Case Report: What Are We Doing for Our “20/20 Unhappy” Scleral Lens Patients?

Abstract

Significance.

Scleral lenses (SLs) partially mask higher order aberrations (HOA) in highly aberrated eyes. While visual acuity (VA) may show satisfactory quantitative clinical outcomes during SL wear, residual (uncorrected) HOAs can leave subjective visual quality goals unmet.

Purpose.

To report a case where a “20/20 unhappy” patient with SLs was able to meet visual goals with wavefront-guided scleral lenses (WGSL).

Case Report.

A 40-year-old male with bilateral keratoconus) whose Snellen VA with SLs was 20/20⁺² right eye (OD) 20/16⁺² left eye (OS), reported halos and glare at night and perceptual smearing. When viewing a point of light, a “Ferris wheel” shadowing was observed by his right eye and a “U” shaped shadowing by his left. Residual higher-order root mean square (HORMS) wavefront error was 0.49 μm OD and 0.39 μm OS; Visual image quality measured by Visual Strehl ratio was 0.067 OD and 0.092 OS (pupil size = 4.00 mm). WGSLs reduced residual HORMS to 0.19 μm OD and 0.25 μm OS, VA improved to 20/10 OD and 20/13 OS; and Visual Strehl improved to 0.150 OD and 0.121 OS. The patient reported reduced smearing, shadowing and night vision concerns, meeting his visual expectations and goals.

Conclusions.

Wavefront sensing quantifies both lower and HOA, which can cause visual dissatisfaction in individuals with highly aberrated eyes, despite sometimes reaching typical levels of VA. As WGSLs targeting these residual aberrations to improve visual image quality become more available, they should be considered for “20/20 unhappy” patients when conventional clinical options are unsatisfactory.

Scleral lenses have become a standard refractive correction option for patients with highly aberrated eyes, such as those with post-refractive surgery ectasia, post-penetrating keratoplasty, corneal trauma, pellucid marginal degeneration, and keratoconus. Conventional scleral lenses mask higher-order aberrations between 60 and 65% ^1,2 through (1) approximate refractive index matching of the post-lens tear layer and the cornea, and (2) by providing a new, well-formed optical first-refracting-surface for light entering the eye. While typical measures of visual performance, such as high contrast visual acuity, may show satisfactory quantitative clinical outcomes, the 35-40% residual (uncorrected) higher order aberrations can cause visual sequelae that leave the individual’s visual goals unsatisfied, and may cause the patient to voice concern, even as the clinician feels an acceptable outcome has been achieved. For instance, the patient may say “I can read the letters, but they are not clear” or a similar statement. This qualitative dissatisfaction can persist, even as the individual reaches what would be considered a satisfactory level of quantitative acuity (20/20). It is important to note that highly aberrated eyes, especially keratoconus, have a decline on vision related quality of life (V-QoL)³. Further, patients with keratoconus may be perceived as being dissatisfied with their clinical experience and that this may influence their perception of their doctor and their illness.³

Wavefront-guided scleral lenses, an emerging translational technology targeting the higher-order aberrations that remain uncorrected during conventional scleral lens wear, have reduced aberration, improved visual image quality and improved resulting visual performance.^1,4,5 As these wavefront-guided scleral lenses become more clinically available, they are providing an additional tool to clinicians when conventional correction modalities have been exhausted and the patient continues to report unsatisfactory perceived visual quality.^1,4,5 Equally important, the introduction of wavefront sensors into the routine examination of these difficult cases will provide insight into the root cause of patient dissatisfaction, which is invisible to the clinician in today’s practice.

This case report focuses on an individual whose subjective visual acuity was 20/20 or better with conventional scleral lenses, yet the individual remained unsatisfied due to perceptual smearing, shadowing, and halos and glare at night in both eyes. When wavefront-guided scleral lenses were fit, the individual’s visual symptoms were reduced to a level where his personal visual goals and expectations were better met. In addition to the successful fitting of the wavefront-guided scleral lens, this case demonstrates the power of wavefront sensing in understanding the visual experience of the patient (through point spread function, retinal image simulation and visual image quality metrics), thus bridging the dissonance between the patient and clinician’s perception of disease burden. The clinical timeline indicating key events relevant to this case presentation, intervention, and resolution is shown is Figure 1.

Figure 1.

Clinical timeline: a 40-year-old male with keratoconus reporting smearing, shadowing and halos and glare at night despite having 20/20 vision in both eyes. Wavefront error was measured and wavefront-guided scleral lenses were fit, which reduced residual higher order aberrations, smearing and shadowing to a level that met his visual goals. OD = right eye; OS = left eye; OU = both eyes; VA = visual acuity; HORMS = higher-order root mean square; WFE = wavefront error; COAS = Complete Ophthalmic Analysis System.

