3 & 9-O'Clock Staining/Peripheral Corneal Desiccation
- CLINICAL DESCRIPTION:
- Epithelial punctate staining of the peripheral cornea in regions adjacent to the edge of a rigid contact lens. As it pertains to the area of cornea that may not be adequately resurfaced with tears after a blink, its location is limited to the 2 to 4-o'clock and 8 to 10-o'clock regions of the peripheral cornea. Initially, and in most cases, the desiccation consists of isolated punctate stains. However, the staining can coalesce, with engorgement of the adjacent conjunctival blood vessels. In the most severe cases, peripheral corneal thinning occurs with ulceration, neovascularization, and scarring. A related condition, termed vascularized limbal keratitis (VLK) results when the desiccation is further compromised by peripheral seal off of the lens edge resulting in vascularization, staining, and an elevated opacified region. With peripheral corneal desiccation, the affected area stains with fluorescein and is easily detected using the cobalt blue filter over the illumination system and a yellow (Wratten or Tiffen) filter over the observation system of the biomicroscope.
- Patients with 3 & 9-o'clock staining may be asymptomatic, especially in the most common low grade form of this condition. However, some wearers will report redness and/or dryness. Severe cases may result in photophobia, lens awareness and reduced wearing time.
- Estimates range from 20-80% of rigid lens wearers with the incidence higher with extended wear.
- Contributory factors include tear film instability or deficiency, incomplete blinking, and "lid gap" factors such as excessive lens edge thickness, low lens positioning, excessive edge lift and insufficient lens movement. Insufficient edge lift or lens adherence may also induce staining. Poor RGP wettability due to acquired deposits and/or lens material surface characteristics (i.e., tear film dries out rapidly) is also a factor.
As 3 & 9-o'clock often occurs with an inferiorally decentered rigid lens, lens design changes to improve centration are important. This includes reducing the center thickness (i.e., an ultrathin design if possible) and use of a plus lenticular design for high minus power lenses and a minus lenticular for all plus and low minus power lenses. In addition, the edge should be inspected to ensure that it is smooth, free of defects, and is not excessively thick or blunt. If with fluorescein application, the edge clearance appears quite excessive, reducing edge clearance via a steeper peripheral curve radius, a narrower peripheral curve width, or both is indicated.
Likewise, the achievement of an alignment lens-to-cornea fitting relationship, if possible, is important. The use of an aspheric design or, with high corneal astigmatism, a bitoric or posterior toric design will assist in the achievement of such a fitting relationship. The selection of a RGP lens material with good wetting characteristics is important as well. Finally, frequent application of rewetting drops may be beneficial. Blinking exercises are indicated if the peripheral corneal desiccation is caused, in part, through partial or incomplete blinking.
In unresolved cases, lens wear should be decreased; if the patient wears the lenses on an extended wear basis, the wearing time should be reduced to a daily wear schedule. Punctal plug therapy may also be necessary. If the above management methods are not successful, refitting into a hydrogel lens is recommended.
- BEST REFERENCES:
- Hine H, Back A, Holden BA. Aetiology of arcuate epithelial lesions induced by hydrogels. Trans Br Cont Lens Assoc Conf 1987:48-50. (introduced the term SEAL's)
- Holden BA, Stephenson A, Stretton S, Sankaridurg P, O’Hare N, Jalbert I, Sweeney D. Superior Epithelial Arcuate Lesions with Soft Contact Lens Wear. Optom Vis Sci 2001; 78:9-12. (excellent review article)
- Malinovsky V, Pole J, Pence N, Howard D. Epithelial splits of the superior cornea in hydrogel contact lens patients. ICLC 1989;16:252-5. (retrospective study of clinical cases)
- OTHER REFERENCES:
- Tomlinson A. Contact lens-induced dry eye. In Tomlinson A: Complications of Contact Lens Wear. Mosby Year Book, St. Louis, MO 1992:195-218.
- Davis LJ, Lebow KA. Noninfectious corneal staining. In Silbert JA: Anterior Segment Complications of Contact Lens Wear (2nd ed.). Butterworth Heinemann, Boston, MA 2000:67-94.
- Schnider CM, Terry RL, Holden BA. Clinical correlates of peripheral corneal desiccation. Invest Ophthalmol Vis Sci 1988;29(Suppl):336.
- Henry VA, Bennett ES, Forrest JM. Clinical investigation of the Paraperm EW rigid gas permeable contact lens. Am J Optom & Physiol Opt 1987;64:313-320.
- Andrasko G. Peripheral corneal staining: incidence and time course. Contact Lens Spectrum 1990;7:59-62.
- Businger U, Treiber A, Flury C. the etiology and management of three and nine o'clock staining. Int Contact Lens Clin 1989;16(50):136-139.
- Holden T, Bahr K, Koers D, et al. The effect of secondary curve liftoff on peripheral corneal desiccation. Am J Optom Physiol Opt 1987;64:113.
- Schnider CM. Rigid gas permeable extended wear. Contact Lens Spectrum 1990;5(9):101-106.
- Bennett ES. Rigid gas-permeable lens problem solving. In Bennett ES, Henry VA: Clinical Manual of Contact Lenses (2nd ed.). Lippincott Williams & Wilkens, Philadelphia, PA 2000:181-210.
Cornea and Contact Lens Living Library
3 & 9-O'Clock Staining/Peripheral Corneal Desiccation
Terry Scheid, O.D. F.A.A.O., State University of New York College of Optometry
Edward Bennett, O.D., M.S., F.A.A.O., University of Missouri - St. Louis School of Optometry