**5. Intraoperative OCT (iOCT)**

diameter, thus translating to an intraoperative increase in MHI and facilitating hole closure. This was done along with other surgical modifications including a large arcade to arcade ILM peel and removing any ERM associated with it. An improvement in the postoperative visual

Thus, OCT not only facilitates an accurate diagnosis, but preoperative surgical planning

Another surgical technique proposed for large macular holes, to improve anatomic and functional outcomes of surgery by *preventing postoperative flat-open configuration* of macular holes, is the inverted ILM flap technique [15]. In this technique, after core vitrectomy and dye staining, the ILM is not completely removed from the retina but is left in place, attached to the edges of the MH. This ILM remnant is then inverted to cover and fill the MH (**Figure 7**). The rationale for tissue repair that occurs following the use of this technique is: the inverted ILM, containing Muller cell fragments, induces glial cell proliferation, resulting in the macular hole filling with proliferating cells that enhance closure. It also works as a scaffold for tissue proliferation, creating a microenvironment that encourages correct photoreceptor alignment. This allows a near-perfect anatomic restoration, *with OCT demonstrating restoration of normal foveal architecture*. Hence, this technique results in better postoperative anatomic and

Also, because ILM is a basement membrane, it allows glial cell proliferation, allowing large

• It is the ratio of minimum diameter of MH to base diameter and is an indicator of extent

• It is the ratio of maximal height of MH to minimum diameter and is an indicator of AP

Patients with higher THI values (>1.41) and low DHI values (<0.50) had the best post-op

As an increasing number of surgeons opt for ILM peeling to facilitate hole closure, vital dyes have become useful tools for the membrane and ensuring its complete removal [18]. Also, mixtures of dyes with high-density dextrose or polyethylene glycol (PEG) solution have improved the staining of the macula [19]. These high-density solutions when combined with the dye promote immediate settling of the dye onto the macula and minimize its dispersion

With the availability of several dyes and formulations, concerns regarding chemical or phototoxicity are always expressed. Hence, the need to develop new methods to enhance the visualization of the ILM. One example is the use of intraoperative optical coherence tomography (iOCT), which has the potential to visualize the ILM during vitrectomy with immediate

MHs to fill with tissue over time further expanding its use to repeat MH surgery [16].

outcome was observed with large macular holes with MHI as low as 0.25.

functional outcome.

88 OCT - Applications in Ophthalmology

**c.** Diameter hole index (DHI)

of tangential traction.

traction and retinal hydration.

**d.** Tractional hole index (THI)

VA recovery [17].

throughout the vitreous cavity.

surgical feedback.

based on OCT factors also helps in improving anatomic and functional prognosis.

OCT is fundamental to our clinical decision-making for management of macular holes. It has now been incorporated as intraoperative OCT (iOCT)—supplementing surgical assessments in the operating room and guiding surgical decisions.

Intraoperative OCT consists of spectral domain optical coherence tomography (SD-OCT) on an OCT-mounted surgical microscope. It identifies intraoperative changes in the macular anatomy and provides additional information to predict visual outcomes of macular surgery. The SD-OCT scan taken immediately after ERM removal identifies a cleavage plane for the subsequent ILM peeling, allowing an accurate ILM peel causing minimum disruption of retinal architecture [20].

Intraoperative OCT has been described in several types of retinal surgeries, including vitrectomy for the macular hole. During membrane peeling, the surgeon's impression of membrane peel completeness conflicted with iOCT data in 19% of cases (e.g., iOCT displayed a persistent occult residual membrane or showed lack of residual membrane). For posterior segment surgery, it has been reported that the use of iOCT provided valuable feedback in 71% (97 of 136) of cases.

It has been noted in various studies that photoreceptor integrity is the best prognostic factor

Optical Coherence Tomography: Essential Tool in Macular Hole Management

http://dx.doi.org/10.5772/intechopen.79279

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Analysis of the inner HRL (hyperreflective layer) allows a better understanding of the outcomes of macular hole surgeries. It has been seen that anatomic success with restoration of foveal contour does not always translate to improved postoperative visual acuity. Irregularities at the level of the inner HRL after macular hole surgery may prevent visual acuity improvement. On the other hand, improvement in BCVA has been noted with IS/OS

**b.** Foveolar gaps (lucencies) are a common occurrence post MH surgery. Conservative treatment with patient reassurance is the treatment of choice as has been demonstrated by

**c.** Macular hole closure can be observed ophthalmoscopically 9–10 days after gas injection.

• type 1 closure (closed without foveal neurosensory retinal defect) and type 2 closure (closed with foveal neurosensory retinal defect) (**Figure 9a**) [25]. The extent of postoperative visual improvement of type 1 closure group was larger than that of type 2 closure group. Also, only type 2 closure was associated with recurrence of the pathology. Thus, the postoperative visual prognosis directly correlated to the type of hole closure, which

In another study by Imai et al. [26], OCT images of repaired macular holes were catego-

The closed macular holes have been variously classified based on OCT

in turn was seen to correspond to the preoperative hole diameter [25].

**Figure 9.** Types of macular hole closure on (a) OCT-Kang et al. [25] and (b) OCT-Imai et al. [26].

junction normalization in the postoperative period [23].

serial OCT follow-up (**Figure 8**) [24].

• Elevated/open

• Flat/open and flat/closed anatomic closure

rized into three patterns (**Figure 9b**).

for VA.

The use of iOCT, being in its early stages, has certain limitations—real-time membrane peeling using metallic instruments creates absolute shadowing. Despite this drawback, it is still useful in visualizing tissue-instrument interactions, revealing residual membranes, and confirming completion of surgical objectives in macular surgery [21, 22].

This new modality will help improve anatomic and visual outcomes by helping the surgeon ensure completeness of surgical intervention and at the same time minimizing tissue manipulation.
