MANAGEMENT OF ASTIGMATISM

IN CONJUNCTION WITH

CLEAR CORNEAL PHACO SURGERY

Louis D. “Skip” Nichamin, M.D.

Medical Director Laurel Eye Clinic, Brookville, PA

Improved spherical and astigmatic outcomes are now well-recognized benefits of

modern small incision cataract surgery. In fact, the term “refractive cataract surgery” no

longer simply engenders a shift in philosophy, but rather has come to represent a reality

for our cataract patients. An increasing number of refractive surgical patients may in fact

fare better with refractive lensectomy surgery than they might with “standard”

keratorefractive procedures.

Incision Decisions

During the early and mid 1990’s, a great deal of effort was directed toward the

study of the astigmatic effects of various cataract incisions. By manipulating incision

parameters (size, location, and shape) surgeons could, with a reasonable level of

accuracy, “tailor” their astigmatic outcome according to the patient’s preexisting

astigmatism. This on-axis, variable incisional approach does, however, require effort

rotating about the operating room table, a dynamic mindset, and to some degree varying

instrumentation. Although effective, recent advances in incisional technique and implant

technology have led to a different approach in managing astigmatism during

phacoemulsification (phaco) surgery. Specifically, the temporal clear corneal phaco

incision, as popularized by Dr. Howard Fine, has now proven itself to be safe, effective,

and remarkably reproducible. Additionally, as a result of improvements in foldable

2

intraocular lens (IOL) delivery systems, implantation may now be routinely performed

through incisions of 2.8-3.2 mm.

Well-documented studies now support the clinical impression that incisions of

this size behave in an essentially astigmatically neutral fashion1,2

. Thus, an incision may

now be easily and reproducibly crafted that yields all of the wonderful benefits of the

clear corneal approach, yet is astigmatically neutral. If a patient has enough preexisting

astigmatism to warrant reduction, then additional surgery may be superimposed,

concurrently or at a later time, upon this temporal clear corneal phaco incision. Today,

this most commonly takes the form of (intra-) limbal peripheral arcuate astigmatic

relaxing incisions or “LRI’s.” Other options include toric implants or a “bioptics”

approach utilizing excimer or other non-laser technology to enhance the refractive

outcome (please see following handout).

The use of peripheral arcuate astigmatic relaxing incisions or “LRIs” has been

shown to be extremely safe and reliable.3 In the setting of concomitant lens surgery, our

data indicate that this technique provides for more predictable astigmatic outcomes as

compared to the use of conventional (smaller) astigmatic keratotomy (A.K.) optical

zones, and yields more consistent results than when relying solely upon a “tailored”

phaco incision.4

Our use of LRIs originated from the work of Dr. Stephen Hollis. With refinement

of his nomogram, we found this approach to astigmatic management to be considerably

more forgiving with less induced shift of resultant cylinder axis, greater predictability,

and perhaps most importantly, less tendency to induce irregular corneal flattening and

hence irregular astigmatism. Admittedly, these more peripheral incisions are less

powerful than conventional corneal relaxing incisions; however, in treating cataract and

presbyopic-aged patients, more effect may be achieved in this older population and one

3

must keep in mind that the goal is to reduce preexisting astigmatism without

overcorrecting or shifting the axis. In fact, many refractive surgeons now prefer use of

longer intralimbal arcuate incisions in all astigmatic keratotomy candidates irrespective

of age.

Another advantage gained by moving out to the limbus involves the “coupling

ratio” which describes the amount of flattening that is induced in the incised meridian

relative to the amount of steepening that occurs 90° away. LRIs exhibit a very consistent

1:1 ratio, and therefore negligible change in spheroequivalent occurs obviating the need

to adjust the IOL power. Finally, this form of intralimbal keratotomy seems to logically

dovetail with the trend toward clear corneal phaco incisions. In summary, we start with

the amazingly simple but elegant single-plane, temporal (neutral) clear corneal phaco

incision, and then add on to the steep meridian, the necessary nonbeveled (perpendicular

to the corneal surface) limbal arcuate relaxing incisions. This makes for a facile, logical

and esthetic approach to astigmatism management.

