Superior Keratoconus

Superior keratoconus is a rare corneal disorder classified as a progressive noninflammatory ectasia, most commonly bilateral and asymmetric, with few occurrences of unilateral presentation. Controversy exists regarding the true presence of isolated superior keratoconus, but several cases have been confirmed and documented based on corneal topography measurements. Superior keratoconus characteristically presents as a superior corneal protrusion with superior central and paracentral corneal thinning and steepening, resulting in visual disturbances. Ocular manifestations vary and can remain subclinical for years with incremental advancement. Clinical onset and diagnosis typically occur between ages 10 and 40. Secondary causes of superior keratoconus commonly include mechanical disruption, such as in cases of blepharoptosis. As for the symptoms, patients usually experience worsening and fluctuating visual acuity with associated glare, halos, and photophobia.   Recent advancements in diagnostic imaging, such as corneal topography and tomography, have improved clinicians' ability to detect and monitor superior keratoconus. These imaging techniques allow for detailed corneal curvature, elevation, and thickness mapping, providing essential information for diagnosis and management. Studies have shown that superior keratoconus can be identified by distinctive topographic patterns, including superior steepening and inferior flattening, critical for differentiating it from other corneal ectasias. The management of superior keratoconus involves both nonsurgical and surgical approaches. Nonsurgical options include using rigid gas permeable (RGP) contact lenses or scleral lenses to improve vision by providing a more regular refractive surface. These lenses are particularly beneficial in cases where glasses are insufficient to correct vision due to irregular astigmatism. For progressive cases, corneal collagen cross-linking (CXL) is a well-established treatment aimed at halting the progression of ectasia. CXL works by strengthening the corneal stroma through the application of riboflavin (vitamin B2) and ultraviolet-A (UVA) light, which induces the formation of additional covalent bonds within the corneal collagen fibers. This procedure has been shown to stabilize the cornea and prevent further deterioration in many patients with superior keratoconus. Surgical interventions such as intracorneal ring segments (ICRS) or keratoplasty may be required in advanced stages of superior keratoconus, marked by corneal scarring or significant thinning. ICRS involves the insertion of semicircular plastic rings into the corneal stroma to flatten the cornea and improve vision. This procedure may be particularly useful in cases presenting with moderate ectasia and contact lens intolerance. Penetrating keratoplasty (PKP) or deep anterior lamellar keratoplasty (DALK) may be considered in severe cases where other treatments are ineffective. These procedures involve replacing the damaged corneal tissue with healthy donor tissue, offering the potential for significant visual improvement. However, PKP and DALK come with risks, such as graft rejection and the need for long-term immunosuppressive therapy. Genetic factors have also been implicated in the development of superior keratoconus. Studies have identified several genetic markers associated with keratoconus, suggesting a hereditary component to the disease. Understanding these genetic factors could pave the way for future therapies targeting the underlying causes of corneal ectasia. Moreover, research into the biomechanical properties of the cornea has provided insights into the pathophysiology of superior keratoconus. Advanced technologies like Brillouin microscopy and optical coherence elastography are being explored to assess corneal stiffness and viscoelasticity, which may help in early diagnosis and personalized treatment strategies. The prognosis of superior keratoconus is similar to that of general keratoconus. Patients typically experience progressive corneal thinning and worsening visual acuity. Severe stages of this disease may cause acute corneal hydrops and subsequent corneal stromal scarring. Current management strategies are aimed at stabilizing the cornea and improving visual acuity. Options include contact lens fitting, corneal cross-linking (CXL) or transplants, and intrastromal ring insertions. Superior keratoconus is a complex corneal disorder requiring a multifaceted approach for effective management. Early detection and intervention are crucial in preventing significant visual impairment. Ongoing research and technological advancements continue to enhance our understanding and treatment of this challenging condition, offering hope for better patient outcomes in the future.