Tour de France: how riders see at 90 km/h on a descent

On a Tour de France mountain descent, a rider can exceed 90 km/h: at that speed, he covers 25 meters every second and must read the road, plan the racing line, judge a corner’s grip and the move of the rival beside him, all in a split second. This feat does not rest on the legs alone: it draws on a heavily taxed “dynamic” vision, on contrast sensitivity in wooded shade and tunnels, and on an ocular surface pushed hard by the wind. Understanding how a cyclist sees also sheds light on a very practical question for the amateur rider: glasses, contact lenses, or refractive surgery?

THE ESSENTIALS

THE CHALLENGE

Seeing at 90 km/h: what the eye and brain must process

When a rider tips into a descent, the scene rushes by at a speed that leaves little margin for error. The gaze must constantly anticipate: spotting the ideal line dozens of meters ahead, gauging a corner’s radius, detecting a patch of moisture or a stray piece of gravel, all while keeping the wheel of the rider alongside in peripheral vision. This is not a feat of “good eyesight” in the sense of the acuity chart, but rapid, holistic visual processing.

Several abilities combine: acuity in motion, contrast sensitivity, peripheral vision, reaction time, and the capacity to track several moving elements at once. Vision-science research has in fact shown that the ability to identify moving targets is linked to the ability to track multiple objects simultaneously, a skill directly useful in a fast-moving peloton.

In other words, a cyclist’s vision is closer to a pilot’s than to a reader’s: what matters is the speed of analyzing a complex, shifting scene, not reading a fixed line of text.

DYNAMIC VISION

Dynamic visual acuity, a skill in its own right

“Static” visual acuity — the kind measured by reading still letters — does not predict performance on a moving target. Dynamic visual acuity (DVA) refers to the ability to make out the details of a moving object, or when you yourself are moving. That is precisely the situation of a rider on a descent.

The sports-vision literature suggests that dynamic acuity is generally higher in trained athletes than in non-athletes, even when their static acuity is comparable. Among professional soccer players, dynamic acuity actually varies by playing position, illustrating how closely this aptitude is tied to the real visual demands of the activity.

Can you “train” your vision?

The question is debated. Part of these differences probably reflects selection (elite athletes have excellent visual-motor aptitudes from the outset) rather than a simple training effect. “Sports vision training” programs show encouraging results on the visual tests themselves, but their transfer to real on-field performance still needs to be confirmed by larger studies. In practice, the priority is not to improve already-normal eyesight: it is to correct what can be corrected and to preserve the ocular surface.

VISUAL FIELD

The visual field in the peloton: seeing without looking

In the heart of the peloton, a rider cannot fix his gaze on each wheel around him one after another: there would be no time. He monitors the whole “out of the corner of his eye,” thanks to his peripheral vision. It is what signals a swerve, a sudden braking, or a crash beginning three rows ahead, without the gaze ever having to leave the road.

Sports-science studies show that peripheral vision serves precisely to monitor several moving objects at once — rivals and teammates — and that peripheral information-gathering strategies distinguish expert players from less experienced ones. Other work indicates that trained athletes detect a target appearing in the periphery faster than non-athletes. The peloton is the real-world application of this skill.

The “useful field of view” narrows at high speed

The notion of the useful field of view refers to the zone from which you can extract information in a single glance, without moving your eyes. This field is not fixed: it narrows when attention is divided, under the effect of speed, stress, or fatigue. In driving, the measurement of the useful field of view is one of the best predictors of crash risk, precisely because it reflects the ability to process a complex scene quickly.

The logic is the same on a bike: the higher the speed and mental load, the tighter the “bubble” of usable information closes around the point of fixation. This is also why a pathological loss of the visual field — such as that of early glaucoma, which is silent for a long time — must be screened for: without our noticing, it eats away at part of this peripheral vigilance. An eye examination includes an assessment of the visual field.

