Vision Drops During Pregnancy (Changes in Eye Prescription)

During pregnancy,
・things may look harder to see, or your vision may drop
・your contact lenses or glasses may no longer suit you
・your vision may seem strange
— any of these may happen.

The tissues responsible for refracting the light entering the eye are
the cornea (the black of the eye) and the crystalline lens.

Both can temporarily change in thickness during pregnancy.

Pregnancy is also a time when the body’s immune system changes greatly.

Temporary changes in the front half of the eyeball (the anterior segment): the cornea and lens
may be the cause of reduced vision during pregnancy.¹。

Most eye complications during pregnancy are mild and temporary and need no treatment.
Sometimes they are serious and permanent, and prompt judgment by an ophthalmologist may be needed.

However, we also need to watch for pathological changes inside the eye.

TOC

Reduced Vision During Pregnancy (Changes in Eye Prescription)

妊娠中に視力が下がる（目の度数の変化）の解説スライド:眼球断面図（参天製薬提供）とともに、角膜の厚み・湾曲、水晶体の厚み・湾曲、涙液量の減少という変化を挙げ、多くは一時的で出産後にもとの度数に戻ることを説明

Here we mainly describe changes in the anterior segment (the cornea and lens).

Temporary changes in refraction (eye prescription): the cornea and lens during pregnancy

・the cornea becomes thicker
・the curvature of the cornea and lens increases

Either can cause a temporary change in refraction.
→ The eyes “get worse,” shifting toward myopia.

視力表記の方法の図解：Vd（右眼視力）＝0.1（1.2×S-2.00 C-1.50 Ax180°）の例で、裸眼視力・矯正視力・球面度数・円柱度数・円柱軸の読み方を示す

This shows up as reduced uncorrected vision / a change in the prescription of glasses and contact lenses
.

It is known to return to the original state after delivery.

Corneal thickness
: an increase of about 1–16 microns in corneal thickness, thought to be due to temporary corneal edema²。

Corneal curvature
: it is known to increase by an average of 1 D in late pregnancy³。
It resolves after childbirth or after breastfeeding ends.

Curvature of the lens
: during pregnancy and breastfeeding, the curvature of the lens also increases,and a temporary decrease in accommodation occurs⁴。

What is a micron?

It refers to a micrometer (μm).
There was an easy-to-understand picture comparing small things.

微粒子の大きさ比較インフォグラフィック（The Relative Size of Particles):ジカウイルス0.045µmからコロナウイルス0.1〜0.5µm、細菌1〜3µm、赤血球7〜8µm、花粉15µm、塩粒60µm、人の髪の毛50〜180µmまでを段階的に並べて示す — Visual Capitalist

Hair: 50–180 microns
One grain of beach sand: 90 microns
One grain of salt: 60 microns
White blood cell: 25 microns
Pollen: 15 microns
Dust: 10 microns or less
Red blood cell: 7–8 microns
Droplets: 5–10 microns
Dust (PM2.5): 2.5 microns
Bacteria: 1–3 microns
Wildfire smoke: 0.4–0.7 microns
Coronavirus: 0.1–0.5 microns
Enterobacteria virus T4: 0.225 microns
Zika virus: 0.045 microns

The change in corneal thickness during pregnancy can be understood as
a change on the scale of bacteria to droplets to red blood cells to pollen
(a change far finer than the thickness of a hair).

Because refraction (the prescription) is unstable,
refractive surgery such as LASIK or ICL (implantable contact lens) is recommended to be postponed.

Keratoconus: changes during pregnancy

There are reports that during pregnancykeratoconusmay progress.^5,6。

The cause is explained as softening of the cornea by estrogen and relaxin (a uterine relaxing factor).

Careful follow-up using corneal topography is recommended.

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Other changes

Diseases that cause serious vision loss, such as retinal disease and glaucoma, may also be hidden.

If you notice anything unusual, it is important to consult an ophthalmologist.

(References)

Sharma, S., Rekha, W., Sharma, T., Downey, G., 2006. Refractive issues in pregnancy. Aust N Z J Obstet Gynaecol 46, 186–188. https://doi.org/10.1111/j.1479-828X.2006.00569.x
Weinreb, R.N., Lu, A., Beeson, C., 1988. Maternal Corneal Thickness During Pregnancy. American Journal of Ophthalmology 105, 258–260. https://doi.org/10.1016/0002-9394(88)90006-2
Park SB, Lindahl KJ, Temnycky GO, Aquavella JV. The effect of pregnancy on corneal curvature. CLAO J 1992; 18: 256– 259.
Duane’s Ophthalmology: Pregnancy and the Mother’s Eye (CD- ROM). Clinical volume 5, Chapter 32. Hagerstown, MD: Lippincott Williams & Wilkins, 2001.
Naderan, M., Jahanrad, A., 2017. Topographic, tomographic and biomechanical corneal changes during pregnancy in patients with keratoconus: a cohort study. Acta Ophthalmologica 95, e291–e296. https://doi.org/10.1111/aos.13296
Bilgihan, K., Hondur, A., Sul, S., Ozturk, S., 2011. Pregnancy-induced Progression of Keratoconus. Cornea 30, 991–994. https://doi.org/10.1097/ICO.0b013e3182068adc