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PURPOSE: To estimate the time taken for topometric indices to stabilize in keratoconic corneas following cessation of habitual RGP contact lens wear. METHODS: A total of 29 eyes of 20 patients, diagnosed with mild to severe keratoconus were included in this prospective observational study. All patients were experienced RGP contact lens wearers (either conventional RGP or Rose K2 lens) with each patient having used these lenses for at least a year. Corneal topography was performed immediately following discontinuation of habitual contact lens wear at baseline and each of four consecutive visits, 1-week apart. RESULTS: An overall reduction in the keratometry and thickness values were noted on tomography immediately following cessation of contact lens wear and these indices increased significantly in the 1st week (P < 0.001). Consecutive visits following the first visit did not show any significant change in the topometric parameters (P > 0.05). Subgroup analysis revealed a similar trend in eyes with "severe" keratoconus and in eyes fitted with the "three-point touch" philosophy. However, eyes with "mild-moderate" keratoconus and those fitted with "apical clearance" fitting philosophy showed marginal differences even within the 1-week period of lens cessation. CONCLUSION: Maximum changes in keratometry and pachymetry values following discontinuation of RGP lens wear stabilize within the 1st week of cessation of rigid lens wear in a keratoconic cornea. These changes were more pronounced in patients with severe keratoconus and those with an apical bearing fit. This information would be useful for practitioners to assess the progression of keratoconus in RGP lens users before collagen cross-linking.

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PURPOSE: To investigate the effect of lens centre thickness (and mass) upon short-term horizontal and vertical scleral lens decentration, and the association between both scleral topography and apical clearance, with lens decentration. METHODS: Lens decentration was measured using over-topography data from 9 healthy young participants (25 ± 4 years) with normal corneae fitted with ICD 16.5 scleral lenses (hexafocon B material) with centre thicknesses of 150, 250, and 350 µm, while controlling for other lens parameters. Scleral toricity and elevation were determined from sagittal height data over a 15 mm chord obtained from a corneo-scleral topographer and central apical clearance was quantified using anterior segment optical coherence tomography. RESULTS: The mean lens decentration was 0.55 ± 0.19 mm temporally and 0.84 ± 0.35 mm inferiorly, which did not vary significantly with centre thickness (p > 0.05). The mean nasal-temporal asymmetry in scleral elevation data was substantially greater (619 ± 67 µm) compared to the vertical meridian (369 ± 57 µm) (p < 0.01), and this variation in scleral topography along the horizontal meridian was associated with the magnitude of horizontal lens decentration (r = 0.68, p = 0.04). Greater initial central apical clearance was associated with more inferior lens decentration (r = -0.78, p = 0.01). CONCLUSION: Lens centre thickness and mass did not significantly influence centration. Horizontal lens decentration was associated with the nasal-temporal asymmetry in scleral elevation, while vertical lens decentration correlated with initial central apical clearance. Factors affecting scleral lens centration may vary between the horizontal and vertical meridians.

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PURPOSE: To describe patterns of prescribing Prosthetic Replacement of Ocular Surface Ecosystem (PROSE) in irregular corneas and compare various components of lens design. METHODS: Design: Retrospective, observational case series. 244 eyes of 173 patients with keratoconus (n=178), pellucid marginal degeneration (n=21), keratoglobus (n=6), following refractive surgery (n=19) and following keratoplasty (n=20) fitted with the PROSE device were retrospectively analyzed. Simulated keratometry value along the steep meridian (Steep-K) and anterior chamber depth (ACD) were measured using Scheimpflug imaging. Improvement in visual acuity and parameters of lens design such as vault, front surface eccentricity (FSE) and toricity were analyzed and compared across all conditions. RESULTS: PROSE improved visual acuity, both uncorrected (median, 1.30 logMAR) and spectacle-corrected (median, 0.60 logMAR), to a median of 0.22 logMAR. Positive correlation was observed between Steep-K and ACD with lens vault, especially in keratoconus. Multiple regression analysis established ACD as the most reliable factor while choosing vault. FSE value of 0.6 was the most common across diagnostic subgroups. The distribution of FSE values did not differ between keratoconus patients with Steep keratometry of <60D or those >60D. In every diagnostic subgroup, at least 20% of eyes required a lens design of with-the-rule toricity of haptic. CONCLUSION: The PROSE device resulted in significant improvement in vision in this population. A trend of prescribing higher lens vault with increased keratometry value was evident especially in keratoconus. ACD appeared to be more important than Steep K in vault selection. An FSE of 0.6 and vertical peripheral lens toricity were used most frequently in this subset of patients.

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PURPOSE: The aim of this study was to show the potential applicability of optical coherence tomography angiography (OCTA) for the evaluation of the peripheral fitting of fully scleral contact lenses. METHODS: A pilot study was proposed fitting three different scleral contact lenses (Irregular Corneal Design [ICD]) with different sagittal heights (4200, 4800, and 5600 mm) in a healthy volunteer of 27 years old. We evaluated by means of optical coherence tomography (OCT, DRI Triton) the apical clearance achieved with each of the three lenses fitted. The impact over scleral flow was assessed with the OCTA module of the same device. RESULTS: The apical clearance was 310, 901, and 1680 µm with the scleral lenses of sagittal heights 4200, 4800, and 5600 µm, respectively. With OCTA, we evaluated the impact of the lens bearing on the conjunctival vascular flow, observing an area of vascular interruption of 0, 25, and 75% with the lenses of 4200, 4800, and 5600 µm of sagittal heights, respectively. The vascular interruption was induced in the perilimbar area, suggesting the need of readjusting the limbal clearance zone of the lens. CONCLUSION: Fully scleral contact lens fitting may be optimized with the use of OCTA, allowing the practitioner to perform the fitting with better control of the peripheral bearing of the lens on the conjunctival tissue, assessing the impact on vascular structures. This potential use of OCTA must be investigated further in future studies including large samples of eyes.