Microwash or macrowash technique to maintain a clear cornea during cataract surgery

Abstract

 

We describe a technique of irrigating and thereby rapidly and effectively clearing the cornea of relatively large amounts of surface contaminants that reduce surgical visibility and may contribute to endophthalmitis. This technique is referred to as “macrowash.” If the technique is required, it is usually at the commencement of cataract surgery, immediately after placement of the surgical drape. The technique not only saves time, but also reduces the volume of irrigating solution required by the “microwash” technique, which is traditionally carried out by the scrub nurse/surgical assistant using a Rycroft cannula attached to a 15 mL container of irrigating solution.

Financial Disclosure: 

No author has a financial or proprietary interest in any material or method mentioned.

The clarity of the surgeon's field of view during cataract surgery depends significantly on the amount of debris, mucus, and oil present on the cornea and the severity of corneal drying. Surface contaminants, including oil, fragments of conjunctival mucus, and other debris, usually derived from the lids, frequently circulate on the corneal surface at the commencement of cataract surgery, despite high quality draping. There is always a concern that as a result of surface contaminants, and despite exclusion of the lids, surface infection or wound contamination might subsequently occur.¹ We have described improved surgical draping techniques² that may minimize the presentation of large amounts of surface contaminants early in the course of surgery. Large amounts of surface contaminants may result in wound infection,¹ and entry of these contaminants may result in endophthalmitis. Indeed, the organisms that most commonly cause endophthalmitis are derived from the eyelid margin and preocular tear film.³

TECHNIQUE

During our 36 years of performing surgery, up to late 2008, surface contaminants, whether in small or large amounts, were dealt with by repeated irrigation with a 27-gauge Rycroft cannula or similar instrument (#OP6211, Alcon, Inc.) attached to a 15 mL container of irrigating fluid. This “microwash” technique (Figure 1) sometimes used the entire 15 mL container of balanced salt solution (BSS, Alcon, Inc.), frequently without ridding the cornea of surface contaminants.

Figure 1: In the traditional microwash technique using the fine corneal irrigating cannula, there is little apparent fluid movement. This technique is effective for small quantities of surface contaminants and works within seconds of irrigation. Note that the fine-toothed forceps is about to fixate the eye at the 4 o'clock position, with the 2.2 mm incision blade poised to make the incision. The aim is to rid the corneal surface of surface contaminants before making the definitive main-port incision.

Recently, it was noted that by removing the cannula from the irrigating container and irrigating the cornea and surrounding tissue with a relatively high-volume flow of BSS, the ocular surface was immediately cleared of large amounts of surface contaminants. This is referred to as a “macrowash” technique (Figure 2). Both techniques are demonstrated in the video (available at http://jcrsjournal.org).

Figure 2: Macrowash showing multiple large fluid waves that assist in rapidly clearing large volumes of surface contaminants with relatively small volumes of BSS.

Some colleagues report that a macrowash can also be achieved by using the open end of the irrigating cannula of the phacoemulsification system, with the irrigating system under surgeon foot control or with a large bore Rycroft cannula.

DISCUSSION

The method we describe has at least 4 advantages:

1. Our method allows the operator the flexibility to use macrowash or microwash simply by temporary removal/replacement of the Rycroft cannula.
2. For most surgery, microwash with a 27-gauge Rycroft is preferable to a large bore Rycroft because it interferes less with the surgeon's field of view during irrigation and generally eliminates surface contaminants effectively.
3. Large amounts of fluid irrigation can be wasteful and unnecessary in the context of the more common types of surface contaminants, which are easily eliminated.
4. To use the phaco or irrigation/aspiration cannula to irrigate the cornea means the instrument has to be removed from the eye, which is counterproductive to operating time and could be associated with repeated wound trauma.

Ophthalmic viscoelastic devices (OVDs) are reported to be beneficial in managing severe corneal drying intraoperatively.^A However, we have found that using OVDs can impair surgical visibility and that microwash adequately maintains good corneal clarity and possibly minimizes the risk for infection. Clearly, the microwash, or the macrowash when needed, is a more economical option than using OVDs.

Given that postoperative endophthalmitis ultimately involves the introduction of an offending agent through the corneal incision,³ which can occasionally occur at the time of surgery, it seems appropriate to use every reasonable modality to minimize this. We believe that when a microwash fails to clear the cornea of surface contaminants despite being repeated once or twice, a macrowash may be an effective method. We therefore recommend this technique to our surgical colleagues.