The Effect of a Scleral Lens on the Anterior Chamber Depth and Minimum Rim Width
Condition: Ocular Hypertension
MeSH terms: Ocular Hypertension
Study type: Interventional

Summary: 
      The purpose of this study is to evaluate the use of two instruments to measure changes in two
      ocular structures: 1) the anterior chamber depth (ACD) - measured using low coherence optical
      biometry, and 2) minimum rim width of the optic nerve head (MRW) - measured using optical
      coherence tomography. Changes in these ocular structures indicate fluctuations in intraocular
      pressure (IOP) and will be measured during scleral contact lens (SGP) wear to determine if
      SGP wear influences IOP. We hypothesize that a scleral lens increases the intraocular
      pressure (IOP) during active wear and that the ACD and MRW will also change.
    

Detailed description: 
      Contact lenses are often used to correct vision blur. The most common types of contact lenses
      include those referred to as 'soft' and 'rigid'. Visual acuity through rigid lenses often
      surpasses that of soft lenses. Historically, these lenses have been small in diameter, and
      hence patients also felt discomfort when wearing the lenses. Scleral lenses are relatively
      new, customized devices that have gained popularity with patients and practitioners in the
      past 5-10 years, because they are more comfortable and provide more stable vision than the
      small diameter rigid contact lenses. However, relatively little is known about the
      physiologic response of the eye to the scleral lens, or the long-term effects of their use,
      since they are such a new modality.

      Maintaining the IOP within the eye is imperative to prevent damage to ocular tissue, which
      can occur in glaucoma. Given the landing of scleral lens overlying the sclera and ciliary
      body, which assist in modulating the transport of fluid in the eye, there is a potential for
      these lenses to impinge on fluid drainage which could lead to increases of IOP during scleral
      lens wear. The placement of the lens creates an obstacle in evaluating IOP while the lens is
      actually on the eye (covering the cornea), and since increases in IOP may only occur during
      lens wear, which is removed when determining clinical IOP measurements, it is difficult to
      monitor IOP during scleral lens wear with traditional IOP instrumentation (ie. iCare,
      Goldman, etc).

      Optical coherence tomography is a non-invasive imaging technology that has revolutionized how
      the retina and optic nerve are clinically evaluated. The optic nerve head is typically
      assessed using radial scans, from which the minimal distance from the Bruch's membrane
      opening to the inner limiting lamina is quantified as the minimum rim width (MRW). With
      changes in IOP, the MRW is known to also change in thickness. Many studies are investigating
      the MRW changes during IOP fluctuations, with studies finding a decrease in MRW during acute
      IOP increase. In this project, MRW will be used to indirectly assess changes in IOP by
      measuring the MRW periodically during active scleral lens wear.

      In addition, we are incorporating low coherence optical biometry (Lenstar) to evaluate the
      effect of the scleral lens pressure on the anterior chamber. Using the Lenstar, corneal
      thickness, anterior chamber depth (ACD), lens thickness and vitreous chamber depth can be
      quantified. In this project, ACD will be used to indirectly evaluate changes in the pressure
      within the anterior chamber. The assumption is that the ACD will change based on changes in
      pressure in the scleral lens tear reservoir.

      This study will add to the knowledge of how the scleral lens affects the dynamic pressure
      system of the eye. Based on the implications for disease with chronic increases and
      fluctuations in IOP, this is important information to understand with the scleral lens, a
      relatively new refractive treatment modality.
    

Intervention name(s): Scleral Lens; No lens
Intervention type(s): Device; Other
Intervention description(s): The contact lens will be worn on one eye.; No lens worn on the contralateral control eye
Allocation: Randomized
Intervention model: Single Group Assignment
Intervention model description: Subjects are all non-scleral lens wearers. One eye (test) will be selected to wear a scleral lens, and the contralateral eye (control) will not wear any lens.
Masking: None (Open Label)
Primary purpose: Basic Science