Soft Lens Fitting

from Research to Practice

Mari Fujimoto & Matthew Lampa

With soft contact lens (SCL) design, the two factors that can greatly contribute to the lens-to-ocular surface relationship are the lens base curve and the diameter. Together, the base curve and diameter are directly linked to the sagittal depth of a soft contact lens. Adjusting the sagittal depth may improve centration and on-eye performance of a soft contact lens.

The contemporary, widely manufactured hydrogel and silicone hydrogel lens designs are optimized for comfort and to match the corneal and scleral shape of the average eye. We have all seen patients with end-of-day discomfort or who are wearing soft lenses that exhibit inadequate coverage past the limbus. Patients who believe that they are not able to wear contact lenses also present in our exam chairs. Two questions often cross our minds: 1) How can we optimize our chair time and effectively select soft contact lens options for these individuals? And 2) How do we efficiently determine whether patients require a custom soft contact lens to best fit their ocular surface?

In a recent publication in Contact Lens and Anterior Eye, van der Worp et al. reported the sagittal depths of a series of modern commercially available soft contact lenses. The sagittal depth charts have provided some insight into answering these questions and have helped guide our clinical decision-making. To demonstrate how we apply the sagittal depth charts to clinical practice, we present the case report below.

The patient in Figure 1 is a 23-year-old optometry student who has struggled with soft contact lens comfort and reports that his eyes are irritated after a few hours of lens wear. The patient was interested in wearing daily disposable lenses, if possible. Figure 1A reveals a shallow-fitting lens on the patient’s eye, with inadequate limbal coverage and superior-temporal decentration of the lens on eye. To improve the contact lens fit, the patient requires a deeper lens with a higher sagittal depth. To observe a change in the SCL fit, we predict that the contact lens sagittal depth requires an adjustment of approximately 250 microns. The lens in Figure 1B is 232 microns deeper than the lens in 1A, resulting in a slight improvement in lens centration but still inadequate coverage of the SCL past the limbus. Yet again, we need to apply a lens that has a greater sagittal depth, in this case greater than 3700 microns (sagittal depth of lens 1B). Although the ideal next lens would have a sagittal depth of approximately 3950 microns, lens 1C was the deepest spherical daily disposable lens available at the time of the CL fitting (212 microns deeper than lens 1B). Figure 1C shows adequate centration, lens movement, and approximately 1mm of limbal coverage. The patient reported that lens 1C was the most comfortable spherical daily disposable trialed. The patient’s spectacle prescription is -3.00 -0.75 x 180, but he has habitually worn the spherical equivalent CL Rx of -3.25DS. Low-cylinder lenses can sometimes offer an advantage in fitting individuals similar to our patient, as the toric lens counterparts often have a larger lens diameter and therefore a higher sagittal depth. Figure 1D shows a toric lens that is 241 microns deeper than lens 1C. Although the fit seems relatively similar to 1C, the patient reported improved comfort and appreciated the vision with the astigmatism-correcting optics. The patient determined that lens 1D provided acceptable comfort, but he was interested in pursuing other SCL options due to continued lens awareness.

Figure 1. The soft contact lenses have been dyed with lissamine green for imaging visibility only. (A) Acuvue Moist 9.0 / 14.2, sagittal depth 3468µm (B) Biotrue OneDay 8.6 / 14.2, sagittal depth 3700µm (C) Dailies Total1 (8.5 / 14.2, sagittal depth 3912µm) (D) Biotrue OneDay for Astigmatism (8.4 / 14.5, sagittal depth 4153µm).

Figure 2. Daily disposable lens sagittal depth chart with the addition of the Biotrue OneDay for Astigmatism. The arrows and labels represent the lenses of Figure 1A, 1B, 1C, and 1D. (Chart adapted from van der Worp, et al.).

The sagittal depth charts (Figure 2) can help guide clinicians in selecting the next best lens option to trial on eye. Another aspect to appreciate is that if the deepest lens with the highest sagittal depth does not offer an appropriate fit, this can help confirm that a custom soft contact lens is the next best option for soft contact lens fitting success. After receiving his custom soft contact lenses, this patient reported a significant improvement in lens comfort after a few hours of wear compared to any previously worn lenses. From a clinical perspective, the custom SCL provided a more optimal lens fit (Figure 3).

Figure 3. Custom SCL fit with a lens diameter of 15.0mm compared to (1D) Biotrue OneDay for Astigmatism (8.4 / 14.5, sagittal depth 4153). The patient reported the best comfort with the custom soft contact lens (right image).


A wide range of factors may contribute to the sagittal depth and the fitting properties of a soft contact lens. The lens modulus and lens hydration are two significant factors that may affect the sagittal depth of the contact lens on-eye. When a lens has a higher modulus, i.e., is made of a stiffer material, the lens fit may need to be more precise when compared to the fit with a low-modulus lens material. This may mean that you need a more significant change in the sagittal depth than 250 microns if you are switching from a lower-modulus lens to a higher-modulus lens. Additionally, lens hydration plays a role in that the moment you place a contact lens on the eye is the flattest fit that the lens will have. As the lens loses water and equilibrates to the ocular surface, the soft lens base curve steepens and the diameter decreases. Considering the tightening of the lens fit due to dehydration, selecting lenses of a shallower sagittal depth for patients who experience end-of-day discomfort may relieve symptoms of fatigue or discomfort at the end of the day.

The sagittal depth charts have expanded our understanding of soft contact lenses and have provided guidance in clinical decision making. As we continue to study the various lens designs, we hope to utilize the sagittal depth chart to decrease the rate of soft contact lens dropout


1. Van der Worp E, Lampa M, Kinoshita B, et al. Variation in sag values in daily disposable, reusable and toric soft contact lenses. Contact Lens and Anterior Eye. 2021 Online ahead of print.

2. Tranoudis I, Efron N. Parameter stability of soft contact lenses made from different materials. Contact Lens and Anterior Eye. 2004. 27(3):115-31.