Ординатура / Офтальмология / Английские материалы / The Art of Phacoemulsification_Mehta, Alpar_2001

322 THE ART OF PHACOEMULSIFICATION

Gowri J Murthy

KR Murthy

Cataract and glaucoma constitute two common causes of decreased vision. When they occur together, they present a unique problem in diagnosis and management.

Diagnosis of Glaucoma in the Presence of Cataracts

Diagnosis of glaucoma has traditionally rested on three criteria, namely the intraocular pressure (IOP), optic disc changes, and thirdly, visual field abnormalities. The presence of a cataract makes evaluation of the optic disc difficult, and poses certain problems in the interpretation of visual fields.

In the presence of cataract, one can try to visualize the optic by the noncontact high convex lenses, namely the 78D, 90D, 60D, etc, on slit-lamp examination. Having a well-dilated pupil facilitates visualization through a clear area in the lens. In very advanced lens opacities, one can also try to assess the disc by indirect ophthalmoscopy, but generally, if the disc is seen by indirect ophthalmoscope, it must also be amendable to evaluation by the noncontact slit-lamp methods. Considering the stereopsis, and the higher magnification provided by the slit lamp, this method, is by and large, the preferred method of evaluation of the optic disc, especially so in the presence of cataractous lenses. Evaluation of the disc in the other eye can also provide valuable information, particularly, if a mature cataract precludes visualization of the disc in the cataractous eye. Previous disc photographs, and ophthalmic records of the patient can also provide useful information.

MANAGEMENT OF GLAUCOMA IN CATARACT PATIENTS 323

Visual Fields in the Presence of Cataract

Problems in Performing the Test

Patients with cataracts should have the appropriate optical correction, while performing the fields. One should make a careful note of the location of the lens opacities, and try to correlate the field changes, in consideration of this. Pupillary diameter should be adequate, and any miotic used, should be withdrawn prior to the field test.

Interpretation

Generalized field depression can be a feature of cataracts. One should pay more attention to the pattern diviation, rather than the total deviation, as cataracts may cause the latter.

In visual field examination, decreased thresholds, flattening of the central field profile, exaggeration of pre-existing scotoma, and/or constriction of the visual field, may give an erroneous impression that the glaucomatous defects have progressed.1

When the lens opacities are so dense that meaningful interpretation of visual fields is impossible, one will have to rely on the fields of the other eye, or on previous records of the patient.

Gonioscopy can be misinterpreted in patients with cataract. Large or swollen lenses can alter the angle appearance, making it seem narrower than it actually is. The use of different diagnosis lenses—Zeiss, and the Goldmann lenses, in conjunction, may help in overcoming this problem. Comparing the angle of the other eye can also provide clues, as to the extent to which the lens has altered the angle appearance.2

Management of Cataract with Coexisting Glaucoma

Preoperative Considerations

One should meticulously work up the patient, and come to a conclusion as to the mechanism of the coexisting glaucoma, as mentioned in Figure 30.1. Management should be individualized depending on the mechanism of glaucoma.

The physician should determine the relative contribution of the two conditions, the lens opacity and the glaucomatous damage to the vision loss, and he/she should explain this clearly to the patient. This will result in realistic expectations about the postoperative vision by the patient. One can also employ laser interferometry, potential acuity meters, etc. to help in predicting the postoperative vision.2

Classification

•Based on the type of glaucoma

•Open-angle glaucoma (OAG) with cataract

•Narrow-angle glaucoma (NAG) with cataract

•Congenital galucoma with cataract

•Syndromes with coexistent cataract and glaucoma.

—Pseudoexfoliation

—Pigment dispersion

—Fuch’s heterochromic cyclitis

—Tumors

—?Steroid induced

Fig. 30.1: Patient with cataract with high IOP

The secondary glaucomas mentioned in Figure 30.1 should be managed appropriately, before undertaking cataract surgery. Certain situations deserve special mention.

•One should be especially careful in patients with pseudoexfoliation to look for associated zonular weakness. Pupillary dilatation may also be suboptimal.

•Presence of neovascularization due to proliferative diabetic retinopathy warrants panretinal laser photocoagulation, which might be done by indirect ophthalmoscopic delivery at the time of surgery, immediately after cataract extraction.

