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Michael Korchak, Sandra Lora Cremers, Jenny Ha, Jayson Koppinger, Jesus Alberto Martinez; Tracking Changes in Corneal Tomography After Pterygium Excision to Aid Planning Future Refractive Surgery. Invest. Ophthalmol. Vis. Sci. 2016;57(12):3538.
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© ARVO (1962-2015); The Authors (2016-present)
There is no consensus in the literature regarding when corneal tomography stabilizes after pterygium excision. We performed a retrospective study to examine the effects of pterygium removal on corneal tomography and determine when structural stability is achieved.
This study of 43 eyes undergoing pterygium excision reviewed data before and after surgery (2 weeks, 1 month, 2 months, and 3 months). Corneal tomography data was obtained using Pentacam (Oculus Inc) and included anterior and posterior keratometry (K), astigmatism, corneal axis, pachymetry, anterior chamber depth, chamber volume, and corneal volume. Statistical analyses (SPSS V23.0 for Windows) included paired t-tests to compare all visits. Subgroup analysis divided eyes by those with <1D or ≥1D of astigmatism and used Wilcoxon Signed Rank Test to compare all visits for each group. A p value <0.05 was considered statistically significant.
In our cohort, the anterior flat K increased from preop to 2w (p=0.02) but stabilized thereafter (all p>0.05 between later visits; Figure 1). The anterior steep K increased from pre-op to post-op week 2 (p=0.05) then decreased from 2w to 1m (p=0.018), and did not statistically change afterwards (Figure 1). These results were similar within subgroup analyses. Pachymetry changed between visits until 2m (all p<0.05) but no change was seen between pre-op and 3m (p=0.353). Postoperative astigmatism at 1m, 2m, and 3m was significantly lower than preop (all p<0.05), and stabilized by 1m. Of all data, only pachymetry demonstrated a significant change between 1m and 2m (p=0.014). In eyes with <1D astigmatism, the only significant difference seen between postop visits was pachymetry at 1m vs 3m. In eyes with ≥1D Astig, there were no significant tomographic changes after 1m.
After pterygium excision, changes in keratometry occurred within one month after surgery with no significant changes between later visits. Refractive surgery should be postponed at least one month after pterygium excision to allow for keratometry to stabilize, though further delay may be warranted if a change in pachymetry is observed.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
Figure 1. Means plot demonstrating the changes in the anterior flat K (K1) and steep K (K2) after pterygium excision surgery.
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