Documenta Ophthalmologica 81: 301-307, 1992. 9 1992 Kluwer Academic Publishers. Printed in the Netherlands.

Endothelial cell density and corneal pachometry after no-stitch, small-incision cataract surgery MICHAEL AMON, RUPERT PANOS PAPAPANOS

MENAPACE,

URSULA

RADAX

&

University Eye clinic, Vienna, Austria

Accepted 9 July 1992

Key words: Cataract surgery, corneal pachometry, endothelial cell density Abstract. In a prospective study we used the change of central and peripheral (12 o'clock-

position) corneal thickness (CT) after no-stitch small incision cataract surgery as a parameter of tissue traumatisation (33 eyes) and compared the values to a series of cases (32 eyes) with conventional 3.5 mm scleral step incision. In both groups the peripheral measurements showed a higher increase in corneal thickness than the central. After 1 month all eyes regained their central preoperative thickness. Increase in corneal thickness (ACTc, ACTp) after the different postoperative periods were correlated. The values of the central cornea showed no significant difference between the two groups. 1, 7 and 30 days after surgery the increase of peripheral CT was significantly higher in the no-stitch group. This fact was underlined by the clinical aspect at the slit lamp and is due to the anatomical and surgical characteristic of this procedure. One month postoperatively there was no increased endothelial cell loss in the no-stitch group (3%). No-stitch cataract surgery surgery provides a lot of intra- and postoperative advantages. The problem of increased swelling of the peripheral corneal entry seems to be a secondary one as corneal thickness decreases with time. Concerning the prospective endothelial cell loss it is mandatory to study the long term results. Introduction

N o - s t i t c h c a t a r a c t is a new, p r o m i s i n g surgical t e c h n i q u e [1, 2]. In this p r o c e d u r e a s c l e r a l - t u n n e l is p r e p a r e d a n d a c o r n e a l flap is c r e a t e d [1, 2]. T h i s t e c h n i q u e is r e p o r t e d n o t to h a v e a n y i n c r e a s e d r a t e o f p o s t o p e r a t i v e c o m p l i c a t i o n s [1, 2]. T h e p o s t o p e r a t i v e visual r e h a b i l i t a t i o n is a c c e l e r a t e d b e c a u s e o f t h e low p o s t o p e r a t i v e a s t i g m a t i s m d u e to s u t u r e l e s s w o u n d c l o s u r e [1, 2]. F o r p r e p a r a t i o n o f t h e t u n n e l incision with its i n n e r c o r n e a l flap a c e r t a i n a m o u n t o f m a n i p u l a t i o n is r e q u i r e d a n d all i n s t r u m e n t s h a v e to b e i n s e r t e d t h r o u g h c l e a r c o r n e a , b e h i n d the flap, into t h e eye. Surgically i n d u c e d t r a u m a t i s a t i o n o f scleral a n d c o r n e a l tissue including t h e e n d o t h e l i u m m a y l e a d to i n c r e a s e d c o r n e a l swelling a n d e n d o t h e l i a l cell loss [3, 4]. C o n c e r n i n g t h e p o s t o p e r a t i v e i n c r e a s e o f c o r n e a l t h i c k n e s s it was n o t p o s s i b l e to find a n y significant d i f f e r e n c e b e t w e e n a 7 m m - a n d a 3.5 m m scleral- s t e p incision in a p r i o r s t u d y [3]. In this s t u d y w e i n v e s t i g a t e d if t h e r e is a d i f f e r e n c e in i n c r e a s e o f c o r n e a l t h i c k n e s s b e t w e e n t h e no-stitch

302 technique and the 3.5mm scleral-step incision technique. In order to exclude an increased endothelial cell loss in the no-stitch group the central endothelial cell density was determined pre- and postoperatively. The endothelium maintains corneal transparency by its pump function, actively removing fluid from the stroma [5]. The efficiency of the pump depends on the number of working units and their functional state. Pump function may be impaired in a variety of ways [6], leading to swelling. This for example, happens in diseased states [7], if the cells are damaged [8], or if the physiologic milieu is altered [9]. While it is readily appreciated that the cornea swells when more fluid leaks into it than fluid is removed from it, it is not entirely clear how functional units are related to cell density, which is not significantly related to corneal thickness (CT) in normal eyes [10-12]. During surgery the cells and cell junctions may be damaged, resulting in increased ingress of fluid and reduced removal [13]. The increase and decrease in corneal thickness (ACT) may reflect the damage inflicted at surgery and the number of residual cells capable of dehydrating the stroma