•Patients with fuch’s heterochromic cyclitis are especially prone to develop, postoperative hyphema, due to the fine neovascularization that is associated with this condition.

•Subluxated lenses have to be managed as the individual case dictates by either pars plana approach or limbal approach, and combined with an anterior vitrectomy in case of vitreous in the anterior chamber (AC).

•Patients, who have been on chronic miotic therapy for glaucoma, will present pupillary dilatation problems at the time of surgery. Pupillary stretch techniques may have to be used in such cases.

•There exists an increased possibility of occurrence of expulsive choroidal hemorrhage in patients whose IOPs have been on the higher side preoperatively, especially when there is sudden reduction of IOP at the time of entry into the eye.

MANAGEMENT OF GLAUCOMA IN CATARACT PATIENTS 325

•In patients with nanophthalmos, one will have to consider performing partial thickness scleral resection in four quadrants, (vortex vein decompression), in conjunction or before the other surgical procedures.3

Management of Cataract in Presence of Glaucoma

•Without prior glaucoma surgery

•In the presence of a filtering bleb

Options

•Only glaucoma surgery

•Only cataract surgery

•Combined surgery—glaucoma and cataract

1.Extracapsular cataract extraction (ECCE) + IOL + Trab

2.Phaco-trab

•Single site

•Two sites

How to Decide (Fig. 30.2)

Fig. 30.2: Algorithm for one approach to selecting a surgical procedure for patients with coexisting glaucoma, and cataract (from Shields MB: Ophthalmology 93: 366, 1986)

MANAGEMENT OF CATARACTS, AND GLAUCOMA (WITHOUT PRIOR FILTRATION PROCEDURE)

Filtration Surgery Alone, Followed by Possible Cataract Extraction Later

This two-stage approach can be considered in two situations.

326 THE ART OF PHACOEMULSIFICATION

In a Glaucoma Patient with Minimal Lens Opacities

This approach is justified only if the lens opacities are very minimal, and the patient has adequate vision for his/her needs. Though the newer microsurgical methods of glaucoma filtering surgeries have a reasonably high success rate— 8 to 90 percent, there have been reports of significantly higher incidence of development of lens opacities following glaucoma filtering surgeries. Another consideration is that over 50 percent of these filters will be lost when a subsequent cataract extraction is performed.1 But, with the advent of clear corneal phacoemulsification, this aspect should be reconsidered.

In patients with Uncontrolled Glaucoma

In the presence of uncontrolled glaucoma, despite maximal medical therapy, the urgency is to prevent further damage by IOP rise. The priority therefore is to reduce the IOP. It has been observed, that filtering surgery alone, followed by cataract extraction later, is associated with better long-term control of IOP compared to combined procedures at the same sitting. This is particularly so due to the availability of newer small incision cataract surgeries, which enable cataract extraction, with IOL implantation to be performed, at a site such that minimum manipulation or damage to the glaucoma filter occurs.5 However, with the advent of antimetabolite usage and other newer techniques of combined surgery, the observation noted above may no longer hold true. This has to be clarified by long-term studies.

Cataract Extraction Alone

As mentioned in Figure 30.2, this can be performed in patients with well-controlled glaucoma, on low-dose of medications, with mild to moderate glaucomatous field loss.

Small incision cataract surgery has an advantage of improved chances of successful filtering surgeries to be performed later, as an untouched quadrant of superior conjunctiva is preserved.6

Combined Cataract Extraction and Glaucoma Surgery

This approach can be considered in patients in whom cataract surgery is indicated, and have borderline IOP control, or patients who are not tolerating their antiglaucoma medications. Patients with well-controlled glaucoma, on medications with moderate to advanced field loss can also be considered for this combined approach.

The major advantage of combined procedures is in preventing the early postoperative pressure spikes, which can cause further field loss in a glaucomatous eye.6

Also, with the use of antimetabolities, and the newer small incision cataract surgeries combined with the glaucoma surgery, better success rates have been proposed in IOP control compared to earlier methods.

Generally the use of anterior chamber IOLs should be avoided in presence of glaucoma.

