Reshaping The Cone: Topography Guided Custom Ablation Treatment For Corneal Regularisation-Two Case Reports

Keratoconus is a progressive ectatic disorder characterised by corneal thinning and irregular astigmatism, often causing poor spectacle correction and contact lens intolerance. Topography-guided custom ablation (T-CAT) regularises the corneal surface, while corneal collagen cross-linking (CXL) enhances biomechanical stability. This report presents two cases of moderate keratoconus treated with simultaneous T-CAT and CXL, demonstrating improvements in vision, corneal shape, and higher-order aberrations. Ideal candidates have stable moderate ectasia (pachymetry >450 μm, no scarring), whereas advanced, thin, or scarred corneas should be avoided to ensure optimal outcomes.

At our centre, the two cases met the criteria: thinnest pachymetry >450 μm, no central scarring, irregular astigmatism on tomography. Preoperative Snellen UCVA/BCVA, tomography, and aberrometry were assessed.The visual acuity and refractive correction:

Case1: Right eye: UCVA 6/24, BCVA 6/9 (-1.00DS/-6Dcyl@170°). Left eye: UCVA 6/60, BCVA 6/12 (-2.50DS/-8.00Dcyl@170°).

Case2: Right eye: UCVA 6/18p, BCVA 6/9 (-2.50DS/-2.00Dcyl@30°). Left eye: UCVA 6/18, BCVA 6/6p (-2.00DS/-2.25Dcyl@180°)

The procedure began with the instillation of proparacaine 0.5% eye drop. A 8-mm zone

of corneal epithelium was removed using Excimer LASER Phototherapeutic Keratectomy.

A customized topography-guided ablation was then performed.. Data from five

tomographies were averaged to guide the ablation, and the optical zone diameter was set to 5.5 mm.

Maximum ablation was limited to 40 μm in the thinnest corneal region, and Zernike optimisation

was applied to match defocus (C4) and spherical aberration (C12), keeping the refractive correction

as zero.Post ablation isotonic riboflavin applied q2 min x 20 min,Collagen Crosslinking for Keratoconus

(UVA irradiation 365 nm, 9 mW/cm²)10min,done then irrigated with cold BSS and cold BCL applied

Case1:

In the first case, a reduction of 6.34 D cylindrical (Dcyl) and 6.25 Dcyl in the steep K reading was

observed in the right and left eyes, respectively, at the 6-month follow-up. UCVA improved and

remained stable up to 6 months post-operatively.

Case2:

In the second case, a reduction of 2.75 Dcyl and 5.21 Dcyl in the steep K readings was noted in the

right and left eyes, respectively, at 6 months. The patient’s UCVA showed significant

improvement, which remained stable for up to 18 months post-operatively.

Both demonstrated decreased cylinder and higher-order aberrations, contributing to

enhanced visual quality. Improvements in corneal tomoography were confirmed.

Tomographer, showing more regular corneal surfaces post-procedure.

Concurrent topography-guided custom ablation (T-CAT) and corneal collagen crosslinking (C3R) provide complementary KC management, enhancing structural integrity while correcting surface irregularity. Custom ablation smoothens the ectatic peak and steepens periphery to restore corneal contour, using minimal tissue removal to safeguard thickness and optimise vision,

Simultaneous T-CAT and C3R appear to be an effective modality for treating moderate keratoconus.

It has the advantage of improved predictability of refractive

outcomes due to ablation of non-crosslinked tissue

resulting in significant improvements in corneal regularity, UCVA, and BCVA. however further studies are

needed to assess long-term biomechanical and topographical stability.