’s lifestyle.
Conclusion
There are various broad spectrum treatment options for glaucoma. However, it is imperative that a pilot catch glaucoma in the early stages before surgery becomes necessary. Additionally, an eye care specialist who has an understanding of the special visual demands of the pilot may act as bridge between the pilot and the aviation medical examiner.
Dr. William Monaco
bill@flightsight.com
Flight Sight
