Is the Use of Empirically Designed Custom Soft Contact Lenses a Good Option for Challenging Patients?

doi:10.4236/ojoph.2013.33014

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Open Journal of Ophthalmology, 2013, 3, 54-60

http://dx.doi.org/10.4236/ojoph.2013.33014 Published Online August 2013 (http://www.scirp.org/journal/ojoph)

Is the Use of Empirically Designed Custom Soft Contact

Lenses a Good Option for Challenging Patients?

Frank Spors1*, Donald J. Egan1, Lance E. McNaughton1, Jie Shen1, Matthew J. Lampa2

1Western University of Health Sciences, College of Optometry, Pomona, USA; 2Pacific University, College of Optometry, Forest

Grove, USA.

Email: *[email protected]

Received April 28th, 2013; revised May 29th, 2013; accepted June 15th, 2013

which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

ABSTRACT

Purpose: Reasons for the lack of success for contact lens patients range from poor fit, to discomfort or to a less than

optimum wearing schedule. This project was a preliminary investigation of customized soft toric contact lenses as an

alternative for unsuccessful contact lens patients or potential drop-outs. Methods: Fifteen healthy non-compromised,

previously unsuccessful contact lens wearing patients (13 women, 2 men) with ages from 21 to 33 years (25.1 ± 2.7

years) were the subjects for this study. They were empirically fitted with 15 astigmatic and 5 spherical customized Spe-

cialEyes soft contact lenses. Visual acuities, comfort, lens movement, and rotation were evaluated. Results: Patients

fitted with customized SpecialEyes soft contact lenses had statistically significant better visual acuities than with

Phoropter Manifest Refraction. The lenses used in this study centered well and moved no more than 1 mm upon each

blink. Lens rotation was less than 10 degrees for all toric lenses. Patients gave very positive vision and comfort ratings.

Conclusion: This preliminary study supports the application of a software program to empirically design and manufac-

ture SpecialEyes custom soft lenses based upon co rneal topographical parameters and subjective manifest refraction for

those patients who either have challenging corneal parameters, high sphero-cylindrical prescriptions, or are currently

dissatisfied with their contact lenses and are potential drop-outs.

Keywords: Soft Contact Lenses; Custom Contact Lenses; Toric Contact Lenses; Contact Lenses for Astigmatism;

Empirical Contact Lens Fitting

1. Introduction

The goal of soft contact lens application is to combine

excellent vision with overall lens comfort. In recent years

the introduction of improved materials has led to an in-

crease in the popularity of soft lenses, especially since

frequent replacement options reduce the risk of microbial

infections and the presence of lens deposits. As some-

what of a disadvantage however most frequent replace-

ment lenses are only available in a narrow range of pa-

rameters. Indeed most lenses are available in just one

diameter, one or two base curves, and in the case of as-

tigmatic designs limited cylinder power and range of axis

values exists. Although these limitations result in a sim-

plified approach to lens selection, it may not be the best

way of successfully prescribing contact lenses for pa-

tients who do not have average corneal shape values,

refractive data, or visual demands.

Up to 45% of the contact lens seeking population have

astigmatism of 0.75 D or greater [1]. However, toric soft

contact lenses remain generally underutilized as a co rrec-

tive strategy. A variety of soft toric contact lenses have

been widely available for some years, but many practi-

tioners are reluctant to incorporate them into their fitting

routines or recommend them to wearers. This is partly

due to a history of unpredictable lens orientation and

difficulty in achieving a stable fit [1]. According to the

International Survey of Contact Lens Prescribing, only

19% of prescribed daily wear soft contact lenses are toric

in design [2].

The reasons for discontinuing contact lenses have been

evaluated in a number of studies [3,4]. The most com-

monly cited reason in all of these studies is discomfort,

which accounts for between 43% and 72% of the drop-

outs. Poor vision is another important factor which is due

in part to product non-availability for high prescriptions,

and practitioner misjudgment. Prime reasons for practi-

*Corresponding a uthor.

Is the Use of Empirically Designed Custom Soft Contact Lenses a Good Option for Challenging Patients? 55

tioner misjudgment are inappropriate lens fit and uncor-

rected astigmatism [5].

Lens reproducibility is regarded as another very im-

portant factor in the success of toric soft contact lenses,

and poor reproducibility of frequent replacement lenses

has been implicated in the underutilization of these len-

ses [6].

