Ординатура / Офтальмология / Учебные материалы / Color Atlas of Ophthalmology The Quick-Reference Manual for Diagnosis and Treatment
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502 Color Atlas of Ophthalm ology
Fig . 17.13 Iridectomy with argon laser—opening a narrow angle in chronic, narrow angle glaucoma. A laser iridectomy is the procedure of choice for narrow angle glaucoma except in cases such as (A) where the pe - ripheral iris lies too close to the cornea for treatment. Laser applications (D) are placed in the midstroma area of the iris to open the angle. These nonperforative laser applications cause heat, which in turn causes shrinkage of the iris collagen fibres in the direction of the arrow. The iris sphincter muscle (S) and the laser beam (L) are shown in (B), shrinkage from laser applications (D) has opened the angle to an acceptable position (C). A peripheral laser iridectomy is then executed. The normal iris location is shown on dot ted line (N). The angle is now sufficiently open for laser trabeculoplast y if indicated. Laser beam
(L) is shown producing burns (E) in the now visible trabeculum . (From
Boyd, BF, Lunt z, M. Acute and chronic angle closure. In: Innovations in the glaucomas. Highlights of Ophthalmology, 2002, 277. Courtesy Jaypee Highlights Medical Publishers Inc., Panama.)
It is an effective w ay of producing an open ing in th e iris but should n ot be used w hile the eye is congested or in flam ed . Clear m edia are essent ial. Th e eye is prepared w ith topical an esth esia. The surgeon sh ould have com fortable arm supports.
Th e Abrah am tech n ique is h igh ly u seful an d effect ive. Th ese bu rn s im m ediately cause iris con t ract ion an d put th e iris cr ypt on st retch . Oth er surgeon s fin d th at th e st retch burn is gen erally u n n ecessar y if th e Abrah am con tact len s is used .
In th e m ajorit y of cases, an iridectom y is ach ieved at th e first session . As p en - et rat ion of th e iris st rom a reach es th e pigm en ted epith elium of th e iris, bu rst s of p igm en t appear in th e an terior ch am ber (“sm oke sign als”). Pow er is th en reduced, an d fu r th er burn s are applied u n t il a m ush room clou d of aqueous an d pigm en t balloon s th rough th e iridectom y, in dicat ing pen et rat ion of th e iris.
Argon Laser Trabeculoplasty
Th e Glaucom a Laser Trial, a m ajor prospect ive, ran dom ized st udy, con cluded th at laser t rabeculoplast y as an in it ial t reat m en t for op en -angle glaucom a is as safe an d as effect ive as m edical t reat m en t . In som e cases, it m ay be m ore appropriate as in it ial th erapy. Th ese cases in clude (1) pat ien ts w h o can n ot or w ill n ot com p ly
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w ith prescribed m edical th erapy, (2) areas of th e w orld w h ere adequ ate m edical t reat m en t is un feasible because of povert y.
In all cases, to be su ccessful, th e angle does h ave to be open , th e m edia m u st be clear, an d on e m u st h ave access to th e t rabecular m esh w ork. Jam es B. Wise, M.D., w h o developed argon laser t rabecu loplast y (argon laser t rabecu loplast y), h as obser ved th at populat ion group s of ph akic pat ien ts do bet ter th an aph akic. It ap pears th at aph akia does in terfere w ith respon se to th e laser, probably by th e in fluen ce of vit reous in th e an terior ch am ber an d th e t rabecu lar m esh w ork. In terest ingly en ough , p seu doph akic pat ien t s resp on d to th e laser ver y sim ilarly th an ph akic pa- t ien t s. Th at is, th e presen ce of th e posterior ch am ber len s im plan t keeping th e vitreou s out of th e an terior ch am ber greatly im p roves th e respon se to th e laser. Eyes w ith an terior ch am ber len ses an d glaucom a u sually sh ow a p oor laser respon se du e to uveit is an d t rabecu lar dam age from th e len s (Fig. 17.14).
