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Mature Cataract

One of the biggest bugbears for a phaco surgeon is to perform a rhexis in a m a- ture cataract . Once one perform s rhexis in m ature and hyperm ature cataracts, then phaco can be done in these cases and a foldable intraocular lens can be im planted.

Presentation

Th e solu t ion to m at u re cat aract s is to h ave a dye th at st ain s th e an terior capsu le. Th is dye is t r ypan blu e (Fig. 7.4A,B). On e can also use in docyan in e green .

Differential Diagnosis

Ch eck for variou s causes of m at u re cataracts.

Management

Th e problem w h en on e operates a m at ure cataract is th e creat ion of th e rh exis, w h ich can be solved u sing a dye. Th e oth er problem is surge. On e sh ou ld un derstan d th e w orking of a ph aco m ach in e for un derstan ding surge. W h en an occlu ded fragm en t is h eld by h igh vacu um an d th en abruptly aspirated, fluid ru sh es in to th e

A

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ph aco t ip to equ ilibrate th e bu ilt-up vacu um in th e asp irat ion lin e, causing su rge. Th is leads to sh allow ing or collapse of th e an terior ch am ber. Differen t m ach in es em ploy a variet y of m eth ods to com bat surge. An oth er m eth od is th e air pu m p . An au tom ated air pu m p is used to pu sh air in to th e in fu sion bot tle, th us in creasing th e pressure w ith w h ich th e fluid flow s in to th e eye. Th is in creases th e steady-state pressure of th e eye, m aking th e an terior ch am ber deep an d w ell m ain tain ed during th e en t ire procedure. It m akes ph akon it an d ph acoem ulsificat ion a relat ively safe p rocedu re by reducing su rge even at h igh vacu um levels (Figs. 7.5, 7.6, 7.7, an d 7.8).

Fig . 7.5 The principles of how the phaco m achine works. This conceptual view shows the three main elements of m ost phaco systems. (1) The irrigation (red): Intraocular pressure is maintained and irrigation is provided by the bot tle of balanced salt solution

(B) connected via tubing to the phaco handpiece (F). It is controlled by the surgeon. Irrigation enters the eye via an infusion port (H) located on the outer sleeve of the bi-tube phaco probe. Height of the bot tle above the eye is used to control the inflow pressure.

(2) Aspiration (blue): (I) enters through the tip of the phaco probe, passes within the inner tube of the probe, travels through the aspiration tubing, and is controlled by the surgeon by way of a variable -speed pump (J). The peristaltic t ype pump is basically a motorized wheel exerting rotating external pressure on a portion of the flexible aspiration line, which physically forces fluid through the tubing. Varying the speed of the rotating pump controls the rate of aspiration. Aspirated fluid passes to a drain (l). (3) Ultrasonic energy (green) is provided to the probe tip via a connection (M) to the unit. All three of these m ain phaco functions are under control of the surgeon by way of a multicontrol

foot pedal (N). (Courtesy of Benjamin F. Boyd, MD, FACS, Editor-in-Chief, “The Art and the Science of Cataract Surgery.” Highlights of Ophthalmology, English Edition, 2001.)

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Fig . 7.6 Mechanism of the undesirable surge phenomenon. One problem area of the closed phaco system occurs during abrupt dislodging of an occluding piece of lens material so that it no longer occludes the aspiration port of the phaco tip. A sudden drop in intraocular pressure occurs as the fluid rate into the eye fails to imm ediately match the sudden fluid rate out of the eye. This is known as the surge phenomenon. (A) A piece of lens material occluding the aspiration port of the phaco tip is held in place by vacuum pressure created by the operating pump (D). (Note there is no drainage (E) from the blocked system .) Infusion from the irrigating bot tle (C) has ceased, but it is still providing controlled intraocular pressure due to its elevated position above the eye. With sufficient vacuum pressure from the pump and/or emulsification from the ultrasonic energy, the nuclear piece will abruptly enter the aspiration port and the fluid system will once again open (B). Because the plastic infusion/aspiration lines and the eye walls are flexible in absorbing the sudden inflow–outflow pressure differential, there occurs a moment when the infusion fluid (G, small arrow) does not effectively enter the eye fast enough to replace the fluid suddenly moving out of the unblocked system (F, large arrow). Outflow rate from the force of the pump is momentarily greater than the replacing infusion rate. This out-of-balance system (out of balance in not providing constant intraocular pressure) in which the eye m omentarily absorbs the inflow–outflow rate differential may traumatically collapse the eye for a short period. (Courtesy of Benjamin F. Boyd,

MD, FACS, Editor-in-Chief, “The Art and the Science of Cataract Surgery.” Highlights of Ophthalmology, English Edition, 2001.)

