Which is better: superior or temporal incisions?
In the debut of CEDARS Debates, Jonathan Solomon, MD, and Keith A. Walter, MD, make a case for the best incision for cataract surgery.
Welcome to the first issue of CEDARS Debates, a new monthly feature in Ocular Surgery News. CEDARS — Cornea, External Disease, and Refractive Surgery Society — is a group of cornea, cataract and refractive surgery specialists, here to discuss some of the latest hot topics in ophthalmology.
This month, Jonathan Solomon, MD, and Keith A. Walter, MD, discuss the merits of temporal vs. superior located incisions for cataract surgery. While many surgeons had trained using the superior incision, particularly if they trained in the era of extracapsular cataract extractions, most younger surgeons likely trained with a temporal incision. With the advent of premium IOLs and the emphasis on astigmatic correction, incision location has become more of an issue. This has also become an area of concern for surgeons who have never had to move their incision locations before. We hope you enjoy this discussion.
Kenneth A. Beckman, MD, FACS
OSN CEDARS Debates Editor
More consistent surgery possible with temporal incisions
As a former practitioner of steep on-axis incisions, I am well-versed in the arguments for superior incisions when needed to avoid orthogonal vector disarray. However, a number of advancements make strict adherence to the 90° meridian nothing more than blind dogma. First, to be clear, against-the-rule corneal incisions are no more likely to lead to endophthalmitis than similarly constructed superior incisions. Furthermore, with shrinking incision size, improved wound architecture, intracameral antibiotics and adjunctive therapy, such as the recently approved ReSure sealant (Ocular Therapeutix), concerns about wound leak conceivably could be a thing of the past.
It should also be said that when the incision is located superiorly, both gravity and blinking of the eyelid tend to create a drag on the incision, and these two forces are neutralized better when the incision is parallel to the vector of the forces. For the same reason, the inferiorly hinged LASIK flap never gained traction. Finally, it has been known for many years that incisions at 12 o’clock induce significantly more astigmatism than those made temporally and, because of their shorter radial distance from the corneal apex, may have greater impact on corneal biomechanics, in particular hysteresis.
In addition, the more acute angle of approach necessitated by working over the brow or nasal bridge lead to greater torque on the corneal incision. This coupled with the smaller vertical diameter of the cornea lead to a greater propensity for hydration of the corneal cap, leading to less reliable intraoperative verification with the aberrometer.
As surgical management of cataracts has evolved into a refractive procedure, minimizing variables and maximizing reproducibility reign supreme. Predictable refractive outcomes are only as good as our measurements, and there are many, including assessment of the posterior cornea contribution, wavefront deconstructions and intraoperative guidance systems. Limiting the location of the main incision to the temporal meridian minimizes the variability of the surgically induced astigmatism, enhancing the predictability of the final keratorefractive component. More accurate outcomes may then be anticipated when only one factor, the IOL, has to be taken into account.
In summary, by settling in the temporal meridian, I am less likely to contaminate my valuable intraoperative measurements for IOL calculation, arcuate incisions and toric IOL alignment. I am also more likely to have a consistent surgically induced astigmatism, place less stress on my surgical wound and gain range of motion in small orbits without compromising the favored location for more invasive glaucoma procedures. All the while, I have not completely given up my devotion to on-axis incision and approach with-the-rule astigmatism on the orthogonal flat axis with a nomogram adjustment, and remind myself to keep it simple.
The superiority of superior cataract incisions
Most residents are taught temporal incision cataract surgery because it is an easy place to begin, is reasonably comfortable and allows “more room” for them to work. After 20 years of doing superior incisions on my cataract patients, I have discovered numerous advantages:
By having the incision under the lid, it is out of the patient’s reach. Patients typically wipe or rub their eye by reaching for the lateral canthal area. This exposes the wound to possible contamination and, worse yet, “burping” the wound. By placing the incision under the eyelid, it becomes much more difficult for the patient to exact pressure on the wound. In addition, with respect to intraoperative floppy iris syndrome, a temporal wound with iris prolapse can denude the iris pigment epithelium, causing increased glare postoperatively as well as cosmetic defects. A superior wound in the same circumstance will more easily forgive these transgressions by being well-hidden underneath the eyelid.
2. Patient comfort
A superior wound is completely away from the blink of an eyelid, theoretically reducing postop discomfort and foreign body sensation. With an average person blinking approximately 10,000 times a day, a temporal incision can perpetuate patient discomfort as the incision heals.
3. Corneal edema
A superior incision is closer to the visual axis than a temporal incision but only by 1 mm at most, and with a 1.4 mm deep wound, it is far from inhibiting excellent early postoperative outcomes, as the wound edema is distal to affecting visual acuity.
4. Ergonomics and patient flow
Superior incisions allow my staff to maintain the same operative set-up regardless of which eye I operate. This also eases scheduling difficulties because I do not have to schedule only right eyes then left eyes or vice versa. This flexibility is particularly helpful in accommodating patient needs (eg, diabetics or transportation issues). Sitting at the head of the table allows my legs and knees to move freely without potentially moving the head by bumping the operative table. Finally, operating superiorly provides a built-in “wrist rest” by resting on the patient’s forehead, which moves with the patient as opposed to against their movements.
5. Control of astigmatism
Because most elderly patients have against-the-rule astigmatism, temporal incisions lack consistent reduction of astigmatism. Temporal incisions alone may help reduce a small amount of against-the-rule astigmatism, but larger amounts require a “paired” incision. It is impossible to really pair the temporal incision unless you make a cataract wound to match it nasally. Most surgeons who use temporal incisions make a limbal relaxing incision on the opposite side, which does not match or perform the same as their temporal wound, making it difficult, if not impossible, to accurately manage astigmatism. In order to control even larger amounts of astigmatism, the temporal incision needs to be enlarged or modified. However, by making a superior incision and knowing the exact amount of surgically induced astigmatism, I can freely make precisely paired incisions at 0° and 180° to treat against-the-rule astigmatism in a very precise manner, especially when utilizing a femtosecond laser, further justifying the use of the advanced technology to the patient.
Performing cataract surgery using a superior approach is easier than you think. Most surgeons rarely have ventured away from temporal and are intimidated by the patient’s brow or deep-set eyes. By ensuring the head is level or has a slight chin-up position, the angle of approach and exposure are similar to temporal incisions. In fact, I have never had to move to temporal once I plan to operate superior. The benefits of having an incision under the eyelid, improved patient comfort, improved ergonomics and improved astigmatism management have all worked together to provide me with consistently excellent outcomes. Because of the foregoing, I reserve temporal incisions only in the rare instance a patient has a superior corneal disease such as Terrien’s marginal degeneration. Remember, superior surgeons operate superiorly.