The Surgical Plan

In creating a surgical plan, it is generally agreed that mild residual with-the-rule

astigmatism is desirable (when using monofocal IOL’s), overcorrection (axis shift of

180°) is undesirable, and that the refractive plan must take into account the status of the

fellow eye. With this in mind, surgery is planned according to the nomograms as

illustrated (Tables I & II). Unfortunately, preoperative measurements—keratometry,

refraction, and topography—do not always agree. Lenticular astigmatism may account

for some of this disparity; however, our experience supports the notion that traditional

measurements of astigmatism, particularly those obtained with standard keratometry

(only 2 points measured in each meridian) do not always adequately quantitate the

4

amount of astigmatism present. We have found that keratometry generally provides an

accurate determination of axis and that refraction, presuming that the cataract is not

extremely dense, provides a more reliable indicator of the quantity of cylinder. When

confounding measurements do arise, one can compromise and average the disparate

readings, or simply defer the relaxing incisions until a stable postoperative refraction is

obtained since this technique lends itself nicely for in-office “touchups.” We have come

to increasingly rely upon corneal topography, particularly when measurements do vary

and in complex cases. Once the amount of astigmatism to be corrected has been

determined, the nomogram is used by aligning the age and preop cylinder columns.

Incisions are typically paired to optimize symmetric corneal flattening and expressed in

degrees of arc rather than millimeters since corneal diameter may significantly impact the

relative length of the arcuate incision and its resultant effect (Fig. 1).

These nomograms may be used in conjunction with any modern phaco incision

including scleral tunnels, but one must know the exact astigmatic effect of the cataract

incision and factor this into the surgical plan. As mentioned, it is our preference to

perform surgery through a 2.5 mm. to 2.8 mm temporal clear corneal incision, depending

upon the tip and sleeve combination, and it is then enlarged to 2.8 to 3.2 mm to

accommodate the particular foldable IOL. This single plane, paracentesis-style temporal

incision is placed at or just anterior to the vascular arcade. If a larger incision is to be

used (to accommodate a particular IOL), increased against-the-wound drift (with-the-

rule, given temporal incision location) must be anticipated and factored into the amount

of cylinder to be corrected. As seen in the nomogram, for patients with negligible

preexisting astigmatism, the single plane phaco incision alone is employed. For patients

with minimal against-the-rule astigmatism, a nasal peripheral arcuate relaxing incision is

placed opposite to the temporal clear corneal phaco incision. As the amount of against-

5

the-rule cylinder increases, a temporal arcuate incision is paired with the nasal incision to

create symmetric flattening in the horizontal meridian. The temporal cut, in essence,

becomes a deep groove such that the incision architecture resembles the Langerman

Hinge5 with the extent or length of the groove determined by the nomogram).

For with-the-rule astigmatism, the surgeon has two choices. There is varying

opinion regarding the use of superior clear corneal incisions. Many leading surgeons

fully advocate their use. One must keep in mind that these superior incisions will drift

against the wound more than temporal incisions, as noted by Dr. Harry Grabow and

others. In nearly all cases of with-the-rule astigmatism, I personally prefer to keep the

phaco tunnel situated temporally, maintain an incision size of 3.5 mm. or less for

neutrality, and apply LRIs over the steep vertical axis. In my experience, the latter

approach has yielded more consistent results with less corneal edema, particularly in

those patients who have short eyes with small corneal diameters, are deeply set, or those

who have compromised endothelium. A final planning note for patients who have with-

the-rule astigmatism, the side-port incision location may need to be adjusted so as not to

interfere with the intralimbal relaxing incision.

Surgical Technique

When?

