Changes in the Corneal Endothelial Cell Density and Corneal Thickness Following Intraocular Lens Implantation

Changes in the Corneal Endothelial Cell Density and Corneal Thickness Following Intraocular Lens Implantation* K. PSI LAS, G. PETROUTSOS, D. PREVEZAS, CHR. KALOGEROPOULOS, M. ASPIOTIS and V. KATSOUGIANOPOULOS

University Eye Clinic of loannina, Medical School, Department of Ophthalmology, PO Box 1186, 451 10 loannina, Greece

The central corneal thickness and the central corneal endothelium of a consecutive group of 60 patients was measured before intracapsular (ICCE) and extracapsular (ECCE) surgery with implantation of an anterior (32 patients) or posterior (28 patients) chamber lens. The same measurements were made at 10 days and 1,3 and 6 months after surgery. The mean increase in corneal thickness after surgery was found to be 36.8 j.Lm at 10 days and 25.5 j.Lm at 6 months in the first group of patients. In the second group, 49.5 j.Lm and 29.0 j.Lm. The mean endothelial cell loss after surgery was 21.9% at 1 month and 26.6% at 6 months in the first group of patients and 19.6 and 23.8% in the second group. A significant correlation between increase in corneal thickness at 10 days and percentage of endothelial cell loss at 6 months was only found in the second group of patients (r = 0.52, P = 0.01). Keywords: Cataract surgery; Intraocular lens; Pachymetry; Endothelium

INTRODUCTION

It is well known that the corneal endothelium is essential for the long-term maintenance of corneal transparency. The human corneal endothelium has little capacity to regenerate once it is traumatized or damaged. When damaged human endothelial cells are replaced by enlarging neighbouring cells. This process may take several months after cataract surgery. Cellular losses can be estimated by observing changes in endothelial cell density [1] or by measuring the corneal thickness [2]. This study describes a prospecti ve series of 60 patients in whom pachymetry and endothelial microscopy were performed before and after cataract surgery. SUBJECTS AND METHODS

Sixty patients scheduled for cataract surgery from 15 August 1988 to 15 October 1988 in our Clinic were recruited in our study. Preoperatively, all patients * This paper was presented at the 7th Congress of European Intraocular Lens Implant Council, Zurich, Switzerland, 27-31 August, 1989. 0955-3681/91/010031 +04 $03.0010 © 1991 Bailliere Tindall

received a standard ophthalmological examination including, as far as possible, corrected visual acuity, applanation tonometry, and ophthalmoscopy. Patients with pathological systemic or ocular conditions were not entered into this study. Central corneal thickness was determined preoperatively and postoperatively at 10 days and 1, 3 and 6 months. Measurements were made using a Paxial Ultrasonic Pachymeter by a trained observer working for over 1 year. The pachymeter probe used has a frequency of 16 MHz and touched the eye in order to be perpendicular to the inner surface of the cornea (a sound beep informs the user that the probe is well positioned). The probe was applied to four points on four meridian lines (0°, 90°, 180° and 270°); there was a distance of about 3 mm (diameter ofthe central area measured) between each pair of opposite points. The lower value of each measured point was noted and the central corneal thickness was estimated by taking the average value of the measurements on four meridians. Increase in corneal thickness (.6CT) was taken to be the postoperative value, minus the preoperative value of the operated eye. Central endothelial cell densities were obtained by Eisner Contact Lens (Manufacturer: Haag-Streit A.G.) [3] preoperatively and postoperatively at 1, 3 Eur J Implant Ref Surg, Vol 3, March 1991