CONTRAST

Tunnels, wooded shade, backlighting: the role of contrast sensitivity

A mountain descent rarely runs through uniform light. The rider goes from blinding full sun to the dense shade of the woods, passes through a short tunnel, faces late-afternoon backlighting. In all these situations, acuity measured on a well-lit black-on-white chart is not enough to describe what the eye actually perceives.

Contrast sensitivity — the ability to tell apart close shades of gray, the texture of asphalt, the edge of a cast shadow — then becomes decisive. It is what lets you “read” a matte road surface at the entrance to a shaded corner. And this function is particularly sensitive to the eye’s optical imperfections: an important point when discussing vision correction, because not every correction acts the same way on fine vision at low contrast.

GLARE

Low sun and glare: the invisible enemy of the descent

In the mountains, the light is more intense and the sun is often low at the start and end of a stage. Glare — that visual discomfort that temporarily “washes out” contrasts — can hide a detail of the road at the worst moment. Sport sunglasses with photochromic or polarized lenses, chosen for the activity, reduce this effect and improve comfort without compromising vision.

Glare is not just a matter of comfort: it affects safety. It is also heightened by certain eye conditions (an early clouding of the lens in the older rider, a dry eye that degrades the tear film). This is one of the reasons a cyclist who complains of “sensitivity to light” is better off having their eyes checked than buying pair after pair of glasses.

WIND & DRY EYE

The descent wind dries out the eye (and blurs vision)

At 70 or 90 km/h, the relative wind hits the surface of the eye like a hair dryer. This airflow speeds up the evaporation of the tear film, that thin veil of tears that keeps the image sharp. When this film breaks too quickly between blinks, vision becomes unstable: this is the intermittent blur that cyclists know well, cleared for a moment by a blink and then returning at once.

This is not just an impression: wind exposure is a recognized risk factor for dry eye. In a population-based study, people exposed to excessive wind had a risk of dry eye roughly twice as high, with sun exposure also playing an aggravating role. Other work shows that wind speed is associated with a faster break-up of the tear film and greater distress of the corneal surface.

What actually helps

Wraparound glasses that create a protective pocket of air, preservative-free artificial tears before and after the effort, and treatment of any underlying dryness clearly limit the discomfort. For a contact lens wearer, wind and dust worsen the discomfort: it is often in these conditions that the lens “sticks,” stings, or shifts out of place.

CORRECTION

Glasses and contact lenses: why they show their limits on a bike

For a cyclist who is nearsighted, astigmatic, or farsighted, correction is not a minor detail: uncorrected myopia degrades distance vision and dynamic acuity, and correcting it improves precisely these performances. What remains is choosing how to correct, because each solution has constraints specific to riding.

• Corrective glasses fog up when you stop, catch rain and spray on descents, slip with sweat, and complicate wearing wraparound sunglasses. Custom frames exist, but remain a compromise.
• Contact lenses free up the visual field and pair with any sunglasses. But wind, dust, and dry air promote dryness and discomfort, and the risk of a lens decentering or being lost mid-effort is not zero.
• Refractive surgery removes the dependence on a removable correction, which explains the interest of many endurance athletes. It is, however, neither automatic nor without considerations: it is decided after a full workup, case by case.

REFRACTIVE SURGERY

Why many athletes turn to refractive surgery

Going without glasses and contact lenses during the effort is a strong argument for a cyclist: no more fogging, no more lens drying out in the wind, no more correction to manage in the rain. This is one of the reasons refractive surgery — LASIK, PKR, or SMILE — appeals to many endurance athletes. The choice of technique depends on each person’s profile (corneal thickness and shape, degree of correction, lifestyle), a topic we detail in our article on refractive surgery according to the sport practiced.

One must stay clear-eyed and honest: operating on a healthy eye alters its optics. Contrast sensitivity in low light and night-vision quality deserve particular attention, because some corrections can increase the eye’s optical aberrations. This is why the preoperative workup is decisive: it checks that the cornea, the tear film, and the correction are suited to surgery, and it makes it possible to honestly set out both the expected benefits and the limits. No procedure “guarantees” an identical result for everyone — it aims to reduce a dependence, after an individual assessment.