It is reasonable to place all relaxing incisions at the conclusion of surgery, in the

event that a complication necessitates a modification to the phaco incision. For routine

cases, however, I prefer to place these incisions at the outset in order to avoid epithelial

disruption. One exception would be in the case of high against-the-rule astigmatism

wherein the nomogram calls for a temporal arcuate incision of greater than 40°. Since

this incision or “deep groove” will be superimposed upon the phaco tunnel, if it is

6

extended to its full arc length at the start of surgery, significant gaping and edema may

result secondary to intraoperative manipulation. In this situation, the temporal incision is

made by first creating a two-plane, grooved phaco incision (600 micron depth), which is

then extended to the full arc length, as determined by the nomogram, at the conclusion of

surgery. The nasal arc may be extended to its full arc length at the beginning of the case.

Note that the keratome used for the phaco tunnel is inserted through the temporal LRI by

pressing the bottom surface of the blade downward upon the outer or posterior edge of

the LRI, and then advancing the keratome at an iris-parallel plane. This angulation will

allow the keratome to enter at mid-stromal depth.

Where?

Most surgeons advocate placing an orientation mark at the 12:00 or 6:00 limbus

before adopting the supine position. This is particularly important when utilizing

injection anesthesia. In either event, to help identify the steep meridian (plus cylinder

axis) intraoperative keratoscopy is highly recommended. The steep meridian over which

the incisions are centered corresponds to the shorter axis of the corneal mire as reflected

by the keratoscope. A simple hand-held device such as the Maloney (Katena, Storz and

others) works well, or a more elaborate microscope-mounted device may be employed

such as the Mastel Ring of Light. The steep meridian may also be identified by aligning

a Mendez Ring or similar degree gauge with the previously placed 12:00 or 6:00 limbal

orientation marks.

The LRIs are placed at the most peripheral extent of clear corneal tissue, just

inside of the true surgical limbus, irrespective of the presence of vessels or pannus. If

bleeding is encountered, it may be ignored and will stop spontaneously. Care must be

taken not to place the incisions out at the true (gray-to-blue) surgical limbus in that a

significant reduction in effect will occur. An empiric blade depth setting of 600 microns

7

is used in the setting of concomitant cataract surgery. Prior studies employing

pachymetry and adjusted blade settings yielded negligible benefit in this older population,

as opposed to younger refractive surgery patients where variable blade depth settings are

justified along with a slightly more aggressive nomogram (see NAPA Nomogram, Table

I). Diamond blade style and configuration may require an adjustment in depth settings;

in my experience, a triple-edged 15° Thornton Arcuate Diamond set at this depth has

yielded excellent results with no perforations. My personal preference is for a new

diamond blade solely dedicated to this technique (Mastel). A single arced footplate

improves visibility and the diamond extends to the appropriate (600 micron) preset depth

(Fig. 2). Similar designs are available from Rhein Medical, ASICO and other companies.

The extent of arc to be incised may be demarcated in several different ways. My

preferred method makes use of a specially designed Fine-Thornton Fixation Ring that

both fixates the globe and allows one to delineate the extent of arc by visually

extrapolating from the limbus to the adjacent marker (Mastel Precision, Rhein Medical

and Storz). Each incremental mark is 10° apart, and bold hash marks (180°) apart serve

to align with the steep axis. This approach avoids inking and marking of the cornea. If

desired, a two-cut R.K. marker may be used to mark the exact extent of arc to be incised

in conjunction with the fixation ring/gauge (Fig. 3). Alternatively, various press-on

markers are available, such as those made by Rhein Medical (Nichamin-Kershner LRI

Markers or the Dell Marker).

Increased Comfort for Patient and Doctor

Interestingly, one of the most common patient complaints following

contemporary phaco surgery is that of a foreign body sensation. Intralimbal relaxing

incisions, as compared to more central corneal incisions (smaller optical zones),

8

definitely improve patient comfort. With the addition of a postop topical NSAID, this

problem is virtually eliminated. Upon examination, these incisions appear to heal quickly

and are nearly unidentifiable within several days.