[4]. Since it is postulated in literature that there is a correlation between the increase in CT in the immediate postoperative period and the percentage of endothelial cell loss 1 and 6 months after cataract surgery [4] this prospective study examines the changes in central (ACTc) and peripheral (2xCTp; 12 o'clock position) CT after no-stitch small incision cataract surgery as a parameter of tissue traumatisation with resulting endothelial cell loss. Presuming that this new surgical technique of scleral-tunnel preparation with lens-implantation affects values of CT and endothelial cell density, we investigated the changes of CT and endothelial cell density after no stitch small-incision cataract surgery and compared the results to a series of conventional 3.5 mm scleral-step incision cases.

Method

65 eyes were included in this study. 33 eyes were operated on with no-stitc~h small incision (3.5-4 mm scleral-tunnel preparation) cataract surgery and a folded Hydrogel-IOL was implanted in the bag (group N). 3 mm behind the limbus a scleral tunnel was prepared forward up to 1 mm into clear cornea. At the end of the tunnel the anterior chamber was opened and a 3.5 mm inner corneal flap was prepared in order to act as wound closure. After capsulorhexis all eyes were operated on by phakoemulsification. Only eyes with a central endothelial cell density exceeding 1500cells/ squaremeter were recruited for this study, eyes with cornea guttata or polymegatism were excluded. The exact surgical technique has been previously described in detail [1, 2, 14]. During all operations we used the same physiological solution for irrigation. The lens was inserted with a Faulkner folder through the 3.5ram

303 incision. All operations were done by the same surgeon, only eyes with uncomplicated senile cataract were accepted in this study. We randomized the nuclear density by clinical aspect at the slit lamp. The phaco time was comparable. Eyes with high intraoperative traumatisation resp. complications were excluded. Postoperative treatment consisted of 4 x Dexamethason drops and 4 x Indomethacin drops for 6 weeks. Eyes with postoperatively increased IOP were excluded. The mean age of the patients was 71.2 years (71.2 +-8.3; range 52-76a). There were 18 female and 15 male patients. Central endothelial cell counts were obtained using a contact specular microscope (Conan). Cell counts were performed preoperatively and 1 month after surgery. Corneal thickness (Ixm) was determined preoperatively and postoperatively after 1 day, 7 days and 30 days. Measurements were obtained using an ultra sound pachometer (Storz corneo-scan). All measurements were obtained by the same trained observer measuring CT for three times and taking the mean value. First central CT was determined, then peripheral CT was measured in 12 o'clock-position, i mm from the limbus. Increase in CT (ACT) was taken to be the postoperative value minus the preoperative value of the operated-on eye. Increase in CT after the different postoperative periods were compared to a series of 32 cases with conventional 3.5 mm small incision cataract surgery (group H). We have reported about this group previously [3]. This group consisted of 32 eyes. All patients were age, sex and refractive error matched. The technique of implantation and the type of IOL were the same in all cases. For statistical analysis the Wilcoxon test was used comparing ACT in the two different groups and the t test was used when comparing ACTc with ACTp in the same group, p < 0.05 was determined to be significant.

