Protection to +12 Gz.

BACKGROUND: The U.S. Air Force has developed +Gz-protective equipment that will provide most pilots protection to +9 Gz with minimal-to-no straining. This equipment includes a pressure breathing system called COMBAT EDGE (CE), which is currently operational, and the Advanced Technology Anti-G Suit (ATAGS), which is not yet operational. For future high-performance aircraft design it is important to know the upper limit of various protective equipment and techniques. METHODS: Six subjects were randomly exposed to a 12-cell matrix composed of +Gz and the following combinations of protective equipment at three seat-back angles (13 degrees, 30 degrees and 55 degrees from the vertical): 1) the standard CSU-13B/P anti-G suit (STD); 2) the STD suit with CE; 3) the ATAGS; and 4) the ATAGS with CE. Relaxed, followed by straining +Gz tolerance was determined using 15-s rapid onset runs to a maximum of +12 Gz. A comprehensive battery of baseline and post-exposure medical surveillance studies was performed to evaluate the medical consequences of these high +Gz exposures. RESULTS: All 6 subjects were able to achieve +12 Gz with various combinations of +Gz-protective equipment, seat-back angle, and various amounts of straining, from none to maximum. When the data were collapsed over all protective equipment there was a significant (p < 0.05) seat effect. Relaxed tolerance to ROR increased with seat-back angle from 13 degrees to 30 degrees to 55 degrees. There was also a significant protective equipment effect when the data were collapsed over all seat-back angles. CONCLUSIONS: These data confirm that effortless protection to +9 Gz is available using ATAGS/CE with the 13 degree and 30 degree seat-back angle (F-15, F-16 and F-22) and to +10.5 Gz with a 55 degree seat-back angle. Moreover, with ATAGS/CE, and a moderate degree of straining, +12 Gz is definitely achievable at 55 degrees, even with reduced anti-G suit pressure at 55 degrees. With additional straining +12 GC is also achievable at the 13 degree and 30 degree seat-back angles.

Primary idiopathic optic neuritis in U.S. Air Force Aviators.

The records of 31 male aviators seen at the Ophthalmology Branch of the USAF Aeromedical Consultation Service (formerly the USAF School of Aerospace Medicine) for a diagnosis of primary idiopathic optic neuritis (PION) were reviewed. Each subject received comprehensive ophthalmologic and neurologic examinations. The long-term follow-up data were collected through repeat examinations and by survey. Despite 39% of aviators being grounded due to complications of their PION or multiple sclerosis (MS), many aviators diagnosed with PION may be safely returned to flying duties. However, any aviator diagnosed with PION has a risk of recurrence or a potential to develop systemic MS and must be carefully reevaluated and followed to ensure they remain a viable asset and do not compromise flight safety or mission completion.

Photorefractive keratectomy (PRK) in the military aviator: an aeromedical perspective.

Refractive surgery to visually rehabilitate refractive errors of the eye continues to evolve at a significant pace and is here to stay. The surgical manipulation of the cornea by carefully planned incisions, as in radial keratotomy, represented the first procedure to evolve for the correction of ametropia and is an area of continued active development and improvement. However, many concerns mitigate against this procedure in the aeromedical arena. More recently, photorefractive keratectomy using laser technology to ablate and recontour the corneal surface has emerged as a viable modality. This paper explores the aeromedical factors surrounding this new revolutionary procedure and discusses the issues relevant to evaluating its applicability to the modern military aviator as well as reviewing results of the latest clinical trials currently in progress. The goal is to provide the aeromedical community with the fundamental information required to formulate aeromedical decisions and policy-making in regard to a new procedure that is certain to have tremendous impact on the selection of future aircrew candidates.

The USAF Aircrew Medical Contact Lens Study Group: operational problems.

BACKGROUND: Although soft contact lens (SCL) wear for aircrew with refractive errors was approved in June 1989, aircrew with certain ocular disorders, such as keratoconus, have been waivered to fly with contact lenses (CL) since the 1960's. These aircrew are members of the United States Air Force (USAF) Medical Contact Lens Study Group and are fitted [with SCL's or hard contact lenses (HCL)] and followed by the Ophthalmology Branch at Armstrong Laboratory; Brooks Air Force Base, TX. Because HCL's are perceived to be more susceptible to a disabling foreign body (FB) under a lens and are more difficult to remove in flight, Study Group aircrew are the only USAF HCL wearers allowed to fly. METHODS: The medical records of the 142 aircrew members followed for CL wear between 1970 and 1993 were retrospectively examined to determine the type of CL worn, crew position, and the medical reason for CL wear. The Study Group was then surveyed to ascertain whether there were any significant operational problems for aircrew wearing medically indicated CL's. Aircrew were divided into HCL (51 surveys returned) and SCL (44 surveys returned) wearers to compare each modality's efficacy in the flight environment. RESULTS: HCL wearers were more likely than SCL wearers to have endured at least one FB incursion under a lens during flight (p = 0.053). HCL wearers were also more likely to have had a lens come off-center at least once in their careers during flight (p = 0.035). Both groups reported problems with CL dryness in the 5-15% relative humidity of the cockpit. Only four aircrew reported any CL-related Duties Not Involving Flying (DNIF) days during their careers. CONCLUSION: Because HCL's are necessary to correct vision adequately to return aircrew with keratoconus and other corneal anomalies to the cockpit, the USAF needs to continue to investigate the use of rigid gas-permeable HCL's with aircrew.