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and 6 months. The number of endothelial cells (observed in specular reflection) was estimated by means of a special eye piece with a comparison grid. A magnification of 55x was used for the estimation of the number of endothelium cells. This magnification was obtained by the combination ofthe 2.2 x magnification provided by the contact glass itself and the magnification of 25 x provided by the special eye piece (2.2 x 25 x = 55 x). Measlirements of endothelium cell density were made by three trained observers. The cell density in three areas of the central cornea was determined and the mean value of the two closest average measurements was taken into account. The significance of the association between 6 CT at 10 days and percentage of cell loss at 6 months was tested by the X2 test. The age of the 32 patients in the intracapsular cataract extraction group (lCCE; group A) with an anterior chamber lens (ACIOL) was 75.71 ± 8.80 (mean ± S.D.). The age of the 28 patients in the extracapsular cataract extraction group (ECCE; group B) with a posterior chamber lens (PCIOL) was 66.10 ± 9.64 (mean ± S.D.). The patients of each group were randomly selected. It is to be noted that an anterior chamber lens implantation was preferred in older patients and in those with iridodonesis (cases with operative complications were excluded from the study). Two basic types of cataract surgery were performed; intracapsular surgery with cryoextraction and extracapsular surgery with manual irrigationaspiration. An anterior chamber C-loop (SAC 3U or SAC 4U; CILCO) lens was implanted in the patients of group A after pupil constriction (Acetylcholine injected on to the iris) and the anterior chamber had been reformed using air (1% sodium hyaluronate (Healon) was infused to entrap the air and retain the chamber during the implant insertion, it was later aspirated). A posterior chamber lens was implanted (sulcus fixation) in the patients of group B. [Balanced Salt Solution (BSS) was used to irrigate the eye before lens implantation. After removal of lens material, air was used to reform the anterior chamber and was entrapped by Healon; this way the posterior chamber lens insertion was facilitated. After lens implantation Acetylcholine was injected on to the iris to constrict the pupil and Healon was aspirated from the anterior chamber.] Regarding models, we used the following posterior lenses: (a) With prolene haptics: Sinskey Modified J-loop (lOLAB)-Lester 045 (one closed-one open loop); Modified J-loop UV51; Modified C-loop UV52A (lNTERMEDICS); and Kratz-LS 5243UV (MEDICONZEPT); (b) One-piece: C-loop UI87 (lNTERMEDICS); and Kratz 9372UV (MEDICONZEPT). Postoperative medications, including topical anti-

K. Psilas et al.

biotics and topical corticosteroids, were given to all patients in the same fashion (for 2 months): 1) Tid for the first month; 2) Bid for the following 2 weeks; 3) Once every 24 h for the last 2 weeks. RESULTS

Preoperatively, there were no significant differences in central corneal thickness measurements (Table 1) Table 1 Central corneal thickness in ILm (Mean ± S.E.) Group A Group B (lCCE + ACIDL) (ECCE + PCIDL) Preoperatively 547.4 ± 5.2 548.1 ± 6.1 Postoperatively 585.9 ± 7.2 10 Days 598.6 ± 8.5 580.2 ± 5.4 1 Month 585.0 ± 7.3 3 Months 575.6 ± 5.9 578.0 ± 6.9 574.6 ± 6.1 6 Months 576.2 ± 6.4

and the number of central endothelial cells (Table 3) between the two groups of patients. The mean values, in micrometres, of the central corneal thickness measured preoperatively and postoperatively at 10 days and 1, 3 and 6 months are shown at Table 1. Table 2 Table 2 Increase in corneal thickness, ILm (Mean ± S.E.) Group A Group B (lCCE + ACIDL) (ECCE + PCIDL) Postoperatively 49.5 ± 5.9 36.8 ± 4.8 10 Days 1 Month 31.5 ± 3.7 36.9 ± 4.3 26.9 ± 3.2 29.9 ± 5.4 3 Months 6 Months 25.5 ± 3.4 29.0 ± 5.3

shows the increase in corneal thickness (6CT) in micrometres, after surgery, at 10 days and at 1, 3 and 6 months. Corneal thickness increases significantly (P < 0.001) at 10 days after surgery and decreases slowly, but remains increased (P < 0.001), by 6 months (Fig. 1). Preoperative and postoperative cell densities are shown in Table 3. Mean (percentage) cell losses for group A were 21.9% at 1 month, increasing to 26.6% at 6 months. For group B mean cell losses were 19.6% at 1 month, increasing to 23.8% at 6 months. The cell loss at 1 month was about 80% of the total loss at 6 months in both groups. The rate of cell loss decreased after the first month of surgery (Table 4, Fig. 2). No statistically significant difference was noted in endothelial cell loss and increase in corneal thickness up to 6 months between the patients with intracapsular cataract extraction and those undergoing an extracapsular procedure. The 6 CT at 10 days was plotted against the percentage of cell loss at 6 months after surgery for both groups of patients (Figs 3, 4). A significant correEur J Implant Ref Surg, Vol 3, March 1991

Corneal Endothelium and Thickness after IOL Implantation

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Fig.l Mean (± S.E.) values ofincrease in corneal thickness up to 6 months after operation

Table 3 Measurements of central endothelial cells mm -2 Group A Group B (ECCE + PCIOL) (lCCE + ACIOL) Preoperatively 1826 ± 58 1813 ± 74 Postoperatively 1458 ± 53 1 Month 1444 ± 65 3 Months 1376 ± 55 1374 ± 62 1370 ± 50 6 Months 1346 ± 63

Table 4 Percentage of endothelial cell loss (Mean ± S.E.) GroupB Group A (lCCE + ACIOL) (ECCE + PCIOL) Postoperatively 21.9 ± 1.4 19.6 ± 1.1 1 Month 22.9 ± 1.2 24.8 ± 1.4 3 Months 23.8 ± 1.2 6 Months 26.6 ± 1.4

