Suprachoroidal Air Injection for Detached Retina

INJECTION of air into the eye is considered by some authors to be useful in certain cases of detached retina (Spaeth, 1941). Where a considerable quantity of subretinal fluid has been evacuated, with consequent collapse of the globe, there are two ways in which the eye may regain its shape and tension. Either the subretinal fluid may re-form and reproduce the detachment, or aqueous may be formed quickly enough to restore the shape of the globe before subretinal fluid has collected in great quantity. Presumably both processes tend to occur simultaneously. The crucial matter would seem to be the nearness of the retinal hole to the choroid at the stage when these structures have been rendered adhesive by diathermy. The union is tenuous in its early stages. The conception that the hole itself is " sealed " by diathermy seems difficult to accept, especially as in the case of a large hole it can still be clearly seen. The fact that the edges of the hole are adherent to the choroid may not be ophthalmoscopically obvious as the layer of " physiological glue " may be thick. However, if the edges of the hole do become adherent to the choroid, the subretinal space becomes a closed pocket. It is no longer in direct contact with aqueous (via vitreous) and hence cannot be fed with high chloride osmotically active fluid. It may be thatthe boundary between the subretinal fluid and the chorio-capillaris is comparable with the blood-aqueous barrier. If this were the case, and the barrier was intact, the tendency might arise for fluid to be " secreted " into the space by the choroid by virtue of the fact that the subretinal fluid was osmotically active. This is purely speculative, but makes the basis for a rational concept ofthe peculiar phenomena associated with the formation and absorption of subretinal fluid and its variations. The " blood-subretinal-fluid barrier " as a concept is useful in developing an argument to explain the behaviour of various types of detachment. In particular one wonders how it is that " spontaneous absorption" of fluid takes place after a retinal hole has been made adherent to the choroid. It would be of great interest to know whether the rate of absorption of such " residual detachments " is related to the degree of damage done at operation to the " blood-subretinal-fluid barrier ". Perhaps Bruch's membrane plus pigment epithelium, if left relatively intact over a wide area, retains chloride