With Dr Moïse Tourabaly, the consultation and workup take place at the practice; laser refractive surgery is performed at the Clinique Laser Victor Hugo. The goal is never athletic performance in itself, but lasting, safe visual comfort, tailored to the patient’s lifestyle.

PROTECTION

Protecting your eyes on a bike: UV, projectiles, dryness

Whether you ride in the Tour peloton or on Sunday along country roads, eye protection answers three very real threats:

• UV. At altitude, ultraviolet radiation increases as you climb. Chronic, unprotected sun exposure is a recognized factor in ocular aging; lenses filtering 100% of UV are essential (see our article on sunglasses and protection against cataract).
• Projectiles. Gravel, insects, twigs: on a bike, the eye is exposed. Wraparound polycarbonate sport glasses protect against impact and wind.
• Dryness. Wind, dry air, and prolonged effort weaken the tear film. Artificial tears and wraparound glasses limit the discomfort; persistent dryness warrants an opinion.

AMATEUR RIDING

Amateur cyclist: when should you have your eyes checked?

You do not need to be chasing the yellow jersey to be concerned. A few signals justify an eye consultation: distance vision that is worsening, sensitivity to light or glare on descents, intermittent blur relieved by blinking, persistent contact lens discomfort during effort, or simply the wish to explore refractive surgery to ride without correction.

An examination makes it possible to measure vision precisely, analyze the ocular surface, and discuss, with no obligation, the solution best suited to your riding. Seeing the road better also means riding more safely.

FAQ

Frequently asked questions

Scientific sources

1. Zimmerman AB, Lust KL, Bullimore MA. Visual acuity and contrast sensitivity testing for sports vision. Eye Contact Lens. 2011;37(3):153-159. PMID 21378574
2. Jorge J, Fernandes P. Static and dynamic visual acuity and refractive errors in elite football players. Clin Exp Optom. 2019;102(1):51-56. PMID 30054950
3. Lee JS, Liu YH, Chen WM, et al. Association of sports vision with age, gender, and static visual acuity among nonathletic population. Taiwan J Ophthalmol. 2022;12(1):53-60. PMID 35399972
4. Vera J, Redondo B, Molina R, Jiménez R, Dalton K. Relationship between dynamic visual acuity and multiple object tracking performance. Perception. 2022;51(8):539-548. PMID 35668637
5. Vater C, Roca A, Williams AM, Hossner EJ. Testing the functionality of peripheral vision in a mixed-methods football field study. J Sports Sci. 2019;37(24):2789-2797. PMID 31631809
6. Muiños M, Ballesteros S. Peripheral vision and perceptual asymmetries in young and older martial arts athletes and nonathletes. Atten Percept Psychophys. 2014;76(8):2465-2476. PMID 25005071
7. Wood JM, Owsley C. Useful field of view test. Gerontology. 2014;60(4):315-318. PMID 24642933
8. Sahai A, Malik P. Dry eye: prevalence and attributable risk factors in a hospital-based population. Indian J Ophthalmol. 2005;53(2):87-91. PMID 15976462
9. Deng X, Qi W, Zhao S, et al. Effects of climate factors and Demodex infestation on meibomian gland dysfunction-associated dry eye diseases. Sci Rep. 2024;14(1):284. PMID 38168639

Further reading

• Refractive surgery and sport: which technique for which athlete?
• LASIK: principle, procedure, and recovery
• The preoperative workup in refractive surgery

Practice of Dr Moïse Tourabaly · Tel. 01 45 47 08 11

Disclaimer

This article is intended for information. A personalized ophthalmological opinion remains essential for any decision concerning your correction or surgery.

This article is intended as general information and does not replace a medical consultation. Choosing a correction (glasses, contact lenses) or refractive surgery requires a full eye examination, including assessment of the cornea and the ocular surface. The decision to operate is made case by case, after detailed information is given to the patient about the expected benefits and the limits. For any question about your vision, consult an ophthalmologist.