Scleral lens fogging is a common complaint, but “fogging” is not necessarily 1 phenomenon. Clinically, it is important to distinguish between debris or deposits on the anterior lens surface and particulate accumulation within the post-lens tear reservoir. Although both can cause reduced vision and a hazy appearance, their causes—and solutions—are quite different.
Anterior-Surface Fogging
Surface fogging, as the name suggests, occurs on the front surface of the scleral lens. The most obvious clinical observation is a hazy lens surface that may improve temporarily with blinking or instillation of an artificial tear.
One common contributor is an unstable or compromised pre-lens tear film. Meibomian gland dysfunction, aqueous deficiency, and mucin abnormalities can all contribute to rapid tear film breakup and debris accumulation on the lens surface. Cosmetics, environmental contaminants, and certain artificial tears can also contribute to deposits.
Immediately improving vision often requires removing the lens and cleaning or rinsing the front surface. It also may be beneficial to use the “atypical” end of the application plunger as a squeegee. Many times, a drop of multipurpose contact lens solution on the back of the application plunger can, at least temporarily, allow for improved vision.
Management should, therefore, focus on the ocular surface and the anterior lens environment. Optimizing meibomian gland function, treating inflammation, modifying the patient’s tear supplementation, and improving lens cleaning and surface wettability may all help. In some cases, changing the lens material or surface treatment is also beneficial.
Post-Lens Tear Reservoir Fogging
Perhaps more common is post-lens tear reservoir fogging that occurs behind the scleral lens, within the fluid reservoir between the posterior lens surface and the cornea (Figure 1). Clinically, this is a different problem and requires a different plan of attack.
The hallmark is particulates, cellular debris, or lipids and other inflammatory material that are suspended in the reservoir. Rather than simply sitting on the front of the lens, the opacity appears to move with the fluid behind the lens. The patient may report progressively decreasing vision or a “cloudy” view that does not resolve with blinking.
Lens fit can play an important role. Excessive clearance, inadequate limbal sealing, or localized areas of excessive movement may permit greater exchange between the reservoir and the surrounding tear film. Therefore, post-lens tear reservoir fogging requires that the lens-to-globe fitting relationship be revisited to improve haptic alignment and minimize unwanted fluid exchange. In some patients, removing and reinserting the lens with fresh preservative-free saline provides dramatic improvement.
Why the Distinction Matters
The 2 forms of fogging can look deceptively similar, but they point the clinician toward different treatment strategies. If the problem is on the front surface, treat the tear film and lens surface. If it is behind the lens, evaluate the fit and post-lens environment.
Can this process be frustrating, especially when patients have both complaints? Of course! However, if you can ascertain where the fogging is occurring, provide detailed lens-to-globe measurements to lab consultants, and have a working knowledge of rigid lens materials, you are much more likely to be successful in fitting these lenses. OM
