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Biomedical subjects

T J Tredici

Publications and source records attributed to T J Tredici.

At least 19 recordsLinked to original sources
PubMed1998

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.

Adult↗
PubMed1996

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.

Aerospace Medicine↗
PubMed1996

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.

Aerospace Medicine↗
PubMed1992

Yellow lens effects upon visual acquisition performance.

Twenty subjects made a total of 400 threshold visual acquisitions of T-38 aircraft approaching from 9 miles out. Half of the acquisitions were made with the subjects wearing yellow ophthalmic filters, and the other half without filters. No overall statistically significant difference in acquisition performance due to the use of yellow filters was found.

Adolescent↗
PubMed1988

Effects of routine pupillary dilation on functional daylight vision.

The visual acuity of 100 patients between the ages of 16 and 66 years, seen for routine ophthalmologic examination, was measured before and after dilation. All patients had a predilation visual acuity of 20/40 or better. Postdilation binocular visual acuity using the patients' usual correction was measured first in the office and then outdoors, both with the patient's back to and the patient facing the sun, with and without the aid of postmydriatic sunglasses. Twelve percent experienced disabling photophobia even with the use of postmydriatic sunglasses, with 3% having significant objective visual loss defined as 20/50 or worse. No objective visual loss was found in 30 controls examined outdoors before dilation, without sunglasses. We recommend that patients who have experienced significant photophobia with dilation in the past, or who have never before undergone dilation, make arrangements for transportation after a dilated examination.

Adolescent↗
PubMed1988

Central serous chorioretinopathy in U.S. Air Force aviators: a review.

Idiopathic central serous chorioretinopathy (ICSC) is an uncommon disease with the potential to cause loss of visual acuity, decreased color vision, and decreased depth perception. These visual changes may become permanent and require removal of aviators from flight status. This study reviews 55 eyes of 47 USAF aviators with ICSC examined at the United States Air Force School of Aerospace Medicine (USAFSAM), Brooks AFB, TX. Clinical and aeromedical findings, both on initial and on follow-up ophthalmic examination were studied. Ninety-seven percent of aviators otherwise medically qualified were ultimately returned to flight status. Overall, 51% had recurrent episodes, 17% had bilateral disease, and 13% underwent laser photocoagulation. Visual acuity correlated with active disease, and there was a trend toward poor stereopsis and diminished color vision with worsening visual acuity. Eighty-six percent attained a final visual acuity of 20/20 or better. On final examination, 90% had normal stereopsis, 87% had normal color vision, and 49% had a normal central visual field. Eyes with recurrent disease tended to have degraded final visual acuity, stereopsis, color vision, and central visual field. The visual and aeromedical prognosis from a single attack of ICSC is generally favorable, but repeated attacks can lead to a significant decrease in visual functions that may jeopardize flying status.

Adult↗
PubMed1988

Soft contact lens wear at altitude: effects of hypoxia.

In the U.S. Air Force, aircraft can be divided into two categories--those with cabin pressures equivalent to high altitudes and aircraft with cabin pressures equivalent to lower altitudes, with longer duration exposures. The purpose of this study was to determine the effects of soft contact lens wear under atmospheric pressures simulating these two types of aircraft environments. Ten subjects were tested to 7620 m (25,000 ft) in hypobaric chamber flights of 75 min and eight subjects were tested in hypobaric chamber flights at 3048 m (10,000 ft) for 4 h. Four subjects were also tested in dry air to further simulate cabin conditions. Vision and physiologic response were monitored by measurements of visual acuity, contrast sensitivity, and slit-lamp biomicroscopy examinations. The results of this study indicate that the physiologic responses of the cornea to soft contact lens wear at altitude are subject to higher levels of manifested stresses, but these occurred without measurable degradation in vision and did not preclude normal wear of soft contact lenses.

Aircraft↗
PubMed1987

The use of contact lenses by USAF aviators.

Contact lenses are an alternative method to spectacles for correcting refractive errors, but the U.S. Air Force prohibits the wearing of contact lenses by all aircrew members unless medically or optically indicated (AFR 167-3). USAFSAM has a clinical contact lens study consisting of 55 individuals wearing contact lenses for eye defects such as keratoconus, aphakia, anisometropia, and other special indications. Of these 55 individuals, 33 had medical conditions affecting their vision and were unconditionally grounded. Of these individuals, 31 (18 of 19 pilots, 8 of 9 navigators, 5 of 5 other categories) were visually rehabilitated and returned to full flight status by the use of contact lenses. Hard lenses were used in 70% of the cases and soft lenses in 30%. The large number of USAF aviators required to wear spectacles and new head-borne equipment has created compatibility problems with the standard USAF aviators' spectacle. For this spectacle compatibility problem, contact lenses appear as a viable alternative. However, for wide-spread use, concerns remain about the potential aviation hazards, such as +Gz effects, bubble formation, and corneal hypoxia.

