Short-term corneal changes with gas-permeable contact lens wear in keratoconus subjects: a comparison of two fitting approaches / Cambios corneales a corto plazo con el uso de lentes de contacto permeables al gas en sujetos con queratocono: comparación entre dos procedimientos de adaptación

Purpose: To evaluate changes in anterior corneal topography and higher-order aberrations (HOA) after 14-days of rigid gas-permeable (RGP) contact lens (CL) wear in keratoconus subjects comparing two different fitting approaches. Methods: Thirty-one keratoconus subjects (50 eyes) without previous history of CL wear were recruited for the study. Subjects were randomly fitted to either an apical-touch or three-pointtouch fitting approach. The lens’ back optic zone radius (BOZR) was 0.4 mm and 0.1 mm flatter than the first definite apical clearance lens, respectively. Differences between the baseline and post-CL wear for steepest, flattest and average corneal power (ACP) readings, central corneal astigmatism (CCA), maximum tangential curvature (KTag), anterior corneal surface asphericity, anterior corneal surface HOA and thinnest corneal thickness measured with Pentacam were compared. Results: A statistically significant flattening was found over time on the flattest and steepest simulated keratometry and ACP in apical-touch group (all p < 0.01). A statistically significant reduction in KTag was found in both groups after contact lens wear (all p < 0.05). Significant reduction was found over time in CCA (p = 0.001) and anterior corneal asphericity in both groups (p < 0.001). Thickness at the thinnest corneal point increased significantly after CL wear (p < 0.0001). Coma-like and total HOA root mean square (RMS) error were significantly reduced following CL wearing in both fitting approaches (all p < 0.05). Conclusion: Short-term rigid gas-permeable CL wear flattens the anterior cornea, increases the thinnest corneal thickness and reduces anterior surface HOA in keratoconus subjects. Apicaltouch was associated with greater corneal flattening in comparison to three-point-touch lens wear (AU)

Objetivo: Evaluar los cambios en la topografía corneal anterior y las aberraciones de alto orden (HOA) a los 14 días de uso de lentes de contacto rígidas permeables al gas (RGP) en pacientes con queratocono, comparando dos tipos diferentes de adaptación. Métodos: Se incluyó en el estudio a treinta y un sujetos con queratocono (50 ojos), sin historia previa de uso de lentes de contacto. A los sujetos se les aplicó aleatoriamente un procedimiento de adaptación de toque apical o de tres puntos. Radio base (BOZR) de la lente fue de 0,4 mm, y 0,1 mm más plano que las primeras lentes que proporcionaban claridad apical, respectivamente. Se compararon las diferencias entre la visita de inicio y tras el uso de las lentes, de las mediciones de potencia corneal media, en el meridiano más plano y más curvo, el astigmatismo central corneal (CCA), la curvatura tangencial máxima (KTag), la asfericidad de la superficie corneal anterior, las HOA de la superficie corneal anterior y el grosor corneal más fino, utilizando el sistema Pentacam. Resultados: Se encontró un aplanamiento estadísticamente significativo en el tiempo, de las lecturas queratométricas más plana y más curva así como de la potencia media de la córnea, en el grupo de toque apical (todos p < 0,01). Se detectó una reducción estadísticamente significativa de la KTag en ambos grupos tras el uso de lentes de contacto (todas las p < 0,05). Se observó una reducción significativa en el tiempo del CCA (p = 0,001) y de la asfericidad corneal anterior en ambos grupos (p < 0,001). El grosor en el punto corneal más fino se incrementó considerablemente tras el uso de las lentes (p < 0,0001). Se redujeron considerablemente el coma y el error cuadrático medio asociado a las HOA tras el uso de las lentes de contacto con ambos procedimientos de adaptación (p < 0,05). Conclusión: El uso de lentes de contacto rígidas permeables al gas aplana la córnea anterior, incrementa el espesor del punto más fino de la córnea, y reduce las HOA de la superficie anterior en pacientes con queratocono. La adaptación de toque apical está asociada a un mayor aplanamiento de la córnea en comparación con la adaptación tres puntos (AU)

Which soft lens power is better for piggyback in keratoconus? Part II.