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lation (r = 0.52, P = 0.01) between 6CT at 10 days and the percentage cell loss at 6 months was only found in the second group of patients. DISCUSSION

Our results suggest that the increase in central corneal thickness (6CT), in both groups of patients, increased 10 days after cataract surgery and decreased slowly up to 6 months. However, it remained thick compared to the preoperative values. Schultz et al. [4] reported that corneal thickness increased significantly in the central cornea at 1 week and returned to preoperative levels 1 month after surgery. The same results are reported by Cheng et al. [5]. We think that cell loss and increase of corneal thickness depend on method of cataract extraction, experience of the surgeon, implant type and difficulty of implantation. Our findings of endothelial cell loss after intracapsular or extracapsular cataract extraction are essen-

34

K. Psilas et al.

tially the same as those reported by other investi- thickness after the surgical trauma is not only due to gators. Kraff et al. [6] found that significant cell loss the number of remaining endothelial cells, but is also occurred with all surgical procedures, averaging be- an indication of their functional status which is tween 11.6% and 25.6%, depending on type of pro- related to the patient's age. This results in the cedure and implant used. In a recent study Matsuda absence of a significant linear correlation between et al. [7] reported that in 19 eyes receiving posterior ""CT at 10 days and percentage of cell loss at 6 chamber lens with intracapsular fixation, the mean months in the first group. A long-term study is taking place in our clinic in endothelial cell loss was 18.1%. In 18 eyes that received anterior chamber lens with posterior cap- order to evaluate the effect of intraocular lenses on sule remaining intact, the degree of cell loss was the corneal endothelium up to 5 years after surgery. 23.5%. We found that the mean endothelial cell losses were 26.6 and 23.8% 6 months after surgery in the REFERENCES first and second group of patients. These results are in keeping with the above studies or others [8, 9]. 1 G.O. Waring, W.M. Bourne, H.F. Edelhauser, etal. The corneal endothelium: Normal and pathologic structure and function. A significant correlation between ""CT at 10 days Ophthalmology, 89, 531-590 (1982). and percentage of cell loss at 6 months was found only 2 S. Mishima. Clinical investigations on the corneal endothein our second group of patients. In 1980 Kraff et al. [9] lium. Ophthalmology, 89, 525-530 (1982). reported that corneal thickness measurements did 3 G. Eisner, W. Lotmar and F. Papritz. A new contact glass for slit-lamp examination of the cornea, especially in specular not correlate with endothelial cell loss or trauma reflection. Ophthalmology, 92(S), 72-83 (1985). observed clinically at the time of surgery, and did not 4 RO. Schultz, D.B. Glasser, M. Matsuda, RW. Vee and H.F. seem helpful in the preoperative evaluation of catarEdelhauser. Response of the corneal endothelium to cataract surgery. Arch. Ophthalmol., 104, 1164-1169 (1986). act cases. In 1988 Cheng et al. [5] reported that a 5 H. Cheng, A.K. Bates, L. Wood and K. McPherson. Positive significant linear correlation was found between correlation of corneal thickness and endothelial cell loss. Serial measurements after cataract surgery. Arch. Ophthalmol., 106, "" CT in the immediate postoperative period and 920-922 (1988). percentage of cell loss at 1 and 6 months after catar6 M.C. KrafT, D.R Sanders and H.L. Lieberman. Monitoring for act surgery. The discrepancies in these reports may continuing endothelial cell loss with cataract extraction and intraocular lens implantation. Ophthalmology, 89, 30-34 be the result of differences in age of patients, method (1982). of cataract extraction and type of lens implant used. 7 M. Matsuda, K. Miyake and M. Inaba. Long-term corneal It is well known that injuries ofthe same intensity endothelial changes after intraocular lens implantation. Am. induce damage of the same number of endothelial J. Ophthalmol., 105, 248-252 (1988). cells. In our study the patients of the first group are 8 N.F. Martin, W.J. Stark and A.E. Maumenee. Continuing corneal endothelial loss in intracapsular surgery with and with10 years (difference of mean age) older than those of out Binkhorst four-loop lenses: A long-term specular microsthe second group. Thus in the first group there is also copy study. Ophthalmic Surg., 18(12),867-872 (1987). a further functional deterioration, induced by an 9 M.C. KrafT, D.R Sanders and H.L. Lieberman. Specular microscopy in cataract and intraocular lens patients. A report of injury less or more severe which results in an even 564 cases. Arch. Ophthalmol., 98, 1782-1784 (1980). more significant increase of corneal thickness 10 days after surgery. This happens because the corneal ReceiuedFebruary 1990

Eur J Implant Ref Surg, Vol 3, March 1991