patient’s environment. If the allergen is a necessary topical medication, such as glaucoma therapy, then an alternative should be found. Meanwhile, the conjunctival oedema may take some time to resolve. The lid position can be improved with inverting sutures.

Temporary inverting sutures are placed through the full thickness of the lower lid at an angle so that the anterior lamella is advanced or rises with respect to the posterior lamella (Fig. 1.11). After subcutaneous infiltration with vasoconstrictive local anaesthetic (1–2 mL of local anaesthetic with 1:80,000 adrenaline is usually sufficient) and topical anaesthetic drops to the conjunctiva, 3 or 4 double armed long acting absorbable sutures such as 4/0 vicryl are placed, entering from the conjunctival surface just under the lower border of the tarsal plate. The needles are then passed anteriorly and inferiorly to come through the skin at a level below that of the entry on the conjunctival surface. The sutures are tied over bolsters and should be removed by 10–14 days.

1.4 Distichiasis

1.4.1 Introduction

Distichiasis is the term used to describe the abnormal growth of hair follicles from what should normally be meibomian glands, and can be congenital or acquired. Congenital distichiasis is rare and is transmitted by dominant inheritance. Due to an error in differentiation, the putative meibomian glands develop into pilo-sebaceous

units. Distichiasis, from metaplasia of the meibomian glands on the posterior lamella into pilo-sebaceous units, can be acquired following chronic inflammatory insults. Examples include chronic blepharitis, cicatricial diseases such as ocular cicatricial pemphigoid and StevensJohnson syndrome, and long term sequelae from infection as in trachoma. These abnormal lashes range in type from fine non-pigmented stumps, to the more recognisable long pigmented ones, and can be few and sparse or multiple. They can be treated by a variety of methods, all of which involve destruction of the lash root, or follicle, to prevent new growth. As not all lashes are in the same part of their growth cycle, these treatments often need to be repeated.

Cryotherapy will destroy broad areas of abnormal lashes. Its application to the lid margin is not pinpoint, even when using the small round tipped cryotherapy probes used in retinal detachment surgery. Inevitably, the freezing time needed to cause death of the lash follicle means that there is also time for the ice to spread further than perhaps desired. Splitting the lid margin so as to separate the anterior from the posterior lamellar edge, prior to treating the posterior edge, helps to prevent the spread of ice onto the normal more anteriorly placed lashes [2, 55]. Cryotherapy cannot be used on pigmented patients as melanin carrying cells die at a higher temperature (c. −10°C) than that required to destroy lash follicles (c. −20°C), potentially leaving these patients with cosmetically unacceptable depigmented patches. The use of a specially designed cryoprobe and its posterior (conjunctival) placement has been shown to minimise these effects in patients with trichiasis [57].