PURPOSE: To evaluate how soft lens power affects rigid gas-permeable (RGP) lens power and visual acuity (VA) in piggyback fittings for keratoconus. METHODS: Sixteen keratoconus subjects (30 eyes) were included in the study. Piggyback contact lens fittings combining Senofilcon-A soft lenses of -6.00, -3.00, +3.00 and +6.00 D with Rose K2 RGP contact lenses were performed. Corneal topography was taken on the naked eye and over each soft contact lens before fitting RGP lenses. Mean central keratometry, over-refraction, RGP back optic zone radius (BOZR) and estimated final power as well as VA were recorded and analyzed. RESULTS: In comparison to the naked eye, the mean central keratometry flattened with both negative lens powers (p<0.05 in all cases), did not change with the +3.00 soft lens power (p=1.0); and steepened with the +6.00 soft lens power (p=0.02). Rigid gas-permeable over-refraction did not change significantly between different soft lens powers (all p>0.05). RGP's BOZR decreased significantly with both positive in comparison with both negative soft lens powers (all p<0.001), but no significant differences were found among negative- or positive-powers separately (both p>0.05). Estimated RGP's final power increased significantly with positive in comparison with negative lens powers (all p<0.001), but no significant differences were found among negative or positive lens powers separately (both p>0.05). Visual acuity did not change significantly between the different soft lens powers assessed (all p>0.05). CONCLUSION: The use of negative-powered soft lenses in piggyback fitting reduces RGP lens power without impacting VA in keratoconus subjects.

Short-term corneal changes with gas-permeable contact lens wear in keratoconus subjects: a comparison of two fitting approaches.

PURPOSE: To evaluate changes in anterior corneal topography and higher-order aberrations (HOA) after 14-days of rigid gas-permeable (RGP) contact lens (CL) wear in keratoconus subjects comparing two different fitting approaches. METHODS: Thirty-one keratoconus subjects (50 eyes) without previous history of CL wear were recruited for the study. Subjects were randomly fitted to either an apical-touch or three-point-touch fitting approach. The lens' back optic zone radius (BOZR) was 0.4mm and 0.1mm flatter than the first definite apical clearance lens, respectively. Differences between the baseline and post-CL wear for steepest, flattest and average corneal power (ACP) readings, central corneal astigmatism (CCA), maximum tangential curvature (KTag), anterior corneal surface asphericity, anterior corneal surface HOA and thinnest corneal thickness measured with Pentacam were compared. RESULTS: A statistically significant flattening was found over time on the flattest and steepest simulated keratometry and ACP in apical-touch group (all p<0.01). A statistically significant reduction in KTag was found in both groups after contact lens wear (all p<0.05). Significant reduction was found over time in CCA (p=0.001) and anterior corneal asphericity in both groups (p<0.001). Thickness at the thinnest corneal point increased significantly after CL wear (p<0.0001). Coma-like and total HOA root mean square (RMS) error were significantly reduced following CL wearing in both fitting approaches (all p<0.05). CONCLUSION: Short-term rigid gas-permeable CL wear flattens the anterior cornea, increases the thinnest corneal thickness and reduces anterior surface HOA in keratoconus subjects. Apical-touch was associated with greater corneal flattening in comparison to three-point-touch lens wear.

An assessment of the optimal lens fit rate in keratoconus subjects using three-point-touch and apical touch fitting approaches with the rose K2 lens.

