"Most of the lens opacities occurring after refractive keratotomy have resulted from direct laceration of the lens at the time of a corneal perforation. This is one time when the diminutive term "microperforation" takes on a more onerous meaning. This complication was not only limited to the early 1980s when metal-bladed knives and cruder techniques were used; we are
aware of cases in the late 1980s. Direct laceration of the lens is most likely to occur when the surgeon uses new techniques or instruments that cause deeper incisions in the cornea, when the surgeon is careless or in a hurry , when the patient moves inadvertently in the midst of an incision, and during deepening incisions. Other causes of cataracts after keratotomy surgery include endophthalmitis and prolonged topical corticosteroid use."
Refractive Keratotomy, George O Waring -1992
"Topical corticosteroids are used after refractive keratotomy for three reasons: 1) to decrease the postoperative mild inflammation of the cornea, a use that can be effective with in less than a week, at which time the steroids should be stopped; (2) to enhance the effect of the surgery by presumably retarding wound healing in patients who retain normal intraocular pressure, a use that has been supported by one report"; and (3) to enhance the effect of the surgery by elevating the intraocular pressure, an effect that is clearly demonstrative on the short term , but the long-term benefit has never been documented. Surgeons should guard against the chronic use of topical corticosteroids to affect the outcome of refractive keratotomy because of the danger of optic nerve damage from elevated intraocular pressure and of the induction of posterior subcapsular cataracts."
Refractive Keratotomy, George O Waring -1992
"A small number of cases of cataract formation have been reported to date. Five followed perforation into the anterior chamber....Two cases of steroid-induced cataract formation have been reported. In each case the surgeon was attempting to enhance the effect of the surgery by inducing an IOP rise with topical steroids . It has not been shown that increasing the IOP above normal has any permanent effect on the outcome of the surgery; nonetheless, some surgeons persist in this attempt. Because of the serious side effects reported with long-term topical steroid usage, this method of "treating" undercorrection is not recommended. "
"The major vision-threatening complications of radial keratotomy have until recently been limited to case reports of endophthalmitis and cataract."
Dr Irving Schwab, Refractive Keratoplasty - 1987
CATARACT SURGERY OCULAR SURGERY NEWS U.S. EDITION March 15, 2007
Cataract surgery after radial keratotomy can be challenging
Inaccurate IOL calculations, extended postop recovery and patients’ mindset create the possibility of a difficult procedure.
Many of the patients who had radial keratotomy surgery in the ’80s and ’90s are now developing visually significant cataracts.
Because of their irregular corneas, even mild cataracts can induce visually significant aberrations at an earlier stage than would be expected for a traditional patient. This is a difficult subset of patients for many reasons: The IOL implant calculations can be inaccurate, the surgical procedure can be challenging, and the postoperative recovery can be prolonged. However, the greatest challenge is often the mindset of the refractive patient. These patients often have high demands and are frequently intolerant of residual refractive errors.
Many formulas and techniques have been described for calculating IOL power in post-radial keratotomy (RK) patients. This tells me that there is no single method that yields great results. The principal error in calculation is overestimation of the corneal power, which results in implantation of a lower power IOL and postop hyperopia. Because these patients have typically been myopic their entire lives, leaving them with residual hyperopia is particularly uncomfortable and Uday bothersome. To help prevent postop hyperopia, a more myopic result can betargeted, such as –0.75 D instead of the typical –0.25 D.
In patients with no old records, the method that I use most often to calculate corneal power was proposed by Robert K. Maloney, MD. It uses the central corneal power as measured by topography and therefore does not depend on history. The power of the cornea is a combination of the anterior corneal power and the posterior corneal power. By converting the overall central corneal power from topography back to the anterior corneal power, then subtracting the expectedposterior corneal power, we can achieve a fairly accurate estimation for our IOL calculations. This formula is:
Estimated K power = (Central K power on topography × 376/337.5) – 6.1
Because of the irregular corneas, I prefer to avoid multifocal IOLs, instead preferring single focus lens implants. Aspheric IOLs may be a particularly good choice in these patients because of their significant corneal aberrations.
Implanting a negative spherical aberration aspheric IOL can help to offset the large amount of positive spherical aberration often seen in RK corneas. In this case, I prefer the Advanced Medical Optics Tecnis IOL, as it has the best ability to offset large degrees of corneal positive spherical aberration. When the corneal aberrations are not known and a degree of irregularity and other higher order aberrations are suspected, I prefer the Bausch & Lomb SofPort Advanced Optics, as it has zero spherical aberration and is the “do no harm” IOL that will not confound the aberrations.
The RK incisions are weak and are prone to opening during surgery. Any incisions made during cataract surgery must avoid intersecting the existing RK incisions, lest they unzip and cause excessive fluid leakage during surgery. In patients with previous 8-cut RK, clear corneal incisions can be made between the existing RK incisions. (Figure 1). In patients with 16-cut or more RK, it becomes difficult to avoid the existing RK incisions unless a scleral tunnel cataract incision is used (Figure 2).
To be gentle on the weakened cornea, I prefer lower flow and a lower bottle height with a smaller phaco needle to ensure that the fluid inflow still stays greater than the fluid outflow. If the RK incisions open during surgery, be aware that there could be sudden instability and shallowing of the anterior segment, and the chance for capsule rupture is increased. At the end of these surgeries, I like to paint the entire cornea with fluorescein dye to check for any leaks, which can easily be sutured while the patient is in the operating room.
The RK incisions swell during even the gentlest cataract surgery, and this swelling can induce central corneal flattening, which results in excessive hyperopia immediately postop. These RK patients will experience fluctuations in their refractive state for many weeks after their cataract surgery, so a mild amount of initial hyperopia should not be a cause of concern. After waiting at least 6 weeks, if the patient is still significantly hyperopic, a second procedure can be performed.
Perhaps the most important issues in RK patients with cataracts are explaining to them that their IOL calculations are, at best, estimations and that their surgery and postop recovery will likely be more challenging for the surgeon and the patient.