Scleral indentation is a technique used to examine the peripheral fundus in conjunction with binocular indirect ophthalmoscopy (BIO). Slight pressure applied to the sclera, enables the ophthalmologist to examine the peripheral fundus.
Medical Use or Purpose
Scleral indentation allows the inward displacement of tissue, enabling the peripheral fundus to be viewed in profile. It enhances the contrast between the normal and abnormal retina and changes the perspective with which an ophthalmologist views the retina. The technique also enables stereoscopic examination of the peripheral retina.
For example, it is easier to view retinal abnormalities like tears, holes, lattice, breaks, and vitreoretinal adhesions, using scleral indentation. Other conditions that can be viewed include:
- High axial myopia
- Blunt trauma history
- Retinal detachment symptoms
- Peripheral retina abnormalities
Research indicates that scleral indentation can help remove the peripheral vitreous or intraocular foreign body (IOFB), where the pars plana and ciliary body process are brought into view. The method allows direct visualization to extract a foreign body lodged at or near the ciliary body. However, if the foreign body is located behind the ora serrata, then scleral indentation may not be of help. The technique may also not be useful in recent intraocular surgery, recent hyphema, and a ruptured globe.
Risks & Complications
Some of the risks and complications associated with scleral indentation include pain, which can be caused when the tarsal plate gets depressed. Pain can also manifest when the depressor presses excessively toward the globe and is not placed tangential to the globe.
Another risk is the examiner being unable to visualize the depressor. Failure of the depressor to be aligned to the examiner's head and the patient's gaze presents another risk. Besides, complications may arise if the depressor is not placed in an accurate location, at least 7-14 mm behind the limbus. Failure by the ophthalmologist to view out to or near the ora serrata can be a risk.
Corneal perforation is a complication that can arise from scleral indentation necessitating further treatment such as the use of cyanoacrylate glue and placement of a bandage contact lens. Corneal perforations can lead to further complications like a deepening anterior chamber with iris incarceration. A tectonic full thickness keratoplasty can follow to correct the complication. Loss of anterior chamber stability, application of corneal glue, and use of tectonic full-thickness keratoplasty can lead to even more complications like cataract, raised intraocular pressure, and inflammation. This makes visual rehabilitation difficult.
Scleral indentation can increase IOP to high levels so that retinal function is affected. A drainage valve may then need to be implanted to help lower IOP that does not respond to medication. Elevated IOP may result from scleral buckling and vitreous surgeries due to the immense pressure exerted to bring the peripheral retina into view. Elevated pressure can result in more adverse effects such as vitreous hemorrhage, ganglion cell damage, expulsive choroidal hemorrhage, retinal ischemia, and choroidal detachment. The most affected eyes are myopic, glaucoma, and those which are injured.
Preparation & Expectation
A complete medical and ophthalmic examination is conducted. The medical history of the patient is also taken. The surgeon explains the details of the procedure, including the risks, complications, and benefits.
Scleral indentation utilizes a scleral depressor which comes in different designs such as a double-ended flat, thimble, or cotton-tipped swab. Additionally, a topical ophthalmic mydriatic solution is used. The surgeon determines which instrument will best serve the purpose. For instance, some surgeons may opt to use the thimble depressor because it enables more freedom for manipulation of the lids. Other surgeons find the cotton-tip applicator easier to use, although it is more challenging to move across the eyelids. A recent addition to the list of instruments includes the Josephberg-Besser scleral depressor, which has a wider, curved blade.
Procedure or Steps Involved
The patient is prepared and placed in a reclining position after which the surgeon:
- Ensures there is maximal pupillary dilation
- Performs a BIO in the area of interest
- Holds a depressor with the leading hand and places it on the furrow of the eyelid
- Requests the patient to unhurriedly look in the depressor’s direction. The surgeon allows the depressor’s tip to follow the patient’s eye back into the orbit
- Ensures the patient’s eye and the examiner’s eyes lie along the same axis at 180 degrees away from the depressor and patient’s gaze
- Puts condensing lens in position to enable a view of the retina
- Applies gentle pressure on the depressor
Scleral indentation is an effective method that makes visualization of the periphery fundus possible. It also helps to expose an IOFB for easier extraction. The IOFB is extracted with less surgical time, better surgical outcomes, and quicker recovery.