ECCE + IOL + Trabeculectomy

This is a well-known procedure in which the scleral (partial thickness) flap is performed, as usual, along with excision of the internal block, and performing the capsulotomy through this internal block/separate paracentesis. The wound is enlarged on either side of the scleral flap. The lens is expressed, cortical matter washed, and wound closed by continuous/interrupted sutures, after an iridectomy. Meticulous closure of the conjunctival flap is performed, which is usually fornix based in such cases.

PHACO-Trabeculectomy

Spaeth and Sivalingam, were the first to propose modification of the shelved posterior lip of a cataract incision to allow filtration, in 1976. With the advent of phacoemulsification, there has been resurgence of this concept.

The conjunctival flap can be either fornix/limbal based.

One can either make a standard trabeculectomy 5 mm partial thickness scleral flap first, and phacoemulsification, and IOL insertion is performed, in what will be the site of the sclerectomy. The sclerectomy can then be completed, and the wound closed as in any trabeculectomy, after a peripheral iridectomy.

Another approach is to perform a standard scleral tunnel phacoemulsification with IOL implantation, and, later modify the posterior lip of the wound, by excising a portion of this. This causes the wound to lose its self-sealing capability, and sutures may have to be used.7

Alternately, a two-site approach can also be used. Small incision cataract extraction with IOL implantation is performed by a 3 or 5 mm wound, which can be a scleral tunnel/clear corneal. At the same time, a separate trabeculectomy is performed at a different site superiorly.7

All the three approaches, have been claimed to produce better success rates, as compared to standard ECCE-Trabs, but long-term follow-up results are still awaited.

Antimetabolities can be used as adjuncts in these procedures. The guidelines for the use of these drugs, (5-FU, and Mitomycin-C) are as proposed by the Moorfields Eye Hospital/University of Florida (more flow) regimen.8

Management of Cataracts with a Pre-existing Glaucoma Filter

In the presence of a filtering bleb, while performing cataract extraction one has to avoid any damage to the bleb site. Small incision or clear corneal approaches are well suited in these circumstances.5

In all the surgical procedures mentioned above, postoperatively one should particularly look for and treat postoperative pressure spikes.

In the lens induced, phacolytic, and phacomorphic glaucomas, one can perform cataract extraction, by extracapsular methods, along with IOL implantation, after bringing down the pressure by medical means. Lens extraction alone, is sufficient to bring down the IOP in majority of the cases. However, in some cases, where the duration of the glaucoma has been long, one can consider combining the lens extraction, with a trabeculectomy.9

328 THE ART OF PHACOEMULSIFICATION

In conclusion, the management approach in a patient with both cataract, and glaucoma, has to be decided, after careful preoperative work-up, and has to be individualized to the particular patient.

R E F E R E N C E S

3. A. Neelakantan et al: Familial nanophthalmos—management and complication. Indian J Ophthalmol 42(3):139-43, 1994.

4. Laakainen L: Late results of surgery on eyes with primary glaucoma and cataract. Acta Ophthalmol 49: 281, 1971.

5. HJ Park, YH Kwon et al: Temporal corneal phacoemulsification in patients with filtered glaucoma.

Arch Ophthalmol 115:1375-80, 1997.

6. LF Cashwell, MB Shields: Surgical management of coexistent cataract and glaucoma. In Ritch R, Shields MB, Krupin T (Eds): The Glaucomas (2nd ed) CV Mosby: St Louis, 1745-61, 1996.

7. Allen D: Combined procedures. In Yanoff M, Duker J (Eds): Ophthalmology, CV Mosby: St. Louis, 4:27-32, 1999.

8. Peng T Khaw, Mark Wilkins: Antifibrotic agents in glaucoma surgery. In Yanoff M, Duker J (Eds) Ophthalmology CV Mosby: St. Louis, 3: 12-31, 1999.

9. Braganza A, Thomas R, George T et al: Management of phacolytic glaucoma—an experience of 135 cases. Indian J Ophthalmol 46:139-43, 1998.

