diopter value

逛Mall時在Sears的男裝部門一個角落看到這個算是很尋常的reading glasses展示/販售架。顧客可以自己戴著試，滿意了直接拿去附近櫃台結帳
(我的便宜手機的相機解析度看樣子不甚好...)

以下出現的 strength 字眼相當於我們平常講的(眼鏡)度數:

To Choose Your Correct Strength:

* If you are wearing glasses, remove them.
* Read down the chart to the right at your normal reading distance, about 14 inches
* When the text becomes difficult to read, note the diopter figure on the left.
* The diopter value indicates the strength of the lens that your require.
* Select this strength from the display and check for comfort.
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WEAK    +1.25    If you cannot read this line .....
MEDIUM    +1.75    If you cannot read this line .....
MEDIUM    +2.25    If you cannot read this line .....
STRONG    +2.75    If you cannot read this line .....
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下方展示架上有很多reading glasses(老花眼鏡)(上頭有貼度數標籤)

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另一個賣場看到的:

Step 1 Remove your glasses and step back approximately 14 inches away from the eye test chart.

Step 2 Read the lines starting at the top. The first line that you have trouble reading has the lens' strength to the left. That is your correct strength.

Step 3 Find your glasses easily with our color-coded strength labels.