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Fig . 7.7 Technical solution to prevent the undesirable surge phenomenon. One technical solution for elim inating the surge phenomenon involves the use of a high-tech microprocessor. When a nuclear piece (F) occludes the aspiration port and then suddenly (B) is aspirated (F, arrow) by the vacuum pressure of the pump (P), a sensor (E) located on the aspiration line signals a microprocessor (G) in the unit that an abrupt surge in aspiration flow has begun to take place. Within milliseconds, the microprocessor directs the motor of the pump (P) to slow down. The reduction in aspiration rate resulting from the slowed pump occurs before the eye can collapse from any volum e differential encountered be - t ween sudden inflow and outflow rates. The potentially dangerous surge phenomenon is avoided. This elimination of the surge phenomenon allows the surgeon to safely use higher vacuum rates (necessary in some situations) with a reduction in the need to use potentially damaging high ultrasonic power set tings. Surgery becomes safer and faster.

(Courtesy of Benjamin F. Boyd, MD, FACS, Editor-in-Chief, “The Art and the Science of Cataract Surgery.” Highlights of Ophthalmology, English Edition, 2001.)

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Fig . 7.8 Diagrammatic representation of the connection of the air pump to the infusion bot tle.

Senile Cataract

On e sh ould perform cat aract su rger y w ell in sen ile cataracts (Fig. 7.9).

Presentation

Th e fu n dam en tal goal of Ph aco is to rem ove th e cat aract w ith m in im al dist urban ce to th e eye u sing th e least n um ber of su rgical m an ipulat ion s. Each m an euver sh ou ld be perform ed w ith m in im al force, an d m a xim al efficien cy sh ould be obtain ed .

Fig . 7.9 Rhexis being done in a case of senile cataract.

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Differential Diagnosis

Oth er system ic causes of cataract

Management

After viscoelast ic is injected in to th e eye th rough a 26-gauge n eedle, a globe stabilizat ion rod is in ser ted an d a clear corn eal in cision is m ade. On e can th en rem ove th e cataracts u sing th e divide an d con quer tech n iqu es. We prefer th e ch opping tech n ique (Figs. 7.10 an d 7.11). Th e Ph aco probe is in ser ted th rough th e in cision sligh tly sup erior to th e cen ter of th e n u cleu s, an d th e ph aco t ip is em bedded in th e n u cleu s w ith th e t ip directed obliqu ely dow nw ard tow ard th e vit reou s an d n ot h orizon t ally tow ard th e iris. On ce th e t ip is em bedded, w h ile in foot posit ion 2, th e n u cleus is ch opped w ith a st raigh t dow nw ard m ot ion at th e en d of w h ich th e ch op per m oves to th e left on reach ing th e cen ter of th e n ucleus (i.e., like a laterally reversed L) (Fig. 7.12). Th e n u cleu s is th en rot ated 180 degrees an d cracked again to get t w o h alves of th e n u cleu s. Th is is th en repeated to fu r th er ch op th e cataract in to sm aller pieces, w h ich are th en brough t in to th e an terior ch am ber on e by on e an d em ulsified . On ce th e n u cleus an d cor tex are rem oved th e foldable in t raocular len s is im plan ted (Fig. 7.13).

Fig . 7.10 A diam ond knife blade (D) enters the first incision (1), the second tunnel incision (2), and is then directed slightly oblique to the iris plane and advanced (arrow) into the anterior chamber. This forms the internal aspect of the incision into the cham ber

(A). This is the third step (3) in the three -step self-sealing incision. (Courtesy of Benjamin F.

Boyd, MD, FACS, Editor-in-Chief, “The Art and the Science of Cataract Surgery.” Highlights of Ophthalmology, English Edition, 2001.)

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Fig . 7.11 Emulsification of lens fragments: This surgeon’s view shows the manage - ment of the lens quadrants. The apex of each of the four loose quadrants is lifted with the second instrument (S), the ultrasound phaco tip (P) is em bedded into the posterior edge of each, and by m eans of aspiration the surgeon centralizes each quadrant for emulsification. U.S., ultrasound; Asp., aspiration flow rate; Vac., vacuum; C, capsule;

F, fragment. (Courtesy of Benjamin F. Boyd, MD, FACS, Editor-in-Chief, “The Art and the Science of Cataract Surgery.” Highlights of Ophthalmology, English Edition, 2001.)

