198 - Eye health—everything you need to know | Steven Dell, M.D.

KEYPOINTS

• 01

  Eye surgery is microsurgery at an extreme scale.

  Steven Dell, an ophthalmologist and refractive and cataract surgeon, describes sutures as fine as 11-0 (cardiac surgeons use 7-0 or 8-0 for coronary arteries); as a trainee he practiced tying 11-0 every night on call. Each surgical field's 'bread and butter' changes by era; when he trained, it was cataract surgery and diabetic retinal disease.

• 02

  The eye handles a staggering range of light.

  Humans can function from dim light to around 200,000 lux, many orders of magnitude. Eye color variation mirrors skin pigmentation: darker eyes cluster near the equator, where visible, UV and infrared light are more damaging to the retina.

• 03

  20/20 is average, not the limit.

  20/20 means seeing at 20 feet what a 'normal' person sees at 20 feet; 20/10 is better. Some athletes Dell has treated were 20/20 and wanted 20/15 or 20/10, which modern laser vision correction can achieve, though most of their medical screening had never checked vision at all. The theoretical limit, set by photoreceptor spacing, is somewhere around 20/8.

• 04

  Astigmatism is extremely common.

  Astigmatism means the eye's focusing power differs by meridian; Dell estimates that more than 60% of people with glasses have a significant amount. The cornea is about 500–550 microns thick, roughly a credit card.

• 05

  Myopia is an epidemic driven by indoor near work.

  Up to 90% of the population in some Southeast Asian cities is now nearsighted, too fast to be evolutionary. The eye adapts within a lifetime. Staying inside in dim light doing near tasks raises myopia risk about 16-fold compared with kids who go outside, and brightness matters: noon outdoor time beat 8 a.m. outdoor time, likely through light-driven retinal dopamine release.

• 06

  Prescriptions should stabilize in your early 20s.

  The eye typically stops changing around ages 23–24. Afterward, worsening prescriptions usually signal cataract formation, which begins affecting the lens's light-bending power in the 50s–70s. Dell rarely sees patients in their 70s without some cataract.

• 07

  Cataract surgery and lens implants have transformed outcomes.

  Modern cataract surgery with implanted lenses, developed from the 1980s, both removes the cloudy lens and can correct refractive error. Dell has worked since the mid-2000s on implant designs that could restore focusing ('zoom'). New eye drops such as a pupil-shrinking drug that works in about 15 minutes (expected commercially in early 2022) can temporarily improve near vision.

• 08

  PRK, LASIK and SMILE trade off differently.

  First laser treatments were in 1989, with FDA approval of PRK and LASIK around 1995–96. PRK removes the roughly 50-micron epithelium and reshapes the surface, with slower recovery. LASIK cuts a roughly 100-micron flap (about 20% of the cornea) and is like opening a book to page 100 and removing pages 100–110; it carries lower infection risk but introduces flap risks. SMILE extracts tissue through a tiny keyhole. Thin corneas or strong prescriptions may favor PRK.

• 09

  Dry eye follows laser surgery and is common generally.

  Both PRK and LASIK cause temporary dry eye in most patients, usually resolving in about 60–90 days, sometimes longer. GLA (from black currant seed, borage or evening primrose oil) may help. The NEI's DREAM trial of 3 g/day of EPA and DHA found no superiority over olive oil, though Dell notes criticisms of its design.

• 10

  Glaucoma is many diseases with one endpoint.

  Glaucoma is probably about 100 different diseases sharing a final common pathway of pressure-related damage to the optic nerve. Pressure is measured by indenting the anesthetized cornea with a known force. Management has improved greatly, including minimally invasive glaucoma surgery (MIGS).

• 11

  The eye is a window into metabolic disease.

  Diabetes is largely a microvascular disease, and the retina lets clinicians watch it directly; leaking vessels are an early sign of retinopathy. Dell and Attia reject binary HbA1c thresholds (5.6 normal, 6.0 prediabetic, 6.5 diabetic): risk is a continuum, and damage visible in the eye is probably also in the kidneys and toes.