Topographic Astigmatism After Deep Anterior Lamellar Keratoplasty: Orientation, Power, And Correlation With Preoperative Values

To evaluate the postoperative changes in the axis orientation and power of topographic astigmatism in eyes undergone deep anterior lamellar keratoplasty (DALK) for keratoconus, and to investigate eventual correlations with preoperative astigmatism.

Patients underwent big-bubble DALK between 2011 and 2023 by the same experienced surgeons (V.S. and A.L.) at the department of ophthalmology of the “Magna Graecia” University of Catanzaro in Italy.

This retrospective study included patients with keratoconus who did not achieve satisfying visual acuity using spectacles or contact lenses or were intolerant. Eyes undergone corneal, vitreoretinal, or refractive surgery, as well as those affected by any ocular or systemic disease that could interfere with surgical outcomes were excluded from the study. Topographic astigmatism was evaluated using the anterior segment optical coherence tomography CASIA SS-1000 (Tomey, Tokyo, Japan). Astigmatism axis and power were evaluated preoperatively (T0), 1 week after surgery (T1) and at about 1 year, at least 1 month after the complete removal of sutures (T2).

In total, 290 eyes (261 patients) underwent DALK. Preoperative axis orientation was with-the-rule in 123 eyes, against-the-rule in 60, and oblique in 107. In the first two groups orientation remained unchanged at T2, respectively in 47.2% (n=58) and 48.3% (n=29) of cases. An axis change ≤30 degrees was reported in 137 eyes (47.2%) between T0 and T2, and in 114 eyes (39.3%) between T1 and T2. The difference was statistically significant (P=0.05). A significant reduction in astigmatism power at T2 was exclusively reported if preoperative orientation was with-the-rule (5.11±2.85 dioptres [95% CI, 2.31-7.90] vs 4.54±3.12 dioptres [95% CI, 1.48-7.59]; P=0.02).

One year after DALK, astigmatism axis tends to align more closely with its preoperative orientation than with measurements taken one week postoperatively. This correlation may be useful in surgical planning, especially for managing corneal suture tension and optimize postoperative outcomes.