CASE REPORT

A 40-year-old male with bilateral keratoconus (severe disease in the right, moderate disease in the left - disease severity was determined using the CLEK grading system ⁶) enrolled in a research study examining wavefront-guided scleral lenses, which was approved by the Institutional Review Board of the University of Houston and adhered to the Declaration of Helsinki. A written informed consent was obtained for identifiable health information, but no identifiable health information was included in this case report. After completion of conventional scleral lens fitting and refinement of the prescription, Snellen visual acuity was 20/20⁺² in the right eye and 20/16⁺² in the left eye. As displayed in Table 1, the residual higher-order aberrations root mean square wavefront error (through the 10^th Zernike radial order) through the conventional scleral lens measured with a Complete Ophthalmic Analysis System (COAS) HD wavefront sensor (Johnson and Johnson Vision, Santa Ana CA) were poorer than typical ⁷ as was the visual image quality metric measured by the visual Strehl ratio.⁸ Despite reaching 20/20 or better in both eyes, the patient reported halos and glare at night and perceptual smearing, specifically a “Ferris wheel” shadowing in the right eye and a “U” shaped shadowing in the left eye and was unsatisfied with the qualitative visual performance provided by conventional scleral lenses. Because wavefront error was measured through the conventional scleral lenses, these subjective percepts could be objectively corroborated by visualization of the point spread function derived from the measured wavefront error of each eye, and are seen through direct comparison of the patient’s drawn illustration depicting his perception of a point of light (Figure 2). These objective findings are currently invisible in today’s practice, where wavefront sensors are absent, not well understood or under-utilized.

Table 1.

Residual aberrations with conventional scleral lenses (SL) and wavefront-guided scleral lenses (WGSL) are reported in two ways. First, data are reported as higher order root mean square (HORMS) of the 3^rd – 10^th radial orders. Second, residual error is reported by each individual term in the 3^rd-5^th radial orders. Typical data for both HORMS wavefront error and term-by-term are reported for 40-49-year-olds.⁷ Given mirror symmetry⁹ that is exhibited between left and right eyes, left eye data is represented as right eye data.¹⁰ The bottom row of the Table displays the visual image quality metric the visual Strehl calculated using the 2^nd through 10^th radial order for typical eyes where the sphero-cylindrical correction was optimized to create the best visual Strehl values and the measured value for the patient’s two eyes. All aberration values are in μm and that visual Strehl is a unitless ratio.

				OD		OS
	HORMS or Individual Term	Typical Φ=4.00 mm 2SD below mean	Typical Φ=4.00 mm 2SD above mean	SL Residual Aberrations	WGSL Residual aberrations	SL Residual aberrations	WGSL Residual aberrations
HORMS	3rd-10th order	0.045	0.210	0.494	0.195	0.388	0.245
3rd order	6	−0.132	0.058	−0.049	0.007	−0.030	0.044
	7	−0.115	0.094	0.453	0.132	0.302	0.084
	8	−0.117	0.086	0.110	0.019	0.026	−0.011
	9	−0.112	0.118	0.056	−0.037	0.101	0.054
4th order	10	−0.048	0.046	0.022	0.032	−0.042	−0.081
	11	−0.044	0.042	−0.015	0.033	−0.061	−0.027
	12	−0.027	0.107	0.015	0.044	−0.084	−0.102
	13	−0.051	0.038	0.065	0.058	0.117	0.120
	14	−0.042	0.047	−0.022	0.000	−0.040	−0.016
5th order	15	−0.019	0.022	−0.011	−0.019	0.012	0.001
	16	−0.020	0.023	0.046	0.014	0.020	0.011
	17	−0.024	0.023	−0.102	−0.087	−0.090	−0.051
	18	−0.014	0.019	0.013	0.008	0.009	0.006
	19	−0.022	0.019	0.012	0.026	−0.035	−0.028
	20	−0.021	0.022	0.005	0.000	−0.041	−0.053
Visual Strehl		0.268	0.724	0.067	0.150	0.092	0.121

Figure 2.

Optical and visual performance with the conventional scleral lens: Measured higher-order aberrations (A,B), the resultig point spread function (C,D), simulated retinal images (E,F) and the patient’s drawing of his visual precept (G,H).

Following study protocol, ^1,5 the patient was dilated with 1 drop of 1% tropicamide and 1 drop of 2.5% neosynephrine. The conventional scleral lenses were applied and residual wavefront error and lens offsets with respect to the patient’s dilated pupils were measured. Wavefront-guided scleral lenses targeting aberrations in the 2^nd to 5^th Zernike radial orders were manufactured using a DAC 2X-ALM OTT ophthalmic lens lathe (DAC International, Carpinteria, CA) in Boston XO material (Bausch and Lomb, Rochester NY). The wavefront-guided correction was offset from the geometric center of the lens and designed into the wavefront-guided scleral lens such that the correction was coaxial to the center of the dilated pupil. The patient’s Snellen visual acuity improved to 20/10 in the right eye and 20/13 in the left eye. Residual higher-order root mean square wavefront error through the 10^th order was reduced to 0.19 μm (Φ=4.00 mm) in the right eye (which was within 2 standard deviations of age-matched normal limits of 0.21 μm ⁷ ) and 0.25 μm (Φ=4.00 mm) in the left eye and visual image quality as measured by the visual Strehl ratio improved from 0.067 to 0.150 in the right eye and from 0.092 to 0.121 in the left. The mean of typical eyes with sphero-cylinder lenses that optimize the visual Strehl for Φ=4.00 mm for 40 to 50 year old is 0.496 ± 0.228.

