Primary Retinal Detachment

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resorption. The combination of glaucoma with retinal detachment
leads to several considerations with respect to PR. Patients with
a functioning bleb or tube shunt device in place may be better
managed by PR than scleral buckle (SB). Although an expanding
gas bubble has the potential to dramatically raise the intraocular
pressure (IOP), bubble expansion typically occurs simultaneously
with resorption of SRF. The resolution of SRF provides potential
space for bubble expansion without perturbations in the IOP. Only
detachments with scant SRF or chronic, thick SRF are more prone
to IOP problems and, as a result, are relative contraindications to
PR in patients with coexisting glaucoma.
Gas Selection
4 Pneumatic Retinopexy for Primary Retinal Detachment
Intraocular gas works by temporarily closing retinal breaks via the
surface tension properties of the bubble meniscus. Blocking the
movement of liquid vitreous into the subretinal space allows the
retinal pigment epithelium to actively pump fluid from the subretinal
space and flatten the detachment. Once the neurosensory
retina is in apposition to the pigment epithelial layer, the adhesive
properties of cryopexy or laser retinopexy permanently close the
break(s). The most commonly utilized gases are air, sulfur hexafluoride
(SF 6), and perfluoropropane (C 3F 8). Choice of gas is based
upon volume issues, arc length of contact/bubble size requirements,
and bubble duration (Table 4.1) [7]. The tamponade must
last until the laser or cryopexy adhesion is strong enough to resist
reopening – generally 3–5 days for laser and 5–7 days for cryopexy.
Air is non-expansile and quickly disappears from the eye. Sulfur
hexafluoride and C 3F 8 are expansile and have longer half-lives. In
general, a 1-ml final bubble size tamponades a 120° arc length,
which is sufficient for most cases of PR (Table 4.2) [8]. There is,
however, considerable variation based on the axial length/ size of
the globe, so that larger bubbles are required in myopic individuals
to achieve the desired arc length of contact.