– EYELASHES: ANATOMY AND CONDITIONERS FOR INCREASING LENGTH AND FULLNESS/THICKNESS

EYELASHES: ANATOMY AND CONDITIONERS
FOR INCREASING LENGTH AND
FULLNESS/THICKNESS

Susan Lin, M.D.

448 N. San Mateo Drive San Mateo CA 94401 USA

ABSTRACT

This chapter describes the anatomy of eyelash hair and conditioners as well as methodology to beautify one of the most beguiling substrates related to beauty.

The history of eyelash beautification is a long one. It was first documented in Egypt with the use of a mixture of donkey feces and kohl pigmentation to paint on lashes. Lash transplant was developed about a decade ago. Commercial lash conditioners first arose in early 2000 and were composed of oil and vitamins. They only produced modest results. A flurry of prostaglandin- containing lash conditioners were developed in 2007 with one published study described below. Subsequent second-generation bioactive peptide lash conditioners and recent third-generation adipose stem-cell secreted peptide are currently on the market. In view of the vast changes in the technology, and the importance consumers place upon beautiful eyelashes as an essential part of their overall approach to looking good leading to feeling good, this chapter is worth the read.

TABLE OF CONTENTS

3.3.5.1 Lash Anatomy

3.3.5.2 Lash Growth Cycle

3.3.5.3 Lash Conditioners

e. Newer-Generation Lash Conditioners

f. Observations with lash conditioner usage:

3.3.5.1 LASH ANATOMY:

Eyelash hair is cosmetically unique and different than the rest of the hair on our body. Eyelashes are much shorter than scalp hair. Lashes are approximately 4–14 mm in length, depending on location, race, and age. Eyelash follicles extend about 2 mm deep into the dermis. Due to thinness of the eyelid, sectioning reveals a thin epidermis with the absence of hypodermis.

The upper eyelid contains approximately 300–400 eyelashes arranged in multiple rows in triangular or pyramid shape. Lower eyelashes have shorter and fewer lashes, with generally about 100–150 lashes on the lower lid.

All eyelashes are characterized by a tendency to bend from the bulb to the tip of the shaft. The degree of curvature is dependent on the asymmetric distribution of keratin 38 in the hair bulb, resulting in a curved fiber. Curvature is noted most in the African race, followed by Caucasian and least in Asians.

In contrast to scalp hair, the eyelash is free of arrector pili muscle. There are roughly 50 glands in the upper eyelids and 25 glands in the lower eyelids. Two types of glands, known as Zeis and Moll glands, surround the eyelash follicles. Zeis glands are unilobular sebaceous glands. They are found at the margin of the eyelids, producing an oily substance into the mid-portion of lash follicles. Moll glands are modified apocrine sweat glands. Meibomian glands are sebaceous glands secreting lipid to form a tear film. Melanocytes are found in very high density in three areas: the basal layer of the eyelid epidermis, the ORS, and the eyelash follicle.

3.3.5.2 LASH GROWTH CYCLE:

Length of eyelash cycle is much shorter than scalp hair, with anagen one to four months and telogen four to eight months. By comparison, scalp hair anagen phase is two to six years and the telogen phase (the transition from resting into the active growth phase) is three months. During the anagen (growth) phase, average daily growth rate is 0.12 mm with range +0.05 mm. Approximately 60–85% of eyelash follicles are in the telogen phase, in comparison to scalp which is only 15%. Thus duration of the eyelash anagen phase is strikingly shorter, with growth rate lower than that of the scalp hair.

It has been observed that the use of lash conditioners increases the percentage of lashes in anaphase from 20 to 90% and extends the duration from four months to two years. Although the exact cellular mechanism is not well defined, it has been suggested to be through the regulation of intracellular c-AMP levels but has not yet been proven (16).

3.3.5.3 LASH CONDITIONERS:

a. History:

Synthetic prostaglandin analogues, used for the treatment of glaucoma in the form of ophthalmic drops, have been shown to result in the desired cosmetic side effect of increased eyelash length, number, and thickness (2–6). This is likely due to follicles entering the telogen phase prior to entering the anagen phase.

b. Safety Assessment:

To achieve the desired cosmetic goal of eyelash beautification by means of increasing length, number, and thickness, the novel synthetic compound dechloro ethylcloprostenolamide was developed in 2007 and its safety was assessed.

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