Ординатура / Офтальмология / Английские материалы / The Art and the Science of Cataract Surgery_Boyd, Barraquer_2000
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cataracts need to be removed so that treatment of the diabetic retinopathy can be performed. Occasionally, cataracts need to be removed when performing vitrectomy.
It is important that we consider various diabetic factors in planning cataract surgery because the retinopathy can influence the result. We may see increased bleeding and fibrin formation, especially in the younger patientswithactiveretinopathyandcompromised retinal perfusion.
Importance of Maintaining the
Integrity of the Lens Capsule
Cataract surgery may not only result in rapid progression of diabetic retinopathy, but it may also complicate its management and treatment. Rapid deterioration often occurs
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when the lens capsule and zonular integrity are sacrificed by the cataract surgery such as with rupture of the posterior capsule.
Retained lens material may produce increased inflammation, which may further accelerate this process. While it is important to maintain an intact posterior lens capsule, it is equally important tohave an easilydilatablepupil and a clear capsule to allow a good fundus view throughwhichlasertreatmentcanbeperformed.
Significant Increase in Complications
Following Cataract Surgery
The progression of retinopathy following cataract surgery may take several forms. We may see a patient with non-proliferative retinopathy rapidly develop macular edema (CSME) (Figs. 10, 11 and 13). Macular edema
Figure 12: Severe, Advanced Proliferative
Diabetic Retinopathy, Very High-Risk - A
Prolongued Vitreous Cavity Hemorrhage
May Result in Partial Opacification of Lens
Artistic rendition of severe, advanced, proliferative, very high risk diabetic retinopathy. (A) Shows a fundus view of a severe case of proliferative diabetic retinopathy. There are preretinal hemorrhages (H) in several locations. Note the extensive active fibrovascular proliferation causing a traction detachment (D) nasally due to traction from the fibrovascular tissue (A) on the retina. There is also active fibrovascular proliferation along the retinal vesselarcade(V)withdetachmentofthemacular area. Note the active fibrovascular stalk (S) which obscures the optic nerve. (B) Shows the sameeyewiththesurgeon'sviewasseenthrough thepupil,andaccompanyingcrosssectionview of the tissue pathology. Note hemorrhage (H), traction (arrows) of the posterior hyaloid (C), traction detachment of the retina (D), and active fibrovascular stalk (S) on the optic nerve.
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Figure 13: Diabetic Macular Edema
(A) Shows the fundus view of diabetic macular edema. Notice thickening of the macular area (F). From the oblique cross section (B), an area of the retina and choroid is magnified in
(C) to show its relationship to the clinical ophthalmoscopic fundus view above. In (C), there is pooling of fluid (D) within the inner layers of the retina. This fluid is trapped between the ganglion cell layer (G) and the outer plexiform layer
(P). Notice there is almost complete loss of the intermediary neurons (N) in this area.
may progress from being diffuse to being cystic. Rafael Cortez, M.D., has observed that diabetic patients with proliferative retinopathy (Fig. 12), or non-proliferative retinopathy (Fig. 13) or even without retinopathy, have a higher risk of developing a vitreous hemorrhage, rubeosis of the iris and neovascular glaucomapostoperatively. Thisriskisparticularly high in those patients with proliferative retinopathy (Fig. 12).
Appropriate Laser Treatment
Most diabetic retinopathy complications can be prevented by appropriate laser treatment before cataract surgery. Eyes with nonproliferative retinopathy that have clinically
significant macular edema (Figs. 13 and 14) should receive focal or grid laser treatment (Figs. 10, 11 and 14) to seal the leakage which is detectable through fluorescein angiography. Eyes with severe, non-proliferative (pre-pro- liferative) diabetic retinopathy (Fig. 15) and proliferative retinopathy (Fig. 16) should receive panretinal laser photocoagulation (Fig. 17) before cataract surgery. This treatment will reduce additional proliferation and deterioration.
Even with a cataract, laser treatment can usually be performed with good pupillary dilatation. Krypton red wavelengths are often successful in penetrating somewhat dense nuclear sclerotic lenses (Fig. 14). Retrobulbar anesthesia may be necessary.