Selection of an initial soft contact lens base curve has

traditionally been based on central corneal curvature, as

measured by keratometry. The underlying assumption

behind this is that co rneas with steeper central radii have

greater sagittal height and, therefore, require a lens of

greater sagittal depth in the form of a steeper base curve

to optimally fit the cornea. However, previous studies

have shown that there is no strong correlation between

keratometry readings and the best-fitting soft con tact lens

[7]. Accordingly soft toric contact lens fitting, when

based on manifest refraction and keratometry alone, of-

ten presents unanticipated fitting and power errors upon

initial lens dispensing [8].

Following the standard procedure of keratometry, em-

pirical fitting success with soft toric contact lenses can be

anticipated in spherical corneas, central astigmatism, or

corneas with peripheral toricity matched with central

toricity. Considering that high and irregular peripheral

corneal toricity occurs in the majority of astigmatic pa-

tients, including empirical soft contact lens fitting based

upon more corneal topographical parameters, sagittal

height, and corneal diameter, may lead to increased fit-

ting success, better visual acuity, and fewer drop-outs

[8-10]. Incorporation of all of these parameters requires

customized soft contact lenses with varying base curves,

diameters, sagittal heights, and power values [11,12].

The purpose of this project was to evaluate Spe-

cialEyes customized soft toric contact lenses as an alter-

native for unsuccessful contact lens patients or potential

drop-outs.

2. Methods

2.1. Subjects and Inclusion Criteria

Fifteen healthy, non-compromised, previously unsuc-

cessful contact lens wearing patients (13 women, 2 men)

with ages ranging from 21 - 33 years (25.1 ± 2.7 years)

were the subjects for this stud y. The reasons for previous

drop-outs were unsatisfactory visual acuity and/or re-

duced comfort with conventional and disposable soft

contact lenses. Refractive errors were not limited, but fell

within the range of −8.00 D to + 3.75 D sphere, and up to

−3.75 D of spectacle cylinder. Expressed in rectangular

Fourier optics terms, the mean spherical equivalent was

M = −4.36 D (SD 2.66 D), and the astigmatic vector

components were J0 = 0.09 D (SD 0.74 D), and J45 =

0.04 D (SD 0.62 D). None of the participants suffered

from any eye disease or injury, nor were they taking any

medication or supplements. This research followed the

tenets of the Declaration of Helsinki, and informed con-

sent was obtained from all participants. All measure-

ments were conducted at the Health Education Center at

Western University of Health Sciences, College of Op-

tometry.

2.2. Measurements and Fitting Modalities

Corneal topography data were obtained using the Med-

mont E 300™ Corneal Topography System (Medmont

Pty Ltd, Nudawading, VIC, Australia). Data of interest

included tangential curvature, elevation topographical

maps, simulated keratometry values, and corneal diame-

ters, as depicted in Figure 1. In addition, the patients’

maximum plus manifest non-cycloplegic Phoropter-

refractions were measured to determine lens power val-

ues. Each patient’s best corrected high contrast visual

acuities were obtained using ETDRS letters provided by

the M&S Smart System (M&S Technologies, Inc., Niles,

IL, USA) and recorded in logarithmically-stepped Snel-

len foot notation. The examination room illumination

was 100 lu x.

Thirty eyes were fitted with custom hydrogel contact

lenses, empirically designed and manufactured by Spe-

cialEyes (Bradenton, FL, USA) based upon the submitted

topographical and refractive data.

All contact lenses were initially evaluated and subse-

quently followed -up to determine if this approach in lens

design represents a successful alternative to generic lens

designs which account for the standard office stock

available and dispensed by most eye care practitioners.

Corneal anatomical features and refraction data deter-

mined the lens parameters designed by SpecialEyes’ pro-

prietary software. From the available data the following

contact lens parameters were calculated:

• Diameter

• Base curve

• Sagittal height

• Power

2.3. Contact Lenses and Lens Material

All lenses were used as daily wear lenses. Each lens was

a customized lathe-cut design manufactured by Spe-

cialEyes from the p-GMA/HEMA hioxifilcon D material

with a water content of 54%, and a Dk value of 23 × 10−11

(cm/sec)(mL02/mL/mm Hg). All lenses were designed

for a three month replacement modality. Table 1 lists the

range of contact lens parameters used in this study.