OBJECTIVES: To compare the number of ordered lenses required to achieve an optimal lens fit between three-point-touch and apical touch fittings in keratoconus subjects with nipple and oval cones using the first definite apical clearance lens (FDACL) as a starting point. METHODS: First trial lens was selected following manufacturer's guidelines and the back optic zone radius (BOZR) was flattened or steepened in 0.10 mm steps until a FDACL was found. Subsequently, subjects were randomly allocated to three-point-touch (BOZR 0.10 mm flatter than FDACL) and apical touch fittings (BOZR 0.40 mm flatter than FDACL). Changes were made solely in total lens diameter, edge lift, and/or back vertex power until an optimal lens fit was achieved. Differences between fitting approaches were compared in terms of optimal lens fit rates defined as the percentage of subjects successfully fitted with the first lens ordered from the manufacturer. RESULTS: Sixty-one subjects (109 eyes) were randomly allocated to three-point-touch and apical touch fitting approaches. An average of 2.3 trial lenses were necessary to achieve the FDACL. An optimal lens fit rate was achieved with the first lens in 84 of 109 eyes (77%). No statistically significant differences in optimal lens fit rates were found between three-point-touch and apical touch fitting approaches (83% and 71%, respectively; P = 0.12) and between nipple and oval cones (81% and 68%, respectively; P = 0.12). CONCLUSIONS: The use of the FDACL provides a systematic, reliable, and repeatable starting point for Rose K2 contact lens fitting in keratoconus. Eye care practitioners should anticipate higher optimal lens fit rates when using three-point-touch (83%) in comparison with apical touch contact lens fittings (71%).

Utility of a semi-scleral contact lens design in the management of the irregular cornea.

OBJECTIVES: To evaluate the utility of the Rose K2 XL semi-scleral contact lens (Menicon Co. Ltd., Nagoya, Japan) in the management of the irregular cornea. METHODS: Twenty-seven subjects (34 eyes) with irregular corneas referred for contact lens fitting were evaluated. A diagnostic trial set was used in the fitting process. Once the trial lens was considered optimal, a final lens was ordered from the manufacturer with the necessary changes in power, edge lift and diameter. We analyzed visual acuity, number of lenses ordered and patients' ability to wear and handle lenses. RESULTS: Twenty-three subjects (30 eyes) were fitted with the Rose K2 XL lens. Four subjects (4 eyes) decided not to conclude the fitting process for different reasons. Average logMAR visual acuity without correction and with the lens was 0.82 and 0.09, respectively (p<0.001). An average of 1.4 ordered lenses (range 1-3) were necessary to achieve the optimal fit. Nineteen eyes (63%) were fitted with the first lens ordered. Three subjects (13%) had problems with lens handling, and three subjects (4 eyes) abandoned the wear of the lenses after three months due to discomfort (3 eyes) and unsatisfactory visual acuity (1 eye), respectively. Follow-up ranged from 6 to 9 months. CONCLUSION: Rose K2 XL semi-scleral contact lens provides good visual acuity and comfort in patients with irregular corneas.

The thinnest, steepest, and maximum elevation corneal locations in noncontact and contact lens wearers in keratoconus.

PURPOSE: To assess the relationship between the thinnest corneal location and the steepest and maximum elevation corneal locations in subjects with keratoconus and the effect of gas permeable contact lens wear on the location of these points. METHODS: Sixty-one consecutive subjects (98 eyes) with keratoconus. Thirty-one (49 eyes) and 30 (49 eyes) subjects were gas permeable contact lens (CL-W) and non-contact lens wearers (N-CL), respectively. Thinnest, steepest, and maximum elevation corneal locations were evaluated from topographies collected with Pentacam Eye Scanner. RESULTS: In the entire sample and in N-CL and CL-W, the thinnest location does not overlap with the steepest or maximum elevation corneal locations (all P > 0.05). The thinnest and maximum tangential curvature locations were found to be located further away from the geometric center of the cornea in CL-W versus N-CL (P < 0.05). CONCLUSION: The thinnest corneal location does not overlap with maximum axial and tangential curvatures or with the front and back elevation locations in keratoconus subjects. Contact lens wear does not affect this lack of overlapping.

Which soft contact lens power is better for piggyback fitting in keratoconus?

