Bilateral cystoid macular oedema due to high altitude exposure: An unusual clinical presentation

High altitude retinopathy: An overview and new insights

High altitude retinopathy (HAR) is a common ocular disorder that occurs on ascent to high altitude. There are many clinical symptoms, retinal vascular dilatation, retinal edema and hemorrhage are common. These usually do not or slightly affect vision; rarely, severe cases develop serious or permanent vision loss. At present, the research progress of HAR mainly focuses on hemodynamic changes, blood-retinal barrier damage, oxidative stress and inflammatory response. Although the related studies on HAR are limited, it shows that HAR still belongs to hypoxia, and hypobaric hypoxia plays an aggravating role in promoting the development of the disease. Various studies have demonstrated the correlation of HAR with acute mountain sickness (AMS) and high-altitude cerebral edema (HACE), so a deeper understanding of HAR is important. The slow ascent rates and ascent altitude are the key to preventing any altitude sickness. Research on traditional chinese medicine (TCM) and western medicine has been gradually carried out. Further exploration of the pathogenesis and prevention strategies of HAR will provide better guidance for doctors and high-altitude travelers.

Impact of flight and equivalent short-term high-altitude exposure on ocular structures and function

Background

Exposure to high-altitude conditions during flight or similar activities affects many aspects of visual function, which is critical not only for flight safety but for any altitude-related activity. We aimed to summarize the available literature pertaining to ocular changes during flight or equivalent short-term high-altitude exposure (e.g., hypobaric chamber, effortless ascent lasting ≤ 24 h) and to highlight future research priorities.

Methods

Using the PubMed/MEDLINE and Web of Science/ISI Web of Knowledge databases with structured search syntax, we conducted a systematic review of the literature spanning a 40-year period (January 1, 1983, to October 10, 2023). Articles pertaining to ocular changes during flight or flight-equivalent exposure to altitude were retrieved. The reference lists of retrieved studies were also searched, and citations of these references were included in the results.

Results

Of 875 relevant PubMed and ISI publications, 122 qualified for inclusion and 20 more were retrieved from the reference lists of initially selected records, for a total of 142 articles. Reported anterior segment changes included deterioration in tear film stability and increased dry eye incidence, increased corneal thickness, discomfort and bubble formation in contact lens users, refraction changes in individuals with prior refractive surgery, decreased intraocular pressure, and alterations in pupillary reaction, contrast sensitivity, and visual fields. Photoreceptor-visual pathway changes included alterations in both photoreceptors and neuro-transduction, as evidenced in dark adaptation, macular recovery time, reduction in visual field sensitivity, and optic neuritis (likely an element of decompression sickness). Retinochoroidal changes included increases in retinal vessel caliber, retinal blood flow, and choroidal thickness; central serous chorioretinopathy; and retinal vascular events (non-arteritic ischemic optic neuropathy, high-altitude retinopathy, and retinal vein occlusion).

Conclusions

The effect of short-term high-altitude exposure on the eye is, in itself, a difficult area to study. Although serious impairment of visual acuity appears to be rare, ocular changes, including tear film stability, contact lens wear, central corneal thickness, intraocular pressure, contrast sensitivity, stability of refractive surgeries, retinal vessels, visual fields, and macula recovery time, should be considered in civilian aviators. Our report provides guidance to climbers and lowlanders traveling to altitude if they have pre-existing ocular conditions or if they experience visual symptoms while at altitude. However, key outcomes have been contradictory and comprehensive studies are scarce, especially those pertaining to the choroid and retina. Such studies could not only deepen our understanding of high-altitude ocular pathophysiology, but could also offer valuable information and treatment possibilities for a constellation of other vision-threatening diseases.

Cystoid macular edema precipitated by altitude in a patient with X-linked retinitis pigmentosa

BACKGROUND

X-linked retinitis pigmentosa (XLRP) is a hereditary retinopathy that may present with cystoid macular edema (CME). The exact cause of CME in XLRP is unknown. We describe a case report of new-onset CME precipitated by travel to high altitude in an adult with XLRP, but no known prior history of CME.

CASE DESCRIPTION

A 38-year-old man with XLRP caused by a hemizygous pathogenic variant in RPGR (c.372del; p.Glu125fs) reported sudden onset bilateral blurry vision 4 days after ascending to an altitude of 3,700 m. He sought local ophthalmic care and was found to have severe bilateral CME. He was treated with topical and oral carbonic anhydrase inhibition and instructed to return to normal altitude. Follow-up imaging at normal altitude revealed that the CME was nearly completely resolved 4 days after initial presentation, and completely resolved 2 weeks after initial presentation.

CONCLUSION

Vascular and metabolic changes caused by retinal degeneration in XLRP may predispose to the development of CME under the hypoxic conditions experienced at high altitudes. We advise that retinal specialists treating patients with RP should caution them on traveling to high altitudes that could precipitate or exacerbate CME.