Twenty-five lenses were astigmatic, and five lenses

were spherical. All patients were fit with at least one as-

tigmatic lens. Eighteen eyes had with-the-rule astigma-

tism, three eyes had against-the-rule astigmatism, and

Is the Use of Empirically Designed Custom Soft Contact Lenses a Good Option for Challenging Patients?

Figure 1. Corneal topographical maps: (a) Tangential curvature; (b) Elevation.

Table 1. Range of SpecialEyes contact lens parameters used in this study.

Parameter Range Mean SD

Base curve 7.70 mm - 9.00 mm 8.42 mm 0.40 mm

Diameter 13.80 mm - 15.20 mm 14.54 mm 0.39 mm

Sphere power −8.00 D - +3.75 D −3.69 D 2.51 D

Cylinder power −3.25 D - −0.50 D −1.47 D 0.81 D

Central thickness 99.43 µm - 284.66 µm 120.49 µm 38.91 µm

Sagittal height 3129.87 µm - 4470.68 µm 3784.10 µm 278.73 µm

four eyes had oblique astigmatism.

SpecialEyes employs a prism ballast stabilization de-

sign for back surface toric lenses, which is depicted in

Figure 2. In general, this design is associated with a

higher visual acuity when compared to alternative stabi-

lization mechanisms [13]. To assure optimum optical

quality each of the manufactured lenses was evaluated-

prior to delivery with a Nimo TR1504 contact lens power

mapper and wavefront analyzer (Lambda-X S.A., Niv-

elles, Belgium) via the Phase-Shifting Schlieren trans-

mission method. Sample images of these measurements

are displayed in Figu re 3.

2.4. Fitting Evaluation

Lenses were allowed to settle for fifteen minutes, fol-

lowed by evaluation of centration, movement, and in the

case of astigmatic lenses, lens rotation. Fitting was

evaluated with a Haag Streit BQ 900 slit lamp utilizing

the IM 900 digital imaging system and EyeCap Version

6.2.0 software (Haag Streit AG, K oeni z, Switzerland ).

In observance of Snyder’s Rule the maximum rotation

permitted for a successful fit was no more than ten de-

grees [14]. High contrast visual acuity was measured

under the initial conditions, and all patients rated vision

and comfort with their lenses on a scale from 1 (not sat-

isfied) to 5 (excellent).

Fitting success was determined as indicated by the fol-

lowing parameters:

• Visual Acuity: with SpecialEyes contact lenses equal

to or better than Phoropter Ma nifest Refraction.

• Subjective Vision Rating: at least 4 (very satisfied) for

the majorit y of l enses, and no value of 1 (not satis fied)

for any lens.

• Subjective Comfort Rating: at least 4 (very satisfied)

for the majority of lenses, and no value of 1 (not sat-

isfied) for any lens.

• Lens Rotation: less than 10 degrees for astigmatic

lenses.

• Lens Decentration: between 0.1 mm and 1.0 mm post-

blink movement, and in ter-blink stability.

2.5. Statistical Analysis

A Wilcoxon matched-pairs signed rank test was con-

ducted for thirty eyes with Prism6 (GraphPad Software

Inc., La Jolla, USA) after not passing the Kolmogorov-

Smirnov normality test with Dallal and Wilkinson ap-

Is the Use of Empirically Designed Custom Soft Contact Lenses a Good Option for Challenging Patients? 57

Figure 2. SpecialEyes toric soft contact lens, prism ballast stabilization example: (a) Front view showing markings, toric optic

zone, and prism distribution; (b) Cross-sec t io nal view illustrating prism distribution.

Figure 3. Nimo TR 1504 images of a SpecialEyes soft toric contact lens: (a) Phase-shifting Schlieren image; (b) Wavefront

analysis of the central 6 mm optical zone of the same lens, (Images courtesy SpecialEyes).

proximation to Lilliefors’ method (P < 0.0001) [15].

The mean visual acuity values achieved with the

Phoropter Manifest Refraction and with the SpecialEyes

lenses were compared. For statistical purposes, a P value

lower than 0.05 was considered statistically significant.

3. Results

The analysis of mean visual acuity displayed in Figure 4

and Table 2 illustrates that patients fit with customized

SpecialEyes soft contact lenses had a statistically signifi-

cant better visual acuities than with Phoropter Manifest

Refraction. All p atients evaluated the contact lenses with

regards to vision and comfort and ga ve rat ings of at least 4

(very satisfied) for the majority of lenses, whereas no one

reported a val ue o f 1 (not satisfied) for any lens, as shown

in Figure 5. Judgments of lens and axis rotation as well as

movem ent upon blink a re depicted i n Figure 6. The lenses

used in thi s s tudy cente red we ll and mo ved s m oothl y over

the patients’ corneas and conjunctivas. Figure 7 shows

two representative slit lamp biomicroscopy images.