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Figure 14 (above right): Prevention of Diabetic Retinopathy Complications by Laser Treatment before Cataract Surgery
Mostdiabeticretinopathycomplications can be prevented by appropriate laser treatment before cataract surgery. Eyes with non-prolif- erative retinopathy that have retinal thickening from edema near the macula should receive focal treatment of the macular aneurysms to erase fluorescein leakage. As shown in this figure, even with a cataract, krypton red wavelengthsareoftensuccessfulinpenetratingfairly dense nuclear sclerotic lenses. Laser treatment must be performed with good pupillary dilatation.
Figure 16 (below right): Proliferative Diabetic Retinopathy
This photo shows the next stage in severity of the disease. Please observe a large subretinal hemorrhage surrounding soft cotton exudates at the lower temporal arcade. There are also multiple intraretinal hemorrhages with neovascularization elsewhere (NVE), which is defined as a proliferative retinopathy anywhere in the retina which is greater than 1 disc diameter from the optic disc margin. The macula is not shown. (Photo courtesy of Samuel Boyd, M.D., Clinica Boyd, Panama).
Figure 15 (center): Severe Non-Proliferative Diabetic Retinopathy (Pre-Proliferative).
Thisphoto showsacharacteristicsevere,nonproliferative diabetic retinopathy, previously known as pre-proliferative. Please observe prominent soft exudates, dot blot hemorrhages, venous beading, and microaneurysms. (Photo courtesy of Lawrence A. Yannuzzi, M.D., selected from his extensive retinal images collection with the collaboration of Kong-
Chan Tang, M.D.)
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Figure 17 (above right): Panretinal Laser Photocoagulation Before Cataract Surgery
In treating diabetic retinopathy, panretinal photocoagulation covers all of the periphery and mid-periphery of the retina from the ora serrata to the vascular arcades, sparing only theposteriorpole. (PhotocourtesyofProf.RosarioBrancato, M.D., from Milan, Italy, reproduced from "Practical Guide to Laser Photocoagulation", Italian Edition by Brancato, Coscas and Lumbroso, published by SIFI.
Main Options in Management of
Co-existingDiabeticRetinopathy and
Cataract
The first and most successful is to defer the cataract surgery until laser treatment can be performed. If there is extensive vitreous hemorrhage or traction retinal detachment, you
Figure 18: Need to Combine Cataract Removal with Vitrectomy (Vitreous Hemorrhage and Traction Retinal Detachment)
The first indication for vitrectomy in the case of proliferative diabetic retinopathy is the presence of vitreous hemorrhage (H). This is conditional, however, depending on several factors such as status of retinopathy, visual loss, adequacy of previous photocoagulation, frequency of hemorrhage, vision in the fellow eye, advancing iris neovascularization, response to vitreous surgery in fellow eye, and systemic factors. In general, surgery for retinopathy is more likely to be indicated with hemorrhage in the presence of active fibrovascular proliferation or traction retinal detachment. This is the second indication for vitrectomy, namely a tractionretinaldetachment,butonlywhenthemacula
(M)isdetachedasshown. Notecontraction(arrows) ofposteriorhyaloid(P)causinganon-rhematogenous retinal detachment (D) due to traction from the fibrovascular tissue (A) on the retina.
may need to combine the cataract removal with a vitrectomy (Fig. 18).
Intraocular lenses do not present a problem when a patient is going to have a vitrectomy. The visual results of pseudophakic eyes with diabetic retinopathy complications that have vitrectomy surgery are essentially identical to those of phakic eyes.
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CATARACT SURGERY AND AGE-RELATED MACULAR DEGENERATION
Felix Sabates, M.D., has best outlined theprecautionswemusttakewhenconsidering extracapsular extraction or phacoemulsification in eyes with already present age-related macular degeneration already present. These principles are: 1) It is important to study the macular area in detail prior to cataract surgery to detect the presence of age-related macular degeneration. 2) If cataract surgery is performed in the presence of age-related macular degeneration, special care should be taken to reduce the possibility of inflammation even if it would require immediate use of antiinflammatory drugs. 3)Cystoidmacularedema should be aggressively treated, with careful follow-up emphasized. 4) Cataract surgery should not be performed on the patient with active "wet" macular degeneration (Fig. 19) untilithasbeenbrought toadrystage(Fig.20). If there is bleeding from a neovascular membrane, cataract surgery should be postponed until at least six (6) months after the blood has completely reabsorbed and there has been no recurrence ofthebleedinghasbeenpresent. 5) In patients with macular scars (Fig. 20) and opaquecataracts,surgicalremovaloftheopacified lens with intraocular lens implantation may be of benefit in recovering some degree of pericentral or peripheral vision. The smaller the macular scar, the better the prognosis. No cataract surgery should be performed unless the cataract is opaque enough so that when it is removed, the patient will probably perceive the benefit of the operation.
