in the absence of capsular support intraocular lens ( iol ) implantation behind the iris plane is still possible with various scleral fixation techniques [ 1 , 2 ] .
globe collapse , lens decentration , lens tilt , and sutures related complications are known encountered difficulties with sclera fixated iol ( sf - iol ) [ 35 ] .
although more points of fixation allow greater stability with less risk of decentration and tilt , there are greater risk of complications from multiple sutures passing through the sclera and the uvea .
stability of haptic fixation was questionable and required special lens designs , haptic modifications , or adopting a technique that avoids the use of sutures for haptic fixation [ 611 ] .
in this study , the widely available one - piece pmma lens was stabilized in the sulcus by two 10/0 polypropylene horizontal strings .
the efficacy of the two mechanically balanced strings in stabilizing an iol was experimented on a cardboard disc with two opposite peripheral holes mimicking the dialing holes of a pmma iol ( figure 1 ) .
a similar experiment was repeated in vitro with a pmma lens suspended by two mechanically balanced strings of a 10/0 polypropylene suture through its dialing holes .
temporal and nasal conjunctival periotomies are fashioned from 2 to 4 o'clock and from 10 to 8 o'clock .
two parallel 1/3 partial - thickness scleral grooves 5 - 6  mm long are made 2  mm from the limbus ( at 3 and 9 o'clock ) .
two rectangular scleral pockets are dissected from each scleral groove towards the cornea by a crescent knife till they reach the limbus at 3 and 9 o'clock .
a 7  mm superior corneal incision is fashioned and sutured to become water tight .
the straight needles of a double - armed 10 - 0 polypropylene suture ( alcon stj-6 ) are introduced into the eye by piercing the scleral bed at the upper and the lower extremities of the rectangular scleral pocket 2  mm from the limbus .
the needles are retrieved outside the globe from the corneal incision guided out by passing into the hollow tip of a 25-gauge needle inserted through the corneal incision .
the lower and the upper needles are retrieved to the left and the right of the corneal wound ( figure 2(a ) ) .
the lower end of the 10 - 0 polypropylene suture passes through the lower dialing hole of the one - piece pmma lens ( eyekon medical inc .
, usa ) from the front to the back surface of the lens and the upper needle passes through the upper dialing hole from the back to the front ( figure 2(b ) ) .
a 25-gauge needle is inserted under the lower extremity of the opposite ( exit site ) scleral pocket 2  mm from the limbus to emerge in the pupil for the retrieval of the lower polypropylene needle .
the latter is reintroduced into the eye from the corresponding side of the corneal incision and passes into the hollow tip of the preplaced 25-gauge needle .
the lower polypropylene needle is withdrawn out from the lower end of the opposite scleral pocket ( figure 2(c ) ) .
the corneal wound sutures are cut and the pmma posterior chamber iol is inserted through the main corneal incision into the sulcus ( figure 2(d ) ) .
the corneal wound is secured with three interrupted 10/0 silk sutures and the intraocular pressure is reformed .
the needle of the upper polypropylene string is withdrawn out from the upper extremity of the exit site scleral pocket by passing through the hollow of a preplaced 25-gauge needle .
the lower and upper 10/0 polypropylene strings are pulled tight from their exit site to bury the polypropylene loop at the entry site within the scleral pocket ( figure 2(e ) ) .
side to side lens centration is checked and readjusted along the two 10/0 polypropylene strings . 
 
the knot is secured to the scleral bed within the scleral pocket ( figure 2(f ) ) .
the viscoelastic is removed , and the conjunctival periotomies are sutured .  
 clinical experience .
six aphakic patients had sf - iol by the two - balanced - string technique through the dialing holes ( table 1 ) .
the research adhered to the tenets of the declaration of helsinki and was conducted after the approval of ethical review board ( erb ) of faculty of medicine , alexandria university .
preoperative evaluation included refraction , best spectacle corrected visual acuity ( bscva ) , intraocular pressure ( iop ) measurement , and fundus examination .
patients who had preoperative noncorrectable bscva , corneal opacity , or retinal problems were excluded from this work . lens tilt and decentration were assessed by visante anterior segment oct ( carl zeiss meditec , dublin , ca , usa ) .
a reference line was drawn between the scleral spur and/or the limbus on the opposite sides of the as - oct images .
