CORNEAL THICKNESS AND ENDOTHELIAL DAMAGE AFTER INTRAOCULAR LENS IMPLANTATION

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  • A C T A O P H T H A L M O L O G I C A V O L . 5 8 1980

    Department of Ophthalmology (Head: N . Ehlers), hhus Kommunehospital, University of Aarhus and

    Department of Ophthalmology (Head: E . Westerlund), Central Hospital, NykQbing Falster, Denmark

    CORNEAL THICKNESS AND ENDOTHELIAL DAMAGE AFTER INTRAOCULAR LENS IMPLANTATION

    THOMAS OLSEN and JENS SINDBERG ERIKSEN

    The corneal thickness and the specular appearance of the corneal endothelium are reported in 100 patients with unilateral intraocular lens implantation. Post-operative time ranged from one to 42 months. An average central endothelial cell loss of uncomplicated cases of 46%, range 1 to 83%, with no correlation with time after the operation was found. A significantly higher cell loss was found in cases with technical complications, shallow anterior chamber or increased intraocular pressure post-operatively. No correlation was found between the corneal thickness and the endothelial cell loss. In two patients, however, with a cell density below 500 cells/mm*, a slight increase in corneal thickness was noted. Thirty patients presented a guttate endothelium. Ir- respective of the occurrence of surgical complications the presence of a guttate endothelium was found to be a major determinant of the corneal thickness increase and could be ascribed as a cause of persistent corneal swelling in six of twelve patients with elevated corneal thickness. The progression of guttate changes occurred independently of the cell loss.

    Key words: cataract extraction - cell loss - corneal thickness - endothelium - lens implantation - specular microscopy.

    Cataract extraction combined with an intraocular lens implantation is now be- coming an increasingly employed surgical procedure. Along with the good refrac- tive correction it provides to the patient, this insertion of a foreign body into the eye has its costs, however. One of the feared complications is persistent corneal oedema, which seems to occur more frequently after lens implantation than after simple cataract extraction (Jardine & Sandford-Smith 1974; Pearce 1972, 1975; Duffner

    Received March 10, 1980.

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  • Thomm Olsen and Jens Sandberg Eriksen

    et al. 1976; Baggesen et al. 1978). The incidence of corneal oedema reported in these studies ranges from a few per cent to 13%. Other investigators have failed to demonstrate this higher incidence (Binkhorst & Leonard 1967).

    In recent years a number of specular microscopic studies have reported a greater endothelial cell loss associated with lens implantation than without lens implantation after cataract extraction (Bourne & Kaufman 1976; Forstot et al. 1977; Cheng et al. 1977; Sugar 1979; Abbott & Forster 1979; Galin et a]. 1979). Some authors have not found this higher cell loss (Hirst et al. 1977; Binkhorst et al. 1978). In these studies the cell loss after lens implantation ranges from 7 to 62%. The post- operative follow-up time, however, also varies considerably. Because a redistribu- tion of the cell population occurs during the first months after the operation (Rao et al. 1978; Sugar 1979; Galin et al. 1979) this makes a direct comparison of the studies difficult. The lowering of the cell population has been viewed with some concern because a low cell density presumably renders the cornea more susceptible to the development of corneal oedema (Irvine 1956; Capella 1971; Stocker 1971; Bourne & Kaufman 1976a; Kaufman 1979).

    The immediate post-operative increase in corneal thickness after lens implanta- tion seems to be higher than after simple cataract extraction (Cheng et al. 1977a; Praeger & Schneider 1977). Because of the quantitative association between cell loss and immediate corneal thickness increase after cataract extraction (Olsen 1980), this is to be expected. In the above mentioned studies, however, corneal thickness was found to return to normal levels some months after the operation. It is remarkable, that even in case of very high immediate increase in corneal thickness after surgery, and therefore presumably a high concomitant cell loss, the ultimate thickness has been reported to return to its pre-operative level (Giardini & Cambiaggi 1956). It therefore seems that the long-term effect of endothelial cell loss on the corneal thickness still remains to be shown.

    The present investigation was undertaken in order to elucidate the role of the endothelium for the ultimate hydration of the cornea after cataract extraction with lens implantation. By this study it was attempted to throw light upon the still unsettled question of the information yielded by the endothelial reflex and its significance for corneal hydration.