PURPOSE: To evaluate the impact of differente soft contact lens power in the anterior corneal curvature and regularity in subjects with keratoconus. METHODS: Nineteen subjects (30 eyes) with keratoconus were included in the study. Six corneal topographies were taken with Pentacam Eye System over the naked eye and successively with soft lens (Senofilcon A) powers of -3.00, -1.50, 0.00, +1.50 and +3.00 D. Corneal measurements of mean central keratometry (MCK), maximum tangential curvature (TK), maximum front elevation (MFE) and eccentricity (Ecc) at 6 and 8 mm diameters as well as anterior corneal surface high order aberrations (i.e. total RMS, spherical- and coma-like and secondary astigmatism) were evaluated. RESULTS: Negative- and plano-powered soft lenses flattened (p<0.05 in all cases), whereas positive-powered lenses did not induce any significant changes (p>0.05 in all cases) in MCK in comparison to the naked eye. The TK power decreased with negative lenses (p<0.05 in both cases) and increased with +3.00 D lenses (p=0.03) in comparison to the naked eye. No statistically significant differences were found in MFE with any soft lens power in comparison to the naked eye (p>0.05 in all cases). Corneal eccentricity increased at 8 mm diameter for all lens powers (p<0.05 in all cases). No statistically differences were found in HOA RMS and spherical-like aberration (both p>0.05). Statistically differences were found in coma-like and secondary astigmatism (both p<0.05). CONCLUSION: Negative-powered soft contact lenses provide a flatter anterior surface in comparison to positive-powered lenses in subjects with keratoconus and thus they might be more suitable for piggyback contact lens fitting.

Keratopathy after cross-linking for keratoconus.

PURPOSE: To report 2 cases of keratopathy after uneventful cross-linking procedures for grade 3 keratoconus. METHODS: Two patients (21 and 11 years old) with grade 3 keratoconus underwent uneventful cross-linking in 1 eye. In both patients, multiple peripheral stromal precipitates, which extended centripetally, were observed 48 hours after the procedure. Sample cultures were negative for bacteria, fungi, and parasites. RESULTS: Cornea infiltrates slowly resolved after combined topical antibiotic/antifungal/povidone/steroids treatment. Final best spectacle-corrected visual acuity was 20/25 for patient 1, after uneventful bilateral toric intraocular contact lens (ICL) (Staar Surgical) implantation, but faint and paracentral scarring persisted. Final best-corrected visual acuity was 20/25 for patient 2 with gas-permeable contact lens wear, despite stromal scarring. CONCLUSIONS: Cross-linking associated with sterile keratitis is an unusual entity of unknown etiology, which can lead to stromal scarring.

Keratoconus: a review.

Keratoconus is the most common primary ectasia. It usually occurs in the second decade of life and affects both genders and all ethnicities. The estimated prevalence in the general population is 54 per 100,000. Ocular signs and symptoms vary depending on disease severity. Early forms normally go unnoticed unless corneal topography is performed. Disease progression is manifested with a loss of visual acuity which cannot be compensated for with spectacles. Corneal thinning frequently precedes ectasia. In moderate and advance cases, a hemosiderin arc or circle line, known as Fleischer's ring, is frequently seen around the cone base. Vogt's striaes, which are fine vertical lines produced by Descemet's membrane compression, is another characteristic sign. Most patients eventually develop corneal scarring. Munson's sign, a V-shape deformation of the lower eyelid in downward position; Rizzuti's sign, a bright reflection from the nasal area of the limbus when light is directed to the limbus temporal area; and breakages in Descemet's membrane causing acute stromal oedema, known as hydrops, are observed in advanced stages. Classifications based on morphology, disease evolution, ocular signs and index-based systems of keratoconus have been proposed. Theories into the genetic, biomechanical and biochemical causes of keratoconus have been suggested. Management varies depending on disease severity. Incipient cases are managed with spectacles, mild to moderate cases with contact lenses and severe cases can be treated with keratoplasty. This article provides a review on the definition, epidemiology, clinical features, classification, histopathology, aetiology and pathogenesis, and management and treatment strategies for keratoconus.