One current controversy revolves around whether scleral lens wear affects intraocular pressure (IOP). Research has produced conflicting results, which may be due to differences in study design. There are two commonly cited theories for IOP increase with scleral lens wear: 1) the weight of the lens compresses the episcleral veins or Schlemm’s canal, resulting in reduced aqueous outflow; and 2) the suction or negative pressure generated when the lens is worn elevates the IOP, particularly if the lens is fit too tightly.
| AUTHORS / YEAR | SUBJECTS | IOP MEASUREMENT TECHNIQUE | METHOD | RESULTS |
|---|---|---|---|---|
| Nau et al 2015 | N = 29 Healthy | Pneumatonometry | 1) Baseline central IOP with lens off 2) Peripheral bulbar conjunctival IOP with lens on at < 5 minutes, 1 hour, 2 hours |
No significant IOP increase with scleral lens on, or immediately after, removal compared to baseline |
| Michaud et al 2018 | N = 21 Healthy | 1) Goldmann 2) Transpalpebral |
1) Baseline diurnal Goldmann IOP with lens off 2) Transpalpebral IOP with lens on (15.8mm or 18.0mm diameter) |
Average IOP increase of 5 mmHg for both small- and large-diameter lenses |
| Shahnazi et al 2019 | N = 25 Ocular Surface Disease | Tonopen | 1) Baseline central IOP prior to lens application 2) Central IOP immediately after lens removal |
No significant IOP change after lens removal regardless of wear time (range one to 6+ hours) |
| Cheung et al 2020 | N = 50 Healthy | Rebound tonometry | 1) Baseline central IOP prior to lens application 2) Central IOP through fenestration in lens without fluid immediately following application 3) Central IOP immediately after lens removal |
Average IOP increase of < 4 mmHg with lens on, and IOP levels returned close to pre-lens wear IOP immediately after lens removal |
| Kramer and Vincent 2020 | N = 17 Ectasia, post-radial keratotomy, post-penetrating keratoplasty, high ametropia | Goldmann | 1) Baseline central IOP before lens fitting using scleral profilometry 2) Central IOP after lens removal at 1- and 6-month follow ups |
No significant IOP change after lens removal for both 1- and 6-month follow ups |
Clinical Implications
Studies measuring IOP after scleral lens removal show relatively good agreement that pressure is not significantly changed from baseline. Of the studies measuring IOP with a lens on, two showed an average increase of ~4 mmHg to 5 mmHg (Cheung et al, 2020; Michaud et al, 2019), whereas one showed no significant increase (Nau et al, 2016).
These and other studies utilized different tonometry techniques, and there are varying reports about the comparability of pneumatonometry and transpalpebral tonometry with Goldmann (Chakraborty et al, 2014; Duke et al, 2012; Sandner et al, 2003). Cheung (2020) used rebound tonometry, which has relatively good agreement with Goldmann; however, the fenestrated scleral effectively reduced the suction force. The fact that an increase in IOP was still found may indicate that tissue compression or changes in biomechanical properties of the cornea and/or sclera are the main contributors to IOP change.
Without consistent findings to guide our clinical decision making, should we be concerned about IOP elevation in our scleral patients? This becomes particularly concerning in glaucoma patients or glaucoma suspects. We must also consider patients who may require sclerals to function, such as those who have keratoconus, as thinner corneas with lower hysteresis complicate our interpretation of IOP measurements. In these situations, determine whether the benefits of scleral lens wear outweigh the risks and consider more frequent glaucoma testing to monitor for changes over time. CLS
For references, please visit www.clspectrum.com/references and click on document #298.
![]({"src":"/media/pjzmazs2/cover_cls_0920.jpg","focalPoint":null,"crops":[{"alias":"thumbnail","width":1110,"height":700,"coordinates":null}]})