4. Discussion

The results of this preliminary study support the ap plica-

tion of a software program to empirically design and

Is the Use of Empirically Designed Custom Soft Contact Lenses a Good Option for Challenging Patients?

Figure 4. Visual acuities achieved with Phoropter Manifest Refraction and SpecialEyes lenses.

Table 2. Statistical analysis of differences in visual acuities achieved with Phoropter Manifest Refraction versus SpecialEyes

lenses.

Wilcoxon matched-pairs signed rank test

Treatment modality Phoropter Manifest Rx SpecialEyes

Number of values 30 30

Mean 0.9623 1.045

Std. Deviation 0.1632 0.1255

Std. Error of M ea n 0.02980 0.02291

Lower 95% CI of mean 0.9014 0.9981

Upper 95% CI of mean 1.023 1.092

P value 0.0208

Significantly different ? (P < 0. 05) Yes

One- or two-tailed P value? Two-tailed

Sum of positive, negative ranks 88.50, −16.50

Sum of signed ranks (W) 72.00

Figure 5. Subjective r atings for SpecialEyes soft contact lenses: (a) Vision; (b) Comfort.

Is the Use of Empirically Designed Custom Soft Contact Lenses a Good Option for Challenging Patients? 59

Figure 6. SpecialEyes lenses observed by biomicroscopy: (a) Rotation; (b) Movement.

Figure 7. Biomicroscopy images of SpecialEyes custom soft lenses: (a) Spherical lens; (b) Astigmatic lens.

manufacture SpecialEyes custom soft lenses based upon

corneal topographical parameters and subjective manifest

refraction data for those patients who either have chal-

lenging corneal parameters, high sphero-cylindrical pre-

scriptions, or are currently dissatisfied with their contact

lenses and are potential drop-outs. Customized lens pa-

rameters, a robust stabilization mechanism for astigmatic

lenses, a comfortable hydrophilic material, in vivo pa-

rameter stability, and high reproducibility are shown here

to be important elements for successful fitting soft con-

tact lenses in challenging patients.

Lenses made from the hioxifilcon material family, as

used in this study, are known to remain saturated and

dimensionally stable on the eye resulting in excellent

visual acuity, comfort, as well as alleviation of sympto ms

and ocular surface staining associated with contact lens

related dryne ss [16].

The patients in our study reported good comfort and

vision with customized SpecialEyes soft contact lenses.

With these lenses the patients achieved statistically sig-

nificant improvements in visual acuities when compared

with Phoropter Manifest Refraction, although this dif-

ference was not clinically significant, since the visual

acuity improved less than one line. Possible explanations

for the increase in visual acuity with lenses when com-

pared to the best corrected manifest phoropter refraction

may be larger retinal image sizes in myopic patients, and

the reduction of some corneal higher order aberrations,

Is the Use of Empirically Designed Custom Soft Contact Lenses a Good Option for Challenging Patients?

e.g. coma, due to the thickness of the hioxifilcon D con-

tact lens material [13,17].

5. Conclusions

The results of this study suggest that empirically de-

signed custom fit soft contact lenses:

• Fit most refractive parameter combinations and cor-

neal profiles;

• Allow fast and easy correction of high astigmatic re-

fractive errors;

• Provide good patient comfort;

• Reduce chair-time;

• Increase the first pair fit success rate.

The virtually unlimited range of parameters with these

lenses assures availability of the optimal lens for each

patient’s condition, and may have a positive impact on

patient compliance and loyalty. A rigorous cleaning and

disinfecting regimen in combination with planned lens

replacement is necessary to maintain optical quality as

well as hydrophilicity, and to decrease the accumulation

of long term deposits on the contact lens material. It ap-

pears that a 3-month replacement cycle is appropriate for

these lathe-cut manufactured custom soft lenses.

Additional research with a larger sample of normal as

well as compromised corneas, different lens types and

materials is planned for future studies.

6. Acknowledgements

We thank SpecialEyes, especially Ms. Lindsay McCorkle,

for empirically designing and providing the customized

contact lenses used in this study.

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