Visual morbidity in thirty-four families with Schnyder crystalline corneal dystrophy (an American Ophthalmological Society thesis)

Abstract

Purpose: To assess the findings, visual morbidity, and surgical intervention in Schnyder crystalline corneal dystrophy (SCCD).

Methods: Retrospective case series of 115 affected individuals from 34 SCCD families identified since 1989. Age, uncorrected visual acuity, best-corrected visual acuity (BCVA), corneal findings, and ocular surgery were recorded. Prospective phone, e-mail, or written contact provided updated information. Patients were divided into 3 age categories for statistical analysis: less than 26 years of age, 26 to 39 years of age, and 40 years of age and older.

Results: Mean age on initial examination was 38.8 +/- 20.4 (range, 2-81) with follow-up of 55 of 79 (70%) of American patients. While there were no statistical significant correlations between logMAR visual acuity and age (logMAR BCVA =.033 + .002 x age; R =.21), the linear regression showed the trend of worse visual acuity with age. BCVA at > or =40 years was decreased compared to <40 (P < .0001), although mean BCVA was > 20/30 in both groups. Twenty-nine of 115 patients had corneal surgery with 5 phototherapeutic keratectomy (3 patients), and 39 penetrating keratoplasty (PKP) (27 patients). PKP was reported in 20 of 37 (54%) patients > or =50 years and 10 of 13 (77%) of patients > or =70. BCVA 1 year prior to PKP in 15 eyes (9 patients) ranged from 20/25 to 20/400 including 7 eyes with other ocular pathology. BCVA in the remaining 8 eyes was 20/25 to 20/70 with 3 of these 4 patients reporting preoperative glare. Chart and phone survey suggested increasing difficulty with photopic vision with aging.

Conclusion: Although excellent scotopic vision continues until middle age in SCCD, most patients had PKP by the 7th decade. SCCD causes progressive corneal opacification, which may result in glare and disproportionate loss of photopic vision.

FIGURE 1

Corneal diagram of location of corneal changes in Schnyder crystalline corneal dystrophy. Initial changes are noted in central cornea (A) with occurrence of corneal crystals and/or central haze followed by formation of arcus lipoides (C) and finally midperipheral stromal haze (B). Reprinted from Weiss JS, et al.

FIGURE 2

Map of Finland with arrows pointing to towns with patients identified to have Schnyder crystalline corneal dystrophy.

FIGURE 3

Pedigree A. Patients who have had penetrating keratoplasty are indicated. Individual patients are identified by a roman numeral representing the family generation and an arabic number. The unique patient identifier number and pedigree name is used to identify the patient in the text, photographs, and tables.

FIGURE 4

Pedigree B. Key for this figure is listed in Figure 3. Individual patients are identified by a roman numeral representing the family generation and an arabic number. The unique patient identifier number and pedigree name is used to identify the patient in the text, photographs, and tables. Patients who have had penetrating keratoplasty are indicated.

FIGURE 5

Pedigree J. Key for this figure is listed in Figure 3. Individual patients are identified by a roman numeral representing the family generation and an arabic number. The unique patient identifier number and pedigree name is used to identify the patient in the text, photographs and tables. Patients who have had penetrating keratoplasty or phototherapeutic keratectomy are indicated.

FIGURE 6

Visual acuity flow chart of patients with Schnyder crystalline corneal dystrophy.

FIGURE 7

Regression analysis of best-corrected visual acuity (BCVA) with age in years (yrs) in Schnyder crystalline corneal dystrophy patients who have no other ocular pathology. Y-axis represents logMAR visual acuity and x-axis represents age y = −.033 + .002x; R² = .046.

FIGURE 8

The corneas of a 28-year-old female in family G, with UCVA 20/15 OD and 20/20 OS, which demonstrate an almost complete circle of crystalline deposition that appears to be bilaterally symmetric. OD and OS appear to have a mirror image crystalline deposit. Left, External photograph of OD. Middle, External photograph of OS. Right, Slit-lamp photograph demonstrating subepithelial crystalline deposits.

FIGURE 9

External photograph of the cornea of a 14-year-old male, III 2, in family B, with UCVA of 20/20 and partial arc deposition of subepithelial crystals. A symmetrical mirror image crystalline deposit was seen in the other eye.

FIGURE 10

External photograph of the cornea of a 38-year-old male, II 7, in family A, with central haze, central ring of crystals, midperipheral clouding, and arcus lipoides. BCVA was 20/25.

FIGURE 11

External photograph of the cornea of a 37-year-old male, III 5, in family B, with central plaque of subepithelial crystals in visual axis and BCVA of 20/50. Six months later, PRK/PTK was performed with improvement of UCVA to 20/25.

FIGURE 12

Slit-lamp photograph of the cornea of a 23-year-old female, III 9, in family B, with BCVA 20/20 and central corneal ring opacity slightly inferiorly displaced in the visual axis. No subepithelial crystals were present.

FIGURE 13

External photograph of the cornea of a 40-year-old male, II 5, in family A, with BCVA 20/25 and central disc-shaped stromal opacity and arcus lipoides. The central opacity is panstromal and is slightly inferiorly displaced in the visual axis. No subepithelial crystals were present.