Nonetheless, the patient reported that the smearing and shadowing were reduced to a level that met his personal visual goals and night vision was no longer problematic. The reduction in these deleterious effects can be seen directly by comparing the patient’s illustration and the visualization of the point spread function derived from the measured wavefront error when the patient was wearing the conventional scleral lenses (Figure 2) and the wavefront-guided lenses (Figure 3). The comparison of residual wavefront error for both conventional scleral lenses and wavefront-guided scleral lenses on a term-by-term basis and the single value summary metric, the visual Strehl ratio, as well as mean and ±2 standard deviations for typical eyes can be seen in Table 1.

Figure 3.

Optical and visual performance with the wavefront-guided scleral lens: Measured higher-order aberrations (A,B), the resulting point spread function (C,D), simulated retinal images (E,F) and the patient’s drawing of his visual precept (G,H).

DISCUSSION

The application of wavefront technology has been studied at length in the literature and has created a paradigm shift in refractive surgery, cataract surgery, and wavefront-based refractive correction and can improve the visual quality of individuals.^8,11–13 Wavefront-guided corrections in contact lenses is in its clinical infancy and has proven itself beneficial, particularly for individuals with elevated higher-order aberrations. However, these highly personalized wavefront-guided lenses are yet to be widely available to these individuals. This continues to be the clinical reality, even as the ability to detect the disease earlier in the disease process increases and estimates as to the true prevalence of diseases such as keratoconus shift. One recent study places the prevalence of keratoconus at roughly 5 times higher (1 in 375) than the commonly accepted prevalence rate (1 in 2000).¹⁴

Wavefront-guided corrections work by directly targeting the root cause of continued patient dissatisfaction – residual, uncorrected higher-order aberration that is inevitable with conventional corrections, particularly for the highly aberrated eye. In the clinical absence of wavefront sensors, the residual higher-order aberrations remaining during conventional scleral lens wear and their impact on visual image quality are invisible to the clinician despite improvement in acuity. The residual total eye aberrations that continue to degrade vision while wearing a correction are not quantified with the phoropter during the subjective refraction, by topography or any other common clinical tool.

Further, high contrast visual acuity is a recognition task: can the letter be correctly identified or not? As such, it does not reflect the quality of the letter, only whether the letter can be correctly identified. The patient’s expressed desire to have better vision is well founded in the literature. Ravikumar et al. demonstrated that there are 6 noticeable changes in visual image quality prior to a line of lost logMAR acuity. This means that patients can see changes in visual image quality well before a measurable loss of acuity.¹⁵ This case demonstrates such a failure of the current clinical standard. A patient with keratoconus achieving 20/20 high contrast visual acuity in both eyes, by current clinical standards, would be considered a resounding success. Importantly, the disease remained a significant burden from the patient’s perspective. Visual acuity and subjective over refraction did not provide evidence to support the patient’s concern, creating dissonance between the patient and clinician’s perception of the disease burden.³

While scleral lenses, a clinical standard, failed to provide the visual quality that met the patient’s visual goals, wavefront sensing and subsequent wavefront-guided lenses succeeded. The application of wavefront sensing is powerfully demonstrated in this case report in two ways. First, wavefront sensing allows the clinician to identify and quantify the source of continued dissatisfaction and allows for visualization (Figures 2 and 3) of the impact of these residual aberrations, which corroborated the patient’s experience. In doing so, the dissonance between this patient’s perception of his disease burden and the clinician’s perception of that burden was bridged. Secondly, the measured aberrations and reduction in the visual image quality called for a solution. By specifically targeting residual higher-order aberrations with the wavefront-guided scleral lenses, visual symptoms such as smearing, and ghosting were diminished, leading to an improvement in the individual’s perceived visual quality.

To put this case in a broader context, it is important to note that the total eye aberrations were not reduced to zero (Table 1) which would have made the visual quality metric a perfect 1; this would be an essentially impossible goal. Instead, the goal is to minimize residual aberrations and their interactions improving visual image quality to meet the visual needs of the patient. While the future is bright for meeting the unmet visual needs of the highly aberrated patient, continuing education on wavefront-guided corrections and its strengths and limitations is essential in utilizing WGSLs to meet the visual needs of the “20/20 unhappy” patients when traditional clinical options are exhausted.