Potential Complications

As previously noted, LRIs are proving to be a safer and more forgiving approach

to treating astigmatism as compared to more central corneal incisions. Nonetheless,

potential for problems will always exist, and several are listed in Table III. Of these,

operating upon the wrong axis is likely to be the most common error experienced. When

this complication is encountered, it typically takes the form of a 90º mistake with the

incisions being centered upon the opposite, flat meridian. This, of course, leads to an

increase and probable doubling of the patient’s preexisting cylinder. Compulsive

attention is needed in this regard, with safety checks such as clear written plans being

available within the OR for reference. Incisions are placed upon the plus (+) cylinder

axis, and opposite to the minus (-) cylinder axis.

Conclusion

Our experience utilizing peripheral, intralimbal arcuate relaxing incisions over the

past decade has paralleled that of many other surgeons, and serves to substantiate this

technique as being a safe, effective and reproducible means by which both congenital and

surgically induced astigmatism may be treated.

Once again acknowledgment is given to Dr. Stephen Hollis of Columbus, Georgia

whose original work provided the platform for this technique, and to Dr. Spencer

Thornton who has contributed so much to astigmatism surgery and whose modifiers are

incorporated into our current nomograms.

9

References:

1. Lyle WA, Jin G. Prospective evaluation of early visual and refractive effects with

small clear corneal incision for cataract surgery. J Cat Refract Surg 1996; 22:1456-

1460.

2. Masket S, Tennen DG. Astigmatic stabilization of 3.0 mm. temporal clear corneal

cataract incisions. J Cat Refract Surg 1996; 22: 1451-1455.

3. Budak K, Friedman NJ, Koch DD. Limbal relaxing incisions with cataract surgery.

J Cat Refract Surg 1998; 24:503-508.

4. Nichamin LD. Changing approach to astigmatism management during phaco-

emulsification: peripheral arcuate astigmatic relaxing incisions. Presented at the

ASCRS Meeting, May 2000, Boston, MA.

5. Langerman DW. Architectural design of the self-sealing corneal tunnel single-hinge

incision. J Cat Refract Surg 1994; 20:84-88.

10

Figure 1

11

Figure 2

Figure 3

12

Table I The “NAPA” Nomogram

Nichamin Age & Pach-Adjusted Intralimbal Arcuate Astigmatic Nomogram

Louis D. “Skip” Nichamin, M.D.

“WITH-THE-RULE”

PREOP CYL (Diopters)

Paired Incisions in Degrees of Arc 20-30 yo 30-40 yo 40-50 yo 50-60 yo

0.75 40 35 35 30

1.00 45 40 40 35

1.25 55 50 45 40

1.50 60 55 50 45

1.75 65 60 55 50

2.00 70 65 60 55

2.25 75 70 65 60

2.50 80 75 70 65

2.75 85 80 75 70

3.00 90 90 85 80

“AGAINST-THE-RULE”

PREOP CYL (Diopters)

Paired Incisions in Degrees of Arc 20-30 yo 30-40 yo 40-50 yo 50-60 yo

0.75 45 40 40 35

1.00 50 45 45 40

1.25 55 55 50 45

1.50 60 60 55 50

1.75 65 65 60 55

2.00 70 70 65 60

2.25 75 75 70 65

2.50 80 80 75 70

2.75 85 85 80 75

3.00 90 90 85 80

*When placing intralimbal relaxing incisions following or concomitant

13

with radial relaxing incisions, total arc length is decreased by 50%

Table II NOMOGRAM

FOR

CLEAR CORNEAL PHACO SURGERY

Louis D. “Skip” Nichamin, M.D. Laurel Eye Clinic, Brookville, PA

♦ ASTIGMATIC STATUS = “SPHERICAL”: (+0.75 X 90 +0.50 X 180)

Incision Design = “Neutral” temporal clear corneal incision (3.5 mm. or less, single plane, just anterior to vascular arcade)

♦ ASTIGMATIC STATUS = “AGAINST-THE-RULE”: Steep Axis 0-30° / 150-180°):