Fig. 17.14 Applying laser burns correctly in argon laser trabeculoplast y. Cross section to the left; cornea (E), Schlemm canal (C), scleral spur (S), Schwalbe line (G), anterior corneoscleral meshwork (A), pigmented band (P), and uveal meshwork (U). Proper placement of the 50 µm laser burn (L) is shown at the posterior margin of the pigmented band (P). To the right is a gonioscopic view with iris (I) below. Properly placed 50 µm laser burn at the posterior pigment band (P) shown at (1). Another burn is shown at (2) along the posterior margin of the pigment band (P). An oversized burn is shown at (3), spanning the entire pigment band. A slightly misplaced burn is shown at (4) in the middle of the pigment band. Aseriously misplaced burn into the uveal meshwork (5). (From Boyd, BF, Luntz, M. Argon
laser trabeculoplast y. In: Innovations in the glaucomas. Highlights of Ophthalmology, 2002, 149. Courtesy Jaypee Highlights Medical Publishers Inc., Panama.)
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Retinal Laser Photocoagulation
Many sign ifican t applicat ion s h ave been discovered for clin ical use of th e laser in oph th alm ology. Th e un ique feat u res of th e eye allow ing in t raocular t ran sm ission an d select ive absorpt ion of ligh t en ergy accoun t for a w ide range of laser t reat- m en ts.
Essen t ially, t reat m en t m ay be categorized in to five gen eral effect s: (1) in du ct ion of ch orioret in al bu rn s or ret in al scar th at lead to (possible ph arm acological) n eu - t ralizat ion of isch em ia-in duced ret in al n eovascu larizat ion ; (2) redu ct ion in ret in al vascu lar perm eabilit y via direct vascular closu re or un kn ow n m ech an ism s; (3) ablat ion of un desired t issue su ch as ch oroidal n eovascu larizat ion , t u m ors, abn orm al n at ive vessels, or aqu eou s-produ cing t issu e; (4) in du ct ion of a ch orioret in al scar th at m ay ser ve as a barrier to exten sion of subret in al fluid; an d (5) lysis of t rac- t ion -in ducing or m edia-opacifying t issu es (Fig. 17.15).
Th e tech n iques of laser ph otocoagu lat ion in clu de th e follow ing broad categories: scat ter t reat m en t , focal t reat m en t , ablat ive t reat m en t , dem arcat ing t reat- m en t , an d cut t ing t reat m en t .
Focal Macular Treatment
Macu lar edem a occurs from a variet y of disease m ech an ism s, bu t th e feat u re com - m on to each is in creased ret in al vascular perm eabilit y. Con t ribut ing factors in - clude ret in al isch em ia, in flam m at ion , an d t ract ion . Som e en t it ies in th e first of
Fig . 17.15 Argon laser treatm ent of a retinal tear (T). (From Cortez, R.
Managem ent of retinal detachment. In: Retinal and vitreoretinal surgery. Highlights of Ophthalmology, 2002, 402. Courtesy Jaypee Highlights Medical Publishers Inc., Panama.)
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Cryoprobes
Cr yoprobes are used for perip h eral ret in opexy in pat ien ts w ith periph erally located ret in al breaks an d tears, in th e t reat m en t of ret in al t u m ors an d ret in al vascular m alform at ion s. Th ey h ave also been u sed for perform ing cyclocr yoth erapy in en d -st age glaucom as.
Th e t ip of th e probe is placed over th e globe at th e edge of th e break w h ile visu - alizing w ith th e in direct oph th alm oscope. Th e freezing is th en applied un t il th ere is w h iten ing of th e ret in a (freezing of th e vit reous sh ou ld be avoided). On ce th e t ip h as th aw ed, it is rem oved an d th e n ext ap plicat ion is m ade (Fig. 17.17).
Fig . 17.17 Cryoprobe.
