A C T A O P H T H A L M O L O G I C A V O L . 5 9 1 9 8 1

Department of Ophthalmology (Head: Salme Vannm), University of Helsinki, Helsinki, Finland

CONTACT LENS INDUCED TRANSIENT CHANGES IN CORNEAL ENDOTHELIUM

BY

VANNAS ANTTI, MAKlTlE JUKKA, SULONEN JUKKA

AHONEN RElJO and JARVINEN ESKO

The effect of soft contact lens (SCL) wear on corneal endothelium was studied with a noncontact specular microscope in 2 1 unadapted young volunteers. In 4 cases the specular reflection remained intact. In 6 cases the specular reflection was abnormally pronounced in the cell periphery and less pronounced in the central cell area. Nine of 21 eyes presented also nonreflecting areas or blebs. In 2 individuals these changes were extensive. The changes appeared 4 to 10 min after the contact lens (CL) insertion and reached a maximum after 15 to 40 min. The endothelial mosaic returned to normal about 30 min after removal of the CL. The endothelial bleb reaction and the role of atmospheric oxygen flux to the endothelium is discussed.

Kpy words: soft contact lenses - corneal endothelium - specular microscopy - blebs.

There has been a general consensus that the corneal endothelium is not greatly affected by CL wear. However in recent studies transient endothelial changes or blebs have been reported in the endothelial mosaic soon after CL insertion (Zantos & Holden 1977, 1978; Holden & Zantos 1979; Vannas et al. 1979).

Some corneal thickness increase accompanies CL wear (Mandell et al. 1970; Holden 8c Zantos 1979). Corneal hypoxia may cause such edema (Hill 8c Cuklanz 1967; Mandell et al. 1970; Poke & Mandell 1970), though other factors may also be involved (Kempster & Larke 1978). Symptoms of corneal distress, discomfort and blurring of vision with SCL wear has also been reported if a succesful SCL wearer is subjected to high altitudes with diminished oxygen tension (Clarke 1976; Hapnes 1980).

Received on February 23rd, 1981.

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A perfectly clear cornea requires undisturbed function of the endothelial cells. Contact lenses are generally used in ophthalmologic practice and the aim of the present study was to achieve clinically valuable information on the rapidity of onset and recovery of the SCL induced endothelial reaction.

Series and methods

The subjects were 21 healthy volunteers, 8 women and 13 men, who were unadapted to SCL wear. The age distribution ranged from 22 to 35 years (mean 26.0). A careful eye examination was performed on all the volunteers. None

Fig. 1. Composite specular photograph of normal looking corneal endothelium before, during and after SCL wear. Picture C is taken before SCL insertion. Pictures before the vertical bar are photographed through the SCL. The numbers before the vertical bar indicate the minutes of SCL wear. The vertical bar marks the time of SCL removal and subsequent numbers with

minus bar the minutes after SCL removal. X 160.

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Fig. 2. Specular photograph demonstrating slight endothelial reaction. Mottled reflection and blurred boundaries of endothelial cells are seen. The arrow indicates the same cells in the

central endothelial mosaic. X 160.

presented a previous history of eye diseases and all were unadapted to SCL wear. The corneal endothelium was photographed before the eyes were fitted with a

thick tight fitting SCL (plano lens, average thickness 0.3 mm, 30% water content) with limited oxygen transmission. The base curve of our experimental lens was 8.0 mm in all cases. The same endothelial area was repeatedly observed and photo- graphed directly through the SCL after lens insertion. The duration of SCL wear ranged from 15 to 40 min (mean 28 min). The endothelium was observed for 40 min after lens removal to document the recovery of blebs. A noncontact specular microscope was used for the photography. A powerful flash (600 WS) was built into a slit lamp light source. The magnifying optics consisted of a Zeiss Luminar objective (f = 16 mm) with a 15 cm extension tube, Zeiss Zusatz magnifier ( x 2), a final extension tube (8 cm) and a camera with a clear viewfinder. The angle of

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illumination was constant, 50 degrees. The same endothelial cell area could be photographed repeatedly in some cases by also using the same eye for fmation. The negatives were printed at eight times magnification for inspection.

Results

Specular microscopy presented a normal reflection of the central endothelial mosaic in all the volunteers before the SCL insertion. Slight discomfort and redness of the eyes were noted during SCL wear. No changes were observed in the epithelium during or after SCL wear.