Fig . 7.12 This cross-section view shows the phacoemulsification probe removing the nucleus frag - m ents within the capsular bag. Note the apex of one of the fragments created in the nucleus being lifted with the second instrument (arrow) and the ultrasound tip embedded into the posterior edge of each seg - m ent ready for emulsification. The epinucleus and cortex will then be removed during the phaco process. If we operate on a softer cataract, the freed fractured pieces are emulsified immediately. (Courtesy of Benja-

min F. Boyd, MD, FACS, Editor-in-Chief, “The Art and the Science of Cataract Surgery.” Highlights of Ophthalmology, English Edition, 2001.)

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Fig . 7.13 This cross-section view shows the movement of the foldable intraocular lens during insertion. Folding forceps removed for clarit y. (1) Folded lens outside the eye. (2) Folded lens passing through small incision. (3) Folded lens placed posteriorly into the capsular bag through anterior capsule opening and then rotated 90 degrees. (4) Lens slowly unfolded in the bag. (5) Final unfolded position of lens within the capsular

bag. (Courtesy of Benjamin F. Boyd, MD, FACS, Editor-in-Chief, “The Art and the Science of Cataract Surgery.” Highlights of Ophthalmology, English Edition, 2001.)

Glued Intraocular Lens

In t raocu lar len s (IOL) im plan t at ion in eyes th at lack posterior capsular su ppor t h as been accom plish ed in th e past by m ean s of an iris-fixated IOL, an terior ch am ber IOL, an d t ran sscleral IOL fixat ion th rough th e ciliar y su lcus or pars plan a. Su rgical exper t ise, prolonged su rgical t im e, su t u re-in du ced in flam m at ion , su t u re degrada- t ion , an d delayed IOL sublu xat ion or dislocat ion due to broken su t u re are som e of th e lim itat ion s in sut u red scleral fixated IOLs.

It is possible to p lace a posterior ch am ber IOL in eyes w ith a deficien t posterior capsule using a glu ed IOL tech n iqu e.

Technique

After clam ping th e su perior rect us, an in fu sion can n u la or an terior ch am ber m ain - tain er is in serted, preferably in th e in feron asal quadran t to preven t in terferen ce in creat ing th e scleral flap s, w h ich is th e n ext step in th e surger y. Tw o part ial-th ick- n ess×3lim.0mbalm-basedareth ensclereatedalflapsexactly~2.5 180 degrees

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A B

Fig . 7.14 (A) Scleral flaps (sf) of 2.5 x 3.0 mm made ~ 1.5 m m from the limbus. (B) Two flaps are made exactly 180 degrees diagonally apart.

diagon ally apar t (Fig. 7.14) up to th e lim bus. Th is is follow ed by vit rectom y via a pars plan a or an terior route to rem ove all vit reous t ract ion . Tw o st raigh t sclerotom ies w ith a 22-gauge n eedle are m ade ~1.5 m m from th e lim bu s un der th e exist ing scleral flaps. A corn eo-scleral or scleral t u n n el in cision is th en prepared for in t rodu cing th e IOL in secon dar y IOL im plan tat ion .

W h ile th e IOL is being in t rodu ced w ith on e h an d u sing a McPh erson forceps, an en d -gripping 23-gauge MST m icro rh exis forceps (MicroSurgical Tech n ology, Red - m on d, WA) is passed th rough th e in ferior sclerotom y w ith th e oth er h an d . Th e t ip of th e leading h apt ic is th en grasped w ith th e m icro rh exis forceps, pulled th rough th e in ferior sclerotom y follow ing th e cu r ve of th e h apt ic (Figs. 7.15 an d 7.16), an d extern alized un der th e in ferior scleral flap . Sim ilarly, th e t railing h apt ic is also extern alized th rough th e su perior sclerotom y u n der th e scleral flap . Scleral t u n n els are m ade w ith a 26-gauge n eedle at th e edge of th e scleral flap an d th e h apt ics are th en t u cked in to th ese scleral t u n n els for addit ion al stabilit y of th e IOL (Fig. 7.17). Recon st it u ted fibrin glu e is th en injected th rough th e can n ula of th e dou ble-sy- ringe deliver y system un der th e su perior (Fig. 7.18) an d in ferior scleral flap s. Local pressure is given over th e flap s for ~10 to 20 secon ds for th e form at ion of fibrin polypept ides. In pat ien t s w h o h ave a lu xated IOL, sim ilar lam ellar scleral flaps as

A B

Fig. 7.15 (A) The IOL is inserted with a McPherson forceps, and the leading haptic is grasped by an end-gripping 23-gauge micro rhexis forceps (f) passed through a scle - rotomy wound. The haptic is then externalised under the scleral flap (sf). (B) The trailing haptic is also externalized in a similar manner.