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Sam Masket's studies have demonstrated convincingly that square or nearly square incisions provide the best seal and help to prevent post op hypotony. Numerous papers have made the point that postop hypotony may lead to postop intraocular infection. So I think we should all strive for square incisions. It's not necessary or even desirable to pump up the intraocular pressure in the eye to test the incision. This can give a false sense of security. A well constructed incision should be water tight at normal pressures. One can measue the intraocular pressure using the tonometer designed by Barraquer ( the one we used to use during lasik), but if you don't try to over-presurize the eye , I don't think that this is necessary. I certainly would not make a less water tight incision is eye's with ocular hypertension. Just make a good incision and don't over inflate the anterior chamber. Mike Colvard

The majority of the incisions shown in eyetube are not square and they need, as you recomend in the video, corneal hydratation. Do you recomend also in those cases ocular hypertension to close the inner valve ? 40 Mm Hg is appropriate ? What is the best method of intraoperative tonometry ?

Thanks to Dr. Colvard for extolling the virtues of the scleral incision. I have long advocated the incision that heals with fibrovascular tissue, is safer for the eye, and may induce less astigmatism. (Corneo-)scleral incisions have a lower incidence of endophthalmitis as shown in many studies. I do not find them to lengthen the case and many fewer of them require a suture. I prefer to use the keratome to make the entire incision in one pass. The major indication in my practice for clear cornea medically is in the glaucoma patient who has had or may likely require a filtering procedure.

Marcos makes a good point. Long intrastromal disections can cause optical distortion during phaco, making it more difficult to see clearly during the case.Paul Ernest's early lab studies demonstrated that in general scleral incisions are stronger than "clear corneal" incisions. In time he found that clear corneal incisions could be made more secure if the intracorneal length of the incision is equal to it's width, i.e. "a square incision". Corneal incisions that aren't square are prone to leak. Incisions with 1.5 mm of scleral dissection, however, can be made secure with less intracorneal dissection as noted below, in previous comments. MIke Colvard

i appreciate such work which is carried out for benefit of mankind. i like this techniq

Incision architecture is a key component, but what about distortion. Square, corneal or MICS are more distortion prone. What´s standard distortion? What incision stands best standard distortion? In think the best compromise for a standard surgeon is obtained with scleral, rectangular and at least 2,5Mm.

An interesting read on how Dr. Ernest tested his scleral incisions in the early days.

I agree entirely with Dr.Jones' comments. This point is now widely appreciated. These videos accompany the textbook "Acheiving Excellence in Cataract Surgery". In the text, Dr. Ernest's work is discussed in detail. Mike Colvard

A square wound with an adequate corneal component is

Generally , yes, if our goal is to reduce surgically induced astigmatism. However, if the cornea is steep vertically, I often made the external part of the scleral incision longer to increase flattening. Take care however, not to dissect the corneal flap wider than the phaco keratome or the out flow during phaco will be excessive and the chamber will be unstable during the procedure.

What is the optimum size of an incision. The smaller the better?

Dear Dr.Sumanth, Both incison types have their virtues and downsides. Corneal incisions are quicker and esthetically more pleasing. The down side is that they are not as strong as scleral incisions, must be constructed perfectly to avoid hypotony and create unpredictable astigmatic results if the are place superiorly. Scleral incisions are rock solid as long as there is a good internal corneal dissection of 1.5 mm or more, and they may be place anywhere, allowing the surgeon to operate on the steep axis even when the axis is vertical, but there's almost always a subconjunctival hemorhage, so they'll not as pretty. Mike Colvard

which incision is better scleral or corneal?

scleral incision is good for astigmatisma but most of surgeons use corneal incision for shortening operation time