Corneal changes after suspending contact lens wear in early pellucid marginal corneal degeneration and moderate keratoconus.

OBJECTIVES: This case study reports on how refraction, visual acuity, and ocular higher-order aberrations changed after rigid gas-permeable (RGP) lens wear was suspended by a patient with early pellucid marginal corneal degeneration (PMD) and by a patient with moderate keratoconus. Alterations in central corneal power and axes, central corneal thickness, and corneal topography were also explored. METHODS: Ocular aberrations and Scheimpflug photography were measured at 2 visits, 7 days apart, after the patients had removed their contact lenses. Subjective refraction and logarithm of the minimum angle of resolution visual acuities were also recorded at both visits. RESULTS: In contrast to the keratoconic patient, the patient with early PMD showed changes in subjective refraction (approximately -1.75 diopter cylinder of astigmatism), front surface central powers (∼1.3 diopter [D] horizontally and 2 D vertically), and anterior surface topography (∼1.2 D) between visits. Both patients showed an increase in total higher-order root mean square (HORMS) aberrations after suspending lens wear (∼0.40 µm for the moderately keratoconic patient and 0.22 µm for the early PMD patient). CONCLUSIONS: Changes in the optical and structural parameters of the cornea after suspending lens wear are likely to be dependent on a multitude of factors, such as the lens fitting and the biomechanical properties of the cornea. The findings of this report may be useful to practitioners when refracting or refitting existing RGP lens wearers with ectasia or to those involved in prescribing aberration-controlling contact lenses for conditions such as keratoconus and PMD.

Adapting to blur produced by ocular high-order aberrations.

The perceived focus of an image can be strongly biased by prior adaptation to a blurred or sharpened image. We examined whether these adaptation effects can occur for the natural patterns of retinal image blur produced by high-order aberrations (HOAs) in the optics of the eye. Focus judgments were measured for 4 subjects to estimate in a forced choice procedure (sharp/blurred) their neutral point after adaptation to different levels of blur produced by scaled increases or decreases in their HOAs. The optical blur was simulated by convolution of the PSFs from the 4 different HOA patterns, with Zernike coefficients (excluding tilt, defocus, and astigmatism) multiplied by a factor between 0 (diffraction limited) and 2 (double amount of natural blur). Observers viewed the images through an Adaptive Optics system that corrected their aberrations and made settings under neutral adaptation to a gray field or after adapting to 5 different blur levels. All subjects adapted to changes in the level of blur imposed by HOA regardless of which observer's HOA was used to generate the stimuli, with the perceived neutral point proportional to the amount of blur in the adapting image.

Corneoscleral contact lenses fitting on irregular corneas after laser-assisted in situ keratomileusis.

PURPOSE: We aimed to describe the outcomes of corneoscleral contact lens fitting with multi-aspherical geometry designs in patients with irregular corneas after laser-assisted in situ keratomileusis (LASIK). METHODS: This was a retrospective series of 18 patients (age, 26-38 years) selected from an eye clinic database. Participants were required to have unsatisfactory visual acuity with their current contact lenses or spectacles after LASIK for myopia correction. All patients were fitted with corneoscleral contact lenses designed to correct corneal surface irregularities. A diagnostic trial set was used for fitting, and assessments were performed according to a standardized methodology. Subjective comfort, visual acuity, central corneal thickness, endothelial cell count, and corneal-compensated intraocular pressure were evaluated. The follow-up period was one year. RESULTS: Contact lens use was discontinued in 3 patients, thus leaving 24 eyes from 8 females and 7 males for analysis. The fitting characteristics were optimal in terms of lens position and movement. Statistically significant improvements were found in the best spectacle-corrected vision from before fitting to the visual acuity after fitting (p<0.001). Moreover, the patients reported high subjective comfort ratings and usage times (12.98 ± 2.3 hours/day). After one year of wear, visual acuity, subjective comfort, and usage time were maintained. No statistically significant adverse changes developed in the corneas over this period. CONCLUSION: Corneoscleral contact lenses with a multi-aspherical geometry design provide optimal visual acuity, improved comfort, and prolonged usage times in patients with irregular corneas after LASIK.

Efficacy of spherical aberration correction based on contact lens power.