Results

There were 65 eyes included in this study. Mean preoperative results of CT are listed in Table 1. Central and peripheral thickness (CTc, CTp) showed no significant difference between group H and group N. Figure 1 shows the changes of CTc and CTp for both groups during the follow-up period. It can be seen in the graph that the fluctuation of CTc was almost the same and that CTp was different in the two groups. Mean values measured pre- and postoperativelY at 1 day, 7 days and 30 days and their increase in CT (ACT) are plotted in Table 1. One day after surgery increase in central and peripheral corneal thickness was higher in group N. The highest difference was 67 ~m for ACTp 1 day after operation (Table 1). As compared to group H this peripheral difference was significant in statistical analysis (p < 0.0025). Seven days after surgery ACTc was higher in group H. This was the

304 Table 1. Mean corneal thickness increase (ACT • SD) in groups H and N and difference in corneal thickness between the groups

Group pre (CT) (CT) 1 day post

c p c p c p c p

7 days post 30 days post

H ACT • SD

N ACT • SD

ACTN-ACTH

542 -+ 46 649 • 56 127 • 58 143 • 77 87 -+ 52 91 • 48 - 4 • 36 -16 • 45

540 -+ 40 670 -+ 50 150 -+ 100 210 • 110 50 • 40 120 • 110 1 • 30 60 -+ 70

23 67 -37 29 5 76

pre = preoperatively; post = postoperatively; c = central; thickness.

p = peripheral;

(CT) = corneal

o n l y o n e e x c e p t i o n w h e r e g r o u p H s h o w e d a h i g h e r i n c r e a s e . A C T p was h i g h e r in g r o u p N again. This d i f f e r e n c e was significant ( p < 0.0007). A f t e r 30 d a y s all e y e s a l m o s t r e g a i n e d t h e i r p r e o p e r a t i v e c e n t r a l c o r n e a l t h i c k n e s s . I n g r o u p N p e r i p h e r a l C T was h i g h e r significantly ( p < 0.0003). O n e a n d 7 d a y s a f t e r o p e r a t i o n C T p s h o w e d a h i g h e r A C T t h a n C T c ( T a b l e 2). A f t e r 1, 7 a n d 30 d a y s t h e d i f f e r e n c e was significantly h i g h e r in g r o u p N (1 d a y : p < 0.027; 7 d a y s : p < 0.0013; 30 days: p < 0.0002). W h e n i n v e s t i g a t i n g t h e c o r n e a s at t h e s l i t - l a m p an e v i d e n t d i f f e r e n c e in clinical a s p e c t was f o u n d in t h e p e r i p h e r a l p a r t o f t h e c o r n e a at t h e 12 o ' c l o c k p o s i t i o n . I n g r o u p N the c o r n e a s s h o w e d a r e m a r k a b l e e d e m a at t h a t a r e a a n d t h e e d g e o f t h e i n c i s i o n c r e a t i n g t h e c o r n e a l flap was visible in m o s t cases. I n statistical a n a l y s i s t h e c h a n g e s in c e n t r a l C T s h o w e d no significant d i f f e r e n c e b e t w e e n t h e t w o g r o u p s . A t all c o n t r o l s i n c r e a s e in p e r i p h e r a l C T was significantly h i g h e r in g r o u p N. In g r o u p N m e a n p r e o p e r a t i v e c e n t r a l e n d o t h e l i a l cell d e n s i t y was 1816-+ 383. A f t e r 1 m o n t h t h e c e n t r a l e n d o t h e l i a l cell d e n s i t y was 1762 -+ 375. M e a n e n d o t h e l i a l cell loss 1 m o n t h p o s t o p e r a t i v e l y was 3 % . 1100 i 1000

...

.q Boo;

700

T~

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.

.......................................

.

.

.~

~ " ~

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/

~= 500400, 300 o

1

7

Time After Operation (d) Fig. 1. Mean (-+SD) corneal thickness up to 30 days after operation. Group H: 9

central; O - - O peripheral; Group N: 9 - - 9 central; [] - 9- [] peripheral.

3'o

305 Table 2. Difference between CTp and CTc in each group (CTpcH, CTpcN) and difference in increase in CTp to CTc in each group (ACTpcH, ACTpcN)

Pre 1 day post 7 days post 30 days post

Diff. CTpcH (CTpH-CTcH)

Diff. CTpcN (CTpN-CTcN)

Diff. ACTpcH Diff. ACTpcN (ACTpH-ACTcH) (ACTpN-ACTcN)

107 123 111 95

130 190 200 189

16 4 - 12

60 70 59

pre = preoperatively; post = postoperatively.

