From DoA ABJD Wiki
One of the most important aspects of BJD customization is the ability to change the eyes. Because eyes are available in a large variety of sizes, colors, dome heights, and materials, owners can choose eyes that best suit their budget and their intended 'look'. Most eyes are available with either a rounded back (including a nub or stem that can be either blunt or sharp, and can be used to help position the eyes), or with a flattened back (useful for dolls who do not have much empty space in their heads).
Eyes generally come in one of four materials:
- Acrylic Eyes are the cheapest and most common, and are often included with dolls purchased directly from the company. They are the weakest when it comes to durability, as they often have poor reactions with eye putty, resulting in the lens cracking. Most companies sell acrylic eyes in a large range of colors, and some even offer 'blanks' to be customized by the customer.
- Glass Eyes are the next most common, and are popular for their low price and relatively 'deep' appearance. While not prone to being damaged by eye putty, they are more fragile when it comes to being dropped on hard surfaces.
- Silicone Eyes are a less popular type of eye, though they boast a unique flexibility that allows for them to be placed flush in the eye well to minimize gaps. With a soft and slightly porous surface, they must be treated carefully and cleaned frequently as dust will easily accumulate on them. These types of eyes are also pricier, but they do provide a more realistic and natural look.
- Urethane Eyes are becoming more common, and have come to rival glass in popularity. Urethane eyes are slightly more prone to scratching than glass, if handled carelessly. They are similar to high-quality glass eyes in structure and depth, though as they are made of resin they allow for alternate methods of creation that can produce a variety of effects in the final product.
Doll eyes can have a surprising number of color, shape, design and sized pupil/iris combinations. Eyes that have a traditional round, black pupils are considered 'regular', while eyes with unusually shaped pupils, no pupils, or with non-black pupils are considered 'special'. Some companies will offer a very limited stock, while others allow full customization, including pupil, iris, and the ring around the iris to have individually chosen colors.
Dome height refers to the depth of the eye. Some eyes have high/rounded domes, meaning that the colored part of the eye protrudes from the "white" or sclera. This gives the eyes a bit more depth from the shadow the high dome would cast and versatility in appearance most of the time, as some find this gives the doll a "following" eye effect. Others have flat domes, allowing for a closer fit to the eyewell. This produces less shadows on the iris/pupils and has somewhat less depth as the higher domes, but is suitable for those who wish for the full color of the iris to show more.
Sizes are generally measured in mm (millimeter), with the primary measurement being the radius or width of the entire eye. Some manufacturers offer more than one iris width, such as 18mm/10mm (entire eye/iris) and 18mm/9mm. Different head sculpts require different eye sizes, though sometimes an alternate size can be used to make the doll seem more alert, lifelike, or mature (smaller) or doe-eyed/childlike (larger). The most common eyes range from 8mm to 20mm. Usually, a company will list on the doll's sale page what size of eyes the doll can wear.