FIGURE 14

Slit-lamp photograph of the cornea of a 47-year-old male, II 1, in family B, with BCVA 20/30. Retroillumination reveals that the central opacity is more lucent in its middle and the opacity appears to be tessellated. Midperipheral haze and prominent arcus lipoides are also noted.

FIGURE 15

External photograph of the cornea OD of a 63-year-old female, I 1, in family B, with BCVA 20/70 with subepithelial crystals, diffuse corneal haze, and arcus lipoides. OD underwent PKP, CE and IOL surgery within the year. Figure 28 demonstrates change in appearance of eyes after PKP.

FIGURE 16

External photograph of the cornea of a 72-year-old female in family C, patient 2, with BCVA 20/40 with dense central opacity, midperipheral haze, and arcus lipoides that underwent PKP, cataract extraction, and IOL within the year.

FIGURE 17

External photograph of the cornea of a 74-year-old male, I 1, in family J, with BCVA 20/25 and diffuse corneal opacification and arcus lipoides.

FIGURE 18

Left, External photograph of the cornea of a 39-year-old female, II 2, in family B, with BCVA of 20/20 with diffuse corneal opacification that makes the entire cornea appear hazy. Patient had PKP 18 years later. Right, With use of retroillumination, a denser central opacity is apparent.

FIGURE 19

External photograph of the cornea of a 49-year-old male, II 5, from family B, with BCVA of 20/30 and central and midperipheral corneal haze, central crystals, and arcus lipoides. Arcus was prominent enough to see without the aid of a slit lamp. Patient subsequently had PKP for complaints of decreased vision and glare.

FIGURE 20

Flow chart of Schnyder crystalline corneal dystrophy patient survey and phone call follow-up.

FIGURE 21

Flow chart of change in visual acuity in Schnyder crystalline corneal dystrophy (SCCD) patient with at least 7 years of follow-up.

FIGURE 22

Left, External photograph of the cornea of a 33-year-old male, patient 1, in family Q, with BCVA of 20/25, central subepithelial crystals, and arcus lipoides. (Photograph has been lightened to increase contrast and allow best visualization of crystal deposition). Right, 8 years later, patient is 43 years old with BCVA of 20/50 with increased central crystalline opacity, midperipheral haze, and arcus lipoides. PTK, which was subsequently performed within the year, did not increase BCVA and patient subsequently underwent PKP.

FIGURE 23

Serial external photos of the eyes of a 39-year-old woman, patient 1, in family C, with amblyopia OS and BCVA of 20/30 OD and 20/400 OS, demonstrating central corneal disc opacity, few inferior central subepithelial crystals, midperipheral haze, and arcus lipoides. Increasing density of corneal haze is demonstrated over 17-year follow-up. BCVA at age 56 is 20/50 OD and 20/400 OS and PKP was planned. External photos of OD at age 39 (top left), OS at age 39 (bottom left), OD at age 52 (top middle), OS at age 52 (bottom middle), OD at age 56 (top right), and OS at age 56 (bottom right).

FIGURE 24

Schnyder crystalline corneal dystrophy penetrating keratoplasty flow chart for age at first PKP.

FIGURE 25

Age vs corneal surgery prevalence in Schnyder crystalline corneal dystrophy.(SCCD). Left y-axis represents number of patients, right y-axis represent percentage of patients. X-axis represents decade of age in years (yr) on most recent contact. Blue columns represent total number of patients in each decade of age. Red columns represent number of patients reporting prior corneal surgery on the most recent contact. Red line indicates percentage of patients in each decade of age with history of corneal surgery.

FIGURE 26

Flow chart of cholesterol measurements in patients undergoing penetrating keratoplasty or phototherapeutic keratectomy.

FIGURE 27

Diagram of corneal changes with age. Reprinted from Weiss JS.

FIGURE 28

External photograph of eyes of 68-year-old female, I 1, from family B, with clear cornea after PKP OD and “cloudy” cornea OS from SCCD. Bilateral arcus lipoides is apparent. Figure 15 demonstrates magnified view of corneal changes OD before PKP.

FIGURE 29

External photograph of cornea of an 80-year-old male, I 2, in family J, with BCVA of 20/30 OD and diffuse corneal haze with tessellations reminiscent of central cloudy dystrophy of Francois or posterior crocodile shagreen. OS had undergone PKP 3 years before.

FIGURE 30

53-year-old male, II 1, in family J (son of patient I 1 in Figure 17) with BCVA 20/25 OU, central corneal haze and crystals, midperipheral haze, and arcus lipoides.

FIGURE 31

Light microscopy of the SCCD cornea with reddish hue from staining of the lipid deposits with oil red O (oil red O, ×40).

FIGURE 32

Fluorescence noted from stromal deposition of filipin stained lipid (filipin, ×40).

FIGURE 33

Left, Basal epithelial cells, corneal stroma, and few endothelial cells demonstrated dissolved lipid and cholesterol (toluidine blue, ×250). Right, Electron microscopy demonstrating lipid deposits in posterior stroma and pre-Descemet’s area (×9900).