Discussion

In a previous study we could show that changes in CT after cataract surgery are not primarily caused by the length of the incision [3]. In this study we investigated if the different technique of the no-stitch tunnel incision [1, 2] has an impact on postoperative corneal swelling and on the prospective endothelial cell loss. In literature there is not found any significant correlation between CT and endothelial cell count on 'unoperated-on' eyes [10, 12, 13]. Considering that changes in endothelial cell counts, which always happen after cataract surgery [15, 16], have an influence on corneal deturgescence and so on CT a connection of change in CT and endothelial cell loss seems reasonable [4]. As postulated in literature there is a correlation between increase in corneal thickness in the immediate postoperative period and percentage of endothelial cell loss 1 and 6 months after cataract surgery. So CT has b e c o m e an early prognostic parameter for the prospective endothelial cell loss. In our study we used the change of central and peripheral (12 o'clock-position) corneal thickness after two different techniques of cataract surgery as a parameter of tissue traumatisation with resulting endothelial cell loss. We investigated if in our findings there was a significant difference between corneal thickness in the two groups and thus in the prospective endothelial cell loss. Since Rao et al. reported a significant difference in ACT between 'polymegathous' and 'homomegathous' corneas [17] we only accepted 'homomegathous' corneas with at least 2000 cells/squaremeter for our study. For comparing the two groups a standardized technique of phacoemulsification was used [1, 2, 14] by the same surgeon, in order to get objective results, Irrigation during surgery was provided by the same solutions in both groups, so that differences of ACT caused by different intraocular milieus were avoided [9]. The length of the scleral-step incision was the same and only the anatomical location and the technique of the preparation of the tunnel were different in the two groups. F o r m e r studies showed that CT returns to almost normal values within the first 30 days [3,4, 18], so only measurements in the early postoperative

306 period are important and make early prognostic results possible. The early CT values reflect the short term changes caused by tissue-traumatisation after surgery [18]. The probability of high cell loss increases with CT [4]. Cheng et al. showed that a ACT of more than 75 txm 2 days and of 100 Ixm 5 days postoperatively provide useful clinical indicators for high cell loss. We have reported in literature about a difference between CTc and CTp respectively ACTc and ACTp after cataract-surgery [3]. Our hypothesis was, that the signs of tissue traumatisation should be higher at the peripheral (12 o'clock position) cornea, where all instruments are inserted and the limbal ciliary plexus is vulnerated. These considerations were the reason for obtaining measurements of the peripheral cornea. We thought that in the no-stitch group, having a corneal flap, the peripheral values are of more importance. In all measurements CTp was higher than CTc. This is a well known fact for 'unoperated-on' eyes since a long time [19]. We found a significant difference in the changes of CTp between the two groups. In both groups increase in CTp was higher than CTc. But 1, 7 and 30 days after operation group N showed significantly higher values of ACTp as compared to group H. During clinical observation at the slit lamp a remarkable difference of the peripheral cornea between the two groups was seen too. It seems to be obvious that this significant difference is caused by the anatomical and surgical characteristic of the no-stitch technique. In this technique preparation of the tunnel into clear cornea is necessary in order to create a corneal flap. All instruments are inserted through this part, at least 1 mm central from the limbus. Local edema and local endothelial cell loss seems unavoidable. If the findings of the peripheral corneal changes have an impact on the prospective endothelial cell loss has never been shown. The changes in central CT showed no significant difference between the two groups, a predictable fact. The fact that 7 days after surgery ACTc was much lower in group N remains inexplicable. From that point of view increased central endothelial cell loss should not take place. In our study we could not find any increased endothelial cell loss in the no-stitch group. Mean endothelial cell loss was very low. This fact seems to be due to the endocapsular, bimanuel phaco-technique. In order to preclude increased endothelial cell loss long term results are desirable.