RETINAL BREAKS AND RETINAL DEGENERATIONS PRIOR TO CATARACT SURGERY
The preoperative treatment of these retinal lesions has traditionally come into consideration as a possible means of preventing retinal detachments after cataract extraction, especially in myopes. I refer only to those peripheral retinal degenerations which can be clinically defined and identified, and which have statistically been linked with retinal detachmentfollowingposteriorvitreousdetachments. This, therefore, excludes senile retinoschisis, which has a higher prevalence in the general population than among patients with a retinal detachment. What needs to be clarified is the effect of cataract surgery on the risk retinal breaks and degenerations present and what recommendations should be given in regard to their management prior to cataract surgery. This requires therapeutic proof that prophylactic treatment significantly lowers this risk below that which the natural course of untreated lesions would present. There is an increasing tendency to support the concept that retinal detachments generally are associated with recent, not old, retinal breaks. At the present time the picture is not clear. We lack solid reports supporting the prophylactic treatment of preexisting retinal breaks prior to cataract surgery.
What happens to an eye with lattice degeneration when cataract extraction is performed? Again, we face a lack of valid reports in the literature to support preventive treatment prior to cataract surgery. About 90% of eyes with lattice degeneration do not detach after small incision cataract extraction even when
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Figure 19 (above right): Anatomy and Pathology of
Exudative, ("Wet") Macular Degeneration with
Extrafoveal Neovascularization
Cataract surgery should not be performed in these cases. Wait until it has been brought to dry stage as shown in Fig. 20. Fundus view (A) shows an example of exudative"wet"maculardegenerationwithanextrafoveal neovascular membrane (N) and limited subretinal hemorrhage (H) just at the margin of the paramacular retinal vessels surrounding the fovea (F). From the oblique cross section (B), an area is magnified in (C) to show the direct relationship between clinical ophthalmoscopicfundusviewaboveanditscorresponding cellular pathology. Pathology reveals that the retina is slightly elevated over a neovascular membrane (N). Note vessels emanating from the choriocapillaris (J), into the neovascular membrane (N) and into the sub-RPE and subretinal spaces, passing through small breaks (T) in the retinal pigment epithelial cell layer (E). There is some atrophy of photoreceptors in this area (P). Subretinal blood (H) is seen to either side of the neovascular membrane. Large choroidal vessels (K).
Figure 20 (below left)): Anatomy and Pathology of Non-Exudative, Geographic ("Dry") Macular Degeneration
Inthesepatients,surgicalremovaloftheopacified lenswithIOLimplantationmaybeofbenefitinrecovering some degree of peripheral vision. Fundus view (A) shows an example of non-exudative, geographic atrophic "dry" maculardegenerationwhereatrophyoftheretinalpigment epithelium predominates. The smaller the macular scar, the better the prognosis for cataract surgery. Notice the clinical signs of drusen (D) which can appear as discrete subretinalbodies,confluentmassesorhardglintinglesions, usually yellowishincolor. Darkerintraretinal pigment (I) may or may not be present. Retinal pigment epithelium atrophy (E) is identified by prominence of the underlying choroidal vessels. From the oblique cross section (B), an area is magnified in (C) to show the direct relationship between the clinical ophthalmoscopic fundus view above and its corresponding cellular pathology. Pathology includessubretinaldrusen(D)andatrophyoftheRPE(E). Compare the disorganized RPE cell layer at (E) on the right to the more normal configuration at (N) on the left. Most importantly, though not clinically visible, there is definite loss of photoreceptors (P) in the area of degeneration (compare with normal photoreceptor layer on the left). Other anatomy: inner limiting membrane (L), choriocapillaris (J) and large choroidal vessels (K).
