Effects of fibrovascular traction and pooling of tears on corneal topographic changes induced by pterygium

Abstract

Aim To investigate the effects of fibrovascular traction and the pooling of tears at the pterygium apex on the corneal topographic changes induced by pterygium. Methods A total of 16 eyes of 14 cases with primary pterygium were included in the study. A computerized corneal topography system was used for corneal topography examinations. Baseline keratographs were taken two times at straight gaze. A repeat corneoscope photograph was immediately obtained in temporal gaze. Then the tears at the pterygium apex were dried with a cellulose sponge, and a new corneoscope photograph was immediately obtained without allowing one to blink. Corneal topographic maps (numeric maps) were divided into 301 fields in 24 meridians. One colour was allocated to each field, representing its mean refractive power for all groups. In all eyes, keratometric astigmatism at the 3 mm central cornea and total mean corneal refractive power were found. Data were compared using pairedsamples two-tailed t-tests.Results Keratometric astigmatism at the 3 mm central cornea was significantly reduced at the temporal gaze (3.1072.34 D, t ¼ 3.40, P ¼ 0.027) and dried eyes (2.1271.01 D, t ¼ 4.74, P ¼ 0.001) according to the first baseline measurement (4.3171.91 D) of the total mean corneal refractive power was found to be 43.4571.28 D (39.29-45.87) at the first baseline measurement. There was no change at the temporal gaze (43.5471.06 D, P40.05). However, the total corneal refractive power was significantly higher in dried eyes (44.2670.93 D, t ¼ 34.92, Po0.001). The steepest region of corneal topography was a superior quadrant, and the flattest area was a nasal quadrant at the baseline. At the temporal gaze, the cornea was significantly flatter in the superior and inferior sides of the pterygium meridian. After dried pooling of tears, topographic abnormalities returned, and the cornea became more uniform and symmetric. Conclusion We conclude that the pooling of tears at the pterygium apex plays an important role, but fibrovascular traction has no effect on the corneal topographical changes induced by pterygium.

Effects of pterygium surgery on front and back corneal surfaces and anterior segment parameters

“…Pterygium-induced corneal flattening and its topographic changes have been attributed to the pooling of tears at the pterygium apex or to the mechanical traction by the pterygium fibrovascular tissue [1,30]. A recent study by Yasar et al emphasized the role of tear pooling by ruling out the effects of mechanical traction [31]. However, changes in the back corneal surface, as observed in our study, reveal that at least some of the pterygium-induced topographic changes are due to alterations in the corneal shape which are reversed after surgery.…”

Tear function and goblet cell density after pterygium excision

“…For tear dynamics, a recent study has shown that there is a pooling of tears at the pterygium apex as evidenced by the significantly increased total corneal refractive power after the tears were dried. 22 The pooling of tears, presumably caused by the protrusion of pterygial lesion, can disturb the distribution of tear film on the ocular surface. It is still unclear whether the tear volume plays a role in the abnormal tear function in pterygia patients.…”

Radial Descemet's membrane folds as a sign of pterygium traction

“…In our patient, fibrovascular traction was the cause of structural and topographic corneal changes even though the pooling of tears at the pterygium head is known to play an important role on corneal topography in most cases. 7 Even though preoperative automated keratometry showed a high with-the-rule astigmatism on the right side, the patient's subjective refraction was spherical. It is known, however, that the induced irregular astigmatism caused by pterygia is not always apparent by subjective refraction.…”