PURPOSE: To investigate the efficacy of spherical aberration (SA) correction with aspheric contact lenses (aspheric lenses) based on lens power, and compare the results with those of spherical contact lenses (spherical lenses). METHODS: Ocular higher-order aberrations were measured with a wavefront sensor, in 11 myopic subjects wearing an aspheric lens (Medalist Fresh fit (PUREVISION 2 HD); Bausch+Lomb) or a spherical lens (ACUVUE Oasys; Johnson & Johnson). Six different lens powers (-7.00 diopters (D), -5.00 D, -3.00 D, -1.00 D, +1.00 D, +3.00 D) were used for all subjects. The amount of SA correction from the contact lens at each power was calculated as the difference between SA with the contact lens on-eye and SA of the eye alone. RESULTS: For the spherical lenses, SA correction was close to 0.00 µm for the +1.00 D lens, became more positive as the labeled lens power increased and became more negative as the labeled lens power decreased. For the aspheric lenses, SA correction was consistent, from -0.15 to -0.05 µm, for all lens powers except for the -1.00 D lens. SA correction for the spherical and aspheric lenses was significantly different at -7.00 D (p=0.040), -3.00 D (p=0.015), -1.00 D (p<0.001), +1.00 D (p=0.006), and +3.00 D (p<0.001) powers. CONCLUSION: An aspheric lens is capable of correcting SA at different lens powers, and has SA correction in the range of -0.15 to -0.05 µm over a 6mm aperture.

Corneoscleral contact lenses fitting on irregular corneas after laser-assisted in situ keratomileusis / Lentes de contato corneoesclerais adaptadas em córneas irregulares após cirurgia LASIK

ABSTRACT Purpose: We aimed to describe the outcomes of corneoscleral contact lens fitting with multi-aspherical geometry designs in patients with irregular corneas after laser-assisted in situ keratomileusis (LASIK). Methods: This was a retrospective series of 18 patients (age, 26-38 years) selected from an eye clinic database. Participants were required to have unsatisfactory visual acuity with their current contact lenses or spectacles after LASIK for myopia correction. All patients were fitted with corneoscleral contact lenses designed to correct corneal surface irregularities. A diagnostic trial set was used for fitting, and assessments were performed according to a standardized methodology. Subjective comfort, visual acuity, central corneal thickness, endothelial cell count, and corneal-compensated intraocular pressure were evaluated. The follow-up period was one year. Results: Contact lens use was discontinued in 3 patients, thus leaving 24 eyes from 8 females and 7 males for analysis. The fitting characteristics were optimal in terms of lens position and movement. Statistically significant improvements were found in the best spectacle-corrected vision from before fitting to the visual acuity after fitting (p<0.001). Moreover, the patients reported high subjective comfort ratings and usage times (12.98 ± 2.3 hours/day). After one year of wear, visual acuity, subjective comfort, and usage time were maintained. No statistically significant adverse changes developed in the corneas over this period. Conclusion: Corneoscleral contact lenses with a multi-aspherical geometry design provide optimal visual acuity, improved comfort, and prolonged usage times in patients with irregular corneas after LASIK.

RESUMO Objetivo: Descrever os resultados do ajuste de lentes de contato corneoesclerais com geometria multiasférica em pacientes com córneas irregulares após cirurgia de ceratomileuse in situ assistida por laser (LASIK). Métodos: Esta foi uma série retrospectiva de 18 pacientes (idade, 26-38 anos) selecionados a partir de um banco de dados de uma clínica oftalmológica. Os participantes foram escolhidos ao manifestaram acuidade visual insatisfatória com suas lentes de contato ou óculos atuais depois de terem sido submetidos à LASIK para correção de miopia. Todos os pacientes receberam lentes de contato corneoesclerais projetadas para corrigir irregularidades na superficie da córnea. Um conjunto diagnóstico de prova foi usado para a adaptação e as avaliações foram feitas de acordo com uma metodologia padronizada. O conforto subjetivo, a acuidade visual, a espessura central da córnea, a contagem de células endoteliais e a pressão intraocular compensada da córnea foram avaliados. O período de acompanhamento foi de um ano. Resultados: O uso de lentes de contato foi descontinuado em 3 pacientes, deixando 24 olhos de 8 mulheres e 7 homens para análise. As características de adaptação foram ótimas em termos de posição e movimento da lente. Melhorias estatisticamente significativas foram encontradas na melhoria da visão corrigida por óculos antes de se ajustar a acuidade visual após a adaptação (p<0,001). Além disso, os pacientes relataram altos índices subjetivos de conforto e tempo de uso (12,98 ± 2,3 horas/dia). Após um ano de uso, a acuidade visual, o conforto subjetivo e o tempo de uso foram mantidos. Não houve alterações adversas estatisti­camente significativas nas córneas ao longo deste período. Conclusão: As lentes de contato corneoesclerais com projeto geométrico multiasférico proporcionam acuidade visual ideal, maior conforto e tempo de uso prolongado em pacientes com córneas irregulares após o LASIK.