( figure 3 ) the anterior and the posterior curvatures of the iol surface were determined . the lens periphery on as - oct
images was blotted geometrically by extending the iol curvatures until they meet at right and left angles .
a line was drawn between the lens curvature angles on both sides of the as - oct image to represent lens position .
a perpendicular line to the scleral spur or the limbus reference lines was drawn from their middle to bisect the iol curvature angles line ( ica - line ) .
the difference in length between the resulting right and left segments of the ica - line indicated the degree of lens decentration .
the angle subtended by the perpendicular line to the ica - line indicated the degree of iol tilt .
age ranged between 22  y and 73  y ( mean 51  y ) .
one patient had lens removal with a cutter and irrigation aspiration due to zonular dehiscence .
one patient had a sunset subluxated iol implanted in the bag due to zonular dehiscence .
preoperative bscva ranged between 20/80 and 6/60 mainly due to irregular astigmatism caused by sutures following the primary surgery or lens displacement .
postoperative bscva ranged between 20/20 and 20/80 measured at least four months following the removal of corneal sutures .
lens decentration ranged between 0.21  mm and 0.9  mm ( average 0.53  mm ) .
variable approaches for scleral fixation are described in literature with common documented difficulties : lens tilt , decentration , and sutures related complications [ 2 , 4 , 8 , 12 ] . in most scleral fixation techniques lens haptics are fitted directly to the sclera . that is why once the haptics are fixated , lens readjustment can be quite difficult . in this work ,
the iol is suspended in the ciliary sulcus through its optics by two horizontally placed strings passing through the lens dialing holes .
the two mechanically balanced strings prevent lens tilting as proved by the in vitro experiment .
vertical and horizontal centration of the iol is dependent in one plane on accurate symmetrical location of the suture entry sites , but it can be adjusted along the parallel sutures in the orthogonal plane , which is a potential advantage . the scleral entry and exit sites can be precisely determined because the direction of scleral penetration is always from the outside to the inside .
the two polypropylene strings are in fact a single loop and require only one knot that can be sutured and secured adequately enough to the bed of the scleral pocket under proper tension .
the polypropylene suture is placed isolated from the subconjunctival space within the scleral pocket to avoid producing a track for infection . in comparison to the standard use of scleral flaps for other sf - iol techniques ,
scleral collapse during iol suturing is managed by frequently reforming the intraocular pressure , which is helped by the temporary corneal stitches . using the commonly available one - piece pmma lens
there is also no need to keep special lens design in stock which can be difficult to keep in most ophthalmic theaters .
the main difficulties with this technique are that it requires an attentive skillful surgeon , who should pay utmost care for choosing the proper site and direction of needle insertion , guard against sutures entangling , and adjust string tension on a reformed globe .
too tight loop may lead to cheese wiring and too lax loop would cause lens sagging .
this technique also requires a 7  mm wound for pmma lens insertion and consequently wound sutures , which can induce astigmatism .
the degree of lens tilt and decentration were comparable to in - the - bag iol lens implantation .
the iol surface curvature angles were determined by geometrically blotting iol periphery along the well determined central iol surface curvatures .
the iol surface curvatures angles may not match precisely the actual lens edges but would have a symmetrical relation to them on both sides of the as - oct images .
deduction of the right and the left segments from each other would provide a precise measurement for iol decentration .
the ica - line was determined on the vertical and horizontal meridians and was correlated to a reference scleral spur line or limbus line .
this measurement technique provides precise iol plane - representing line suitable for different lens edge designs .
the use of a more durable suture material like polytetrafluroethylen ( gore - tex ) or a thicker ( 9 - 0 instead of 10 - 0 ) polypropylene suture material would be a safer option and was suggested by some authors [ 12 , 14 ] .
this work sheds light on an alternative technique to implant one - piece pmma iol in the absence of capsular support that may be of value in certain surgical circumstances .
 
 purpose . to describe and explore an alternative approach for sulcus intraocular lens ( iol ) implantation in the absence of capsular support 
 . methods . 
 the commonly available one - piece poly(methyl methacrylate ) ( pmma ) lens is stabilized in the sulcus by two intraocular horizontal strings of 10/0 polypropylene suture passed through the lens dialing holes in opposite directions to achieve a mechanical balance . 
 the horizontal strings of 10/0 polypropylene work as a rail track for the iol optics , allowing some side to side lens adjustment even following wound closure . the stability of the iol was tested in vitro . 
 six aphakic patients underwent in - sulcus iol secondary implantation using the balanced two - string technique . 
 patients were followed up for a minimum of six months . 
 best spectacle corrected vision was assessed . 
 lens centration and lens tilt were measured by anterior segment optical coherence tomography ( as - oct ) . 
 results . 
 all patients had successful lens insertion . 
 best spectacle corrected visual acuity ( bscva ) improved in all patients . 
 lens decentration ranged between 0.21  mm and 0.9  mm ( average 0.53  mm ) . 
 lens tilt ranged between 1.2 and 2.8 ( average 2.17 ) . 
 conclusion . 
 the mechanically balanced two - string technique is an alternative option for sulcus iol implantation in absence of capsular support , allowing lens centration adjustment with no additional risks . 
1. Introduction
2. Methods
3. Surgical Technique
4. Results (
5. Discussion