Intraoperative keratoscopy determines exact incision location

PRE-OP CYLINDER 30-40 yo 41-50 yo 51-60 yo 61-70 yo 71-80 yo 81-90 yo > 90

nasal limbal arc only

+0.75 → +1.25

*paired limbal arcs

on steep axis

55°

50°

45°

40°

35°

35°

*paired limbal arcs

+1.50 → +2.00 on steep axis

70°

65°

60°

55°

45°

40°

35°

*paired limbal arcs

+2.25 → +2.75 on steep axis

90°

80°

70°

60°

50°

45°

40°

*paired limbal arcs

+3.00 → +3.75 on steep axis

↓ o.z. to 8 mm

90°

↓ o.z. to 9 mm

90°

85°

70°

60°

50°

45°

degrees of arc to be incised

Table II

♦ASTIGMATIC STATUS = “WITH-THE-RULE”: (Steep Axis 45°- 145°):

Intraoperative keratoscopy determines exact incision location

Incision Design = “Neutral” temporal clear corneal along with the following peripheral arcuate incisions:

PRE-OP CYLINDER 30-40 yo 41-50 yo 51-60 yo 61-70 yo 71-80 yo 81-90 yo >90 paired limbal arcs

+1.00 → +1.50 on steep axis

50°

45°

40°

35°

30°

paired limbal arcs

+1.75 → +2.25 on steep axis

60°

55°

50°

45°

40°

35°

30° paired limbal arcs

+2.50 → +3.00 on steep axis

70°

65°

60°

55°

50°

45°

40° paired limbal arcs

+3.25 → +3.75 on steep axis

80°

75°

70°

65°

60°

55°

45°

degrees of arc to be incised

TABLE III

___________________________________

Potential Problems

• Infection

• Weakening of the globe

• Perforation

• Decreased corneal sensation

• Induced irregular astigmatism

• Misalignment/axis shift

• Wound gape and discomfort

• Operating upon the wrong (opposite) axis!

___________________________________

Bioptics for the Pseudophakic Patient

Refining the refractive outcome following intraocular lens surgery has arguably

become the most pressing challenge facing the cataract surgeon today. Patients

increasingly expect early and excellent uncorrected visual acuities, and the refractive

“surprise” has become one of the most common causes for litigation following cataract

surgery.1 Indeed, the borders separating the fields of cataract and refractive surgery have

all but faded, as intraocular lens surgery has become an important alternative, in

appropriate cases, to that of standard keratorefractive procedures.

Recent advances in surgical technique and technology have significantly improved

refractive outcomes. These would include the use of intralimbal relaxing incisions and

toric IOLs to address preexisting astigmatism, and improved accuracy in measuring axial

lengths with partial coherence interferometry thereby permitting more accurate IOL power

selection. Nonetheless, we must seek ways to further enhance the refractive predictability

of our surgery.

Recently, Zaldivar has described a technique to treat high levels of myopia that he

has termed bioptics.2 Guell and coworkers have reported a similar technique.

3 In this

approach, the patient first receives bilateral LASIK flaps without ablation, then undergoes

myopic phakic IOL surgery which is subsequently enhanced by raising the flaps and

ablating for the residual refractive error. This combined approach for the high myope has

several advantages. Preoperatively, phakic IOL power calculation is hampered by the

inherent difficulty in obtaining an accurate refraction in the very high myope due in part to

their minified image and vertex distance considerations. Following placement of the

phakic IOL and reduction of the myopia to a more modest level, a more accurate refraction

may be obtained, and then refined through the use of LASIK.

Furthermore, this combined strategy avoids deep excimer ablations reducing the

risks of ectasia, glare and halos, and other aberrations that occur secondary to the induced

oblate state of the cornea. One thus corrects the majority of the refractive error by means

of a lenticular procedure (in this original scenario by utilizing a myopic phakic implant)

and then refines the refractive outcome with LASIK.

Recently, we have begun to incorporate this bioptics approach into the surgical

protocol of our pseudophakic patients. Our experience began with refractive lensectomy

candidates where precise refractive outcomes were a must. Not long thereafter, we began

to offer this option to select cataract patients, particularly younger patients and those

receiving multifocal IOLs.

