RGP lenses provide a good level of visual correction, but do not arrest progression of the condition.In people with keratoconus, rigid contact lenses improve vision by means of tear fluid filling the gap between the irregular corneal surface and the smooth regular inner surface of the lens, thereby creating the effect of a smoother cornea. Many specialized types of contact lenses have been developed for keratoconus, and affected people may seek out both doctors specialized in conditions of the cornea, and contact lens fitters who have experience managing people with keratoconus. The irregular cone presents a challenge and the fitter will endeavor to produce a lens with the optimal contact, stability and steepness. Some trial-and-error fitting may prove necessary. Hybrid lenses
Traditionally, contact lenses for keratoconus have been the hard or RGP variety, although manufacturers have also produced specialized soft or hydrophilic lenses and, most recently, silicone hydrogel lenses. A soft lens has a tendency to conform to the conical shape of the cornea, thus diminishing its effect. To counter this, hybrid lenses have been developed that are hard in the centre and encompassed by a soft skirt. However, soft or earlier generation hybrid lenses did not prove effective for every person. Early generation lenses have been discontinued. The fourth generation of hybrid lens technology has improved, giving more people an option that combines the comfort of a soft lens with the visual acuity of an RGP lens.
The nerve is particularly vulnerable to injury when there has been a disruption in the normal anatomy. The most common site of ulnar nerve entrapment is at the elbow, followed by the wrist.Causes or structures which have been reported to cause ulnar nerve entrapment include:
Problems originating at the neck: thoracic outlet syndrome, cervical spine pathology, compression by anterior scalene muscles
Problems originating in the chest: compression by pectoralis minor muscles
Brachial plexus abnormalities
Elbow: fractures, growth plate injuries, cubital tunnel syndrome, flexorpronator aponeurosis, arcade of Struthers
Forearm: tight flexor carpi ulnaris muscles
Wrist: fractures, ulnar tunnel syndrome, hypothenar hammer syndrome
Artery aneurysms or thrombosis
Other: Infections, tumors, diabetes, hypothyroidism, rheumatism, and alcoholism

Cubital tunnel syndrome
The most common location of ulnar nerve impingement at the elbow is within the cubital tunnel, and is known as cubital tunnel syndrome. The tunnel is formed by the medial epicondyle of the humerus, the olecranon process of the ulna and the tendinous arch joining the humeral and ulnar heads of the flexor carpi ulnaris muscle. While most cases of injury are minor and resolve spontaneously with time, chronic compression or repetitive trauma may cause more persistent problems. Commonly cited scenarios include:

Sleeping with the arm folded behind neck, elbows bent. Pressing the elbows upon the arms of a chair while typing. Resting or bracing the elbow on the arm rest of a vehicle. Bench pressing. Intense exercising and strain involving the elbow.Compression of the ulnar nerve at the medial elbow may occasionally be caused by an epitrocheloanconeus muscle, an anatomical variant.