THERMAL-GRADIENTS IN THE EYES OF LID-SUTURED CHICKS

Thermal gradients were measured from the cornea to the posterior pole in the eyes of 11 chicks, six of which had the lids of one eye sutured three weeks previously. A comparison was made between eyes that were chronically closed by lid-suture (while still sutured shut) and two ty pes of control eyes: (a) treated controls, which were the non-sutured, contralateral eyes of the lid-sutured chicks and (b) untreated contro ls, which were the eyes of a different group of chicks in which neithe r eye had been sutured. The results indicated that transient closing o f the eyes of normal, untreated chicks (untreated controls) elevated t he ocular temperature by about 1.5-degrees-C at the cornea; the extent of thermal elevation, diminished as the thermoprobe was advanced towa rds the posterior pole. In contrast, when the transiently closed eyes in untreated control chicks were compared with the chronically closed eyes of the lid-sutured chicks, the lid-sutured eyes were cooler by 2- degrees-2.5-degrees. When the sutured lids were opened, however, the e yes were isothermal with the untreated control eyes. Moreover, the eye s of lid-sutured chicks were isothermal with their contralateral, non- sutured, control eyes (treated control), whether in the opened or clos ed state. A comparison of the untreated control eyes and the treated c ontrol eyes revealed no differences (except at the cornea) when the ey es were opened; but when the eyes were closed, the treated control eye s were 2-degrees-3-degrees cooler than the untreated control eyes. The se results indicate that chronic lid suture produces very different ef fects on the thermal properties of the eye than does transient lid clo sure. Chronic lid closure results in a reduction of ocular temperature when the eyes are closed, which may be a consequence of the sutured e ye's reduced need for vascular thermoregulation by the choriocapillari s circulation. The differences between lid suturing, which reduces ocu lar temperature, and the application of goggles, which elevates ocular temperature, are discussed.