Aerospace Medicine↗
PubMed1987

Effect of positive acceleration (+Gz) on soft contact lens wear.

The effects of positive acceleration on soft contact lens wear were tested on a human centrifuge to +8 Gz. There were 11 subjects who participated in this study; 5 were myopic subjects fit with low-, medium-, and high-water-content spherical soft lenses; 3 were astigmatic subjects fit with various designs of toric soft lenses and 3 were emmetropic control subjects. As an additional control, the contact lens subjects were tested with spectacles for comparison. Video photography was used to monitor lens position during the centrifuge rides and visual acuity was checked at +1, +2, +4, +6, and +8 Gz with a reduced Snellen eye chart. Each lens type and control run was evaluated in straight-ahead, lateral, and vertical gaze. No visually significant decentration was noted for any of the lens types tested up to the maximum level of +8 Gz. Visual acuity was reduced at the higher +Gz levels for contact lenses, and spectacle trials, and with the emmetropic controls--all to similar levels. Contact lens wear did not produce any corneal insult due to the +Gz exposure.

Acceleration↗
PubMed1987

Contact lens wear at altitude: subcontact lens bubble formation.

A concern in the past regarding contact lens wear in aviation has been the fear of subcontact lens bubble formation. Previous reports have documented the occurrence of bubbles with hard (PMMA) lenses. Reported here are the results of contact lens bubble studies with soft hydrophilic and rigid gas-permeable lenses. Testing was accomplished in hypobaric chambers and onboard USAF transport aircraft. Hypobaric chamber flights were of three types: high-altitude flights up to 7,620 m (25,000 ft); explosive rapid decompressions from 2,438.4 m (8,000 ft) to 7,620 m (25,000 ft); and 4-h flights at 3,048 m (10,000 ft). Flights aboard transport aircraft typically had cabin pressures equivalent to 1,524-2,438.4 m (5,000-8,000 ft), and ranged in duration from 3 to 10 h. For subjects wearing rigid gas-permeable lenses, central bubbles were detected in 2 of 10 eyes and occurred at altitudes greater than 6,096 m (20,000 ft). With soft contact lenses, bubble formation was detected in approximately 24% (22 of 92 eyes) of the eyes tested, sometimes occurring at altitudes as low as 1,828.8 m (6,000 ft). Soft lens bubbles were always located at the limbus and were without sequela to vision or corneal epithelial integrity. Bubbles under the rigid lenses were primarily central, with potential adverse effects on vision and the corneal epithelium.

Altitude↗
PubMed1986

Air travel and intraocular gas.

The safety of air travel for persons with intraocular gas after ocular surgery has been in question since the mid 1970s, when the use of intraocular gases after vitrectomy became widespread. After vitrectomy, air-fluid exchange was performed on six Rhesus monkeys. During simulated air travel in an altitude chamber, intraocular pressure rose an average of 42 mmHg with intraocular air volumes as small as 0.25 cc. Hypotony was observed after return to ground level in all cases. Transient central retinal artery occlusion and pupillary block was observed. Patient safety and comfort is endangered during air travel with very small volumes of intraocular gas.

Aircraft↗
PubMed1984

Ophthalmoplegic migraine.

A 5-year-old girl developed severe periocular pain lasting 4 days. As the pain subsided, a right oculomotor palsy developed which slowly resolved without aberrant regeneration over a 2 1/2-month period. A classic history and normal high-resolution CT scan were essential in making the diagnosis of ophthalmoplegic migraine. This is a rare disorder classically requiring normal cerebral angiography for diagnosis. With the advent of high-resolution CT scanning, angiography may no longer be indicated in the typical case.

Child, Preschool↗
PubMed1984

Corneal opacification and lecithin-cholesterol acyltransferase (LCAT) deficiency: a case report.

Bilateral corneal opacities are the first clinical sign of a familial lecithin-cholesterol acyltransferase (LCAT) deficiency and can be found in early childhood. Familial LCAT deficiency includes the following typical clinical findings: corneal opacification, proteinuria, anemia, turbid or milky plasma, very low plasma HDL, very low plasma cholesterol esters and lysolecithin, hyperlipidemia, and very low or absent LCAT enzymatic activity. Several patients have had fundus findings including angioid streaks and papilledema. This disease is autosomal recessive and has been reported in a total of 19 patients previously. Progression of the disease has resulted in premature atherosclerosis, renal failure and transplantation, decreasing visual acuity and corneal transplantation.

Adult↗