**3. Aiding early differential diagnosis**

Diagnosing early macular hole lesions and differentiating them from other mimicking conditions are the clinical challenges in the management of macular holes. Fluorescein angiography (FA) was the earlier imaging modality of choice to identify macular holes. Although useful in characterizing full-thickness holes, this test does not help in identifying stage 1 macular holes, which are the source of clinical dilemma. The purpose of FA was largely to demonstrate other biomicroscopically similar lesions that have classic angiographic features (e.g., choroidal neovascular membranes), thereby excluding the diagnosis of macular hole.

Optical coherence tomography, as compared to FA, provides noninvasive diagnostic imaging helping early and accurate diagnosis. At the same time, it rules out other mimicking conditions, allowing the clinician to distinguish these from pseudohole and prehole conditions in almost all instances (**Figure 5**). It has been useful in demonstrating the sequence of events leading to macular hole formation over time and has thus increased our understanding of the anatomic relations in macular holes [9–11].

**a.** Hole form factor (HFF)

**b.** Macular hole index (MHI)

**4.1. Clinical significance**

hole [10].

index.

• It is the ratio of left arm length and right arm length to the base diameter of macular

**Figure 6.** (a) Schematic representation of OCT factors; (b) HFF = (b + c)/a; (c) MHI = height/base (h/b); (d) Tractional hole

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• In a study by Ullrich et al., it was observed that if **HFF was greater than 0.9,** the macular hole closed following a single surgical procedure, whereas if **HFF was less than 0.5,** anatomical success was achieved in 67% cases. Also, **higher HFF** preoperatively was associated with **better postoperative functional outcomes**. The base or minimum diam-

• It is the ratio of hole height to base diameter (ratio of perpendicular and horizontal dimensions of the hole). It can be calculated from OCT transverse images of the macular area. • The MHI represents the **preoperative configuration** of a macular hole and is a prognostic factor for visual outcome. It was suggested that **MHI value of ≥0.5** could be used to

In a study of large macular holes (low MHI macular holes) by Kumar et al. [14], preoperative screening for low MHI macular holes was done using spectral domain OCT. In view of large base diameters and low MHI, an additional maneuver was incorporated during surgery intraoperative tapping of macular hole edges in all quadrants from the inner side. This leads to an in situ increase in perpendicular height of the macular hole compared with the base

eters were independent of the duration of the symptoms [12].

predict better postoperative outcomes [13].

**Figure 5.** (a) Lamellar macular hole; (b) pseudohole.