Prior to instituting bioptics, 10-15% of our refractive lensectomy patients were

bothered by residual refractive error and many of these individuals required further

intervention, typically secondary piggyback IOL placement into the ciliary sulcus for

residual spherical error, and/or additional intralimbal relaxing incisions for symptomatic

astigmatism. By utilizing the excimer laser as an enhancement tool, we now can avoid

further intraocular manipulation and its attendant risk, and exploit the remarkable precision

that this technology offers. Intralimbal relaxing incisions have been a wonderfully

effective way to manage preexisting astigmatism, but are simply no match for the accuracy

that is obtainable with the laser. The small amount of ablation that is typically required

poses little risk of ectasia, glare, halos or other aberrations that may be associated with

excimer treatment.

Our initial protocol was similar to that of Zaldivar’s. We first would perform

bilateral conventional LASIK flaps, followed several weeks later by unilateral, sequential

implant surgery. The several week delay between the flap and implant procedures allowed

us to confirm that no flap-related problems had occurred and to repeat corneal

measurements to rule-out flap-induced change. Once a stable refractive result was

documented following the IOL surgeries, as necessary, the flap(s) were raised manually

and ablation was performed if symptomatic residual refractive error persisted.

More recently, we have begun to perform both the microkeratome cut and laser

ablation together, if required, 2-3 months after the IOL procedures. This has eliminated

the creation of many unnecessary flaps.

There are, however, new challenges that arise with this technique. First, not all

implant surgeons have ready access to an excimer laser. In addition, this service would, of

course, not be covered by insurance and therefore requires out-of-pocket expense for the

patient. Most importantly, additional surgery is being performed with additional

associated risks.

When first discussing this option with prospective patients, we were surprised at

the willingness they showed to pursue this option, perhaps due to the increased awareness

of refractive surgery and in particular LASIK. In our experience, most refractive

lensectomy patients are willing to pay a premium to obtain heightened accuracy, and a

surprising number of cataract patients, particularly younger and more active individuals,

opt for this more costly approach.

A true concern, however, is the potential for added risk. All of the stand-alone

problems associated with LASIK must now be considered. In regard to cataract patients,

we are now dealing with an older population and a higher incidence of epithelial-related

flap problems must be expected, along with dry eye complications. Other potential

denervation-related issues must also be entertained. Additionally, biomechanical changes

that the cornea sustains from the creation of the flap are still not completely understood.

Because of these concerns, it may be that LASEK or even surface ablation will prove to be

a better alternative to that which is currently being employed.

Similarly, other non-laser modalities may be utilized in this bioptics approach.

Although laser thermal keratoplasty would seem to be falling out of favor at this time,

conductive keratoplasty, i.e., may hold promise as being a way to simply and safely treat

residual hyperopia as well as mixed and hyperopic astigmatism.

We are following closely and collecting data on all of our pseudophakic bioptics

patients. Pop and coworkers have reported good results on a series of hyperopic clear

lensectomies that received LASIK as an enhancement procedure.4 A small group of

surgeons including, but not limited to A. Hatsis of Rockville Centre, NY and J.J. Arroyo

from Manila, are also employing a similar technique (personal communication). We are

very enthusiastic about this new approach and the expanding role that bioptics is taking on.

References:

1. Brick DC. Risk management lessons from a review of 168 cataract surgery claims.

Surv Ophthalmol 1999; 43:356-360.

2. Zaldivar R, Davidorf JM, Oscherow S, et al. Combined posterior chamber phakic

intraocular lens and laser in situ keratomileusis: bioptics for extreme myopia. J

Refract Surg 1999; 15:299-308.

3. Guell JL, Vazquez M, Gris O, et al. Combined surgery to correct high myopia:

iris claw phakic intraocular lens and laser in situ keratomileusis. J Refract Surg

1999; 15:529-537.

4. Pop M, Payette Y, Amyot M. Clear lens extraction with intraocular lens followed

by photorefractive keratectomy or laser in situ keratomileusis. Ophthalmology

2001; 108:104-111.