In 4 eyes the endothelium remained intact during SCL wear (Fig. 1). The

Fig. 3 . Photograph showing moderate changes in the corneal endothelium after SCL wear. Blebs and indistinct cell junctions appear at 6 to 15 rnin after SCL insertion. Specular reflection is

normalized 26 rnin after SCL removal. x 160.

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Fig. 4. Photograph showing extensive changes. Four minutes after SCL insertion the endothelial reflection is blurred. Several blebs are seen at 18 and 25 rnin. After SCL removal recovery

starts quickly and the blebs disappear after 15 min. x 160

remaining 17 eyes developed endothelial changes. The endothelial reaction was graded according to the disappearance of specular reflection as slight, moderate or extensive. Six subjects presented slight changes, endothelial cells with blurred reflection and thickened cell junction areas (Fig. 2). When the endothelium presented slight changes together with black nonreflecting areas of one to two endothelial cells in size the reaction was considered moderate (Fig. 3). Moderate changes were observed in 9 subjects. The increase in size and number of nonreflecting areas in 2 subjects represented extensive changes (Fig. 4). The observed endothelial changes appeared to be similar in both sexes.

The onset of endothelial changes was rapid after SCL insertion. Slight changes were observed within 4 min of the lens insertion. Nonreflecting small black areas,

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when present, appeared after 4-10 min. The number and size of blebs increased during SCL wear and the reaction reached a maximum after 15-40 min. After removal of the SCL the endothelial cells of all the volunteers returned to normal in appearance from 3 to 30 min. Some subjects offered a landmark in the endothe- lium and we were able to document the onset and recovery of the same endothelial changes. No endothelial cell loss seemed to accompany the recovery of the endothelial changes.

Discussion

Visualization of the corneal endothelium with a slit lamp was introduced by Vogt (1930). Using this principle, the endothelium can also be photographed with modern equipment, and blebs or non reflecting areas in the endothelium have been documented soon after CL insertion in unadapted eyes (Zantos & Holden 1977). However, this finding has not been widely accepted, because it is believed that CL wear does not affect the endothelium. It has been shown that the corneal stroma and endothelium remain clear for months if the epithelium is replaced by a plastic CL glued to the stroma (Kaufman & Gasset 1969). Thus aqueous can support endothelial cells to maintain stromal dehydration.

In our study blebs were easily documented after the insertion of a SCL with our specular microscope. Blebs are not reflections from the epithelial surface because they remain visible if the angle of illumination is changed. Bleb areas recover to normal appearance soon after CL removal. We were able on several occasion to document that there was no endothelial cell loss.

It is thought that under normal open eye conditions the corneal endothelium receives its oxygen from the aqueous (Riley 1969; Fatt et al. 1974). However, there are different opinions on this point and the results of oxygen electrode measure- ments are a matter of some discussion. Another experimental work indicates that under open eye conditions the oxygen flux comes from the atmosphere (Barr & Roetman 1974; Barr et al. 1977). Seventeen of 21 eyes presented transient changes in their central endothelial mosaic due to SCL wear. The rapid appearance and recovery of blebs need more etiologic investigation.

The CL cornea bearing relationship, steep or flat fit, affects the lens movement but not tear pumping under the lens (Wagener et al. 1980). Therefore the circumtances for bleb formation were propably fairly uniform. The variation in the bleb response between different eyes can not be explained, but it is interesting that reduced oxygen availability at the precorneal surface causes an increase in corneal thickness with wide individual variation (Mandell & Farrell 1980). There also seems to be inter species variation in the bleb response, because we have been unable to produce blebs in rabbits with a corresponding stimulus.

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Normally, the posterior endothelial cell surface is slightly convex in electron microscopy (Hodson 1968). I f a contact lens is worn at surgery, irregularity in this contour together with edematous changes can be observed in electronmicroscopy after enucleation (Vannas et al. 1979). Most of the light in specular microscopy is reflected from the endothelial - aqueous interface (Laing 1979). Conceivably slight undulation of the posterior, aqueous facing cell membrane could deflect the light away from the objective lens. However, why some endothelial cells react more vigorously than others is still to be explained. Further work on human corneas is needed for better understanding of the bleb phenomenon.

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Author’s address:

Antti Vannas, Eye Department, University of Helsinki, 00290 Helsinki 29, Finland

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