Conclusion

No-stitch cataract surgery is a new surgical technique and provides a lot of intra- and post-operative advantages [1, 2]. Significantly increased corneal swelling of peripheral cornea during the first postoperative days is due to the anatomical and surgical characteristic of this procedure. The central cornea does not show any significant difference in increase in corneal thickness and in clinical aspect. One month postoperatively endothelial cell loss was 3% and thus comparable to other surgical techniques [20]. The problem with the

307

peripheral corneal edema is a temporary one as corneal thickness decreases with time. Long term results concerning changes in central endothelial cell density are desirable.

References 1. Menapace R, Radax U, Amon M, Papapanos P. No-stitch cataract surgery with flexible lenses: Evaluation of 100 consecutive cases. J Cat Refract Surg 2. Menapace R, Radax U, Amon M, Papapanos P. Kleinschnitt-Kataraktchirurgie ohne Naht: Bericht fiber 10 konsekutive Ffille. Spektrum der Augenheilkund 1991; 5(4): 135-140. 3. Amon M, Menapace R, Scheidel W. Results of corneal pachometry after small-incision hydrogel-lens-implantation and 7 mm scleral-step incision PMMA-lens-implantation following phacoemulsification. J Cataract Refrac Surgery 1991; 17: 466-470. 4. Cheng H, Bates AK, Wood L, McPherson K. Positive correlation of corneal thickness. Arch Ophthalmol 1988; 106: 920-922. 5. Maurice DM. The cornea and sclera, in Davson H, ed, The Eye. Orlando, Fla: Academic Press, 1984; vol 18: 75-89. 6. Waring GO, Bourne WM, Edelhauser HF et al. The corneal endothelium: Normal and pathologic structure and function. Ophthalmology 1982; 89: 531-590. 7. Olsen T. Transient changes in specular appearance of the corneal endothelium and in corneal thickness during anterior uveitis. Acta Ophthalmol 1981; 59: 100-109. 8. Green K, Livingston V, Bowman K et al. Chlorhexidine effects on corneal epithelium and endothelium. Arch Ophthalmol 1980; 98: 1273-1288. 9. Glasser DB, Matsuda M, Ellis JG et al. Effects of intraocular irrigation solutions on the corneal endothelium after in vivo anterior chamber irrigation. Am J Ophthalmol 1985; 99: 321-328. 10. Mishima S. Clinical investigations on the corneal endotbelium (38th Edward Jackson Memorial Lecture). Am J Ophthalmol 1982; 93: 1-29. 11. Kaufman HE, Capella JA, Robbins JE. The human corneal endothelium. Am J Ophthaltool 1966; 61: 835-841. 12. Amon M, Grasl M, Scheidel W et al. Bestimmung der pr/ioperativen zentralen Endothelzelldichte von Spenderhornh/iuten: Kritischer Vergleich zweier Methoden. Spektrum Augenheilkd 1988; 2(6): 245-248. 13. Khodadoust AA, Green K. Physiological function of regenerating endothelium. Invest Ophthalmol Vis Sci 1976; 15: 96-101. 14. Menapace R, Amon M, Radax U. Evaluation of 200 consecutive IOGEL 1103 bag-style lenses implanted through a small incision. J Cat Refract Surg (in press). 15. Oxford Cataract Treatment and Evaluation Team. Long-term corneal endothelial cell loss after cataract surgery. Arch Ophthalmol 1986; 104: 1170-1175. 16. Levy JH, Pisacano AM. Endothelial cell loss in four types of intraocular lens implant procedures. J Am Intraocul Implant Soc 1985; 11: 465-468. 17. Rao GN, Shaw EL, Arthur EJ et al. Endothelial cell morphology and corneal deturgescence. Ann Ophthalmol 1979; 11: 885-889. 18. Olsen T. Corneal thickness and endothelial damage after intracapsular cataract extraction. Acta Ophthalmol 1980; 58: 424-433. 19. Martola EA, Baum JL. Central and peripheral corneal thickness. Arch Ophthalmol 1968; 79: 28-30. 20. Sugar J, Mitchelson J, Kraft M. The effect of phacoemulsification on corneal endothelial cell density. Arch Ophthalmol 1978; 96: 446.

Address for correspondence: Michael Amon, MD, 1st University Eye Clinic, Spitalgasse 2, 1090 Vienna, Austria