Novel tunnel staining technique to reduce premature entry in manual small-incision cataract surgery

Abstract

Mastering manual small-incision cataract surgery (MSICS) for beginner surgeons is difficult. In the initial days of residency or training, surgeons struggle to make a proper scleral tunnel and keratome entry. It commonly results in premature entry and iris prolapse. Most of the literature has shed light on premature entry during tunnel construction by a crescent blade, whereas a significant majority of iris prolapse happens due to improper keratome entry. This novel trypan blue dye-assisted tunnel staining (TBTS) technique helps in proper tunnel demarcation which can reduce the incidence of premature entry with a keratome.

Cataract surgery is usually the first surgery any resident or trainee surgeon will perform, and in India, it commonly starts with learning manual small-incision cataract surgery (MSICS). It is difficult for beginners to understand the tunnel dimensions, internal anatomy, and its correlation with nucleus size while doing MSICS. Iris prolapse through the tunnel is one of the most common and bothersome complications in beginners. It most commonly occurs due to poor tunnel architecture. In the literature, much emphasis has been given to premature entry during tunnel construction with a crescent blade,[1,2,3,4] but very little emphasis on premature entry with a keratome.

Surgical Technique

This novel trypan blue dye-assisted tunnel staining (TBTS) technique will help beginner surgeons in assessing tunnel architecture and prevent premature entry with a keratome. It is very common to see iris prolapse, even after proper tunnel construction due to premature keratome entry. With the help of this technique, beginner surgeons develop the requisite skills for good tunnel construction and keratome entry. This will in turn reduce the incidence of tunnel-related complications in the initial days of learning as described in video.

In TBTS, once the tunnel is constructed, trypan blue dye (0.06%) is injected inside the tunnel and spread evenly by moving the cannula from right to left, leading to an evenly stained scleral tunnel [Fig. 1]. Once the tunnel is stained, the surgeon proceeds to keratome entry, making sure to enter the anterior chamber (AC) exactly at the end of the tunnel [Fig. 2a]. This line is clearly demarcated by the stained internal lip of the tunnel [Fig. 2b: black arrow].

Figure 1.

Corneo-scleral tunnel after trypan blue staining

Figure 2.

(a and b): Correct keratome entry point is well demarcated due to tunnel staining

Without tunnel staining, it is difficult to identify the correct AC entry point by the keratome. Premature entry occurs if the keratome enters the mid-tunnel [Fig. 3a]. This is easy to visualize if the tunnel is stained [Fig. 3b].

Figure 3.

(a and b): Inadvertent premature keratome entry identified easily due to tunnel staining

Discussion

Premature entry is a common complication encountered by a new surgeon in MSICS. It is essential to have a spatial orientation of tunnel architecture to avoid this complication, which is usually difficult in the initial days. Tunnel staining improves the visualization of tunnel architecture and properly demarcates the internal corneal lip.

Ideally, to prevent premature entry, the crescent blade should extend the tunnel into the cornea beyond the blue line, and the 2.8- or 3.2-mm entry keratome should make the inner lip of the incision at the extreme anterior portion of the tunnel. As the MSICS tunnels are horizontally longer than those needed for phaco, the vertical width should be more than 2.5 mm.[1] There is a paucity of literature highlighting the importance of a proper keratome entry site in MSICS.

Conclusion

In conclusion, the TBTS technique is beneficial for new surgeons to get an idea of the tunnel architecture and reduce the incidence of premature entry with keratome and in turn reduce associated complications. This technique would help surgeons in the early stages of training.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.