Garry P Condon

Luis W Lu

I N T R O D U C T I O N

Advances in small incision clear corneal phacoemulsification and folding intraocular lens (IOL) technology have had no greater an impact in the management of cataract than in the glaucoma patient. Reduced incision size with a folding IOL improves the likelihood of continued bleb function in the filtered eye.1 A clear corneal incision that completely avoids conjunctival manipulation in the glaucomatous eye, allows infinite variability in the timing of a filtering procedure whenever surgical control of intraocular pressure (IOP) is necessary following cataract surgery (Fig. 31.1). In the previously filtered eye, the remaining available undisturbed conjunctiva greatly facilitates any repeat filtration procedure when needed (Fig. 31.2).

Phacoemulsification in the glaucomatous eye with a preexisting bleb, though generally safe, involves potential pitfalls not encountered in the otherwise normal eye.2 The most well recognized and concerning of these is the prospect of bleb failure requiring additional glaucoma surgery. A recent study suggested a bleb failure rate after phacoemulsification of approximately 5%, in patients with mean follow-up of 18 months.3 Additional studies have demonstrated fewer filtering bleb failures after uncomplicated phacoemulsification compared to extracapsular cataract extraction (ECCE).4,5 In the absence of complete bleb failure, an IOP rise of 3 to 6 mm Hg on average, has been reported, with no statistically significant difference attributable to antimetabolite use at the time of filtering surgery.6,7 Currently, there are no studies demonstrating increased bleb survival or IOP control associated with the use of 5-FU injections following cataract surgery in the presence of an established filtering bleb. Though not statistically significant, trabeculectomies originally performed with adjunctive mitomycin-c,

PHACOEMULSIFICATION IN THE PREVIOUSLY FILTERED EYE 331

once disturbed, and as a result, may enhance the likelihood of bleb fibrosis.14 The presence of viscoelastic material, lens particles, and liberated lens epithelial cells are variables that are not present in patients simply undergoing trabeculectomy alone and might possibly contribute to bleb failure in the previously filtered eye as well as a lower success rate in combined phacotrabeculectomy surgery.15-17

Surgica l Approaches

Essential to selecting an appropriate surgical approach is the complete evaluation of the patient’s optic nerve and visual field status, along with all information pertaining to the patient’s glaucoma medication history. A suggestion of progressive glaucomatous visual field progression would indicate some form of filtration augmentation be undertaken at the time of cataract surgery. A clear picture of

the patient’s medication tolerance, compliance, and response, is of utmost importance in anticipating the ability to control postoperative pressure elevation and thereby adjust the surgical approach accordingly. Although cataract surgery in the presence of a filtering bleb always creates a real possibility of bleb compromise, the option of combining simultaneous bleb revision affords an opportunity to enhance filtration and potentially long-term pressure control.

Previously filtered patients undergoing cataract surgery generally fall into one of three categories. First, there are the patients with apparently well functioning filtering blebs, in whom simple clear corneal small incision phacoemulsification is preferred along with the meticulous medical management of postoperative inflammation, and potential early IOP spikes. With this approach, care must be taken to avoid manipulating the conjunctiva and iris if at all possible.

A second category includes patients with marginal bleb function, or blebs that appear doomed to further compromise following phacoemulsification. In these patients, an internal bleb revision technique, utilizing a spatula directed through the internal sclerostomy via the corneal incision may improve filtration or provide some protection to the bleb. 18 Conversely or concurrently, minimal external dissection can be used to release fibrous adhesions allowing expansion of the bleb and enhanced outflow.19 Postoperative 5-FU injections or intraoperative mitomycin-C in the case of an external dissection may be considered.

The remaining patients are those in whom an obvious pattern of preexisting complete bleb failure requires combining cataract surgery with either complete revision of the original filtering bleb utilizing extensive conjunctival dissection, or the creation of an entirely new filtration site adjacent to the previous one. Combined phacoemulsification and trabeculectomy utilizing two separate sites has made this latter approach much more feasible where space constraints are not nearly the problem they were prior to small incision clear corneal phacoemulsification.20

The selection of a surgical approach is influenced ultimately by the desired target IOP for that individual patient, while considering available reserve options which might be required for postoperative pressure control. A 45-year-old patient with split fixation, a pressure of 15 mm Hg and poor medication compliance