Glaucoma ranks as the third most common cause of irreversible blindness in adults. Surgical treatment options for glaucoma include trabeculectomy and the use of devices such as EX-PRESS or the Glaucoma Drainage Device, with the latter often being mistaken for foreign bodies. 

Cataracts are the most common cause of reversible blindness in adults. The most frequently used surgery is phacoemulsification, whose post-surgical changes are easily detectable in both CT and MRI scans. 

Surgical treatment for retinal detachment includes scleral buckles and vitrectomies, whose tomographic appearance should not be confused with intraocular infections or hemorrhages.

This presentation outlines the radiological characteristics for each of these procedures, which are routinely recognized as incidental findings in examinations requested for other reasons. It also mentions other surgical devices such as orbital and eyelid implants, as well as radiological mimics, including trochlear apparatus calcifications, senile scleral plaques, and drusen.

Glaucoma

The most common surgery is trabeculectomy, which does not show evident findings in post-surgical CT or MRI. Other surgical options include the use of various devices, among which we find the EX-PRESS and the glaucoma drainage devices (GDD).

1. EX-PRESS: these devices have been used worldwide in recent decades; they are surgical stainless steel devices measuring 2 to 3 mm, inserted under a scleral flap (Figure 1). In CT, they appear as a pinpoint image with metallic density. In MRI, they exhibit susceptibility magnetic artifacts. Their characteristic location is in the superior corneoscleral junction, superonasal, or superotemporal. Horizontal or inferior placement is rare; in these cases, a foreign body should be considered.  
   

   Fig 1: A, B and C: Ex- PRESS Glaucoma filtration device. References: A: Grlica, I. 2023. B: Hospital San Juan de Dios de La Serena. C: Case courtesy of Gerard Carbo, Radiopaedia.org
    
2. Glaucoma Drainage Device (GDD): these are two-part devices, a tube inserted into the anterior chamber and a plate fixed to the sclera. Superotemporal and inferonasal insertions are preferred. Superonasal insertion is avoided to prevent damage to the trochlear apparatus. In CT, the plates appear as hyperdense curvilinear structures adjacent to the eyeball (Figure 2). Density varies according to the manufacturer. The most commonly used devices include the Ahmed, Molteno, Baerveldt and Paul valves.
   

   Fig 2: A, B and C: Glaucoma Drainage Device (GDD). In particular, this case featured an Ahmed valve. References: A, B: Grlica, I. 2023. C: Hospital San Juan de Dios de La Serena.
    

Cataracts

The most commonly used technique is phacoemulsification, where ultrasound is used to fragment and remove the lens. Subsequently, an acrylic or silicone intraocular lens is implanted, visible as thin hyperdense structures in CT (Figure 3) and hypointense in T2-weighted sequences (Figure 4).  

Fig 3: The thin hyperdense structure in CT replacing the lens (yellow arrow) corresponds to an intraocular lens, visible in patients who have undergone phacoemulsification for cataracts. For comparison, a normal lens is evident on the contralateral side (blue arrow). References: Hospital San Pablo de Coquimbo, Chile.

Fig 4: A: MRI of a patient who has not undergone eye surgery. B: MRI of a patient who has had bilateral cataract surgery, where intraocular lenses implants are visible as thin, low T2 signal structures (yellow arrows). References: Hospital San Pablo de Coquimbo, Chile.

Retinal Detachment

Treatment for retinal detachment includes multiple surgical options. The most used locally is the scleral buckle. Other therapeutic options are vitrectomy and retinopexy. 

1. Scleral Buckle: it involves a band or ring attached around the sclera. They can be total (360°) or segmental and are usually permanent. They can be solid silicone, hyperdense in CT, or porous silicone, visualized with gas density. (Figure 5)
   

   Fig 5: Scleral buckles for the treatment of retinal detachment. They can be made of solid silicone, hyperdense on CT scans (A, B), or porous silicone, with gas density (C). References: A, B: Hospital San Pablo de Coquimbo, Chile. C: Case courtesy of Yahya Baba, Radiopaedia.org.
    
2. Vitrectomy: it involves the removal of the vitreous from the posterior chamber. It can be replaced with sulfur hexafluoride gas (more common) or silicone oil. 

   Hydroair levels are expected in the early postoperative period of a vitrectomy with sulfur hexafluoride gas, which should not raise suspicion of infection (Figure 6).

   

   Fig 6: A, B, C: Left vitrectomy with subsequent replacement of the vitreous humor with gas, which appears hypodense on CT (yellow arrows). Over the course of several days, the gas is gradually reabsorbed until it completely resolves (blue arrow). It should not be confused with an infection or post-surgical complication. References: Hospital San Pablo de Coquimbo, Chile.
    

   Silicone oil is hyperdense on CT and should not be confused with intraocular hemorrhage or metastases. (Figure 7 and 8). Silicone typically has >100 HU, while blood has <90 HU.

   

   Fig 7: Bilateral vitrectomy with subsequent silicone oil implantation. The silicone oil is visible as spontaneously dense content within the eye globe and should not be confused with hemorrhages or metastases. It typically has a density greater than 100 Hounsfield Units (UH), while blood is usually less than 90 UH. References: Hospital San Juan de Dios de La Serena, Chile.
   

   Fig 8: Vitrectomy and subsequent silicone oil implantation in the left eye (yellow arrows), which appears hyperdense on CT (A), hyperintense in T1 and FLAIR relative to water (B, D), somewhat hypointense relative to water in T2 (C), with magnetic susceptibility artifact (E), and diffusion restriction (F, G). References: Hospital San Juan de Dios de La Serena, Chile.
    

3. Retinopexy: after this procedure, intraocular gas must be injected, so the CT image can be similar to vitrectomy, but its use is decreasing.

Others

Other surgical interventions include orbital implants for aesthetic purposes after enucleations, and eyelid implants with gold or platinum weights for the treatment of facial paralysis.

Mimics

These postoperative changes should not be confused with other expected findings secondary to aging, such as trochlear apparatus calcifications, drusen or senile scleral plaques (Figure 9).  

Fig 9: Mimics that should not be confused with postsurgical orbital changes include senile scleral plaques (A), drusen (B), and trochlear apparatus calcifications (C). References: Hospital San Pablo de Coquimbo, Chile.