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YAG laser capsulotomy is later performed. Those that do develop a retinal detachment frequently do not detach from retinal breaks adjacent to or within the lattice lesions, but from unrelated areas which previously looked clinically normal. This has now been observed by numerous investigators.
Sabates thinks that each case must be individualized. If a patient has a history of retinal detachment in one eye and lattice degenerationwithretinalholesintheothereye, he performs cryosurgery or laser surgery and closes those holes in the second eye. Usually cryosurgery is required because the cataract
may preclude the use of laser. The type of tear present and other factors including the location of the tear and the existence of high myopia would influence the ophthalmologist's judgment in deciding when to treat. Fig. 21 shows the typical retinal tear that he treats, sealed with cryotherapy.
Since seven to eight percent of the populationhaslatticedegeneration,itisobviousthat notallpatientswithlatticedegenerationshould be treated. Regardless of whether the patient is treated prior to cataract surgery, those patients should be followed closely with careful examination of the peripheral retina postoperatively following cataract removal.
Figure 21: Creating the Chorioretinal Adhesion of Retinal Tear with Cryotherapy Before Performing Cataract Surgery
Thisfigurepresentsthetreatmentwith cryotherapy of a retinal tear that needs to be sealed prior to cataract surgery. The freezing and defrosting is observed with the indirect ophthalmoscope. (A conceptual slit beam has been added to this illustration to enhance the 3-dimensional nature of the view).
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CATARACT SURGERY IN PATIENTS WITH UVEITIS
Rubens Belfort Jr.,M.D., in Sao Paulo, Brazil and Martinez Castro in Mexico have conductedextensiveresearchonthesepatients. Cataracts develop frequently in patients with uveitis, either as a result of inflammation, the treatment of inflammation or both. There has been much controversy as to what to do, how to do it and when to operate in patients with cataract and uveitis, and whether intraocular lenses should be implanted in these patients.
Professor Rubens Belfort Jr. considers that uveitis is one of the last categories for which surgeons have advised «don’t do it» when cataract surgery is considered. Cataract surgery has been regarded as contraindicated because of the initial bad results with intraocular lenses (IOLs) in patients with uveitis. Until about 10 years ago, most surgeons avoided cataract surgery with or without IOL implantation in these patients.
There was concern about superimposing IOL implantation, with the inflammation which used to accompany it in many cases, on a seriously compromised and already inflamed eye. This concept has now changed. The development of current techniques for small incision cataract surgery, new types of IOLs, and advances in the management of patients with uveitis have changed the prognosis. The change is fortunate because cataracts are the major cause of loss of vision in patients with chronic uveitis (Fig. 22). Moreover, cataracts are potentially dangerous for patients with uveitis because they interfere with visualization of the fundus, denying the ophthalmologist the opportunity to identify macular lesions and to treat them adequately. When these pa-
Figure 22: Uveitic Cataract
Cataracts caused by an inflammatory uveitic process generally occur with pigment deposits (P) on the anterior capsule of the lens (C) related to anterior synechiae that can immobilize the pupillary sphincter. The intensive use of topical steroids for the management of the uveitis can hasten the formation of such cataracts. Cataracts are the major cause of loss of vision in patients with chronic uveitis. Current techniques for small incision surgery, new types of IOL's and advances in management of uveitis enable their removal where previously this was contraindicated.
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tients finally undergo long-postponed surgery, usually with good anatomic success, central vision may not be recovered because of irreversible macular damage that had developed from chronic cystoid macular edema. Therefore it is critical for both the surgeon and the patient with uveitis to realize there is another reason for cataract surgery in addition to improving vision as much as possible. Removal of the cataract enables the the ophthalmologist to examine and treat the macula in order to forestall damage.
Method of Choice
In theory, removal of the lens as a whole (intracapsular) could lead to less inflammation. In fact, careful extracapsular surgery with adequate cleaning of the lens material during surgery usually provides a better outcome. Most surgeons now prefer phacoemulsification to a classic extracapsular extraction of the cataract even in patients with uveitis. Belfort believes phacoemulsification leads to faster results and less inflammation, and he advocates phacoemulsification with or without an IOL.
