In this study, physiological EAPPTT reference intervals were established for clinically healthy Akkaraman sheep and Damascus goats. The absence of significant differences between right and left eyes allowed bilateral data to be pooled for breed-specific reference interval estimation. The EAPPTT was well tolerated in all animals, and no ocular complications were observed, supporting its practical applicability in small ruminant ophthalmology.
The EAPPTT offers several procedural advantages over conventional tear tests. Although the STT and PRTT are widely used in veterinary ophthalmology 3,20,21, STT strips may cause mechanical irritation and reflex tearing, whereas the flexible PRTT thread may require forceps for stable placement 3,6,22. In contrast, the relatively rigid and conical structure of the endodontic paper point enables rapid, atraumatic, and forceps-free placement by a single operator 2,3,8.
The maximum wetting value observed in this study was 18 mm, which remained below the 28 mm capacity of the paper points. This supports the use of the 15-second protocol, which was selected to prevent saturation and maintain measurement sensitivity in small ruminants with relatively high tear production.
Because previous EAPPTT data are not available for Akkaraman sheep or Damascus goats, the present findings were interpreted in relation to previously reported STT and PRTT values in small ruminants. Previous studies report 60-second STT means ranging from 10.6 to 18.8 mm/min 4,17,19, whereas 15-second PRTT values may exceed 20 mm in various breeds 4. The EAPPTT values obtained in the present study may reflect the high wicking capacity and narrow surface area of the paper points, which can produce a greater wetting length for a given tear volume 23.
Beyond the physical properties of the EAPPTT material, the reference values observed in Akkaraman sheep may reflect breed-specific ecological adaptations. Variations in tear production reported in other ovine populations 12,16 indicate that lacrimal physiology is influenced by both genetic and environmental factors 10,12. Given the Akkaraman breed's adaptation to the harsh, drought-prone continental climate of Central Anatolia 13, the relatively high tear production observed in this study may represent a compensatory response to increased evaporation and the risk of ocular surface desiccation. This interpretation is consistent with lacrimal patterns described in other arid-adapted species, such as the Barbary sheep 24.
Similarly, the reference values observed in Damascus goats should be interpreted in the context of their adaptation to arid climates 15. Tear production values reported in other caprine species show considerable variation 17,25. The values obtained in the present study are comparable to those reported for arid-adapted species such as the Nubian ibex 26. In combination with the high absorptive capacity of the EAPPTT material 2, this pattern may reflect an adaptive response of the lacrimal unit to increased thermal and evaporative stress, contributing to the maintenance of ocular surface homeostasis under harsh environmental conditions. However, these interpretations should be considered cautiously because the present study was not designed to directly test the effects of climate, season, age, or sex on tear production.
Although this study provides the first physiological EAPPTT reference values for Akkaraman sheep and Damascus goats, several limitations should be acknowledged. First, only clinically healthy animals were included; therefore, tear dynamics in ocular diseases such as infectious keratoconjunctivitis were not evaluated. Second, although measurements were performed within the same time interval and under comparable field conditions, objective environmental parameters, such as ambient temperature, relative humidity, and airflow, were not recorded. This may have introduced unexplained variability and reduced the reproducibility of measurements under different environmental conditions. Third, the study population included animals aged 1-8 years, but age-based subgroup analysis was not performed. In addition, although sex distribution was recorded, sex was not analyzed as an independent variable because the study was not primarily designed to evaluate sex-related differences in tear production. Moreover, the number of male and female animals was not balanced within each breed group, which limited the statistical reliability of sex-based subgroup comparisons. All measurements were performed by a single trained investigator to minimize procedural variability; however, inter-observer agreement was not assessed. Future studies should evaluate inter-observer reliability using approaches such as the intraclass correlation coefficient or Bland-Altman analysis and should include balanced sex distributions, age-stratified analyses, and objective environmental monitoring. Finally, the 15-second EAPPTT protocol requires further validation against the standard 60-second applications and conventional tear tests such as STT and PRTT.
In conclusion, the EAPPTT represents a rapid, atraumatic, and practical method for assessing tear production in small ruminant ophthalmology. The breed-specific reference values established for Akkaraman sheep and Damascus goats provide baseline data that may support ocular surface evaluation and the diagnosis of tear film disorders such as keratoconjunctivitis sicca in both field and clinical settings.
)
)