    Subjects and Methods At the Central Hospital in Nykebing Falster cataract extraction with lens implantation has been employed since 1976 in patients with senile cataract and more than 60 years of age. Indication for lens implantation has generally been found if the patient presented with no history of uveitis, no present eye inflammation, corneal oedema or marked endothelial dystrophy, glaucoma, retinal detachment, juvenile onset diabetes, myopia > 7 dioptres or a shallow anterior chamber.

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  • Intraocular Lens Implantation

    The surgical procedure was intracapsular cryoextraction with corneal incision. Pre-opera- ive treatment consisted in diamox 500 mg intravenously and eye ball massage. The lens used hroughout was a Federow iris clip lens (manufacturer: 3M). No special lens coating solution vas used to lubricate the lens prior to insertion. To obtain fixation of the lens dry pilocarpine vas applied to the wound edge. Normal saline was used as irrigating solution if necessary. Mound closure was done with 8-0 running Dexona or Vicryla absorbable suture. All but a ew operations were done by one surgeon (E.W.). Post-operatively, the patients were treated vith pilocarpine eye drops and prednisolone ointments for six and one months, respectively.

    For the present study only patients with an unoperated fellow eye without previous trauma ir disease other than cataract were included. In this way 140 patients with unilateral lens mplant were selected from the operated series. Eighteen patients had died since the )peration. Nine patients could not be traced or did not show up for the present follow-up nvestigation. Seven patients were omitted due to poor general condition. Four patients had he pseudophakos removed shortly after surgery due to dislocation of the lens and were .xcluded from the study.

    At the present follow-up examination corneal thickness measurements were deferred (and pecular microscopic examination not attempted) in two patients with clear corneas due to nability of the patients to fixate a target. One patient presented with an iridocyclitis on the )perated side. Because none of the other patients showed this complication this patient was kxcluded from the below grouped data (the corneal thickness was 0.550 and 0.5 10 mm of )perated and unoperated side, respectively, and the cell loss was 46% on the operated side).

    This leaves 99 patients, 39 men and 60 women, in the age range from 62 to 91 years, with a inilateral lens implant. Of these, two patients had previously undergone intracapsular .ataract extraction, whereas the rest of the patients had no previous history of disease or rauma in the now pseudophakic eye. The time period from the operation to the present 'xamination ranged from one to 42 months.

    Data concerning complications that occurred during or after the operation were obtained Ptrospectively from the case record.

    Central corneal thickness was measured with a modified Haag-Streit pachometer (Ehlers & iperling 1977). Each measurement was taken as the closest 5 pm reading on the scale reading )f the pachometer. Single determinations were used, the standard deviation of which has Ieen found to be 5-6 pm from a large number of readings on several individuals. Corneal hickness of non-operated eye was taken as control. In what follows residual corneal thickness ncrease refers to central corneal thickness of operated eye minus thickness of non-operated :ye.

    The corneal endothelium was photographed with a non-contact specular microscope Olsen 1979) in a central area of both sides, and 2-3 mm superiorly in the operated eye. If he specular photomicrographs from the central endothelium revealed one or more circular lefects in the endothelial reflex larger than two cells width, the endothelium was classified as 1 guttate endothelium. By using contralateral eye as control a cell loss was estimated as the 3ercentual decrease in cell count from unoperated eye.

    Resu I ts >orneal thickness

    rhirty patients showed a guttate endothelium with bilateral involvement in 28 of he cases. Irrespective of the occurrence of surgical complications the presence of a

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  • Thomas OLren and Jens Sindberg Eriksen

    guttate endothelium was found to be an important factor for the residual thickness. As shown in Table I the guttate changes were wOrse (more numerous and larger defects in the endothelial reflex) in the operated eye in about two-thirds of the cases which were largely responsible for the increased thickness in this group.

    In order to further analyse possible factors influencing the corneal hydration the patients were grouped as shown in Table 11. If per-operative complications such as excessive vitreous loss or difficulty in lens placement had occurred, or a dislocation of the lens had occurred post-operatively, the patients were classified as technical complications. The mean side difference in corneal thickness for this group was not different from the group of uncomplicated cases without guttate endothelium.

    Fourteen patients had a shallow anterior chamber post-o

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