Intracapsular technique is no longer used except in some rare cases of lens-induced uveitis, in which inflammation is caused by the leakage of protein material from the lens.
Diagnosing the Type of Uveitis in the
Pre-Operative Phase
Belfort emphasizes that in the preoperative phase, it is very important for the surgeon to determine the exact type of uveitis the patient has in order to better predict the surgical outcome and minimize reaction. For
instance, patients with ocular sarcoid have a much worse postoperative course than other patients. Therefore, a patient with sarcoidosis and uveitis, even in the absence of important uveitis, must be approached more carefully than patients with other types of uveitis. Other types of uveitis that can be effectively managed are Fuchs’ heterochromic cyclitis, intermediate uveitis, and posterior uveitis as well as most of the anterior essential uveities. Behcet’s disease and other vascular inflammations, which in the past were considered to have a bad prognosis, have shown much better results with current techniques.
Preoperative Management
In general, the less inflamed the eye at the time of surgery, the better the prognosis. Ideally, every patient should be operated only after being inflammation-free for at least 3 months, although this is not possible in many cases. Uveitis is chronic, no matter what dose of steroids is used, and many patients must be operated even in the presence of some active uveitis. The goal is to have the eye as little inflamed as possible. Preoperative steroids, as eyedrops or even systemically, as well as immunosuppressive drugs have to be used in more severe cases. In patients who do not respond to steroids alone, Belfort uses systemic oral cyclosporin and oral prednisone therapy. In 20% of patients the use of an IOL is not advisable. This includes patients with granulomatous uveitis such as sarcoid, Vogt-Koyanagi-Harada syndrome, and sympathetic ophthalmia. Belfort also advises against using IOLs in patients with juvenile rheumatoid arthritis, who tend to have a chronic disease and may develop long-term complications.
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The Intraocular Lens
Currently, IOLs can be used in at least 80% of patients with both uveitis and cataract. Selecting the right type of IOL is very important. Although PMMA lenses are well tolerated by the eye with uveitis, they may lead to more posterior capsule opacification than other lenses. Belfort recommends not using silicone in cases of uveitis because silicone lenses by themselves can cause uveitis and may aggravate previous intraocular inflammation, especially in heavily pigmented people. Belfort therefore prefers to use acrylic lenses in these patients. We do not yet have clinical trials or studies that establish conclusively the superiority of one lens material over another. Results appear not to be better with heparin-coated IOLs than with PMMA lenses in patients with uveitis. Considering that heparin-coated lenses are also more expensive, Belfort does not advocate using them in uveitis.
CATARACT SURGERY IN ADULT STRABISMUS PATIENTS
Preoperative Judgment
The treatment of co-existing cataract and strabismustraditionallyhasbeenmanagedwith separate operations. Usually the cataract ex-
traction has been done first, followed later by a surgical correction of strabismus. As a matter of fact, we may even hesitate to remove a cataract in a patient who has had a deviated eye foralongperiodfortworeasons: First,cataract removal may result in postoperative diplopia, and second, it is difficult to predict whether amblyopia may be present in the deviated eye, leaving us with a questionable prognosis.
Successful combined cataract and strabismus surgery is highly feasible. The ideal patient for a combined approach must fill certain prerequisites: one, he or she must have a congenital strabismus rectifiable by surgery on asinglemuscleineacheye. Second,thepatient must have an alternating deviation and equal fusion potential in each eye, determined either byknowingthepatient'svisionbeforetheonset of the cataracts or by the results of the potential acuity meter (PAM) that should be about equal in both eyes (see figures 3 through 7). An equal potential acuity meter measurement in both eyeswouldseemtoexcludeamblyopia,thereby improving the chances for an optimal visual outcome.
During combined cataract and strabismus surgery, if the patient continues to blink or squeeze the eyelids following the combined topical and intracameral anesthesia, you can obtain anesthetic control this a sub-Tenon's injection of lidocaine as illustrated in Figs. 33 and 34. The effect is almost instantaneous, and surgery can continue without delay.
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