Barosinus pneumocele: transient visual loss due to sphenoid sinus pneumocele in a U.S. Air Force pilot.

Symptomatic sphenoid sinus pneumoceles are extremely rare. This case presented in a U.S. Air Force aviator who had recurrent left-sided visual loss during ascent in jet aircraft. Computed tomography showed a dehiscent optic nerve within the left sphenoid sinus. Surgical correction included removing a mucosal polyp from the sinus ostium. The aviator has since flown 70 sorties without recurrence of symptoms. This entity is named barosinus pneumocele.

The effect of test chart design and human factors on visual performance with night vision goggles.

In an effort to increase flight safety, it is imperative to learn as much as possible about the man-goggle interrelationship. This study was undertaken to see if type of goggle or other covariates might affect visual acuity (VA). We tested the VA of 103 aircrew with both the AN/PVS-5 and Aviator's Night Vision Imaging System (ANVIS) goggles using a Snellen vision testing chart and the new Night Vision Goggle (NVG) Resolution (Grid Type) Chart. Average VA's using ANVIS (Snellen = 20/38, Grid = 20/45) were significantly better (p < 0.01) than VA's using AN/PVS-5 (Snellen = 20/54, Grid = 20/58). Snellen VA's were better on average than Grid VA's (p < 0.001). Neither age, gender, nor NVG experience affected average VA at the 0.05 level. Average VA was significantly better (p < 0.05) for non-spectacle wearers using ANVIS goggles and for non-smokers using AN/PVS-5 goggles. Visual acuity is better with ANVIS than with AN/PVS-5 goggles, and may be affected somewhat by wearing spectacles, and by smoking.

Aircrew soft contact lens wear: a survey of USAF eyecare professionals.

The USAF, when it approved soft contact lens (SCL) wear for aircrew in June 1989, chose a conservative approach that authorizes only daily-wear of extended-wear SCL's. The aircrew SCL program has been perceived as a success, and follow-up data are no longer being collected. A survey was sent to all USAF eyecare professionals to assess the types and extent of SCL-related ocular pathology, the magnitude of environmental SCL problems in the cockpit, and the brands of SCL's that are being fitted. Only two instances of ulcerative keratitis were reported. The most severe inflight problem reported was the dry cockpit environment. CSI-T (Pilkington Barnes-Hind) was the most frequently used spherical lens and the Hydrasoft Toric XW (CoastVision) was the most used toric lens. The USAF aircrew SCL program appears to be progressing successfully. However, the Ophthalmology Branch at Armstrong Laboratory will continue to monitor the program for serious medical complications.

Cases from the aerospace medicine residents' teaching file. Case #46. A boom operator with evidence of keratoconus.

A boom operator with evidence of keratoconus. The clinical presentation, evaluation, and diagnosis of a boom operator being evaluated for keratoconus. The aeromedical disposition of this patient is also discussed.

Achromatopsia. Clinical diagnosis and treatment.

Six cases of classic achromatopsia are presented. The methods of practical clinical diagnosis are discussed, including paradoxical pupillary constriction in darkness, the easily performed Sloan achromatopsia test, and electrophysiologic studies which are useful in young children. The visual and cosmetic benefits of heavily tinted contact lenses in such patients are stressed.

The Marcus Gunn pupil in experimental tract lesions.

Isolated surgical lesions were made in three Macaca mulatta monkeys. Two had right optic tract section. One control underwent section of the right half of the chiasm. Preoperative evaluation revealed no fundus, pupil, or VER abnormalities. Postoperatively, a classic Marcus Gunn pupil was found contralateral to the isolated optic tract lesions. The control had normal pupils. The nature of the lesions was documented histopathologically, the pupillary findings, photographically. Possible explanations are explored. Contrary to traditional teaching, lesions occurring posterior to the chiasm may indeed produce the Marcus Gunn pupillary phenomenon.

Active central retinal artery embolization.

A 44-year-old white woman with metastatic breast carcinoma and ongoing showers of branch and central retinal artery emboli is presented. The patient had no ocular complaints and demonstrated no cumulative effect from the embolic material, the cause of which remained undetermined despite intensive systemic medical evaluation.